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Sample records for unconfined compressive strength

  1. Influence of variables on the consolidation and unconfined compressive strength of crushed salt: Technical report

    International Nuclear Information System (INIS)

    Eight hydrostatic compression creep tests were performed on crushed salt specimens fabricated from Avery Island dome salt. Following the creep test, each specimen was tested in unconfined compression. The experiments were performed to assess the influence of the following four variables on the consolidation and unconfined strength of crushed salt: grain size distribution, temperature, time, and moisture content. The experiment design comprised a half-fraction factorial matrix at two levels. The levels of each variable investigated were grain size distribution, uniform-graded and well-graded (coefficient of uniformity of 1 and 8); temperature 250C and 1000C; time, 3.5 x 103s and 950 x 103s (approximately 60 minutes and 11 days, respectively); and moisture content, dry and wet (85% relative humidity for 24 hours). The hydrostatic creep stress was 10 MPa. The unconfined compression tests were performed at an axial strain rate of 1 x 10-5s-1. Results show that the variables time and moisture content have the greatest influence on creep consolidation, while grain size distribution and, to a somewhat lesser degree, temperature have the greatest influence on total consolidation. Time and moisture content and the confounded two-factor interactions between either grain size distribution and time or temperature and moisture content have the greatest influence on unconfined strength. 7 refs., 7 figs., 11 tabs

  2. Effect Of Coir Fibres On The Compaction And Unconfined Compressive Strength Of Bentonite-Lime-Gypsum Mixture

    Directory of Open Access Journals (Sweden)

    Tilak B. Vidya

    2015-06-01

    Full Text Available This paper presents the effect of coir fibres on the compaction and unconfined compressive strength of a bentonite-lime-gypsum mixture. The coir fiber content varied from 0.5 to 2 %. The results indicated that the dry unit weight and the optimum moisture content of a bentonite – lime mix increased with the addition of gypsum. The unconfined compressive strength of the bentonite increased with the increase in the lime content up to 8 %. Beyond 8 %, the unconfined compressive strength decreased. The dry unit weight of the reference mix decreased, and the optimum moisture content increased with the addition of coir fibre. The unconfined compressive strength of the bentonite + 8 % lime mix increased up to 4 % with the gypsum. Beyond 4 %, the unconfined compressive strength decreased. The unconfined compressive strength of the reference mix increased with the addition of coir fibre up to a fibre content of 1.5 %. The unconfined compressive strength of the reference mix-coir fibre composite was less in comparison to the reference mix. The unconfined compressive strength of the bentonite increased with the addition of lime and gypsum and with the increase in the curing period. The improvement in the post-peak region was better for the reference mix with reinforced coir fibres as compared to the unreinforced reference mix. The improved post-peak behaviour of the bentonite-lime-gypsum-coir fibre mixture could boost the construction of temporary roads on such problematic soils. Further, its use will also provide an environmental motivation for providing a means of consuming large quantities of coir fibres.

  3. Influence of mica on unconfined compressive strength of a cement-treated weathered granite gravel

    Scientific Electronic Library Online (English)

    M R, Mshali; A T, Visser.

    Full Text Available The road construction industry faces a shortage of naturally occurring gravel materials that meet the requirements for base or even at times sub-base quality. This situation is exacerbated in some cases by the occurrence of mica in soils. This is reported to significantly affect the engineering prop [...] erties of materials, including plasticity index and compacted density. The objective of this paper is to investigate the influence of mica on the unconfined compressive strength (UCS) and volumetric changes of a cement-treated gravel material. Free mica (muscovite) was added in predetermined percentages by mass to neat gravel (G5) and specimens subjected to a series of standard laboratory tests. The results show that UCS of greater than 3 MPa is achievable by stabilising less than 5% mica content gravel material with at least 4% cement. Mica content beyond 10% results in very low UCS, even for cement content greater than 6%.

  4. Unconfined Compressive Strength of Fly Ash Mixed With Lime Precipitated Waste Sludge and Cement

    Directory of Open Access Journals (Sweden)

    Dr. Malik Shoeb Ahmad

    2014-10-01

    Full Text Available For an effective disposal of fly ash, avoiding environmental pollution, it is necessary to utilize it on a continuous basis for some beneficial purposes. The present study investigated the feasibility and effectiveness of the fly ash along with lime precipitated waste sludge and cement. The Unconfined Compressive Strength (UCS tests were carried out on the specimens comprising of fly ash (FA, (5 to 35% lime precipitated electroplating waste sludge (S and (2-20% cement at 7 and 28 days of curing periods. The results of UCS tests indicated that the strength of fly ash increases substantially on addition of lime precipitated sludge and cement. It has been observed that compressive strengths of cement stabilized fly ash were smaller than the cement-sludge stabilized mix. It has also been observed that the strength was increasing upto 20% sludge addition to fly ash-cement mix, however, the strength started decreasing on further addition of sludge beyond 20% to the fly ash-cement combination. The most effective percentage of fly ash-cement-sludge was found as 72%FA+20%S+8%C. The UCS of this mix was found as 18 and 25 MPa at 7 and 28 days of curing respectively. This is substantially higher than the UCS of plain fly ash (1.0 and 2.5 MPa at the same curing periods respectively. The X-ray analyses of some selected samples using EDX technique were also carried to study the elemental analyses of the various mixes. The EDX data showed that the experimental results obtain by UCS tests were in conformity with the chemical findings of EDX

  5. Development of K-Basin High-Strength Homogeneous Sludge Simulants and Correlations Between Unconfined Compressive Strength and Shear Strength

    Energy Technology Data Exchange (ETDEWEB)

    Onishi, Yasuo; Baer, Ellen BK; Chun, Jaehun; Yokuda, Satoru T.; Schmidt, Andrew J.; Sande, Susan; Buchmiller, William C.

    2011-02-20

    K-Basin sludge will be stored in the Sludge Transport and Storage Containers (STSCs) at an interim storage location on Central Plateau before being treated and packaged for disposal. During the storage period, sludge in the STSCs may consolidate/agglomerate, potentially resulting in high-shear-strength material. The Sludge Treatment Project (STP) plans to use water jets to retrieve K-Basin sludge after the interim storage. STP has identified shear strength to be a key parameter that should be bounded to verify the operability and performance of sludge retrieval systems. Determining the range of sludge shear strength is important to gain high confidence that a water-jet retrieval system can mobilize stored K-Basin sludge from the STSCs. The shear strength measurements will provide a basis for bounding sludge properties for mobilization and erosion. Thus, it is also important to develop potential simulants to investigate these phenomena. Long-term sludge storage tests conducted by Pacific Northwest National Laboratory (PNNL) show that high-uranium-content K-Basin sludge can self-cement and form a strong sludge with a bulk shear strength of up to 65 kPa. Some of this sludge has 'paste' and 'chunks' with shear strengths of approximately 3-5 kPa and 380-770 kPa, respectively. High-uranium-content sludge samples subjected to hydrothermal testing (e.g., 185 C, 10 hours) have been observed to form agglomerates with a shear strength up to 170 kPa. These high values were estimated by measured unconfined compressive strength (UCS) obtained with a pocket penetrometer. Due to its ease of use, it is anticipated that a pocket penetrometer will be used to acquire additional shear strength data from archived K-Basin sludge samples stored at the PNNL Radiochemical Processing Laboratory (RPL) hot cells. It is uncertain whether the pocket penetrometer provides accurate shear strength measurements of the material. To assess the bounding material strength and potential for erosion, it is important to compare the measured shear strength to penetrometer measurements and to develop a correlation (or correlations) between UCS measured by a pocket penetrometer and direct shear strength measurements for various homogeneous and heterogeneous simulants. This study developed 11 homogeneous simulants, whose shear strengths vary from 4 to 170 kPa. With these simulants, we developed correlations between UCS measured by a Geotest E-280 pocket penetrometer and shear strength values measured by a Geonor H-60 hand-held vane tester and a more sophisticated bench-top unit, the Haake M5 rheometer. This was achieved with side-by-side measurements of the shear strength and UCS of the homogeneous simulants. The homogeneous simulants developed under this study consist of kaolin clay, plaster of Paris, and amorphous alumina CP-5 with water. The simulants also include modeling clay. The shear strength of most of these simulants is sensitive to various factors, including the simulant size, the intensity of mixing, and the curing time, even with given concentrations of simulant components. Table S.1 summarizes these 11 simulants and their shear strengths.

  6. Development of K-Basin High-Strength Homogeneous Sludge Simulants and Correlations Between Unconfined Compressive Strength and Shear Strength

    International Nuclear Information System (INIS)

    K-Basin sludge will be stored in the Sludge Transport and Storage Containers (STSCs) at an interim storage location on Central Plateau before being treated and packaged for disposal. During the storage period, sludge in the STSCs may consolidate/agglomerate, potentially resulting in high-shear-strength material. The Sludge Treatment Project (STP) plans to use water jets to retrieve K-Basin sludge after the interim storage. STP has identified shear strength to be a key parameter that should be bounded to verify the operability and performance of sludge retrieval systems. Determining the range of sludge shear strength is important to gain high confidence that a water-jet retrieval system can mobilize stored K-Basin sludge from the STSCs. The shear strength measurements will provide a basis for bounding sludge properties for mobilization and erosion. Thus, it is also important to develop potential simulants to investigate these phenomena. Long-term sludge storage tests conducted by Pacific Northwest National Laboratory (PNNL) show that high-uranium-content K-Basin sludge can self-cement and form a strong sludge with a bulk shear strength of up to 65 kPa. Some of this sludge has 'paste' and 'chunks' with shear strengths of approximately 3-5 kPa and 380-770 kPa, respectively. High-uranium-content sludge samples subjected to hydrothermal testing (e.g., 185 C, 10 hours) have been observed to form agglomerates with a shear strength up to 170 kPa. These high values were estimated by measured unconfined compressive strength (UCS) obtained with a pocket penetrometer. Due to its ease of use, it is anticipated that a pocket penetrometer will be used to acquire additional shear strength data from archived K-Basin sludge samples stored at the PNNL Radiochemical Processing Laboratory (RPL) hot cells. It is uncertain whether the pocket penetrometer provides accurate shear strength measurements of the material. To assess the bounding material strength and potential for erosion, it is important to compare the measured shear strength to penetrometer measurements and to develop a correlation (or correlations) between UCS measured by a pocket penetrometer and direct shear strength measurements for various homogeneous and heterogeneous simulants. This study developed 11 homogeneous simulants, whose shear strengths vary from 4 to 170 kPa. With these simulants, we developed correlations between UCS measured by a Geotest E-280 pocket penetrometer and shear strength values measured by a Geonor H-60 hand-held vane tester and a more sophisticated bench-top unit, the Haake M5 rheometer. This was achieved with side-by-side measurements of the shear strength and UCS of the homogeneous simulants. The homogeneous simulants developed under this study consist of kaolin clay, plaster of Paris, and amorphous alumina CP-5 with water. The simulants also include modeling clay. The shear strength of most of these simulants is sensitive to various factors, including the simulant size, the intensity of mixing, and the curing time, even with given concentrations of simulant components. Table S.1 summarizes these 11 simulants and their shear strengths.

  7. Development of experimental correlations between indentation parameters and unconfined compressive strength (UCS) values in shale samples

    International Nuclear Information System (INIS)

    Confined Compressive Strength (UCS) is one of the rock mechanical properties that is important take into account during drilling operations in order to avoid wellbore instability. During drilling operations, UCS variability influences wellbore stability more than other factors such as azimuth, slope, exposure time, and mud weight (Jaramillo, 2004). In last year, the indentation technique has been demonstrated to be an appropriate method for determining rock strength in real time during oil well drilling. This technique implements correlation that allow UCS evaluation from indentation parameters such as Indentation Module (IM) and Critical Transition Force (CTF), that can be measured on small rock fragments obtained during drilling. Shale formations in well drilling have demonstrated to be a hindrance since they represent the most important problem in reservoir stability (Abass, H., A. et al. 2006). Therefore, the main objective of this article is to find experimental correlations that allow the modeling of rock strength by applying the indentation technique to reservoir plug. The importance of this technique is the possibility to get rock strength properties in real time during drilling operations, although, those reservoir sections which do not have neither direct neither UCS records nor indirect measurements. Eight Unconfined Compression Tests (UCS) on rock cylinders (plugs) extracted from the Paja Formation upwelling were conducted in order to develop the corresponding experimental correlations. Two hundred indentation tests were also simultaneously conducted on shale fragments extracted from each plug surroundings in order to simulate the caving obtained from reservoir drilled. Results of both tests were correlated using the Minimum Square technique, seeking the best correlation that shall represent result behavior, thus obtaining two 2nd-degree polynomial correlations. Correlation coefficients of 0.6513 were determined for the (IM) - (UCS) correlation and 0.8111 for the (CTF) - (UCS) correlation. This demonstrates that the highest correlation between indentation parameters and (UCS) is obtained with the Critical Transition Force (CTF)

  8. Effect of Industrial By-Products on Unconfined Compressive Strength of Solidified Organic Marine Clayey Soils

    Directory of Open Access Journals (Sweden)

    Chan-Gi Park

    2015-08-01

    Full Text Available The use of industrial by-products as admixture to ASTM Type I cement (ordinary Portland cement (OPC was investigated with the objective of improving the solidification of organic marine clayey soils. The industrial by-products considered in this paper were oyster-shell powder (OSP, steelmaking slag dust (SMS and fuel-gas-desulfurized (FGD gypsum. The industrial by-products were added to OPC at a ratio of 5% based on dry weight to produce a mixture used to solidify organic marine clayey soils. The dosage ratios of mixtures to organic marine clayey soils were 5, 10 and 15% on a dry weight basis. Unconfined compressive strength (UCS test after 28 days revealed that the highest strength was obtained with the OPC + SMS 15% mixing ratio. The UCS of specimens treated with this mixture was >500 kPa, compared with 300 kPa for specimens treated with a 15% OPC + OSP mixture and 200 kPa when 15% of OPC was used alone. These results were attributed to the more active hydration and pozzolanic reaction of the OPC + SMS mixture. This hypothesis was verified through X-ray diffraction (XRD and scanning electron microscopy (SEM analyses, and was confirmed by variations in the calcium carbonate (CaCO3 content of the materials during curing.

  9. Rock drillability prediction from in situ determined unconfined compressive strength of rock

    Scientific Electronic Library Online (English)

    V.C, Kelessidis.

    2011-06-01

    Full Text Available SYNOPSIS The interaction between rock and drill bit during drilling has been modeled for many years, but a complete understanding of the phenomena occurring has yet to materialize. Successful models will allow the prediction of rate of penetration in a given environment and optimal selection of dril [...] l bit and drilling parameters, thus minimizing exploration costs. In most rock-drilling models the value of the unconfined compressive strength of the rock (UCS) is used in the predictive equations, within the concept of specific energy, and the value of UCS is the percentage of the value of the stress applied on the drilling bit in order for the bit to advance. While the exact percentage depends on the model used and it is not known with certainty, good knowledge of UCS is never-theless required before any decent prediction can be made on rate of penetration. Determination of UCS, normally done via destructive testing, requires not only the availability of sound rock core samples but also expensive testing and significant time for the test, which frequently are not available for routine drillability predictions. Hence, a multitude of methods and techniques has been proposed for estimating UCS from various indirect and/or non-destructive measurements, or combination of measurements with neural networks, such as point load index, block punch index, unit weight, and apparent porosity, water absorption by weight, sonic velocity, and Schmidt hardness. The many proposed approaches are critically reviewed and the results are compared, and what becomes apparent is that after many years, not only in mining but also in oil-well drilling, accurate indirect determination of UCS is still an elusive goal. An equation to predict UCS from sonic velocity data is suggested based on several data sets reported in the literature. Use of the specific energy equation with UCS or sonic data and utilization of drilling data allows an estimation of the efficiency of energy transfer from the bit to the rock and of the friction coefficient. Analysis of data reported in the literature, both from laboratory and field studies, has shown that this approach is sound and enables the determination of energy transfer efficiencies and friction coefficients, which for the cases studied range between 15 and 30% and 0.15 and 0.30 respectively. Thus, the suggested data analysis approach allows drillers to focus on inefficiencies and optimize drilling practices in future campaigns.

  10. Behavior of Stabilized Peat Soils in Unconfined Compression Tests

    Directory of Open Access Journals (Sweden)

    Wong L. Sing

    2008-01-01

    Full Text Available Problem statement: Deep stabilized peat columns were known to be economical at forming foundations to support highway embankments constructed on deep peat land. However, failure in the formation of the columns with adequate strength was often attributed to unsuitable type and insufficient dosage of binder added to the soil. Organic matter in peat was known to impede the cementing process in the soil, thus retarding the early strength gain of stabilized peat. Approach: To evaluate the strength characteristics of stabilized peat, laboratory investigation on early strength gain of the stabilized soil was conducted to formulate a suitable and economical mix design that could be effectively used for the soil stabilization. To achieve such purpose, the study examined the effect of binder, sodium chloride as cement accelerator and siliceous sand as filler on the unconfined compressive strength of stabilized peat soils after 7 days of curing. Binders used to stabilize the peat were Ordinary Portland cement, ground granulated blast furnace slag, sodium bentonite, kaolinite, lime and bentonite. All the stabilized peat specimens were tested using unconfined compression apparatus. Results: The test results revealed that the stabilized peat specimen (80% OPC: 10% GGBS: 10% SB with addition of 4% sodium chloride by weight of binder and 50% well graded siliceous sand by volume of wet peat at 300 kg m-3 binder dosage yielded the highest unconfined compressive strength of 196 kPa. Such finding implied that the higher the dosage of siliceous sand in stabilized peat, the more solid particles were available for the binder to unite and form a load sustainable stabilized peat. Conclusions/Recommendations: It could be summarized that as the rate of hydration process of stabilized peat was accelerated by inclusion of sodium chloride, the solid particles contributed to the hardening of stabilized peat by providing the cementation bonds to form between contact points of the particles.

  11. DEVELOPMENT OF EXPERIMENTAL CORRELATIONS BETWEEN INDENTATION PARAMETERS AND UNCONFINED COMPRESSIVE STRENGTH (UCS VALUES IN SHALE SAMPLES DESARROLO DE CORRELACIONES EXPERIMENTALES ENTRE PÁRAMETROS DE IDENTACIÓN Y LA RESISTENCIA COMPRENSIVA UNIAXIAL (UCS PARA MUESTRAS DE SHALE

    Directory of Open Access Journals (Sweden)

    Ricardo-Andrés García

    2008-12-01

    Full Text Available Unconfined Compressive Strength (UCS is one of the rock mechanical properties that is important take into account during drilling operations in order to avoid wellbore instability. During drilling operations, UCS variability influences wellbore stability more than other factors such as azimuth, slope, exposure time, and mud weight (Jaramillo, 2004. In last years, the indentation technique has been demonstrated to be an appropriate method for determining rock strength in real time during oil well drilling. This technique implements correlation that allow UCS evaluation from indentation parameters such as Indentation Module (IM and Critical Transition Force (CTF, that can be measured on small rock fragments obtained during drilling. Shale formations in well drilling have demonstrated to be a hindrance since they represent the most important problem in reservoir stability (Abass, H., A. et al. 2006. Therefore, the main objective of this article is to find experimental correlations that allow the modeling of rock strength by applying the indentation technique to reservoir plug. The importance of this technique is the possibility to get rock strength properties in real time during drilling operations, although, those reservoir sections which do not have neither direct UCS records nor indirect measurements. Eight Unconfined Compression Tests (UCS on rock cylinders (plugs extracted from the Paja formation upwelling were conducted in order to develop the corresponding experimental correlations. Two hundred indentation tests were also simultaneously conducted on shale fragments extracted from each plug surroundings in order to simulate the cavings obtained from reservoir drilled. Results of both tests were correlated using the Minimum Square technique, seeking the best correlation that shall represent result behavior, thus obtaining two 2nd-degree polynomial correlations. Correlation coefficients of 0,6513 were determined for the (IM - (UCS correlation and 0,8111 for the (CTF - (UCS correlation. This demonstrates that the highest correlation between indentation parameters and (UCS is obtained with the Critical Transition Force (CTF.La Resistencia Compresiva Uniaxial (UCS, es una de las propiedades mecánicas de las rocas que se debe tener en cuenta durante las operaciones de perforación para evitar la inestabilidad de pozos (Abass H., A. et al. 2006. Durante las operaciones de perforación el UCS de las formaciones es la variable de más alta influencia por encima de factores como el azimut, la inclinación, el tiempo de exposición e incluso el peso del lodo de perforación (Jaramillo, 2004. La técnica de Indentación ha demostrado en los últimos años ser adecuada para ayudar a determinar la resistencia de las rocas en tiempo real durante la perforación de pozos, mediante la implementación de correlaciones que permitan evaluar el UCS a partir de los parámetros de Indentación conocidos como Módulo de Indentación (IM y Fuerza Crítica de Transición (CTF, medidas en pequeños fragmentos de roca obtenidos de la perforación de pozos. La resistencia de los shales ha demostrado ser muy problemática durante la perforación. Por este motivo el principal objetivo de este trabajo es encontrar correlaciones experimentales que permitan modelar la resistencia de la roca a través de la aplicación de la técnica de indentacion a muestras de roca. Lo interesante de esta técnica es la posibilidad de obtener propiedades de resistencia en tiempo real durante la perforación, incluyendo esas secciones del reservorio en las que no existen registros directos UCS ni mediciones indirectas. Con el fin de desarrollar las correlaciones experimentales se realizaron ocho pruebas de Compresión Uniaxial (no confinada sobre cilindros de roca (plugs extraídos de muestras de afloramiento de la formación Paja. A la vez re realizaron 200 pruebas de Indentación sobre fragmentos de shale extraídos de los alrededores de cada plug simulando los ripios que se obtienen de la perforación de pozos. Los resultados de ambas pruebas f

  12. DEVELOPMENT OF EXPERIMENTAL CORRELATIONS BETWEEN INDENTATION PARAMETERS AND UNCONFINED COMPRESSIVE STRENGTH (UCS) VALUES IN SHALE SAMPLES / DESARROLO DE CORRELACIONES EXPERIMENTALES ENTRE PÁRAMETROS DE IDENTACIÓN Y LA RESISTENCIA COMPRENSIVA UNIAXIAL (UCS) PARA MUESTRAS DE SHALE

    Scientific Electronic Library Online (English)

    Ricardo-Andrés, García; Néstor-Fernando, Saavedra; Zuly, Calderón-Carrillo; Darwin, Mateus.

    2008-12-01

    Full Text Available La Resistencia Compresiva Uniaxial (UCS), es una de las propiedades mecánicas de las rocas que se debe tener en cuenta durante las operaciones de perforación para evitar la inestabilidad de pozos (Abass H., A. et al. 2006). Durante las operaciones de perforación el UCS de las formaciones es la varia [...] ble de más alta influencia por encima de factores como el azimut, la inclinación, el tiempo de exposición e incluso el peso del lodo de perforación (Jaramillo, 2004). La técnica de Indentación ha demostrado en los últimos años ser adecuada para ayudar a determinar la resistencia de las rocas en tiempo real durante la perforación de pozos, mediante la implementación de correlaciones que permitan evaluar el UCS a partir de los parámetros de Indentación conocidos como Módulo de Indentación (IM) y Fuerza Crítica de Transición (CTF), medidas en pequeños fragmentos de roca obtenidos de la perforación de pozos. La resistencia de los shales ha demostrado ser muy problemática durante la perforación. Por este motivo el principal objetivo de este trabajo es encontrar correlaciones experimentales que permitan modelar la resistencia de la roca a través de la aplicación de la técnica de indentacion a muestras de roca. Lo interesante de esta técnica es la posibilidad de obtener propiedades de resistencia en tiempo real durante la perforación, incluyendo esas secciones del reservorio en las que no existen registros directos UCS ni mediciones indirectas. Con el fin de desarrollar las correlaciones experimentales se realizaron ocho pruebas de Compresión Uniaxial (no confinada) sobre cilindros de roca (plugs) extraídos de muestras de afloramiento de la formación Paja. A la vez re realizaron 200 pruebas de Indentación sobre fragmentos de shale extraídos de los alrededores de cada plug simulando los ripios que se obtienen de la perforación de pozos. Los resultados de ambas pruebas fueron correlacionados por medio de la técnica de mínimos cuadrados y se buscó la mejor correlación que representara el comportamiento de los resultados, permitiendo así obtener dos correlaciones polinomiales de segundo grado. Se determinaron coeficientes de correlación de 0,6513 para la correlación IM-UCS y 0,8111 para la correlación CTF-UCS, mostrando así que la mayor correlacionalidad entre parámetros de indentación y el UCS se da con el parámetro de Indentación conocido como Fuerza Critica de Transición (CTF). Abstract in english Unconfined Compressive Strength (UCS) is one of the rock mechanical properties that is important take into account during drilling operations in order to avoid wellbore instability. During drilling operations, UCS variability influences wellbore stability more than other factors such as azimuth, slo [...] pe, exposure time, and mud weight (Jaramillo, 2004). In last years, the indentation technique has been demonstrated to be an appropriate method for determining rock strength in real time during oil well drilling. This technique implements correlation that allow UCS evaluation from indentation parameters such as Indentation Module (IM) and Critical Transition Force (CTF), that can be measured on small rock fragments obtained during drilling. Shale formations in well drilling have demonstrated to be a hindrance since they represent the most important problem in reservoir stability (Abass, H., A. et al. 2006). Therefore, the main objective of this article is to find experimental correlations that allow the modeling of rock strength by applying the indentation technique to reservoir plug. The importance of this technique is the possibility to get rock strength properties in real time during drilling operations, although, those reservoir sections which do not have neither direct UCS records nor indirect measurements. Eight Unconfined Compression Tests (UCS) on rock cylinders (plugs) extracted from the Paja formation upwelling were conducted in order to develop the corresponding experimental correlations. Two hundred indentation tests were also simultaneously conducted on

  13. Determination of Friction Coefficient in Unconfined Compression of Brain Tissue

    CERN Document Server

    Rashid, Badar; Gilchrist, Michael; 10.1016/j.jmbbm.2012.05.001

    2013-01-01

    Unconfined compression tests are more convenient to perform on cylindrical samples of brain tissue than tensile tests in order to estimate mechanical properties of the brain tissue because they allow for homogeneous deformations. The reliability of these tests depends significantly on the amount of friction generated at the specimen/platen interface. Thus, there is a crucial need to find an approximate value of the friction coefficient in order to predict a possible overestimation of stresses during unconfined compression tests. In this study, a combined experimental-computational approach was adopted to estimate the dynamic friction coefficient mu of porcine brain matter against metal platens in compressive tests. Cylindrical samples of porcine brain tissue were tested up to 30% strain at variable strain rates, both under bonded and lubricated conditions in the same controlled environment. It was established that mu was equal to 0.09 +/- 0.03, 0.18 +/- 0.04, 0.18 +/- 0.04 and 0.20 +/- 0.02 at strain rates of...

  14. Behavior of Stabilized Peat Soils in Unconfined Compression Tests

    OpenAIRE

    Wong L. Sing; Roslan Hashim; Faisal H. Ali

    2008-01-01

    Problem statement: Deep stabilized peat columns were known to be economical at forming foundations to support highway embankments constructed on deep peat land. However, failure in the formation of the columns with adequate strength was often attributed to unsuitable type and insufficient dosage of binder added to the soil. Organic matter in peat was known to impede the cementing process in the soil, thus retarding the early strength gain of stabilized peat. Approach: To evaluate the strength...

  15. Unconfined compression experiments on Topopah Spring Member tuff at 22 degrees C and a strain rate of 10-9 s-1: Data report

    International Nuclear Information System (INIS)

    Experiment results are presented for unconfined compressive strength and elastic moduli of tuffaceous rocks from Busted Butte near Yucca Mountain, Nevada. The data have been compiled for the Yucca Mountain Site Characterization Project Site and Engineering Properties Data Base. Experiments were conducted on water-saturated specimens of the potential nuclear waste repository horizon Topopah Spring Member tuff (thermal/mechanical unit TSw2). The influence of strain rate on mechanical properties of the tuff was examined by loading six specimens in uniaxial compression at a strain rate of 10-9 s-1. The experiments performed under ambient pressure and temperature conditions and conformed to Technical Procedure 91, titled ''Unconfined Compression Experiments at 22 degrees C and a Strain Rate of 10-9 s-1.'' The mean and standard deviation values of ultimate strength, Young's modulus and Poisson's ratio determined from these experiments are 85.4±21.7 MPa, 33.9±4.6 GPa, and 0.09±0.07, respectively

  16. In situ compressive strength analysis as an aid in fixed cutter bit selection and performance

    Energy Technology Data Exchange (ETDEWEB)

    Fabian, R.T.

    1997-07-01

    During the past 10 years, numerous analysis programs have been developed which derive continuous compressive strength profiles from well log data. Their primary purpose is to determine formation drillability to aid bit selection. Having a quantified physical value of rock strength can be invaluable not only for making a bit selection, but also for choosing running parameters. The focus of this paper is on making practical use of rock strength profiles. The rock strength output used throughout the analysis is confined compressive strength (also referred to as in situ compressive strength). This approach is preferred because its value of prediction is related to the stresses existing downhole, unlike unconfined strength, where the value is determined at atmospheric pressure. Case studies are presented showing the value of in situ rock strength output in the successful selection of drill bits.

  17. Saturated-Unsaturated flow in a Compressible Leaky-unconfined Aquifer

    CERN Document Server

    Mishra, Phoolendra K; Kuhlman, Kristopher L

    2011-01-01

    An analytical solution is developed for three-dimensional flow towards a partially penetrating large-diameter well in an unconfined aquifer bounded below by an aquitard of finite or semi-infinite extent. The analytical solution is derived using Laplace and Hankel transforms, then inverted numerically. Existing solutions for flow in leaky unconfined aquifers neglect the unsaturated zone following an assumption of instantaneous drainage assumption due to Neuman [1972]. We extend the theory of leakage in unconfined aquifers by (1) including water flow and storage in the unsaturated zone above the water table, and (2) allowing the finite-diameter pumping well to partially penetrate the aquifer. The investigation of model-predicted results shows that leakage from an underlying aquitard leads to significant departure from the unconfined solution without leakage. The investigation of dimensionless time-drawdown relationships shows that the aquitard drawdown also depends on unsaturated zone properties and the pumping...

  18. Saturated-unsaturated flow in a compressible leaky-unconfined aquifer

    Science.gov (United States)

    Mishra, Phoolendra K.; Vesselinov, Velimir V.; Kuhlman, Kristopher L.

    2012-06-01

    An analytical solution is developed for three-dimensional flow towards a partially penetrating large-diameter well in an unconfined aquifer bounded below by a leaky aquitard of finite or semi-infinite extent. The analytical solution is derived using Laplace and Hankel transforms, then inverted numerically. Existing solutions for flow in leaky unconfined aquifers neglect the unsaturated zone following an assumption of instantaneous drainage due to Neuman. We extend the theory of leakage in unconfined aquifers by (1) including water flow and storage in the unsaturated zone above the water table, and (2) allowing the finite-diameter pumping well to partially penetrate the aquifer. The investigation of model-predicted results shows that aquitard leakage leads to significant departure from the unconfined solution without leakage. The investigation of dimensionless time-drawdown relationships shows that the aquitard drawdown also depends on unsaturated zone properties and the pumping-well wellbore storage effects.

  19. Saturated-Unsaturated flow in a Compressible Leaky-unconfined Aquifer

    OpenAIRE

    Mishra, Phoolendra K.; Vessilinov, Velimir V.; Kuhlman, Kristopher L.

    2011-01-01

    An analytical solution is developed for three-dimensional flow towards a partially penetrating large-diameter well in an unconfined aquifer bounded below by an aquitard of finite or semi-infinite extent. The analytical solution is derived using Laplace and Hankel transforms, then inverted numerically. Existing solutions for flow in leaky unconfined aquifers neglect the unsaturated zone following an assumption of instantaneous drainage assumption due to Neuman [1972]. We exte...

  20. Compressive Strength of Autoclaved Aerated Concrete Blockwork

    OpenAIRE

    Y.A. Daou

    2001-01-01

    One of the basic problems in the design of masonry structures is the calculation of the compressive strength of masonry walls. This paper discusses the various parameters which affect the compressive strength of Autoclaved Aerated concrete blockwork with particular reference to the British Standard BS 5628: Part 1 and the Draft Eurocode EC6. Thirty six blockwork wallettes made of Autoclaved Aerated concrete blockwork were built and tested together with the corresponding properties of the unit...

  1. COMPRESSIVE STRENGTH TESTING OF EARTH MORTARS

    OpenAIRE

    Givanildo Alves Azeredo; Jean-Claude Morel; Normando Perazzo Barbosa

    2007-01-01

    This paper discusses the compressive strength of earth mortars. The goal is to use these mortars for masonry construction. Although it is necessary to study the whole masonry behaviour, the scope of this paper refers to the mortar only, without taking into account the blocks. As with other masonry units, compressive strength is a basic measure of quality for masonry mortars. However, there is a great variety of methodology for determining their parameters and properties, such as different sam...

  2. Compressive Strength of Autoclaved Aerated Concrete Blockwork

    Directory of Open Access Journals (Sweden)

    Y.A. Daou

    2001-01-01

    Full Text Available One of the basic problems in the design of masonry structures is the calculation of the compressive strength of masonry walls. This paper discusses the various parameters which affect the compressive strength of Autoclaved Aerated concrete blockwork with particular reference to the British Standard BS 5628: Part 1 and the Draft Eurocode EC6. Thirty six blockwork wallettes made of Autoclaved Aerated concrete blockwork were built and tested together with the corresponding properties of the units. The parameters examined were unit strength, mortar strength and size of the units. For the range of the block width (i.e. 100mm and 200mm, The strength of the wallettes were not significantly affected by the height/width ratio of the unit. Higher block strength yielded higher wallette stergnth, but only a slight difference in the strength of wallettes built with mortar designation (iii and (iv (i.e. 1:1:6 and 1: 2:9 by volume, cement: lime: sand respectively was obtained. The methods used in the British Standard BS 5628 and the Eurocode EC6 for the determination of the compressive strenght of masonry are reviewd and compared with the test results.

  3. Optimization of compressive strength in admixture-reinforced cement-based grouts

    Directory of Open Access Journals (Sweden)

    Sahin Zaimoglu, A.

    2007-12-01

    Full Text Available The Taguchi method was used in this study to optimize the unconfined (7-, 14- and 28-day compressive strength of cement-based grouts with bentonite, fly ash and silica fume admixtures. The experiments were designed using an L16 orthogonal array in which the three factors considered were bentonite (0%, 0.5%, 1.0% and 3%, fly ash (10%, 20%, 30% and 40% and silica fume (0%, 5%, 10% and 20% content. The experimental results, which were analyzed by ANOVA and the Taguchi method, showed that fly ash and silica fume content play a significant role in unconfined compressive strength. The optimum conditions were found to be: 0% bentonite, 10% fly ash, 20% silica fume and 28 days of curing time. The maximum unconfined compressive strength reached under the above optimum conditions was 17.1 MPa.En el presente trabajo se ha intentado optimizar, mediante el método de Taguchi, las resistencias a compresión (a las edades de 7, 14 y 28 días de lechadas de cemento reforzadas con bentonita, cenizas volantes y humo de sílice. Se diseñaron los experimentos de acuerdo con un arreglo ortogonal tipo L16 en el que se contemplaban tres factores: la bentonita (0, 0,5, 1 y 3%, las cenizas volantes (10, 20, 30 y 40% y el humo de sílice (0, 5, 10 y 20% (porcentajes en peso del sólido. Los datos obtenidos se analizaron con mediante ANOVA y el método de Taguchi. De acuerdo con los resultados experimentales, el contenido tanto de cenizas volantes como de humo de sílice desempeña un papel significativo en la resistencia a compresión. Por otra parte, las condiciones óptimas que se han identificado son: 0% bentonita, 10% cenizas volantes, 20% humo de sílice y 28 días de tiempo de curado. La resistencia a compresión máxima conseguida en las anteriores condiciones era de 17,1 MPa.

  4. Temperature dependence of uniaxial compressive strength of Hnilec granite

    OpenAIRE

    Laba? Milan

    1997-01-01

    Paper presents the results of the temperature dependence of uniaxial compressive strength of Hnilec Granite. The measurements of the uniaxial compressive strength were carried out at five different temperatures.

  5. Compressive strength of interocclusal recording materials.

    Science.gov (United States)

    Keyf, F; Altunsoy, S

    2001-01-01

    Many materials are used for making interocclusal records to mount casts on dental articulators. The strength of these materials during the compressive forces encountered in the mounting process is important because any deformation will cause incorrect occlusal relationships. This investigation compared the deformation of 4 thicknesses (2 mm, 5 mm, 10 mm, 20 mm), when subjected to 25 N compressive force, of 3 interocclusal recording materials: condensation silicone, recording wax, and rubber-based polyvinylsiloxane. Significant differences were recorded for all materials of 20 mm, 10 mm and 2 mm thickness. However, there was no significant difference among the 5 mm groups. Interocclusal records should be made of a minimal thickness, using a recording material which exhibits minimal distortion during compression. PMID:11210251

  6. Investigating conversion of endplate chondrocytes induced by intermittent cyclic mechanical unconfined compression in three-dimensional cultures.

    Science.gov (United States)

    Xu, H G; Zhang, W; Zheng, Q; Yu, Y F; Deng, L F; Wang, H; Liu, P; Zhang, M

    2014-01-01

    Mechanical stimulation is known to regulate the calcification of endplate chondrocytes. The ANK protein has a strong influence on anti-calcification by transports intracellular inorganic pyrophosphate (PPi) to the extracellular. It is known that TGF-?1 is able to induced Ank gene expression and protect chondrocyte calcification. Intermittent cyclic mechanical tension (ICMT) could induce calcification of endplate chondrocytes by decrease the expression of Ank gene. In this study, we investigated the relation of intermittent cyclic mechanical unconfined compression (ICMC) and Ank gene expression. We found that ICMC decreased the Ank gene expression in the endplate chondrocytes, and there was an decreased in the  TGF-?1 expression after ICMC stimulation. The Ank gene expression significantly increased when treated by transforming growth factor alpha 1 (TGF-?1) in a dose-dependent manner and decreased when treated by SB431542 (ALK inhibitor) in a dose-dependent manner. Our results implicate that ICMC-induced downregulation of Ank gene expression may be regulated by TGF-?1 in endplate chondrocytes. PMID:25308847

  7. Investigating conversion of endplate chondrocytes induced by intermittent cyclic mechanical unconfined compression in three-dimensional cultures

    Directory of Open Access Journals (Sweden)

    H.G. Xu

    2014-07-01

    Full Text Available Mechanical stimulation is known to regulate the calcification of endplate chondrocytes. The ANK protein has a strong influence on anti-calcification by transports intracellular inorganic pyrophosphate (PPi to the extracellular. It is known that TGF-?1 is able to induced Ank gene expression and protect chondrocyte calcification. Intermittent cyclic mechanical tension (ICMT could induce calcification of endplate chondrocytes by decrease the expression of Ank gene. In this study, we investigated the relation of intermittent cyclic mechanical unconfined compression (ICMC and Ank gene expression. We found that ICMC decreased the Ank gene expression in the endplate chondrocytes, and there was an decreased in the  TGF-?1 expression after ICMC stimulation. The Ank gene expression significantly increased when treated by transforming growth factor alpha 1 (TGF-?1 in a dose-dependent manner and decreased when treated by SB431542 (ALK inhibitor in a dose-dependent manner. Our results implicate that ICMC-induced downregulation of Ank gene expression may be regulated by TGF-?1 in endplate chondrocytes.

  8. Compressive strength of delaminated aerospace composites.

    Science.gov (United States)

    Butler, Richard; Rhead, Andrew T; Liu, Wenli; Kontis, Nikolaos

    2012-04-28

    An efficient analytical model is described which predicts the value of compressive strain below which buckle-driven propagation of delaminations in aerospace composites will not occur. An extension of this efficient strip model which accounts for propagation transverse to the direction of applied compression is derived. In order to provide validation for the strip model a number of laminates were artificially delaminated producing a range of thin anisotropic sub-laminates made up of 0°, ±45° and 90° plies that displayed varied buckling and delamination propagation phenomena. These laminates were subsequently subject to experimental compression testing and nonlinear finite element analysis (FEA) using cohesive elements. Comparison of strip model results with those from experiments indicates that the model can conservatively predict the strain at which propagation occurs to within 10 per cent of experimental values provided (i) the thin-film assumption made in the modelling methodology holds and (ii) full elastic coupling effects do not play a significant role in the post-buckling of the sub-laminate. With such provision, the model was more accurate and produced fewer non-conservative results than FEA. The accuracy and efficiency of the model make it well suited to application in optimum ply-stacking algorithms to maximize laminate strength. PMID:22431756

  9. Axial Compressive Strength of Foamcrete with Different Profiles and Dimensions

    Directory of Open Access Journals (Sweden)

    Othuman Mydin M.A.

    2014-01-01

    Full Text Available Lightweight foamcrete is a versatile material; primarily consist of a cement based mortar mixed with at least 20% volume of air. High flow ability, lower self-weight, minimal requirement of aggregate, controlled low strength and good thermal insulation properties are a few characteristics of foamcrete. Its dry densities, typically, is below 1600kg/m3 with compressive strengths maximum of 15MPa. The ASTM standard provision specifies a correction factor for concrete strengths of between 14 and 42MPa to compensate for the reduced strength when the aspect height-to-diameter ratio of specimen is less than 2.0, while the CEB-FIP provision specifically mentions the ratio of 150 x 300mm cylinder strength to 150 mm cube strength. However, both provisions requirements do not specifically clarify the applicability and/or modification of the correction factors for the compressive strength of foamcrete. This proposed laboratory work is intended to study the effect of different dimensions and profiles on the axial compressive strength of concrete. Specimens of various dimensions and profiles are cast with square and circular cross-sections i.e., cubes, prisms and cylinders, and to investigate their behavior in compression strength at 7 and 28 days. Hypothetically, compressive strength will decrease with the increase of concrete specimen dimension and concrete specimen with cube profile would yield comparable compressive strength to cylinder (100 x 100 x 100mm cube to 100dia x 200mm cylinder.

  10. Application of size effect to compressive strength of concrete members

    Indian Academy of Sciences (India)

    Jin-Keun Kim; Seong-Tae Yi

    2002-08-01

    It is important to consider the effect of size when estimating the ultimate strength of a concrete member under various loading conditions. Well known as the size effect, the strength of a member tends to decrease when its size increases. Therefore, in view of recent increased interest in the size effect of concrete this research focuses on the size effect of two main classes of compressive strength of concrete: pure axial compressive strength and ?exural compressive strength. First, fracture mechanics type size effect on the compressive strength of cylindrical concrete specimens was studied, with the diameter, and the height/diameter ratio considered as the main parameters. Theoretical and statistical analyses were conducted, and a size effect equation was proposed to predict the compressive strength specimens. The proposed equation showed good agreement with the existing test results for concrete cylinders. Second, the size, length, and depth variations of a ?exural compressive member have been studied experimentally. A series of -shaped specimens subjected to axial compressive load and bending moment were tested. The shape of specimens and the test procedures used were similar to those by Hognestad and others. The test results are curve-?tted using Levenberg-Marquardt’s least squares method (LSM) to obtain parameters for the modi?ed size effect law (MSEL) by Kim and co workers. The results of the analysis show that the effect of specimen size, length, and depth on ultimate strength is signi?cant. Finally, more general parameters for MSEL are suggested.

  11. STRENGTH SHRINKAGE AND CREEP OF CONCRETE IN TENSION AND COMPRESSION

    Directory of Open Access Journals (Sweden)

    S A Kristiawan

    2006-01-01

    Full Text Available Strength, shrinkage and creep of concrete in tension and compression have been determined and the relationship between those properties was studied. Direct tensile tests were applied to measure those properties in tension. The relationship of creep in tension and compression was determined based on the measurement of creep at similar stress and similar stress/strength ratio. It is found that concrete deforms more in tension than in compression. Except for concrete with a higher water/cement ratio, the use of pulverised fuel ash, ground granulated blast furnace slag, superplasticizer and shrinkage reducing admixture has no effect on strength. However, they affect creep and shrinkage of concrete.

  12. Ultimate Strength Analysis of Stiffened Plate Under Longitudinal Compression, Transverse Compression and Lateral Pressure

    Directory of Open Access Journals (Sweden)

    Ta Hong Phong1a,

    2015-10-01

    Full Text Available The ship hull can be considered as a thin – walled box gider constituted by stiffened panels. In order to research the ship ultimate strength, the ultimate strength of stiffened panel must be considered. Stiffened plates are typical structure of ship. Ultimate strength analysis of stiffened plate for the analysis of ships' structures. In present paper, the nonlinear finite element method is employed to predict the ultimate strength of stiffened plate model under longitudinal compression, transverse compression, lateral pressure.

  13. Compressive strength and rheology of environmentally-friendly binders

    Directory of Open Access Journals (Sweden)

    Juan Manuel Lizarazo Marriaga

    2010-07-01

    Full Text Available Ordinary Portland cement production accounts for 9% of worldwide greenhouse gas emissions. This paper summarises the results of research aimed at developing environmentally-friendly binders which can be used as an alternative in civil construction, aimed at generating alternatives and sustainable materials. Mixes of the combination of granulated ground blast furnace slag, basic oxygen slag, cement kiln dust and plasterboard gypsum were used for optimising the binders, according to their compressive strength, to obtain 5 concrete mixtures made partially or completely with industrial waste. The results showed that the compressive strength of mixtures of Portland cement and industrial waste were suitable for different civil construction applications and, although mixtures formed entirely from industrial waste had a significant decrease in their compressive strength, the results sho- wed great potential for specific industrial applications. In addition to compressive strength, the rheological properties of these mixtures were determined for defining flow and workability characteristics.

  14. Compressive strength of brick masonry made with weak mortars

    DEFF Research Database (Denmark)

    Pedersen, Erik Steen; Hansen, Klavs Feilberg

    2013-01-01

    The use of weak mortar has a number of advantages (e.g. prevention of expansion joints, environmental issues). However, according to EC6, the strength of masonry vanishes when the compressive strength of the mortar approaches zero. In reality the presence of even unhardened mortar kept in place in the joint will ensure a certain level of load-carrying capacity. This is due to the interaction between compression in the weak mortar and tension in the adjacent bricks. This paper proposes an expression for the compressive strength of masonry made with weak lime mortars (fm<1N/mm2) in which the strength of masonry depends only on the strength of the bricks. A compression failure in masonry made with weak mortars occurs as a tension failure in the bricks, as they seek to prevent the mortar from being pressed out of the joints. The expression is derived by assuming hydrostatic pressure in the mortar joints, which is the most unfavourable stress distribution with respect to tensile stresses in bricks. The expressionis compared with the results of compression tests of masonry made with weak mortars. It can take into account bricks with arbitrary dimensions as well as perforated bricks. For a stronger mortar (fm?6 N/mm2) compression tests of masonry with perforated bricks show that the EC6 expression is not always safe for Danish masonry. This is probably because the tensile strength of the bricks also has an effect on the compressive strength of masonry when the mortar is stronger than weak lime mortar. An extended version of the EC6 expression for the compressive strength of masonry is proposed, which includes the effect in question.

  15. Comparison Of Compressive Strength Of Medium Strength Self Compacted Concrete By Different Curing Techniques

    Directory of Open Access Journals (Sweden)

    Prof. Nanak J Pamnani1, Dr. A.K. Verma2, Dr. D.R. Bhatt

    2013-05-01

    Full Text Available : In this paper variation in compressive strength of medium strength, self-compacted concrete with 3 different curing techniques is discussed. Initially several trials were carried out for mix design of medium strength selfcompacting concrete. Once the mix design was achieved, three batches of concrete cubes were cast as per ASTM standard. Water cement ratio and admixture dose were kept constant as required by selected Mix Design. Slump Test was carried out on each batch in order to ascertain concrete flow for self-compacting concrete. First batch was cured in a temperature controlled curing tank in the laboratory. The second batch was cured by the application of an external curing compound under prevailing site conditions. The 3rd batch was cured with internal curing agent. From each batch, 3 cubes were tested for compressive strength at 3-days age, at 7 days age and 28 days age of concrete and average values were taken. Results were analyzed and graphs were drawn.It was noted that 28-days compressive strength of cubes cured by applying curing compound was 91 % of the compressive strength of cubes cured in water tank in the laboratory (i.e., 09 % less.Similarly compressive strength of cubes cured by Internal curing compound was 95 % of the compressive strength of cubes cured in the laboratory (i.e., 05% less. So it was concluded that in areas with shortage of water, curing compounds can be effectively used with improved strength and sustainability of selfcompacted concrete

  16. Comparison of Open-Hole Compression Strength and Compression After Impact Strength on Carbon Fiber/Epoxy Laminates for the Ares I Composite Interstage

    Science.gov (United States)

    Hodge, Andrew J.; Nettles, Alan T.; Jackson, Justin R.

    2011-01-01

    Notched (open hole) composite laminates were tested in compression. The effect on strength of various sizes of through holes was examined. Results were compared to the average stress criterion model. Additionally, laminated sandwich structures were damaged from low-velocity impact with various impact energy levels and different impactor geometries. The compression strength relative to damage size was compared to the notched compression result strength. Open-hole compression strength was found to provide a reasonable bound on compression after impact.

  17. Correlation between compressive strength and ultrasonic pulse velocity of high strength concrete incorporating chopped basalt fibre

    Science.gov (United States)

    Shafiq, Nasir; Fadhilnuruddin, Muhd; Elshekh, Ali Elheber Ahmed; Fathi, Ahmed

    2015-07-01

    Ultrasonic pulse velocity (UPV), is considered as the most important test for non-destructive techniques that are used to evaluate the mechanical characteristics of high strength concrete (HSC). The relationship between the compressive strength of HSC containing chopped basalt fibre stands (CBSF) and UPV was investigated. The concrete specimens were prepared using a different ratio of CBSF as internal strengthening materials. The compressive strength measurements were conducted at the sample ages of 3, 7, 28, 56 and 90 days; whilst, the ultrasonic pulse velocity was measured at 28 days. The result of HSC's compressive strength with the chopped basalt fibre did not show any improvement; instead, it was decreased. The UPV of the chopped basalt fibre reinforced concrete has been found to be less than that of the control mix for each addition ratio of the basalt fibre. A relationship plot is gained between the cube compressive strength for HSC and UPV with various amounts of chopped basalt fibres.

  18. Strength and texture of Pt compressed to 63?GPa

    International Nuclear Information System (INIS)

    Angle- and energy-dispersive X-ray diffraction experiments in a radial geometry were performed in the diamond anvil cell on polycrystalline platinum samples at pressures up to 63?GPa. Observed yield strength and texture depend on grain size. For samples with 70–300-nm particle size, the yield strength is 5–6?GPa at ?60?GPa. Coarse-grained (?2-?m particles) Pt has a much lower yield strength of 1–1.5?GPa at ?60?GPa. Face-centered cubic metals Pt and Au have lower strength to shear modulus ratio than body-centered cubic or hexagonal close-packed metals. While a 300-nm particle sample exhibits the ?110? texture expected of face-centered-cubic metals under compression, smaller and larger particles show a weak mixed ?110? and ?100? texture under compression. Differences in texture development may also occur due to deviations from uniaxial stress under compression in the diamond anvil cell

  19. Effect of Hand Mixing on the Compressive Strength of Concrete

    Directory of Open Access Journals (Sweden)

    James Isiwu AGUWA

    2010-12-01

    Full Text Available This paper presents the effect of hand mixing on the compressive strength of concrete. Before designing the concrete mix, sieve analysis of sharp sand and chippings was carried out and their fineness moduli were determined. Also the dry weight of chippings and the specific gravities of both sand and chippings were determined. A designed concrete mix of 1:2:4 was used and the number of turnings of the mixture over from one end to another by hand mixing was varying from one time up to and including seven times. The strengths were measured at the curing ages of 7, 14, 21 and 28 days respectively using 150mm concrete cubes cast, cured and crushed. The results revealed that the compressive strengths of concrete cubes appreciably increased with increase in number of turnings from one to four times but remained almost constant beyond four times of turning for all the ages tested. For example, at 1, 2, and 3 times turning; the compressive strengths at 28 days were 4.67, 13.37 and 20.28N/mm2 respectively while at 4, 5 and 6 times turning; the compressive strengths at 28 days were 21.15, 21.34 and 21.69N/mm2. From the data, adequate strengths were not developed at turnings below three times of hand mixing, concluding that a minimum of three times turning is required to produce concrete with satisfactory strength.

  20. Compressive Strength of Longitudinally Stiffened GRP Panels

    DEFF Research Database (Denmark)

    Böhme, J.; Noury, P.; Riber, Hans Jørgen; Verdier, Guillaume Henry C.

    1996-01-01

    A structural analysis of a cross stiffened orthotropic GRP panel subjected to uniaxial compressive loads is carried out. Analytical solutions to the buckling of such structures are proposed and validated by a finite element analysis. Both analytical and finite element approaches confirm an identical failure scenario. In the present case, the load carring capacity of the stiffened panel is limited by the plate buckling capability.

  1. Compressive strength of brick masonry made with weak mortars

    DEFF Research Database (Denmark)

    Pedersen, Erik Steen; Hansen, Klavs Feilberg

    2013-01-01

    The use of weak mortar has a number of advantages (e.g. prevention of expansion joints, environmental issues). However, according to EC6, the strength of masonry vanishes when the compressive strength of the mortar approaches zero. In reality the presence of even unhardened mortar kept in place in the joint will ensure a certain level of load-carrying capacity. This is due to the interaction between compression in the weak mortar and tension in the adjacent bricks. This paper proposes an express...

  2. COMPRESSIVE STRENGTH AND SORPTIVITY PROPERTIES OF PET FIBER REINFORCED CONCRETE

    OpenAIRE

    R. N. Nibudey; P. B. Nagarnaik; D. K. Parbat; A. M. Pande

    2014-01-01

    This paper presents experimental results of compressive strength and sorptivity for normal concrete and PET fiber reinforced concrete (PFRC). The PET fibers used in this study were obtained manually from waste mineral water bottles. Two grades, M20 and M30, of concrete and two fiber geometry of aspect ratios 35 and 50 with fiber volume fractions 0.0 to 3.0% were used in the experiments. Each specimen was tested after 28 days of curing. It was found that the compressive strength of PFRC increa...

  3. Relationship between the Compressive and Tensile Strength of Recycled Concrete

    International Nuclear Information System (INIS)

    Concrete recycling consists of crushing the concrete provided by demolishing the old constructions, and of using the resulted small pieces as aggregates in the new concrete compositions. The resulted aggregates are called recycled aggregates and the new mix of concrete containing a percentage of recycled aggregates is called recycled concrete. Our previous researches have indicated the optimal percentages of recycled aggregates to be used for different cases of recycled concrete related to the original aggregates nature. All results have shown that the concrete compressive strength is significantly reduced when using recycled aggregates. In order to obtain realistic values of compressive strength, some tests have been carried out by adding water-reducer plasticizer and a specified additional quantity of cement. The results have shown that for a limited range of plasticizer percentage, and a fixed value of additional cement, the compressive strength has reached reasonable value. This paper treats of the effect of using recycled aggregates on the tensile strength of concrete, where concrete results from the special composition defined by our previous work. The aim is to determine the relationship between the compressive and tensile strength of recycled concrete. (author)

  4. Compression strength perpendicular to grain of structural timber and glulam

    DEFF Research Database (Denmark)

    Damkilde, Lars; Hoffmeyer, Preben; Pedersen, Torben N.

    1998-01-01

    The characteristic strength values for compression perpendicular to grain as they appear in EN 338 (structural timber) and EN 1194 (glulam) are currently up for discussion. The present paper provides experimental results based on EN 1193 that may assist in the correct assignment of such strength values. The dominant failure mode of glulam specimens is shown to be fundamentally different from that of structural timber specimens. Glulam specimens often show tension perpendicular to grain failure b...

  5. Evaluation of Adhesive and Compressive Strength of Glass Ionomer Cements

    OpenAIRE

    Ramashanker,; Raghuwar D Singh; Chand, Pooran; Jurel, Sunit Km.; Tripathi, Shuchi

    2011-01-01

    The aim of the study was to assess, compare and evaluate the adhesive strength and compressive strength of different brands of glass ionomer cements to a ceramometal alloy. (A) Glass ionomer cements: GC Fuji II (GC Corporation, Tokyo), Chem Flex (Dentsply DeTrey, Germany), Glass ionomer FX (Shofu-11, Japan), MR dental (MR dental suppliers Pvt Ltd, England). (B) Ceramometal alloy (Ni–Cr: Wiron 99; Bego, Bremen, Germany). (C) Cold cure acrylic resin. (E) Temperature cum humidity control chamber...

  6. Compression Strength of Composite Primary Structural Components

    Science.gov (United States)

    Johnson, Eric R.

    1998-01-01

    Research conducted under NASA Grant NAG-1-537 focussed on the response and failure of advanced composite material structures for application to aircraft. Both experimental and analytical methods were utilized to study the fundamental mechanics of the response and failure of selected structural components subjected to quasi-static loads. Most of the structural components studied were thin-walled elements subject to compression, such that they exhibited buckling and postbuckling responses prior to catastrophic failure. Consequently, the analyses were geometrically nonlinear. Structural components studied were dropped-ply laminated plates, stiffener crippling, pressure pillowing of orthogonally stiffened cylindrical shells, axisymmetric response of pressure domes, and the static crush of semi-circular frames. Failure of these components motivated analytical studies on an interlaminar stress postprocessor for plate and shell finite element computer codes, and global/local modeling strategies in finite element modeling. These activities are summarized in the following section. References to literature published under the grant are listed on pages 5 to 10 by a letter followed by a number under the categories of journal publications, conference publications, presentations, and reports. These references are indicated in the text by their letter and number as a superscript.

  7. Comparison Of Compressive Strength Of Medium Strength Self Compacted Concrete By Different Curing Techniques

    OpenAIRE

    Prof. Nanak J Pamnani1, Dr. A.K. Verma2, Dr. D.R. Bhatt

    2013-01-01

    : In this paper variation in compressive strength of medium strength, self-compacted concrete with 3 different curing techniques is discussed. Initially several trials were carried out for mix design of medium strength selfcompacting concrete. Once the mix design was achieved, three batches of concrete cubes were cast as per ASTM standard. Water cement ratio and admixture dose were kept constant as required by selected Mix Design. Slump Test was carried out on each batch in order to ascertain...

  8. Unfired clay bricks – moisture properties and compressive strength

    DEFF Research Database (Denmark)

    Hansen, E.J. de Place; Hansen, Kurt Kielsgaard

    2002-01-01

    Apparatus, methods and test results from an experimental investigation of (1) the properties for moisture performance of the materials, including water vapour sorption and water vapour transmission, (2) humidity buffering of the indoor climate by an absorbent material, and (3) the compressive strength are presented.

  9. Neutron irradiation of sapphire for compressive strengthening. I. Processing conditions and compressive strength

    International Nuclear Information System (INIS)

    Sapphire suffers a dramatic loss of c-axis compression strength at elevated temperatures. Irradiation of sapphire with fission-spectrum neutrons to an exposure of ?1022 neutrons/m2 in the core of a 1 MW fission reactor increased the c-axis compression strength by a factor of ?3 at 600 deg. C. Strength was similarly improved when 99% of slow neutrons (?0.1 eV) were removed by 10B and Cd shields during irradiation. Annealing at 600 deg. C for 10 min changed the yellow-brown color of irradiated sapphire to pale yellow, but had no effect on compressive strength. Annealing irradiated sapphire at 1200 deg. C for 24 h reduced the compressive strength to its baseline value. Transmission electron microscopy suggests that fast-neutron-induced displacement damage inhibits the propagation of r-plane twins which are responsible for the low compressive strength. When irradiated with 10B and Cd shielding, sapphire that was not grown in iridium crucibles is safe for unrestricted handling after 1 month

  10. The effect of shear strength on isentropic compression experiments

    Science.gov (United States)

    Thomson, Stuart; Howell, Peter; Ockendon, John; Ockendon, Hilary

    2015-06-01

    Isentropic compression experiments (ICE) are a novel way of obtaining equation of state information for metals undergoing violent plastic deformation. In a typical experiment, millimetre thick metal samples are subjected to pressures on the order of 10 -102 GPa, while the yield strength of the material can be as low as 10-1GPa. The analysis of such experiments has so far neglected the effect of shear strength, instead treating the highly plasticised metal as an inviscid compressible fluid. However making this approximation belies the basic elastic nature of a solid object. A more accurate method should strive to incorporate the small but measurable effects of shear strength. Here we present a one-dimensional mathematical model for elastoplasticity at high stress which allows for both compressibility and the shear strength of the material. In the limit of zero yield stress this model reproduces the hydrodynamic models currently used to analyse ICEs. We will also show using a systematic asymptotic analysis that entropy changes are universally negligible in the absence of shocks. Numerical solutions of the governing equations will then be presented for problems relevant to ICEs in order to investigate the effects of shear strength over a model based purely on hydrodynamics.

  11. Prediction of Compressive Strength of Concrete using Artificial Neural Network

    Directory of Open Access Journals (Sweden)

    Wankhade M W

    2013-07-01

    Full Text Available Concrete cube strength determination tests are usually performed at three days to one year afterpouring the concrete. The waiting period required to perform such test may delay the construction progress,decision making and neglecting such test would limit the quality control checks in large constructionprojects. Therefore it becomes necessary that the rapid and reliable prediction of concrete strength isessential for pre-design or quality control of construction. It is possible to facilitate the modification of themix proportion if the concrete does not meet the required design stage, which may save time andconstruction costs. The early prediction of concrete strength is essential for estimating the desirable time forconcrete form removal, project scheduling, quality control and estimating delay if any. Artificial NeuralNetwork (ANN is used to predict the compressive strength of concrete. Standard back propagation andJordan–Elman algorithms are used to train the networks. Networks are trained and tested at various learningrate and momentum factor and after many trials these were kept constant for this study. Performance ofnetworks were checked with statistical error criteria of correlation coefficient, root mean squared error andmean absolute error. It is observed that artificial neural networks can predict compressive strength ofconcrete with 91 to 98 % accuracy.

  12. Compressive strength of human openwedges: a selection method

    Science.gov (United States)

    Follet, H.; Gotteland, M.; Bardonnet, R.; Sfarghiu, A. M.; Peyrot, J.; Rumelhart, C.

    2004-02-01

    A series of 44 samples of bone wedges of human origin, intended for allograft openwedge osteotomy and obtained without particular precautions during hip arthroplasty were re-examined. After viral inactivity chemical treatment, lyophilisation and radio-sterilisation (intended to produce optimal health safety), the compressive strength, independent of age, sex and the height of the sample (or angle of cut), proved to be too widely dispersed [ 10{-}158 MPa] in the first study. We propose a method for selecting samples which takes into account their geometry (width, length, thicknesses, cortical surface area). Statistical methods (Principal Components Analysis PCA, Hierarchical Cluster Analysis, Multilinear regression) allowed final selection of 29 samples having a mean compressive strength ?_{max} =103 MPa ± 26 and with variation [ 61{-}158 MPa] . These results are equivalent or greater than average materials currently used in openwedge osteotomy.

  13. Optimization of compressive strength of zirconia based dental composites

    Indian Academy of Sciences (India)

    U V Hambire; V K Tripathi

    2014-10-01

    Dental composites are tooth-coloured restorative material used by dentists for various applications. Restoration of a lost tooth structure requires a material having mechanical as well as aesthetic properties similar to that of tooth. This poses challenges to engineers and the dentist alike. Dental composites consist of a matrix and a dispersed phase called filler, which are mainly responsible for its mechanical properties. Most commonly used matrix is bisphenol glycidyl methacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGMA). Silica and glass are conventional fillers used in the past. Recently, zirconia is being used due to its improved mechanical properties. A study was conducted to evaluate the contribution of zirconia to the mechanical properties in general and compressive strength in particular. We have attempted to make an experimental dental composite with a conglomerate of nanofillers, namely, zirconia, glass and silica, and optimize this filler volume percentage and obtain an optimum compressive strength for the experimental dental composite.

  14. Compressive strength of human openwedges: a selection method

    OpenAIRE

    Follet, Hélène; Gotteland, Maurice; Bardonnet, Raphaël; Sfarghiu, Ana-Maria; Peyrot, Jacques; Rumelhart, Claude

    2004-01-01

    A series of 44 samples of bone wedges of human origin, intended for allograft openwedge osteotomy and obtained without particular precautions during hip arthroplasty were re-examined. After viral inactivity chemical treatment, lyophilisation and radio-sterilisation ( intended to produce optimal health safety), the compressive strength, independent of age, sex and the height of the sample ( or angle of cut), proved to be too widely dispersed [10-158 MPa] in the first study. We propose a method...

  15. Estimating compressive strength of concrete by mortar testing

    OpenAIRE

    Camões, Aires; Aguiar, J. L. Barroso de; Jalali, Said, ed. lit.

    2005-01-01

    Concrete mix design laboratory tests which time consuming and entails considerable effort. This study presents a method of reducing mix design testing costs by testing mortar instead of concrete specimens. The experimental programme consisted of defining mortar mixes equivalent to concrete mixes, moulding specimens of both mortar and concrete mixes studied and finally evaluating the compressive strength of specimens cured at different curing time. Results obtained indicate that a goo...

  16. Compressive Strength of a Longitudinally Stiffened FRP Panel

    DEFF Research Database (Denmark)

    Riber, Hans Jørgen; Jensen, Jørgen Juncher; Pedersen, Preben Terndrup

    1997-01-01

    A structural analysis of a cross stiffened orthotropic FRP panel subjected to uni-axial compressive load is crarried out. Analytical Calculations of the strength of the panel are presented and compared to finite element analysis performed by different authors. Both analytica and finite element approaches confirm an identical failrue scenario. In the present case, the load carrying capacity of the stiffened panel is limited by the plate stiffener debonding stress.

  17. Compressive Strength and Microstructure of Sugar Cane Bagasse Ash Concrete

    OpenAIRE

    Asma Abd Elhameed Hussein; Nasir Shafiq; Muhd Fadhil Nuruddin; Fareed Ahmed Memon

    2014-01-01

    This study presents the results of an experimental research study on the effectiveness of Sugar Cane Bagasse Ash (SCBA) as a cement replacement material in concrete production. The ordinary Portland cement was replaced with 0, 5, 10, 15, 20, 25 and 30%, respectively bagasse ash, the effect of Sugar cane Bagasse Ash on workability, compressive strength and microstructure of Interfacial Transition Zone (ITZ) of concrete was examined. The results showed that inclusion of Sugar cane Bagasse Ash i...

  18. Compressive Strength and Microstructure of Sugar Cane Bagasse Ash Concrete

    Directory of Open Access Journals (Sweden)

    Asma Abd Elhameed Hussein

    2014-03-01

    Full Text Available This study presents the results of an experimental research study on the effectiveness of Sugar Cane Bagasse Ash (SCBA as a cement replacement material in concrete production. The ordinary Portland cement was replaced with 0, 5, 10, 15, 20, 25 and 30%, respectively bagasse ash, the effect of Sugar cane Bagasse Ash on workability, compressive strength and microstructure of Interfacial Transition Zone (ITZ of concrete was examined. The results showed that inclusion of Sugar cane Bagasse Ash in concrete up to 20% level significantly enhanced the compressive strength of concrete at all ages; the highest compressive strength was obtained at 5% SCBA replacement level. The ITZ thickness was greatly reduced with increasing the bagasse ash replacement level up to 15%, beyond that the ITZ thickness was slightly increased, however the thickness was still narrower than the normal concrete, it was observed that at 15% bagasse ash replacement level, the interfacial transition zone was homogeneous and there was no gap between the coarse aggregate and the paste matrix.

  19. A model for compression after impact strength evaluation

    Science.gov (United States)

    Ilcewicz, Larry B.; Dost, Ernst F.; Coggeshall, Randy L.

    1989-01-01

    One key property commonly used for evaluating composite material performance is compression after impact strength (CAI). Standarad CAI tests typically use a specific laminate stacking sequence, coupon geometry, and impact level. In order to understand what material factors affect CAI, evaluation of test results should include more than comparisons of the measured strength for different materials. This study considers the effects of characteristic impact damage state, specimen geometry, material toughness, ply group thickness, undamaged strength, and failure mode. The results of parametric studies, using an analysis model developed to predict CAI, are discussed. Experimental results used to verify the model are also presented. Finally, recommended pre- and post-test CAI evaluation schemes which help link material behavior to structural performance are summarized.

  20. Effect of Metakaolin on Compressive Strength of Concrete

    Directory of Open Access Journals (Sweden)

    Satyendra Dubey

    2015-06-01

    Full Text Available Metakaolin is a cementitious materials used as an admixture to produce high strength concrete and is used for maintaining the consistency of concrete. In the case where insufficient or poor curing concrete structure like the underground structure which undergo serve loss of compressive strength, use of metakaolin proves to be very useful to modify the properties of concrete. This paper deals with the properties of concrete with varying percentage replacement of metakaolin in M-25 greade of concrete. The mix M1,M2,M3 and M4 were obtained by replacing 0,5,10 and 15 percent mass of cement by Metakaolin. The test results indicated that admixture metakaolin when used at optimum quantity tend to increase the strength of the concrete mix when compared with conventional concrete.

  1. INTRA-RING COMPRESSION STRENGTH OF LOW DENSITY HARDWOODS

    Directory of Open Access Journals (Sweden)

    Audrey Zink-Sharp

    2006-01-01

    Full Text Available Engineered wood composites are being crafted with increasingly smaller and smaller components, yet a search of the literature indicates a lack of intra-ring mechanical property data for almost all commercial wood types, particularly the underutilized low density hardwoods. In addition, there is no universally accepted testing regime for determining micromechanical properties of wood samples. As a result, we developed a testing system for determining compression, tension, and bending properties of growth ring regions of wood samples. Our microtesting system consists of a 45.4 kg load stage, motor drive, data acquisition system, motor control, load cell, strain transducer, and software. In this study, intra-ring compression strength parallel to the grain was determined for small samples (a few millimeters³ in volume of sweetgum (Liquidambar styraciflua, yellow-poplar (Liriodendron tulipifera, and red maple (Acer rubrum. It was determined that compression strength is weakly correlated with specific gravity but unrelated to growth rate. Specific gravity was also unrelated to growth rate. Sweetgum values were intermediate between yellow-poplar and red maple

  2. INTRA-RING COMPRESSION STRENGTH OF LOW DENSITY HARDWOODS

    Scientific Electronic Library Online (English)

    Audrey, Zink-Sharp; Carlile, Price.

    Full Text Available Engineered wood composites are being crafted with increasingly smaller and smaller components, yet a search of the literature indicates a lack of intra-ring mechanical property data for almost all commercial wood types, particularly the underutilized low density hardwoods. In addition, there is no u [...] niversally accepted testing regime for determining micromechanical properties of wood samples. As a result, we developed a testing system for determining compression, tension, and bending properties of growth ring regions of wood samples. Our microtesting system consists of a 45.4 kg load stage, motor drive, data acquisition system, motor control, load cell, strain transducer, and software. In this study, intra-ring compression strength parallel to the grain was determined for small samples (a few millimeters³ in volume) of sweetgum (Liquidambar styraciflua), yellow-poplar (Liriodendron tulipifera), and red maple (Acer rubrum). It was determined that compression strength is weakly correlated with specific gravity but unrelated to growth rate. Specific gravity was also unrelated to growth rate. Sweetgum values were intermediate between yellow-poplar and red maple

  3. Predicting compressive strength of different geopolymers by artificial neural networks

    OpenAIRE

    A. Nazari; Torgal, Fernando Pacheco

    2013-01-01

    In the present study,six different models based on artificial neural networks have been developed to predict the compressive strength of different types of geopolymers.The differences between the models were in the number of neurons in hidden layers and in the method of finalizing the models.Seven independent input parameters that cover the curing time,Ca(OH)2 content, the amount of superplasticizer, NaOH concentration,mold type,geopolymer type and H2O/Na2O molar ratio were considered.For ...

  4. Mechanical properties of Concrete with SAP. Part I: Development of compressive strength

    DEFF Research Database (Denmark)

    Hasholt, Marianne Tange; Jespersen, Morten H. Seneka; Jensen, Ole Mejlhede

    2010-01-01

    The development of mechanical properties has been studied in a test program comprising 15 different concrete mixes with 3 different w/c ratios and different additions of superabsorbent polymers (SAP). The degree of hydration is followed for 15 corresponding paste mixes. This paper concerns compressive strength. It shows that results agree well with a model based on the following: 1. Concrete compressive strength is proportional to compressive strength of the paste phase 2. Paste strength depends...

  5. Compressive strength of concrete containing fly ash, brine and admixtures

    Energy Technology Data Exchange (ETDEWEB)

    Al-Manaseer, A.; Haug, M.D.; Nasser, K.W.

    The effect of using brine on the compressive strength of concrete containing fly ash and admixtures was studied. The term brine, in this investigation, is restricted to the liquid solution obtained from potash mines that contains salts of sodium, potassium, calcium, and magnesium in the following respective percentages: 9.0, 5.0, 5.2, and 5.8. Four series of tests were performed in this study on concrete made from Type 1 (Ordinary Portland) and Type V (sulphate resisting) cement. High-calcium Saskatchewan fly ash was used as a replacement for cement by weight. Air-entraining agents and superplastics were also added to the mixes. The investigation found that the presence of 40 percent brine in the mixing fluid of concrete made from Type I or Type V cement and containing 35 percent fly ash increased the 28-day strength by about 8 percent over similar concrete containing no brine. The fly ash was an essential factor in obtaining increased strength with brine. The addition of superplasticizer was found to increase the 90-day strength of concrete containing brine.

  6. Strength and stiffness of thermally rectified eucalyptus wood under compression

    Scientific Electronic Library Online (English)

    Marcio Rogério da, Silva; Gilmara de Oliveira, Machado; José Otávio, Brito; Carlito, Calil Junior.

    2013-10-01

    Full Text Available The aim of this work was the evaluation of the thermal-rectification process of reforestation wood Corymbia citriodora Hook by measuring of mechanical properties under compression parallel to the grain and also determining of chemical composition. The tested samples were thermally treated in a furna [...] ce with nitrogen-atmosphere at heating rate of 0.033 ºC.min-1, at temperatures of 160, 180, 200, 220 and 240 ºC. The chemical components and mechanical properties were affected with the thermal rectification process. The contents ranged from 17.85 to 3.51% extractives, 30.44 to 53.86% lignin, 69.56 to 46.14% holocellulose and 0.31 to 0.47% ashes. The samples strength decreased from 20% to 50% and the elasticity modulus increased about 47%. The characteristic values of strength under compression were determined and these changes were about 23% lower than Brazilian standard. The best mechanical properties of Corymbia citriodora were obtained at 180 ºC.

  7. Compressive strength and hydrolytic stability of fly ash based geopolymers

    Directory of Open Access Journals (Sweden)

    Nikoli? Irena

    2013-01-01

    Full Text Available The process of geopolymerization involves the reaction of solid aluminosilicate materials with highly alkaline silicate solution yielding an aluminosilicate inorganic polymer named geopolymer, which may be successfully applied in civil engineering as a replacement for cement. In this paper we have investigated the influence of synthesis parameters: solid to liquid ratio, NaOH concentration and the ratio of Na2SiO3/NaOH, on the mechanical properties and hydrolytic stability of fly ash based geopolymers in distilled water, sea water and simulated acid rain. The highest value of compressive strength was obtained using 10 mol dm-3 NaOH and at the Na2SiO3/NaOH ratio of 1.5. Moreover, the results have shown that mechanical properties of fly ash based geopolymers are in correlation with their hydrolytic stability. Factors that increase the compressive strength also increase the hydrolytic stability of fly ash based geopolymers. The best hydrolytic stability of fly ash based geopolymers was shown in sea water while the lowest stability was recorded in simulated acid rain. [Projekat Ministarstva nauke Republike Srbije, br. 172054 i Nanotechnology and Functional Materials Center, funded by the European FP7 project No. 245916

  8. Effect of Banana Fibers on the Compressive and Flexural Strength of Compressed Earth Blocks

    Directory of Open Access Journals (Sweden)

    Marwan Mostafa

    2015-03-01

    Full Text Available Sustainable development of the built environment in developing countries is a major challenge in the 21st century. The use of local materials in construction of buildings is one of the potential ways to support sustainable development in both urban and rural areas. Building with Compressed Earthen Blocks (CEBs is becoming more popular due to their low cost and relative abundance of materials. The proposed Green-Compressed Earth Block (GCEB consists of ordinary CEB ingredients plus Banana fibers, which will be the focus of this study. Banana fibers are widely available worldwide as agricultural waste from Banana cultivation. Banana fibers are environmentally friendly and present important attributes, such as low density, light weight, low cost, high tensile strength, as well as being water and fire resistant. This kind of waste has a greater chance of being utilized for different application in construction and building materials. This focused on the use of banana fiber and its effect on the compressive and flexural strength in CEB. The deflection at the mid-span of the blocks studied was calculated using the Linear Variable Differential Transformer (LVDT. The results of this study will highlight general trends in the strength properties of different soil mixes for CEBs. These efforts are necessary to ensure that GCEB technology becomes more widely accepted in the world of building materials and is considered a reliable option for providing low-cost housing.

  9. Permeability, porosity and compressive strength of self-compacting concrete

    Directory of Open Access Journals (Sweden)

    Valcuende, M.O.

    2005-12-01

    Full Text Available Most deterioration affecting the durability of self-compacting concrete structures is mediated by water penetration in the concrete, a condition related to its porous structure. The present study analyzes these two factors. To this end, two types of concrete were prepared, a self-compacting and a traditional vibrated concrete, with different W/C ratios and different types of cement. The results of low-pressure water testing to evaluate permeability and analyses to determine compressive strength and pore size distribution showed that self-compacting concrete has lower capillary porosity than traditional concrete, which would explain its greater resistance to water penetration. Such concrete likewise reached higher strength values, except where large proportions of lime powder with low sand equivalents were used in its manufacture, when lower strength was recorded. Lastly, the depth of water penetration and compressive strength were found to be linearly correlated. That correlation was seen to depend, in turn, on the type of concrete, since for any given strength level, self-compacting concrete was less permeable than the traditional material.

    En este trabajo experimental se estudia la penetración de agua en hormigones autocompactables, analizando al mismo tiempo su estructura porosa, pues gran parte de los procesos de deterioro que afectan a la durabilidad de las estructuras están condicionados por estos dos aspectos. Para ello se han fabricado dos tipos de hormigones, uno autocompactable y otro tradicional vibrado, con diferentes relaciones A/C y distintos tipos de cemento. Tras determinar la permeabilidad al agua bajo presión, la resistencia a compresión y las distribuciones de tamaño de poro, los resultados obtenidos ponen de manifiesto que los hormigones autocompactables presentan menor porosidad capilar que los tradicionales, lo que les confiere mejores prestaciones frente a la penetración de agua. Asimismo, dichos hormigones alcanzan mayores resistencias, si bien, cuando para su fabricación se emplean grandes cantidades de finos calizos cuyo equivalente de arena es bajo la tendencia se invierte, obteniéndose peores resultados. Por último, se ha establecido una relación de tipo lineal entre la profundidad de penetración de agua y la resistencia a compresión. Dicha relación depende a su vez del tipo de hormigón, dado que los hormigones autocompactables son menos permeables que los tradicionales para una misma resistencia.

  10. Mechanical properties of Concrete with SAP. Part I: Development of compressive strength

    DEFF Research Database (Denmark)

    Hasholt, Marianne Tange; Jespersen, Morten H. Seneka

    2010-01-01

    The development of mechanical properties has been studied in a test program comprising 15 different concrete mixes with 3 different w/c ratios and different additions of superabsorbent polymers (SAP). The degree of hydration is followed for 15 corresponding paste mixes. This paper concerns compressive strength. It shows that results agree well with a model based on the following: 1. Concrete compressive strength is proportional to compressive strength of the paste phase 2. Paste strength depends on gel space ratio, as suggested by Powers 3. The influence of air voids created by SAP on compressive strength can be accounted for in the same way as when taking the air content into account in Bolomeys formula. The implication of the model is that at low w/c ratios (w/c 0.45) and addition of large amounts of SAP, this effect cannot counterbalance the strength reducing effect of increased void volume. In these cases, SAP addition reduces the compressive strength.

  11. Diametral Compressive Strength and Elastic Modulus of Flattened Disc using Diametral Compressive Test

    International Nuclear Information System (INIS)

    The nuclear grade graphite is the candidate materials for the in-core components of the very high temperature gas-cooled tractor (VHTR) due to its very high conductivity, melting temperature, chemical resistance and mechanical stability. Nuclear graphite undergoes dimensional change and mechanical properties change because of irradiation damage. To estimate the irradiation damage, surveillance capsule would be inserted in reactor. Surveillance capsule sizes were limited because it would be located inside of a reactor vessel. Thus, a new test method using small specimen is needed and diametral compressive test is one of them. However, circular anvils are needed according to the specimen size. A flattened disc specimen were proposed to overcome such a problem and applied for determination of mechanical properties for brittle rocks. In this study, the applicability of such specimen was investigated. In addition, minimum specimen size for test was determined and diametral compressive strength of nuclear graphite was measured

  12. Numerical analysis of the spacer grids' compression strength

    Energy Technology Data Exchange (ETDEWEB)

    Schettino, C.F.M.; Gouvea, J.P.; Medeiros, N., E-mail: carlosschettino@inb.gov.br, E-mail: jpg@metal.eeimvr.uff.br [Universidade Federal Fluminense (UFF), Volta Redonda, RJ (Brazil). Programa de Engenharia Metalurgica

    2013-07-01

    Among the components of the fuel assembly, the spacer grids play an important structural role during the energy generation process, mainly for their requirement to have enough structural strength to withstand lateral impact loads, due to fuel assembly shipping/handling and due to forces outcome from postulated accidents (earthquake and LOCA). This requirement ensures a proper geometry for cooling and for guide thimble straightness in the fuel assembly. In this way, the understanding of the macroscopic mechanical behavior of this component becomes essential even to any subsequent geometrical modifications to optimize the flue assemblies' structural behavior. In the present work, three-dimensional finite element models destined to provide consistent predictions of 16X16-type spacer grids lateral strength were proposed. Firstly, buckling tests based on results available in the literature were performed to establish a methodology for spacer grid finite element-based modeling. The, by considering a spacer grid interesting geometry and some possible variations associated to its fabrication, tolerance, the proposed numerical models were submitted to compression conditions to calculate the buckling force. Also, these models were validated for comparison with experimental buckling load results. Comparison of buckling predictions combined to observations of actual and simulated deformed spacer grids geometries permitted to verify the consistency and applicability of the proposed models. Thus, these numerical results show a good agreement between the and the experimental results. (author)

  13. Utilization of the Brazilian test for estimating the uniaxial compressive strength and shear strength parameters

    Scientific Electronic Library Online (English)

    K., Karaman; F., Cihangir; B., Ercikdi; A., Kesimal; S., Demirel.

    2015-03-01

    Full Text Available Uniaxial compressive strength (UCS) and shear strength parameters (cohesion and angle of internal friction, C and ?) of rocks are important parameters needed for various engineering projects such as tunnelling and slope stability. However, direct determination of these parameters is difficult and re [...] quires high-quality core samples for tests. Therefore, this study aimed to explore the applicability of the Brazilian test (BT) - a simple, less sophisticated and inexpensive method for both specimen preparation and testing - to estimate the UCS and shear strength parameters of rocks. Thirty-seven rock types were sampled and tested, 24 of which were volcanic, 8 were metamorphic, and 5 were sedimentary. Statistical equations were derived to estimate the UCS and shear strength parameters of rocks using the BT. The validity of the statistically derived equations was confirmed using predictive analytics software (PASW Statistics 18). A strong linear relation was found between BT and UCS values. BT and UCS values exhibited prominent linear correlations with the cohesion values of rocks. The Mohr envelope was also used to determine the cohesion and friction angle of rocks using BT and UCS values. It is deduced from the current study that the BT values can be used to estimate the UCS and cohesion. However, no relation was observed between the angle of internal friction values and the UCS and BT for all rock types. Therefore, different approaches are suggested for the estimation of the internal angle of friction for application in the preliminary design of projects.

  14. Influence of Cementitious Materials and Aggregates Content on Compressive Strength of Palm Kernel Shell Concrete

    Directory of Open Access Journals (Sweden)

    U.J. Alengaram

    2008-01-01

    Full Text Available This study reports the effect of cementitious materials, fine and coarse aggregates content on workability and compressive strength of palm kernel shell concrete. Palm kernel shells a by product of the production of palm oil, were used as lightweight aggregates. The following cementitious materials were added: 10% silica fume as additional cementitious material and 5% fly ash as cement replacement on weight of cement. The influence of varying fine aggregate and palm kernel shell contents on workability and compressive strength has been studied. The specimens have been cured under three different curing environments to study the effect on compressive strength. The effect of cementitious materials and curing conditions on compressive strength for a period of 90 days was analyzed. The fresh density of concrete was found to be in the range of 1810 to 1940 kg m-3. The strength of Palm Kernel Shells (PKS was found to be the primary factor controlling the strength. However, the addition of silica fume was found to have influence on compressive strength. An increase in fine aggregate content and subsequent decrease in PKS content had positive effect on both workability and compressive strength. The 28 day compressive strengths of the mixes containing cementitious materials were found in the range of 26 to 36 MPa. The difference in strength between water cured and specimens cured under controlled environment was found to vary between 3 and 5%.

  15. Compressibility and strength of nanocrystalline tungsten boride under compression to 60 GPa

    Energy Technology Data Exchange (ETDEWEB)

    Dong Haini [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Department of Geosciences, Princeton University, Princeton, New Jersey 08544 (United States); Dorfman, Susannah M.; Duffy, Thomas S. [Department of Geosciences, Princeton University, Princeton, New Jersey 08544 (United States); Chen Ying; Wang Haikuo; Wang Jianghua; He Duanwei [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Qin Jiaqian [Geodynamics Research Center, Ehime University Bunkyo-cho 2-5, Matsuyama 790-8577 (Japan)

    2012-06-15

    The compression behavior and stress state of nanocrystalline tungsten boride (WB) were investigated using radial x-ray diffraction (RXRD) in a diamond-anvil cell under non-hydrostatic compression up to 60.4 GPa. The compression properties and stress state are analyzed using lattice strain theory. Experiments were conducted at beamline X17C of the National Synchrotron Light Source. The radial x-ray diffraction data yield a bulk modulus that is qualitatively consistent with density functional theory calculations and demonstrate that WB is a highly incompressible material. A maximum differential stress, t, of about 14 GPa can be supported by nanocrystalline WB at the highest pressure. This corresponds to about 5% of the shear modulus, G, which is smaller than the values of t/G ({approx}8%-10%) observed for BC{sub 2}N, B{sub 6}O, TiB{sub 2}, and {gamma}-Si{sub 3}N{sub 4} at high pressures. Thus, while WB is highly incompressible, its strength is relatively low at high pressures compared to other hard ceramics.

  16. Strength of thin laminated polyimide/S2 glass under simultaneous face compression and interlaminar shear

    International Nuclear Information System (INIS)

    The experiment was performed to determine the strength of laminated organic insulators loaded simultaneously in face compression and interlaminar shear. Thin disks of polyimide/S2 glass (PS2) laminate were compressed perpendicular to the surface and loaded in face torsion at room temperature and 77 K. The interlaminar shear strength was determined as a function of face pressure

  17. Strength of Kevlar narrow fabrics as influenced by folding and compression in the presence of moisture

    Energy Technology Data Exchange (ETDEWEB)

    Ericksen, R.H.

    1986-08-01

    The tensile strength of dry Kevlar narrow fabrics was investigated as a function of moisture present during folding and compression. Fabric samples were exposed to 96% relative humidity, or soaked in water prior to compression; or moisture was introduced while the samples were compressed. The fabrics exhibited a 10 to 30% tensile strength loss after wet compression relative to data for samples compressed dry. Similar tests on nylon did not show this effect. Warp yarns removed from fabrics compressed with moisture present exhibited nominally the same strength as those obtained from fabrics compressed dry or from uncompressed fabrics. These results are consistent with test data from a parachute that had been exposed to moisture and with packing difficulties encountered under high humidity environments.

  18. Compressive strength, microstructure and hydration products of hybrid alkaline cements

    Scientific Electronic Library Online (English)

    Zahra, Abdollahnejad; Petr, Hlavacek; Sergio, Miraldo; Fernando, Pacheco-Torgal; José Luís Barroso de, Aguiar.

    2014-08-01

    Full Text Available Ordinary Portland cement (OPC) is the dominant binder in the construction industry with a global production that currently reaches a total of 3 Gt per year. As a consequence, the cement industry's contribution to the total worldwide CO2 emissions is of about 7% of the total emissions. Publications o [...] n the field of alkali-activated binders (also termed geopolymers), state that this new material is, potentially, likely to fbecome an alternative to Portland cement. However, recent LCA studies show that the environmental performance of alkali-activated binders depends, to great extent, of their composition. Also, researchers report that these binders can be produced in a more eco-efficient manner if the use of sodium silicate is avoided. This is due to the fact that the referred component is associated to a high carbon footprint. Besides, most alkali-activated cements suffer from severe efflorescence, a reaction originated by the fact that the alkaline and/or soluble silicates that are added during processing cannot be totally consumed. This paper presents experimental results on hybrid alkaline cements. The compressive strength results and the efflorescence observations show that some of the new mixes already exhibit a promising performance.

  19. Effect of raw material ratios on the compressive strength of magnesium potassium phosphate chemically bonded ceramics

    International Nuclear Information System (INIS)

    The compressive strength of magnesium potassium phosphate chemically bonded ceramics is important in biomedical field. In this work, the compressive strength of magnesium potassium phosphate chemically bonded ceramics was investigated with different liquid-to-solid and MgO-to-KH2PO4 ratios. X-ray diffractometer was applied to characterize its phase composition. The microstructure was imaged using a scanning electron microscope. The results showed that the compressive strength of the chemically bonded ceramics increased with the decrease of liquid-to-solid ratio due to the change of the packing density and the crystallinity of hydrated product. However, with the increase of MgO-to-KH2PO4 weight ratio, its compressive strength increased firstly and then decreased. The low compressive strength in lower MgO-to-KH2PO4 ratio might be explained by the existence of the weak phase KH2PO4. However, the low value of compressive strength with the higher MgO-to-KH2PO4 ratio might be caused by lack of the joined phase in the hydrated product. Besides, it has been found that the microstructures were different in these two cases by the scanning electron microscope. Colloidal structure appeared for the samples with lower liquid-to-solid and higher MgO-to-KH2PO4 ratios possibly because of the existence of amorphous hydrated products. The optimization of both liquid-to-solid and MgO-to-KH2PO4 ratios was important to improve the compressive strength of magnesium potassium phosphate chemically bonded ceramics. - Highlights: • High packing density and amorphous hydrated phase improved the compressive strength. • Residual KH2PO4 and poor bonding phase lower the compressive strength. • MPCBC fabricated with optimized parameters had the highest compressive strength

  20. Effect of raw material ratios on the compressive strength of magnesium potassium phosphate chemically bonded ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ai-juan; Yuan, Zhi-long; Zhang, Jiao; Liu, Lin-tao; Li, Jun-ming, E-mail: ajwmxl@163.com; Liu, Zheng, E-mail: zhengliu@xaut.edu.cn

    2013-12-01

    The compressive strength of magnesium potassium phosphate chemically bonded ceramics is important in biomedical field. In this work, the compressive strength of magnesium potassium phosphate chemically bonded ceramics was investigated with different liquid-to-solid and MgO-to-KH{sub 2}PO{sub 4} ratios. X-ray diffractometer was applied to characterize its phase composition. The microstructure was imaged using a scanning electron microscope. The results showed that the compressive strength of the chemically bonded ceramics increased with the decrease of liquid-to-solid ratio due to the change of the packing density and the crystallinity of hydrated product. However, with the increase of MgO-to-KH{sub 2}PO{sub 4} weight ratio, its compressive strength increased firstly and then decreased. The low compressive strength in lower MgO-to-KH{sub 2}PO{sub 4} ratio might be explained by the existence of the weak phase KH{sub 2}PO{sub 4}. However, the low value of compressive strength with the higher MgO-to-KH{sub 2}PO{sub 4} ratio might be caused by lack of the joined phase in the hydrated product. Besides, it has been found that the microstructures were different in these two cases by the scanning electron microscope. Colloidal structure appeared for the samples with lower liquid-to-solid and higher MgO-to-KH{sub 2}PO{sub 4} ratios possibly because of the existence of amorphous hydrated products. The optimization of both liquid-to-solid and MgO-to-KH{sub 2}PO{sub 4} ratios was important to improve the compressive strength of magnesium potassium phosphate chemically bonded ceramics. - Highlights: • High packing density and amorphous hydrated phase improved the compressive strength. • Residual KH{sub 2}PO{sub 4} and poor bonding phase lower the compressive strength. • MPCBC fabricated with optimized parameters had the highest compressive strength.

  1. Filler effect of fine particle sand on the compressive strength of mortar

    Science.gov (United States)

    Jaturapitakkul, Chai; Tangpagasit, Jatuphon; Songmue, Sawang; Kiattikomol, Kraiwood

    2011-04-01

    The river sand, which is a non-pozzolanic material, was ground into 3 different particle sizes. Portland cement type I was replaced by the ground river sands at 10wt%-40wt% of binder to cast mortar. Compressive strengths of mortar were investigated and the filler effect of different fine particles of sand on the compressive strength of mortar was evaluated. The results show that the compressive strength of mortar contributed from the filler effect of smaller particles is higher than that of the coarser ones. The difference in compressive strength of mortar tends to be greater as the difference in ground river sand fineness increases. The results also suggest that ASTM C618 specification is not practically suitable for specifying pozzolan in concrete since the strength activity index of mortar containing ground river sand (high crystalline phase) with 33.8wt% of particles retained on a 45-?m sieve can pass the strength requirement.

  2. Compression Strength of Fir and Beech Wood Modified by Citric Acid

    Directory of Open Access Journals (Sweden)

    Bogoslav Šefc

    2012-03-01

    Full Text Available Previous articles have shown that modification of wood by citric acid (CA improves dimensional stability and resistance of wood against fungi attack. However, chemical modification of wood also modifies its mechanical properties in some way. The compression strength of wood is one of its representative mechanical properties. Modified wood with lower values of compression strength has limited purpose. The intention of this work is to show the effect of wood modification by citric acid on the compression strength of wood. Fir wood (Abies alba Mill. and beech wood (Fagus sylvatica L. were impregnated by citric acid with sodium-dihydrogen-hypophosphite (NaH2PO2 as a catalyst. Part of the impregnated samples together with control samples were cured at the temperature of 140 °C for 10 hours and the remaining samples were cured in microwaves for 35 minutes. The average compression strength parallel to the grain of wood modifi ed by CA, using different regimes of curing, was compared to the strength of unmodifi ed wood. The average compression strength parallel to the grain of wood was retained after modification. In the case of fir wood, the average compression strength was even improved after modification. The results indicate that wood modified by citric acid may be considered for the purposes where compression strength properties are equally important as improved durability and dimensional stability of wood.

  3. Effect of Cellulose-Ibeta Presence in Sawdust on Compressive Strength of Cement Paste

    OpenAIRE

    Abdoullah Namdar,; Fadzil Mat Yahaya

    2014-01-01

    In this paper, enhancement of compressive strength of OPC paste is main objective. 1% and 4% of sawdust powder has been blended to Ordinary Portland Cement (OPC) paste. The compressive strength has been measured on 7, 28, 56 and 90 days. The micro properties of OPC paste has been investigated by using X-ray diffraction (XRD) and Atomic Force Microscopy (AFM). The best quantity for replacement of sawdust is 1%. The mixture of 4% sawdust to OPC paste has also been improved compressive strength ...

  4. Effect of Specimen Shape and Size on the Compressive Strength of Foamed Concrete

    Directory of Open Access Journals (Sweden)

    Sudin M.A.S.

    2014-03-01

    Full Text Available Lightweight concrete, in the form of foamed concrete, is a versatile material that primarily consists of a cement based mortar, mixed with at least 20% volume of air. Its dry density is typically below 1600 kg/m3 with a maximum compressive strength of 15MPa. The ASTM standard provision specifies a correction factor for concrete strength of between 14 and 42Mpa, in order to compensate for a reduced strength, when the aspect height-to-diameter ratio of a specimen is less than 2.0. However, the CEB-FIP provision specifically mentions a ratio of 150mm dia. × 300mm cylinder strength to 150 mm cube strength; though, both provision requirements do not specifically clarify the applicability and/or modification of the correction factors for the compressive strength to lightweight concrete (in this case, foamed concrete. The focus of this work is to study the effect of specimen size and shape on the axial compressive strength of concrete. Specimens of various sizes and shapes were cast with square and circular cross-sections i.e., cubes, prisms, and cylinders. Their compression strength behaviours at 7 and 28 days were investigated. The results indicate that, as the CEB-FIP provision specified, even for foamed concrete, 100mm cubes (l/d = 1.0 produce a comparable compressive strength with 100mm dia. × 200mm cylinders (l/d = 2.0.

  5. Influence of added concrete compressive strength on adhesion to an existing concrete substrate

    OpenAIRE

    Júlio, Eduardo N. B. S.; Branco, Fernando A. B.; Silva, Vítor D.; Lourenço, Jorge F.

    2006-01-01

    An experimental study was performed to evaluate the bond strength between two concrete layers of different ages, considering different mixtures of added concrete, with different strengths. The specimens first had the roughness of the substrate surface increased by sand blasting. Later, the new concrete was added. Afterwards, slant shear tests were performed to quantify the bond strength in shear. These tests indicated that increasing the compressive strength of the added concrete relative to ...

  6. Tension/compression asymmetry in yield and creep strengths of ni-based superalloys

    OpenAIRE

    Tsuno, N; Shimabayashi, S; Kakehi, K; Rae, CMF; Reed, RC

    2008-01-01

    The tension/compression asymmetries of yield and creep strengths of three kinds of single-crystal superalloys-PWA1480, CMSX-4, and TMS-75 - and a DS superalloy, Mar-M247LC, were investigated at intermediate and high temperatures. In PWA1480, tensile yield strength was higher than the compressive strength from 20°C to 750°C From the TEM observation, it was found that the asymmetry of yield strengths is primarily due to the microtwin formation associated with a superlattice extrinsic stacking f...

  7. FACTORS INFLUENCING THE COMPRESSIVE STRENGTH OF FLY ASH-BASED GEOPOLYMER CONCRETE

    Directory of Open Access Journals (Sweden)

    Djwantoro Hardjito

    2004-01-01

    Full Text Available This paper describes the effects of several factors on the properties of fly ash based geopolymer concrete, especially the compressive strength. The test variables included were the age of concrete, curing time, curing temperature, quantity of superplasticizer, the rest period prior to curing, and the water content of the mix. The test results show that the compressive strength of geopolymer concrete does not vary with age, and curing the concrete specimens at higher temperature and longer curing period will result in higher compressive strength. Furthermore, the commercially available Naphthalene-based superplasticizer improves the workability of fresh geopolymer concrete. The start of curing of geopolymer concrete at elevated temperatures can be delayed at least up to 60 minutes without significant effect on the compressive strength. The test data also show that the water content in the concrete mix plays an important role.

  8. Determine the Compressive Strength of Calcium Silicate Bricks by Combined Nondestructive Method

    OpenAIRE

    Jiri Brozovsky

    2014-01-01

    The paper deals with the application of combined nondestructive method for assessment of compressive strength of calcium silicate bricks. In this case, it is a combination of the rebound hammer method and ultrasonic pulse method. Calibration relationships for determining compressive strength of calcium silicate bricks obtained from nondestructive parameter testing for the combined method as well as for the L-type Schmidt rebound hammer and ultrasonic pulse method are quoted here. Calibration ...

  9. Durability and compressive strength of blast furnace slag-based cement grout for special geotechnical applications

    OpenAIRE

    Ortega Álvarez, José Marcos; Pastor Navarro, José Luis; Albaladejo Ruiz, Arturo; Sánchez Martín, Isidro; Climent Llorca, Miguel Ángel

    2014-01-01

    Special foundations, most prominently micropiles and soil anchors, are frequently used in construction today. In Spain, the grout for these special technical applications is generally prepared with portland cement, although the codes and standards in place stipulate only the minimum compressive strength required, with no mention of cement type. Those texts also establish a range of acceptable water:cement ratios. In the present study, durability and compressive strength in cement grout prepar...

  10. Prediction of compressive strength of concrete containing fly ash using data mining techniques

    OpenAIRE

    Martins, Francisco F.; Camões, Aires

    2013-01-01

    The concrete compressive strength is the most used mechanical property in the design of concrete structures. Therefore, the use of rational models to its prediction, to simulate the effects of its different constituents and its properties can play an important role in the achievement of the safety-economy required. Models to forecast the concrete compressive strength have already been presented before by some researchers. However, the comparison of different rational models and the applicatio...

  11. FACTORS INFLUENCING THE COMPRESSIVE STRENGTH OF FLY ASH-BASED GEOPOLYMER CONCRETE

    OpenAIRE

    Djwantoro Hardjito; Steenie E Wallah; Dody M.J. Sumajouw; B.V Rangan

    2004-01-01

    This paper describes the effects of several factors on the properties of fly ash based geopolymer concrete, especially the compressive strength. The test variables included were the age of concrete, curing time, curing temperature, quantity of superplasticizer, the rest period prior to curing, and the water content of the mix. The test results show that the compressive strength of geopolymer concrete does not vary with age, and curing the concrete specimens at higher temperature and longer cu...

  12. Prediction of compressive strength up to 28 days from microstructure of Portland cement

    DEFF Research Database (Denmark)

    Svinning, K.; Høskuldsson, Agnar; Justnes, H.

    2008-01-01

    The influence of the characteristics or the microstructure of Portland cement on compressive strength up to 28 days has been statistically investigated by application of partial least square (PLS) analysis. The main groups of characteristics were mineralogy and superficial microstructure represented by curves from X-ray diffraction analysis and differential thermogravimetric analysis, as well as particle size distributions. PLS gave maximum explained variance in compressive strength at 1, 2, 7 a...

  13. Compressive Strength and Setting Time of MTA and Portland Cement Associated with Different Radiopacifying Agents

    OpenAIRE

    TANOMARU-FILHO, Mario; Morales, Vanessa; da Silva, Guilherme F.; Bosso, Roberta; Reis, José M. S. N.; Duarte, Marco A. H.; Guerreiro-Tanomaru, Juliane M.

    2012-01-01

    Objective. The aim of this study was to evaluate the compressive strength and setting time of MTA and Portland cement (PC) associated with bismuth oxide (BO), zirconium oxide (ZO), calcium tungstate (CT), and strontium carbonate (SC). Methods. For the compressive strength test, specimens were evaluated in an EMIC DL 2000 apparatus at 0.5?mm/min speed. For evaluation of setting time, each material was analyzed using Gilmore-type needles. The statistical analysis was performed with ANOVA and th...

  14. Effect of compressive loads on the tensile strength of concrete at high strain rates

    OpenAIRE

    Tinic, C.; Brühwiler, E.

    1985-01-01

    This paper describes the behaviour of concrete subjected to tensile loads at high strain rates with and without compressive load histories. The tests, carried out at the laboratory of building materials of the Swiss Federal Institute of Technology, Zurich, show a considerable deterioration of the tensile strength due to initially applied compressive loads.

  15. Compression strength of a fibre composite main spar in a wind turbine blade

    Energy Technology Data Exchange (ETDEWEB)

    Moelholt Jensen, F.

    2003-06-01

    In this report the strength of a wind turbine blade is found and compared with a full-scale test, made in the same project. Especially the post buckling behaviour of the compression flange is studied. Different compressive failure mechanisms are discussed and the limitations in using the Finite Element Method. A suggestion to the further work is made. (au)

  16. Compression strength of a fibre composite main spar in a wind turbine blade

    DEFF Research Database (Denmark)

    Jensen, Find Mølholt

    2003-01-01

    In this report the strength of a wind turbine blade is found and compared with a full-scale test, made in the same project. Especially the postbuckling behaviour of the compression flange is studied. Different compressive failure mechanisms are discussedand the limitations in using the Finite Element Method. A suggestion to the further work is made.

  17. Non-Uniform Compressive Strength of Debonded Sandwich Panels

    DEFF Research Database (Denmark)

    Nøkkentved, Alexandros; Lundsgaard-Larsen, Christian; Berggreen, Carl Christian

    2005-01-01

    Face/core debond-damaged sandwich panels exposed to non-uniform compression loads are studied. The panel geometry is rectangular with a centrally located circular debond. The study primarily includes experimental methods, but simple finite element calculations are also applied. The complexity of applying a controlled non-uniform compressive load to the test panels requires a strong focus on the development of a suitable testrig. This is done by the extensive use of product development methods. T...

  18. Fracture Energy of High-Strength Concrete in Compression

    DEFF Research Database (Denmark)

    Dahl, H.; Brincker, Rune

    1989-01-01

    Compression tests are usually carried out in load control. This implies the termination of the test at the peak point of the load-displacement curve, while the fracture under these conditions becomes unstable at the descending branch of the load displacement relation. However, the descending branch is essential for understanding the fracture mechanism of concrete in compression. In this paper a series of tests is reported, carried out for the purpose of studying the fracture mechanical propertie...

  19. Fracture Energy of High-Strength Concrete in Compression

    OpenAIRE

    Dahl, H.; Brincker, Rune

    1989-01-01

    Compression tests are usually carried out in load control. This implies the termination of the test at the peak point of the load-displacement curve, while the fracture under these conditions becomes unstable at the descending branch of the load displacement relation. However, the descending branch is essential for understanding the fracture mechanism of concrete in compression. In this paper a series of tests is reported, carried out for the purpose of studying the fracture mechanical proper...

  20. Compression specific toughness of normal strength steel fiber reinforced concrete (NSSFRC) and high strength steel fiber reinforced concrete (HSSFRC)

    Scientific Electronic Library Online (English)

    Khaled, Marara; Özgür, Erenb; & #304; brahim, Yitmena.

    Full Text Available Compression toughness tests were carried out on concrete cylinders reinforced with three different aspect ratios of hooked-end steel fibers 60, 75, and 83 and six different percentages of steel fibers 0.5, 1.0, 1.25, 1.5, 1.75, and 2.0% by volume of concrete. The w/c ratio used for the normal streng [...] th steel fiber reinforced concrete mixes (NSSFRC) was 0.55, and the water-cementitious ratio (w/c+s) for the high strength fiber reinforced concrete mixes (HSSFRC) was 0.31. For each mix, three test cylinders were tested for compression specific toughness. The effect of fiber reinforcement index: volume of fibers × length/diameter ratio on compression specific toughness and also on the relationship between these two properties is presented in this paper. As a result, (a) equations are proposed to quantify the effect of fibers on compression toughness ratio of concrete in terms of FRI, (b) equations obtained in terms of FRI and compression specific toughness of plain concrete to estimate both compression specific toughness of NSSFRC and HSSFRC (N.m), (c) equations obtained which represent the relationship between compression toughness index and FRI for NSSFRC and HSSFRC, respectively, and (d) equations obtained to quantify the relationship between compression specific toughness index and fiber reinforcement index for NSSFRC and HSSFRC, respectively. The proposed equations give good correlation with the experimental values.

  1. Influence of the real density and structure imperfection of hollow glass microspheres on the compression strength

    International Nuclear Information System (INIS)

    Highlights: ? A new formula for calculating the compression strength of hollow glass microspheres was proposed. ? Chemical composition of HGM was analyzed. ? Imperfect structure was characterized by optical microscope. ? Structure defects were characterized by SEM after heat treating at 700 deg. C. ? Strength of samples with same structure coefficient increases with real density. - Abstract: In this paper, we simplified the factors that affect the compression strength of hollow glass microspheres theoretically. When the chemical composition of the hollow glass microspheres was determined, the real density was the only variable to decide the strength. We calculated the theoretical strength of sample - T, Tg1, Tg2, S, A and R according to their chemical composition and real density. The real strength of the hollow glass microspheres was much lower than the theoretical strength actually due to the structure imperfection. The structure defect was characterized by optical microscope and scanning electron microscope (samples for scanning electron microscope have been treated under 700 deg. C). The real strength 'Pr' should be decided by the theoretical strength 'P' multipied by a structure coefficient '?', which is related to the preparation technology closely. The sample-T was graded in grain size with a water separator to get samples with the same structure coefficient but varied in real density. The results of compression test proved that the strength increased with the real density.

  2. Laboratory Investigation on Performance of Cement Using Different Additives Schemes to Improve Early Age Compressive Strength

    Directory of Open Access Journals (Sweden)

    Muhannad Talib Shuker

    2014-03-01

    Full Text Available It is essential to maintain the oil well cement integrity effectively and economically. The classical literature review of cement slurry preparation has shown high temperature in wellbore has influenced the mechanical properties of cement slurry, especially compressive strength. The compressive strength is the most important parameter when the ability of the cement to perform its necessary functions of down-hole faster placement analyzed. In past, the different additives were used to improve the performance of cement slurry by maintain compressive strength during placement. Laboratory tests carry out by Silica Fume (SF with dispersants and fluid loss control additives at different concentrations to performed early age compressive test of nondestructive cement slurry through Ultra-Sonic Cement Analyzer (UCA. Measured result showed that 6:34 and 7:48 h aged sample have a maximum compressive strength at temperature above 120°C. It is observed that as concentration of SF increased with combined dispersants and fluid loss additives used to control& enhance compressive strength at above 120°C for the integrity of cement slurry.

  3. Variations in Compressive Strength of Geopolymer due to the CaO Added Fly Ash

    Science.gov (United States)

    Zhao, Yuqing; Koumoto, Tatsuya; Kondo, Fumiyoshi

    Recently, geopolymer has been a noteworthy material which can be used as a replacement for portland cement. The mechanical characteristics and consistency of the geopolymer are strongly affected by its chemical components of fly ash. The variations in compressive strength of geopolymer due to the CaO added fly ash were investigated in this paper. The compressive strengths of geopolymer were increased with an increase in the curing period, and the characteristics changed from the one of plastic soil material to brittle material such as concrete, regardless of CaO content. Also, the results of compressive strength and modulus of deformation showed their maximum value in the case of 8-10% CaO content. From this result, the maximum characteristics of the strengths were assumed to be exerted in case which the water draining process of geopolymer was balanced with the water absorbing process of additional CaO.

  4. THE DENSITY, COMPRESSION STRENGTH AND SURFACE HARDNESS OF HEAT TREATED HORNBEAM (Carpinus betulus L. WOOD

    Directory of Open Access Journals (Sweden)

    Gokhan Gunduz

    2009-01-01

    Full Text Available The heat treatment of wood is an environment-friendly method for wood preservation. The heat treatment process only uses steam and heat, and no chemicals or agents are applied to the material during the process. Tests have shown no harmful emissions are apparent when working with the material. This process improves wood’s resistance to decay and its dimensional stability. In this study, the density, compression strength and hardness of heat treated hornbeam (Carpinus betulus L. wood were investigated. Wood specimens that had been conditioned at 65% relative humidity and 20ºC were subjected to heat treatment at 170, 190, and 210 °C for 4, 8, and 12 hrs. After heat treatment, compression strength and hardness were determined according to TS 2595 and TS 2479. The results showed that the decreases of compression strength and hardness were related to the extent of density loss. Both compression strength and hardness decreased with the increasing temperatures and durations of the heat treatment. While the maximum density loss observed was 16.12% at 210 ºC and 12 hour, at these heat-treatment conditions, the compression strength approximately decreased 30% and hardness values in tangential, radial, and longitudinal directions approximately decreased by 55%, 54%, and 38%, respectively. Hence, it was concluded that there might be a relationship between changes of these wood properties.

  5. THE DENSITY, COMPRESSION STRENGTH AND SURFACE HARDNESS OF HEAT TREATED HORNBEAM (Carpinus betulus L.) WOOD

    Scientific Electronic Library Online (English)

    Gokhan, Gunduz; Suleyman, Korkut; Deniz, Aydemir; Ilter, Bekar.

    Full Text Available The heat treatment of wood is an environment-friendly method for wood preservation. The heat treatment process only uses steam and heat, and no chemicals or agents are applied to the material during the process. Tests have shown no harmful emissions are apparent when working with the material. This [...] process improves wood’s resistance to decay and its dimensional stability. In this study, the density, compression strength and hardness of heat treated hornbeam (Carpinus betulus L.) wood were investigated. Wood specimens that had been conditioned at 65% relative humidity and 20ºC were subjected to heat treatment at 170, 190, and 210 °C for 4, 8, and 12 hrs. After heat treatment, compression strength and hardness were determined according to TS 2595 and TS 2479. The results showed that the decreases of compression strength and hardness were related to the extent of density loss. Both compression strength and hardness decreased with the increasing temperatures and durations of the heat treatment. While the maximum density loss observed was 16.12% at 210 ºC and 12 hour, at these heat-treatment conditions, the compression strength approximately decreased 30% and hardness values in tangential, radial, and longitudinal directions approximately decreased by 55%, 54%, and 38%, respectively. Hence, it was concluded that there might be a relationship between changes of these wood properties.

  6. Effect of activator solution on compressive strength of flyash geopolymer blended with slag

    Directory of Open Access Journals (Sweden)

    Debabrata Dutta

    2014-12-01

    Full Text Available The influence of the composition of activator solution on the strength of fly ash geopolymer blended with slag was investigated. The research variable include % Na2O and sodium silicate under typical controlled parameters like curing profile, water content, base material and supplementary material. In this study, the monitoring response variable was compressive strength. Finding suggests that activator solution combination has a significant effect on the properties of the GP (non-blended geopolymer and GB (geopolymer blended with 15% slag. The experiment concludes that higher percentage of Na2O gives lower strength for GB specimens but corresponding higher strength for GP specimens. Silicate modulus has similar impact on GP and GB. Both for GP and GB specimens compressive strength is increase with higher silicate modulus.

  7. Compressive strength, flexural strength and thermal conductivity of autoclaved concrete block made using bottom ash as cement replacement materials

    International Nuclear Information System (INIS)

    Highlights: ? Autoclaved aerated concrete were produced using coal bottom ash as a cement replacement material. ? Coal bottom ash was found to enhance concrete strengths. ? Thermal conductivity of concrete was not significantly affected. ? X-ray diffraction and thermal analysis show tobermorite formation. -- Abstract: The bottom ash (BA) from Mae Moh power plant, Lampang, Thailand was used as Portland cement replacement to produce lightweight concrete (LWC) by autoclave aerated concrete method. Portland cement type 1, river sand, bottom ash, aluminium powder and calcium hydroxide (Ca(OH)2) were used in this study. BA was used to replace Portland cement at 0%, 10%, 20% and 30% by weight and aluminium powder was added at 0.2% by weight in order to produce the aerated concrete. Compressive strength, flexural and thermal conductivity tests were then carried out after the concrete were autoclaved for 6 h and left in air for 7 days. The results show that the compressive strength, flexural strength and thermal conductivity increased with increased BA content due to tobermorite formation. However, approximately, 20% increase in both compressive (up to 11.61 MPa) and flexural strengths (up to 3.16 MPa) was found for mixes with 30% BA content in comparison to just around 6% increase in the thermal conductivity. Thermogravimetry analysis shows C–S–H formation and X-ray diffraction confirm tobermorite formation in bottom ash lightweight concrete. The use of BA as a cement replacement, therefore, can be seen to have the benefit in enhancing strength of the aerated concrete while achieving comparatively low thermal conductivity when compared to the results of the control Portland cement concrete.

  8. Compression specific toughness of normal strength steel fiber reinforced concrete (NSSFRC) and high strength steel fiber reinforced concrete (HSSFRC)

    OpenAIRE

    Khaled Marara; Özgür Erenb; ?brahim Yitmena

    2011-01-01

    Compression toughness tests were carried out on concrete cylinders reinforced with three different aspect ratios of hooked-end steel fibers 60, 75, and 83 and six different percentages of steel fibers 0.5, 1.0, 1.25, 1.5, 1.75, and 2.0% by volume of concrete. The w/c ratio used for the normal strength steel fiber reinforced concrete mixes (NSSFRC) was 0.55, and the water-cementitious ratio (w/c+s) for the high strength fiber reinforced concrete mixes (HSSFRC) was 0.31. For each mix, three tes...

  9. Improved compressive strength ordered polymer fibers via radiation-induced cross-linking

    International Nuclear Information System (INIS)

    Radiation cross-linking was successfully applied to increase the compressive strength of ordered polymer fibers. PBO, PBO/IP-600, methyl-PBZT and dimethyl-PBZT fibers were irradiated with proton, electron and gamma rays at varying doses. The compressive strength of PBO fiber was doubled by proton irradiation and dimethyl-PBZT fiber was improved more than 50 percent by electron irradiation. PBO/IP-600 and methyl-PBZT fibers were not noticeably improved by irradiation. Fiber swelling studies at M.I.T. confirmed the cross-linking mechanism for protons and electrons, but not gamma rays. The results of efforts to improve the compressive strength of ordered polymer fibers are discussed

  10. Statistical approach to predict compressive strength of high workability slag-cement mortars

    International Nuclear Information System (INIS)

    This paper reports an attempt made to develop empirical expressions to estimate/ predict the compressive strength of high workability slag-cement mortars. Experimental data of 54 mix mortars were used. The mortars were prepared with slag as cement replacement of the order of 0, 50 and 60%. The flow (workability) was maintained at 136+-3%. The numerical and statistical analysis was performed by using database computer software Microsoft Office Excel 2003. Three empirical mathematical models were developed to estimate/predict 28 days compressive strength of high workability slag cement-mortars with 0, 50 and 60% slag which predict the values accurate between 97 and 98%. Finally a generalized empirical mathematical model was proposed which can predict 28 days compressive strength of high workability mortars up to degree of accuracy 95%. (author)

  11. A Study of Compressive Strength Characteristics of Laterite Sand Hollow Blocks

    Directory of Open Access Journals (Sweden)

    Abiodun Olanipekun

    2007-01-01

    Full Text Available This paper presents the results of experimental investigations carried out on partial replacement of sand with laterite as it affects the compressive strength of sandcrete hollow blocks. Two mix proportions (1:6 and 1:8 were used with laterite content varying between 0 and 50% at 10% intervals. Hand and machine compaction methods were used. Curing was done by sprinkling water on the specimens. The results showed that for each mix proportion and compaction method, the compressive strength decreases with increase in laterite content. Machine compacted hollow sandcrete blocks made from mix ratio 1:6 and with up to 10% laterite content is found suitable and hence recommended for building construction having attained a 28-day compressive strength of 2.07N/mm2 as required by the Nigerian Standards.

  12. Effects of densified silica fume on microstructure and compressive strength of blended cement pastes

    International Nuclear Information System (INIS)

    Some experimental investigations on the microstructure and compressive strength development of silica fume blended cement pastes are presented in this paper. The silica fume replacement varies from 0% to 20% by weight and the water/binder ratio (w/b) is 0.4. The pore structure by mercury intrusion porosimetry (MIP), the micromorphology by scanning electron microscopy (SEM) and the compressive strength at 3, 7, 14, 28, 56 and 90 days have been studied. The test results indicate that the improvements on both microstructure and mechanical properties of hardened cement pastes by silica fume replacement are not effective due to the agglomeration of silica fume particles. The unreacted silica fume remained in cement pastes, the threshold diameter was not reduced and the increase in compressive strength was insignificant up to 28 days. It is suggested that the proper measures should be taken to disperse silica fume agglomeration to make it more effective on improving the properties of materials

  13. Non-Uniform Compressive Strength of Debonded Sandwich Panels

    DEFF Research Database (Denmark)

    Berggreen, Carl Christian; Simonsen, Bo Cerup

    2005-01-01

    This article describes the development, validation and application of a FEM based numerical model for prediction of residual strength of damaged sandwich panels. The core of the theoretical method is a newly developed procedure for prediction of the propagation of a face-core debond. As demonstrated, the method can predict the maximum load carrying capacity of real-life panels with debond damages, where the failure is governed by face-sheet buckling followed by debond growth. The developed theor...

  14. The Study of Green Compression Strength of a Green Sand Mould Using Statistical Approach

    OpenAIRE

    Aondona Paul Ihom; Aniekan Offiong

    2014-01-01

    The study of green compression strength of a green sand mould using statistical approach has been undertaken. Empirically generated data in National Metallurgical Development Centre, Jos Sand Testing Laboratory were used for the study. Coefficient of correlation, coefficients of determination and coefficient of multiple determinations were used to explain the relationship existing between the two independent variables of clay and moisture content and green compression streng...

  15. Dynamic compressive and tensile strengths of spark plasma sintered alumina

    Energy Technology Data Exchange (ETDEWEB)

    Girlitsky, I.; Zaretsky, E. [Department of Mechanical Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105 (Israel); Kalabukhov, S.; Dariel, M. P.; Frage, N. [Department of Materials Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105 (Israel)

    2014-06-28

    Fully dense submicron grain size alumina samples were manufactured from alumina nano-powder using Spark Plasma Sintering and tested in two kinds of VISAR-instrumented planar impact tests. In the first kind, samples were loaded by 1-mm tungsten impactors, accelerated to a velocity of about 1?km/s. These tests were aimed at studying the Hugoniot elastic limit (HEL) of Spark Plasma Sintering (SPS)-processed alumina and the decay, with propagation distance, of the elastic precursor wave. In the tests of the second kind, alumina samples of 3-mm thickness were loaded by 1-mm copper impactors accelerated to 100–1000?m/s. These tests were aimed at studying the dynamic tensile (spall) strength of the alumina specimens. The tensile fracture of the un-alloyed alumina shows a monotonic decline of the spall strength with the amplitude of the loading stress pulse. Analysis of the decay of the elastic precursor wave allowed determining the rate of the irreversible (inelastic) strains in the SPS-processed alumina at the initial stages of the shock-induced inelastic deformation and to clarify the mechanisms responsible for the deformation. The 1-% addition of Cr{sub 2}O{sub 3} decreases the HEL of the SPS-processed alumina by 5-% and its spall strength by 50% but barely affects its static properties.

  16. Compressive strength and microstructural analysis of fly ash/palm oil fuel ash based geopolymer mortar

    International Nuclear Information System (INIS)

    Highlights: • Results show POFA is adaptable as replacement in FA based geopolymer mortar. • The increase in POFA/FA ratio delay of the compressive development of geopolymer. • The density of POFA based geoploymer is lower than FA based geopolymer mortar. - Abstract: This paper presents the effects and adaptability of palm oil fuel ash (POFA) as a replacement material in fly ash (FA) based geopolymer mortar from the aspect of microstructural and compressive strength. The geopolymers developed were synthesized with a combination of sodium hydroxide and sodium silicate as activator and POFA and FA as high silica–alumina resources. The development of compressive strength of POFA/FA based geopolymers was investigated using X-ray florescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and field emission scanning electron microscopy (FESEM). It was observed that the particle shapes and surface area of POFA and FA as well as chemical composition affects the density and compressive strength of the mortars. The increment in the percentages of POFA increased the silica/alumina (SiO2/Al2O3) ratio and that resulted in reduction of the early compressive strength of the geopolymer and delayed the geopolymerization process

  17. The Comparison of the Film Thickness and Compressive Strength Between Ariadent and Harvard Zinc Phosphate Cement.

    Directory of Open Access Journals (Sweden)

    M - Sabouhi

    2005-01-01

    Full Text Available Introduction. Recently, the Ariadent Zinc phosphate cement has been introduced to market with low cost. Some dentists purchase this product because of low cost and others avoid buying it because of unreliable quality. The two important properties of ideal dental cement are to have the minimum film thickness (less than 25 micron and to have favorable compressive strength. The purpose of this study was to determine the mean and to compare the film thickness and compressive strength of Ariadent and Harvard Zinc phosphate cement.Materials and Methods. In this experimental study evaluation was made based on Iranian standard number 2725. To measure film thickness of each cement, the first step was to prepare two glass slabs and their thickness was measured with micrometer, then each cement was prepared according to standard procedure and was put between the glass slabs. The difference between glass slabs with and without cement was measured. This procedure was repeated 3 times and average of three measurements were obtained and determined as mean of cement film thickness. To determine the compressive strength of each cement at first a mold was fabricated according to standard procedures. Then each prepared cement was poured in to the mold. After 24 hours each of five prepared specimens was Put under load and the average compressive strength was calculated.Results. The mean film thickness for Arident Zinc phosphate was 42.33?4.50 micron and for Harvard cement was 24.33?5.70. The mean compressive strength of Ariadent Zinc phosphate cement was 44.90?4.11 MPa and for Harvard cement was 62.85?5.19 MPa. The statistical analysis (t-student revealed significant difference between two phosphate cement.Discussion. In this study mean film thickness of Iranian Ariadent Zinc phosphate cement was more than standard level (25 micron and the mean compressive strength was less than standard level (70 MPa. These results indicated that Ariadent cement was of low quality and below standard. But Harvard Zinc phosphate cement had a standard film thickness and its compressive strength was close to standard and this is a reason for acceptable quality of Harvard Zinc phosphate cement.Keywords. Cement, Compressive strength, film thickness, Zinc phosphate cement

  18. The statitistical evaluation of the uniaxial compressive strength of the Ruskov andesite

    Directory of Open Access Journals (Sweden)

    Krepelka František

    2002-03-01

    Full Text Available The selection of a suitable model of the statistical distribution of the uniaxial compressive strength is discussed in the paper. The uniaxial compressive strength was studied on 180 specimens of the Ruskov andesite. The rate of loading was 1MPa.s-1. The experimental specimens had a prismatic form with a square base; the slightness ratio of specimens was 2:1. Three sets of specimens with a different length of the base edge were studied, namely 50, 30 and 10 mm. The result of the measurement were three sets with 60 values of the uniaxial compressive strength. The basic statistical parameters: the sample mean, the sample standard deviation, the variational interval, the minimum and maximum value, the sample obliqueness coefficient and the sharpness coefficient were evaluated for each collection. Two types of the distribution which can be joined with the real physical fundamentals of the desintegration of rocks ( the normal and the Weibull distribution were tested. The two-parametric Weibull distribution was tested. The basic characteristics of both distributions were evaluated for each set and the accordance of the model distribution with an experimental distribution was tested. The ÷2-test was used for testing. The two-parametric Weibull distribution was selected following the comparison of the test results of both model distributions as a suitable distribution model for the characterization of uniaxial compressive strength of the Ruskov andesite. The two-parametric Weibull distribution showed better results of the goodness-of-fit test. The normal distribution was suitable for two sets; one of the sets showed a negative result of the goodness-of-fit testing. At the uniaxial compressive strength of the Ruskov andesite, a scale effect was registered : the mean value of uniaxial compressive strength decreases with increasing the specimen base edge. This is another argument for using the Weibull distribution as a suitable statistical model of the uniaxial compressive strength distribution. The Weibull distribution unlike the normal distribution enables the physical interpretation of the scale effect influence on uniaxial compressive strength value.

  19. Prediction of potential compressive strength of Portland clinker from its mineralogy

    DEFF Research Database (Denmark)

    Svinning, K.; Høskuldsson, Agnar; Justnes, H.

    2010-01-01

    Based on a statistical model first applied for prediction of compressive strength up to 28 d from the microstructure of Portland cement, potential compressive strength of clinker has been predicted from its mineralogy. The prediction model was evaluated by partial least squares regression. The mineralogy was described by patterns from X-ray diffraction analysis in the 20-regions 29.88-30.70 degrees and 32.90-34.10 degrees (using CuK alpha-radiation). It has been shown that prediction of potentia...

  20. The chemical composition and compression strengths of refractory ceramics, tested for 3 curing temperatures

    International Nuclear Information System (INIS)

    An investigation was carried out to determine and compile the mechanical strength of a refractory ceramic made of ground fire bricks and refractory fire mortar. Three different compositions were studied for the compression strength and it was found that the composition with 50% fire bricks and 50% fire mortar gives the best mechanical strength. With this composition the maximum failure compression stress is 3.2 MPa. and the Young Modulus is 403.5 MPa. The investigation also shows that the curing temperatures and the composition percentages play an important role in determining the strength of the ceramic. The trend obtained from the investigation shows that there is the possibility that an optimum value of composition percentage exist

  1. Effect of additives on the compressive strength and setting time of a Portland cement

    Directory of Open Access Journals (Sweden)

    Desirée Freitas Mryczka Machado

    2010-06-01

    Full Text Available Improvements in strength and setting time of Portland cements (PC are needed to enhance their performance as endodontic and load bearing materials. This study sought to enhance the compressive strength and setting time of a PC by adding one of the following additives: 20% and 30% poly-methylmethacrylate (PMMA, 20% and 30% irregular and spherical amalgam alloys, and 10% CaCl2. The control consisted of unreinforced PC specimens. Setting time was determined using a Gillmore apparatus according to standardized methods while compressive strength was measured using a universal testing machine after 21 hours or 60 days of water storage. Data were analyzed by ANOVA, Tukey and Games-Howell tests (? = 5%. All additives significantly decreased both initial and final setting times as compared with the PC-control (p < .05. 30% PMMA and 30% irregular alloy had the lowest values of initial setting time. 30% irregular alloy also produced the lowest values of final setting time while 30% spherical alloy yielded the highest (p < .05. No differences were detected between the compressive strength values of 21 hours and 60 days. While 10% CaCl2, 20% and 30% PMMA produced values significantly lower than the PC-control, 30% spherical alloy significantly improved the compressive strength of the reinforced PC (p < .05. In summary, all additives significantly reduced the setting time and 30% spherical amalgam alloy yielded a significant increase in compressive strength for the tested PC, which might represent an improved composition for PCs to expand their use as endodontic and potentially load bearing materials.

  2. Effect of Cement Stabilized Kaolin Subgrade on Strength Properties

    OpenAIRE

    Nur Akmal Abd Karim; Ahmad Safuan A Rashid; Norhazilan Md. Noor; Haryati Yaacob

    2014-01-01

    Subgrade performance generally depends on the load bearing capacity of soil. This load is often affected by degree of compaction, moisture content and soil type. Poor subgrade should be avoided by removal, replace and add stabilizer agent to provide a suitable strength for subgrade. This study presents the effect of cement stabilizer on California Bearing Ratio (CBR) and Unconfined Compressive Strength (UCS) for kaolin clay in low traffic volume road. The test conducted includes determination...

  3. Effect of different dispersants in compressive strength of carbon fiber cementitious composites

    Science.gov (United States)

    Lestari, Yulinda; Bahri, Saiful; Sugiarti, Eni; Ramadhan, Gilang; Akbar, Ari Yustisia; Martides, Erie; Khaerudini, Deni S.

    2013-09-01

    Carbon Fiber Cementitious Composites (CFCC) is one of the most important materials in smart concrete applications. CFCC should be able to have the piezoresistivity properties where its resistivity changes when there is applied a stress/strain. It must also have the compressive strength qualification. One of the important additives in carbon fiber cementitious composites is dispersant. Dispersion of carbon fiber is one of the key problems in fabricating piezoresistive carbon fiber cementitious composites. In this research, the uses of dispersants are methylcellulose, mixture of defoamer and methylcellulose and superplasticizer based polycarboxylate. The preparation of composite samples is similar as in the mortar technique according to the ASTM C 109/109M standard. The additives material are PAN type carbon fibers, methylcellulose, defoamer and superplasticizer (as water reducer and dispersant). The experimental testing conducts the compressive strength and resistivity at various curing time, i.e. 3, 7 and 28 days. The results obtained that the highest compressive strength value in is for the mortar using superplasticizer based polycarboxylate dispersant. This also shown that the distribution of carbon fiber with superplasticizer is more effective, since not reacting with the cementitious material which was different from the methylcellulose that creates the cement hydration reaction. The research also found that the CFCC require the proper water cement ratio otherwise the compressive strength becomes lower.

  4. Effects of CuO nanoparticles on compressive strength of self-compacting concrete

    Indian Academy of Sciences (India)

    Ali Nazari; Shadi Riahi

    2011-06-01

    In the present study, the compressive strength, thermal properties and microstructure of self-compacting concrete with different amounts of CuO nanoparticles have been investigated. CuO nanoparticles with an average particle size of 15 nm were added to self-compacting concrete and various properties of the specimens were measured. The results indicate that CuO nanoparticles are able to improve the compressive strength of self-compacting concrete and reverse the negative effects of superplasticizer on compressive strength of the specimens. CuO nanoparticles as a partial replacement of cement up to 4 wt.% could accelerate C–S–H gel formation as a result of the increased crystalline Ca(OH)2 amount at the early ages of hydration. Increasing CuO nanoparticle content to more than 4 wt.%, causes reduced compressive strength because of unsuitable dispersion of nanoparticles in the concrete matrix. Accelerated peak appearance in conduction calorimetry tests, more weight loss in thermogravimetric analysis and more rapid appearance of peaks related to hydrated products in X-ray diffraction results, all indicate that CuO nanoparticles up to 4 wt.% could improve the mechanical and physical properties of the specimens. Finally, CuO nanoparticles improved the pore structure of concrete and caused shifting of the distributed pores from harmless to low harm.

  5. The Effect of Blood Contamination on the Compressive Strength of Calcium-Enriched Mixture

    Directory of Open Access Journals (Sweden)

    Alireza Adl

    2015-03-01

    Full Text Available Statement of the Problem: In clinical situations, Calcium-Enriched Mixture (CEM comes into direct contact or even mixes with blood during or after placement. Purpose: The aim of this study was to evaluate the effect of blood contamination on the compressive strength of CEM. Materials and Method: Three experimental groups were included in this study. In the first group, CEM was mixed with distilled water and was exposed to normal saline (control group. In the second group, CEM cement was mixed with distilled water and then was exposed to blood. In the third group, CEM was mixed with and exposed to blood. Nine custom-made two-part split Plexiglas molds with five holes were used to form CEM samples for compressive strength testing (15 samples in each group. After 7 days of incubation, compressive bond strength testing was performed using a universal testing machine. Data were statistically analyzed using the Mann–Whitney U test with a significance level of p 0.05. Conclusion: It can be concluded that exposure to blood does not adversely affect the compressive strength of CEM, but incorporation of blood makes the cement very brittle.

  6. Prediction of Corrosion Resistance of Concrete Containing Natural Pozzolan from Compressive Strength

    Science.gov (United States)

    al-Swaidani, A. M.; Ismat, R.; Diyab, M. E.; Aliyan, S. D.

    2015-11-01

    A lot of Reinforced Concrete (RC) structures in Syria have suffered from reinforcement corrosion which shortened significantly their service lives. Probably, one of the most effective approaches to make concrete structures more durable and concrete industry on the whole - more sustainable is to substitute pozzolan for a portion of Portland cement (PC). Syria is relatively rich in natural pozzolan. In the study, in order to predict the corrosion resistance from compressive strength, concrete specimens were produced with seven cement types: one plain Portland cement (control) and six natural pozzolan-based cements with replacement levels ranging from 10 to 35%. The development of the compressive strengths of concrete cube specimens with curing time has been investigated. Chloride penetrability has also been evaluated for all concrete mixes after three curing times of 7, 28 and 90 days. The effect on resistance of concrete against damage caused by corrosion of the embedded reinforcing steel has been investigated using an accelerated corrosion test by impressing a constant anodic potential for 7, 28 and 90 days curing. Test results have been statistically analysed and correlation equations relating compressive strength and corrosion performance have been developed. Significant correlations have been noted between the compressive strength and both rapid chloride penetrability and corrosion initiation times. So, this prediction could be reliable in concrete mix design when using natural pozzolan as cement replacement.

  7. Compressive strength of different brands of cement (OPC) in province of Sindh

    International Nuclear Information System (INIS)

    OPC (Ordinary Portland Cement) is the most common type of cement used in construction industry. Three major brands of OPC are normal OPC, SRC (Sulphate Resisting Cement) and SC (Slag Cement). It is seen that the variation in constituents of cement may cause serious effects on the quality of cement. Thus the motivation of this research is to study the basic properties (consistency, setting time, and fineness), compressive strength (cement mortar and concrete cubes) and modulus of elasticity of all the OPC brands (OPC, SRC and SC) manufactured in Sindh. In total 10 cement factories, altogether 21 different brands of cement, were studied in the light of BS and ASTM Code specifications. In total 126 mortar cubes (1:3), 252 concrete cubes (126 for 3000 psi mix design and remaining for 5000 psi) and 126 concrete cylinders (6 for the each brand of cement pertaining to 3000 psi and 5000 psi mix design) were manufactured and tested. Experimental results demonstrated that all the cement brands fulfilled the BS and ASTM Code requirements for (i) basic properties (ii) compressive strength of mortar cubes at 3 and 28 days curing age (iii) compressive strength of concrete cubes at 28 days curing age, and (iv) modulus of elasticity. Some of the cements did not fulfill the BS and ASTM Code requirements for compressive strength of concrete cubes at 7 days curing age. (author)

  8. Non-Uniform Compressive Strength of Debonded Sandwich Panels : I. Experimental Investigation

    DEFF Research Database (Denmark)

    NØkkentved, Alexandros; Lundsgaard-Larsen, Christian

    2005-01-01

    Face/core debond-damaged sandwich panels exposed to non-uniform compression loads are studied. The panel geometry is rectangular with a centrally located circular debond. The study primarily includes experimental methods, but simple finite element calculations are also applied. The complexity of applying a controlled non-uniform compressive load to the test panels requires a strong focus on the development of a suitable testrig. This is done by the extensive use of product development methods. The experimental results based on full-scale testing of 10 GFRP/foam core panels with prefabricated debonds show a considerable strength reduction with increasing debond diameter, with failure mechanisms varying between fast debond propagation and wrinkling-introduced face compression failure for large and small debonds, respectively. Residual strength predictions are based on intact panel testing, and a comparison between a simple numerical model and the experimental results shows fair agreement.

  9. Statistical analysis of compositional factors affecting the compressive strength of alumina-loaded epoxy (ALOX).

    Energy Technology Data Exchange (ETDEWEB)

    Montgomery, Stephen Tedford; Ahn, Sung K. (Washington State University, Pullman, WA); Lee, Moo Yul

    2006-02-01

    Detailed statistical analysis of the experimental data from testing of alumina-loaded epoxy (ALOX) composites was conducted to better understand influences of the selected compositional properties on the compressive strength of these ALOX composites. Analysis of variance (ANOVA) for different models with different sets of parameters identified the optimal statistical model as, y{sub l} = -150.71 + 29.72T{sub l} + 204.71D{sub l} + 160.93S{sub 1l} + 90.41S{sub 2l}-20.366T{sub l}S{sub 2l}-137.85D{sub l}S{sub 1l}-90.08D{sub l}S{sub 2l} where y{sub l} is the predicted compressive strength, T{sub l} is the powder type, D{sub l} is the density as the covariate for powder volume concentration, and S{sub il}(i=1,2) is the strain rate. Based on the optimal statistical model, we conclude that the compressive strength of the ALOX composite is significantly influenced by the three main factors examined: powder type, density, and strain rate. We also found that the compressive strength of the ALOX composite is significantly influenced by interactions between the powder type and the strain rate and between the powder volume concentration and the strain rate. However, the interaction between the powder type and the powder volume concentration may not significantly influence the compressive strength of the ALOX composite.

  10. Compressive strength of dental composites photo-activated with different light tips

    International Nuclear Information System (INIS)

    The aim of this study was to evaluate the compressive strength of microhybrid (Filtek™ Z250) and nanofilled (Filtek™ Supreme XT) composite resins photo-activated with two different light guide tips, fiber optic and polymer, coupled with one LED. The power density was 653 mW cm?2 when using the fiber optic light tip and 596 mW cm?2 with the polymer. After storage in distilled water at 37 ± 2?°C for seven days, the samples were subjected to mechanical testing of compressive strength in an EMIC universal mechanical testing machine with a load cell of 5 kN and speed of 0.5 mm min?1. The statistical analysis was performed using ANOVA with a confidence interval of 95% and Tamhane’s test. The results showed that the mean values of compressive strength were not influenced by the different light tips (p > 0.05). However, a statistical difference was observed (p < 0.001) between the microhybrid composite resin photo-activated with the fiber optic light tip and the nanofilled composite resin. Based on these results, it can be concluded that microhybrid composite resin photo-activated with the fiber optic light tip showed better results than nanofilled, regardless of the tip used, and the type of the light tip did not influence the compressive strength of either composite. Thus, the presented results suggest that both the fiber optic and polymer light guide tips provide adequate compressive strength to be used to make restorations. However, the fiber optic light tip associated with microhybrid composite resin may be an interesting option for restorations mainly in posterior teeth. (paper)

  11. The effect of different concentrations of chlorhexidine gluconate on the compressive strength of mineral trioxide aggregate.

    Science.gov (United States)

    Bidar, Maryam; Eslami, Neda; Naghavi, Neda; Fasihi, Zohreh; Attaran Mashhadi, Negin

    2015-01-01

    Background and aims. Substituting chlorhexidine (CHX) for water has been shown to enhance antimicrobial activity of mineral trioxide aggregate (MTA). The purpose of this study was to compare the compressive strength of MTA mixed with distilled water, 0.12% and 0.2% chlorhexidine. Materials and methods. MTA was mixed according to manufacturer's instructions in group I (n = 20). In groups II & III, 0.12% and 0.2% CHX liquid was substituted for water, respectively. Samples were condensed with moderate force into 20 tubes with 1.5×5 mm dimensions and were allowed to set for 72 hours at 37°C in 100% humidity. After being removed from the molds, their compressive strength was determined using Instron testing machine. Each group was divided into two subgroups according to the time of testing (at 72 hours, and one week). Fractured surfaces of 4 specimens in each group were then evaluated under Scanning Electron Microscope (SEM) to determine their microstructure. One-way ANOVA, Tukey, and paired sample t-test was used for statistical analysis. P < 0.05 was set as significant. Results. There was no significant difference between three groups in terms of their compressive strength after 72 hours. However, the compressive strength of group II was significantly higher than group I (P = 0.034) and group III (P = 0.021) after one week. Crystalline microstructure was similar in all groups. Conclusion. Substitution of 0.012% chlorhexidine for water significantly increased the compressive strength of MTA at 1 week without significant change in crystalline structure. PMID:25973146

  12. The Effect of Different Concentrations of Chlorhexidine Gluconate on the Compressive Strength of Mineral Trioxide Aggregate

    Directory of Open Access Journals (Sweden)

    Maryam Bidar

    2015-03-01

    Full Text Available Background and aims. Substituting chlorhexidine (CHX for water has been shown to enhance antimicrobial activity of mineral trioxide aggregate (MTA. The purpose of this study was to compare the compressive strength of MTA mixed with distilled water, 0.12% and 0.2% chlorhexidine. Materials and methods. MTA was mixed according to manufacturer’s instructions in group I (n = 20. In groups II & III, 0.12% and 0.2% CHX liquid was substituted for water, respectively. Samples were condensed with moderate force into 20 tubes with 1.5 × 5 mm dimensions and were allowed to set for 72 hours at 37°C in 100% humidity. After being removed from the molds, their compressive strength was determined using Instron testing machine. Each group was divided into two subgroups according to the time of testing (at 72 hours, and one week. Fractured surfaces of 4 specimens in each group were then evaluated under Scanning Electron Microscope (SEM to determine their microstructure. One-way ANOVA, Tu-key, and paired sample t-test was used for statistical analysis. P < 0.05 was set as significant. Results. There was no significant difference between three groups in terms of their compressive strength after 72 hours. However, the compressive strength of group II was significantly higher than group I (P = 0.034 and group III (P = 0.021 after one week. Crystalline microstructure was similar in all groups. Conclusion. Substitution of 0.012% chlorhexidine for water significantly increased the compressive strength of MTA at 1 week without significant change in crystalline structure.

  13. Optimum Compressive Strength of Hardened Sandcrete Building Blocks with Steel Chips

    Directory of Open Access Journals (Sweden)

    Alohan Omoregie

    2013-02-01

    Full Text Available The recycling of steel chips into an environmentally friendly, responsive, and profitable commodity in the manufacturing and construction industries is a huge and difficult challenge. Several strategies designed for the management and processing of this waste in developed countries have been largely unsuccessful in developing countries mainly due to its capital-intensive nature. To this end, this investigation attempts to provide an alternative solution to the recycling of this material by maximizing its utility value in the building construction industry. This is to establish their influence on the compressive strength of sandcrete hollow blocks and solid cubes with the aim of specifying the range percent of steel chips for the sandcrete optimum compressive strength value. This is particularly important for developing countries in sub-Saharan Africa, and even Latin America where most sandcrete blocks exhibit compressive strengths far below standard requirements. Percentages of steel chips relative to the weight of cement were varied and blended with the sand in an attempt to improve the sand grading parameters. The steel chips variations were one, two, three, four, five, ten and fifteen percent respectively. It was confirmed that the grading parameters were improved and there were significant increases in the compressive strength of the blocks and cube samples. The greatest improvement was noticed at four percent steel chips and sand combination. Using the plotted profile, the margin of steel chips additions for the optimum compressive strength was also established. It is recommended that steel chip sandcrete blocks are suitable for both internal load bearing, and non-load bearing walls, in areas where they are not subjected to moisture ingress. However, for external walls, and in areas where they are liable to moisture attack after laying, the surfaces should be well rendered. Below ground level, the surfaces should be coated with a water proofing agent like bitumen and cement containing waterproofing agents be used in the manufacture, laying, and rendering of steel chip sandcrete blocks.

  14. Compressive Strength and Static Modulus of Elasticity of Periwinkle Shell Ash Blended Cement Concrete

    Directory of Open Access Journals (Sweden)

    Akaninyene Afangide Umoh

    2012-11-01

    Full Text Available The study examined the effect of periwinkle shell ash as supplementary cementitious material on the compressive strength and static modulus of elasticity of concrete with a view to comparing it’s established relation with an existing model. The shells were calcined at a temperature of 800oC. Specimens were prepared from a mix of designed strength 25N/mm2. The replacement of cement with periwinkle shell ash (PSA was at five levels of 0, 10, 20, 30 and 40% by volume. A total of 90 cubical and cylindrical specimens each were cast and tested at 7, 14, 28, 90, 120 and 180 days. The results revealed that the PSA met the minimum chemical and physical requirements for class C Pozzolans. The compressive strength of the PSA blended cement concrete increased with increase in curing age up to 180 days but decreased as the PSA content increased. The design strength was attained with 10%PSA content at the standard age of 28 days. The static modulus of elasticity of PSA blended cement concrete was observed to increase with increased in curing age and decreases with PSA content. In all the curing ages 0%PSA content recorded higher value than the blended cement concrete. The statistical analysis indicated that the percentage PSA replacement and the curing age have significant effect on the properties of the concrete at 95% confidence level. The relation between compressive strength and static modulus of elasticity fitted into existing model for normal-weight concrete.

  15. Effect of dilute tungsten alloying on the dynamic strength of tantalum under ramp compression

    Science.gov (United States)

    Alexander, C. S.; Brown, J. L.; Millett, J. C. F.; Whiteman, G.; Asay, J. R.; Bourne, N. K.

    2015-06-01

    The strength of tantalum and tantalum alloys are of considerable interest due to their widespread use in both military and industrial applications. Previous work has shown that strength in these materials is tied to dislocation density and mobility within the microstructure. Accordingly, strength has been observed to increase with dilute alloying which serves to increase the dislocation density. In this study, we examine the effect of alloying on the strength of a dilute tantalum-tungsten alloy (2.5 weight percent W) under ramp compression. The strength of the alloy is measured using the ``self-consistent'' technique which examines the response under longitudinal unloading from peak compression. The results are compared to previous studies of pure tantalum and dilute tantalum-tungsten alloys under both shock and ramp compression and indicate strengthening of the alloy when compared to pure tantalum. Sandia National Labs is a multi-program laboratory managed and operated by Sandia Corp., a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  16. Strength and Ductility of Randomly Distributed Palm Fibers Reinforced Silty-Sand Soils

    OpenAIRE

    S. M. Marandi; M. H. Bagheripour; R. Rahgozar; H. ZARE

    2008-01-01

    This paper investigates the resultant strength and ductility behavior when randomly distributed palm fibers are used to reinforce silty-sand soils. The composite soils were tested under laboratory conditions and examined for unconfined compression strength (UCS), California Bearing Ratio (CBR) and compaction test. The results indicated that; the maximum and residual strengths, orientation of surface failures, ductility and the stress-strain relationship of the specimens were substantially aff...

  17. Effect of additives on the compressive strength and setting time of a Portland cement

    Scientific Electronic Library Online (English)

    Desirée Freitas Mryczka, Machado; Luiz Eduardo, Bertassoni; Evelise Machado de, Souza; Janaina Bertoncelo de, Almeida; Rodrigo Nunes, Rached.

    2010-06-01

    Full Text Available Improvements in strength and setting time of Portland cements (PC) are needed to enhance their performance as endodontic and load bearing materials. This study sought to enhance the compressive strength and setting time of a PC by adding one of the following additives: 20% and 30% poly-methylmethacr [...] ylate (PMMA), 20% and 30% irregular and spherical amalgam alloys, and 10% CaCl2. The control consisted of unreinforced PC specimens. Setting time was determined using a Gillmore apparatus according to standardized methods while compressive strength was measured using a universal testing machine after 21 hours or 60 days of water storage. Data were analyzed by ANOVA, Tukey and Games-Howell tests (? = 5%). All additives significantly decreased both initial and final setting times as compared with the PC-control (p

  18. THE COMPRESSIVE AND FLEXURAL STRENGTHS OF SELF-COMPACTING CONCRETE USING RAW RICE HUSK ASH

    Directory of Open Access Journals (Sweden)

    MD NOR ATAN

    2011-12-01

    Full Text Available This study investigates the compressive and flexural strengths of self-compacting concrete incorporating raw rice husk ash, individually and in combination with other types of mineral additives, as partial cement replacement. The additives paired with raw rice husk ash were fine limestone powder, pulverized fuel ash and silica fumes. The mix design was based on the rational method where solid constituents were fixed while water and superplasticizer contents were adjusted to produce optimum viscosity and flowability. All mixes were designed to achieve SF1 class slump-flow with conformity criteria ? 520 mm and ? 700 mm. Test results show that 15% replacement of cement using raw rice husk ash produced grade 40 concrete. It was also revealed that 30% and 45% cement replacements using raw rice husk ash combined with limestone powder and raw rice husk ash combined with limestone powder and silica fume respectively, produced comparable compressive strength to normal concrete and improved flexural strengths.

  19. COMPRESSIVE STRENGTH OF SOLID ROUND STEEL MEMBERS REINFORCED WITH SPLIT PIPE(S

    Directory of Open Access Journals (Sweden)

    Vrushali M. Tickle

    2005-01-01

    Full Text Available Results of experimental investigation on the compressive strength of twenty solid round steel leg member specimens of lattice communication towers reinforced with one or two split pipe(s are presented in this paper. The reinforcement was connected to the leg members either by means of U-bolts only or by means of U-bolts and end welding. It was found that bolt torque has no significant effect in the increase on the strength. It was also concluded that using two split pipes without end welding is better than using one split pipe with end welding. Based on the test results, a simplified and conservative design procedure in accordance to the Canadian and American Standards is proposed to determine the compressive strength of solid round steel leg members reinforced with split pipe(s.

  20. Effect of shear strength on the Hugoniot-compression curve and EOS of some metals

    Science.gov (United States)

    Mashimo, Tsutomu; Gomoto, Yuya; Liu, Xun; Zaretsky, Eugene; Katayama, Masahide; Nagayama, Kunihito

    2015-06-01

    To derive true equations of state (EOS) of matter, we need the precise Hugoniot data, and must access the strength under shock compression to draw the isothermal hydrostatic compression curve. For this, we have established the high-speed streak camera measurement system consisting of rotating-mirror type streak camera and pulsed dye laser combined with the one-stage powder gun and two-stage light gas gun. We performed the plate-mirror Hugoniot measurement experiments on tungsten (W), copper (Cu), etc. in the pressure range up to >200 GPa by symmetric impact method, and measured the Hugoniot data where the effects of tilt and bowing of the impact plate were carefully considered. It was found that the zero-intercept value (C0) of Us-Up relation (Us =C0 +SUp) of W were larger than the bulk sound velocity by 3.1%, which may show the effect of shear strength in plastic region. The hydrostatic-compression curves were drawn by using the shear strength values reported by Sandia National Laboratories group, and the EOS's were discussed. The hypothesized Us-Up Hugoniot curve of the hydrostatic compression curve converged to the bulk sound velocity.

  1. The effects of specimen scale on the compression strength of composite materials

    Science.gov (United States)

    Camponeschi, Eugene Thomas, Jr.

    1994-01-01

    This paper presents a number of observations on the effect of specimen scale on the compression response of composite materials. Work on this topic was motivated by observations that thick-walled, unstiffened carbon reinforced cylinders subjected to hydrostatic pressure were not reaching inplane laminate stress levels at failure expected from coupon level properties, while similar cylinders reinforced with fiberglass were. Results from a study on coupon strength of (0/0/90) laminates, reinforced with AS4 carbon fiber and S2 glass fiber, are presented and show that compression strength is not a function of material or specimen thickness for materials that have the same laminate quality (autoclave cured quality). Actual laminate compression strength was observed to decrease with increasing thickness, but this is attributed to fixture restraint effects on coupon response. The hypothesis drawn from the coupon level results is further supported by results from a compression test on a thick carbon reinforced coupon in a fixture with reduced influence on specimen response and from a hydrostatic test on an unstiffened carbon reinforced cylinder subjected to hydrostatic pressure with end closures designed to minimize their effect on cylinder response.

  2. Compression strength of canine bone allografts treated with various sterilization and storage methods

    International Nuclear Information System (INIS)

    The objective of this study is to determine the effect of various sterilization and preservation techniques (autoclave, deep-freeze, freeze-dried, and hydrogen peroxide vapor) done at the Philippine General Hospital Tissue Bank on the compression strength of canine bone allografts. Ninety six bone segments taken from left and right matched pairs of the humerus, radius, femur and tibia were harvested from four dogs. All of the left-sided long bones were placed in the control group and all the right sided long bones were placed in the experimental group. The average weight was 2.29 gm and 2.20 gm for the control and treatment groups, respectively. The average length was 1.8 cm for the control group and 1.8 cm for the treatment group. The average compressive area was 0.55 cm sup 2 and 0.6 cm sup 2 for the control and treatment groups, respectively. In general, all bone blocks treated with autoclave and deep-freeze showed a decrease in compression strength as compared to the control group by an average of 19.88% and 18.37%, respectively Ali bone segments treated with freeze-drying and hydrogen peroxide vapor showed an increase in the compression strength as compared to the control group by an average of 23.48% and 24.63%, respectively

  3. Analyses of spacer grids compression strength and fuel assemblies structural behavior

    International Nuclear Information System (INIS)

    Highlights: • Modeling of a 16 × 16 spacer grid to reproduce compression tests. • Evaluation of spacer grids mechanical behavior. • Modeling of fuel assembly with beam-type finite elements. • Calculation of fuel assembly natural frequencies by considering fuel rods sliding. • A new procedure to correct fuel assembly natural frequencies with weighting factor ?. -- Abstract: In this work, finite-element models were proposed to evaluate the spacer grids compression strength and structural behavior of fuel assemblies, mainly in terms of their natural frequencies. Firstly, a three-dimensional model was developed to provide consistent predictions of 16 × 16-type spacer grids compression strength. Regarding their original geometry and some possible design variations, the models were submitted to compression conditions to calculate the maximum compression force and they were validated for comparison with experimental predictions. Secondly, fuel assembly models were proposed with the aim at to correct its natural frequencies. For that, two distinct three-dimensional finite element approaches for the spacer grids, called total mesh and inner mesh, were adopted, respectively. For each model, the maximum and minimum fuel assembly lateral stiffness was determined. Also, by adopting the correction factor ?, the natural frequencies were corrected by a ?(?) value that was characteristic of each model and compared to experimental results. The procedure used in the present work permitted a good agreement between numerical and experimental natural frequencies results with the total mesh model

  4. Analyses of spacer grids compression strength and fuel assemblies structural behavior

    Energy Technology Data Exchange (ETDEWEB)

    Schettino, C.F.M.; Gouvêa, J.P.; Medeiros, N., E-mail: neil@metal.eeimvr.uff.br

    2013-07-15

    Highlights: • Modeling of a 16 × 16 spacer grid to reproduce compression tests. • Evaluation of spacer grids mechanical behavior. • Modeling of fuel assembly with beam-type finite elements. • Calculation of fuel assembly natural frequencies by considering fuel rods sliding. • A new procedure to correct fuel assembly natural frequencies with weighting factor ?. -- Abstract: In this work, finite-element models were proposed to evaluate the spacer grids compression strength and structural behavior of fuel assemblies, mainly in terms of their natural frequencies. Firstly, a three-dimensional model was developed to provide consistent predictions of 16 × 16-type spacer grids compression strength. Regarding their original geometry and some possible design variations, the models were submitted to compression conditions to calculate the maximum compression force and they were validated for comparison with experimental predictions. Secondly, fuel assembly models were proposed with the aim at to correct its natural frequencies. For that, two distinct three-dimensional finite element approaches for the spacer grids, called total mesh and inner mesh, were adopted, respectively. For each model, the maximum and minimum fuel assembly lateral stiffness was determined. Also, by adopting the correction factor ?, the natural frequencies were corrected by a ?(?) value that was characteristic of each model and compared to experimental results. The procedure used in the present work permitted a good agreement between numerical and experimental natural frequencies results with the total mesh model.

  5. Correlation between aggregate quality and compressive strength of andesite from Hungary

    Science.gov (United States)

    Czinder, Balázs; Török, Ákos

    2015-04-01

    Andesite is one of the most common lithology that is used as aggregate. Testing of aggregate quality traditionally includes Los Angeles, micro-Deval tests and the quality of the stone is assessed according to these values. In the present paper both aggregate properties and strength properties of andesites are compared in order to find correlation between aggregate strength, durability and compressive and tensile strength as well as frost resistance. Tests were made from andesite types obtained from two operating quarries of Nógrádkövesd and Gyöngyössolymos. Uniaxial compressive strength (UCS) values were compared with aggregate test results obtained from the same block. Air dry, water saturated and freeze-thaw subjected specimens were tested. According to lithological description and fabric analyses samples were grouped into 4 main lithotypes: one from Nógrádkövesd and three from Gyöngyössolymos. Fine porphyric andesite from Gyöngyössolymos provided the best micro-Deval values. In terms of uniaxial compressive strength the same trend was found, fine porphyric andesite from Gyöngyössolymos had the highest UCS under laboratory conditions, while coarser porphyritic andesite from the same quarry had lower strength. Water saturation decreased UCS as it was expected. Tensile strength values show a gradual deceases from air dry to water saturated and finally subjected to freeze-thaw cycles. Mean micro-Deval value of fine porphyric Gyöngyössolymos andesite was about 7, while that of the coarser porphyritic andesite was app. 16. These values are still higher than the mean micro-Deval test result of Nógrádkövesd andesite; which was 20. A good correlation was found in between Los Angeles and micro-Deval values, but there was no indication that micro-Deval values correlate well with UCS.

  6. COMPRESSIVE STRENGTH EVALUATION OF CONCRETE: A PARADIGMATIC USE OF WASTE (SAWDUST AND COW DUNG

    Directory of Open Access Journals (Sweden)

    Ayeni I.S

    2015-10-01

    Full Text Available This research aims to find out the optimum compressive strength of concrete produced with partial replacement of cement with cow dung and fine aggregates with sawdust. T he concrete mix of 1:2:4 was prepared using water/cement ratio of 0.65 with 0%, 2%, 4% and 6%. Sawdust and cow dung were used concurrently as partial replacement for fine aggregate s and cement respectively. The specific gravity values of cement, cow dung, stone dust (fine aggregates and sawdust are 3.13, 1.33, 3.00 and 1.25 re spectively. The compressive stren gth obtained for different percentages of replacement with cow dung and sawdust are; 8.56N/mm 2 , 14.11N/mm 2 , 17,33N/mm 2 ,18.89N/mm 2 for 0% replacement, 7.56N/mm 2 , 10.89N/mm 2 , 14.22N/mm 2 , 17.55N/mm 2 for 2% replacement, 5.22N/mm 2 , 8.72N/mm 2 , 12.22N/mm 2 , 15.72N/mm 2 for 4% replacement and 3.33N/mm 2 , 7.08N/mm 2 , 10.83N/mm 2 , 14.58N/mm 2 for 6% replacement at 7,14,21 and 28 days respectively . It was also di scovered that as curing age increases, the compressive strength increases and increase i n percentage replacement caused a corresponding decrease in the compressive strength. The Compressive strength value obtained were found to conform to the minimum requirement of 17N/mm 2 for light weight concrete especially when 2% cement and fine aggregat e were replaced with cow dung and sawdust respectively

  7. Compressive strength degradation in ZrB2-based ultra-high temperature ceramic composites

    OpenAIRE

    Ramírez-Rico, J.; Bautista, M A; Martínez-Fernández, Julián; Singh, M.

    2011-01-01

    The high temperature compressive strength behavior of zirconium diboride (ZrB2)-silicon carbide (SiC) particulate composites containing either carbon powder or SCS-9a silicon carbide fibers was evaluated in air. Constant strain rate compression tests have been performed on these materials at room temperature, 1400, and 1550°C. The degradation of the mechanical properties as a result of atmospheric air exposure at high temperatures has also been studied as a function of exposure time. The ZrB...

  8. Electrical resistivity measurement to predict uniaxial compressive and tensile strength of igneous rocks

    Indian Academy of Sciences (India)

    Sair Kahraman; Tekin Yeken

    2010-12-01

    Electrical resistivity values of 12 different igneous rocks were measured on core samples using a resistivity meter in the laboratory. The resistivity tests were conducted on the samples fully saturated with brine (NaCl solution) and the uniaxial compressive strength (UCS), Brazilian tensile strength, density and porosity values of the samples were determined in the laboratory. The test results were evaluated using simple and multiple regression analysis. It was seen that the UCS and tensile strength values were linearly correlated with the electrical resistivity. The correlation coefficients are generally higher for the multiple regression models than that of the simple regression models. It was concluded that the UCS and tensile strength of igneous rocks can be estimated from electrical resistivity. However, the derived relations are purely empirical and they should be checked for other igneous rocks. The effect of rock types such as sedimentary and metamorphic rocks on the derived equations also needs to be investigated.

  9. Development of optimization models for the set behavior and compressive strength of sodium activated geopolymer pastes

    Science.gov (United States)

    Fillenwarth, Brian Albert

    As large countries such as China begin to industrialize and concerns about global warming continue to grow, there is an increasing need for more environmentally friendly building materials. One promising material known as a geopolymer can be used as a portland cement replacement and in this capacity emits around 67% less carbon dioxide. In addition to potentially reducing carbon emissions, geopolymers can be synthesized with many industrial waste products such as fly ash. Although the benefits of geopolymers are substantial, there are a few difficulties with designing geopolymer mixes which have hindered widespread commercialization of the material. One such difficulty is the high variability of the materials used for their synthesis. In addition to this, interrelationships between mix design variables and how these interrelationships impact the set behavior and compressive strength are not well understood. A third complicating factor with designing geopolymer mixes is that the role of calcium in these systems is not well understood. In order to overcome these barriers, this study developed predictive optimization models through the use of genetic programming with experimentally collected set times and compressive strengths of several geopolymer paste mixes. The developed set behavior models were shown to predict the correct set behavior from the mix design over 85% of the time. The strength optimization model was shown to be capable of predicting compressive strengths of geopolymer pastes from their mix design to within about 1 ksi of their actual strength. In addition to this the optimization models give valuable insight into the key factors influencing strength development as well as the key factors responsible for flash set and long set behaviors in geopolymer pastes. A method for designing geopolymer paste mixes was developed from the generated optimization models. This design method provides an invaluable tool for use in future geopolymer research as well as commercial development of geopolymer products.

  10. The Effect on the Flexural Strength, Flexural Modulus and Compressive Strength of Fibre Reinforced Acrylic with That of Plain Unfilled Acrylic Resin – An in Vitro Study

    Science.gov (United States)

    Thomas, Tony C; K, Aswini Kumar; Krishnan, Vinod; Mathew, Anil; V, Manju

    2015-01-01

    Aim: The aim of this in vitro study was to compare the flexural strength, the flexural modulus and compressive strength of the acrylic polymer reinforced with glass, carbon, polyethylene and Kevlar fibres with that of plain unfilled resin. Materials and Methods: A total of 50 specimens were prepared and divided into 10 specimens each under 5 groups namely group 1- control group without any fibres, group 2 – carbon fibres, group 3- glass fibres, group 4 – polyethylene, group 5- Kevlar. Universal testing machine (Tinius olsen, USA) was used for the testing of these specimens. Out of each group, 5 specimens were randomly selected and testing was done for flexural strength using a three point deflection test and three point bending test for compressive strength and the modulus was plotted using a graphical method. Statistical analysis was done using statistical software. Results: The respective mean values for samples in regard to their flexural strength for PMMA plain, PMMA+ glass fibre, PMMA+ carbon, PMMA+ polyethylene and PMMA+ Kevlar were 90.64, 100.79, 102.58, 94.13 and 96.43 respectively. Scheffes post hoc test clearly indicated that only mean flexural strength values of PMMA + Carbon, has the highest mean value. One-way ANOVA revealed a non-significant difference among the groups in regard to their compressive strength. Conclusion: The study concludes that carbon fibre reinforced samples has the greatest flexural strength and greatest flexural modulus, however the compressive strength remains unchanged. PMID:25954696

  11. Prediction of concrete compressive strength considering humidity and temperature in the construction of nuclear power plants

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Seung Hee; Jang, Kyung Pil [Department of Civil and Environmental Engineering, Myongji University, Yongin (Korea, Republic of); Bang, Jin-Wook [Department of Civil Engineering, Chungnam National University, Daejeon (Korea, Republic of); Lee, Jang Hwa [Structural Engineering Research Division, Korea Institute of Construction Technology (Korea, Republic of); Kim, Yun Yong, E-mail: yunkim@cnu.ac.kr [Structural Engineering Research Division, Korea Institute of Construction Technology (Korea, Republic of)

    2014-08-15

    Highlights: • Compressive strength tests for three concrete mixes were performed. • The parameters of the humidity-adjusted maturity function were determined. • Strength can be predicted considering temperature and relative humidity. - Abstract: This study proposes a method for predicting compressive strength developments in the early ages of concretes used in the construction of nuclear power plants. Three representative mixes with strengths of 6000 psi (41.4 MPa), 4500 psi (31.0 MPa), and 4000 psi (27.6 MPa) were selected and tested under various curing conditions; the temperature ranged from 10 to 40 °C, and the relative humidity from 40 to 100%. In order to consider not only the effect of the temperature but also that of humidity, an existing model, i.e. the humidity-adjusted maturity function, was adopted and the parameters used in the function were determined from the test results. A series of tests were also performed in the curing condition of a variable temperature and constant humidity, and a comparison between the measured and predicted strengths were made for the verification.

  12. Prediction of concrete compressive strength considering humidity and temperature in the construction of nuclear power plants

    International Nuclear Information System (INIS)

    Highlights: • Compressive strength tests for three concrete mixes were performed. • The parameters of the humidity-adjusted maturity function were determined. • Strength can be predicted considering temperature and relative humidity. - Abstract: This study proposes a method for predicting compressive strength developments in the early ages of concretes used in the construction of nuclear power plants. Three representative mixes with strengths of 6000 psi (41.4 MPa), 4500 psi (31.0 MPa), and 4000 psi (27.6 MPa) were selected and tested under various curing conditions; the temperature ranged from 10 to 40 °C, and the relative humidity from 40 to 100%. In order to consider not only the effect of the temperature but also that of humidity, an existing model, i.e. the humidity-adjusted maturity function, was adopted and the parameters used in the function were determined from the test results. A series of tests were also performed in the curing condition of a variable temperature and constant humidity, and a comparison between the measured and predicted strengths were made for the verification

  13. Compressive Strength and Static Modulus of Elasticity of Periwinkle Shell Ash Blended Cement Concrete

    OpenAIRE

    Akaninyene Afangide Umoh; Kolapo O. Olusola

    2012-01-01

    The study examined the effect of periwinkle shell ash as supplementary cementitious material on the compressive strength and static modulus of elasticity of concrete with a view to comparing it’s established relation with an existing model. The shells were calcined at a temperature of 800oC. Specimens were prepared from a mix of designed strength 25N/mm2. The replacement of cement with periwinkle shell ash (PSA) was at five levels of 0, 10, 20, 30 and 40% by volume. A total of 90 cubica...

  14. Determination of composition of pozzolanic waste mixtures with optimized compressive strength

    Directory of Open Access Journals (Sweden)

    Nardi José Vidal

    2004-01-01

    Full Text Available The utilization of ceramic wastes with pozzolanic properties along with other compounds for obtaining new materials with cementating properties is an alternative for reducing the environmental pollution. The acceptance of these new products in the market demands minimal changes in mechanical properties according to its utilization. For a variable range of compositional intervals, attempts were made to establish limiting incorporation proportions that assure the achievement of minimum pre-established mechanical strength values in the final product. In this case minimum compressive strength value is 3,000 kPa. A simultaneous association of other properties is also possible.

  15. Analysis of the Flexure Behavior and Compressive Strength of Fly Ash Core Sandwiched Composite Material

    Directory of Open Access Journals (Sweden)

    Vijaykumar H.K

    2014-07-01

    Full Text Available In this paper, commercially available Fly Ash and Epoxy is used for the core material, woven glass fabric as reinforcing skin material, epoxy as matrix/adhesive materials used in this study for the construction of sandwich composite. Analysis is carried out on different proportions of epoxy and fly ash sandwiched composite material for determining the flexural strength and compressive strength, three different proportions of epoxy and fly ash used for the study. Those are 65%-35% (65% by weight fly ash and 35% by weight epoxy resin composite material, 60%-40% and 55%-45% composite material. 60%-40% composite material specimen shows better results in the entire test carried out i.e. Flexure and Compression. The complete experimental results are discussed and presented in this paper.

  16. Increasing the compressive strength of portland cement concrete using flat glass powder

    International Nuclear Information System (INIS)

    This paper analyzes the compressive strength of Portland cement concrete in response to the incorporation of 5%, 10% and 20% of flat glass powder in place of sand, at w/c (water/cement) ratios of 0.50, 0.55 and 0.58. A statistical analysis of variance (ANOVA) was performed after 7, 14 and 28 days of curing. The compressive strength test results indicate that the concrete containing a w/c ratio of 0.50 can be used for structural applications, regardless of the waste glass content, as can that with a w/c ratio of 0.55 containing 20% of waste glass. We suggest that the use of flat glass powder in place of sand in the above mentioned percentages is feasible for the production of an environmentally appropriate and structurally applicable concrete. However, the concrete's fluidity and void content must be taken into account. (author)

  17. Increasing the compressive strength of Portland cement concrete using flat glass powder

    Scientific Electronic Library Online (English)

    Edson Jansen Pedrosa de, Miranda Júnior; Helton de Jesus Costa Leite, Bezerra; Flávio Salgado, Politi; Antônio Ernandes Macêdo, Paiva.

    2014-08-01

    Full Text Available This paper analyzes the compressive strength of Portland cement concrete in response to the incorporation of 5%, 10% and 20% of flat glass powder in place of sand, at w/c (water/cement) ratios of 0.50, 0.55 and 0.58. A statistical analysis of variance (ANOVA) was performed after 7, 14 and 28 days of [...] curing. The compressive strength test results indicate that the concrete containing a w/c ratio of 0.50 can be used for structural applications, regardless of the waste glass content, as can that with a w/c ratio of 0.55 containing 20% of waste glass. We suggest that the use of flat glass powder in place of sand in the abovementioned percentages is feasible for the production of an environmentally appropriate and structurally applicable concrete. However, the concrete's fluidity and void content must be taken into account.

  18. Increasing the compressive strength of portland cement concrete using flat glass powder

    Energy Technology Data Exchange (ETDEWEB)

    Miranda Junior, Edson Jansen Pedrosa de; Bezerra, Helton de Jesus Costa Leite; Politi, Flavio Salgado; Paiva, Antonio Ernandes Macedo, E-mail: edson.jansen@ifma.edu.br [Instituto Federal de Educacao, Ciencia e Tecnologia do Maranha (IFMA), Sao Luis, MA (Brazil). Dept. de Mecanica e Materiais

    2014-08-15

    This paper analyzes the compressive strength of Portland cement concrete in response to the incorporation of 5%, 10% and 20% of flat glass powder in place of sand, at w/c (water/cement) ratios of 0.50, 0.55 and 0.58. A statistical analysis of variance (ANOVA) was performed after 7, 14 and 28 days of curing. The compressive strength test results indicate that the concrete containing a w/c ratio of 0.50 can be used for structural applications, regardless of the waste glass content, as can that with a w/c ratio of 0.55 containing 20% of waste glass. We suggest that the use of flat glass powder in place of sand in the above mentioned percentages is feasible for the production of an environmentally appropriate and structurally applicable concrete. However, the concrete's fluidity and void content must be taken into account. (author)

  19. Pozzolanic Properties of Micronized Biomass Silica in Enhancing Compressive Strength and Water Permeability of Concrete

    OpenAIRE

    Suraya Hani Adnan; Ismail Abdul Rahman; Hamidah Mohd Saman; Fetra Venny Riza

    2012-01-01

    This study presents the analysis and the benefits from using Micronized Biomass Silica (MBS) of rice husk which comprises of high content of silica. MBS was generated from controlled burning of the husk into off-white biomass silica ash and crushing the ash into micronized size. Concrete samples containing various percentages of MBS were tested for workability, compressive strength and also water permeability performances. It was found that the optimum percentage of MBS added to the concrete...

  20. Influence of Cementitious Materials and Aggregates Content on Compressive Strength of Palm Kernel Shell Concrete

    OpenAIRE

    U.J. Alengaram; M.Z. Jumaat; H. Mahmud

    2008-01-01

    This study reports the effect of cementitious materials, fine and coarse aggregates content on workability and compressive strength of palm kernel shell concrete. Palm kernel shells a by product of the production of palm oil, were used as lightweight aggregates. The following cementitious materials were added: 10% silica fume as additional cementitious material and 5% fly ash as cement replacement on weight of cement. The influence of varying fine aggregate and palm kernel shell content...

  1. Determination of characteristic compressive strength of self- compacting and vibrated concrete

    OpenAIRE

    Turel, Marko

    2006-01-01

    The use of self-compacting concrete is increasing due to the demand of faster work performance and better working conditions. The leadership countries in this field are European, and especially Scandinavian countries. Also Slovenian constructors are using self- compacting concrete where performing mechanical vibrations is difficult or impossibile. The purpose of the present Graduation thesis is to determinate the characteristic compressive strength of self-compacting concrete taking in consid...

  2. Influence of ultrasonic setting on compressive and diametral tensile strengths of glass ionomer cements

    Scientific Electronic Library Online (English)

    Terezinha Jesus Esteves, Barata; Eduardo, Bresciani; Akimi, Adachi; Ticiane Cestari, Fagundes; Carlos Augusto Ramos, Carvalho; Maria Fidela Lima, Navarro.

    2008-03-01

    Full Text Available The aim of this study was to assess the influence of ultrasonic wave propagation on the compressive (CS) and diametral tensile (DTS) strengths of glass ionomer cements (GICs). Three variables were evaluated: conventional GICs, ultrasonic excitation and storage time (1 hour, 24 hours and 7 days). Bov [...] ine teeth molds were used for simulating a clinical ultrasonic excitation. The data were submitted to three-way ANOVA and Tukey tests (P

  3. Effect of mix composition on compressive strength and microstructure of fly ash based geopolymer composites

    Directory of Open Access Journals (Sweden)

    Ravindra N. Thakur

    2009-06-01

    Full Text Available Geopolymer is a class of aluminosilicate binding materials synthesized by thermal activation of solid aluminosilicate base materials such as fly ash, metakaolin, GGBS etc. with an alkali metal hydroxide and silicate solution. These binders are currently attracting widespread attention due to their potential utilization as a high performance, environmental friendly and sustainable alternative to Portland cement. The present paper reports results of an experimental study on development of compressive strength and microstructure of geopolymer paste and mortar specimens prepared by thermal activation of Indian fly ash with sodium hydroxide and sodium silicate solution. The effect of main synthesis parameters such as alkali content(Na2O/Al2O3, silica content (SiO2/Al2O3, water to geopolymer solid ratio and sand to fly ash ratio of geopolymer mixture and processing parameters such as curing time and curing temperature on development of compressive strength and microstructure of fly ash based geopolymer paste and mortar were studied. The compressive strength of 48.20MPa was obtained for geopolymer mixture cured at 850C for 24 hours with alkali content of 0.62 and silica content of 4.0. The mineralogical and microstructure studies on hardened geopolymer performed by means Scanning electron microscope (SEM and X-ray diffraction (XRD, showed formation of a new amorphous alumino-silicate phase such as hydroxysodalite and herschelite influenced development of compressive strength. The results obtained in the current research will be useful for developing of mix design guidelines for commercial exploitation of the new binding material.

  4. EXPERIMENTAL STUDY ON EFFECT OF VARIOUS FACTORS ON COMPRESSIVE STRENGTH OF CONCRETE

    Directory of Open Access Journals (Sweden)

    Hanifi B?N?C?

    2000-03-01

    Full Text Available In this study, the factors affecting at the compressive strength of the concrete were determined. According the result of the test, the quality of concrete, which was used, is very low. Cement, analysis of aggregates for concrete, compacting, mixing placing and curing of concrete, and the techniques of the production of concrete have effected by different ratio of the quality of concrete.

  5. A Simplified Method for predicting Ultimate Compressive Strength of Ship Panels

    DEFF Research Database (Denmark)

    Paik, Jeom Kee; Pedersen, Preben Terndrup

    1996-01-01

    A simplified method for predicting ultimate compressive strength of ship panels which have complex shape of the initial deflection is described. The procedure consist of the elastic large deflection theory and the rigid-plastic analysis based on the collapse mechanism taking into account large deformation effects. By taking only one component for the selected deflection function, the computer time for the elastic large deflection analysis will be drastically reduced. The validity of the procedur...

  6. Design and Fabrication of a Compression Strength Testing Machine for Blocks and Clay Bricks

    OpenAIRE

    Abdulkadir Baba HASSAN; Yahaya Ahmed BUKAR

    2009-01-01

    This study was carried out to design and fabricate a cost effective and efficient compression strength tester to carter for the needs of stakeholders in the blocks and bricks industries. In carrying out the project work a thorough study of the foreign testers and the requirements of the Nigerian industrial standards, NIS 87:2000 and NIS 74:1976 for blocks and clay bricks respectively was done. Design drawings and calculations were established and the machine was fabricated with well selected ...

  7. THE DENSITY, COMPRESSION STRENGTH AND SURFACE HARDNESS OF HEAT TREATED HORNBEAM (Carpinus betulus L.) WOOD

    OpenAIRE

    Gokhan Gunduz,; Suleyman Korkut; Deniz Aydemir; Ilter Bekar

    2009-01-01

    The heat treatment of wood is an environment-friendly method for wood preservation. The heat treatment process only uses steam and heat, and no chemicals or agents are applied to the material during the process. Tests have shown no harmful emissions are apparent when working with the material. This process improves wood’s resistance to decay and its dimensional stability. In this study, the density, compression strength and hardness of heat treated hornbeam (Carpinus betulus L.) wood were inv...

  8. Uniaxial compressive strength prediction of jet grouting columns using support vector machines

    OpenAIRE

    Tinoco, Joaquim Agostinho Barbosa; Correia, A. Gomes; Cortez, Paulo

    2011-01-01

    Uniaxial compressive strength (UCS) is the mechanical properties currently used in geotechnical works design, namely in jet grouting (JG) treatments. However, when working with this soil improvement technology, due to its inherent geological complexity and high number of variables involved, such design is a hard, perhaps very hard task. To help in such task, a support vector machine (SVM), which is a data mining algorithm particularly adequate to explore high number of complex data, was train...

  9. Effect of compressive prestress on the Young's modulus and strength of isotropic graphite

    International Nuclear Information System (INIS)

    It is well known that properties, such as Young's modulus, strength and so on, change when compressive or tensile prestresses are applied to graphite materials at room temperature. It is important from the designer's standpoint in the sense that it should be taken into consideration for the structural design of the graphite components if there is an effect of prestresses at high temperature on the mechanical properties. In this study compressive prestresses were applied to an isotropic fine-grained graphite at room temperature (RT) and high temperature (2010 deg. C). As a result decrease in Young's modulus due to high temperature prestressing was 56% which was much larger than the 6.4% that was due to RT prestressing. This finding was considered to be due primarily to difference in degree of preferred orientation of crystallites in the graphite on the basis of Bacon anisotropy factor (BAF) from X-ray diffraction measurement of the prestressed specimens. Furthermore, high temperature compressive prestressing produced an increase in the strength of the isotropic graphite, although room temperature prestressing produced no such effect. The results obtained here suggest that isotropic graphite which is subjected to high-temperature compressive stress becomes anisotropic. It is concluded that it should be considered in the design stage of the reactors that the anisotropy may change after long term operation of high temperature gas-cooled reactors. (author). 6 refs, 8 figs, 3 tabs

  10. Comparative Evaluation of the Compressive Strength of a Direct Composite Resin and Two Laboratorial Resins

    Directory of Open Access Journals (Sweden)

    Alexandre Costa Reis BRITO

    2007-05-01

    Full Text Available Purpose: To compare the compressive strength of two commercially available laboratorial resins - Solidex® (Shofu and Cristobal® (Dentsply - to that of a direct composite resin (Concept®; Vigodent, as a control group.Method: Five specimens of each tested material were fabricated using stainless steel matrices with the following dimensions: 8 mm of internal diameter on the base, 9 mm of internal diameter on the top and 4 mm of height. The specimens were stored in distilled water for 72 hours and submitted to an axial load by the action of a 2-mm-diameter round-end tip adapted to a universal testing machine (EMIC 500. A 200 kgf load cell was used running at a crosshead speed of 0.5 mm/min. The load and the point of failure were recorded. Results: Means, in kgf, were: Concept® (Ct = 124.26; Cristobal® (C =184.63; Solidex® (S =173.58. Data (means and standard deviations were analyzed statistically by ANOVA and Tukey’s for comparisons among the groups using the SPSS software (version 10.0. Significance level was set at á=0.05 (95%. Concept® presented significantly lower (p<0.05 compressive strength than the other two materials, Cristobal® and Solidex®, which, in turn, did not differ significantly to each other.Conclusion: Cristobal® and Solidex® laboratorial resins did not show significant difference to each other and both presented compressive strength significantly higher than that of Concept® direct resin.

  11. Compressive Strength and Setting Time of MTA and Portland Cement Associated with Different Radiopacifying Agents.

    Science.gov (United States)

    Tanomaru-Filho, Mario; Morales, Vanessa; da Silva, Guilherme F; Bosso, Roberta; Reis, José M S N; Duarte, Marco A H; Guerreiro-Tanomaru, Juliane M

    2012-01-01

    Objective. The aim of this study was to evaluate the compressive strength and setting time of MTA and Portland cement (PC) associated with bismuth oxide (BO), zirconium oxide (ZO), calcium tungstate (CT), and strontium carbonate (SC). Methods. For the compressive strength test, specimens were evaluated in an EMIC DL 2000 apparatus at 0.5?mm/min speed. For evaluation of setting time, each material was analyzed using Gilmore-type needles. The statistical analysis was performed with ANOVA and the Tukey tests, at 5% significance. Results. After 24 hours, the highest values were found for PC and PC + ZO. At 21 days, PC + BO showed the lowest compressive strength among all the groups. The initial setting time was greater for PC. The final setting time was greater for PC and PC + CT, and MTA had the lowest among the evaluated materials (P < 0.05). Conclusion. The results showed that all radiopacifying agents tested may potentially be used in association with PC to replace BO. PMID:22957262

  12. Compressive strength of radiation-induced polymer impregnated autoclaved lime-rich clay

    International Nuclear Information System (INIS)

    Factors affecting the radiation-induced polymer impregnation of autoclaved lime-rich clay specimens have been investigated. The monomer used is acrylic acid and it was found that the amount of monomer absorbed by the autoclaved specimens increases with increase of acrylic acid concentration and with impregnation time. The degree of polymer incorporation at a fixed ?-irradiation dose of 20 kGy increased with impregnation time of monomer up to 5 hr and also with monomer concentration. An improvement in the compressive strength of the polymer-impregnated autoclaved specimens was observed, and was found to depend mainly on the degree of polymer incorporation. The compressive strength of the autoclaved impregnated specimens was twice the value of the unimpregnated at a degree of polymer incorporation of 12%. The effect of ?-irradiation dose on the degree of polymer incorporation and on the compressive strength of the specimens was also investigated. Infrared and scanning electron microscopic studies of the polymer impregnated specimens were carried out. (author)

  13. Characterization of Erodibility Using Soil Strength and Stress-Strain Indices for Soils in Some Selected Sites in Imo State

    OpenAIRE

    N.A.A. Okereke; C.C. Egwuonwu

    2012-01-01

    In this study, initial soil strength indices (qu) and stress-strain characteristics namely failure strain (?f); area under the stress-strain curve up to failure (Is) and stress-strain modulus between no load and failure (Es) were investigated as potential indicators for characterizing the erosion resistance of two compacted soils namely Sandy Clay Loam (SCL) and Clay Loam (CL) in some selected sites in Imo State, Nigeria. The unconfined compressive strength (used in obtaining strength indices...

  14. THE EFFECTS OF WOODEN BOARDS AND ADHESIVE TYPES TO DIAGONAL COMPRESSION AND TENSILE STRENGTHS ON THE BOX CONSTRUCTION

    Directory of Open Access Journals (Sweden)

    Mustafa ALTINOK

    2003-01-01

    Full Text Available The main factor for furniture manufacturing with box construction is diagonal compression or diagonal tensile strength on joint points. This strength differences according to type of wooden board joining style an glue type.In this study, the effects of lathly joining with different glue type on the different wooden board in box construction manufacturing was experimentally tested by diagonal compression and tensile test methods. Finally, it was determined that the diagonal compression and tensile strengths were lower in all lathly joining wooden board with used polyviniyl acetat glue and those were higer with used desmodur-vtka glue.

  15. Prediction of compression strength of high performance concrete using artificial neural networks

    Science.gov (United States)

    Torre, A.; Garcia, F.; Moromi, I.; Espinoza, P.; Acuña, L.

    2015-01-01

    High-strength concrete is undoubtedly one of the most innovative materials in construction. Its manufacture is simple and is carried out starting from essential components (water, cement, fine and aggregates) and a number of additives. Their proportions have a high influence on the final strength of the product. This relations do not seem to follow a mathematical formula and yet their knowledge is crucial to optimize the quantities of raw materials used in the manufacture of concrete. Of all mechanical properties, concrete compressive strength at 28 days is most often used for quality control. Therefore, it would be important to have a tool to numerically model such relationships, even before processing. In this aspect, artificial neural networks have proven to be a powerful modeling tool especially when obtaining a result with higher reliability than knowledge of the relationships between the variables involved in the process. This research has designed an artificial neural network to model the compressive strength of concrete based on their manufacturing parameters, obtaining correlations of the order of 0.94.

  16. Size effects on tensile and compressive strengths in metallic glass nanowires

    Science.gov (United States)

    Zhou, Xiaoling; Zhou, Haofei; Li, Xiaoyan; Chen, Changqing

    2015-11-01

    Shear localization induced brittleness is the main drawback of metallic glasses which restricts their practical applications. Previous experiments have provided insights on how to suppress shear localization by reducing the sample size of metallic glasses to the order of 100 nm. In order to reveal the size effects and associated deformation mechanisms of metallic glasses in an even finer scale, we perform large-scale atomistic simulations for the uniaxial compression and tension of metallic glass nanowires. The simulation results show that, as the diameter of metallic glass samples decreases from 45 nm to 8 nm, the tensile yield strength increases while the compressive yield strength decreases. Homogeneous flow is observed as the governing deformation mechanism in all simulated metallic glass samples, where plastic shearing tends to initiate on the sample surface and propagate into the interior. To rationalize the size dependence of yield strengths, we propose a theoretical model based on the concept of surface stress and Mohr-Coulomb criterion. The theoretical predictions agree well with the simulation results, implying the important role of surface stress on the yielding of MGs below 100 nm. Finally, a discussion about the size effects of strength in metallic glasses at different length scales is provided. Our results suggest that the shear band energy and surface stress might be the two crucial parameters in determining the critical size required for the transition from shear localization to homogeneous deformation in MGs.

  17. Influence of ultrasonic setting on compressive and diametral tensile strengths of glass ionomer cements

    Directory of Open Access Journals (Sweden)

    Terezinha Jesus Esteves Barata

    2008-03-01

    Full Text Available The aim of this study was to assess the influence of ultrasonic wave propagation on the compressive (CS and diametral tensile (DTS strengths of glass ionomer cements (GICs. Three variables were evaluated: conventional GICs, ultrasonic excitation and storage time (1 hour, 24 hours and 7 days. Bovine teeth molds were used for simulating a clinical ultrasonic excitation. The data were submitted to three-way ANOVA and Tukey tests (P < 0.05. All the tested conventional GICs presented an increase in strength from 1 hour to 7 days for CS and DTS. Ultrasonic excitation resulted in a statistically significant increase in the CS, but showed no statistically significant difference in the DTS. Regardless the GICs tested the increase in strength was maturation time-dependent for all groups.

  18. Strength Studies of Dadri Fly Ash Modified with Lime Sludge – A Composite Material

    Directory of Open Access Journals (Sweden)

    Vaishali Sahu

    2014-07-01

    Full Text Available The aim of the present work is to prepare a new type of fly ash–lime sludge composite totally composed with industrial by-products which can be utilized as road construction material. The lime sludge content was varied from 10% to 50% (at an interval of 10% and the various composites were tested for unconfined compressive strength after 7 and 28 days curing period. The mix formula of this composite was optimized based on maximum strength and equal utilization of both the by-products. The composite with optimal mix formula (fly ash/lime sludge =1:1 results in highest strength. This paper outlines the characteristics of fly ash and lime sludge, method of preparation of compaction specimen and unconfined compression test specimen, testing procedure and salient results thereof. The strength formation mechanism of this composite is discussed. This composite can be further engineered as road construction material with competitive properties.

  19. A study on the effect of nano silica on compressive strength of high volume fly ash mortars and concretes

    International Nuclear Information System (INIS)

    Highlights: • The addition of NS compensates low early age compressive strength of HVFA system. • NS also contributes to later age compressive strength gain of HVFA system. • The XRD results confirm the reduction of CH in HVFA paste due to addition of NS. - Abstract: This paper presents the effect of nano silica (NS) on the compressive strength of mortars and concretes containing different high volume fly ash (HVFA) contents ranging from 40% to 70% (by weight) as partial replacement of cement. The compressive strength of mortars is measured at 7 and 28 days and that for concretes is measured at 3, 7, 28, 56 and 90 days. The effects of NS in microstructure development and pozzolanic reaction of pastes containing above HVFA contents are also studied through backscattered electron (BSE) image and X-ray diffraction (XRD) analysis. Results show that among different NS contents ranging from 1% to 6%, cement mortar containing 2% NS exhibited highest 7 and 28 days compressive strength. This NS content (2%) is then added to the HVFA mortars and concretes and the results show that the addition of 2% NS improved the early age (7 days) compressive strength of mortars containing 40% and 50% fly ash by 5% and 7%, respectively. However, this improvement is not observed at high fly ash contents beyond 50%. On the other hand, all HVFA mortars exhibited improvement in 28 days compressive strength due to addition of 2% NS and the most significant improvement is noticed in mortars containing more than 50% fly ash. In HVFA concretes, the improvement of early age (3 days) compressive strength is also noticed due to addition of 2% NS. The BSE and XRD analysis results also support the above findings

  20. Lumbar vertebral body compressive strength evaluated by dual-energy X-ray absorptiometry, quantitative computed tomography, and ashing

    DEFF Research Database (Denmark)

    Ebbesen, Ebbe Nils; Thomsen, Jesper Skovhus

    1999-01-01

    Bone densitometry with DXA (dual energy X-ray absorptiometry) and QCT (quantitative computed tomography) techniques are used for in vivo assessment of bone strength and thereby prediction of fracture risk. However, only few in vitro studies have investigated and compared these techniques' ability to determine vertebral compressive strength. The aim of the present study was to (1) assess the predictive value of DXA, QCT, and pQCT (peripheral QCT) for vertebral bone compressive strength assessed by mechanical testing; (2) describe both linear and power relationship between density and strength; and (3) evaluate whether gender-related differences in the above relations were present. The material comprised human lumbar vertebrae L3 from 51 women and 50 men (age range: 18 to 96 years). The study showed that both DXA and CT techniques (QCT and pQCT) have a high predictive value for vertebral strength. The DXA BMD had a high correlation with maximum compressive load (r2 = 0.86). The QCT and pQCT had high correlations with maximum compressive stress (r2 = 0.75 and r2 = 0.86, respectively). The correlation between ash density of the biomechanically tested specimen and maximum compressive stress was r2 = 0.88. There were no differences between linear and power fit in the degree of determination between density and strength. There was no gender-related difference in the relationship between volumetric density and maximum compressive stress. In conclusion, it was demonstrated that DXA, QCT, and pQCT are ex situ equally capable of predicting vertebral compressive strength with a degree of determination (r2) between 75% and 86%. No differences were found between linear and power analysis of the relationship between density and strength, and no difference was found in the density strength relationship between women and men.

  1. Comparative study on compressive strength of Self cured SCC and Normally cured SCC

    Directory of Open Access Journals (Sweden)

    Ms. Akanksha A. Patil

    2014-11-01

    Full Text Available Curing is the process of maintaining proper moisture content particularly within 28 days to promote optimum cement hydration immediately after placement. Self-compacting concrete is made up of admixture i.e. superplasticizer. In recent years, self-compacting concrete (SCC has gained wide use for placement in congested reinforced concrete structures with difficult casting conditions. Also various curing methods are adopted in the construction industry especially for vertical structures, inaccessible areas s.a. high rise buildings, water scarce areas etc. In such structures conventional curing is not practically possible in most of the cases. But we need efficient curing which improves the strength and durability of concrete. In the present work, comparison of compressive strength of normally cured SCC and SCC cured with self curing material i.e. wax based, white pigmented, membrane forming concrete curing compound has been done. This study is investigating that weather the use of self curing compound is economical or not in remote areas of water without compromising with the compressive strength of concrete.

  2. Influence of curing regimes on compressive strength of ultra high performance concrete

    Indian Academy of Sciences (India)

    Prabhat Ranjan Prem; B H Bharatkumar; Nagesh R Iyer

    2013-12-01

    The present paper is aimed to identify an efficient curing regime for ultra high performance concrete (UHPC), to achieve a target compressive strength more than 150 MPa, using indigenous materials. The thermal regime plays a vital role due to the limited fineness of ingredients and low water/binder ratio. By activation of the reaction kinetics, the effectiveness of the binder is enhanced which leads to improvements in mechanical as well as durability properties. The curing cycle employed are ambient air curing, water curing and hot air curing. The specimens were exposed to thermal regime at (90°C/150°C/200°C) for duration of 24, 48 or 72 hours at the age of 3rd and 7th day followed with air curing or water curing till 28 days. The results showed a marked difference in compressive strength ranging from 217 to 142 MPa with change in curing regimes. The samples when thermally cured at the age of 3rd and 7th day produced an average ultimate strength of 217–152 MPa and 196–150 MPa, respectively.

  3. Characterizing compressive and fracture strengths of fiber reinforced composites using off-axis specimens

    Science.gov (United States)

    Bing, Qida

    The present report focuses on testing and modeling strain rate dependent compressive and fracture strengths of unidirectional fiber reinforced composites by using off-axis specimens. Experimental results in split Hopkinson pressure bar (SHPB) tests with AS4/3501-6 off-axis specimens showed large bending wave existing in the incident bar and transmission bar because of the strong interface friction induced by the direct contacts between the stiff fiber ends and loading surfaces, thus the extension-shear coupling was prevented fully developing in the off-axis specimens under compression and the one-dimensional wave propagation assumption in the SHPB analysis was violated. Through the vapor deposition technique a thin titanium layer is coated on both specimen ends, smooth sliding between loading surfaces and specimen ends assures the pressure is the only interaction. Stress-strain curves are generated at different strain rate using this type of specimens with various off-axis angles under strain controlled testing mode. From these curves a rate-dependent viscoplasticity constitutive model is developed to predict the stress-strain relations at various strain rates and a compressive strength model is established from the viscoplasticity model for AS4/3501-6 carbon/epoxy composite. Comparison between the model predictions and experimental results shows good agreement and indicates that the compressive strength model obtained by using low strain rate test data is valid for high strain rate too. From the established rate dependent compressive strength model, the longitudinal compressive strengths at various strain rates are predicted. Through an extrapolation technique proposed in the work, rate dependent 0° compressive strengths of unidirectional AS4/3501-6 composite are obtained from off-axis test data and compared to model predictions. By utilizing the advantage of off-axis specimens that a combined stress state can be obtained from a simple uniaxial loading, a new method to perform mode II fracture tests is presented which involves using off-axis specimen by properly introducing a pre-crack in the specimen along the fiber direction. Static off-axis fracture tests are conducted with S2/8552 glass/epoxy composite at various off-axis angles and finite element (FE) method is used to evaluate the critical mode II energy release rate (fracture toughness). Note that the crack surface is not frictionless and existence of pressure on the crack surfaces, crack surface friction is considered in the FE analysis and it is found that the virtual crack closure method is still valid in the presence of crack surface friction. Different crack surface frictions are obtained by varying the off-axis angle and friction effect on mode II fracture toughness of S2/8552 glass/epoxy composite is found to increase as off-axis angle increases. Moreover, the transverse compressive stress is found to have significant effect on mode II energy release rate from FE analysis. The small size of block off-axis specimen makes it possible to perform dynamic fracture tests on a SHPB setup and high crack propagation speed is obtained with this type of specimen. By defining a time rate of mode II energy release rate GcI? to represent the load rate or using average strain rate of the off-axis specimen, it is found that the dynamic initiation mode II fracture toughness is larger than the static value of mode II fracture toughness and a load rate effect is observed. Specimen size effects in off-axis compression tests are studied as well by conducting experiments with small block off-axis specimens of low modulus S2 glass fiber reinforced composites and high modulus AS4 carbon fiber reinforced composites. It was found that the off-axis compressive strength of the glass/epoxy composite decreased by a small amount (<5%) when increasing either specimen width or thickness. However, an appreciable reduction in off-axis compressive strength of the high modulus carbon/epoxy composite was observed as specimen width or thickness increased with lapped specimens. But when a

  4. Compressive strength of esthetic restorative materials polymerized with quartz-tungsten-halogen light and blue LED

    Scientific Electronic Library Online (English)

    Cecy Martins, Silva; Katia Regina Hostilio Cervantes, Dias.

    Full Text Available Este estudo comparou a resistência à compressão de uma resina composta e de um compômero, fotoativados com luz halógena convencional de quarto-tungstênio (QTH) (XL 300, 3M/SPE) e LED azul (SmartLite PS; Dentsply/De Trey). Foram confeccionados 40 espécimes em forma de disco usando uma matriz bipartid [...] a de politetrafluoretileno (4,0 mm de diâmetro x 8,0 mm de altura) em que o material foi inserido incrementalmente. O tempo de polimerização de cada incremento foi de 40 s para a luz halógena convencional e de 10 s para o LED. Os espécimes foram aleatoriamente alocados em 4 grupos (n=10), de acordo com a fonte de luz e com o material restaurador. Depois de armazenadas em água destilada a 37°C ± 2°C por 24 h, a resistência à compressão dos espécimes foi testada em uma máquina universal de ensaios com célula de carga de 500 kgf a uma velocidade de carregamento de 0,5 mm/min. Os dados (em MPa) foram analisados estatisticamente por ANOVA e teste de Student-Newman-Keuls (p0,05) em sua resistência à compressão quando comparada à fotopolimerização com LED. Contudo, a fotopolimerização do compômero com a luz halógena resultou em uma resistência à compressão significativamente maior que a feita o LED (p>0,05). A resina composta apresentou resistência à compressão significativamente maior que a do compômero, independente da fonte de luz. Concluiu-se que a resistência à compressão dos materiais fotopolimerizados com luz halógena e LED foi influenciada pela densidade de energia empregada e pela composição química dos materiais restauradores estéticos. Abstract in english This study compared the compressive strength of a composite resin and compomer photoactivated with a conventional quartz-tungsten halogen-light (XL 3000, 3M/SPE) and a blue light-emitting diode (LED) (SmartLite PS; Dentsply/De Trey). Forty disc-shaped specimens were prepared using a split polytetraf [...] luoroethylene matrix (4.0 mm diameter x 8.0 mm hight) in which the materials were inserted incrementally. The curing time of each increment was of 40 s with the QTH and 10 s with the LED. The specimens were randomly assigned to 4 groups (n=10), according to the light source and the restorative material. After storage in distilled water at 37oC ± 2oC for 24 h, the specimens was tested in compressive strength in a universal testing machine with load cell of 500 kgf running at a crosshead speed of 0.5 mm/min. Data (in MPa) were analyzed statistically by ANOVA and Student-Newman-Keuls test (p0.05) in the compressive strength when compared to light curing with the LED source. However, light curing of the compomer with the QTH source resulted in significantly higher compressive strength than the use of the LED unit (p>0.05). The composite resin presented significantly higher (p>0.05) compressive strength than the compomer, regardless of the light source. In conclusion, the compressive strength of the tested materials photoactivated with a QTH and a LED light source was influenced by the energy density employed and the chemical composition of the esthetic restorative materials.

  5. Comparison of Elastic Modulus and Compressive Strength of Ariadent and Harvard Polycarboxylate Cement and Vitremer Resin Modified Glass Ionomer

    Directory of Open Access Journals (Sweden)

    Ahmadian Khoshemehr Leila

    2009-09-01

    Full Text Available Background: Luting agents are used to attach indirect restoration into or on the tooth. Poor mechanical properties of cement may be a cause of fracture of this layer and lead to caries and restoration removal. The purpose of this study was to compare the elastic modulus and compressive strength of Ariadent (A Poly and Harvard polycarboxylate (H Poly cements and Vitremer resin modified glass ionomer (RGl.Materials & Methods: In this experimental study 15 specimens were prepared form each experimental cement in Laboratory of Tehran Oil Refining Company. The cylindrical specimens were compressed in Instron machine after 24 hours. Elastic modulus and compressive strength were calculated from stress/strain curve of each specimen. One way ANOVA and Tukey tests were used for statistical analysis and P values<0.05 were considered to be statistically significant.Results: The mean elastic modulus and mean compressive strength were 2.2 GPa and 87.8MPa in H poly, 2.4 GPa and 56.5 MPa in A Poly, and 0.8GPa and 105.6 MPa in RGI, respectively. Statistical analysis showed that compressive strength and elastic modulus of both polycarboxylate cements were significantly different from hybrid ionomer (P<0.05, but the difference between elastic modulus of two types of polycarboxilate cements was not statistically significant. Compressive strength of two polycarboxilate cements were significantly different (P<0.05. Conclusion: An ideal lutting agent must have the best mechanical properties. Between the tested luttins RGl cement had the lowest elastic modulus and the highest compressive strength, but the A poly cement had the highest elastic modulus and the lowest compressive strength. Therefore none of them was the best.

  6. Durability and compressive strength of blast furnace slag-based cement grout for special geotechnical applications

    Directory of Open Access Journals (Sweden)

    Ortega, J. M.

    2014-03-01

    Full Text Available Special foundations, most prominently micropiles and soil anchors, are frequently used in construction today. In Spain, the grout for these special technical applications is generally prepared with portland cement, although the codes and standards in place stipulate only the minimum compressive strength required, with no mention of cement type. Those texts also establish a range of acceptable water:cement ratios. In the present study, durability and compressive strength in cement grout prepared with blast furnace slag cement at different w/c ratios are characterised and compared to the findings for a reference portland cement grout. The results show that slag grout exhibits greater durability than the portland cement material and complies with the compressive strength requirements laid down in the respective codes.Actualmente es muy frecuente el empleo de cimentaciones especiales, entre las que destacan los micropilotes y los anclajes. En España, las lechadas de cemento para estos trabajos geotécnicos especiales se preparan habitualmente con cemento Portland, aunque las diferentes normativas al respecto no restringen el tipo de cemento a emplear, siempre que se alcance una determinada resistencia a compresión. Respecto a la dosificación de las lechadas, la normativa permite emplear diferentes relaciones agua/cemento dentro de un determinado rango. En vista de ello, en este trabajo se han caracterizado las propiedades de durabilidad y resistencia a compresión de lechadas de cemento preparadas con un cemento con escoria de alto horno y con diferentes relaciones a/c, tomando como referencia de comportamiento lechadas de cemento Portland. El uso de un cemento con escoria conlleva una mejora en la durabilidad de las lechadas, cumpliendo los requisitos de resistencia a compresión establecidos por la normativa.

  7. Palm fibers influence the compressive strength and CBR on soil cement

    OpenAIRE

    Suroso, P.; Samang, L.,; Tjaronge, W.; RAMLI M

    2013-01-01

    Soil cement is a mixture of soil with cement. The usefulness of this mixture is very meaningful to increase the carrying capacity of the land. Weakness that accurs from this mix is the process by cement shrinkage and hydration. This process can lead to cracks and effect the compressive strength and carrying capacity of the soil cement. With the addition of fiber in this mix can reduce or even eliminate the process of shrinkage and hydration. Natural fibers as a mixture of palm fib...

  8. Microstructure characteristics of concrete incorporating metakaolin and PVA fibers and influence on the compressive strength

    Science.gov (United States)

    Khan, Sadaqat Ullah; Shafiq, Nasir; Ayub, Tehmina

    2015-07-01

    In this paper, microstructure of concrete is investigated using metakaolin (MK) as cement replacing material and Polyvinyl Alcohol (PVA) fibers. Total ten (10) mixes of concrete are examined by varying PVA fiber aspect ratio. It was found that MK refines the pore structure, improves interfacial transition zone (ITZ) due to its pozzolanic effects, reduces portlandite (Ca(OH)2) content and bridges the gap between matrix and aggregates due to finer particle size. Due to improvement in ITZ, the compressive strength was improved. There was no indication of Ca(OH)2 around the PVA fibers in the presence of MK and the interface between the fiber and matrix was observed very narrow.

  9. Effect of Different Mixing and Placement Methods on the Compressive Strength of Calcium-Enriched Mixture

    OpenAIRE

    Sahebi, Safoora; Sadatshojaee, Nooshin; Jafari, Zahra

    2015-01-01

    Introduction: The aim of this experimental laboratory study was to evaluate the effect of different mixing and placement techniques on compressive strength (CS) of calcium-enriched mixture (CEM) cement. Methods and Materials: CEM powder was mixed with its liquid either by hand mixing or amalgamator mixing. The mixture was loaded to cylindrical acrylic molds with 6.0±0.1 mm height and 4.0±1 mm diameter. Half of the specimens in each group were selected randomly and ultrasonic energy was applie...

  10. Soft computing methods for estimating the uniaxial compressive strength of intact rock from index tests.

    Czech Academy of Sciences Publication Activity Database

    Mishra, A. Deepak; Srigyan, M.; Basu, A.; Rokade, P. J.

    2015-01-01

    Ro?. 80, December 2015 (2015), s. 418-424. ISSN 1365-1609 Institutional support: RVO:68145535 Keywords : uniaxial compressive strength * rock indices * fuzzy inference system * artificial neural network * adaptive neuro-fuzzy inference system Subject RIV: DH - Mining, incl. Coal Mining Impact factor: 1.686, year: 2014 http://ac.els-cdn.com/S1365160915300708/1-s2.0-S1365160915300708-main.pdf?_tid=318a7cec-8929-11e5-a3b8-00000aacb35f&acdnat=1447324752_2a9d947b573773f88da353a16f850eac

  11. Comparative evaluation of compressive strength and flexural strength of conventional core materials with nanohybrid composite resin core material an in vitro study.

    Science.gov (United States)

    Jayanthi, Narasimha; Vinod, V

    2013-09-01

    Several dental materials have been used for core build-up procedures. Most of these materials were not specifically developed for this purpose, but as a consequence of their properties, have found application in core build-up procedures. Improvements in composites and the development of nanocomposites have led to their use as a core build up material due to their superior mechanical properties, optical properties and ease of handling. However it is not clear if they have better mechanical properties than the conventional core build up materials like amalgam, GIC and dual cure composite core build up material. The strength of the core material is very important and this study was undertaken to compare the mechanical properties of materials used for direct core foundations. The differences between the compressive strength and flexural strength of Filtek Z350 nanocomposite with conventional core build up materials like Amalgam, Vitremer GIC and Fluorocore were tested. Cylindrical plexi glass split molds of dimension 6 ± 1 mm [height] x4 ± 1 mm [diameter] were used to fabricate 15 samples of each core material for testing the compressive strength and rectangular plexi glass split molds of dimension 25 ± 1 mm [length] x 2 ± 1 mm[height] x2 ± 1 mm [width] used for fabricating samples for flexural strength. The samples were stored a water bath at 250 °C for 24 h before testing. The samples were tested using a Universal Instron testing machine. The results of the study showed that Fluorocore had the highest compressive strength and flexural strength followed by Filtek Z350 [nanocomposite] Amalgam had the least flexural strength and Vitremer GIC had the least compressive strength. Thus flurocore and nanocomposite are stronger than other core build up materials and hence should be preferred over other conventional core build up materials in extensively damaged teeth. PMID:24431748

  12. Ultimate uniaxial compressive strength of stiffened panel with opening under lateral pressure

    Directory of Open Access Journals (Sweden)

    Yu Chang-Li

    2015-06-01

    Full Text Available This paper concentrated on the ultimate uniaxial compressive strength of stiffened panel with opening under lateral load and also studied the design-oriented formulae. For this purpose, three series of well executed experiments on longitudinal stiffened panel with rectangular opening subjected to the combined load have been selected as test models. The finite element analysis package, ABAQUS, is used for simulation with considering the large elasticplastic deflection behavior of stiffened panels. The feasibility of the numerical procedure is verified by a good agreement of experimental results and numerical results. More cases studies are executed employing nonlinear finite element method to analyze the influence of design variables on the ultimate strength of stiffened panel with opening under combined pressure. Based on data, two design formulae corresponding to different opening types are fitted, and accuracy of them is illustrated to demonstrate that they could be applied to basic design of practical engineering structure.

  13. Ultimate uniaxial compressive strength of stiffened panel with opening under lateral pressure

    Science.gov (United States)

    Yu, Chang-Li; Feng, Ji-Cai; Chen, Ke

    2015-06-01

    This paper concentrated on the ultimate uniaxial compressive strength of stiffened panel with opening under lateral load and also studied the design-oriented formulae. For this purpose, three series of well executed experiments on longitudinal stiffened panel with rectangular opening subjected to the combined load have been selected as test models. The finite element analysis package, ABAQUS, is used for simulation with considering the large elasticplastic deflection behavior of stiffened panels. The feasibility of the numerical procedure is verified by a good agreement of experimental results and numerical results. More cases studies are executed employing nonlinear finite element method to analyze the influence of design variables on the ultimate strength of stiffened panel with opening under combined pressure. Based on data, two design formulae corresponding to different opening types are fitted, and accuracy of them is illustrated to demonstrate that they could be applied to basic design of practical engineering structure.

  14. Dynamics of unconfined spherical flames

    CERN Document Server

    Leblanc, Louis; Dennis, Kadeem; Zhe,; Liang,; Radulescu, Matei I

    2012-01-01

    Using the soap bubble technique, we visualize the dynamics of unconfined hydrogen-air flames using high speed schlieren video. We show that for sufficiently weak mixtures, i.e., low flame speeds, buoyancy effects become important. Flame balls of a critical dimension begin to rise. The experiments are found in very good agreement with the scaling laws proposed by Zingale and Dursi. We report the results in a fluid dynamics video.

  15. Effect of isothermal annealing on the compressive strength of a ZrAlNiCuNb metallic glass

    International Nuclear Information System (INIS)

    Research highlights: ? Only structural relaxation happens during annealing at the temperature below Tg. ? Nanocrystallization happens during annealing at the temperature above Tg. ? The compressive strength increases with annealing time up to 20 min. ? The compressive strength decreases with annealing time after 20 min. - Abstract: The effects of isothermal annealing on the microstructures and compressive strength of a Zr56Al10.9Ni4.6Cu27.8Nb0.7 bulk metallic glass (BMG) have been studied using X-ray diffraction, scanning electron microscopy and compression tests. It has been shown that only structural relaxation happens during annealing at the temperature below Tg (glass transition temperature), while both structural relaxation and nanocrystallization happen during annealing at the temperature above Tg. Compression tests indicated that the strength of the BMG increases with annealing time at 437 deg. C up to 20 min, after which the strength starts to decrease. The strength evolution of the BMG with the annealing time is due to combined effects of the variations of the free volume and nanocrystals.

  16. Characteristic compression strength of a brickwork masonry starting from the strength of its components. Experimental verification of analitycal equations of european codes

    Directory of Open Access Journals (Sweden)

    Rolando, A.

    2006-09-01

    Full Text Available In this paper the compression strength of a clay brickwork masonry bound with cement mortar is analyzed. The target is to obtain the characteristic compression strength of unreinforced brickwork masonry. This research try to test the validity of the analytical equations in European codes, comparing the experimental strength with the analytically obtained from the strength of its components (clay brick and cement mortar.En este artículo se analiza la resistencia a compresión de una fábrica de ladrillo cerámico, asentado con mortero de cemento.El objetivo es obtener la resistencia característica a compresión de la fábrica sin armar.La investigación comprueba la fiabilidad de las expresiones analíticas existentes en la normativa europea, comparando la resistencia obtenida experimentalmente con la obtenida analíticamente, a partir de la resistencia de sus componentes (ladrillo cerámico y mortero de cemento.

  17. In-Situ Welding Carbon Nanotubes into a Porous Solid with Super-High Compressive Strength and Fatigue Resistance.

    Science.gov (United States)

    Lin, Zhiqiang; Gui, Xuchun; Gan, Qiming; Chen, Wenjun; Cheng, Xiaoping; Liu, Ming; Zhu, Yuan; Yang, Yanbing; Cao, Anyuan; Tang, Zikang

    2015-01-01

    Carbon nanotube (CNT) and graphene-based sponges and aerogels have an isotropic porous structure and their mechanical strength and stability are relatively lower. Here, we present a junction-welding approach to fabricate porous CNT solids in which all CNTs are coated and welded in situ by an amorphous carbon layer, forming an integral three-dimensional scaffold with fixed joints. The resulting CNT solids are robust, yet still highly porous and compressible, with compressive strengths up to 72?MPa, flexural strengths up to 33?MPa, and fatigue resistance (recovery after 100,000 large-strain compression cycles at high frequency). Significant enhancement of mechanical properties is attributed to the welding-induced interconnection and reinforcement of structural units, and synergistic effects stemming from the core-shell microstructures consisting of a flexible CNT framework and a rigid amorphous carbon shell. Our results provide a simple and effective method to manufacture high-strength porous materials by nanoscale welding. PMID:26067176

  18. Dynamic shear strength of improved soil with B-type blast-furnace cement

    International Nuclear Information System (INIS)

    It is attempted to apply the improved soil using cement materials as the hardening agent to the foundation ground of the important buildings for electric power plants. The current design procedure of the improved ground is based on the static strength such as the unconfined compressive strength of the improved soil. However, it is not clear whether the static strength is relevant to seismic designs where the effects of the cyclic loading induced by the earthquake shall be considered. Hence, the authors studied the dynamic strength of the improved soil in comparison with the static strength, by executing a series of the cyclic triaxial tests with different loading frequencies and the consolidated-undrained triaxial compression tests (CUB tests) with different axial strain rates. The tested soil specimens which have the unconfined compressive strength of about 5 MPa were made in laboratory using the mixture of a dredged marine clayey soil, a B-type blast-furnace cement (300 kg/m3) and water. Both of the CUB tests and the cyclic triaxial tests showed similar results with respect to the relationships between the strength and the strain rate. The larger the compressive strain rate was, the higher the strength became. It is concluded that the static strength could be used as a sufficiently safe value in seismic designs since the strain rate of the cyclic loading induced by the earthquake is much larger than that of the static test. (author)

  19. Material strength and inelastic deformation of silicon carbide under shock wave compression

    Energy Technology Data Exchange (ETDEWEB)

    Feng, R.; Raiser, G.F.; Gupta, Y.M. [Shock Dynamics Center and Department of Physics, Washington State University, Pullman, Washington 99164-2814 (United States)

    1998-01-01

    In-material, lateral, manganin foil gauge measurements were obtained in dense polycrystalline silicon carbide (SiC) shocked to peak longitudinal stresses ranging from 10{endash}24 GPa. The lateral gauge data were analyzed to determine the lateral stresses in the shocked SiC and the results were checked for self-consistency through dynamic two-dimensional computations. Over the stress range examined, the shocked SiC has an extremely high strength: the maximum shear stress supported by the material in the shocked state increases from 4.5 GPa at the Hugoniot elastic limit (HEL) of the material (11.5 GPa) to 7.0 GPa at stresses approximately twice the HEL. The latter value is 3.7{percent} of the shear modulus of the material. The elastic{endash}inelastic transition in the shocked SiC is nearly indistinctive. At stresses beyond twice the HEL, the data suggest a gradual softening with increasing shock compression. The post-HEL material strength evolution resembles neither catastrophic failure due to massive cracking nor classical plasticity response. Stress confinement, inherent in plane shock wave compression, contributes significantly to the observed material response. The results obtained are interpreted qualitatively in terms of an inhomogeneous deformation mechanism involving both in-grain microplasticity and highly confined microfissures. {copyright} {ital 1998 American Institute of Physics.}

  20. Effect of mix proportion of high density concrete on compressive strength, density and radiation absorption

    International Nuclear Information System (INIS)

    To prevent radiation leaks at nuclear reactors, high-density concrete is used as an absorbent material for radiation from spreading into the environment. High-density concrete is a mixture of cement, sand, aggregate (usually high-density minerals) and water. In this research, hematite stone is used because of its mineral density higher than the granite used in conventional concrete mixing. Mix concrete in this study were divided into part 1 and part 2. In part 1, the concrete mixture is designed with the same ratio of 1: 2: 4 but differentiated in terms of water-cement ratio (0.60, 0.65, 0.70, 0.75, 0.80 ). Whereas, in part 2, the concrete mixture is designed to vary the ratio of 1: 1: 2, 1: 1.5: 3, 1: 2: 3, 1: 3: 6, 1: 2: 6 with water-cement ratio (0.7, 0.8, 0.85, 0.9). In each section, the division has also performed in a mixture of sand and fine sand hematite. Then, the physical characteristics of the density and the compressive strength of the mixture of part 1 and part 2 is measured. Comparisons were also made in terms of absorption of radiation by Cs-137 and Co-60 source for each mix. This paper describes and discusses the relationship between the concrete mixture ratio, the relationship with the water-cement ratio, compressive strength, density, different mixture of sand and fine sand hematite. (author)

  1. Influence of the waste glass in the axial compressive strength of Portland cement concrete

    International Nuclear Information System (INIS)

    In this work, was studied the influence of the incorporation of waste glass, coming from the stage of thinning and polishing of a company of thermal glass treatments, in the axial compressive strength of Portland cement concrete. The coarse and ground aggregates used was crushed stone and sand, respectively. For production of the concrete, percentages of glass residues of 5%, 10% and 20% had been used in substitution to the sand, and relations water/cement (a/c) 0,50, 0,55 and 0,58. The cure of the test bodies was carried through in 7, 14 and 28 days. The statistics analysis of the results was carried out through of the analysis of variance for each one of the cure times. From the results of the compressive strength of the concrete, it could be observed that the concrete has structural application for the relation a/c 0,5, independently of waste glass percentage used, and for the relation a/c 0,55 with 20% of waste glass. (author)

  2. The effects of aging on compressive strength of low-level radioactive waste form samples

    International Nuclear Information System (INIS)

    The Field Lysimeter Investigations: Low-Level Waste Data Base Development Program, funded by the US Nuclear Regulatory Commission (NRC), is (a) studying the degradation effects in organic ion-exchange resins caused by radiation, (b) examining the adequacy of test procedures recommended in the Branch Technical Position on Waste Form to meet the requirements of 10 CFR 61 using solidified ion-exchange resins, (c) obtaining performance information on solidified ion-exchange resins in a disposal environment, and (d) determining the condition of liners used to dispose ion-exchange resins. Compressive tests were performed periodically over a 12-year period as part of the Technical Position testing. Results of that compressive testing are presented and discussed. During the study, both portland type I-II cement and Dow vinyl ester-styrene waste form samples were tested. This testing was designed to examine the effects of aging caused by self-irradiation on the compressive strength of the waste forms. Also presented is a brief summary of the results of waste form characterization, which has been conducted in 1986, using tests recommended in the Technical Position on Waste Form. The aging test results are compared to the results of those earlier tests. 14 refs., 52 figs., 5 tabs

  3. Effect of high volume of fly ash from 5 sources on compressive strength and acid resistance of concrete

    Directory of Open Access Journals (Sweden)

    Vivatanachang, N.

    2004-03-01

    Full Text Available The purpose of this research was to examine the effect of high volume of fly ash from various sources on compressive strength and acid resistance of concrete. Fly ashes from 5 sources were collected and classified by an air classifier into 3 groups of different degree of fineness; low, medium, and high fineness. Portland cement type I was replaced by fly ash at the rate of 50% by weight of cementitious materials (Portland cement type I and fly ash to cast concrete cylinders of 10 cm in diameter and 20 cm in height. After fly ash concreteswere cured in water for 28 days, they were tested to determine the compressive strength. In addition, the specimens were immersed in 3% of sulfuric acid solution and the weight losses of concretes were measured from 3 to 90 days. It was found that the compressive strengths of fly ash concretes were more than 77% of the control concrete when the high fineness fly ashes were used. Each source of the fly ash had different effect on the compressive strength as well as on the sulfuric acid resistance of concrete. The compressive strength of fly ash concrete was improved with the use of high fineness fly ash; however, the sulfuric acid resistance of the concrete tended to decrease as the fineness of fly ash increased.

  4. Ultimate tensile strength testing campaign on ITER pre-compression ring mock-ups

    International Nuclear Information System (INIS)

    ENEA has developed and characterized a high strength glass fibre-epoxy composite as reference material for the manufacture of the two sets of 3 pre-compression rings located at top and bottom of the inner straight leg region of the ITER Toroidal Field (TF) coils. These rings will provide a radial force of about 70 MN/coil at cryogenic temperature pulling the TF coils into contact and reducing toroidal tension in the four outer intercoil structures. The paper describes the ultimate tensile strength (UTS) testing campaign carried out at ENEA Frascati laboratories on six different rings manufactured winding S2 glass fibers on a diameter of 1 m (1/5 of the full scale) by both vacuum pressure epoxy impregnation and filament wet winding techniques. The volumetric glass content was around 70%. The rings were expanded with radial steps of 0.1 mm into a dedicated hydraulic testing machine consisting of 18 radial actuators working in position control with a total capability of 1000 tons. All the mock-ups showed very high tensile strength (1550 MPa is the average of the mean hoop stresses at failure) and a practically constant tensile modulus. The test results are reported and discussed.

  5. Effect of Relative Proportion of Pozzolana on Compressive Strength of Concrete Under Different Curing Conditions

    Directory of Open Access Journals (Sweden)

    B. Bhattacharjee

    2008-02-01

    Full Text Available In this experimental and analytic research, the effect of curing regime on various combinations of silica fume and fly ash was investigated in terms of development of compressive strength. Over 24 mixes were prepared with the water-to-binder ratios of 0.45, 0.35 and 0.25 and with differing percentage of additives used as a combination of 2 or 3 binders. The specimens were subjected to five different curing regimes ranging from continuously water cured to continuously air cured. Results show that it is economical to use a combination of silica fume and fly ash rather than using only silica fume for attaining the same strength level. Poor curing condition adversely affect the strength characteristics of pozzolanic concrete than that of OPC concrete. For silica fume concrete, it is necessary to apply water curing for the initial 7 days to explore pozzolainc activity but it is imperative to cure the fly ash concrete for an extended period to utilize its full potential.

  6. Compressibility and shear strength of municipal solid waste under short-term leachate recirculation operations.

    Science.gov (United States)

    Reddy, Krishna R; Gangathulasi, Janardhanan; Parakalla, Naveen S; Hettiarachchi, Hiroshan; Bogner, Jean E; Lagier, Thomas

    2009-09-01

    This paper describes a comprehensive laboratory study performed to investigate the compressibility and shear strength properties of 1.5-year-old municipal solid waste (MSW) exhumed from a landfill cell where low amounts of leachate were recirculated. The study results are compared with results from a previous study on fresh MSW collected from the same landfill and data from previous studies with known MSW age to assess the variation in properties due to degradation. Laboratory testing was conducted on shredded landfilled and fresh MSW that consisted of similar particle-size distribution, with maximum particle size less than 40 mm and approximately 80% of the waste consisting of particles ranging from 10 to 20 mm. Standard Proctor, compressibility, direct shear, and triaxial consolidated undrained (CU) shear tests were conducted in general accordance with the American Society of Testing and Materials Standard Procedures. These tests were conducted with samples at an in-situ moisture content of 44% (dry weight basis) as well as elevated moisture contents of 60, 80 and 100% (dry weight basis). Standard Proctor compaction tests yielded a maximum dry density of 600 kg/m(3) at 77% optimum moisture content for landfilled MSW compared to the 420 kg/m(3) maximum dry density at 70% optimum moisture content for fresh MSW. Compression ratio values for landfilled MSW varied in a close range of 0.19-0.24 with a slight increasing trend with increase in moisture content; however, for fresh waste they were in the close range of 0.24-0.33 with no definitive correlation with moisture content. Based on direct shear tests, drained cohesion and friction angle were varied in the range of 12-64 kPa and 31-35 degrees for landfilled MSW and 31-64 kPa and 26-30 degrees for fresh MSW. Neither cohesion nor friction angle demonstrated any correlation with the moisture content. Based on triaxial CU tests, the average total strength parameters (TSP) were found to be 39 kPa and 12 degrees for landfilled MSW and 32 kPa and 12 degrees for fresh MSW, while effective strength parameters (ESP) were 34 kPa and 23 degrees for landfilled MSW and 32 kPa and 16 degrees for fresh MSW. This study was limited to small-scale laboratory testing using MSW samples with the specimen size relative to the maximum particle size in the range of 1.6 to 2.6; therefore, large-scale laboratory and field studies are recommended to systematically assess the influence of composition, particle size distribution and specimen size on the geotechnical properties of MSW. PMID:19423596

  7. Statistical analysis of the effective factors on the 28 days compressive strength and setting time of the concrete.

    Science.gov (United States)

    Abolpour, Bahador; Mehdi Afsahi, Mohammad; Hosseini, Saeed Gharib

    2015-09-01

    In this study, the effects of various factors (weight fraction of the SiO2, Al2O3, Fe2O3, Na2O, K2O, CaO, MgO, Cl, SO3, and the Blaine of the cement particles) on the concrete compressive strength and also initial setting time have been investigated. Compressive strength and setting time tests have been carried out based on DIN standards in this study. Interactions of these factors have been obtained by the use of analysis of variance and regression equations of these factors have been obtained to predict the concrete compressive strength and initial setting time. Also, simple and applicable formulas with less than 6% absolute mean error have been developed using the genetic algorithm to predict these parameters. Finally, the effect of each factor has been investigated when other factors are in their low or high level. PMID:26425360

  8. Distribution of the X-ray density, compressive and tensile breaking strength in the human femoral shaft

    International Nuclear Information System (INIS)

    105 cross sections of 21 femora (13 male, 8 female) were examined with respect to X-ray density, compressive and tensile breaking strength. On X-ray photographs of each specimen, the density measurements were obtained with photographic equidenses in 4 sites: anterior, medial, posterior and lateral. Then the compressive and tensile breaking strength were determined on 817 standardized samples from the same sites.The results show, that the X-ray density, compressive and tensile breaking strength respectively represent characteristic features of their distributions, and that these three factors are correlated with one another. From these facts it is derived, that the resultant force in the femoral shaft may be within the cross section of femur, and that the functional adaptation of the bone on its mechanical stress is reached by several factors of bone materials at the same time. (author)

  9. Comparison of the compressive strength of impregnated and nonimpregnated eucalyptus subjected to two different pressures and impregnation times

    Directory of Open Access Journals (Sweden)

    Waldemir Rodrigues

    2004-06-01

    Full Text Available The durability of wood is affected by several factors. For this reason, much research has been done on a variety of chemical compounds for impregnating wood, aimed at preserving it while simultaneously improving its properties. Recent studies of the properties of impregnated wood have demonstrated the possibility of substantially improving its mechanical characteristics. Thus, the purpose of this work was to compare the strength to parallel compression of wooden fibers (Eucalyptus grandis, both nonimpregnated and impregnated with a monocomponent resin, from the standpoint of pressure and impregnation time, aiming at its structural utilization. The results demonstrate that the compressive strength of impregnated test specimens is greater than that of nonimpregnated ones, indicating that monocomponent polyurethane resin can be considered suitable for impregnating wood, since it increases the compressive strength of eucalyptus.

  10. Statistical analysis of the effective factors on the 28 days compressive strength and setting time of the concrete

    Directory of Open Access Journals (Sweden)

    Bahador Abolpour

    2015-09-01

    Full Text Available In this study, the effects of various factors (weight fraction of the SiO2, Al2O3, Fe2O3, Na2O, K2O, CaO, MgO, Cl, SO3, and the Blaine of the cement particles on the concrete compressive strength and also initial setting time have been investigated. Compressive strength and setting time tests have been carried out based on DIN standards in this study. Interactions of these factors have been obtained by the use of analysis of variance and regression equations of these factors have been obtained to predict the concrete compressive strength and initial setting time. Also, simple and applicable formulas with less than 6% absolute mean error have been developed using the genetic algorithm to predict these parameters. Finally, the effect of each factor has been investigated when other factors are in their low or high level.

  11. The unconfined quarks and gluons

    International Nuclear Information System (INIS)

    The consequences of the lepton-hadron gauge unification hypothesis with unconfined quarks and gluons being the hall-mark are discussed. Quark and gluon decays into leptons are shown to provide a new source of multileptonic production in NN, ?N and ?N collisions. A theorem is stated and proved which highlights the differences between the dynamics of gauge versus non-gauge 1- particles. Empirical manifestations of gauge coloured mesons are discussed. The question of exact confinement or not is concluded to be in the end an empirical one and must be settled in the laboratory

  12. Dynamic shear strength of S2 glass fiber reinforced polymer composites under shock compression

    Science.gov (United States)

    Yuan, Fuping; Tsai, Liren; Prakash, Vikas; Dandekar, Dattatraya P.; Rajendran, A. M.

    2008-05-01

    In the present paper, a series of plate impact shock-reshock and shock-release experiments were conducted to study the critical shear strength of a S2 glass fiber reinforced polymer (GRP) composite under shock compression levels ranging from 0.8 to 1.8 GPa. The GRP was fabricated at ARL, Aberdeen, using S2 glass woven roving in a Cycom 4102 polyester resin matrix. The experiments were conducted by using an 82.5 mm bore single-stage gas gun at Case Western Reserve University. In order to conduct shock-reshock and shock-release experiments a dual flyer plate assembly was utilized. The shock-reshock experiments were conducted by using a projectile faced with GRP and backed with a relatively high shock impedance Al 6061-T6 plate; while for the shock-release experiments the GRP was backed by a relatively lower impedance polymethyl methacrylate backup flyer plate. A multibeam velocity interferometer was used to measure the particle velocity profile at the rear surface of the target plate. By using self-consistent technique procedure described by Asay and Chabbildas [Shock Waves and High-Strain-Rate Phenomena, in Metals, edited by M. M. Myers and L. E. Murr (Plenum, New York, 1981), pp. 417-431], the critical shear strength of the GRP (2?c) was determined for impact stresses in the range of 0.8 to 1.8 GPa. The results show that the critical shear strength of the GRP is increased from 0.108 GPa to 0.682 GPa when the impact stress is increased from 0.8 to 1.8 GPa. The increase in critical shear strength may be attributed to rate-dependence and/or pressure dependent yield behavior of the GRP.

  13. The effect of different parameters on the development of compressive strength of oil palm shell geopolymer concrete.

    Science.gov (United States)

    Kupaei, Ramin Hosseini; Alengaram, U Johnson; Jumaat, Mohd Zamin

    2014-01-01

    This paper presents the experimental results of an on-going research project on geopolymer lightweight concrete using two locally available waste materials--low calcium fly ash (FA) and oil palm shell (OPS)--as the binder and lightweight coarse aggregate, respectively. OPS was pretreated with three different alkaline solutions of sodium hydroxide (NaOH), potassium hydroxide, and sodium silicate as well as polyvinyl alcohol (PVA) for 30 days; afterwards, oil palm shell geopolymer lightweight concrete (OPSGPC) was cast by using both pretreated and untreated OPSs. The effect of these solutions on the water absorption of OPS, and the development of compressive strength in different curing conditions of OPSGPC produced by pretreated OPS were investigated; subsequently the influence of NaOH concentration, alkaline solution to FA ratio (A/FA), and different curing regimes on the compressive strength and density of OPSGPC produced by untreated OPS was inspected. The 24-hour water absorption value for OPS pretreated with 20% and 50% PVA solution was about 4% compared to 23% for untreated OPS. OPSGPC produced from OPS treated with 50% PVA solution produced the highest compressive strength of about 30?MPa in ambient cured condition. The pretreatment with alkaline solution did not have a significant positive effect on the water absorption of OPS aggregate and the compressive strength of OPSGPC. The result revealed that a maximum compressive strength of 32?MPa could be obtained at a temperature of 65°C and curing period of 4 days. This investigation also found that an A/FA ratio of 0.45 has the optimum amount of alkaline liquid and it resulted in the highest level of compressive strength. PMID:25531006

  14. Estimating the modulus of elasticity of the rock material from compressive strength and unit weight

    Scientific Electronic Library Online (English)

    I., Ocak.

    2008-10-01

    Full Text Available The modulus of elasticity of rock material (Ei) is an important rock property that is used as an input parameter in the design stage of engineering projects such as dam and tunnel constructions, mining excavations, and so forth. However, determination of the modulus of elasticity is sometimes diffic [...] ult to obtain by laboratory tests because high-quality cores are required. For this reason, empirical methods for predicting the modulus of elasticity of rock material have been popular research topics in recently published literature. In this study, the relationships between the uniaxial compressive strength (UCS), unit weight (y) and modulus of elasticity for different types of rocks were analysed by using 177 data obtained from laboratory tests carried out on cores obtained from drill holes within the area of the Kad?köy-Kartal Metro line (Istanbul, Turkey).

  15. Measurement of sound velocities and shear strength of cerium under shock compression

    International Nuclear Information System (INIS)

    Sound velocity in shock-compressed cerium was measured over the pressure range of 35-140 GPa using the rarefaction overtake technique. Indicator liquids carbogal and tetrachloromethane were used. The samples were loaded with planar shock wave generators using powerful high explosives (HE). Luminescence of the liquid indicators was recorded by optical gauges based on photodiode 'FD 256'. For the pressure range of 13-35 GPa, sound velocity was measured in cerium samples using the counter release method with manganin-based piezoresistive gauges. From the measured longitudinal and bulk sound velocities, Poisson's ratio and shear strength of cerium were determined. The melting boundary on the shock Hugoniot was estimated. Experimental data is compared with calculation results

  16. Electrical impedance spectroscopy measurements to estimate the uniaxial compressive strength of a fault breccia

    Indian Academy of Sciences (India)

    Sair Kahraman; Michael Alber

    2014-10-01

    Fault breccias are usually not suitable for preparing smooth specimens or else the preparation of such specimens is tedious, time consuming and expensive. To develop a predictive model for the uniaxial compressive strength (UCS) of a fault breccia from electrical resistivity values obtained from the electrical impedance spectroscopy measurements, twenty-four samples of a fault breccia were tested in the laboratory. The UCS values were correlated with corresponding resistivity values and a strong correlation between them could not be found. However, a strong correlation was found for the samples having volumetric block proportion (VBP) of 25–75%. In addition, it was seen that VBP strongly correlated with resistivity. It was concluded that the UCS of the tested breccia can be estimated from resistivity for the samples having VBP of 25–75%.

  17. Hot/Wet Open Hole Compression Strength of Carbon/Epoxy Laminates for Launch Vehicle Applications

    Science.gov (United States)

    Nettles, Alan T.

    2009-01-01

    This Technical Memorandum examines the effects of heat and absorbed moisture on the open hole compression strength of carbon/epoxy laminates with the material and layup intended for the Ares I composite interstage. The knockdown due to temperature, amount of moisture absorbed, and the interaction between these two are examined. Results show that temperature is much more critical than the amount of moisture absorbed. The environmental knockdown factor was found to be low for this material and layup and thus obtaining a statistically significant number for this value needs to be weighed against a program s cost and schedule since basis values, damage tolerance, and safety factors all contribute much more to the overall knockdown factor.

  18. The Effect of Curing Conditions on the Compressive Strength of White Concrete Produced with Various Dosages

    Directory of Open Access Journals (Sweden)

    Mücteba Uysal

    2011-12-01

    Full Text Available The white cement, which has been used more widely in aesthetic and decorative applications in Turkey and the use of white cement has not widely common yet in constructional applications. In this study white cement, white calcareous aggregate and marble powder are used and produced white concrete. Furthermore, the effect of curing conditions was investigated on the compressive strength behavior of structural elements. For this reason, the performance properties of white concrete with various cement contents in the range of 250-650 kg/m3 were examined experimentally by keeping chemical admixture ratio constantly. The mixtures were produced in ten different proportions with and without chemical admixtures. The concrete mixtures which were prepared and cured in three different curing conditions. Some of the specimens were placed in water at 20 ± 2 oC and some of them were kept in laboratory environment without placing in water (20 ± 2 oC and % 68 RH and the rest of the specimens were kept in nylon cover. In hardened concrete testing, compressive strength test was performed at 7, 28 and 90 days for white concrete specimens. Based on these concrete designs, it can be concluded that by the use of white cement between 250 and 650 kg/m3 it is possible to produce white concrete according to the ready-mixed concrete standard. According to test results, the specimens which were kept in water and prepared with chemical admixtures were performed better performance than the specimens were kept in air and nylon cover and produced without chemical admixtures.

  19. Experiments on the enhancement of compressible mixing via streamwise vorticity. II - Vortex strength assessment and seed particle dynamics

    Science.gov (United States)

    Naughton, J. W.; Cattafesta, L. N.; Settles, G. S.

    1993-01-01

    The effect of streamwise vorticity on compressible axisymmetric mixing layers is examined using vortex strength assessment and seed particle dynamics analysis. Experimental results indicate that the particles faithfully represent the dynamics of the turbulent swirling flow. A comparison of the previously determined mixing layer growth rates with the present vortex strength data reveals that the increase of turbulent mixing up to 60 percent scales with the degree of swirl. The mixing enhancement appears to be independent of the compressibility level of the mixing layer.

  20. Characterization of compression strength of granite-epoxy composites using design of experiments

    Scientific Electronic Library Online (English)

    Antonio, Piratelli-Filho; Frank, Shimabukuro.

    2008-12-01

    Full Text Available This paper presents a processing study of the polymer matrix composite (PMC) developed with an epoxy polymeric matrix reinforced with particulate ceramic granite. This PMC composite has been reported to be used as structural parts of machine tools and Coordinate Measuring Machines due to its superio [...] r vibration damping characteristics and reduced processing cycle over cast iron. The investigated processing variables were epoxy content and particle size and the mechanical characterization was carried out by compressive tests. Rejects of granite with particle size smaller than 500 µm were prepared by crushing, milling and classification operations. The powder was mixed with different compositions of epoxy resin, between 15 and 20% in weight. An experiment was planned and executed according to the Factorial design technique using two variables at two levels. The obtained cylindrical samples were submitted to compressive strength tests and the results showed a maximum resistance of 114.23 MPa at 20 wt. (%) epoxy, value close to that of the literature.

  1. Enhanced densification, strength and molecular mechanisms in shock compressed porous silicon

    Science.gov (United States)

    Lane, J. Matthew D.; Vogler, Tracy J.

    2015-06-01

    In most porous materials, void collapse during shock compression couples mechanical energy to thermal energy. Increased temperature drives up pressures and lowers densities in the final Hugoniot states as compared to full-density samples. Some materials, however, exhibit an anomalous enhanced densification in their Hugoniot states when porosity is introduced. We have recently shown that silicon is such a material, and demonstrated a molecular mechanism for the effect using molecular simulation. We will review results from large-scale non-equilibrium molecular dynamics (NEMD) and Hugoniotstat simulations of shock compressed porous silicon, highlighting the mechanism by which porosity produces local shear which nucleate partial phase transition and localized melting at shock pressures below typical thresholds in these materials. Further, we will characterize the stress states and strength of the material as a function of porosity from 5 to 50 percent and with various porosity microstructures. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  2. Effects of fabrication and joining processes on compressive strength of boron/aluminum and borsic/aluminum structural panels

    International Nuclear Information System (INIS)

    Processes for forming and joining boron/aluminum and borsic/aluminum to themselves and to titanium alloys were studied. Composite skin and titanium skin panels were joined to composite stringers by high strength bolts, by spotwelding, by diffusion bonding, by adhesive bonding, or by brazing. The effects of the fabrication and joining processes on panel compressive strengths were discussed. Predicted buckling loads were compared with experimental data

  3. Effects of fabrication and joining processes on compressive strength of boron/aluminum and borsic/aluminum structural panels

    Science.gov (United States)

    Royster, D. M.; Wiant, H. R.; Mcwithey, R. R.

    1978-01-01

    Processes for forming and joining boron/aluminum and borsic/aluminum to themselves and to titanium alloys were studied. Composite skin and titanium skin panels were joined to composite stringers by high strength bolts, by spotwelding, by diffusion bonding, by adhesive bonding, or by brazing. The effects of the fabrication and joining processes on panel compressive strengths were discussed. Predicted buckling loads were compared with experimental data.

  4. Developing a Material Strength Design Value Based on Compression after Impact Damage for the Ares I Composite Interstage

    Science.gov (United States)

    Nettles, A. T.; Jackson, J. R.

    2009-01-01

    The derivation of design values for compression after impact strength for two types of honeycomb sandwich structures are presented. The sandwich structures in this study had an aluminum core and composite laminate facesheets of either 16-ply quasi or 18-ply directional lay-ups. The results show that a simple power law curve fit to the data can be used to create A- and B-basis residual strength curves.

  5. Predicting the compressive and tensile strength of rocks from indentation hardness index

    Scientific Electronic Library Online (English)

    S, Kahraman; M, Fener; E, Kozman.

    2012-05-01

    Full Text Available The prediction of rock properties from indirect testing methods is important, particularly for preliminary investigations since indirect tests are easier and cheaper than the direct tests. In this study, we investigate the predictability of the uniaxial compressive strength (UCS) and Brazilian tensi [...] le strength (BTS) of rocks from the indentation hardness index (IHI) obtained using point load apparatus. Forty-six different rock types, 14 of which were igneous, 15 were metamorphic, and 17 were sedimentary were tested in the laboratory. The UCS and BTS values were correlated with the corresponding IHIvalues and the results were statistically analysed. The influence of rock classes on the relationships was also investigated. A strong correlation between UCS and IHI was found for all data. The correlation between BTS and IHI is not as strong as the correlation between UCS and IHI. However, it is in the acceptable limits. When the regression analyses were repeated for igneous, metamorphic, and sedimentary rocks, the correlation coefficients were generally increased. The results show the UCS and BTS can be estimated from IHI. In addition, the effect of rock classes on the relationships between IHI and both UCS and BTS is important.

  6. Determining the Compressive, Flexural and Splitting Tensile Strength of Silica Fume Reinforced Lightweight Foamed Concrete

    Directory of Open Access Journals (Sweden)

    Mydin M.A.O.

    2014-01-01

    Full Text Available This study investigated the performance of the properties of foamed concrete in replacing volumes of cement of 10%, 15% and 20% by weight. A control unit of foamed concrete mixture made with ordinary Portland cement (OPC and 10%, 15% and 20% silica fume was prepared. Three mechanical property parameters were studied such as compressive strength, flexural strength and splitting tensile of foamed concrete with different percentages of silica fume. Silica fume is commonly used to increase the mechanical properties of concrete materials and it is also chosen due to certain economic reasons. The foamed concrete used in this study was cured at a relative humidity of 70% and a temperature of ±28°C. The improvement of mechanical properties was due to a significant densification in the microstructure of the cement paste matrix in the presence of silica fume hybrid supplementary binder as observed from micrographs obtained in the study. The overall results showed that there is a potential to utilize silica fume in foamed concrete, as there was a noticeable enhancement of thermal and mechanical properties with the addition of silica fume.

  7. Strength improvement in transformation toughened ceramics using compressive residual surface stresses

    International Nuclear Information System (INIS)

    Al/sub 2/O/sub 3/-15 vol. % ZrO/sub 2/ bar shaped composite specimens were fabricated by pressing three layers. The two outer layers consisted of Al/sub 2/O/sub 3/ and unstabilized ZrO/sub 2/ (primarily in the monoclinic polymorph), and the inner layer consisted of Al/sub 2/O/sub 3/ and partially stabilized zirconia in the tetragonal polymorph. The transformation of ZrO/sub 2/ from tetragonal to monoclinic, upon cooling from sintering temperature, led to the establishment of residual compressive stresses in the outer layers. Flexural tests at room temperature showed that residual stresses contributed to strength increasing from 450 to 825 MPa. The existence of these stresses was verified by measuring apparent fracture toughness, as well as using strain gages. Strength and toughness data were obtained at 500, 750, and 1000/sup 0/C. X-ray diffraction was used to explain the elevated temperature data by monitoring the monoclinic to tetragonal transformation upon heating to 1000/sup 0/C

  8. Compressive Strength and Water Permeability Performance of Micronised Biomass Silica Concrete

    Directory of Open Access Journals (Sweden)

    S.H. Adnan

    2009-12-01

    Full Text Available Concrete is a common material that is widely used in construction industry. Cement is the main material component for producing concrete but its production has lead into CO2 emission. This work presents a study on Micronised Biomass Silica (MBS that can be used as pozzolan material which can enhance the quality of concrete. The material can be produced from a by-product of biomass agricultural waste but for this study rice husk has been used. From the chemical analysis, MBS has a chemical composition that is fulfill the standard requirement for becoming pozzolan material. The result of MBS concrete shows that the MBS material can enhance the performance of concrete by increasing the compressive strength development and reducing the water permeability. The drawback of MBS is the workability of fresh concrete but can be rectify by using superplasticizer. By replacing up to 12% of cement, MBS material gives the highest performance in term of strength and permeability of the concrete.

  9. Compressive and splitting tensile strength of autoclaved aerated concrete (AAC containing perlite aggregate and polypropylene fiber subjected to high temperatures

    Directory of Open Access Journals (Sweden)

    Borvorn Israngkura Na Ayudhya

    2011-10-01

    Full Text Available This paper presents the results of an experimental study on the residual compressive and splitting tensile strength ofautoclaved aerated concrete (AAC containing perlite and polypropylene (PP fiber subjected to high temperatures. Cylinderspecimens were subjected to various temperature ranges of 100, 200, 400, 800, and 1,000°C. The mixtures were prepared withAAC cementitious materials containing perlite at 15%, 20%, and 30% sand replacement. The polypropylene fiber content of0, 0.5%, 1%, 1.5%, and 2% by volume was also added to the mixture. The results showed that the unheated compressive andsplitting tensile strength of AACs containing PP fiber were not significantly higher than those containing no PP fiber.Furthermore, the presence of PP fiber was not more effective for residual compressive strength than splitting tensile strength.The 30% perlite replacement of sand gave the highest strength. Based on the results, it can be concluded that addition ofPP fiber did not significantly promote the residual strength of AAC specimens subjected to high temperatures.

  10. Compressive strength of glass fiber reinforced composites at room temperature, 77 K and 4.2 K

    International Nuclear Information System (INIS)

    Experiments to determine the ultimate compressive strengths of industrial high-pressure laminates are reported. The choice of materials has been restricted to low cost unidirectional glass fiber and glass cloth reinforcement in matrices of polyester, vinyl ester, and epoxy. Measurements on 1.27 cm diameter rods at room temperature, 77 k and 4.2 k have been made

  11. EFFECT OF SODIUM HYDROXIDE CONCENTRATION ON FRESH PROPERTIES AND COMPRESSIVE STRENGTH OF SELF-COMPACTING GEOPOLYMER CONCRETE

    Directory of Open Access Journals (Sweden)

    FAREED AHMED MEMON

    2013-02-01

    Full Text Available This paper reports the results of the laboratory tests conducted to investigate the effect of sodium hydroxide concentration on the fresh properties and compressive strength of self-compacting geopolymer concrete (SCGC. The experiments were conducted by varying the concentration of sodium hydroxide from 8 M to 14 M. Test methods such as Slump flow, V-Funnel, L-box and J-Ring were used to assess the workability characteristics of SCGC. The test specimens were cured at 70°C for a period of 48 hours and then kept in room temperature until the day of testing. Compressive strength test was carried out at the ages of 1, 3, 7 and 28 days. Test results indicate that concentration variation of sodium hydroxide had least effect on the fresh properties of SCGC. With the increase in sodium hydroxide concentration, the workability of fresh concrete was slightly reduced; however, the corresponding compressive strength was increased. Concrete samples with sodium hydroxide concentration of 12 M produced maximum compressive strength.

  12. Improving the standard of the standard for glass ionomers: an alternative to the compressive fracture strength test for consideration?

    LENUS (Irish Health Repository)

    Dowling, Adam H

    2012-03-01

    Three strength tests (compressive, three point flexure and biaxial) were performed on three glass ionomer (GI) restoratives to assess the most appropriate methodology in terms of validity and reliability. The influence of mixing induced variability on the data sets generated were eliminated by using encapsulated GIs.

  13. Experiment to Measure the Strength of Lead to ~ 1.5 Mbar by Compression and Release using the Z Machine

    Science.gov (United States)

    Rothman, Stephen; Brown, Justin; Davis, Jean-Paul

    2015-06-01

    We are planning an experiment to infer the strength of lead at ~ 1.5 Mbar by ramp compression and release using the Z machine. Longitudinal and bulk sound speeds may be calculated from the measurement of the velocity of the interface between thin lead samples and a LiF window by an iterative process using either a transfer-function or characteristics-based method to map in-situ velocity onto measured window velocity. The hydrostatic response comes from analysis of the compression; the strength at each iteration step from the difference between the longitudinal and (extrapolated) bulk sound speeds. As lead is expected to be soft, the effect of its strength on the expansion on release is thought to be small, and may be treated as an error on the results, contrary to similar results for, e.g., Ta. (c) British Crown Owned Copyright 2015/AWE.

  14. An effective thickness proposal for strength evaluation of one-side pitted steel plates under uniaxial compression

    Scientific Electronic Library Online (English)

    Zorareh Hadj Mohammad Esmaeil, Nouri; Mohammad Reza, Khedmati; Shokoufeh, Sadeghifard.

    2012-08-01

    Full Text Available This paper presents the results of an investigation into the post-buckling behaviour and ultimate strength of imperfect pitted steel plates used in ship and other marine-related structures. A series of elastic-plastic large deflection finite element analyses is performed on pitted steel plates. The [...] effects of pitting corrosion on one side of the plates are introduced into the finite element models. The effects on plate compressive strength as a result of parametric variation of the pitting corrosion geometry are evaluated. A proposal on the effective thickness is concluded in order to estimate the ultimate strength and explore the post-buckling behaviour of pitted steel plates under uniaxial compression.

  15. Data on Material Properties and Panel Compressive Strength of a Plastic-bonded Material of Glass Cloth and Canvas

    Science.gov (United States)

    Zender, George W; Schuette, Evan H; Weinberger, Robert A

    1944-01-01

    Results are presented of tests for determining the tensile, compressive, and bending properties of a material of plastic-bonding glass cloth and canvas layers. In addition, 10 panel specimens were tested in compression. Although the material is not satisfactory for primary structural use in aircraft when compared on a strength-weight basis with other materials in common use, there appears to be potential strength in the material that will require research for development. These points are considered in some detail in the concluding discussion of the report. An appendix shows that a higher tensile strength can be obtained by changes in the type of weave used in the glass-cloth reinforcement.

  16. Comparative experimental study of dynamic compressive strength of mortar with glass and basalt fibres

    Directory of Open Access Journals (Sweden)

    Kruszka Leopold

    2015-01-01

    Full Text Available Specimen reinforced with glass and basalt fibers were prepared using Standard Portland cement (CEM I, 52.5 R as prescribed by EN 197-1 and standard sand, in accordance with EN 196-1. From this cementitious mixture, a reference cement mortar without fibers was first prepared. Compressive strength, modulus of elasticity, and mod of fracture were determined for all specimens. Static and dynamic properties were investigated using Instron testing machine and split Hopkinson pressure bar, respectively. Content of the glass fibers in the mortar does not influence the fracture stress at static loading conditions in a clearly observed way. Moreover at dynamic range 5% content of the fiber results in a significant drop of fracture stress. Analysis of the basalt fibers influence on the fracture stress shows that optimal content of this reinforcement is equal to 3% for both static and dynamic loading conditions. Further increase of the fiber share gives the opposite effect, i.e. drop of the fracture stress.

  17. Comparative experimental study of dynamic compressive strength of mortar with glass and basalt fibres

    Science.gov (United States)

    Kruszka, Leopold; Mo?ko, Wojciech; Fenu, Luigi; Cadoni, Ezio

    2015-09-01

    Specimen reinforced with glass and basalt fibers were prepared using Standard Portland cement (CEM I, 52.5 R as prescribed by EN 197-1) and standard sand, in accordance with EN 196-1. From this cementitious mixture, a reference cement mortar without fibers was first prepared. Compressive strength, modulus of elasticity, and mod of fracture were determined for all specimens. Static and dynamic properties were investigated using Instron testing machine and split Hopkinson pressure bar, respectively. Content of the glass fibers in the mortar does not influence the fracture stress at static loading conditions in a clearly observed way. Moreover at dynamic range 5% content of the fiber results in a significant drop of fracture stress. Analysis of the basalt fibers influence on the fracture stress shows that optimal content of this reinforcement is equal to 3% for both static and dynamic loading conditions. Further increase of the fiber share gives the opposite effect, i.e. drop of the fracture stress.

  18. A comparative in vitro study of microleakage by a radioactive isotope and compressive strength of three nanofilled composite resin restorations

    Directory of Open Access Journals (Sweden)

    Rupika Gogna

    2011-01-01

    Full Text Available Aim : This study compares the compressive strength and microleakage of three nanofilled composites using radioactive isotope ?Ca 45. Materials and Methods : Thirty-six freshly extracted human premolars were used in this study. Standardized Class I preparation was carried out and then randomly divided into three different groups: A, B, and C with 12 teeth in each group which were restored with nanofilled composite restoration and then subjected to thermocycling. Microleakage was tested using radioactive isotope Ca 45 . Kruskal-Wallis and Mann-Whitney tests were used to compare the microleakage scores of the three groups. For measuring the compressive strength of three nanofilled composite resin restorations, 12 specimens of each material were prepared in customized stainless steel cylindrical moulds of 6 mm ?4 mm. The compressive test was performed using the Universal Testing Machine. The values were analyzed with ANOVA and Bonferroni?s test. Results : The findings of this study indicate that the synergy has the least microleakage and highest compressive strength followed by the Grandio and Filtek Z-350. Conclusions : Introduction of nanocomposites (packable appears to have improved the performance of both anterior and posterior restorations with regard to mechanical properties, marginal integrity, and esthetics.

  19. Effect of carbonation on leachability, strength and microstructural characteristics of KMP binder stabilized Zn and Pb contaminated soils.

    Science.gov (United States)

    Du, Yan-Jun; Wei, Ming-Li; Reddy, Krishna R; Wu, Hao-Liang

    2016-02-01

    This study presents a systematic investigation of effects of carbonation on the contaminant leachability and unconfined compressive strength of KMP stabilized contaminated soils. A field soil spiked with Zn and Pb individually and together is stabilized using a new KMP additive under standard curing conditions and also with carbonation. The KMP additive is composed of oxalic acid-activated phosphate rock, monopotassium phosphate and reactive magnesia. The stabilized soils are tested for acid neutralization capacity, toxic characteristics leaching characteristics, contaminant speciation and unconfined compression strength. X-ray diffraction, scanning electron microscope and energy dispersive spectroscopy analyses are performed to assess reaction products. The results demonstrate that carbonation increases both acid buffer capacity index and unconfined compressive strength, but decreases leachability of KMP stabilized soils. These results are interpreted based on the changes in chemical speciation of Zn and Pb and also stability and solubility of the reaction products (metal phosphates and carbonates) formed in the soils. Overall, this study demonstrates that carbonation has positive effects on leachability and strength of the KMP stabilized soils. PMID:26451653

  20. Effect of Superplasticizer and Extra Water on Workability and Compressive Strength of Self-Compacting Geopolymer Concrete

    Directory of Open Access Journals (Sweden)

    Fareed Ahmed Memon

    2012-03-01

    Full Text Available This study documents the results of an experimental work carried out to investigate the effect of superplasticizer and amount of extra water on strength and workability properties of Fly ash-based Selfcompacting geopolymer concrete. The experiments were conducted by varying the amount of extra water and dosage of superplasticizer. A total of nine mixtures with superplasticizer content varying from 3 to 7% and extra water ranging from 10 to 20% of the mass of fly ash were prepared and tested. The essential workability properties of the freshly prepared concrete such as filling ability, passing ability and segregation resistance were evaluated by using Slump flow, T50 slump flow, V-funnel, L-box and J-ring test methods. The compressive strength tests were carried out at 1, 3, 7 and 28 days. Test results indicated that extra water and superplasticizer are key parameters and play an important role in the development of self-compacting geopolymer concrete. Workability of self-compacting geopolymer concrete was dependent on the amount of extra water and dosage of superplasticizer. With the increase in amount of extra water and superplasticizer, the workability was improved. However, the addition of water beyond 15% resulted in bleeding as well as segregation and decreased the compressive strength of the concrete. The compressive strength of self-compacting geopolymer concrete was significantly decreased as the amount of extra water exceeded 12% by mass of Fly ash.

  1. An Experimental Investigation On Minimum Compressive Strength Of Early Age Concrete To Prevent Frost Damage For Nuclear Power Plant Structures In Cold Climates

    International Nuclear Information System (INIS)

    Concrete undergoing early frost damage in cold weather will experience significant loss of not only strength, but also of permeability and durability. Accordingly, concrete codes like ACI-306R prescribe a minimum compressive strength and duration of curing to prevent frost damage at an early age and secure the quality of concrete. Such minimum compressive strength and duration of curing are mostly defined based on the strength development of concrete. However, concrete subjected to frost damage at early age may not show a consistent relationship between its strength and durability. Especially, since durability of concrete is of utmost importance in nuclear power plant structures, this relationship should be imperatively clarified. Therefore, this study verifies the feasibility of the minimum compressive strength specified in the codes like ACI-306R by evaluating the strength development and the durability preventing the frost damage of early age concrete for nuclear power plant. The results indicate that the value of 5 MPa specified by the concrete standards like ACI-306R as the minimum compressive strength to prevent the early frost damage is reasonable in terms of the strength development, but seems to be inappropriate in the viewpoint of the resistance to chloride ion penetration and freeze-thaw. Consequently, it is recommended to propose a minimum compressive strength preventing early frost damage in terms of not only the strength development, but also in terms of the durability to secure the quality of concrete for nuclear power plants in cold climates

  2. Study of the strength of molybdenum under high pressure using electromagnetically applied compression-shear ramp loading

    Science.gov (United States)

    Ding, Jow; Alexander, C. Scott; Asay, James

    2015-06-01

    MAPS (Magnetically Applied Pressure Shear) is a new technique that has the potential to study material strength under mega-bar pressures. By applying a mixed-mode pressure-shear loading and measuring the resultant material responses, the technique provides explicit and direct information on material strength under high pressure. In order to apply sufficient shear traction to the test sample, the driver must have substantial strength. Molybdenum was selected for this reason along with its good electrical conductivity. In this work, the mechanical behavior of molybdenum under MAPS loading was studied. To understand the experimental data, a viscoplasticity model with tension-compression asymmetry was also developed. Through a combination of experimental characterization, model development, and numerical simulation, many unique insights were gained on the inelastic behavior of molybdenum such as the effects of strength on the interplay between longitudinal and shear stresses, potential interaction between the magnetic field and molybdenum strength, and the possible tension-compression asymmetry of the inelastic material response. Sandia National Labs is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. Dept. of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  3. Experimental study on compressive strength of concrete by partially replacement of cement with sugar cane bagasse ash

    Directory of Open Access Journals (Sweden)

    Jayminkumar A. Patel

    2015-04-01

    Full Text Available Use of waste material in concrete is important for environmental aspect. Sugar cane bagasse ash is a waste by product of sugar mill. Present study is to investigate impact of sugar cane bagasse ash in concrete. In this experimental work sugar cane bagasse ash which is taken from Maroli sugar mill, Navsari, Gujarat, INDIA is partially replace with cement at 0%, 5%, 10%, 15% and 20% by weight in concrete. The grade of concrete is M25 and w/c ratio is 0.49 taken as a reference. 150*150*150 mm cubes are casted and tested for 7, 14, 28 and 56 days. Compressive strength result shows that up to 10% replacement of sugar cane bagasse ash in concrete gives comparable result with normal concrete without any admixture, but 5% replacement give maximum compressive strength. Also the amount of sugar cane bagasse ash increase, workability of concrete increases.

  4. Finite Element Analysis for Coating Strength of a Piston Compression Ring in Contact with Cylinder Liner: A Tribodynamic Analysis

    Directory of Open Access Journals (Sweden)

    P.C. Mishra

    2015-03-01

    Full Text Available Piston Compression ring is the constituent part of ring-liner sliding pair that is subjected to high load and speed condition. Due to lubrication regime transition, there is the greater chance of wear and tear in the ring as well as in the liner. In order to reduce the wear and to enhance the ring and liner life, ceramic coatings are provided on the surface of such contact pairs. Current paper uses a finite element method to analyze the coating strength of a compression ring at compression and power stroke transition, where peak combustion pressure is higher than other crank positions. The deformation, von Misses stress and strain in the core and coating interface are discussed elaborately.

  5. Embedded NMR Sensor to Monitor Compressive Strength Development and Pore Size Distribution in Hydrating Concrete

    Directory of Open Access Journals (Sweden)

    Floriberto Díaz-Díaz

    2013-11-01

    Full Text Available In cement-based materials porosity plays an important role in determining their mechanical and transport properties. This paper describes an improved low–cost embeddable miniature NMR sensor capable of non-destructively measuring evaporable water loss and porosity refinement in low and high water-to-cement ratio cement-based materials. The sensor consists of two NdFeB magnets having their North and South poles facing each other, separated by 7 mm to allow space for a Faraday cage containing a Teflon tube and an ellipsoidal RF coil. To account for magnetic field changes due to temperature variations, and/or the presence of steel rebars, or frequency variation due to sample impedance, an external tuning circuit was employed. The sensor performance was evaluated by analyzing the transverse magnetization decay obtained with a CPMG measurement from different materials, such as a polymer phantom, fresh white and grey cement pastes with different w/c ratios and concrete with low (0.30 and high (0.6 w/c ratios. The results indicated that the sensor is capable of detecting changes in water content in fresh cement pastes and porosity refinement caused by cement hydration in hardened materials, even if they are prepared with a low w/c ratio (w/c = 0.30. The short lifetime component of the transverse relaxation rate is directly proportional to the compressive strength of concrete determined by destructive testing. The r2 (0.97 from the linear relationship observed is similar to that obtained using T2 data from a commercial Oxford Instruments 12.9 MHz spectrometer.

  6. Effects of carbonation on the leachability and compressive strength of cement-solidified and geopolymer-solidified synthetic metal wastes.

    Science.gov (United States)

    Pandey, Bhishan; Kinrade, Stephen D; Catalan, Lionel J J

    2012-06-30

    The effects of accelerated carbonation on the compressive strength and leachability of fly ash-based geopolymer and ordinary portland cement (OPC) doped with Cd(II), Cr(III), Cr(VI), Cu(II), Pb(II) or Zn(II) salts were investigated. Cement was effective at immobilizing Cd, Cr(III), Cu, Pb and Zn under both the Synthetic Precipitation Leaching Procedure (SPLP) and the Toxicity Characteristic Leaching Procedure (TCLP), but ineffective for retaining Cr(VI). Carbonated cement maintained its ability to immobilize Cd, Cr(III), Pb and Zn, but, under acidic TCLP conditions, was much worse at retaining Cu. Geopolymer was effective at immobilizing Cr(III) and Cu, and, to a lesser degree, Cd, Pb and Zn in SPLP leaching tests. Only Cr(III) was immobilized under comparatively acidic TCLP testing conditions. Carbonation did not change the metal retention capacity of the geopolymer matrix. Metal doping caused compressive strengths of both geopolymer and cement to decrease. Carbonation increased the compressive strength of cement, but decreased that of the geopolymer. Geochemical equilibrium modeling provided insight on the mechanisms of metal immobilization. PMID:22406845

  7. Experimental and statistical study of the influence of broken up particles and air content on the compressive strength of concretes

    International Nuclear Information System (INIS)

    Companies in Algeria have restricted budgets devoted to the formulation of concrete. Therefore, very few research studies are interested by the concrete composition in accordance to its purpose. Hence, this work is a part of an approved research program assigned to clarify the impact of certain parameters on the quality of concrete. This experimental program consists of more than 700 cylindrical specimens of 16x32 cm that were made using local materials. Excluding the durability indicators towards the concrete, the compressive strength is the most significant property to be considered (Mounanga et al., 2006). The obtained results concern consistency and content air propertiesof the concrete at fresh state and compressive strength of hardened concrete at 28 days. Thus, the influence of the air content percentage on the concrete consistency is studied. Moreover, the influence of these two parameters on the compressive strength of the hardened concrete is also presented. The experimental results obtained constitute a data bank, which allows comparing through a statistical analysis, the model established by Feret (Baron and Ollivier, 1996) and the results of the tests. (author)

  8. Investigation of Noise Level and Penetration Rate of Pneumatic Drill vis-à-vis Rock Compressive Strength and Abrasivity

    Science.gov (United States)

    Kivade, S. B.; Murthy, Ch. S. N.; Vardhan, H.

    2014-10-01

    In this paper, detailed studies were carried out to determine the influence of rock properties on the sound level produced during pneumatic drilling. Further, investigation was also carried out on the effect of thrust, air pressure and compressive strength on penetration rate and the sound level produced. For this purpose, a fabricated pneumatic drill set up available in the institute was used. Rock properties, like compressive strength and abrasivity, of various samples collected from the field were determined in the laboratory. Drilling experiments were carried out on ten different rock samples for varying thrust and air pressure values and the corresponding A-weighted equivalent continuous sound levels were measured. It was observed that, very low thrust results in low penetration rate. Even very high thrust does not produce high penetration rate at higher operating air pressures. With increase in thrust beyond the optimum level, the penetration rate starts decreasing and causes the drill bit to `stall'. Results of the study show that penetration rate and sound level increases with increase in the thrust level. After reaching the maximum, they start decreasing despite the increase of thrust. The main purpose of the study is to develop a general prediction model and to investigate the relationships between sound level produced during drilling and physical properties such as uniaxial compressive strength and abrasivity of sedimentary rocks. The results were evaluated using the multiple regression analysis taking into account the interaction effects of predictor variables.

  9. An in vitro study to compare the transverse strength of thermopressed and conventional compression-molded polymethylmethacrylate polymers

    Directory of Open Access Journals (Sweden)

    Anjana Raut

    2013-01-01

    Full Text Available Statement of Problem: Acrylic resins have been in the center stage of Prosthodontics for more than half a century. The flexural fatigue failure of denture base materials is the primary mode of clinical failure. Hence there is a need for superior physical and mechanical properties. Purpose: This in vitro study compared the transverse strength of specimens of thermopressed injection-molded and conventional compression-molded polymethylmethacrylate polymers and examined the morphology and microstructure of fractured acrylic specimens. Materials and Methods: The following denture base resins were examined: Brecrystal (Thermopressed injection-molded, modified polymethylmethacrylate and Pyrax (compression molded, control group. Specimens of each material were tested according to the American Society for Testing and Materials standard D790-03 for flexural strength testing of reinforced plastics and subsequently examined under SEM. The data was analyzed with Student unpaired t test. Results: Flexural strength of Brecrystal (82.08 ± 1.27 MPa was significantly higher than Pyrax (72.76 ± 0.97 MPa. The tested denture base materials fulfilled the requirements regarding flexural strength (>65 MPa. The scanning electron microscopy image of Brecrystal revealed a ductile fracture with crazing. The fracture pattern of control group specimens exhibited poorly defined crystallographic planes with a high degree of disorganization. Conclusion: Flexural strength of Brecrystal was significantly higher than the control group. Brecrystal showed a higher mean transverse strength value of 82.08 ± 1.27 MPa and a more homogenous pattern at microscopic level. Based on flexural strength properties and handling characteristics, Brecrystal may prove to be an useful alternative to conventional denture base resins.

  10. Static compressive strength prediction of open-hole structure based on non-linear shear behavior and micro-mechanics

    Science.gov (United States)

    Li, Wangnan; Cai, Hongneng; Li, Chao

    2014-11-01

    This paper deals with the characterization of the strength of the constituents of carbon fiber reinforced plastic laminate (CFRP), and a prediction of the static compressive strength of open-hole structure of polymer composites. The approach combined with non-linear analysis in macro-level and a linear elastic micromechanical failure analysis in microlevel (non-linear MMF) is proposed to improve the prediction accuracy. A face-centered cubic micromechanics model is constructed to analyze the stresses in fiber and matrix in microlevel. Non-interactive failure criteria are proposed to characterize the strength of fiber and matrix. The non-linear shear behavior of the laminate is studied experimentally, and a novel approach of cubic spline interpolation is used to capture significant non-linear shear behavior of laminate. The user-defined material subroutine UMAT for the non-linear share behavior is developed and combined in the mechanics analysis in the macro-level using the Abaqus Python codes. The failure mechanism and static strength of open-hole compressive (OHC) structure of polymer composites is studied based on non-linear MMF. The UTS50/E51 CFRP is used to demonstrate the application of theory of non-linear MMF.

  11. Compressive strength, plastic flow properties, and surface frictional effects of 1100, 3003 and 6061 aluminum alloys

    Energy Technology Data Exchange (ETDEWEB)

    Pinkerton, G.W.

    1993-12-31

    The purpose of this study is to find aluminum alloys that are effective for use as wire vacuum seals in the 800MeV particle accelerator located at the Louis Anderson Meson Physics Facility (LAMPF) in Los Alamos, NM. Three alloys, Al 1100, Al 3003, and Al 6061, are investigated under uniaxial compression to determine stresses for a given height reduction from 0 to 70 percent, and to find plastic flow and surface interaction effects. Right-circular cylindrical specimens are compressed on-end (cylindrically) and radially (for modeling as compressed wire). Aluminum 1100 and 3003 alloys are compared for length to diameter ratios of 1 and 2 for both compression types, and are then compared to results of radial compression of annealed small diameter Al 1100 wire currently used at LAMPE. The specimens are also compressed between three different platen surfaces, polished steel, etched steel, and aluminum 6061-T6, to determine effects of friction. The Al 3003 alloy exhibits 20 to 25% lower stresses at all height reductions than Al 1100 for both cylindrical and radial compression.

  12. Compressive strength, plastic flow properties, and surface frictional effects of 1100, 3003 and 6061 aluminum alloys

    International Nuclear Information System (INIS)

    The purpose of this study is to find aluminum alloys that are effective for use as wire vacuum seals in the 800MeV particle accelerator located at the Louis Anderson Meson Physics Facility (LAMPF) in Los Alamos, NM. Three alloys, Al 1100, Al 3003, and Al 6061, are investigated under uniaxial compression to determine stresses for a given height reduction from 0 to 70 percent, and to find plastic flow and surface interaction effects. Right-circular cylindrical specimens are compressed on-end (cylindrically) and radially (for modeling as compressed wire). Aluminum 1100 and 3003 alloys are compared for length to diameter ratios of 1 and 2 for both compression types, and are then compared to results of radial compression of annealed small diameter Al 1100 wire currently used at LAMPE. The specimens are also compressed between three different platen surfaces, polished steel, etched steel, and aluminum 6061-T6, to determine effects of friction. The Al 3003 alloy exhibits 20 to 25% lower stresses at all height reductions than Al 1100 for both cylindrical and radial compression

  13. The influence of poly(acrylic) acid number average molecular weight and concentration in solution on the compressive fracture strength and modulus of a glass-ionomer restorative.

    LENUS (Irish Health Repository)

    Dowling, Adam H

    2011-06-01

    The aim was to investigate the influence of number average molecular weight and concentration of the poly(acrylic) acid (PAA) liquid constituent of a GI restorative on the compressive fracture strength (?) and modulus (E).

  14. Prediction of Compressive Strength of Self compacting Concrete with Flyash and Rice Husk Ash using Adaptive Neuro-fuzzy Inference System

    Directory of Open Access Journals (Sweden)

    S. S, Pathak

    2012-10-01

    Full Text Available Self-compacting concrete is an innovative concrete that does not require vibration for placing and compaction. It is able to flow under its own weight, completely filling formwork and achieving full compaction even in congested reinforcement without segregation and bleeding. In the present study self compacting concrete mixes were developed using blend of fly ash and rice husk ash. Fresh properties of theses mixes were tested by using standards recommended by EFNARC (European Federation for Specialist Construction Chemicals and Concrete system. Compressive strength at 28 days was obtained for these mixes. This paper presents development of Adaptive Neuro-fuzzy Inference System (ANFIS model for predicting compressive strength of self compacting concrete using fly ash and rice husk ash. The input parameters used for model are cement, fly ash, rice husk ash and water content. Output parameter is compressive strength at 28 days. The results show that the implemented model is good at predicting compressive strength.

  15. Predicting model on ultimate compressive strength of Al2O3-ZrO2 ceramic foam filter based on BP neural network

    OpenAIRE

    Yu Jingyuan; Li Qiang; Tang Ji

    2011-01-01

    In present study, BP neural network model was proposed for the prediction of ultimate compressive strength of Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting. The inputs of the BP neural network model were the applied load on the epispastic polystyrene template (F), centrifugal acceleration (v) and sintering temperature (T), while the only output was the ultimate compressive strength (?). According to the registered BP model, the effects of F, v, T on ? were analyzed. The ...

  16. Case history rock mechanics examination of the Jefferson Island Salt Mine: III. Evaluation of laboratory specimen dimensions on the uniaxial strength and deformational characteristics of dome salt

    International Nuclear Information System (INIS)

    This report presents the results of a laboratory effort to determine the unconfined strength and elastic properties of dome salt from the Diamond Crystal Mine, Jefferson Island, LA. The effects of sample size and geometry on the compressive properties of this salt were investigated, and relationships for compressive strength and deformational modulus as a function of specimen diameter and length to diameter ratio were developed. The results of a finite-element analysis of the stress state in a specimen loaded between steel platens are also presented. 20 figures, 4 tables

  17. OVERVIEW OF RECENT STUDIES AT IPST ON CORRUGATED BOARD EDGE COMPRESSION STRENGTH: TESTING METHODS AND EFFECTS OF INTERFLUTE BUCKLING

    Directory of Open Access Journals (Sweden)

    Roman Popil

    2012-04-01

    Full Text Available Several recent series of investigations were conducted on corrugated board performance in the areas of: loaded container endurance in cyclic humidity, predictive models for edge compression strength (ECT, effects of lightweight facings, measurement of transverse shear rigidity, effects of adhesive level, and out-of-plane crushing on ECT. The course of this program prompted exploration and review of several aspects of ECT testing methods: specimen height, test duration, and fixture-clamping effects. In this review, ECT values are shown to be influenced by the combination of the selected testing technique with the specific structural and strength characteristics of the board being tested. The effect of specimen height on selected single wall C-, E-, F-, and N-flute boards is measured and rationalized using a simplified beam-theory approach. Apparent loss of ECT in a C-flute crushed board is explored to determine whether mitigation is possible by selection or modification of testing method. Investigations of platen speed effects on C-flute substantiate previous work. Lightweight facings on A- and C-flute corrugated boards are observed to display localized buckling, which affects the ECT value. An analytical model that combines the measured bending stiffness of the facings and the compression strengths of the fluting and facings provides an improved predictive accuracy and is applied to a series of laboratory and commercial corrugated boards.

  18. Improvement of linerboard compressive strength by hot-pressing and addition of recovered lignin from spent pulping liquor

    Directory of Open Access Journals (Sweden)

    Saidan Motasem N.

    2015-01-01

    Full Text Available This paper evaluates the effect of addition of precipitated lignin, from spent pulping black liquor, to a wet single-ply linerboard handsheet followed by hot-pressing at different temperatures, on the improvement of its compressive strength. Linerboard handsheets for testing the effect of lignin addition were prepared so that the lignin-modified sheets would have the same basis weights as the control handsheets. Both the commercial and the black liquor lignin were added as a powder to wet handsheets after couching from the handsheet mold. The experiments and testing of the physical and strength properties of dried handsheets were conducted according to TAPPI test methods. The results revealed that the addition of the recovered lignin (at pH of 2 to the wet handsheet followed by hot-pressing at 150°C increased the compressive strength of linerboard handsheets by 10% to 20% above that for handsheets made without the addition of lignin. The same results were achieved using purchased lignin. However, with a 16% addition to linerboard, purchased lignin would be too expensive. These results indicate that inclusion of kraft lignin in linerboard sheets could be proved as an attractive option to reduce linerboard basis weight.

  19. Multicriteria decision-making analysis based methodology for predicting carbonate rocks' uniaxial compressive strength

    Scientific Electronic Library Online (English)

    Ersoy, Hakan; Derya, Kanik.

    2012-06-01

    Full Text Available La resistencia a la compresión uniaxial (RCU) trata con la capacidad de los materiales para soportar fuerzas empujantes dirigidas axialmente y, especialmente, es considerada ser uno de las más importantes propiedades mecánicas de los materiales rocosos. Sin embargo, una prueba de RCU es costosa, lle [...] va mucho tiempo para hacerlo en el laboratorio y requiere muestras de núcleos de alta calidad que tienen una geometría regular. Por lo tanto, ecuaciones empíricas fueron propuestas para la predicción de RCU como una función de las propiedades índice de las rocas. Las metodologías de proceso analítico jerárquico (PAJ) y análisis de regresión múltiple fueron utilizados (en vez de los métodos tradicionales de regresión lineal) en conjuntos de datos obtenidos de las rocas carbonatadas en el noreste de Turquía Muestras de rocas calizas que van desde el Devónico hasta finales del Cretácico fueron escogidas; muestras de travertino y ónix fueron seleccionadas de ambientes morfológicos teniendo en cuenta sus condiciones ambientales de superficie. Los resultados de los experimentos llevados a cabo en alrededor de 250 muestras de rocas carbonatadas fueron utilizados para derivar un modelo Mientras que el modelo de jerarquía se centró en determinar las propiedades índice más importantes afectados por la RCU, el análisis de regresión establece relaciones significativas entre la RCU y las propiedades del índice; coeficientes de correlación positivas de 0,85 y 0,83 fueron determinadas por análisis de regresión entre las variables La metodología proporciona una alternativa adecuada para la estimación cuantitativa de la RCU y evita la necesidad de realizar pruebas del laboratorio las cuales son tediosas y dispendiosas Abstract in english Uniaxial compressive strength (UCS) deals with materials' to ability to withstand axially-directed pushing forces and especially considered to be rock materials' most important mechanical properties. However, the UCS test is an expensive, very time-consuming test to perform in the laboratory and req [...] uires high-quality core samples having regular geometry. Empirical equations were thus proposed for predicting UCS as a function of rocks' index properties. Analytical hierarchy process and multiple regression analysis based methodology were used (as opposed to traditional linear regression methods) on data-sets obtained from carbonate rocks in NE Turkey. Limestone samples ranging from Devonian to late Cretaceous ages were chosen; travertine-onyx samples were selected from morphological environments considering their surface environmental conditions Test results from experiments carried out on about 250 carbonate rock samples were used in deriving the model. While the hierarchy model focused on determining the most important index properties affecting on UCS, regression analysis established meaningful relationships between UCS and index properties; 0. 85 and 0. 83 positive coefficient correlations between the variables were determined by regression analysis. The methodology provided an appropriate alternative to quantitative estimation of UCS and avoided the need for tedious and time consuming laboratory testing

  20. Multicriteria decision-making analysis based methodology for predicting carbonate rocks' uniaxial compressive strength

    Directory of Open Access Journals (Sweden)

    Ersoy Hakan

    2012-10-01

    Full Text Available

    ABSTRACT

    Uniaxial compressive strength (UCS deals with materials' to ability to withstand axially-directed pushing forces and especially considered to be rock materials' most important mechanical properties. However, the UCS test is an expensive, very time-consuming test to perform in the laboratory and requires high-quality core samples having regular geometry. Empirical equations were thus proposed for predicting UCS as a function of rocks' index properties. Analytical hierarchy process and multiple regression analysis based methodology were used (as opposed to traditional linear regression methods on data-sets obtained from carbonate rocks in NE Turkey. Limestone samples ranging from Devonian to late Cretaceous ages were chosen; travertine-onyx samples were selected from morphological environments considering their surface environmental conditions Test results from experiments carried out on about 250 carbonate rock samples were used in deriving the model. While the hierarchy model focused on determining the most important index properties affecting on UCS, regression analysis established meaningful relationships between UCS and index properties; 0. 85 and 0. 83 positive coefficient correlations between the variables were determined by regression analysis. The methodology provided an appropriate alternative to quantitative estimation of UCS and avoided the need for tedious and time consuming laboratory testing


    RESUMEN

    La resistencia a la compresión uniaxial (RCU trata con la capacidad de los materiales para soportar fuerzas empujantes dirigidas axialmente y, especialmente, es considerada ser uno de las más importantes propiedades mecánicas de los materiales rocosos. Sin embargo, una prueba de RCU es costosa, lleva mucho tiempo para hacerlo en el laboratorio y requiere muestras de núcleos de alta calidad que tienen una geometría regular.

    Por lo tanto, ecuaciones empíricas fueron propuestas para la predicción de RCU como una función de las propiedades índice de las rocas. Las metodologías de proceso analítico jerárquico (PAJ y análisis de regresión múltiple fueron utilizados (en vez de los métodos tradicionales de regresión lineal en conjuntos de datos obtenidos de las rocas carbonatadas en el noreste de Turquía Muestras de rocas calizas que van desde el Devónico hasta finales del Cretácico fueron escogidas; muestras de travertino y ónix fueron seleccionadas de ambientes morfológicos teniendo en cuenta sus condiciones ambientales de superficie.

    Los resultados de los experimentos llevados a cabo en alrededor de 250 muestras de rocas carbonatadas fueron utilizados para derivar un modelo Mientras que el modelo de jerarquía se centró en determinar las propiedades índice más importantes afectados por la RCU, el análisis de regresión establece relaciones significativas entre la RCU y las propiedades del índice; coeficientes de correlación positivas de 0,85 y 0,83 fueron determinadas por análisis de regresión entre las variables La metodología proporciona una alternativa adecuada para la estimación cuantitativa de la RCU y evita la necesidad de realizar pruebas del laboratorio las cuales son tediosas y dispendiosas

  1. EFFECT OF SODIUM HYDROXIDE CONCENTRATION ON FRESH PROPERTIES AND COMPRESSIVE STRENGTH OF SELF-COMPACTING GEOPOLYMER CONCRETE

    OpenAIRE

    FAREED AHMED MEMON; MUHD FADHIL NURUDDIN; SADAQATULLAH KHAN; NASIR SHAFIQ; TEHMINA AYUB

    2013-01-01

    This paper reports the results of the laboratory tests conducted to investigate the effect of sodium hydroxide concentration on the fresh properties and compressive strength of self-compacting geopolymer concrete (SCGC). The experiments were conducted by varying the concentration of sodium hydroxide from 8 M to 14 M. Test methods such as Slump flow, V-Funnel, L-box and J-Ring were used to assess the workability characteristics of SCGC. The test specimens were cured at 70°C for a period of 48 ...

  2. Resistencia a la compresión y reología de cementantes ambientalmente amigables / Compressive strength and rheology of environmentally-friendly binders

    Scientific Electronic Library Online (English)

    Juan Manuel, Lizarazo Marriaga; Peter, Claisse.

    2009-08-01

    Full Text Available Siendo la producción de cemento responsable de aproximadamente el 9% de la producción industrial de gases de invernadero, y en pro de generar materiales alternativos, en este artículo se presentan los resultados de una investigación encaminada a desarrollar cementantes que potencialmente representen [...] una alternativa ambientalmente sostenible en la construcción civil. Combinaciones de escoria granulada de alto horno, escoria de acería obtenida mediante un proceso de oxígeno básico, polvo de horno de cemento y residuo de demolición de divisiones de yeso fueron usados para optimizar la resistencia a la compresión y obtener cinco mezclas de concreto con cementantes hechos parcial o totalmente con residuos industriales. Los resultados obtenidos muestran que las resistencias de las mezclas compuestas de cemento Portland y residuos industriales son adecuadas para una cantidad importante de aplicaciones en construcción civil, y aunque para las mezclas formadas completamente por residuos industriales se presentó una importante disminución en la resistencia a la compresión, los resultados obtenidos mostraron un gran potencial para determinadas aplicaciones industriales. Adicionalmente a la resistencia a la compresión, a dichas mezclas se les determinaron sus propiedades reológicas definiendo sus características de flujo y trabajabilidad. Abstract in english Ordinary Portland cement production accounts for 9% of worldwide greenhouse gas emissions. This paper summarises the results of research aimed at developing environmentally-friendly binders which can be used as an alternative in civil construction, aimed at generating alternatives and sustainable ma [...] terials. Mixes of the combination of granulated ground blast furnace slag, basic oxygen slag, cement kiln dust and plasterboard gypsum were used for optimising the binders, according to their compressive strength, to obtain 5 concrete mixtures made partially or completely with industrial waste. The results showed that the compressive strength of mixtures of Portland cement and industrial waste were suitable for different civil construction applications and, although mixtures formed entirely from industrial waste had a significant decrease in their compressive strength, the results showed great potential for specific industrial applications. In addition to compressive strength, the rheological properties of these mixtures were determined for defining flow and workability characteristics.

  3. Effect of Wet and Dry Conditions on Strength of Silty Sand Soils Stabilized with Epoxy Resin Polymer

    Directory of Open Access Journals (Sweden)

    Masoud Ghorbanalizadeh

    2010-01-01

    Full Text Available This study reports on a laboratory experiment conducted to evaluate the stabilization of a silty-sand (SM material with epoxy resin and effect of wet and dry conditions on strength of stabilized silty sand. The additive mixture was composed of a 1:0.15 of epoxy resin to polyamide hardener. Specimens were prepared by adding different amount of epoxy resin polymer emulsion (3, 4 and 5% to silty sand with (0, 10, 20, 30, 35, 45 and 60% silt content at dry density of 17 kN m-3. The unconfined compressive strength of specimens determined with uniaxial test and compared to each other under the same mixing, compaction and curing condition to derivation the effect of polymer emulsion on silty sand. All specimens submerged in water for 24, 96 and 168 h and then taken out from the water and their unconfined compressive strength were recorded. The results of this study indicated that the addition of epoxy resin improves significantly the compressive strength and modulus of elasticity of samples under dry condition. This improvement depends on the content of polymer and silt. However, polymer significantly enhanced the strength of the samples after 7 days of submerging in water but strength of wet samples is less than the dry samples.

  4. The effect of welding on the strength of aluminium stiffened plates subject to combined uniaxial compression and lateral pressure

    Science.gov (United States)

    Pedram, Masoud; Khedmati, Mohammad Reza

    2014-03-01

    Nowadays aluminum stiffened plates are one of the major constituents of the marine structures, espe¬cially high-speed vessels. On one hand, these structures are subject to various forms of loading in the harsh sea envi¬ronment, like hydrostatic lateral pressures and in-plane compression. On the other hand, fusion welding is often used to assemble those panels. The common marine aluminum alloys in the both 5,000 and 6,000 series, however, lose a re¬markable portion of their load carrying capacity due to welding. This paper presents the results of sophisticated finite-element investigations considering both geometrical and mechanical imperfections. The tested models were those pro¬posed by the ultimate strength committee of 15th ISSC. The presented data illuminates the effects of welding on the strength of aluminum plates under above-mentioned load conditions.

  5. Studies on Relationship Between Water/Binder Ratio And Compressive Strength Of High Volume Fly Ash Concrete

    Directory of Open Access Journals (Sweden)

    Dr Sravana 1 Sarika.P 3 Dr.Srinivasa Rao 1 Dr.Seshadri Sekhar T 2 , Apparao.G 2 ,

    2013-08-01

    Full Text Available Pozzolanic admixtures are generally being used along with the cement in concrete mixes so as to derive certain benefits like economy, durability, Chemical resistance in permeability etc. The use of high volumes of fly ash has become on of the current topics of research possibility promoted by the availability of a wide range of chemical and mineral admixtures. In the present experimental investigation fly ash has been used in large volumes as an additional ingredient in concrete mixes. The present experimental investigations was carried out to study the relationship between Water /Binder Ratio to Compressive strength of high volume fly ash concrete using fly ash as an additional material in the cement concrete. The studies have indicated that the high volumes fly ash used in concrete as an additional material would lead to enhanced properties in concrete and contribute towards development of high performance and high strength concrete which is the need of the hour.

  6. Experimental investigation and empirical modelling of FDM process for compressive strength improvement

    Directory of Open Access Journals (Sweden)

    Anoop K. Sood

    2012-01-01

    Full Text Available Fused deposition modelling (FDM is gaining distinct advantage in manufacturing industries because of its ability to manufacture parts with complex shapes without any tooling requirement and human interface. The properties of FDM built parts exhibit high dependence on process parameters and can be improved by setting parameters at suitable levels. Anisotropic and brittle nature of build part makes it important to study the effect of process parameters to the resistance to compressive loading for enhancing service life of functional parts. Hence, the present work focuses on extensive study to understand the effect of five important parameters such as layer thickness, part build orientation, raster angle, raster width and air gap on the compressive stress of test specimen. The study not only provides insight into complex dependency of compressive stress on process parameters but also develops a statistically validated predictive equation. The equation is used to find optimal parameter setting through quantum-behaved particle swarm optimization (QPSO. As FDM process is a highly complex one and process parameters influence the responses in a non linear manner, compressive stress is predicted using artificial neural network (ANN and is compared with predictive equation.

  7. Compressive Strength Prediction of Square Concrete Columns Retrofitted with External Steel Collars

    Directory of Open Access Journals (Sweden)

    Pudjisuryadi, P.

    2013-01-01

    Full Text Available Transverse confining stress in concrete members, commonly provided by transverse reinforcement, has been recognized to enhance strength and ductility. Nowadays, the confining method has been further developed to external confinement approach. This type of confinement can be used for retrofitting existing concrete columns. Many external confining techniques have been proven to be successful in retrofitting circular columns. However, for square or rectangular columns, providing effective confining stress by external retrofitting method is not a simple task due to high stress concentration at column’s corners. This paper proposes an analytical model to predict the peak strength of square concrete columns confined by external steel collars. Comparison with the experimental results showed that the model can predict the peak strength reasonably well. However, it should be noted that relatively larger amount of steel is needed to achieve comparable column strength enhancement when it is compared with those of conve tional internally-confined columns.

  8. Spatial variability of the compressive strength of the Toki granite at the Shobasama and Mizunami Construction Site, Japan

    International Nuclear Information System (INIS)

    This paper studies the spatial variability of the laboratory results of uniaxial compressive tests on the Toki granite at the Shobasama and Mizunami Construction Site, Japan. Some of the spatial variability observed in the laboratory results can be indirectly attributed to the high fracture frequency of the upper highly fractured rock domain where some of the samples were taken. For samples taken from the lower sparsely fractured rock domain, however, the uniaxial compressive strength of the granite seems to be very strongly correlated to level of in-situ rock stress (i.e. maximum shear stress) determined by measurement results obtained from the hydro-fracturing method. The correlation between the laboratory results and the level of in-situ stress is explained by the damage due to the release of the stresses the cores undergo during drilling. An attempt to correct the laboratory results for estimating the in-situ intact rock strength based on its correlation with the in-situ stresses was carried out. (author)

  9. Compressive strength and ductility of short concrete columns reinforced by bamboo

    Directory of Open Access Journals (Sweden)

    Satjapan Leelatanon

    2010-08-01

    Full Text Available The paper presents the structural and environmentally sustainable aspects of bamboo as a reinforcing material insteadof steel reinforcement in concrete columns. Seven small-scale short columns (125 mm x 125 mm x 600 mm with different typeof reinforcements were tested under concentric loading to investigate strength capacity and ductility. The results showedthat the strength capacity of short columns reinforced by bamboo without surface treatment could resist the axial load asstructurally required by ACI318-05, but ductility was rather low especially the column that was reinforced by 1.6 percent ofreinforcing bamboo which showed brittle behavior similar to that of plain concrete column. This was thought to be an effectof water absorption and a loss of bonding strength between concrete and bamboo. On the other hand, columns reinforcedby bamboo treated with water-repellent substance, Sikadur-31CFN, showed higher strength and ductility than columnsreinforced by untreated bamboo. The result also showed that 1.6 % of steel reinforcement, in relation to the column crosssection,could be replaced by 3.2% of treated reinforcing bamboo, for similar behavior, strength and ductility.

  10. The Effects of Friction on the Compressive Behaviour of High Strength Steels

    OpenAIRE

    Ashton, M.; Parry, D

    1997-01-01

    An investigation, covering a wide range of strain rate and temperature has been performed into the effects of interfacial friction on the compressive properties of an armour plate steel. In order to calculate the coefficient of friction, ring tests were carried out and the Avitzur analysis applied. In general coefficients of friction decreased with increasing temperature and strain rate. Other specimen observations indicated the same friction trends. It is essential that friction corrections ...

  11. The fracture strength of TRISO-coated particles determined by compression testing between soft aluminium anvils

    International Nuclear Information System (INIS)

    Compression testing of tri-isotropic (TRISO) carbon/silicon carbide-coated fuel particles between anvil materials with a wide range of hardnesses was investigated. During compression testing, the particle produces a hardness impression before it fractures. For subsequent measurements, the same position can therefore not be used. A special testing machine was designed to use the same set of anvils for testing more than one specimen. By each time positioning a particle at a slightly different position between the anvils, a large number of measurements could be made. The load required for fracture is almost independent of anvil hardness for very hard or very soft anvils. Finite element stress analysis showed that when the anvil hardness is very high, fracture occurs because of high local contact bending stresses at the point of contact. In the case of very soft anvils, a tensile stress develops along a latitudinal direction along the perimeter of the particle over a large volume in between the contact zones with the anvils. The particle then fractures by the development of cracks at right angles to the direction of the tensile stress. From the fracture load, the ability of the particle to withstand internal pressure can be assessed. The advantages of using compression testing of full particles between soft anvils without prior preparation to complement previous test methods are highlighted.

  12. Radius bone strength in bending, compression, and falling and its correlation with clinical densitometry at multiple sites.

    Science.gov (United States)

    Lochmüller, Eva-Maria; Lill, Christoph A; Kuhn, Volker; Schneider, Erich; Eckstein, Felix

    2002-09-01

    This study comprehensively analyzes the ability of site-specific and nonsite-specific clinical densitometric techniques for predicting mechanical strength of the distal radius in different loading configurations. DXA of the distal forearm, spine, femur, and total body and peripheral quantitative computed tomography (pQCT) measurements of the distal radius (4, 20, and 33%) were obtained in situ (with soft tissues) in 129 cadavers, aged 80.16 +/- 9.8 years. Spinal QCT and calcaneal quantitative ultrasound (QUS) were performed ex situ in degassed specimens. The left radius was tested in three-point bending and axial compression, and the right forearm was tested in a fall configuration, respectively. Correlation coefficients with radius DXA were r = 0.89, 0.84, and 0.70 for failure in three-point bending, axial compression, and the fall simulation, respectively. The correlation with pQCT (r = 0.75 for multiple regression models with the fall) was not significantly higher than for DXA. Nonsite-specific measurements and calcaneal QUS displayed significantly (p prediction of axial failure stress but not of failure load. We conclude that a combination of pQCT parameters involves only marginal improvement in predicting mechanical strength of the distal radius, nonsite-specific measurements are less accurate for this purpose, and QUS adds only little independent information to site-specific bone mass. Therefore, the noninvasive diagnosis of loss of strength at the distal radius should rely on site-specific measurements with DXA or pQCT and may be the earliest chance to detect individuals at risk of osteoporotic fracture. PMID:12211433

  13. Modeling and analysis of porosity and compressive strength of gradient Al2O3-ZrO2 ceramic filter using BP neural network

    Directory of Open Access Journals (Sweden)

    Li Qiang

    2013-07-01

    Full Text Available BP neural network was used in this study to model the porosity and the compressive strength of a gradient Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting. The influences of the load applied on the epispastic polystyrene template (F, the centrifugal acceleration (v and sintering temperature (T on the porosity (P and compressive strength (? of the sintered products were studied by using the registered three-layer BP model. The accuracy of the model was verified by comparing the BP model predicted results with the experimental ones. Results show that the model prediction agrees with the experimental data within a reasonable experimental error, indicating that the three-layer BP network based modeling is effective in predicting both the properties and processing parameters in designing the gradient Al2O3-ZrO2 ceramic foam filter. The prediction results show that the porosity percentage increases and compressive strength decreases with an increase in the applied load on epispastic polystyrene template. As for the influence of sintering temperature, the porosity percentage decreases monotonically with an increase in sintering temperature, yet the compressive strength first increases and then decreases slightly in a given temperature range. Furthermore, the porosity percentage changes little but the compressive strength first increases and then decreases when the centrifugal acceleration increases.

  14. Nitrate reduction in an unconfined sandy aquifer

    DEFF Research Database (Denmark)

    Postma, Diederik Jan; Boesen, Carsten; Kristiansen, Henning; Larsen, Flemming

    1991-01-01

    Nitrate distribution and reduction processes were investigated in an unconfined sandy aquifer of Quaternary age. Groundwater chemistry was studied in a series of eight multilevel samplers along a flow line, deriving water from both arable and forested land. Results show that plumes of nitrate-contaminated groundwater emanate from the agricultural areas and spread through the aquifer. The aquifer can be subdivided into an upper 10- to 15-m thick oxic zone that contains O2 and NO3-, and a lower an...

  15. A comparative study of the compressive, flexural and bond strength of brick masonry.

    OpenAIRE

    PAVIA, SARA

    2009-01-01

    Due to their physical and chemical properties, mortars made with lime are considered to be more compatible with historic fabrics than those made with artificial cements. This paper intends to contribute to the knowledge of the behavior of lime mortar masonry, by exploring the mechanical properties of clay brick masonry bound with both hydraulic and non-hydraulic lime mortars. Masonry wallettes built with a (non-hydraulic) low-strength, calcium lime binder (CL90-s) and a natural-hydraulic-lime...

  16. Compressive strength of fungal and oral biofilms: biological and environmental influences

    OpenAIRE

    Paramonova, Ekaterina

    2009-01-01

    Biofilms play an important role in medically-related fields as they are a major cause of many clinical infections. Knowledge about properties of medically-related biofilms can be beneficial for making predictions about effectiveness of treatments and for development of new medications. In my thesis I investigated which factors influence strength of fungal biofilms of Candida species and oral biofilms. C. albicans is the most frequently isolated fungal species in clinical infections; other Can...

  17. Factors affecting early compressive strength of alkali activated fly ash (OPC-free) concrete

    OpenAIRE

    Fernández-Jiménez, Ana; Palomo, A.

    2007-01-01

    This paper presents the findings of experimental research into the chief characteristics of a new type of concrete made solely with alkali activated fly ash (AAFA): i.e., free of ordinary Portland cement (OPC). The results of testing to determine specific properties of the fresh concrete and the development of its mechanical strength showed that most of the factors that affect the manufacture and final properties of Portland cement concrete (water/cement ratio, curing conditions, etc...

  18. STUDIES ON EFFECT OF PERCENTAGE OF CARBON ON THE TENSILE & COMPRESSIVE STRENGTH OF STRUCTURAL STEEL

    OpenAIRE

    JAI PRAKASH SHARMA; SACHIN CHATURVEDI; PAWAN ARORA

    2012-01-01

    The basic necessity of performing these process is that to improve the tensile strength, hardness, dimensional stability & wear resistance by passing the material through cooled area which enhance the hardness of the material because there is an increment takes place in the percentage of martensite in the structure. If such type of process are used in manufacturing the steel of different category which enhances the properties of material at the stage of cooling in negative temperature with th...

  19. Spall strength and ejecta production of gold under explosively driven shock wave compression

    Energy Technology Data Exchange (ETDEWEB)

    La Lone, B. M. [National Security Technologies, LLC. (NSTec), Mercury, NV (United States); Stevens, G. D. [National Security Technologies, LLC. (NSTec), Mercury, NV (United States); Turley, W. D. [National Security Technologies, LLC. (NSTec), Mercury, NV (United States); Veeser, L. R. [National Security Technologies, LLC. (NSTec), Mercury, NV (United States); Holtkamp, D. B. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2013-12-16

    Explosively driven shock wave experiments were conducted to characterize the spall strength and ejecta production of high-purity cast gold samples. The samples were from 0.75 to 1.84 mm thick and 30 mm in diameter. Peak stresses up to 44 GPa in gold were generated using PBX-9501 high explosive. Sample free surface and ejecta velocities were recorded using photonic Doppler velocimetry techniques. Lithium niobate pins were used to quantify the time dependence of the ejecta density and the total ejected mass. An optical framing camera for time-resolved imaging and a single-image x-ray radiograph were used for additional characterization. Free surface velocities exhibited a range of spall strengths from 1.7 to 2.4 GPa (mean: 2.0 ±0.3 GPa). The pullback signals were faint, minimal ringing was observed in the velocity records, and the spall layer continued to decelerate after first pull back. These results suggest finite tensile strength was present for some time after the initial void formation. Ejecta were observed for every sample with a roughened free surface, and the ejecta density increased with increased surface roughness, which was different in every experiment. The total ejected mass is consistent with the missing mass model.

  20. Novel tricalcium silicate/magnesium phosphate composite bone cement having high compressive strength, in vitro bioactivity and cytocompatibility.

    Science.gov (United States)

    Liu, Wenjuan; Zhai, Dong; Huan, Zhiguang; Wu, Chengtie; Chang, Jiang

    2015-07-15

    Although inorganic bone cements such as calcium phosphate cements have been widely applied in orthopaedic and dental fields because of their self-setting ability, development of high-strength bone cement with bioactivity and biodegradability remains a major challenge. Therefore, the purpose of this study is to prepare a tricalcium silicate/magnesium phosphate (C3S/MPC) composite bone cement, which is intended to combine the excellent bioactivity of C3S with remarkable self-setting properties and mechanical strength of MPC. The self-setting and mechanical properties, in vitro induction of apatite formation and degradation behaviour, and cytocompatibility of the composite cements were investigated. Our results showed that the C3S/MPC composite cement with an optimal composition had compressive strength up to 87 MPa, which was significantly higher than C3S (25 MPa) and MPC (64 MPa). The setting time could be adjusted between 3 min and 29 min with the variation of compositions. The hydraulic reaction products of the C3S/MPC composite cement were composed of calcium silicate hydrate (CSH) derived from the hydration of C3S and gel-like amorphous substance. The C3S/MPC composite cements could induce apatite mineralization on its surface in SBF solution and degraded gradually in Tris-HCl solution. Besides, the composite cements showed good cytocompatibility and stimulatory effect on the proliferation of MC3T3-E1 osteoblast cells. Our results indicated that the C3S/MPC composite bone cement might be a new promising high-strength inorganic bioactive material which may hold the potential for bone repair in load-bearing site. PMID:25890099

  1. Compressive yield strength of the nanocrystalline Cu with Al{sub 2}O{sub 3} dispersoid

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Seung J., E-mail: sjhwang@daejin.ac.kr [Department of Materials Science and Engineering, Daejin University, Pocheon, Kyung-gi 487-711 (Korea, Republic of)

    2011-02-03

    Research highlights: > 0.2% yield stress of the HPed nc-Cu with the 4 vol.% of the Al{sub 2}O{sub 3} dispersoids is as high as 863 MPa > The major contribution to total yield strength of the nc-Cu (25.5 nm) with Al{sub 2}O{sub 3} (4 nm, 4 vol.%) dispersoid is attributed to the grain size of the Cu. - Abstract: Nanocrystalline (nc) Cu with Al{sub 2}O{sub 3} dispersoid ({approx}4 vol.%) was successfully synthesized by simple cryo-milling at 210 K with a mixture of Cu{sub 2}O, Al, and Cu elemental powders. The milled powder was consolidated by hot pressing (HP) at 1123 K and 50 MPa for 2 h. TEM (Transmission Electron Microscopy) work revealed that both of the milled powder and the hot pressed (HPed) materials were comprised with a mixture of the nc-Cu and homogeneous distribution of Al{sub 2}O{sub 3} dispersoids. The compressive and micro Vickers hardness tests were performed on the HPed materials (nanocrystalline Cu with 4 vol.% of Al{sub 2}O{sub 3} dispersoid) at room temperature to characterize the mechanical properties of the materials. The compressive yield strength of the materials was as high as 863 MPa; the micro Vickers hardness 2600 MPa. The results of the mechanical tests apparently show that the relationship between the yield strength and the micro hardness of the HPed materials is in well agreement with Tabor's rule, H{sub v} = 3{sigma}{sub y} in MPa. The grain size of the nc-Cu was estimated by XRD using Scherrer's formula and TEM observation; the Al{sub 2}O{sub 3} dispersoid size was measured from element mapping by STEM-EDS (Scanning Transmission Electron Microscopy-Energy Dispersive Spectroscopy) works. An attempt was made to quantify the possible strengthening effects of the nc-Cu materials with Al{sub 2}O{sub 3} dispersoid. Two strengthening mechanisms were proposed for high hardness and yield strength of the materials, i.e., grain size and dispersion hardening effects.

  2. Modeling and analysis of porosity and compressive strength of gradient Al2O3-ZrO2 ceramic filter using BP neural network

    OpenAIRE

    Li Qiang; Zhang Fengfeng; Yu Jingyuan

    2013-01-01

    BP neural network was used in this study to model the porosity and the compressive strength of a gradient Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting. The influences of the load applied on the epispastic polystyrene template (F), the centrifugal acceleration (v) and sintering temperature (T) on the porosity (P) and compressive strength (?) of the sintered products were studied by using the registered three-layer BP model. The accuracy of the model was verified by compa...

  3. Optimizing the Compressive Strength of Strain-Hardenable Stretch-Formed Microtruss Architectures

    Science.gov (United States)

    Yu, Bosco; Abu Samk, Khaled; Hibbard, Glenn D.

    2015-05-01

    The mechanical performance of stretch-formed microtrusses is determined by both the internal strut architecture and the accumulated plastic strain during fabrication. The current study addresses the question of optimization, by taking into consideration the interdependency between fabrication path, material properties and architecture. Low carbon steel (AISI1006) and aluminum (AA3003) material systems were investigated experimentally, with good agreement between measured values and the analytical model. The compressive performance of the microtrusses was then optimized on a minimum weight basis under design constraints such as fixed starting sheet thickness and final microtruss height by satisfying the Karush-Kuhn-Tucker condition. The optimization results were summarized as carpet plots in order to meaningfully visualize the interdependency between architecture, microstructural state, and mechanical performance, enabling material and processing path selection.

  4. The strength of ruby from X-ray diffraction under non-hydrostatic compression to 68 GPa

    Science.gov (United States)

    Dong, Haini; Dorfman, Susannah M.; Wang, Jianghua; He, Duanwei; Duffy, Thomas S.

    2014-07-01

    Polycrystalline ruby (?-Al2O3:Cr3+), a widely used pressure calibrant in high-pressure experiments, was compressed to 68.1 GPa at room temperature under non-hydrostatic conditions in a diamond anvil cell. Angle-dispersive X-ray diffraction experiments in a radial geometry were conducted at beamline X17C of the National Synchrotron Light Source. The stress state of ruby at high pressure and room temperature was analyzed based on the measured lattice strain. The differential stress of ruby increases with pressure from ~3.4 % of the shear modulus at 18.5 GPa to ~6.5 % at 68.1 GPa. The polycrystalline ruby sample can support a maximum differential stress of ~16 GPa at 68.1 GPa under non-hydrostatic compression. The results of this study provide a better understanding of the mechanical properties of this important material for high-pressure science. From a synthesis of existing data for strong ceramic materials, we find that the high-pressure yield strength correlates well with the ambient pressure Vickers hardness.

  5. In Vitro Comparison of Compressive and Tensile Strengths ofAcrylic Resins Reinforced by Silver Nanoparticles at 2% and0.2% Concentrations

    Science.gov (United States)

    Ghaffari, Tahereh; Hamedirad, Fahimeh; Ezzati, Baharak

    2014-01-01

    Background and aims. Polymethyl methacrylate, PMMA, is widely used in prosthodontics for fabrication of removable prostheses. This study was undertaken to investigate the effect of adding silver nanoparticles (AgNPs) to PMMA at 2% and 0.2% concentrations on compressive and tensile strengths of PMMA. Materials and methods. The silver nanoparticles were mixed with heat-cured acrylic resin in an amalgamator in two groups at 0.2 and 2 wt% of AgNPs. Eighteen 2×20×200-mm samples were prepared for tensile strength test, 12 samples containing silver nanoparticle and 6 samples for the control group. Another 18 cylindrical 25×38-mm samples were prepared for compressive strength test. Scanning electron microscopy was used to verify homogeneous distribution of particles. The powder was manually mixed with a resin monomer and then the mixture was properly blended. Before curing, the paste was packed into steel molds. After curing, the specimens were removed from the molds. One-way ANOVA was used for statistical analysis, followed by multiple comparison test (Scheffé’s test). Results. This study showed that the mean compressive strength of PMMA reinforced with AgNPs was significantly higher than that of the unmodified PMMA (PBased on the results and the desirable effect of nanoparticles of silver on improvement of compressive strength of PMMA, use of this material with proper concentration in the palatal area of maxillary acrylic resin dentures is recommended. PMID:25587381

  6. Effect of the Forming Conditions on the Compressive Strength of Fuel Elements for HTGR

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chung Yong; Lee, Seung Jae; Suh, Jung Min; Jo, Young Ho [KEPCO Nuclear Fuel Co., Daejeon (Korea, Republic of); Lee, Young Woo [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-05-15

    Generation-IV reactors have been developed for the safety, high burn-up, long-term irradiation cycle and the hydrogen production. High Temperature Gas cooled Reactor (HTGR), one of the Gen-IV reactors, uses the fuel element which is manufactured by mixing and combining TRISO particles with graphite powder. The graphite powder is pressed with TRISO particles, previously formed with chemical bonding by pyrolizing with FB-CVD (Fluidized Bed-Chemical Vapor Deposition). H-451 Graphite for HTGR was qualified by NRC in the past, but is no longer available. Therefore, the research for new graphite will be necessary. There are many candidates from the graphite powder suppliers such as SGL cop., Graftech and Toyo Tanso suggested by NRC. The most important point of the graphite matrix is the strength for the high reliability, because the graphite matrix should be enable to protect the TRISO particles from the irradiation environment and the impact from the outside. In this research, several kinds of graphite and PVB as binder were chosen and mixed with each other for strength test. The objective of this research is to evaluate and optimize the kind and composition of the graphites and the forming process

  7. Non-Uniform Compressive Strength of Debonded Sandwich Panels : II. Fracture Mechanics Investigation

    DEFF Research Database (Denmark)

    Berggreen, Carl Christian; Simonsen, Bo Cerup

    2005-01-01

    This article describes the development, validation and application of a FEM based numerical model for prediction of residual strength of damaged sandwich panels. The core of the theoretical method is a newly developed procedure for prediction of the propagation of a face-core debond. As demonstrated, the method can predict the maximum load carrying capacity of real-life panels with debond damages, where the failure is governed by face-sheet buckling followed by debond growth. The developed theoretical procedure is an extension of the as Crack Surface Displacement method, here denoted as the Crack Surface Displacement Extrapolation method. The method is first developed in 2D and then extended to 3D by use of a number of realistic assumptions for the considered configurations. Comparison of the theoretical predictions to a series of large-scale experiments, described in Nøkkentved et al.(2005)., shows that the model is indeed able to predict the failure modes and the residual strength of damaged panels with accuracy sufficient for practical applications. This opens up for a number of important engineering applications, for example risk-based inspection and repair schemes.

  8. STUDIES ON EFFECT OF PERCENTAGE OF CARBON ON THE TENSILE & COMPRESSIVE STRENGTH OF STRUCTURAL STEEL

    Directory of Open Access Journals (Sweden)

    JAI PRAKASH SHARMA

    2012-05-01

    Full Text Available The basic necessity of performing these process is that to improve the tensile strength, hardness, dimensional stability & wear resistance by passing the material through cooled area which enhance the hardness of the material because there is an increment takes place in the percentage of martensite in the structure. If such type of process are used in manufacturing the steel of different category which enhances the properties of material at the stage of cooling in negative temperature with the use of liquid nitrogen or other cooling media & all these products are used in different areas with greater performance. Result shows that the tensile strength of material is increased as we cool the material in negative temperature within the same elongation after its manufacture i.e. 741.27 N/mm² to maximum of 793 N/mm² at -15OC & 802 N/mm² at -30OC & 168.25 BHN to a maximum of 199 BHN at -15OC & 260 BHN at -30OC after cold treatment.

  9. Unconfined versus confined speleogenetic settings: variations of solution porosity.

    OpenAIRE

    Klimchouk,A.B.

    2006-01-01

    Speleogenesis in confined settings generates cave morphologies that differ much from those formed in unconfined settings. Caves developed in unconfined settings are characterised by broadly dendritic patterns of channels due to highly competing development. In contrast, caves originated under confined conditions tend to form two- or three-dimensional mazes with densely packed conduits. This paper illustrates variations of solution (channel) porosity resulted from speleogenesis in unconfined ...

  10. Understanding size effects on the strength of single crystals through high-temperature micropillar compression

    International Nuclear Information System (INIS)

    Compression tests of ?1 1 1?-oriented LiF single-crystal micropillars 1–5 ?m in diameter were carried out from 25 °C to 250 °C. While the flow stress at ambient temperature was independent of the micropillar diameter, a strong size effect developed with elevated temperature. This behavior was explained by rigorously accounting for the different contributions to the flow stress of the micropillars as a function of temperature and pillar diameter: the lattice resistance, the forest hardening; and the size-dependent contribution as a result of the operation of single-arm dislocation sources. This was possible because the micropillars were obtained by chemically etching away the surrounding matrix in directionally solidified LiF–NaCl and LiF–KCl eutectics, avoiding any use of focused ion beam methods, yielding micropillars with a controlled dislocation density, independent of the sample preparation technique. In particular, the role of the lattice resistance on the size effect of micrometer-size single crystals was demonstrated unambiguously for the first time. This result rationalizes the different values of power-law exponent for the size effect found in the literature for face-centered cubic and body-centered cubic metals as well as for covalent and ionic solids

  11. Phase transition and strength of vanadium under shock compression up to 88?GPa

    International Nuclear Information System (INIS)

    A series of reverse-impact experiments were performed on vanadium at shock pressure ranging from 32?GPa to 88?GPa. Particle velocity profiles measured at sample/LiF window interface were used to estimate the sound velocities, shear modulus, and yield stress in shocked vanadium. A phase transition at ?60.5?GPa that may be the body-centered cubic (BCC) to rhombohedral structure was identified by the discontinuity of the sound velocity against shock pressure. This transition pressure is consistent with the results from diamond anvil cell (DAC) experiments and first-principle calculations. However, present results show that the rhombohedral phase has higher strength and shear modulus than the BCC phase, which is contrast to the findings from DAC experiments and theoretical work

  12. Phase transition and strength of vanadium under shock compression up to 88?GPa

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Yuying, E-mail: yuyinyu@caep.cn; Tan, Ye; Dai, Chengda; Li, Xuemei; Li, Yinghua; Wu, Qiang; Tan, Hua [Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, Chinese Academy of Engineering Physics, P. O. Box 919-102, Mianyang, Sichuan 621900 (China)

    2014-11-17

    A series of reverse-impact experiments were performed on vanadium at shock pressure ranging from 32?GPa to 88?GPa. Particle velocity profiles measured at sample/LiF window interface were used to estimate the sound velocities, shear modulus, and yield stress in shocked vanadium. A phase transition at ?60.5?GPa that may be the body-centered cubic (BCC) to rhombohedral structure was identified by the discontinuity of the sound velocity against shock pressure. This transition pressure is consistent with the results from diamond anvil cell (DAC) experiments and first-principle calculations. However, present results show that the rhombohedral phase has higher strength and shear modulus than the BCC phase, which is contrast to the findings from DAC experiments and theoretical work.

  13. The influence of clay additives in Portland cement on the compressive strength of the cement stone

    Directory of Open Access Journals (Sweden)

    A.R. Gaifullin

    2015-11-01

    Full Text Available The introduction of mineral additives to binders, especially to Portland cement, is one of the promising trends for solving the resource and energy saving problems, as well as problems of environmental protection during production and application. Expanding the supplementary cementitious materials resource base can be achieved through the use of natural pozzolans and thermally activated polymineral clays(commonly known as glinites in Russia. One type of glinite is metakaolin, which is obtained by calcination of kaolin clays. Metakaolin is widely and effectively used as a pozzolanic additive due to its beneficial effect on the physical and mechanical properties of Portland cement-based materials. The obstacle to its wide production and use are the limited deposits of pure kaolin clays in many countries, including the Russian Federation. In this respect, the studies of pozzolanic activity of the most common mineral clays and their use in some countries have significantly advanced. Similar studies were widely performed in the 1940s in USSR. It seems reasonable to renew this trend to provide a scientific base for the production of local pozzolans made of clays commonly used in different regions. Comparative studies of the effect of 5 clays differing in mineral and chemical composition, calcination temperature and specific surface area, and high-quality metakaolin, on the strength of hardened Portland cement paste have been performed. It has been established that introducing 5…10 % of composite clays calcined at 400…8000 C° and milled to a specific surface area of 290…800 m2/kg into Portland cement enhanced the strength of the hardened cement paste considerably better than the introduction of metakaolin with a specific surface area of 1200 m2/kg. The findings of the study suggest that many kinds of commonly used polymineral clays have a specific calcination temperature and dispersity, which results in a higher pozzolanic activity compared with metakaolin.

  14. Assessment of compression and strength of divergent screws mounted on miniplates for fixation of mandibular fractures: an in vitro experimental study.

    Science.gov (United States)

    Jafarian, M; Pourdanesh, F; Esmaeelinejad, M; Dehghani, N; Aghdashi, F; Tabrizi, R

    2015-09-01

    An efficient band of tension is critical for the adequate fixation of mandibular fractures, so fixation devices that compress are helpful. We aimed to evaluate the possibility of creating compression using screws inserted divergently into miniplates placed in the tension zone of mandibular fractures and record the effects on the strength of fixation. For this in vitro experimental study we prepared 20 sheep hemimandibles. After angle fractures had been created, the specimens were divided into standard and study groups (n=10 in each). In the standard group the tension zones were fixed in the standard manner with 4-hole miniplates and 4 parallel screws. Those in the study group were fixed as for the standard group but with 4×45° divergent screws. The differences in the gap in the fracture line before and after fixation were measured as indicators of compression. The strength of fixation was also assessed with a universal testing machine in vitro. The amount of compression was significant only in the study group (pfracture line. Insertion of divergent screws in miniplates may create compression between fractured segments without jeopardising the strength of fixation. PMID:25921364

  15. Comparative analysis of compressive strength tests at age of 28 and 90 days and density of products using chemical additives in cementing radioactive waste

    International Nuclear Information System (INIS)

    In this research it has been studied the effects of chemical additives (admixtures) in the cementation process of radioactive wastes, which are used to improve the properties of waste cementation process, both of the paste and of the solidified product. However there are a large variety of these materials that are frequently changed or taken out of the market, then it is essential to know the commercially available materials and their effects. The tests were carried out with a solution simulating the evaporator concentrate waste coming from PWR nuclear reactors. It was cemented using two formulations, A and B, incorporating higher or lower amount of waste, respectively. It was added chemical admixtures from two manufacturers (S and H), which were: accelerators, set retarders and superplasticizers. The experiments were organized by a factorial design 23. The measured parameters were the viscosity, the setting time, the paste and product density and the compressive strength. In this study we performed comparative analyzes of the results of compressive strength at age of 28 and 90 days and between the densities of the samples at the same ages.The compressive strength test at age of 28 days is considered a parameter essential issues related to security handling, transport and storage of cemented waste product. The results showed that the addition of accelerators improved the compressive strength of the cemented product, but presented lower values density products. (author)

  16. Comparative analysis of compressive strength tests at age of 28 and 90 days and density of products using chemical additives in cementing radioactive waste

    Energy Technology Data Exchange (ETDEWEB)

    Vieira, Vanessa Mota; Tello, Cledola Cassia Oliveira de, E-mail: vanessamotavieira@gmail.com, E-mail: tellocc@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2013-07-01

    In this research it has been studied the effects of chemical additives (admixtures) in the cementation process of radioactive wastes, which are used to improve the properties of waste cementation process, both of the paste and of the solidified product. However there are a large variety of these materials that are frequently changed or taken out of the market, then it is essential to know the commercially available materials and their effects. The tests were carried out with a solution simulating the evaporator concentrate waste coming from PWR nuclear reactors. It was cemented using two formulations, A and B, incorporating higher or lower amount of waste, respectively. It was added chemical admixtures from two manufacturers (S and H), which were: accelerators, set retarders and superplasticizers. The experiments were organized by a factorial design 2{sup 3}. The measured parameters were the viscosity, the setting time, the paste and product density and the compressive strength. In this study we performed comparative analyzes of the results of compressive strength at age of 28 and 90 days and between the densities of the samples at the same ages.The compressive strength test at age of 28 days is considered a parameter essential issues related to security handling, transport and storage of cemented waste product. The results showed that the addition of accelerators improved the compressive strength of the cemented product, but presented lower values density products. (author)

  17. Properties of confined and unconfined water

    OpenAIRE

    Guse, Christa

    2011-01-01

    The aim of this work is to add to the long lasting efforts to provide an unified picture of the properties of confined and unconfined water. Water is an ubiquitous substance with special importance for geological and biological as well as technical processes. There are 1.4 billion km3 of water on earth, most of it in liquid form, 0.001% as vapor in the atmosphere and 1.8% as ice (mainly crystalline hexagonal ice Ih) frozen at the poles and in Greenland [1]. But water can also exist in an amor...

  18. Strength and deformability of compressed concrete elements with various types of non-metallic fiber and rods reinforcement under static loading

    Science.gov (United States)

    Nevskii, A. V.; Baldin, I. V.; Kudyakov, K. L.

    2015-01-01

    Adoption of modern building materials based on non-metallic fibers and their application in concrete structures represent one of the important issues in construction industry. This paper presents results of investigation of several types of raw materials selected: basalt fiber, carbon fiber and composite fiber rods based on glass and carbon. Preliminary testing has shown the possibility of raw materials to be effectively used in compressed concrete elements. Experimental program to define strength and deformability of compressed concrete elements with non-metallic fiber reinforcement and rod composite reinforcement included design, manufacture and testing of several types of concrete samples with different types of fiber and longitudinal rod reinforcement. The samples were tested under compressive static load. The results demonstrated that fiber reinforcement of concrete allows increasing carrying capacity of compressed concrete elements and reducing their deformability. Using composite longitudinal reinforcement instead of steel longitudinal reinforcement in compressed concrete elements insignificantly influences bearing capacity. Combined use of composite rod reinforcement and fiber reinforcement in compressed concrete elements enables to achieve maximum strength and minimum deformability.

  19. Factors affecting early compressive strength of alkali activated fly ash (OPC-free concrete

    Directory of Open Access Journals (Sweden)

    Palomo, A.

    2007-08-01

    Full Text Available This paper presents the findings of experimental research into the chief characteristics of a new type of concrete made solely with alkali activated fly ash (AAFA: i.e., free of ordinary Portland cement (OPC. The results of testing to determine specific properties of the fresh concrete and the development of its mechanical strength showed that most of the factors that affect the manufacture and final properties of Portland cement concrete (water/cement ratio, curing conditions, etc. also impact the preparation and final quality of this new material. A number of parameters specific to AAFA concrete (nature and concentration of alkali present in the system were also explored to determine their role in the setting and hardening process.Este trabajo presenta los resultados de una investigación experimental llevada a cabo para evaluar las principales características de un nuevo tipo de hormigón fabricado solamente con ceniza volante activada alcalinamente (AAFA; es decir, sin cemento Portland comercial (OPC. Los resultados de los ensayos realizados para determinar las propiedades específicas del hormigón fresco y el desarrollo de resistencias mecánicas mostraron que la mayoría de los factores que afectan al proceso de fabricación y a las propiedades finales de los hormigones de cemento Portland (relación agua/cemento, condiciones de curado, etc. también afectan a la preparación y calidad final de estos nuevos materiales. También fueron estudiados otros parámetros específicos de los hormigones de AAFA (la naturaleza y concentración del álcali presente en el sistema para determinar su papel en el proceso de fraguado y endurecimiento.

  20. Concrete compressive characteristic strength analysis of pile caps with three piles / Análise da resistência característica à compressão do concreto em blocos sobre três estacas

    Scientific Electronic Library Online (English)

    T. E.T., Buttignol; L.C., Almeida.

    2013-02-01

    Full Text Available Este trabalho tem por objetivo realizar uma análise numérica da influência da resistência característica à compressão do concreto (fck) em blocos sobre três estacas. Para tanto, foi utilizado um modelo-padrão de bloco sobre três estacas originalmente desenvolvido por Miguel [1]. A partir deste model [...] o foram realizadas variações na resistência à compressão do concreto de modo a se observar modificações no comportamento estrutural do elemento. A análise numérica é desenvolvida por meio de programa de computador baseado no MEF. Os resultados demonstraram que o aumento do fck não provocou um aumento significativo da resistência do bloco, visto que a ruína dos modelos ocorreu devido ao fendilhamento (desenvolvimento de tensões de tração perpendiculares às bielas comprimidas) e escoamento da armadura dos tirantes. Nos modelos analisados desenvolveram-se tensões de tração elevadas ao longo das bielas e na seção inferior do bloco, demonstrando que a resistência última dos blocos não é função da resistência à compressão. Abstract in english In this paper a numerical analysis of three-pile caps is developed to study the influence of concrete compressive characteristic strength in pile caps resistance capacity. A three-pile cap model derived from Miguel's [1] work was adopted. From this model, variations on the compressive characteristic [...] strength were made in order to observe modifications in its structural behavior. The numerical analysis was developed with finite element software ATENA 3D [2]. The results demonstrated that an increase in the compressive characteristic strength was not followed by a significant increment in pile cap's strength, since models' ruin were due to concrete splitting (opening cracks parallel to principal compressive stresses as a result of perpendicular tension stresses within the structure) and ties steel bars yielding. In the models analyzed high-tension stresses were developed along the struts and at the bottom of the pile cap's section, demonstrating that pile cap's ultimate resistance is not influenced by the compressive strength.

  1. In Vitro Comparison of Compressive and Tensile Strengths of Acrylic Resins Reinforced by Silver Nanoparticles at 2% and 0.2% Concentrations

    Directory of Open Access Journals (Sweden)

    Tahereh Ghaffari

    2014-12-01

    Full Text Available Background and aims. Polymethyl methacrylate, PMMA, is widely used in prosthodontics for fabrication of removable prostheses. This study was undertaken to investigate the effect of adding silver nanoparticles (AgNPs to PMMA at 2% and 0.2% concentrations on compressive and tensile strengths of PMMA. Materials and methods. The silver nanoparticles were mixed with heat-cured acrylic resin in an amalgamator in two groups at 0.2 and 2 wt% of AgNPs. Eighteen 2×20×200-mm samples were prepared for tensile strength test, 12 samples containing silver nanoparticle and 6 samples for the control group. Another 18 cylindrical 25×38-mm samples were prepared for compressive strength test. Scanning electron microscopy was used to verify homogeneous distribution of particles. The powder was manually mixed with a resin monomer and then the mixture was properly blended. Before curing, the paste was packed into steel molds. After curing, the specimens were removed from the molds. One-way ANOVA was used for statistical analysis, followed by multiple comparison test (Scheffé’s test. Results. This study showed that the mean compressive strength of PMMA reinforced with AgNPs was significantly higher than that of the unmodified PMMA (P<0.05. It was not statistically different between the two groups reinforced with AgNPs. The tensile strength was not significantly different between the 0.2% group and unmodified PMMA and it decreased significantly after incorporation of 2% AgNPs (P<0.05. Conclusion. Based on the results and the desirable effect of nanoparticles of silver on improvement of compressive strength of PMMA, use of this material with proper concentration in the palatal area of maxillary acrylic resin dentures is recommended.

  2. In Vitro Comparison of Compressive and Tensile Strengths ofAcrylic Resins Reinforced by Silver Nanoparticles at 2% and0.2% Concentrations.

    Science.gov (United States)

    Ghaffari, Tahereh; Hamedirad, Fahimeh; Ezzati, Baharak

    2014-01-01

    Background and aims. Polymethyl methacrylate, PMMA, is widely used in prosthodontics for fabrication of removable prostheses. This study was undertaken to investigate the effect of adding silver nanoparticles (AgNPs) to PMMA at 2% and 0.2% concentrations on compressive and tensile strengths of PMMA. Materials and methods. The silver nanoparticles were mixed with heat-cured acrylic resin in an amalgamator in two groups at 0.2 and 2 wt% of AgNPs. Eighteen 2×20×200-mm samples were prepared for tensile strength test, 12 samples containing silver nanoparticle and 6 samples for the control group. Another 18 cylindrical 25×38-mm samples were prepared for compressive strength test. Scanning electron microscopy was used to verify homogeneous distribution of particles. The powder was manually mixed with a resin monomer and then the mixture was properly blended. Before curing, the paste was packed into steel molds. After curing, the specimens were removed from the molds. One-way ANOVA was used for statistical analysis, followed by multiple comparison test (Scheffé's test). Results. This study showed that the mean compressive strength of PMMA reinforced with AgNPs was significantly higher than that of the unmodified PMMA (P<0.05). It was not statistically different between the two groups reinforced with AgNPs. The tensile strength was not significantly different between the 0.2% group and unmodified PMMA and it de-creased significantly after incorporation of 2% AgNPs (P<0.05). Conclusion. Based on the results and the desirable effect of nanoparticles of silver on improvement of compressive strength of PMMA, use of this material with proper concentration in the palatal area of maxillary acrylic resin dentures is recommended. PMID:25587381

  3. RESIDUAL COMPRESSIVE STRENGTH OF FLY ASH BASED GLASS FIBRE REINFORCED HIGH PERFORMANCE CONCRETE SUBJECTED TO ACID ATTACK

    Directory of Open Access Journals (Sweden)

    Dr.H.Sudarsana Rao

    2012-01-01

    Full Text Available In recent years, improvements in concrete properties have been achieved by the invention of High- Performance-Concrete (HPC. Improvements involving a combination of improved compaction, improved paste characteristics and aggregate-matrix bond, and reduced porosity are achieved through HPC. The ductility of HPC can be improved by altering its composition through the addition of glass fibers in the design mix. High- Performance-Concrete made with glass fibers inside is regarded as Glass Fiber Reinforced High Performance Concrete (GFRHPC. This paper presents the details of an experimental investigation planned to utilize fly ash in the production of Glass fibre reinforced High-Performance-Concrete (GFRHPC. The investigation examines the progressive deterioration of concrete mixtures containing various combinations of fly ash based GFRHPCmixes exposed to sulphate and chloride solutions. Acid attack tests have been conducted to measure the durability of GFRHPC. Cubes of 150X150X150 mm have been cast, cured and then kept immersed in 5%concentrated solutions of HCl, H2SO4 and MgSO4 for 30, 60 and 90 days and then tested to record the residual compressive strengths of GFRHPC produced with the fly ash mineral admixtures. The results have been analyzed and useful conclusions have been drawn.

  4. The influence of hybridization on impact damage behavior and residual compression strength of intraply basalt/nylon hybrid composites

    International Nuclear Information System (INIS)

    Highlights: ? The impact performances of basalt/nylon intraply hybrid composites were studied. ? In basalt/nylon composite, the excellent impact resistance of nylon fiber was used. ? At high impact energy, the hybrid composite have a better property than the pure ones. ? The impact property of hybrid samples is significantly affected by the fiber content. ? SEM analyses show that hybridization can prevent of catastrophic and complete failure. -- Abstract: Low-velocity impact and compression after impact (CAI) tests were performed to investigate the impact behavior of hybrid composite laminates reinforced by basalt-nylon intraply fabrics. The purpose of using this hybrid composite is to combine the good mechanical property of basalt fiber as a brittle fiber with the excellent impact resistance of nylon fiber as a ductile fiber. Five different types of woven fabric with different contents of nylon (0%, 25%, 33.3%, 50% and 100%) were used as reinforcement. The effect of nylon/basalt fiber content on impact parameters, impact damage behavior and CAI strength was studied at different nominal impact energy levels (16, 30 and 40 J). The results indicate that at low impact energy, hybridization and variation in basalt/nylon fiber content cannot improve the impact performance of composite plates. With increasing impact energy, the impact performance becomes more and more dependent on the content of nylon and basalt.

  5. Compressive strength and interfacial transition zone of sugar cane bagasse ash concrete: A comparison to the established pozzolans

    Science.gov (United States)

    Hussein, Asma Abd Elhameed; Shafiq, Nasir; Nuruddin, Muhd Fadhil

    2015-05-01

    Agricultural and industrial by-products are commonly used in concrete production as cement replacement materials (CRMs) or as admixtures to enhance both fresh and hardened properties of concrete as well as to save the environment from the negative effects caused by their disposal. Sugar Cane Bagasse Ash (SCBA) is one of the promising CRMs, it is used as a partial replacement of cement for producing concrete; properties of such concrete depend on the chemical composition, fineness, and burning temperature of SCBA. Approximately 1500 Million tons of sugarcane are annually produced over all the world which leave about 40-45% bagasse after juice crushing for sugar industry giving an average annual production of about 600 Million tons of bagasse as a waste material. This paper presents some findings on the effect of SCBA on workability, compressive strength and microstructure of interfacial zone of concrete and its performance is compared to some of the established CRMs namely Densified Silica Fume, Fly Ash and Microwave Incinerated Rice Husk Ash.

  6. Modeling Decomposition of Unconfined Rigid Polyurethane Foam

    Energy Technology Data Exchange (ETDEWEB)

    CHU,TZE YAO; ERICKSON,KENNETH L.; HOBBS,MICHAEL L.

    1999-11-01

    The decomposition of unconfined rigid polyurethane foam has been modeled by a kinetic bond-breaking scheme describing degradation of a primary polymer and formation of a thermally stable secondary polymer. The bond-breaking scheme is resolved using percolation theory to describe evolving polymer fragments. The polymer fragments vaporize according to individual vapor pressures. Kinetic parameters for the model were obtained from Thermal Gravimetric Analysis (TGA). The chemical structure of the foam was determined from the preparation techniques and ingredients used to synthesize the foam. Scale-up effects were investigated by simulating the response of an incident heat flux of 25 W/cm{sup 2} on a partially confined 8.8-cm diameter by 15-cm long right circular cylinder of foam which contained an encapsulated component. Predictions of center, midradial, and component temperatures, as well as regression of the foam surface, were in agreement with measurements using thermocouples and X-ray imaging.

  7. Modeling Decomposition of Unconfined Rigid Polyurethane Foam

    Energy Technology Data Exchange (ETDEWEB)

    HOBBS,MICHAEL L.; ERICKSON,KENNETH L.; CHU,TZE YAO

    1999-11-08

    The decomposition of unconfined rigid polyurethane foam has been modeled by a kinetic bond-breaking scheme describing degradation of a primary polymer and formation of a thermally stable secondary polymer. The bond-breaking scheme is resolved using percolation theory to describe evolving polymer fragments. The polymer fragments vaporize according to individual vapor pressures. Kinetic parameters for the model were obtained from Thermal Gravimetric Analysis (TGA). The chemical structure of the foam was determined from the preparation techniques and ingredients used to synthesize the foam. Scale-up effects were investigated by simulating the response of an incident heat flux of 25 W/cm{sup 2} on a partially confined 8.8-cm diameter by 15-cm long right circular cylinder of foam that contained an encapsulated component. Predictions of center, midradial, and component temperatures, as well as regression of the foam surface, were in agreement with measurements using thermocouples and X-ray imaging.

  8. Effects of coating thickness and interfacial roughness on cracking and delamination strength of WC-Co coating measured by ring compression test

    Science.gov (United States)

    Kato, Masahiko; Nazul, Mahmoud; Itti, Takeshi; Akebono, Hiroyuki; Sugeta, Atsushi; Mitani, Eiji

    2014-08-01

    The effects of coating thickness and interfacial roughness on the interfacial fracture toughness of tungsten carbide-cobalt (WC-Co) coatings were evaluated using a ring compression test. WC-Co powder was sprayed on steel (JIS:SS400) rings by a high-velocity air- fuel method in coatings with various thicknesses and values of interfacial roughness. The ring compression test was carried out, and the cracking and delamination behavior of the coatings was observed using charge-coupled-device cameras. The results showed that cracking perpendicular to the loading direction occurred in the coatings during the ring compression test, and the cracking strength obtained from the ring compression test decreased slightly with increasing coating thickness, but was independent of the interfacial roughness. Upon further increase of the compression load, the coatings delaminated from the substrate. The interfacial fracture toughness calculated from the delamination of the coatings during the ring compression test decreased with increasing coating thickness and increased with increasing interfacial roughness.

  9. Predicting model on ultimate compressive strength of Al2O3-ZrO2 ceramic foam filter based on BP neural network

    Directory of Open Access Journals (Sweden)

    Yu Jingyuan

    2011-08-01

    Full Text Available In present study, BP neural network model was proposed for the prediction of ultimate compressive strength of Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting. The inputs of the BP neural network model were the applied load on the epispastic polystyrene template (F, centrifugal acceleration (v and sintering temperature (T, while the only output was the ultimate compressive strength (?. According to the registered BP model, the effects of F, v, T on ? were analyzed. The predicted results agree with the actual data within reasonable experimental error, indicating that the BP model is practically a very useful tool in property prediction and process parameter design of the Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting.

  10. Conventional compressive strength parallel to the grain and mechanical resistance of wood against pin penetration and microdrilling established by in-situ semidestructive devices.

    Czech Academy of Sciences Publication Activity Database

    Kloiber, Michal; Drdácký, Miloš; Tippner, J.; Hrivnák, J.

    2015-01-01

    Ro?. 48, ?. 10 (2015), s. 3217-3229. ISSN 1359-5997 R&D Projects: GA MK(CZ) DF11P01OVV001; GA MŠk(CZ) LO1219 Keywords : compressive strength * density * in situ test ing * non-destructive test ing (NDT) * small size loading jack * wood Subject RIV: AL - Art, Architecture, Cultural Heritage Impact factor: 1.714, year: 2014 http://link.springer.com/article/10.1617/s11527-014-0392-6

  11. Linear dimensional change, compressive strength and detail reproduction in type IV dental stone dried at room temperature and in a microwave oven

    OpenAIRE

    Marcos Aurélio Bomfim da Silva; Rafael Pino Vitti; Simonides Consani; Mário Alexandre Coelho Sinhoreti; Marcelo Ferraz Mesquita; Rafael Leonardo Xediek Consani

    2012-01-01

    The type IV dental stone is widely used for the fabrication of dyes and master casts for fixed and removable partial prostheses. It is typically normal to wait at least 24 hours for the casts to dry prior to beginning the laboratory procedures. The waiting time has been shown to be greatly reduced by using microwave drying. OBJECTIVE: This study evaluated the influence of drying techniques at room temperature and microwave oven on the linear dimensional change, compressive strength and detail...

  12. New phosphate-based binder for stabilization of soils contaminated with heavy metals: leaching, strength and microstructure characterization.

    Science.gov (United States)

    Du, Yan-Jun; Wei, Ming-Li; Reddy, Krishna R; Jin, Fei; Wu, Hao-Liang; Liu, Zhi-Bin

    2014-12-15

    Cement stabilization is used extensively to remediate soils contaminated with heavy metals. However, previous studies suggest that the elevated zinc (Zn) and lead (Pb) concentrations in the contaminated soils would substantially retard the cement hydration, leading to the deterioration of the performance of cement stabilized soils. This study presents a new binder, KMP, composed of oxalic acid-activated phosphate rock, monopotassium phosphate and reactive magnesia. The effectiveness of stabilization using this binder is investigated on soils spiked with Zn and Pb, individually and together. Several series of tests are conducted including toxicity characteristic leaching (TCLP), ecotoxicity in terms of luminescent bacteria test and unconfined compressive strength. The leachability of a field Zn- and Pb- contaminated soil stabilized with KMP is also evaluated by TCLP leaching test. The results show that the leached Zn concentrations are lower than the China MEP regulatory limit except when Zn and Pb coexist and for the curing time of 7 days. On the other hand, the leached Pb concentrations for stabilized soils with Pb alone or mixed Zn and Pb contamination are much lower than the China MEP or USEPA regulatory limit, irrespective of the curing time. The luminescent bacteria test results show that the toxicity of the stabilized soils has been reduced considerably and is classified as slightly toxic class. The unconfined compressive strength of the soils decrease with the increase in the Zn concentration. The stabilized soils with mixed Zn and Pb contaminants exhibit notably higher leached Zn concentration, while there is lower unconfined compressive strength relative to the soils when contaminated with Zn alone. The X-ray diffraction and scanning electron microscope analyses reveal the presence of bobierrite (Mg3(PO4)2·8H2O) and K-struvite (MgKPO4·6H2O) as the main products formed in the KMP stabilized uncontaminated soils; the formation of hopeite (Zn3(PO4)2·4H2O), scholzite (CaZn2(PO4)2·2H2O), zinc hydroxide (Zn(OH)2), and fluoropyromorphite (Pb5(PO4)3F) in the soils are the main mechanisms for immobilization of Zn and Pb with the KMP binder. The change in the relative quantities of the formed phosphate-based products, with respect to the Zn concentration and presence of mixed Zn and Pb contaminants, can well explain the measured impact of the Zn concentration levels and presence of both Zn and Pb contaminants on the unconfined compressive strength of the KMP stabilized soils. PMID:25173726

  13. Linear dimensional change, compressive strength and detail reproduction in type IV dental stone dried at room temperature and in a microwave oven

    Scientific Electronic Library Online (English)

    Marcos Aurélio Bomfim da, Silva; Rafael Pino, Vitti; Simonides, Consani; Mário Alexandre Coelho, Sinhoreti; Marcelo Ferraz, Mesquita; Rafael Leonardo Xediek, Consani.

    2012-10-01

    Full Text Available The type IV dental stone is widely used for the fabrication of dyes and master casts for fixed and removable partial prostheses. It is typically normal to wait at least 24 hours for the casts to dry prior to beginning the laboratory procedures. The waiting time has been shown to be greatly reduced b [...] y using microwave drying. OBJECTIVE: This study evaluated the influence of drying techniques at room temperature and microwave oven on the linear dimensional change, compressive strength and detail reproduction in type IV dental stones. MATERIAL AND METHODS: Three type IV dental stone brands were selected; elite Rock, Shera Premium and Durone IV. Two different drying protocols were tested in 4 groups (n=10); G1 - room temperature (25±4ºC) dried for 2 hours; G2 - room temperature dried for 24 hours; G3 - room temperature dried for 7 days and G4 - microwave oven dried at 800 W for 5 minutes and after 2 hours at room temperature. After drying, the samples were assayed for dimensional charges. The sample surface was submitted to the ImageTool 3.0 software for compressive strength in a universal testing machine with a cell load of 50 KN at a crosshead speed of 0.5 mm/minutes and the detail reproduction was analyzed with a stereomicroscope at 25x magnification. The statistical analysis of the linear dimensional change and compressive strength data were conducted by the ANOVA test followed by the Tukey test (p

  14. Linear dimensional change, compressive strength and detail reproduction in type IV dental stone dried at room temperature and in a microwave oven

    Directory of Open Access Journals (Sweden)

    Marcos Aurélio Bomfim da Silva

    2012-10-01

    Full Text Available The type IV dental stone is widely used for the fabrication of dyes and master casts for fixed and removable partial prostheses. It is typically normal to wait at least 24 hours for the casts to dry prior to beginning the laboratory procedures. The waiting time has been shown to be greatly reduced by using microwave drying. OBJECTIVE: This study evaluated the influence of drying techniques at room temperature and microwave oven on the linear dimensional change, compressive strength and detail reproduction in type IV dental stones. MATERIAL AND METHODS: Three type IV dental stone brands were selected; elite Rock, Shera Premium and Durone IV. Two different drying protocols were tested in 4 groups (n=10; G1 - room temperature (25±4ºC dried for 2 hours; G2 - room temperature dried for 24 hours; G3 - room temperature dried for 7 days and G4 - microwave oven dried at 800 W for 5 minutes and after 2 hours at room temperature. After drying, the samples were assayed for dimensional charges. The sample surface was submitted to the ImageTool 3.0 software for compressive strength in a universal testing machine with a cell load of 50 KN at a crosshead speed of 0.5 mm/minutes and the detail reproduction was analyzed with a stereomicroscope at 25x magnification. The statistical analysis of the linear dimensional change and compressive strength data were conducted by the ANOVA test followed by the Tukey test (p<0.05. Detailed reproduction values were reported in percentages. RESULTS: For the compressive strength test, Elite Rock and Durone IV did not present significant differences between G2 and G4, while Shera Premium did not present differences between G3 and G4. The best reproduction levels were observed for G3. CONCLUSIONS: Dental stone microwave oven drying showed a linear dimensional change similar to after room temperature drying for 24 hours and 7 days. The compressive strength of the stone dried in the microwave oven was similar to those dried at room temperature for 24 hours, with the exception of Shera Premium, which had similar results for microwave and room temperature drying for 7 days. For the microwave drying method the detail reproduction levels for samples dried at room temperature for 24 hours and 7 days were similar, except for the Durone IV.

  15. Radial flow towards well in leaky unconfined aquifer

    Science.gov (United States)

    Mishra, P. K.; Kuhlman, K. L.

    2012-12-01

    An analytical solution is developed for three-dimensional flow towards a partially penetrating large- diameter well in an unconfined aquifer bounded below by a leaky aquitard of finite or semi-infinite extent. The analytical solution is derived using Laplace and Hankel transforms, then inverted numerically. Existing solutions for flow in leaky unconfined aquifers neglect the unsaturated zone following an assumption of instantaneous drainage due to Neuman. We extend the theory of leakage in unconfined aquifers by (1) including water flow and storage in the unsaturated zone above the water table, and (2) allowing the finite-diameter pumping well to partially penetrate the aquifer. The investigation of model-predicted results shows that aquitard leakage leads to significant departure from the unconfined solution without leakage. The investigation of dimensionless time-drawdown relationships shows that the aquitard drawdown also depends on unsaturated zone properties and the pumping-well wellbore storage effects.

  16. Unconfined versus confined speleogenetic settings: variations of solution porosity.

    Directory of Open Access Journals (Sweden)

    Klimchouk Alexander

    2006-01-01

    Full Text Available Speleogenesis in confined settings generates cave morphologies that differ much from those formed in unconfined settings. Cavesdeveloped in unconfined settings are characterised by broadly dendritic patterns of channels due to highly competing development.In contrast, caves originated under confined conditions tend to form two- or three-dimensional mazes with densely packed conduits.This paper illustrates variations of solution (channel porosity resulted from speleogenesis in unconfined and confined settings by theanalysis of morphometric parameters of typical cave patterns. Two samples of typical cave systems formed in the respective settingsare compared. The sample that represents unconfined speleogenesis consists of solely limestone caves, whereas gypsum cavesof this type tend to be less dendritic and more linear. The sample that represents confined speleogenesis consists of both limestoneand gypsum maze caves. The comparison shows considerable differences in average values of some parameters between thesettings. Passage network density (the ratio of the cave length to the area of the cave field, km/km2 is one order of magnitudegreater in confined settings than in unconfined (average 167.3 km/km2 versus 16.6 km/km2. Similarly, an order of magnitudedifference is observed in cave porosity (a fraction of the volume of a cave block, occupied by mapped cavities; 5.0 % versus 0.4 %.This illustrates that storage in maturely karstified confined aquifers is generally much greater than in unconfined. The average areal coverage (a fraction of the area of the cave field occupied by passages in a plan view is about 5 times greater in confined settingsthan in unconfined (29.7 % versus 6.4 %. This indicates that conduit permeability in confined aquifers is appreciably easier to targetwith drilling than the widely spaced conduits in unconfined aquifers.

  17. Blast effect from unconfined vapor cloud explosions

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, A.F.; Pritchard, D.K.

    1982-03-01

    Despite a considerable effort to predict the consequences of an unconfined vapour cloud explosion (UVCE) at a petro-chemical site, the major source of data remains the actual accidents themselves. The most has not always been made of this diagnostic information and, as an example of the type of work that can be undertaken, an analysis of the blast damage to lamp posts at Flixborough is presented in this paper combined with information from damage to other structures. This analysis provided an insight into the sequence of events. It was concluded from the calculated impulses and estimates of peak overpressures that the overpressure-time history in the near field of an UVCE is very different from that generated by the detonation of a solid explosive. The analysis is also of value in its own right since the estimated loadings can be used as a design basis for geometrically similar structures. A programme to investigate the effect of UVCE type blast waves on simple structures has been started at Buxton, as an aid to accident investigation. The facilities available for this work are described in this paper and the work planned is briefly outlined.

  18. Nematode Locomotion in Unconfined and Confined Fluids

    CERN Document Server

    Bilbao, Alejandro; Vanapalli, Siva; Blawzdziewicz, Jerzy

    2013-01-01

    The millimeter-long soil-dwelling nematode {\\it C. elegans} propels itself by producing undulations that propagate along its body and turns by assuming highly curved shapes. According to our recent study [PLoS ONE \\textbf{7}, e40121 (2012)] all these postures can be accurately described by a piecewise-harmonic-curvature (PHC) model. We combine this curvature-based description with highly accurate hydrodynamic bead models to evaluate the normalized velocity and turning angles for a worm swimming in an unconfined fluid and in a parallel-wall cell. We find that the worm moves twice as fast and navigates more effectively under a strong confinement, due to the large transverse-to-longitudinal resistance-coefficient ratio resulting from the wall-mediated far-field hydrodynamic coupling between body segments. We also note that the optimal swimming gait is similar to the gait observed for nematodes swimming in high-viscosity fluids. Our bead models allow us to determine the effects of confinement and finite thickness...

  19. Smart cement modified with iron oxide nanoparticles to enhance the piezoresistive behavior and compressive strength for oil well applications

    Science.gov (United States)

    Vipulanandan, C.; Mohammed, A.

    2015-12-01

    In this study, smart cement with a 0.38 water-to-cement ratio was modified with iron oxide nanoparticles (NanoFe2O3) to have better sensing properties, so that the behavior can be monitored at various stages of construction and during the service life of wells. A series of experiments evaluated the piezoresistive smart cement behavior with and without NanoFe2O3 in order to identify the most reliable sensing properties that can also be relatively easily monitored. Tests were performed on the smart cement from the time of mixing to a hardened state behavior. When oil well cement (Class H) was modified with 0.1% of conductive filler, the piezoresistive behavior of the hardened smart cement was substantially improved without affecting the setting properties of the cement. During the initial setting the electrical resistivity changed with time based on the amount of NanoFe2O3 used to modify the smart oil well cement. A new quantification concept has been developed to characterize the smart cement curing based on electrical resistivity changes in the first 24 h of curing. Addition of 1% NanoFe2O3 increased the compressive strength of the smart cement by 26% and 40% after 1 day and 28 days of curing respectively. The modulus of elasticity of the smart cement increased with the addition of 1% NanoFe2O3 by 29% and 28% after 1 day and 28 days of curing respectively. A nonlinear curing model was used to predict the changes in electrical resistivity with curing time. The piezoresistivity of smart cement with NanoFe2O3 was over 750 times higher than the unmodified cement depending on the curing time and nanoparticle content. Also the nonlinear stress–strain and stress–change in resistivity relationships predicated the experimental results very well. Effects of curing time and NanoFe2O3 content on the model parameters have been quantified using a nonlinear model.

  20. Effect of activator dosage, water-to-binder-solids ratio, temperature and duration of elevated temperature curing on the compressive strength of alkali-activated fly ash cement pastes

    Scientific Electronic Library Online (English)

    J, Shekhovtsova; E P, Kearsley; M, Kovtun.

    2014-10-01

    Full Text Available In this paper the effect of sodium oxide concentration, the water-to-binder-solids ratio, temperature, and the duration of elevated temperature curing on the compressive strength of alkali-activated fly ash cement pastes was investigated. Alkali concentration varied between 3% and 15% Na2O of fly as [...] h mass. An increase in Na2O from 3% to 9% greatly improved the compressive strength of the pastes from 26.1 MPa to 50.8 MPa at 28 days. A further increase in Na2O up to 15% did not provide an increase in the strength, but a decrease was observed, as well as higher strength variation. The paste activated with 9% Na2O had the highest strength at 28 days and a low standard deviation, and 9% Na2O was thus considered as the best value in the present study. The temperature and the duration of elevated temperature curing were found to be critical factors affecting the compressive strength at early age, but their effect decreased significantly in the long term. The water-to-binder-solids ratio affected the compressive strength considerably. An increase in the water-to-binder-solids ratio of the pastes from 0.18 to 0.29 resulted in a decrease in the compressive strength from 49.3 MPa to 21.3 MPa.

  1. Uniaxial and triaxial compression tests of silicon carbide ceramics under quasi-static loading condition.

    Energy Technology Data Exchange (ETDEWEB)

    Brannon, Rebecca Moss; Lee, Moo Yul; Bronowski, David R.

    2005-02-01

    To establish mechanical properties and failure criteria of silicon carbide (SiC-N) ceramics, a series of quasi-static compression tests has been completed using a high-pressure vessel and a unique sample alignment jig. This report summarizes the test methods, set-up, relevant observations, and results from the constitutive experimental efforts. Results from the uniaxial and triaxial compression tests established the failure threshold for the SiC-N ceramics in terms of stress invariants (I{sub 1} and J{sub 2}) over the range 1246 < I{sub 1} < 2405. In this range, results are fitted to the following limit function (Fossum and Brannon, 2004) {radical}J{sub 2}(MPa) = a{sub 1} - a{sub 3}e -a{sub 2}(I{sub 1}/3) + a{sub 4} I{sub 1}/3, where a{sub 1} = 10181 MPa, a{sub 2} = 4.2 x 10{sup -4}, a{sub 3} = 11372 MPa, and a{sub 4} = 1.046. Combining these quasistatic triaxial compression strength measurements with existing data at higher pressures naturally results in different values for the least-squares fit to this function, appropriate over a broader pressure range. These triaxial compression tests are significant because they constitute the first successful measurements of SiC-N compressive strength under quasistatic conditions. Having an unconfined compressive strength of {approx}3800 MPa, SiC-N has been heretofore tested only under dynamic conditions to achieve a sufficiently large load to induce failure. Obtaining reliable quasi-static strength measurements has required design of a special alignment jig and load-spreader assembly, as well as redundant gages to ensure alignment. When considered in combination with existing dynamic strength measurements, these data significantly advance the characterization of pressure-dependence of strength, which is important for penetration simulations where failed regions are often at lower pressures than intact regions.

  2. Modelo teórico para a previsão da resistência à compressão da alvenaria armada / Theoretical model for predicting the compressive strength of reinforced masonry

    Scientific Electronic Library Online (English)

    R. F., Silva; J. S., Camacho; R. O., Rodrigues.

    2011-12-01

    Full Text Available Neste trabalho faz-se a comparação entre diferentes modelos para se prever a resistência à compressão de prismas de alvenaria de blocos de concreto. Foram estudados experimentalmente quatro tipos diferentes de configurações de prismas, sendo cada um deles ensaiados vazios, ou seja, não grauteados, e [...] preenchidos com graute mais armaduras, denominados prismas armados. Para todos os arranjos de prismas foram registradas as suas resistências à compressão axial, deformações e modos de ruptura. Posteriormente, esses resultados foram comparados com diferentes modelos teóricos de previsão de resistência, baseados nas resistências individuais de cada material, nas suas deformações de ruptura e no efeito de cintamento introduzido pelos blocos no sistema. Entre os modelos estudados, verificou-se que os que conduziram à melhores resultados foram aqueles em que foi considerado o efeito do cintamento proporcionado pelo bloco de concreto e, ainda, uma alteração na deformação de ruptura do graute. Abstract in english This paper compares different models for predicting the compressive strength of concrete block masonry prisms. Four different prism configurations were studied experimentally, each of which was tested without grout (ungrouted prisms) and with grout and reinforcement (reinforced prisms). The axial co [...] mpressive strength, strain and failure modes of all the prism configurations were recorded. These results were then compared with different theoretical models for predicting compressive strength, based on the individual strength of each material, its break strain and the strapping effect of the blocks on the system. Among the models studied here, the best results were obtained with those that consider the strapping effect of the concrete block, as well as a change in the break strain of grout.

  3. Influence of the waste glass in the axial compressive strength of Portland cement concrete; Influencia dos residuos vitreos na resistencia a compressao axial do concreto de cimento Portland

    Energy Technology Data Exchange (ETDEWEB)

    Miranda Junior, E.J.P.; Paiva, A.E.M., E-mail: edson.jansen@hotmail.com [Instituto Federal de Educacao, Ciencia e Tecnologia do Maranhao (PPGEM/IFMA), Sao Luis, MA (Brazil). Programa de Pos-Graduacao em Engenharia de Materiais

    2012-07-01

    In this work, was studied the influence of the incorporation of waste glass, coming from the stage of thinning and polishing of a company of thermal glass treatments, in the axial compressive strength of Portland cement concrete. The coarse and ground aggregates used was crushed stone and sand, respectively. For production of the concrete, percentages of glass residues of 5%, 10% and 20% had been used in substitution to the sand, and relations water/cement (a/c) 0,50, 0,55 and 0,58. The cure of the test bodies was carried through in 7, 14 and 28 days. The statistics analysis of the results was carried out through of the analysis of variance for each one of the cure times. From the results of the compressive strength of the concrete, it could be observed that the concrete has structural application for the relation a/c 0,5, independently of waste glass percentage used, and for the relation a/c 0,55 with 20% of waste glass. (author)

  4. Effect of Cement Stabilized Kaolin Subgrade on Strength Properties

    Directory of Open Access Journals (Sweden)

    Nur Akmal Abd Karim

    2014-01-01

    Full Text Available Subgrade performance generally depends on the load bearing capacity of soil. This load is often affected by degree of compaction, moisture content and soil type. Poor subgrade should be avoided by removal, replace and add stabilizer agent to provide a suitable strength for subgrade. This study presents the effect of cement stabilizer on California Bearing Ratio (CBR and Unconfined Compressive Strength (UCS for kaolin clay in low traffic volume road. The test conducted includes determination of liquid limits which leads to plasticity index for tested sample. Standard proctor test have been conducted to determine the optimum moisture content and maximum dry density of kaolin clay by using soil stabilizer with 0, 7 and 13% of Ordinary Portland cement (OPC. The CBR and UCS was conduct to determine the strength of kaolin clay at optimum moisture content and 7 days curing period to obtain minimum strength of the soil. Finding of this study shows cement stabilizer effectively increase the strength of kaolin clay. 8 % of cement was found to be the optimum percentage of cement content value to be added into kaolin soil which complies with the Malaysia Public Work Department (PWD specification.

  5. Deflagration-to-Detonation Transition in Unconfined Media

    Science.gov (United States)

    Poludnenko, Alexei; Gardiner, Thomas; Oran, Elaine

    2011-11-01

    Deflagration-to-detonation transition (DDT) can occur in environments ranging from experimental and industrial systems on Earth to astrophysical thermonuclear supernovae explosions. In recent years, substantial progress has been made in elucidating the nature of this process in confined systems with walls, obstacles, etc. It remains unclear, however, whether a subsonic turbulent flame in an unconfined environment can undergo a DDT. We present simulations of premixed flames in stoichiometric H2-air and CH4-air mixtures interacting with high-intensity turbulence. These calculations demonstrate the DDT in unconfined systems unassisted by shocks or obstacles. We discuss the mechanism of this process and its implications.

  6. Probe penetration test applied for evaluating shotcrete compressive strength / Ensaio de penetração de pino aplicado na avaliação da resistência à compressão de concreto projetado

    Scientific Electronic Library Online (English)

    W. R. L. da, Silva; L. R., Prudencio Jr; A. L. de, Oliveira.

    2012-06-01

    Full Text Available Este trabalho visa apresentar uma metodologia de avaliação da resistência à compressão de concreto projetado. Em função da elevada rugosidade superficial e da baixa espessura da camada de concreto, observada em estruturas de concreto projetado, a metodologia proposta tem por base o ensaio de penetra [...] ção de pinos. Em uma primeira etapa, a variabilidade do ensaio de penetração de pinos foi investigada de modo a definir a quantidade de ensaios necessários para a definição da curva de correlação do ensaio. Em seguida, o procedimento empregado na definição da curva de correlação foi definido. Tal procedimento inclui a moldagem de placas de concreto projetado in loco; o controle da energia de disparo dos pinos; a extração de testemunhos das placas para determinação da resistência à compressão do concreto; e a análise estatística dos dados. De posse da curva de correlação do ensaio, procede-se com a avaliação da estrutura e análise dos dados. De modo a verificar a aplicabilidade da metodologia proposta, a estrutura de concreto projetado de um túnel em uma Pequena Usina Hidrelétrica foi investigada. Na estrutra em questão, foram observados resultados de resistência não-conformes com as especificações de projeto e indícios de falta de homogeneidade do concreto. Uma vez que a metodologia em questão possibilitou a caracterização das condições da estrutura avaliada, pode-se afirmar que a solução proposta neste trabalho é adequada para a avaliação da resistência à compressão de estruturas de concreto projetado. Abstract in english This study presents a methodology for evaluating shotcrete compressive strength. Because of the high surface roughness and low thickness of the concrete layer observed in shotcrete structures, the proposed methodology is based on the probe penetration test. In a first phase, the variability of the p [...] robe penetration test was investigated to define the number of tests that are required to characterise the test correlation curve. Then, a procedure that can be applied to define the correlation curve was described. This procedure includes the moulding of shotcrete plates in loco, the control of the discharge energy of the pins, the extraction of the plates' samples to determine the concrete compressive strength, and statistical analysis. With the test correlation curve, an evaluation of the structure and data analysis can be performed. To verify the applicability of the proposed methodology, the structure of a shotcrete tunnel in a small hydropower plant was investigated. In the analysed structure, strength results that were non-compliant with the project specifications and a lack of concrete homogeneity were observed. Since the analysed methodology allowed for the characterisation of the considered structure conditions, the proposed solution is adequate for evaluating the compression strength of shotcrete structures.

  7. Conditions pertaining to the influence of electrode surface roughness upon the insulation strength of compressed SF6 systems

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson; Crichton, George C

    1997-01-01

    On the basis of a series of experimental investigations reported in the literature, electrode microscopic surface roughness was dismissed as a factor influencing breakdown levels in compressed SF6, irrespective of field non-uniformity. This conclusion appears to be tenable if one restricts observations to the investigations in question. In the present communication, we contend that the scope of these studies formed an insufficient basis on which to invoke such a general conclusion. To clarify th...

  8. Pressure and temperature dependence of shear modulus and yield strength for aluminum, copper, and tungsten under shock compression

    International Nuclear Information System (INIS)

    Experimental data for the shear modulus and yield strength of shocked aluminum, copper, and tungsten were systematically analyzed. Comparisons between these data and calculations using the Steinberg-Cochran-Guinan (SCG) constitutive model [D. J. Steinberg, S. G. Cochran, and M. W. Guinan, J. Appl. Phys. 51, 1498 (1980)] indicate that the yield strength has the same dependence on pressure and temperature as the shear modulus for aluminum for shock pressures up to 50 GPa, for copper to 100 GPa, and for tungsten to 200 GPa. Therefore, the assumption of Yp'/Y0=Gp'/G0,YT'/Y0=GT'/G0 is basically acceptable for these materials, and the SCG model can be used to describe the shear modulus and yield strength of the shocked material at high pressure and temperature

  9. Compressive strength and resistance to chloride ion penetration and carbonation of recycled aggregate concrete with varying amount of fly ash and fine recycled aggregate.

    Science.gov (United States)

    Sim, Jongsung; Park, Cheolwoo

    2011-11-01

    Construction and demolition waste has been dramatically increased in the last decade, and social and environmental concerns on the recycling have consequently been increased. Recent technology has greatly improved the recycling process for waste concrete. This study investigates the fundamental characteristics of concrete using recycled concrete aggregate (RCA) for its application to structural concrete members. The specimens used 100% coarse RCA, various replacement levels of natural aggregate with fine RCA, and several levels of fly ash addition. Compressive strength of mortar and concrete which used RCA gradually decreased as the amount of the recycled materials increased. Regardless of curing conditions and fly ash addition, the 28 days strength of the recycled aggregate concrete was greater than the design strength, 40 MPa, with a complete replacement of coarse aggregate and a replacement level of natural fine aggregate by fine RCA up to 60%. The recycled aggregate concrete achieved sufficient resistance to the chloride ion penetration. The measured carbonation depth did not indicate a clear relationship to the fine RCA replacement ratio but the recycled aggregate concrete could also attain adequate carbonation resistance. Based on the results from the experimental investigations, it is believed that the recycled aggregate concrete can be successfully applied to structural concrete members. PMID:21784626

  10. In-situ Rock Spalling Strength near Excavation Boundaries

    Science.gov (United States)

    Cai, M.; Kaiser, P. K.

    2014-03-01

    It is widely accepted that the in-situ strength of massive rocks is approximately 0.4 ± 0.1 UCS, where UCS is the uniaxial compressive strength obtained from unconfined tests using diamond drilling core samples with a diameter around 50 mm. In addition, it has been suggested that the in-situ rock spalling strength, i.e., the strength of the wall of an excavation when spalling initiates, can be set to the crack initiation stress determined from laboratory tests or field microseismic monitoring. These findings were supported by back-analysis of case histories where failure had been carefully documented, using either Kirsch's solution (with approximated circular tunnel geometry and hence ? max = 3? 1 -? 3) or simplified numerical stress modeling (with a smooth tunnel wall boundary) to approximate the maximum tangential stress ? max at the excavation boundary. The ratio of ? max /UCS is related to the observed depth of failure and failure initiation occurs when ? max is roughly equal to 0.4 ± 0.1 UCS. In this article, it is suggested that these approaches ignore one of the most important factors, the irregularity of the excavation boundary, when interpreting the in-situ rock strength. It is demonstrated that the "actual" in-situ spalling strength of massive rocks is not equal to 0.4 ± 0.1 UCS, but can be as high as 0.8 ± 0.05 UCS when surface irregularities are considered. It is demonstrated using the Mine-by tunnel notch breakout example that when the realistic "as-built" excavation boundary condition is honored, the "actual" in-situ rock strength, given by 0.8 UCS, can be applied to simulate progressive brittle rock failure process satisfactorily. The interpreted, reduced in-situ rock strength of 0.4 ± 0.1 UCS without considering geometry irregularity is therefore only an "apparent" rock strength.

  11. Effect of Superplasticizer and Extra Water on Workability and Compressive Strength of Self-Compacting Geopolymer Concrete

    OpenAIRE

    Fareed Ahmed Memon; Muhd Fadhil Nuruddin; Samuel Demie; Nasir Shafiq

    2012-01-01

    This study documents the results of an experimental work carried out to investigate the effect of superplasticizer and amount of extra water on strength and workability properties of Fly ash-based Selfcompacting geopolymer concrete. The experiments were conducted by varying the amount of extra water and dosage of superplasticizer. A total of nine mixtures with superplasticizer content varying from 3 to 7% and extra water ranging from 10 to 20% of the mass of fly ash were prepared and tested. ...

  12. Anhydrite binders in mining. Part 3. Effects of water-anhydrite index, activator and expansor on consistence, setting velocity, immediate compression strength and expansion range of binding materials

    Energy Technology Data Exchange (ETDEWEB)

    Chudek, M.; Janiczek, S.; Majchrzak, R.

    1988-09-01

    On the basis of investigations carried out by the Institute of Mine Design, Construction and Ground Surface Protection of the Silesian Technical University analyzes physical and mechanical properties of anhydrite binders used for strata control, grouting, packing, stowing and construction of ventilation barriers in underground coal mines in Poland. The following types of anhydrite binders are comparatively evaluated: anhydrite dust, anhydrite binder activated by sodium hydroxide (not exceeding 2%), anhydrite binder activated by calcium oxide (2%), anhydrite binder activated by sodium carbonate (2%), expansive anhydrite binder with sodium bicarbonate (2%), expansive binder with 4% sodium bicarbonate (expansive agent) and 2% calcium hydroxide (activating agent), expansive binder with 2.5% sodium bicarbonate (expansive agent) and 0.5% sodium hydroxide (activating agent). Effects of types and concentration ratio of activating and expanding reagents as well as water to anhydrite ratio on immediate and final compression strength and porosity of anhydrite binders are analyzed. 7 refs.

  13. Effect of solution heat treatment on the internal architecture and compressive strength of an AlMg4.7Si8 alloy?

    Science.gov (United States)

    Tolnai, D.; Requena, G.; Cloetens, P.; Lendvai, J.; Degischer, H.P.

    2013-01-01

    The evolution of the microstructure of an AlMg4.7Si8 alloy is investigated by scanning electron microscopy and ex situ synchrotron tomography in as-cast condition and subsequent solution treatments for 1 h and 25 h at 540 °C, respectively. The eutectic Mg2Si phase, which presents a highly interconnected structure in the as-cast condition, undergoes significant morphological changes during the solution heat treatment. Statistical analyses of the particle distribution, the sphericity, the mean curvatures and Gaussian curvatures describe the disintegration of the interconnected seaweed-like structure followed by the rounding of the disintegrated fractions of the eutectic branches quantitatively. The ternary eutectic Si resulting from the Si-surplus to the stoichiometric Mg2Si ratio of the alloy undergoes similar changes. The morphological evolution during solution heat treatment is correlated with results of elevated temperature compression tests at 300 °C. The elevated temperature compressive strength is more sensitive to the degree of interconnectivity of the three dimensional Mg2Si network than to the shape of the individual particles. PMID:24244073

  14. Effect of solution heat treatment on the internal architecture and compressive strength of an AlMg4.7Si8 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Tolnai, D., E-mail: domonkos.tolnai@hzg.de [Institute of Materials Science and Technology, Vienna University of Technology, Karlsplatz 13/308, A-1040 Vienna (Austria); Eötvös Loránd University, Department of Materials Physics, POB 32, H-1518 Budapest (Hungary); Requena, G. [Institute of Materials Science and Technology, Vienna University of Technology, Karlsplatz 13/308, A-1040 Vienna (Austria); Cloetens, P. [European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, F-38000 Grenoble Cédex (France); Lendvai, J. [Eötvös Loránd University, Department of Materials Physics, POB 32, H-1518 Budapest (Hungary); Degischer, H.P. [Institute of Materials Science and Technology, Vienna University of Technology, Karlsplatz 13/308, A-1040 Vienna (Austria)

    2013-11-15

    The evolution of the microstructure of an AlMg4.7Si8 alloy is investigated by scanning electron microscopy and ex situ synchrotron tomography in as-cast condition and subsequent solution treatments for 1 h and 25 h at 540 °C, respectively. The eutectic Mg{sub 2}Si phase, which presents a highly interconnected structure in the as-cast condition, undergoes significant morphological changes during the solution heat treatment. Statistical analyses of the particle distribution, the sphericity, the mean curvatures and Gaussian curvatures describe the disintegration of the interconnected seaweed-like structure followed by the rounding of the disintegrated fractions of the eutectic branches quantitatively. The ternary eutectic Si resulting from the Si-surplus to the stoichiometric Mg{sub 2}Si ratio of the alloy undergoes similar changes. The morphological evolution during solution heat treatment is correlated with results of elevated temperature compression tests at 300 °C. The elevated temperature compressive strength is more sensitive to the degree of interconnectivity of the three dimensional Mg{sub 2}Si network than to the shape of the individual particles.

  15. The compression strength investigations of AW-AlCu4Mg2Mn alloy based composites reinforced with SiC particles

    Directory of Open Access Journals (Sweden)

    A. Kurzawa

    2011-04-01

    Full Text Available In this paper strength tests of composite materials based on AW-AlCu4Mg2Mn obtained in uniaxial compression test was studied.Materials used for examination were made from AW-AlCu4Mg2Mn alloy and porous preforms of SiC particles (grain size 6÷10?m bypressure infiltration (squeeze casting. The stress-strain curves of the materials with 10% vol., 20% vol., 30% vol. particles of SiC, as well unreinforcement alloy and microstructure of scrap surface samples in a plane parallel to the compressive force were analyzed. The investigated metal matrix composites are characterized by marked reduced the plastic strain values with increasing particle strengthening while the unreinforcement materials throughout the range of deformation show considerable plasticity. In the case of the material containing 10% vol of SiC the plastic strain is a slight strengthening of the material. With increasing of the particle content the plasticity decreases. Materials with 20%vol and 30%vol of SiC particles were brittle cracked at much higher values of stress ?.

  16. Development of experimental concepts for investigating the strength behavior of fine-grained cohesive soil in the Spacelab/space shuttle zero-g environment

    Science.gov (United States)

    Bonaparte, R.; Mitchell, J. K.

    1981-01-01

    Three different sets of tests are proposed for the NASA Spacelab experimental program. The first of tests, designed to measure the true cohesion of several different soils, would be carried out in space through use of a specially prepared direct shear apparatus. As part of this first series of tests, it is recommended that a set of drained unconfined compression tests be performed terrestrially on the same soils as tested in space. A form of the direct tension test is planned to measure the true tensile strength of the same types of soils used in the first series of tests. The direct tension tests could be performed terrestrially. The combined results of the direct shear tests, direct tension tests, and unconfined compression tests can be used to construct approximate failure envelopes for the soils tested in the region of the stress origin. Relationships between true cohesion and true tensile strength can also be investigated. In addition, the role of physio-chemical variables should be studied. The third set of tests involves using a multiaxial cubical or true triaxial test apparatus to investigate the influence of gravity induced fabric anisotropy and stress nonhomogeneities on the stress strain behavior of cohesive soils at low effective stress levels. These tests would involve both in space and terrestrial laboratory testing.

  17. Effect of nepheline syenite particle size on diametrical compression strength and reliability of extruded ceramic Raschig rings used in packed towers

    Energy Technology Data Exchange (ETDEWEB)

    Salem, A.; Rostami, N.

    2013-05-01

    In order to understand the effect of nepheline syenite particle size on physico-chemical properties of ceramic Raschig rings, the fluxing agent was grinded at different milling times. The compositions were prepared by blending the illitic-kaolinitic clay and pre-grinded particles. The rings were shaped by a laboratory extruder and then were sintered at 1200 degree centigrade. The mechanical reliability of sintered specimens was mathematically described by Weibull theory and the effect of pre-grinding of fluxing agent on Weibull modulus was evaluated by measuring the diametrical compression strength. Weibull modulus and strength were the criteria for selecting the suitable particle size range of nepheline syenite. It was found that the pre-grinding of nepheline syenite acts as fairly strong parameter on microstructure of rings. The investigation concludes that reliable rings can be fabricated if the particle size of nepheline syenite is arranged between 53 and 75 {mu}m. This enhancement in reliability is valuable in packed towers. (Author) 17 refs.

  18. Effect of nepheline syenite particle size on diametrical compression strength and reliability of extruded ceramic Raschig rings used in packed towers

    Energy Technology Data Exchange (ETDEWEB)

    Salem, A.; Rostami, N.

    2013-06-01

    In order to understand the effect of nepheline syenite particle size on physico-chemical properties of ceramic Raschig rings, the fluxing agent was grinded at different milling times. The compositions were prepared by blending the illitic-kaolinitic clay and pre-grinded particles. The rings were shaped by a laboratory extruder and then were sintered at 1200 degree centigrade. The mechanical reliability of sintered specimens was mathematically described by Weibull theory and the effect of pre-grinding of fluxing agent on Weibull modulus was evaluated by measuring the diametrical compression strength. Weibull modulus and strength were the criteria for selecting the suitable particle size range of nepheline syenite. It was found that the pre-grinding of nepheline syenite acts as fairly strong parameter on microstructure of rings. The investigation concludes that reliable rings can be fabricated if the particle size of nepheline syenite is arranged between 53 and 75 {mu}m. This enhancement in reliability is valuable in packed towers. (Author)

  19. Effect of Microwave Treatment on Oak Compression Strength / Effet du Traitement du Bois de Chêne par des Ultrasons sur la Résistance à la Compression / Efeito na Resistência à Compressão do Tratamento de Madeira de Carvalho com Ultra-Sons

    Scientific Electronic Library Online (English)

    José Saporiti, Machado.

    2006-06-01

    Full Text Available A energia de microondas (electromagnética) é actualmente utilizada no tratamento de degradação biológica e na classificação mecânica de madeira e perspectiva-se a sua utilização na secagem de madeira. A exposição a microondas de elementos estruturais de madeira implica, tal como para outros processo [...] s de preparação da madeira (preservação ou tratamentos ignífugos), analisar o efeito dessa exposição nas propriedades mecânicas da madeira. O presente artigo pretende contribuir para esta discussão, apresentando um estudo preliminar sobre o efeito da exposição a microondas (durante 5 e 10min) na resistência à compressão paralela às fibras de madeira de Carvalho limpa de defeitos. Os resultados obtidos mostram uma clara perda de resistência com a exposição e aumento do tempo de exposição. Considerando os resultados obtidos no presente estudo e por outros autores, torna-se clara a necessidade de estudos mais exaustivos tendo em vista estabelecer possíveis factores de correcção ou regras de utilização segura desta energia de forma a garantir um apropriado comportamento mecânico da madeira. Abstract in english Microwave (electromagnetic) energy is currently used in the treatment of biological damage, in the machine grading of timber and its use for timber drying is foreseen. The exposure of structural timber elements to microwaves, such as for other timber treatments (preservation or fire-retardant), impl [...] ies analyzing its effect on the mechanical properties of the wood. This paper intends to contribute to this discussion, presenting a preliminary study on the effect of microwave exposure (during 5 and 10min) on compression parallel to grain strength of clear Oak wood. The results obtained show a clear loss of strength due to exposure and to an increase in the time of exposure. Considering the results obtained in this study and by other authors, it becomes clear that more thorough research is needed, bearing in mind the establishment of strength correction factors or rules towards the safe use of this technology for assuring the proper mechanical behaviour of timber.

  20. TNT Equivalency of Unconfined Aerosols of Propylene Oxide

    Directory of Open Access Journals (Sweden)

    A. Apparao

    2014-09-01

    Full Text Available The unconfined aerosols of propylene oxide (PO are formed by dispersing the fuel in air. These aerosols undergo detonation by suitable initiation and produce high impulse blast. Tri-nitro Toluene (TNT equivalence is an important parameter used to represent the power of explosive materials and compare their relative damage effects wrt TNT. The parameters commonly used for estimation of TNT equivalency are total energy of explosive source and properties of resulting blast wave, viz., blast peak overpressure and positive impulse. In the present study, the unconfined aerosols of 4.2 kg PO were formed by breaking open the cylindrical canister with the help of axially positioned central burster charge and then detonated using a secondary explosive charge after a preset time delay. The resulting blast profiles were recorded and the blast parameters were analysed. Being a non-ideal explosive source, the TNT equivalency depends on fraction of total energy utilised for blast formation, the rate of energy release, cloud dimensions, and concentration of fuel. Hence, various approaches based on energy release, experimental blast profiles, triangulated blast parameters, and ground reflected blast parameters were considered to determine the TNT equivalency of unconfined PO aerosols. It was observed that the TNT equivalency is not a single value but vary with distance. The paper provides various options for weapon designer to choose a suitable approach for considering TNT equivalency. The scaling laws established from the experimental data of unconfined aerosols of PO for blast peak over pressure and scaled impulse help in predicting the performance for different values of fuel weight and distance.Defence Science Journal, Vol. 64, No. 5, September 2014, pp.431-437, DOI:http://dx.doi.org/10.14429/dsj.64.6851

  1. Resistência à compressão de argamassas em função da adição de fibra de coco / Compressive strength of cement mortar prepared with the addition of coconut fiber

    Scientific Electronic Library Online (English)

    Everton J. da, Silva; Paola D. da, Silva; Maria L., Marques; Celso C. M., Fornari Junior; Fermin C., Garcia; Francisco H. M., Luzardo.

    2014-12-01

    Full Text Available Neste trabalho se propôs analisar a influência que a variação do comprimento da fibra de coco exerce na resistência à compressão da argamassa, em busca de se determinar, experimentalmente, o comprimento mais próximo ao tamanho crítico. Foram confeccionadas argamassas com adição (0,3% em relação ao v [...] olume total da mistura) de 6 comprimentos diferentes de fibras de coco: 12,5; 25,0; 37,5; 50,0; 62,5 e 75,0 mm, além de uma argamassa de referência sem adição de fibra de coco. Para a avaliação do comportamento de cada um deles na argamassa foram efetuados ensaios de consistência no estado fresco e resistência à compressão axial no estado endurecido, realizado nas idades 7, 28 e 56 dias, ao longo do primeiro semestre de 2013. Foi observado que todos os comprimentos de fibra testados diminuem a resistência à compressão em relação à argamassa de referência, nas três idades. No entanto, dentre esses comprimentos testados, pode-se afirmar que a argamassa com adição de fibras de comprimento 25,0 mm obteve melhor desempenho nas três idades testadas. Abstract in english This paper aims to analyse the influence that the length of coconut fiber exerts on compressive strength of mortar seeking to determine their critical length. Mortars were prepared with addition (0.3% volume of the mixture) of 6 different lengths of coconut fibers: 12.5, 25.0, 37.5, 50.0, 62.5 and 7 [...] 5.0 mm, and a reference mortar. To study the behavior of each one in mortar, consistency tests were performed on fresh and hard state in axial compression strength test at three ages (7, 28 and 56 days) during the first half of 2013. It was observed that all lengths tested decrease resistance compared to the reference mortar in three ages, however, the mortar with addition of 25.0 mm length fibers had a better performance in the study.

  2. Compressive Strength Estimation of Marble Specimens using Acoustic Emission Hits in Time and Natural Time Domains: Preliminary Results

    Science.gov (United States)

    Hloupis, George; Stavrakas, Ilias; Vallianatos, Filippos; Triantis, Dimos

    2013-04-01

    The current study deals with preliminary results of characteristic patterns derived from acoustic emissions during compressional stress. Two loading cycles were applied to a specimen of 4cm x 4cm x 10 cm Dionysos marble while acoustic emissions (AE) were recorded using one acoustic sensor coupled at the expected direction of the main crack (at the center of the specimen). The produced time series comprised from the number of counts per AE hit under increasing and constant load. Processing took place in two domains: in conventional time domain (t), using multiresolution wavelet analysis for the study of temporal variation of the wavelet-coefficients' standard deviation (SDEV) [1] and in natural time domain (?), using the variance (?1) of natural-time transformed time-series [2,3]. Results in both cases, dictate that identification of the region where the increasing stress (?), exceeds 40% of the ultimate compressional strength (?*), is possible. More specific, in conventional time domain, the temporal evolution of SDEV presents a sharp change around ?* during first loading cycle and less than ?* during second loading cycle. In natural time domain, the ?1 value clearly oscillate around 0.07 at natural time indexes corresponding to ?* during first loading cycle. Merging both results leads to a preliminary observation that we have an identification of the time when the compressional stress exceeds ?*. References [1] Telesca, L., Hloupis, G., Nikolintaga, I., Vallianatos, F.,."Temporal patterns in southern Aegean seismicity revealed by the multiresolution wavelet analysis", Communications in Nonlinear Science and Numerical Simulation, vol. 12, issue 8, pp 1418-1426, 2007 [2] P. A. Varotsos, N. V. Sarlis, and E. S. Skordas, "Natural Time Analysis: The New View of Time. Precursory Seismic Electric Signals, Earthquakes and other Complex Time-Series", Springer-Verlag, Berlin, Heidelberg, 2011. [3] N. V. Sarlis, P. A. Varotsos, and E. S. Skordas, "Flux Avalances in YBa2Cu307-x films and rice piles: natural time domain analysis", Physical Review B, 73, 054504, 2006. Acknowledgements This work was supported by the THALES Program of the Ministry of Education of Greece and the European Union in the framework of the project entitled "Integrated understanding of Seismicity, using innovative Methodologies of Fracture mechanics along with Earthquake and non extensive statistical physics - Application to the geodynamic system of the Hellenic Arc. SEISMO FEAR HELLARC".

  3. Concrete-Filled-Large Deformable FRP Tubular Columns under Axial Compressive Loading

    Directory of Open Access Journals (Sweden)

    Omar I. Abdelkarim

    2015-10-01

    Full Text Available The behavior of concrete-filled fiber tubes (CFFT polymers under axial compressive loading was investigated. Unlike the traditional fiber reinforced polymers (FRP such as carbon, glass, aramid, etc., the FRP tubes in this study were designed using large rupture strains FRP which are made of recycled materials such as plastic bottles; hence, large rupture strain (LRS FRP composites are environmentally friendly and can be used in the context of green construction. This study performed finite element (FE analysis using LS-DYNA software to conduct an extensive parametric study on CFFT. The effects of the FRP confinement ratio, the unconfined concrete compressive strength ( , column size, and column aspect ratio on the behavior of the CFFT under axial compressive loading were investigated during this study. A comparison between the behavior of the CFFTs with LRS-FRP and those with traditional FRP (carbon and glass with a high range of confinement ratios was conducted as well. A new hybrid FRP system combined with traditional and LRS-FRP is proposed. Generally, the CFFTs with LRS-FRP showed remarkable behavior under axial loading in strength and ultimate strain. Equations to estimate the concrete dilation parameter and dilation angle of the CFFTs with LRS-FRP tubes and hybrid FRP tubes are suggested.

  4. Constructing a geomechanical model of the Woodford Shale, Cherokee Platform, Oklahoma, USA effects of confining stress and rock strength on fluid flow

    Science.gov (United States)

    Hair, Tyler J.

    A micro-indentation tool is used to estimate the strength of the Woodford Shale from whole core samples through the geometrical attributes (diameter and depth) of a 'dimple' produced by the tool on the rock's surface. The measured dimples are correlated graphically with the unconfined compressive strength and internal friction angle of the Woodford and integrated with contemporary stress data from earthquake focal mechanisms and mapped active faults. Right-lateral strike-slip motion on a deep, unnamed potential splay of the Wilzetta fault (Cherokee Platform, Lincoln County, Oklahoma) is representative of the contemporary stress state of the region. Vertical or near-vertical factures striking ˜ 030° from SHaz (˜ 077°) are the mechanical discontinuities most likely to be reactivated and allow fluids to flow along their surfaces. This reactivation will occur if the magnitude of pressure sources such as pore pressure or fluid pressure exceeds the reactivation pressure for that fracture surface.

  5. Efeito de altas temperaturas na resistência à compressão, resistência à tração e módulo de deformação do concreto / The effect of high temperatures on concrete compression strength, tensile strength and deformation modulus

    Scientific Electronic Library Online (English)

    A. A. A. de, Souza; A. L., Moreno JR.

    2010-12-01

    Full Text Available Este trabalho teve como objetivo a investigação experimental do comportamento do concreto quando submetido a elevadas temperaturas. Um concreto de utilização comum em nossa região, com cimento e agregados usuais, misturados em proporções também usuais (traço), foi submeti- do a temperaturas de 300 ° [...] C, 600°C e 900 °C , de maneira a se avaliar prováveis alterações na resistência à compressão, na resistência à tração e no módulo de deformação deste concreto. O efeito do resfriamento rápido do concreto, usual em intervenções de combate a incêndios, foi avaliado; alguns dos corpos-de-prova submetidos às altas temperaturas estipuladas foram resfriados rapidamente e outros foram resfriados len- tamente (ao ambiente). A recuperação provável das propriedades mecânicas analisadas, com a reidratação do concreto - com possível redução após o efeito das altas temperaturas aplicadas - também foi avaliada; corpos-de-prova submetidos às altas temperaturas estipuladas e resfriados lentamente, foram parte imersos em água e parte envoltos em filme plástico e a seguir, cada parte correspondente foi avaliada, em relação às propriedades do concreto pesquisadas, para as idades do concreto de 28, 56, 112 e 224 dias após o resfriamento lento. Ao final deste trabalho, importantes resultados sobre o efeito de altas temperaturas nas propriedades mecânicas do concreto puderam ser obtidos; contribuindo, em muito, para o estabelecimento de parâmetros para o projeto de recuperação de estruturas submetidas ao efeito do fogo. Abstract in english This paper has as a goal to present the results of experimental investigations on the behavior of concrete when submitted to high temperatures. A concrete of common utilization in our region, with cement and usual aggregates mixed in usual proportions (mix), was submitted to tempera- tures of 300ºC, [...] 600ºC and 900ºC, in order to assess probable variations in its compression strength, tensile strength and deformation module. The effect of rapidly cooling concrete, usual in fire fighting, was assessed; a few test bodies submitted to high temperatures were rapidly cooled and others were slowly cooled (to room temperature). The probable recovery of the mechanical properties under investigation following concrete rehydration - after a possible reduction from the effects of the high temperatures applied - was also assessed; test bodies were submitted to high temperatures and cooled slowly; a few were immersed in water and others were wrapped up in plastic film and then evaluated in relation to the researched properties for concrete ages of 28, 56, 112 and 224 days after slow cooling. Upon finishing this work, important results on the effect of high temperatures on concrete mechanical properties were obtained, thus providing a major contribution for the recovery design of structures that had been subject to fire.

  6. Tissue-Engineered Articular Cartilage Exhibits Tension-Compression Nonlinearity Reminiscent of the Native Cartilage

    OpenAIRE

    Kelly, Terri-Ann N.; Roach, Brendan L.; Weidner, Zachary D.; Mackenzie-Smith, Charles R.; O'Connell, Grace D.; Lima, Eric G.; Stoker, Aaron M; Cook, James. L.; ATESHIAN, GERARD A.; Hung, Clark T.

    2013-01-01

    The tensile modulus of articular cartilage is much larger than its compressive modulus. This tension-compression nonlinearity enhances interstitial fluid pressurization and decreases the frictional coefficient. The current set of studies examines the tensile and compressive properties of cylindrical chondrocyte-seeded agarose constructs over different developmental stages through a novel method that combines osmotic loading, video microscopy, and uniaxial unconfined compression testing. This ...

  7. The influence of specimen capping on the results of compression strength tests of cementitious composites / Influência do capeamento nos resultados do ensaio de resistência à compressão em compósitos cimentícios

    Scientific Electronic Library Online (English)

    Augusto Cesar da Silva, Bezerra; Maria Teresa Paulino, Aguilar; Paulo Roberto, Cetlin.

    2012-09-01

    Full Text Available Os compósitos cimentícios, comumente, são avaliados em função de sua trabalhabilidade, do teor de ar incorporado, do seu módulo de elasticidade e de resistência à compressão. Essa resistência é determinada através de ensaios de compressão axial de corpos-de-prova moldados especialmente para essa fin [...] alidade. Na execução do ensaio de compressão, é necessário que as superfícies, onde se aplicam as cargas, sejam planas, paralelas e lisas, de modo que o carregamento seja uniformemente distribuído. Para isso são utilizadas diversas técnicas e materiais, como capeamentos aderentes, não aderentes, sistemas de desgaste mecânico ou moldes especiais. Atualmente, os capeamentos mais utilizados são os que utilizam argamassas de enxofre ou almofadas de neoprene. O presente trabalho avalia, experimentalmente, a interferência de diferentes tipos de regularização das bases dos corpos-de-prova para compósitos cimentícios de diferentes classes de resistência. Abstract in english Cementitious composites are commonly evaluated considering their workability, level of incorporated air, elasticity modulus and compression strength. Data from compression testing commonly present a high dispersion, which has been attributed to effects of the specimen geometry, dimensions and of the [...] degree of material compaction, as well as to problems in the specimen end-faces, such as their parallelism, orthogonality in relation to the compression axis and surface regularity. Specimen end-face regularization has been achieved through various techniques, such as adhering or non-adhering capping with various materials, mechanical grinding and systems involving special moulds. The regularization methods utilized more frequently employ sulfur mortar capping, neoprene cushions and surface grinding. The present work covers the experimental compression tests of cementitious composites of different classes of strength employing sulfur mortar capping and neoprene cushions. It was concluded that there is a strong influence of the chosen regularization technique on the measured compression strengths.

  8. Modo de ruptura, deformabilidade e resistência de pequenas paredes estruturais / Failure mode, deformability and compressive strength of small structural masonry walls

    Scientific Electronic Library Online (English)

    Gihad, Mohamad; Eduardo, Rizzatti; Humberto Ramos, Roman.

    2011-09-01

    Full Text Available O sistema construtivo em alvenaria estrutural é largamente utilizado no Brasil e um dos principais desafios existents é como aumentar o desempenho mecânico das paredes estruturais. Para isso, é necessário conhecer as propriedades mecânicas responsáveis pela ruptura do conjunto (bloco/argamassa). Nes [...] te trabalho pretende-se avaliar a resistência a tração direta dos blocos de concreto e verificar a deformabilidade e modo de ruptura de pequenas paredes estruturais, a fim de compreender os fenômenos envolvidos na ruptura do conjunto e, por consequência, aumentar o desempenho à compressão. Como conclusão do trabalho, observou-se que o surgimento das não-linearidades da alvenaria correspondeu ao aumento das deformações laterais, devido à extensiva fissuração do material e a um aumento progressivo do coeficiente de Poisson da parede. O início das trincas verticais deu-se na interface bloco/argamassa da junta vertical, sendo este o ponto frágil do conjunto bloco/argamassa. Isso aconteceu quando a tensão atingiu, aproximadamente, 60% da tensão última de ruptura. Abstract in english The masonry construction system is widely used in Brazil and one of the existing challenges is how to improve the performance of structural walls. Therefore, it is necessary understand the mechanical properties of the set (block/mortar) responsible for the failure. The main goal of this study is to [...] assess the tensile strength of concrete blocks and verify the failure mode and deformability of small structural walls in order to understand the phenomena involved in the rupture of the set and, consequently, improve performance under compression. The experimental results indicated that the appearance of nonlinearity in the masonry corresponded to an increase in lateral deformation due to extensive cracking of the material and a progressive increase in the wall Poisson's ratio. The beginning of vertical cracks occurred in the block-vertical interface of the mortar joint. This happened when the stress reached approximately 60% of ultimate stress.

  9. Neutralization of acid mine drainage using fly ash, and strength development of the resulting solid residues

    Scientific Electronic Library Online (English)

    V.R. Kumar, Vadapalli; M.J., Klink; O., Etchebers; L.F., Petrik; W., Gitari; R.A., White; D., Key; E., Iwuoha.

    2008-08-01

    Full Text Available Acid mine drainage (AMD) from a South African coal mine was neutralized with fly ash (FA) from a local power station. An immediate increase in pH and subsequent decrease in the electrical conductivity (EC) values were observed with the addition of FA. A pH buffering region was observed for all the A [...] MD:FA ratios investigated. This was attributed to precipitation and hydrolysis of the main AMD constituents such as Al and Fe and adsorption of the precipitates upon the ash particles. A high percentage of major, minor and trace elements and SO4(2-) attenuation was achieved after contact of AMD with FA in solution; this removal depended on the final pH of the product water. Most of the contaminants were removed to acceptable levels in one simple procedure by contacting the AMD with FA in suitable ratios. Solid residues (SR) recovered from neutralization reactions were tested for unconfined compressive strength and elastic modulus in order to assess their suitability as backfill material. Strength testing was carried out for 410 days with and without the addition of ordinary Portland cement. The SR with a pozzolanic binder added gained 300% greater strength than without, both of which increased in strength over time. The implementation of this FA treatment process would not only be environmentally beneficial but also would be to the advantage of coal mines and power stations as a way of constructively using the large volumes of waste that they generate.

  10. EXPLORACIÓN CON REDES NEURONALES ARTIFICIALES PARA ESTIMAR LA RESISTENCIA A LA COMPRESIÓN, EN CONCRETOS FIBROREFORZADOS CON ACERO / EXPLORING ARTIFICIAL NEURAL NETWORKS TO ESTIMATE COMPRESSIVE STRENGTH OF STEEL FIBER-REINFORCED CONCRETE

    Scientific Electronic Library Online (English)

    Luis Octavio, González Salcedo; Aydée Patricia, Guerrero Zúñiga; Silvio, Delvasto Arjona; Adrián Luis, Ernesto Will.

    2012-01-01

    Full Text Available RESUMEN En diseño y construcción de estructuras de concreto, la resistencia a la compresión a 28 días de curado es la especificación de control de estabilidad de la obra. La inclusión de fibras como reforzamiento de la matriz cementicia permite una ganancia en sus propiedades, además de obtener un m [...] aterial de alto desempeño. En las normativas, se plantean formulaciones predictivas de la resistencia a la compresión basadas en unos pocos parámetros de composición del concreto, tales como la relación agua/cemento y el contenido de cemento Portland. Por otra parte, también se han planteado métodos de diseños de concreto para definir la ponderación de sus materiales componentes, teniendo como referencia la resistencia a la compresión del concreto simple. Además, las redes neuronales artificiales, como un símil de las neuronas biológicas, han sido utilizadas como herramientas de predicción de la resistencia a la compresión en el concreto, también con referencia al concreto simple, sin reforzamiento con fibras. Los antecedentes en este uso muestran que es interesante desarrollar aplicaciones en los concretos reforzados con fibras. En el presente trabajo se elaboraron redes neuronales artificiales para predecir la resistencia a la compresión en concretos reforzados con fibras de acero. Los resultados de los indicadores de desempeño mostraron que las redes neuronales artificiales elaboradas pueden realizar una aproximación adecuada al valor real de la propiedad mecánica. Abstract in english ABSTRACT By designing and building concrete structures, the compressive strength achieved at 28-day curing typically represents the stability control specification of any work. Furthermore, reinforcing fibers into the cement based matrix has allowed a gain to their properties, as well as a high perf [...] ormance material. Technical literature states predictive formulations of compressive strength of concrete in function of a few composition parameters, such as water/cement ratio and the Portland cement. Also, there are formulations to find the proportion of the raw materials to get a defined compressive strength, specifically non-reinforced ordinary concrete. Besides artificial neural networks as a metaphor of biological neurons have been used as a tool to predict concrete compressive strength. The experience in this application shows an increasing interest to develop applications using fiber-reinforced concrete. In this paper, an artificial neural network has been developed to predict the compressive strength of steel-fiber-reinforced-concrete. The results prove that developed artificial neural networks may perform an adequate approximation to the actual value of the mechanical property.

  11. Physical model simulations of seawater intrusion in unconfined aquifer

    Directory of Open Access Journals (Sweden)

    Tanapol Sriapai

    2012-12-01

    Full Text Available The objective of this study is to simulate the seawater intrusion into unconfined aquifer near shoreline and to assessthe effectiveness of its controlling methods by using scaled-down physical models. The intrusion controlled methods studiedhere include fresh water injection, saltwater extraction, and subsurface barrier. The results indicate that under natural dynamicequilibrium between the recharge of fresh water and the intrusion well agree with the Ghyben-Herzberg mathematical solution.Fresh water pumping from the aquifer notably move the fresh-salt water interface toward the pumping well, depending on thepumping rates and the head differences (?h between the aquifer recharge and the salt water level. The fresh water injectionmethod is more favorable than the salt water extraction and subsurface barrier method. The fresh water injection rate of about10% of the usage rate can effectively push the interface toward the shoreline, and keeping the pumping well free of salinity.

  12. Truly unconfined deflagrations of ethylene-air mixtures

    International Nuclear Information System (INIS)

    To estimate the possible over-pressure on the structures of a nuclear power plant under an external explosion, studies on unconfined explosions to provide the necessary elements to establish a safety rule, have been developed. The present research contract, carried out by a French group CEA-EDF-ENSMA, was divided in four stages: 1) Scale effect on the pressure field produced by spontaneous accelerations on blasts in an steady medium; 2) effect of a brutal discontinuity of the fuel gas concentration on the blast speed in a stratified medium; 3) effect of the blast-off energy on the explosion of a spherical ethylene-air mixture; 4) study of the influence of the shape and of the size of the cloud on the pressure field produced by the explosion

  13. Compressive and diametral tensile strength of glass ionomer cements / Resistência à compressão e à tração diametral de cimentos de ionômero de vidro

    Scientific Electronic Library Online (English)

    Eduardo, Bresciani; Terezinha de Jesus Esteves, Barata; Ticiane Cestari, Fagundes; Akimi, Adachi; Marina Martins, Terrin; Maria Fidela de Lima, Navarro.

    2004-12-01

    Full Text Available Comparou-se a Resistência à Compressão (RC) e à Tração Diametral (TD) de um cimento de ionômero de vidro de alta viscosidade [Fuji IX (GC Corporation)] e de dois novos cimentos Brasileiros [Vitro Molar (DFL) e Bioglass R (Biodinamica)], recentemente lançados no mercado, ambos indicados para o Tratam [...] ento Restaurador Atraumático (ART), em diferentes períodos de tempo. Foram confeccionados quinze corpos-de-prova com 6,0 mm de diâmetro x 3,0 mm de altura para o teste de TD e quinze com 6,0 mm de diâmetro e 12,0 mm de altura para o teste de RC, para cada ionômero a ser testado. Os corpos-de-prova foram armazenados em recipientes plásticos, com água deionizada, e mantidos em estufa a 37ºC e 100% de umidade, até a realização dos testes. Cinco corpos-de-prova de cada material foram submetidos aos testes de TD e RC em cada período de tempo: 1-hora, 24-horas e 7-dias, em uma máquina de testes universal (EMIC - DL 500) a uma velocidade de 1,0 mm/min para RC e 0,5mm/min para TD. Os dados obtidos foram submetidos aos testes ANOVA a dois critérios e Tukey (á=0,05). Os valores médios de RC e TD variaram de 42,03 a 155.47 MPa e de 5,54 a 13,72 MPa, respectivamente para os períodos analisados. O Fuji IX e o Vitro Molar não apresentaram diferenças em relação aos testes de RC e TD, exceto para RC no período de 1-hora. O Bioglass R apresentou os menores valores de RC dos cimentos testados. Na TD o Bioglass R não apresentou diferença em relação aos outros cimentos testados no período de 1-hora e não foi diferente do Vitro-Molar nos períodos de 24-horas e 7-dias. Mais estudos são necessários para avaliar outras propriedades mecânicas desses novos cimentos de ionômero de vidro brasileiros, tais como: tenacidade e desgaste, bem como composição química e biocompatibilidade. Abstract in english The aim of this study was to compare, in different periods of time, the compressive and diametral tensile strength of a traditional high viscous glass ionomer cement: Fuji IX (GC Corporation), with two new Brazilian GIC's: Vitro-Molar (DFL) and Bioglass R (Biodinamica), all indicated for the Atrauma [...] tic Restorative Treatment (ART) technique. Fifteen disk specimens (6.0mm diameter x 3.0mm height) for the diametral tensile strength (DTS) test and fifteen cylindrical specimens (6.0mm diameter x 12.0mm height) for the compressive strength (CS) test were made of each GIC. Specimens were stored in deionized water at 37º C and 100% of humidity in a stove until testing. Five specimens of each GIC were submitted to CS and DTS test in each period, namely 1 hour, 24 hours and 7 days. The specimens were tested in a testing machine (Emic) at a crosshead speed of 1.0mm/min for CS and 0.5mm/min for the DTS test until failure occurred. The data were submitted to two-way ANOVA and Tukey tests (alpha=0.05). The mean CS values ranged from 42.03 to 155.47MPa and means DTS from 5.54 to 13.72 MPa, with test periods from 1h to 7 days. The CS and DTS tests showed no statistically significant difference between Fuji IX and Vitro Molar, except for CS test at 1-hour period. Bioglass R had lowest mean value for CS of the cements tested. In DTS test Bioglass R presented no statistically significant differences when compared with all others tested GICs at 1-hour period and Bioglass R presented no difference at 24-hour and 7-day periods when compared to Vitro-Molar. Further studies to investigate other physical properties such as fracture toughness and wear resistance, as well as chemical composition and biocompatibility, are now needed to better understand the properties of these new Brazilian GIC's.

  14. Compressive and diametral tensile strength of glass ionomer cements Resistência à compressão e à tração diametral de cimentos de ionômero de vidro

    Directory of Open Access Journals (Sweden)

    Eduardo Bresciani

    2004-12-01

    Full Text Available The aim of this study was to compare, in different periods of time, the compressive and diametral tensile strength of a traditional high viscous glass ionomer cement: Fuji IX (GC Corporation, with two new Brazilian GIC's: Vitro-Molar (DFL and Bioglass R (Biodinamica, all indicated for the Atraumatic Restorative Treatment (ART technique. Fifteen disk specimens (6.0mm diameter x 3.0mm height for the diametral tensile strength (DTS test and fifteen cylindrical specimens (6.0mm diameter x 12.0mm height for the compressive strength (CS test were made of each GIC. Specimens were stored in deionized water at 37º C and 100% of humidity in a stove until testing. Five specimens of each GIC were submitted to CS and DTS test in each period, namely 1 hour, 24 hours and 7 days. The specimens were tested in a testing machine (Emic at a crosshead speed of 1.0mm/min for CS and 0.5mm/min for the DTS test until failure occurred. The data were submitted to two-way ANOVA and Tukey tests (alpha=0.05. The mean CS values ranged from 42.03 to 155.47MPa and means DTS from 5.54 to 13.72 MPa, with test periods from 1h to 7 days. The CS and DTS tests showed no statistically significant difference between Fuji IX and Vitro Molar, except for CS test at 1-hour period. Bioglass R had lowest mean value for CS of the cements tested. In DTS test Bioglass R presented no statistically significant differences when compared with all others tested GICs at 1-hour period and Bioglass R presented no difference at 24-hour and 7-day periods when compared to Vitro-Molar. Further studies to investigate other physical properties such as fracture toughness and wear resistance, as well as chemical composition and biocompatibility, are now needed to better understand the properties of these new Brazilian GIC's.Comparou-se a Resistência à Compressão (RC e à Tração Diametral (TD de um cimento de ionômero de vidro de alta viscosidade [Fuji IX (GC Corporation] e de dois novos cimentos Brasileiros [Vitro Molar (DFL e Bioglass R (Biodinamica], recentemente lançados no mercado, ambos indicados para o Tratamento Restaurador Atraumático (ART, em diferentes períodos de tempo. Foram confeccionados quinze corpos-de-prova com 6,0 mm de diâmetro x 3,0 mm de altura para o teste de TD e quinze com 6,0 mm de diâmetro e 12,0 mm de altura para o teste de RC, para cada ionômero a ser testado. Os corpos-de-prova foram armazenados em recipientes plásticos, com água deionizada, e mantidos em estufa a 37ºC e 100% de umidade, até a realização dos testes. Cinco corpos-de-prova de cada material foram submetidos aos testes de TD e RC em cada período de tempo: 1-hora, 24-horas e 7-dias, em uma máquina de testes universal (EMIC - DL 500 a uma velocidade de 1,0 mm/min para RC e 0,5mm/min para TD. Os dados obtidos foram submetidos aos testes ANOVA a dois critérios e Tukey (á=0,05. Os valores médios de RC e TD variaram de 42,03 a 155.47 MPa e de 5,54 a 13,72 MPa, respectivamente para os períodos analisados. O Fuji IX e o Vitro Molar não apresentaram diferenças em relação aos testes de RC e TD, exceto para RC no período de 1-hora. O Bioglass R apresentou os menores valores de RC dos cimentos testados. Na TD o Bioglass R não apresentou diferença em relação aos outros cimentos testados no período de 1-hora e não foi diferente do Vitro-Molar nos períodos de 24-horas e 7-dias. Mais estudos são necessários para avaliar outras propriedades mecânicas desses novos cimentos de ionômero de vidro brasileiros, tais como: tenacidade e desgaste, bem como composição química e biocompatibilidade.

  15. CORRELATION DEVELOPMENT BETWEEN INDENTATION PARAMETERS AND UNAXIAL COMPRESSIVE STRENGTH FOR COLOMBIAN SANDSTONES Desarrollo de Correlaciones entre parámetros de indentación y resistencia comprensiva uniaxial para areniscas colombianas

    Directory of Open Access Journals (Sweden)

    Jefferson Mateus

    2007-12-01

    Full Text Available Anew way to characterize the perforated formation strength has been implemented using the Indentation test. This test can be performed on irregular cuttings mounted in acrylic resins forming a disc. The test consists of applying load on each sample by means of a flat end indenter. A graph of the load applied VS penetration of the indenter is developed, and the modules of the test, denominated Indentation Modulus (IM and Critical Transition Force (CTF are obtained (Ringstad et al., 1998. Based on the success of previous studies we developed correlations between indentation and mechanical properties for some Colombian sandstones. These correlations were obtained using a set of 248 indentation tests and separate compression tests on parallel sandstone samples from the same depth. This analysis includes Barco Formation, Mirador Formation, and Tambor Formation. For the correlations, IM-UCS and CTF-UCS, the correlation coefficient are 0,81 and 0,70 respectively. The use of the correlation and the Indentation test is helpful for in-situ calibration of the geomechanical models since the indentation test can be performed in real time thus reducing costs and time associated with delayed conventional characterization.Una nueva manera de caracterizar la resistencia de las formaciones perforadas ha sido implementada por medio de una prueba denominada Indentación. Esta prueba es desarrollada sobre cortes irregulares de roca encapsulados en resina acrílica formando un disco. La prueba consiste en la aplicación de carga sobre cada partícula de roca por medio de un indentador de punta plana. En la prueba, una gráfica de la carga en función del desplazamiento del indentador en la muestra es registrada, en dicha gráfica se calculan los parámetros de indentación denominados Modulo de Indentación (IM y Fuerza Crítica de Transición (CTF (Ringstad et al., 1998. Con base en estudios previos se desarrollaron correlaciones propias entre los parámetros de Indentación y el UCS (Resistencia Compresiva Uniaxial para algunas formaciones de areniscas Colombianas. Dichas correlaciones se obtuvieron llevando a cabo 248 pruebas de Indentación y paralelamente 21 pruebas de Compresión Uniaxial sobre muestras provenientes de cilindros de roca de geometría convencional. Este estudio incluyó muestras de las formaciones: Mirador, Barco y Tambor. Para las correlaciones hspace="0" vspace="0">IM-UCS y CTF-UCS se determinaron coeficientes de correlación de 0,81 y 0,70 respectivamente. El uso de las correlaciones y las pruebas de Indentación es muy útil para la calibración de modelos geomecánicos en tiempo real ya que las pruebas pueden hacerse directamente en campo, reduciendo los costos y tiempo asociados con la caracterización convencional.

  16. Chemical Stabilisation of Sand Part IX: Orthophthalate type Unsaturated Polyester Resin for Inducing Fast setting Behaviour and High Strength

    Directory of Open Access Journals (Sweden)

    B. P. Gupta

    1994-01-01

    Full Text Available Polymer concrete composites have been made from orthophthalate-type unsaturated polyester resin, methyl ethyl ketone peroxide as initiator, cobalt naphthenate as accelerator and desert sand as filler. Composites preferred using resin (10-25 per cent, initiator (4 per cent and accelerator (2 per cent with representative desert sand samples of different particle sizes (0.2-0.02 mm, 2-0.2 mm and 4-2 mm as filler recorded unconfined compression strength ranging from 4 to 442 kg/cm/sup 2/ after curing at 50 degree centigrade in an oven for 0.5-24 h. Using coarse and fine sand samples with 10 and 15 per cent resin systems the maximum strength of 391 and 326 kg/cm/sup 2/ respectively was attained after 2 h of curing at 50 degree centigrade. The fast setting resin system with strength in this range is quite adequate for the construction of chemically stabilised surfaces, which withstand trafficability of vehicles, operation of helicopters and aircraft's requiring a maximum strength up to 275 kg/cm/sup 2/. These composites may prove useful for rapid repair of roads, helipads and runways damaged during operational activities. A mathematical model has been developed for predicting resin percentage needed for obtaining composite material of requisite strength. The observed and model predicted values have been found to show close agreement.

  17. Compressive strength of resin-modified glass ionomer restorative material: effect of P/L ratio and storage time / Resistência à compressão de ionômeros de vidro modificados por resina: efeito da relação P/L e tempos de armazenagem

    Scientific Electronic Library Online (English)

    Mônica, Aratani; Antônio Carlos, Pereira; Lourenço, Correr-Sobrinho; Mário Alexandre Coelho, Sinhoreti; Simonides, Consani.

    2005-12-01

    Full Text Available O objetivo deste estudo foi avaliar a resistência à compressão dos cimentos de ionômero de vidro modificados por resina Vitremer e Fuji II LC, nas relações pó/líquido 1:1, 1:2 e 1:3, por três períodos de armazenagem (24 horas, 7 e 28 dias) em água destilada a 37 ºC. Para cada material, relação pó/lí [...] quido e tempo de armazenagem, cinco corpos-de-prova cilíndricos foram preparados com 4 mm de diâmetro por 6 mm de altura, em moldes de silicone. Os corpos-de-prova foram fotoativados por 40 segundos, em cada extremidade, removidos dos moldes, fotoativado lateralmente (perpendicular ao longo eixo) por 40 segundos, protegidos conforme as instruções dos fabricantes e imersos pelo tempo de teste. Os corpos-de-prova foram submetidos à compressão em uma Instron, à velocidade de 1,0 mm/min até a falha. Os dados foram submetidos à análise de variância e ao teste de Tukey (5%), e mostraram que a resistência à compressão do cimento de ionômero de vidro modificado por resina foi reduzida quando a relação P/L foi diminuída e a armazenagem em água destilada teve pouca influência na resistência à compressão. Abstract in english The aim of this study was to evaluate the compressive strength of resin-modified glass ionomer cement Fuji II LC and Vitremer, in powder/liquid ratios of 1:1, 1:2 and 1:3, at three periods (24 hours, 7 and 28 days) of storage in distilled water at 37ºC. For each material, P/L ratio and storage time, [...] 5 cylindrical specimens were prepared, with 4mm diameter and 6mm height, in silicon moulds. Specimens were light-cured for 40 seconds at each extremity, removed from the moulds and laterally light-cured (perpendicular to long axis) for 40 seconds, protected as recommended by the manufacturers and immersed for the time tested. The specimens were submitted to compressive strength testing in an Instron machine at a crosshead speed of 1.0mm/min until failure. Data were submitted to ANOVA and Tukey's test (5%), and showed that the compressive strength of resin-modified glass ionomer cement was reduced when P/L ratio was reduced and that the storage in water had little influence on compressive strength.

  18. Slug test in an unconfined aquifer: A Richards` equation perspective

    Energy Technology Data Exchange (ETDEWEB)

    Weeber, P. [HSI Geotrans, Roswell, GA (United States); Narasimhan, T.N. [Lawrence Berkeley National Lab., CA (United States)

    1997-10-01

    Slug tests have been used for over 30 years as a means of evaluating hydraulic parameters of aquifers. The interpretation of transient water level data from these tests has almost exclusively been based on fitting the data to analytical solutions or on using semi-analytical methods. Because these methods are constrained by simplifying assumptions, it is useful to investigate the conditions under which these assumptions are reasonable so that the interpretation of field data can be carried out with increased confidence. To this end, the authors investigate the transient flow of water in an unconfined aquifer during a slug test, using a numerical model that solves the generalized Richards` equation. The model accounts for saturated-unsaturated flow, time-dependent seepage face in the well, various combinations of blank casings and well screens, and injection or withdrawal tests. Parametric studies were conducted using a fully penetrating well in a 10 meter thick, homogeneous, isotropic aquifer with an initial hydrostatic condition in order to provide insights into such issues as (1) the difference in response between injection and bail-out tests, (2) the significance of flow through the transient seepage face, and (3) the role of the unsaturated zone. An examination of the flow anatomy suggests that flow in the unsaturated zone is significant and important, although the response of the water level in the well may not be very sensitive to the unsaturated zone processes. A second part of the present study investigated the reasonableness of widely used techniques of interpretation.

  19. Compósitos de cimento Portland com adição de nanotubos de carbono (NTC): Propriedades no estado fresco e resistência à compressão / Portland cement composites with carbon nanotubes (CNT) addition: Properties in freshly state and compressive strength

    Scientific Electronic Library Online (English)

    Marcelo Henrique Farias de, Medeiros; Francielle, Dranka; Alécio Júnior, Mattana; Marienne do Rocio de Mello Maron da, Costa.

    2015-03-01

    Full Text Available Alguns estudos têm sido desenvolvidos sobre a adição de nanotubos de carbono (NTCs) em compósitos cimentícios e indicam melhorias nas propriedades mecânicas, como aumento da resistência à compressão, à tração e diminuição da porosidade. Com base nessas possíveis melhorias, essa pesquisa foi realizad [...] a para analisar a influência dos NTCs na resistência à compressão e fluidez de compósitos de cimento Portland que possam ser usados para reabilitação de estruturas de concreto. Desse modo, foram realizados ensaios de resistência à compressão, squeeze flow, flow table, funil de Marsh e miniabatimento. Foram fixadas uma argamassa e uma pasta de referência (sem adição de nanotubos de carbono), que foram replicadas com mesmo traço e a incorporação de 5 teores de NTCs em relação à massa de cimento: 0,1%, 0,2%, 0,3%, 0,4% e 0,5%. Estes teores foram escolhidos de modo a abranger a faixa de teores mais usadas nas pesquisas sobre NTCs adicionados aos compósitos de cimento Portland. Com relação aos ensaios de medição de fluidez, foi constatado que quanto maior o teor de NTC, mais consistente o compósito cimentício, com indícios de que os teores menores ou iguais a 0,3% são mais adequados para manter a fluidez do compósito de cimento Portland. No caso da resistência à compressão, os resultados indicam que a adição de 0,40% de nanotubos de carbono tende a elevar a resistência em 27%. Por outro lado, a adição de 0,5% de NTC deixou o compósito tão consistente que dificultou a moldagem e a elevação da resistência foi nula comparada a série de referência. Abstract in english Currently there are some studies on the addition of carbon nanotubes (CNTs) in cement composites. These studies indicate enhancements in the mechanical properties, such as increase in compressive strength, tensile strength and durability, and porosity decrease. Based on these possible improvements, [...] this research was conducted to analyze the influence of CNTs on the compressive strength of mortar for rehabilitation of concrete structures, as well as in their consistency. Compressive strength, squeeze flow, flow table, marsh funnel and mini-slump tests were carried. A control mortar and paste were used (without carbon nanotubes added), which was replicated with the same mix proportioning and the incorporation of 5 levels of CNTs related to the cement mass: 0.1%, 0.2%, 0.3%, 0.4% to 0.5%. These concentrations were chosen to cover the commonly range used in researches about Portland cement composites with CNTs addition. Regarding the tests for measuring the fluidity of mortars and pastes, it was found that the higher the percentage of CNT, more consistent the cement Portland composite became, with evidence that smaller or equal to 0.3% levels of NTCs are more adequate to maintain the fluidity of the Portland cement composite. Results indicate that the addition of 0.40% of carbon nanotubes increases the compressive strength by 27%. On the other hand, addition of 0.5% of CNT became the Portland cement composite very consistent, making difficult the molding process, so that the increase in compressive strength was zero compared to the control mortar.

  20. A new diagnostic device for in-situ determination of conventional strength and modulus of deformability in compression of wood parallel to fiber.

    Czech Academy of Sciences Publication Activity Database

    Kloiber, Michal; Kunecký, Ji?í; Tippner, J.; Sebera, V.

    Mexico City : Instituto de Ingeniería UNAM, 2014 - (Peña, F.; Chávez, M.) ISBN N R&D Projects: GA MK(CZ) DF11P01OVV001; GA MŠk(CZ) LO1219 Keywords : semi-destructive device * in-situ measurement * finite element analysis * compression Subject RIV: JN - Civil Engineering http://hdl.handle.net/11104/0238193

  1. Consolidation, permeability, and strength of crushed salt/bentonite mixtures with application to the WIPP [Waste Isolation Pilot Plant

    International Nuclear Information System (INIS)

    Three tests were performed to measure the consolidation, permeability, and compressive strength of specimens prepared from bentonite/crushed salt mixtures. Each mixture comprised 30% bentonite and 70% crushed salt based on total dry weight. Brine was added to each mixture to adjust its water content to either 5 or 10% (nominal) of the total dry weight of the mixture. In the consolidation tests, each specimen was subjected to multiple stages of successively higher hydrostatic stress (pressure). During each stage, the pressure was maintained at a constant level and volumetric strain data were continuously logged. By using multiple stages, consolidation data were obtained at several pressures and the time required to consolidate the specimens to full saturation was reduced. Once full saturation was achieved, each specimen was subjected to a final test stage in which the hydrostatic stress was reduced and a permeability test performed. Permeability was measured using the steady flow of brine and was found to range between 1 x 10-17 and 5 x 10-17 m2. After the final test stage, unconfined compressive strength was determined for each specimen and was found to range between 0.5 and 8.1 MPa. Two constitutive models were fitted to the consolidation data. One relatively simple model related volumetric strain to time while the other related instantaneous density to time, pressure, and initial density. 8 refs., 9 figs., 8 tabs

  2. Pull Off test to evaluate the compressive strength of concrete: an alternative to Brazilian standard techniques / Ensaio de "Pull Off" para avaliar a resistência à compressão do concreto: uma alternativa aos ensaios normalizados no Brasil

    Scientific Electronic Library Online (English)

    E., Pereira; M. H. F. de, Medeiros.

    2012-12-01

    Full Text Available Estimar a resistência à compressão do concreto é uma necessidade em muitos trabalhos de inspeção de estruturas de concreto armado. No Brasil, as ferramentas regulamentadas pela ABNT para este fim são a extração de testemunho, a esclerometria e o ultrassom. Nos Estados Unidos e Europa também são regu [...] lamentadas outras técnicas. O objetivo deste trabalho é estudar a viabilidade do uso do ensaio de "Pull Off" como ferramenta de inspeção em concreto e ainda divulgar a possibilidade de emprego de técnicas complementares as normalizadas no Brasil. Os resultados demonstram que o ensaio "Pull Off" apresenta alto índice de correlação (R²>0,93) com o resultado de resistência à compressão medido tanto em corpos de prova cilíndricos como nos prismáticos. A técnica de esclerometria não apresentou correlação satisfatória (R²?0,6) para o caso de corpos de prova cilíndricos e o ultrassom apresentou alta correlação (R²>0,98), mas se comporta diferente com a mudança de forma dos corpos de prova. Abstract in english To estimate the compressive strength of concrete is necessary in many reinforced concrete structures inspection works. In Brazil, the standard tests for this purpose are: Compressive test in drilled cores, rebound hammer test and ultrasonic test. In the United States and Europe are also regulated ot [...] her techniques. The aim of this paper is to analyze the use of Pull Off test as an inspection tool of concrete and also disclose the possibility of use of complementary techniques to the standard ones in Brazil. The results show that the Pull Off test results in high correlation (R²> 0.93) with the compressive strength, measured in cylindrical and prismatic specimens. The rebound hammer test did not show satisfactory correlation (R²?0.6) for the case of cylindrical specimens. The ultrasonic test showed high correlation (R²> 0.98), but behaves differently with the shape changing of the specimens.

  3. Near-field impact of 216-U-10 (U-Pond) decommissioning on the unconfined aquifer

    International Nuclear Information System (INIS)

    The Hanford Site has been an active liquid waste disposal facility since 1944. Infiltration of liquid effluents from surface ponds, trenches, and high-volume cribs has been directly responsible for the formation of a conical ground-water mound in the unconfined aquifer below 200 West Area. This mound covers more than 143 km2 (56 mi2) of the unconfined aquifer. As of 1980, the crest of the mound was approximately 139 meters (490 feet) above mean sea level, indicating a water-table rise of 24 meters (80 feet) beneath 200 West Area since 1944. The proposed decommissioning of the 216-U-10 surface infiltration pond (U-pond) has raised the question as to the future impact of decommissioning on the unconfined aquifer below the site, and the unconfined ground-water monitoring network. In order to determine the impact of decommissioning, a finite-difference computer model has been calibrated and validated against historical water-level measurements; the model has accurately represented the past and present response of the unconfined aquifer to inflow from 11 liquid waste disposal sites. This computer model was used to predict the water-level decline in the unconfined aquifer in response to U-pond decommissioning. This analysis assumed all inflow into U-pond will be shut off in 1982. The model predicts declines of about 10 meters (33 feet) within the unconfined aquifer 7 years after U-pond shutdown. The model predictions were used to assess the impact of water-table declines associated with U-pond shutdown on Rockwell Hanford Operations and Pacific Northwest Laboratory ground-water monitoring networks; 19 wells will require redrilling, reperforating, or cleaning before 1989 if U-pond is decommissioned in 1982

  4. Synthesis of Zinc Oxide Nanoparticles and Their Effect on the Compressive Strength and Setting Time of Self-Compacted Concrete Paste as Cementitious Composites

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Arefi

    2012-04-01

    Full Text Available In the present study, the mechanical properties of self-compacting concrete were investigated after the addition of different amounts of ZnO nanoparticles. The zinc oxide nanoparticles, with an average particle size of about 30 nm, were synthesized and their properties studied with the help of a scanning electron microscope (SEM and X-ray diffraction. The prepared nanoparticles were partially added to self-compacting concrete at different concentrations (0.05, 0.1, 0.2, 0.5 and 1.0%, and the mechanical (flexural and split tensile strength of the specimens measured after 7, 14, 21 and 28 days, respectively. The present results have shown that the ZnO nanoparticles were able to improve the flexural strength of self-compacting concrete. The increased ZnO content of more than 0.2% could increase the flexural strength, and the maximum flexural and split tensile strength was observed after the addition of 0.5% nanoparticles. Finally, ZnO nanoparticles could improve the pore structure of the self-compacted concrete and shift the distributed pores to harmless and less-harmful pores, while increasing mechanical strength.

  5. IGF-1 does not moderate the time-dependent transcriptional patterns of key homeostatic genes induced by sustained compression of bovine cartilage

    OpenAIRE

    Wheeler, Cameron A.; Jafarzadeh, Seyed R.; Rocke, David M.; Grodzinsky, Alan J

    2009-01-01

    Objective To determine changes in chondrocyte transcription of a range of anabolic, catabolic and signaling genes following simultaneous treatment of cartilage with Insulin-like growth factor-1 (IGF-1) and ramp-and-hold mechanical compression, and compare with effects on biosynthesis. Methods Explant disks of bovine calf cartilage were slowly compressed (unconfined) over 3-min to their 1 mm cut-thickness (0%-compression) or to 50%-compression with or without 300 ng/ml IGF-1. Expres...

  6. Avaliação da força de preensão em ratos Wistar, normais e obesos, submetidos à natação com sobrecarga após compressão do nervo mediano / Evaluation of grip strength in normal and obese Wistar rats submitted to swimming with overload after median nerve compression

    Scientific Electronic Library Online (English)

    Josinéia Gresele, Coradinia; Camila Mayumi Martin, Kakihata; Regina Inês, Kunz; Tatiane Kamada, Errero; Maria Lúcia, Bonfleur; Gladson Ricardo Flor, Bertolini.

    2015-02-01

    Full Text Available Objetivo Verificar a funcionalidade por meio da força muscular de preensão em animais com obesidade induzida por glutamato monossódico (MSG) e animais controle, que sofreram compressão do nervo mediano direito, tendo como tratamento a natação com carga. Métodos Ratos Wistar neonatos durante os prim [...] eiros cinco dias de vida receberam injeções subcutâneas de MSG. O grupo controle recebeu solução salina hiperosmótica. Quarenta e oito ratos foram divididos em seis grupos: G1(controle); G2 (controle com lesão); G3 (controle com lesão + natação); G4 (obesos); G5 (obesos com lesão); G6 (obesos com lesão + natação). Os animais dos grupos G2, G3, G5 e G6 foram submetidos à compressão do nervo mediano e os dos grupos G3 e G6 foram tratados, após a lesão, com exercício de natação com carga durante três semanas. A natação teve duração progressiva conforme as semanas, de 20, 30 e 40 minutos. A força muscular foi avaliada por meio de um medidor de força de preensão no pré-operatório, no terceiro, sétimo, 14° e 21° dia pós-operatório. Os resultados foram expressos e analisados por estatística descritiva e inferencial. Resultados Quando comparada a força de preensão entre as avaliações, indiferentemente de grupos, na segunda avaliação os animais apresentaram menor força de preensão. Os grupos G1 e G4 apresentaram força de preensão maior, em comparação com os grupos G2, G3, G4 e G6. Conclusão O exercício de natação com sobrecarga não foi eficaz em promover melhoria na força muscular de preensão após lesão de compressão do nervo mediano direito em ratos controle e obesos-MSG. Abstract in english Objective To verify the functionality through muscle grip strength in animals with obesity induced by monosodium glutamate (MSG) and in control animals, which suffered compression of the right median nerve, and treated with swimming with overload. Methods During the first five days of life, neonata [...] l Wistar rats received subcutaneous injections of MSG. The control group received a hypertonic saline solution. Forty-eight rats were divided into six groups: G1 (control); G2 (control + injury); G3 (control + injury + swimming); G4 (obese); G5 (obese + injury); and G6 (obese + injury + swimming). The animals in groups G2, G3, G5 and G6 were submitted to compression of the median nerve and G3 and G6 groups were treated, after injury, with swimming exercise with load for three weeks. The swimming exercise had a progressive duration, according to the week, of 20, 30 and 40 min. Muscle strength was assessed using a grip strength meter preoperatively and on the 3rd, 7th, 14th and 21st days after surgery. The results were expressed and analyzed using descriptive and inferential statistics. Results When the grip strength was compared among assessments regardless of group, in the second assessment the animals exhibited lower grip strength. G1 and G4 groups had greater grip strength, compared to G2, G3, G4 and G6. Conclusion The swimming exercise with overload has not been effective in promoting improvement in muscle grip strength after compression injury of the right median nerve in control and in obese-MSG rats.

  7. Temperature and moisture content effects on compressive strength parallel to the grain of paricá / Efeito da temperature e do teor de umidade na resistência à compressão paralela às fibras do paricá

    Scientific Electronic Library Online (English)

    Manuel Jesús Manríquez, Figueroa; Poliana Dias de, Moraes; Fernanda Almeida, Maestri.

    2015-03-01

    Full Text Available O objetivo deste estudo é avaliar o efeito da temperatura e do teorde umidade na resistência à compressão paralela às fibras do paricá (Schizolobium amazonicum Huber ex. Ducke) de florestas plantadas. Os experimentos foram realizados em 3 amostras de madeira em diferentes condições: aquecida (HT), t [...] ratamento térmico (TT), e saturada em água (WS). A amostra HT consistiu-se de 105 corpos de prova classificados em 15 grupos, a amostra TT consistiu-se em corpos de prova classificados em 15 grupos, a amostra WS consistiu-se em 90 corpos de prova classificados em 9 grupos. Os corpos de prova das amostras HT e WS foram testados em uma faixa de temperatura de 20 a 230 ºC e de 20 a 100 ºC, respectivamente. Os corpos de prova da amostra HT foram testados à temperatura ambiente, mas após serem submetidos a um tratamento térmico. As amostras HT, TT e WS apresentaram redução da resistência à compressão, as quais atingiram 65%, 76% e 59% da resistência à compressão à temperatura ambiente, respectivamente. A redução da resistência à compressão das amostras de HT e WS pode ser associada à degradação térmica dos polímeros da madeira e da redução do teor de umidade. Para a amostra TT, a resistência dos corpos de prova aumentou para uma temperatura de pré-aquecimento de até 170 °C, devido à redução do teor de umidade. Abstract in english The aim of this study is to evaluate the effect of the temperature and moisture content on the compressive strength parallel to the grain of paricá (Schizolobium amazonicum Huber ex. Ducke) from cultivated forests. The experiments were carried out on 3 timber samples under different conditions: heat [...] ed (HT), thermal treatment (TT) and water saturated (WS). The HT sample consisted of 105 clear specimens assembled in 15 groups, the TT consisted of 90 clear specimens assembled in 15 groups and the WS consisted of 90 clear specimens assembled in 9 groups. The specimens from HT and WS samples were tested at a temperature range from 20 to 230 ºC and 20 to 100 ºC, respectively. The HT specimens were tested at ambient temperature, but after being submitted to thermal treatment. The HT, TT and WS samples present a decrease in the compressive strength, reaching 65%, 76% and 59% of the compressive strength at room temperature, respectively. The decrease in the compressive strength of the HT and WS samples can be associated to the thermal degradation of wood polymers and the moisture content. For the TT sample, the strength increased for a pre-heating temperature of up to 170 °C due to the reduction in the moisture content of the specimens.

  8. Assessment of strength properties of cemented paste backfill by ultrasonic pulse velocity test.

    Science.gov (United States)

    Y?lmaz, Tekin; Ercikdi, Bayram; Karaman, Kadir; Külekçi, Gökhan

    2014-07-01

    Ultrasonic pulse velocity (UPV) test is one of the most popular non-destructive techniques used in the assessment of the mechanical properties of concrete or rock materials. In this study, the effects of binder type/dosage, water to cement ratio (w/c) and fines content (cemented paste backfill (CPB) samples were investigated and correlated with the corresponding unconfined compressive strength (UCS) data. A total of 96 CPB samples prepared at different mixture properties were subjected to the UPV and UCS tests at 7, 14, 28 and 56-days of curing periods. UPV and UCS of CPB samples of ordinary Portland cement (CEM I 42.5 R) and sulphate resistant cement (SRC 32.5) initially increased rapidly, but, slowed down after 14 days. However, UPV and UCS of CPB samples of the blast furnace slag cement (CEM III/A 42.5 N) steadily increased between 7 and 56 days. Increasing binder dosage or reducing w/c ratio and fines content (<20 ?m) increased the UCS and UPV of CPB samples. UPV was found to be particularly sensitive to fines content. UCS data were correlated with the corresponding UPV data. A linear relation appeared to exist between the UCS and UPV of CPB samples. These findings have demonstrated that the UPV test can be reliably used for the estimation of the strength of CPB samples. PMID:24602334

  9. Evaluación in vitro de la resistencia compresiva de un sellante resinoso fluorado pre y post liberación de flúor / In vitro compressive strength of fluoride-containing resin-based sealant before and after fluoride release

    Scientific Electronic Library Online (English)

    C, Vergara; S, Uribe.

    2012-04-01

    Full Text Available Objetivo: Evaluar in vitro la resistencia compresiva de un sellante resinoso fluorado (F) pre y post liberación de flúor luego de la inmersión en agua. Método: Se utilizaron 40 probetas de 6 mm de alto y 20 mm de diámetro de sellante resinoso fluorado (FluroShield, Brasil, Dentsply) y de sellante no [...] fluorado (Concise(TM) Light Cured White Sealant, USA, 3M ESPE). Las probetas fueron divididas en cuatro grupos, dos de sellante resinoso fluorado (F1 y F2) y dos de control (C1 y C2). Un grupo de probetas de sellante fluorado y un grupo del control (F1/C1) se mantuvieron sin exposición al agua, mientras que los grupos restantes (F2/C2) fueron inmersos en agua destilada por 30 días. Se midió la liberación de flúor desde el grupo F2 mediante el método de electrodo selectivo los días 1, 2, 3 y 30. Posteriormente se midió la resistencia compresiva mediante una máquina de ensayos mecánicos universales (Lloyd, LR 100, UK) con una velocidad de cruceta de 1 mm/min. Las comparaciones entre los grupos F1 vs F2 y C1 vs C2 se analizaron con t-Student. El nivel de significancia se estableció a 0.05. Resultados: La resistencia compresiva en MPa antes y después de la inmersión en agua para el sellante resinoso fluorado fue 337.2 y 337.4, mientras que la del sellante control fue 203.8 y 213.4. Para ambos grupos las diferencias observadas no fueron significativas. Se observó un patrón de liberación de flúor inicial de 1.9 ppm durante las primeras 24 horas para luego decaer a 0.0 ppm al tercer día de liberación. Conclusión: La liberación de flúor desde un sellante resinoso fluorado no afectó su resistencia compresiva en este estudio in vitro. Abstract in english Aim: To evaluate in vitro compressive strength of fluoride-containing resin-based sealant (F) before and after fluoride release in water. Materials and Methods: We used 40 specimens with 6 mm of height and 20 mm of diameter using fluoride-containing resin-based sealant (FluroShield,Brasil, Dentsply) [...] and non-fluoride-containing resin-based sealant (Concise (TM) Light Cured White Sealant, USA, 3M ESPE). The specimens were divided into four groups, two fluoride-containing resin-based sealants (F1 and F2) and two like control groups (C1 and C2). A group of specimens of fluoride-containing resin-based sealant and a control group (F1/C1) remained without exposure to water, while other groups (F2/C2) were immersed in distilled water for 30 days. The release of fluoride from the F2 was measured through selective electrode method on days 1, 2, 3 and 30. Subsequently, the compressive strength was measured using a universal testing machine (Lloyd, LR 100, UK) with a crosshead speed of 1 mm/min. Comparisons between groups F1 vs F2 and C1 vs C2 were analyzed with t-Student. The significance level was set at 0.05. Results: The compressive strength (Mpa) before and after immersion in water for fluoride-containing resin-based sealant was 337.2 and 337.4, while the control sealant was 203.8 and 213.4. For both groups the observed differences were not significant. The initial fluoride release was 1.9 ppm during the first 24 hours and then declined to 0.0 ppm during the third day of release. Conclusion: In this in vitro study, the release of fluoride from a fluoride-containing resin-based sealant does not affect compressive strength.

  10. Modelamiento de la resistencia a la compresión de concretos alternativos, usando la metodología de superficie de respuesta / Modeling of the compressive strength of alternative concretes using the response surface methodology

    Scientific Electronic Library Online (English)

    Susan, Bernal López; Marisol, Gordillo; Ruby, Mejía de Gutiérrez; Erich, Rodríguez Martínez; Silvio, Delvasto Arjona; Robert, Cuero.

    2009-09-01

    Full Text Available En este artículo se presentan los valores de resistencia a la compresión de concretos alternativos de activación alcalina, basados en mezclas binarias de una escoria siderúrgica (GBFS) y un metacaolín (MK) de alta pureza, a edades de curado de 7, 28, 90 y 180 días. Como activante alcalino se empleó [...] una solución de waterglass (Na2SiO3.nH2O + NaOH), cuya dosificación fue ajustada para lograr una relación molar SiO2/Al2O3 del sistema cementante en un rango entre 3,6 y 4,4. Los resultados a 28 días de curado se analizaron a través de la Metodología de Superficie de Respuesta (M.S.R) considerando como variables en estudio: el contenido de MK en el cementante (CMK) y la relación molar SiO2/Al2O3 (Rm). A partir del modelo estadístico obtenido, se presentan los contornos de resistencia a la compresión de estos materiales en función de los factores en estudio y se predice que los concretos producidos con cementos alternativos con una relación GBFS/(GBFS+MK) de 0,9 y con un Rm de 4,2, podrían desarrollar resistencias a la compresión de hasta 74 MPa. Cabe anotar que los concretos basados en sistemas binarios de GBFS/ MK presentan resistencias a la compresión de hasta 56 MPa y 80 MPa, a 7 y 180 días de curado respectivamente, comportamiento característico de materiales de alto desempeño mecánico. Abstract in english In this paper is to present the compressive strength reported by alternative concrete at ages of curing of 7, 28, 90 and 180 days. These materials were produced applying alkaline activation processes to binary systems based on granulated-blast furnace slag (GBFS) and high purity metakaolin (MK). As [...] alkali-activator a waterglass solution (Na2SiO3.nH2O + NaOH) was used and its dosages were adjusted in order to get a SiO2/Al2O3 molar ratio between 3.6 and 4.4. The results at 28 days of curing were analyzed through the statistical methodology of response surface (M.S.R). As study factors have been considered: the amount of MK into the binder (CMK) and the SiO2/Al2O3 molar ratio in the binder (Rm). From the proposed statistical model the compressive strength contours, as function of the binder variables, are identified and it is predicted that concretes elaborated from alternative binders with a GBFS/(GBFS+MK) ratio of 0.9 and Rm of 4.2, it is possible to obtain compressive strengths up to 74 MPa. It important stand out that concrete composed by binary systems of GBFS/MK to develop compressive strengths up to 56 MPa at 7 days of curing and up to 80 MPa at 180 days of curing, which is expected for high mechanical performance materials.

  11. Efecto del envejecimiento artificial acelerado sobre la resistencia a compresión de resinas compuestas / Effect of artificial accelerated aging on compression strength of composite resin

    Scientific Electronic Library Online (English)

    Priscila, Nogueira Gomes; José Carlos, Rabelo Ribeiro; Marcos, Ribeiro Moysés; Andréa, Candido Dias; Sérgio, Candido Dias.

    2009-03-01

    Full Text Available Este estudio tuvo como objetivo analizar el efecto del envejecimiento artificial acelerado (EAA) sobre la resistencia a compresión de las resinas compuestas Filtek Z-250 (F), Charisma (C), Durafil VS (D), Supreme para cuerpo (SNc) e Supreme translúcido (SNt). Fueron confeccionados 16 especímenes con [...] cada resina compuesta con dimensiones de 4x8mm. Las resinas fueron inseridas en tres incrementos y sobre el último incremento fue colocada una matriz de poliéster y una lamina de vidrio con la finalidad obtener una superficie regular. Cada incremento fue polimerizado con una intensidad de luz entre 580 y 600 mW/cm², la cual era monitoreada con un radiómetro (Gnatus) durante todo el tiempo de utilización. Veinticuatro horas después de la obtención de las muestras, 8 muestras de cada material fueron sometidas a los ensayos de compresión (grupo control) los cuales fueron realizados en una maquina EMIC DL 2000, con una célula de carga de 2000Kgf y velocidad de 0,5mm/min. Las otras 8 muestras de cada material fueron colocados en la máquina de EAA, las cuales permanecieron durante 196 horas, las mismas que equivalen a 5 años de envejecimiento y enseguida sometidos a los ensayos de compresión. Los resultados, fueron sometidos al ANOVA y test de Tukey (p24h. Se pudo concluir que el envejecimiento artificial acelerado aumento la resistencia a compresión de las resinas F, C e SNc. Abstract in english The aim of this study was to analyze the effect of artificially accelerated aging (AAA) on the resistance to compression of resin composites Filtek Z-250 (F), Charisma (C), Durafill VS (D), Supreme for body (SNC) and Supreme Translucent (SNt). Sixteen test specimens measuring 4 x 8 mm were made of e [...] ach resin composite. The resins were inserted in three increments, and on the last of them, a polyester strip and glass slide were placed for the purpose of obtaining a regular surface. Each increment was polymerized by light intensity of 580 to 600 mw/cm², which was monitored with a radiometer (Gnatus) throughout the time of use. Twenty-four hours after the samples were obtained, 8 specimens of each material were submitted to the compression test (Control Group) performed with an EMIC DL 2000, machine, with a 2000 Kgf load cell at a speed of 0.5 mm/min. The other 8 samples of each material were placed in an AAA machine, and remained there for 196 hours, equivalent to 5 years of aging. Next they were submitted to the compression test. The values were submitted to ANOVA and the Tukey test (p24h. It was concluded that artificially accelerated aging increased the resistance to compression of the resin composites F, C and SNc.

  12. Resistencia compresiva vidrio ionómero Ionofil Molar® y Vitremer® según tiempo de exposición en saliva artificial / Compressive strength of glass ionomer Ionofil Molar® and Vitremer® according to exposure time in artificial saliva

    Scientific Electronic Library Online (English)

    R, Hernández González; R, Moraga Castillo; M, Velásquez Castilla; F, Gutiérrez Flores.

    2013-08-01

    Full Text Available Objetivo: El conocimiento sobre las propiedades mecánicas de los materiales dentales es fundamental para una correcta indicación y funcionamiento en la cavidad oral, permitiéndole al profesional optar por el que presente mejor comportamiento durante la masticación. El objetivo de este estudio fue ev [...] aluar la resistencia a la compresión de Ionofil Molar® y Vitremer®, según tiempo de exposición en saliva artificial. Materiales y Métodos: Se prepararon 5 muestras para cada material evaluadas a los tiempos 0, 168 y 504 horas en saliva artificial a 37° C, según las especificaciones propuestas por la norma ANSI/ADA n°66. La resistencia a la compresión se determinó sometiendo las muestras a cargas en un equipo de ensayo de fuerzas Instron® a una velocidad de carga de 1 mm/min. Se realizó una prueba de homogeneidad de varianzas, la normalidad se determinó mediante Kolmogorov-Smirnov, y posteriormente un ANOVA. Se realizó el test de Tukey para determinar si existió diferencia significativa entre variables. Resultados: La resistencia compresiva de Vitremer no presentó diferencias estadísticamente significativas en el tiempo (p=0.282), a diferencia de Ionofil Molar, que sí presentó diferencias entre los distintos tiempos (p=0.011). Además en las muestras sin sumergir, no hubo diferencia estadísticamente significativa entre materiales (p=0.091), en cambio sí existió diferencia al cabo de una y tres semanas de exposición (p=0). Conclusión: El vidrio ionómero Vitremer presenta mayor resistencia compresiva a lo largo del tiempo, sin presentar alteraciones significativas en el tiempo al ser inmerso en saliva, a diferencia del Ionofil Molar que disminuyó significativamente su resistencia en las mismas condiciones. Abstract in english Objective: Understanding the mechanical properties of dental materials is essential for proper indication and a correct functioning in the oral cavity, as it allows the dentist to choose the material that presents better performance during mastication. The aim of this study was to evaluate the compr [...] essive strength of Ionofil Molar and Vitremer, according to the exposure time in artificial saliva. Materials: 5 samples were prepared for each material evaluated at 0, 168 and 504 hours in artificial saliva at 37º Celsius, according to the specifications suggested by ANSI/ADA specification No 66. The compressive strength was determined by subjecting the samples to an Instron strength-testing machine at a load speed of 1 mm/min. A test of homogeneity of variance was conducted; normality was determined by Kolmogorov-Smirnov, and ANOVA. Tukey’s test was performed to determine if significant differences existed between variables. Results: Vitremer compressive strength did not show statistically significant differences over time (p=0.282), unlike Ionofil Molar, which did present differences between times (p=0.011). Besides, there were no statistically significant differences in the samples without submerging (p=0.091), unlike after one to three weeks of exposure, were a difference did exist (p=0). Conclusion: Vitremer has greater compressive strength over time, without showing significant changes in time after being immersed in saliva, unlike Ionofil Molar, whose resistance decreased significantly under the same conditions.

  13. Effect of chlorhexidine gluconate on porosity and compressive strength of a glass ionomer cement / Efeito da adição de gluconato de clorexidina na porosidade e resistência à compressão de um cimento de ionômero de vidro

    Scientific Electronic Library Online (English)

    Luana Mafra, MARTI; Elcilaine Rizzato, AZEVEDO; Margareth da, MATA; Elisa Maria Aparecida, GIRO; Angela Cristina Cilense, ZUANON.

    2014-07-01

    Full Text Available INTRODUÇÃO: Por apresentar ampla atividade antibacteriana, a clorexidina (CHX) tem sido amplamente utilizada em odontologia, podendo ser facilmente incorporada ao cimento de ionômero de vidro (CIV) e liberada consequentemente na cavidade bucal. OBJETIVO: O objetivo neste estudo foi avaliar a p [...] orosidade e resistência à compressão de um CIV, ao qual foi adicionado diferentes concentrações de CHX. MATERIAL E MÉTODO: Os espécimes foram preparados com CIV (Ketac Molar Esaymix) e divididos em 4 grupos de acordo com a concentração de CHX: controle, 0,5% e 1% e 2% (n=10). Para análise dos poros os espécimes foram fraturados com auxílio de martelo e cinzel cirúrgicos, de modo que a fratura era realizada no centro do corpo de prova, dividindo-o ao meio e as imagens obtidas no microscópio eletrônico de varredura (MEV) analisadas no software Image J. O teste de resistência à compressão foi realizado na máquina de ensaios mecânicos (EMIC - Equipamentos e Sistemas de Ensaios Ltda, São José dos Pinhais, PR, Brazil). A análise estatística foi realizada por ANOVA, complementada pelo teste de Tukey. Nível de significância adotado de 5%. RESULTADO: Não se observou alteração estatisticamente significante entre os grupos estudados tanto para o número de poros quanto para a resistência à compressão. CONCLUSÃO: O uso de CIV associado ao gluconato de CLX a 1% e 2% é a melhor opção para ser utilizada na clínica odontológica. Abstract in english INTRODUCTION: For presenting wide antibacterial activity, chlorhexidine (CHX) has been extensively used in dentistry and can be easily incorporated into the glass ionomer cement (GIC) and consequently released into the oral cavity. AIM: The aim of this study was porosity and compression strengt [...] h of a GIC, that was added to different concentrations of CHX. MATERIAL AND METHOD: Specimens were prepared with GIC (Ketac Molar Esaymix) and divided into 4 groups according to the concentration of CHX: control, 0.5% and 1% and 2% (n = 10). For analysis of pores specimens were fractured with the aid of hammer and chisel surgical, so that the fracture was performed in the center of the specimens, dividing it in half and images were obtained from a scanning electron microscope (SEM) analyzed in Image J software. The compressive strength test was conducted in a mechanical testing machine (EMIC - Equipment and Testing Systems Ltd., Joseph of the Pines, PR, Brazil). Statistical analysis was performed by ANOVA, Tukey test. Significance level of 5%. RESULT: No statistically significant changes between the study groups was observed both for the number of pores as well as for the compressive strength. CONCLUSION: The use of GIC associated with CHX gluconate 1% and 2% is the best option to be used in dental practice.

  14. Characterization of Erodibility Using Soil Strength and Stress-Strain Indices for Soils in Some Selected Sites in Imo State

    Directory of Open Access Journals (Sweden)

    N.A.A. Okereke

    2012-07-01

    Full Text Available In this study, initial soil strength indices (qu and stress-strain characteristics namely failure strain (?f; area under the stress-strain curve up to failure (Is and stress-strain modulus between no load and failure (Es were investigated as potential indicators for characterizing the erosion resistance of two compacted soils namely Sandy Clay Loam (SCL and Clay Loam (CL in some selected sites in Imo State, Nigeria. The unconfined compressive strength (used in obtaining strength indices and stress-strain measurements were obtained as a function of moisture content in percentage (mc % and dry density (?d. Test were conducted over a range of 8 to 30% moisture content and 1.0 to 2.0 g/cm3 dry density at applied loads of 20, 40, 80, 160 and 320 kPa. Based on the results, it was found out that initial soil strength alone was not a good indicator of erosion resistance. For instance in the comparison of exponents of mc % and ?d for jet index or erosion resistance index (Ji and the strength measurements, qu and Es (Table 1 agree in signs for mc %, but are opposite in signs for ?d. Therefore there is an inconsistency in exponents making it difficult to develop a relationship between the strength parameters and Ji for this data set. In contrast, the exponents of mc % and ?d for Ji and ?f and Is are opposite in signs (Table 1, there is potential for an inverse relationship. The measured stress-strain characteristics however, appeared to have potential in providing useful information on erosion resistance. The models developed for the prediction of the extent or the susceptibility of soils to erosion and subjected to sensitivity test on some selected sites as shown in Table 2 achieved over 90% efficiency in their functions.

  15. An evaluation of aquifer intercommunication between the unconfined and Rattlesnake Ridge aquifers on the Hanford Site

    International Nuclear Information System (INIS)

    During 1986, Pacific Northwest Laboratory conducted a study of a portion of the Rattlesnake Ridge aquifer (confined aquifer) that lies beneath the B Pond - Gable Mountain Pond area of the Hanford Site. The purpose was to determine the extent of intercommunication between the unconfined aquifer and the uppermost regionally extensive confined aquifer, referred to as the Rattlesnake Ridge aquifer. Hydraulic head data and chemical data were collected from the ground water in the study area during December 1986. The hydraulic head data were used to determine the effects caused by water discharged to the ground from B Pond on both the water table of the unconfined aquifer and the potentiometric surface of the confined aquifer. The chemical data were collected to determine the extent of chemical constituents migrating from the unconfined aquifer to the confined aquifer. Analysis of chemical constituents in the Rattlesnake Ridge aquifer demonstrated that communication between the unconfined and confined aquifers had occurred. However, the levels of contaminants found in the Rattlesnake Ridge aquifer during this study were below the DOE Derived Concentration Guides

  16. The Effects of Eggshell Ash on Strength Properties of Cement-stabilized Lateritic

    Directory of Open Access Journals (Sweden)

    Okonkwo U. N

    2012-04-01

    Full Text Available Eggshell ash obtained by incinerating Fowls’ eggshells to ash has been established to be a good accelerator for cement-bound materials and this would be useful for road construction work at the peak of rainy seasons for reducing setting time of stabilized road pavements. However this should be achieved not at the expense of other vital properties of the stabilized matrix. This is part of the effort in adding value to agricultural materials which probably cause disposal problems. Thus this study aimed at determining the effect of eggshell ash on the strength properties of cement-stabilized lateritic soil. The lateritic soil was classified to be A-6(2 in AASHTO rating system and reddish-brown clayey sand (SC in the Unified Classification System. Constant cement contents of 6% and 8% were added to the lateritic soil with variations in eggshell ash content of 0% to 10% at 2% intervals. All proportions of cement and eggshell ash contents were measured in percentages by weight of the dry soil. The Compaction test, California Bearing Ratio test, Unconfined Compressive Strength test and Durability test were carried out on the soil-cement eggshell ash mixtures. The increase in eggshell ash content increased the Optimum Moisture Content but reduced the Maximum Dry Density of the soil-cement eggshell ash mixtures. Also the increase in eggshell ash content considerably increased the strength properties of the soil-cement eggshell ash mixtures up to 35% in the average but fell short of the strength requirements except the durability requirement was satisfied.

  17. Tissue-engineered articular cartilage exhibits tension-compression nonlinearity reminiscent of the native cartilage.

    Science.gov (United States)

    Kelly, Terri-Ann N; Roach, Brendan L; Weidner, Zachary D; Mackenzie-Smith, Charles R; O'Connell, Grace D; Lima, Eric G; Stoker, Aaron M; Cook, James L; Ateshian, Gerard A; Hung, Clark T

    2013-07-26

    The tensile modulus of articular cartilage is much larger than its compressive modulus. This tension-compression nonlinearity enhances interstitial fluid pressurization and decreases the frictional coefficient. The current set of studies examines the tensile and compressive properties of cylindrical chondrocyte-seeded agarose constructs over different developmental stages through a novel method that combines osmotic loading, video microscopy, and uniaxial unconfined compression testing. This method was previously used to examine tension-compression nonlinearity in native cartilage. Engineered cartilage, cultured under free-swelling (FS) or dynamically loaded (DL) conditions, was tested in unconfined compression in hypertonic and hypotonic salt solutions. The apparent equilibrium modulus decreased with increasing salt concentration, indicating that increasing the bath solution osmolarity shielded the fixed charges within the tissue, shifting the measured moduli along the tension-compression curve and revealing the intrinsic properties of the tissue. With this method, we were able to measure the tensile (401±83kPa for FS and 678±473kPa for DL) and compressive (161±33kPa for FS and 348±203kPa for DL) moduli of the same engineered cartilage specimens. These moduli are comparable to values obtained from traditional methods, validating this technique for measuring the tensile and compressive properties of hydrogel-based constructs. This study shows that engineered cartilage exhibits tension-compression nonlinearity reminiscent of the native tissue, and that dynamic deformational loading can yield significantly higher tensile properties. PMID:23791084

  18. RELACIÓN ENTRE LA RESISTENCIA A LA COMPRESIÓN Y LA POROSIDAD DEL CONCRETO EVALUADA A PARTIR DE PARÁMETROS ULTRASÓNICOS / RELATIONSHIP BETWEEN COMPRESSIVE STRENGTH AND POROSITY OF CONCRETE EVALUATED FROM ULTRASONIC PARAMETERS

    Scientific Electronic Library Online (English)

    LUZ AMPARO, QUINTERO ORTÍZ; JULIAN, HERRERA; LAURA, CORZO; JOHANA, GARCÍA.

    2011-06-01

    Full Text Available El propósito de la presente investigación fue evaluar la resistencia a la compresión y la porosidad en muestras de concreto empleando medidas de velocidad de pulso ultrasónico (VPU) y posteriormente establecer relaciones entre las propiedades estudiadas y la VPU. Las muestras fueron preparadas con d [...] iferentes relaciones agua/cemento (a/c) y curadas durante 28 días en condiciones ambientales bajo techo. El trabajo se planteó teniendo en cuenta que la porosidad es un factor importante que influye en el material, ya que permite el ingreso de agentes agresivos dentro de la matriz del concreto afectando su resistencia a la compresión, y en general disminuyendo el tiempo de vida útil proyectado para la estructura. Estudios anteriores han demostrado que la porosidad depende entre otros factores de la relación a/c empleada en la mezcla. Uno de los métodos para evaluar las estructuras sin afectarlas es el ultrasonido, por medio de este se puede estimar la resistencia mecánica tanto in situ como en laboratorio. La técnica ultrasónica de mayor aplicación es la de VPU. En el presente trabajo se midió la resistencia a la compresión, la porosidad y la VPU a probetas de concreto fabricadas con cemento Portland tipo I y relaciones a/c de 0,45, 0,50, 0,55 y 0,60. Los experimentos fueron llevados a cabo a 7, 14 y 28 días de curado. Este primer trabajo acerca de la aplicación de la técnica de VPU como ensayo no destructivo para la evaluación de la calidad del concreto, permitió verificar el potencial de la técnica como medio para estimar el comportamiento del material durante el tiempo de este estudio. Abstract in english The purpose of this research was to evaluate the compressive strength and porosity of concrete samples using ultrasonic pulse velocity (UPV) measurements and then establish relationships between the studied properties and the UPV. The samples were prepared with different water/cement ratios (w/c) an [...] d cured for 28 days at indoor environmental conditions. This work was raised taking into account that porosity is an important factor that influences the material, allowing aggressive agents to enter the concrete matrix affecting its compressive strength, and in general decreasing the projected lifetime of the structure. Previous studies have proved that porosity strongly depends on the water/cement ratio (w/c) used for the mixture. One method to evaluate structures without affecting them is ultrasounds. Through this technique, mechanical resistance can be estimated both in situ and in laboratory. The ultrasonic technique that is widely used is the ultrasonic pulse velocity (UPV). In this paper the compressive strength, the porosity, and the ultrasonic pulse velocity were measured in concrete test tubes manufactured with Portland cement type I, using water/cement ratios of 0.45, 0.50, 0.55, and 0.60. The experiments were carried out at 7, 14 y 28 curing days. This first work about UPV technique application as a non-destructive testing for assessing concrete quality, allowed studying the potential of technique itself, as a means to estimate the material behavior, in this case during the curing stage under environment conditions.

  19. Efecto de la adición mineral cal- zeolita sobre la resistencia a la compresión y la durabilidad de un hormigón Effect of lime- zeolite binder on compression strength and durability properties of a concrete

    Directory of Open Access Journals (Sweden)

    Juan José Dopico Montes de Oca

    2009-08-01

    Full Text Available La práctica internacional reporta una creciente utilización de los hormigones de altas resistencias, con excelentes resultados en la durabilidad, relacionado con la obtención de una matriz cementicia muy densa, a partir del empleo de altos volúmenes de adiciones minerales muy finas, tales como las cenizas volantes, la microsílice, el metacaolín y otros materiales. Para los países emergentes, entre los cuales se ubica Cuba, el uso de estas adiciones puzolánicas resultan una solución relativamente costosa, dado los altos precios de importación de estos materiales puzolánicos, de ahí la utilidad de usar las fuentes nacionales de puzolanas disponibles de probada reactividad, como sustituías parciales de los contenidos de Cemento Portland Ordinario (CPO en las mezclas de hormigón, sin que se vean afectadas significativamente sus propiedades. El presente trabajo muestra la influencia del nivel de sustitución de los contenidos de Cemento Portland por adición mineral cal- puzolana, en combinación con superplastificante, en el comportamiento de la resistencia a la compresión y la durabilidad de un hormigón. Varios niveles de sustitución de CPO son evaluados, utilizando toba zeolítica como puzolana. Los resultados obtenidos corroboran la posibilidad del reemplazo de altos volúmenes de CPO por aglomerante cal-zeolita, sin que se afecten la resistencia a compresión requerida y su comportamiento ante la acción del ingreso del ion cloruro y la carbonatación.The international construction practice reports a remarkable use and development of high performance concretes, with excellent results in the durability properties, associated with a very dense cement matrix, defined from the use of high volumes of very fine minerals additions, such as, fly ash, silica fume, metakaolin and other fine powders. For the developing countries, among others Cuba, the use of these pozzolanic additions are relatively expensive, given for the high import prices of these pozzolanic materials, thus, the utility of using the national available pozzolanic sources with proven reactivity, as a partial substitute of the Ordinary Portland Cement (OPC contents in the concrete mixtures without its properties are affected. The present paper shows the results of the study on the influence of substitution level of Ordinary Portland Cement contents by lime - pozzolan binder in combination with chemical admixture, in the behavior of the compression strength and the durability properties of a concrete. Several levels of OPC substitution are evaluated, using zeolite as pozzolan. The results obtained prove the possibility to carry out the partial replacement of high volumes of OPC by lime - zeolite binder, without affecting the values of compression strength required and their behavior before action of the chloride ion penetration and the carbonation.

  20. Efecto de la adición mineral cal- zeolita sobre la resistencia a la compresión y la durabilidad de un hormigón / Effect of lime- zeolite binder on compression strength and durability properties of a concrete

    Scientific Electronic Library Online (English)

    Juan José, Dopico Montes de Oca; José Fernando, Martirena Hernandez; Alberto, López Rodríguez; Raúl, González López.

    2009-08-01

    Full Text Available La práctica internacional reporta una creciente utilización de los hormigones de altas resistencias, con excelentes resultados en la durabilidad, relacionado con la obtención de una matriz cementicia muy densa, a partir del empleo de altos volúmenes de adiciones minerales muy finas, tales como las c [...] enizas volantes, la microsílice, el metacaolín y otros materiales. Para los países emergentes, entre los cuales se ubica Cuba, el uso de estas adiciones puzolánicas resultan una solución relativamente costosa, dado los altos precios de importación de estos materiales puzolánicos, de ahí la utilidad de usar las fuentes nacionales de puzolanas disponibles de probada reactividad, como sustituías parciales de los contenidos de Cemento Portland Ordinario (CPO) en las mezclas de hormigón, sin que se vean afectadas significativamente sus propiedades. El presente trabajo muestra la influencia del nivel de sustitución de los contenidos de Cemento Portland por adición mineral cal- puzolana, en combinación con superplastificante, en el comportamiento de la resistencia a la compresión y la durabilidad de un hormigón. Varios niveles de sustitución de CPO son evaluados, utilizando toba zeolítica como puzolana. Los resultados obtenidos corroboran la posibilidad del reemplazo de altos volúmenes de CPO por aglomerante cal-zeolita, sin que se afecten la resistencia a compresión requerida y su comportamiento ante la acción del ingreso del ion cloruro y la carbonatación. Abstract in english The international construction practice reports a remarkable use and development of high performance concretes, with excellent results in the durability properties, associated with a very dense cement matrix, defined from the use of high volumes of very fine minerals additions, such as, fly ash, sil [...] ica fume, metakaolin and other fine powders. For the developing countries, among others Cuba, the use of these pozzolanic additions are relatively expensive, given for the high import prices of these pozzolanic materials, thus, the utility of using the national available pozzolanic sources with proven reactivity, as a partial substitute of the Ordinary Portland Cement (OPC) contents in the concrete mixtures without its properties are affected. The present paper shows the results of the study on the influence of substitution level of Ordinary Portland Cement contents by lime - pozzolan binder in combination with chemical admixture, in the behavior of the compression strength and the durability properties of a concrete. Several levels of OPC substitution are evaluated, using zeolite as pozzolan. The results obtained prove the possibility to carry out the partial replacement of high volumes of OPC by lime - zeolite binder, without affecting the values of compression strength required and their behavior before action of the chloride ion penetration and the carbonation.

  1. COMPRESSION RESISTANCE AND SHEAR STRENGTH OF Guadua angustiolia CULMS AFTER DRILLING OF THE NODE DIAPHRAGM / Resistencia a la compresión y al corte de culmos de Guadua angustifolia después de la perforación del diafragma del nudo

    Scientific Electronic Library Online (English)

    Juan Carlos, Camargo García; Juan David, Suarez Franco.

    2014-01-01

    Full Text Available La preservación de culmos de guadua (Guadua angustifolia) es un proceso fundamental que contribuye a garantizar su calidad de estos cuando luego de ser cosechados son usados en distintas aplicaciones como muebles, artesanías y especialmente estructuras. El uso de boro y ácido bórico, es una de las p [...] rácticas más comunes para preparar soluciones preservantes. Para facilitar la absorción de la solución persevante durante la inmersión, el diafragma de los culmos es perforado. En este estudio, mediante un experimento factorial, se evaluó el posible efecto que puede tener la perforación del diafragma en la resistencia al corte y a la compresión de los culmos. Adicionalmente, su madurez fue incluida como otro factor, considerando dos formas de definirla: el método tradicional, a partir de características externas, y otro, mediante la selección de culmos marcados previamente (hace 4 años) al momento de haber emergido del suelo. Los análisis de varianza no mostraron ningún efecto o cambio significativo (p>0.05) en las propiedades mecánicas evaluadas, cuando se evaluaron culmos perforados y no perforados. No obstante, aquellos cuya madurez fue definida mediante el método tradicional mostraron en promedio menor resistencia al corte y a la compresión que los previamente marcados. Por otro lado, la humedad de las probetas mostró un efecto significativo (p Abstract in english The preservation of guadua (Guadua angustifolia) culms is an important process which affects their quality after harvesting and their subsequent utilization as a raw material in handicraft, furniture and construction. Boron and boric acid are frequently used in the preserving solution (PS). To ease [...] the adsorption the culm diaphragm is usually drilled before immersion in the PS. We performed a factorial experiment to determine the possible effects of drilling the culm diaphragm on compression and shear strength. Two measures of culm maturity were considered. The traditional measure is defined by the external features of the culms and another is based on the time since culm emergence. Variance analyses did not show any significant (p > 0.05) difference in mechanical properties when the diaphragm was drilled. Nevertheless, those culms with maturity defined using the traditional approach had significantly lower values of compression and shear strength. In addition, culms with higher moisture content were significantly stronger.

  2. Study of the compressive strength of concrete block prisms: stack and running bond / Estudo da resistência à compressão de prismas de blocos de concreto: juntas sobrepostas e amarradas

    Scientific Electronic Library Online (English)

    G., Mohamad; P.B., Lourenço; H. R., Roman.

    2011-08-01

    Full Text Available O principal objetivo deste trabalho é investigar o comportamento não linear de prismas de blocos de concreto a compressão, com ênfase na deformabilidade e modo de ruptura. Um total de dezoito (18) prismas com blocos sobrepostos foram testados, usando blocos vazados com uma única geometria e dois tra [...] ços de argamassa. Para investigar o efeito da junta vertical utilizaram-se dois meios blocos na junta intermediária dos prismas. Utilizou-se o programa comercial DIANA para simular em elementos finitos o comportamento da alvenaria estrutural. As simulações numéricas foram realizadas usando um elemento bidimensional de oito (8) nós e o estado biaxial de tensões do material foi modelado pela combinação das condições de Rankine e Drucker-Prager. Foram comparados os resultados numéricos e experimentais para validar a capacidade de prever as deformações e a carga última do conjunto. Pode se perceber pelos resultados que um modelo analítico não pode ser formulado sem um entendimento das interações entre o bloco e argamassa. Foi observado que a não linearidade da alvenaria correspondeu a um aumento nas deformações laterais devido à extensiva fissuração do material e a um progressivo aumento nas proporções entre a deformação lateral e axial; as fissuras nos prismas de três blocos construídas com argamassa forte foram verticais em ambos os lados; os prismas construídos com argamassa mais fraca tiveram um modo de ruptura por esmagamento e, também, fissuras verticais devido à concentração de tensões em alguns pontos; a presença da junta vertical nos prismas levou a uma fissura de separação entre o bloco do meio e a junta vertical de argamassa. Abstract in english The main goal of this work is to investigate the nonlinear behavior of concrete block masonry prisms under compression, with an emphasis in the prism deformability and the failure modes. A total of 18 stack-bonded prisms have been tested, using hollow blocks of a single geometry and two different mo [...] rtar types. To investigate the effect of vertical joints, the bond pattern - stack and running bond - in the prism was varied, by using half units. Finite element analysis of hollow masonry prisms was done utilizing a commercial non-linear finite element code DIANA. The numerical simulation were carried out using non-linear two dimensional 8-node elements and the biaxial stress state material was modeled by a combination of the yield conditions of Rankine and Drucker-Prager. The numerical and experimental results were compared to validate the ability to predict deformation and peak load. The results show that an analytical model cannot be formulated without understanding the interaction between block and mortar. It was observed that: the non-linearities of the masonry correspond to an increase in the lateral strain due to extensive cracking of the material and a progressive increase in the ratio between lateral and axial strains.; the cracks in the three block stacked prisms constructed with a stronger mortar were vertical on both sides; the prisms constructed with a weaker mortar had, as a consequence of localized crushing, also vertical cracks due to stress concentration at some points; the presence of a vertical joint in the prism led to the appearance of separation cracks between the middle block and the vertical mortar joint.

  3. Determining the mechanical strength of CO2-induced reaction zones in wellbore cement: is it worth it?

    Science.gov (United States)

    Hangx, Suzanne; Marcelis, Fons; van der Linden, Arjan; Liteanu, Emilia

    2015-04-01

    CO2 injection, either for long-term CO2 storage (CCS) or Enhanced Oil Recovery (EOR), strongly hinges on maintaining storage integrity. Injection and legacy wells penetrating the caprock pose one of the most likely points of leakage. In order to be able to predict the long-term integrity of such wellbores, it's important to understand their chemical, hydrological and mechanical behaviour, and how it may change due to CO2 exposure. Generally, in response to CO2/brine/cement interactions, a number of different reaction zones are observed, each with their own chemical, and hence mechanical, signature. To aid mechanical modelling efforts, assessing the risk of cement failure caused by stress and temperature changes, knowledge is required of the strength of each of these zones. We performed experiments on Class G Portland cement to investigate the chemical-mechanical coupling due to CO2-exposure. Batch reaction experiments, in the presence of CO2-rich brine, were performed under typical storage conditions (T = 65° C, PCO2 = 8 MPa) for various periods of time (1, 2, 3, 4, 5 and 6 months). After exposure, mechanical tests were performed on the observed reaction zones, using the so-called core scratching technique, to evaluate the unconfined compressive strength (UCS) as a function of exposure time. Chemical analyses (CT-imaging, SEM microscopy, EDX chemical analysis) showed the formation of three reaction zones, similarly to what has been observed in other studies. Measurements of the mechanical strength of these different zones showed highly variable results. Such variations have also been observed in other studies, using different measurement techniques. The large variability in strength measurements is most likely an inherent result of the heterogenic nature of cement, which affects the extent and location of reaction throughout the sample. This begs the question: is it worth studying the mechanical strength of reaction-induced zones in cement? Or will it suffice to take into account large uncertainties when modelling the mechanical behaviour of cement?

  4. Multiaxial strength and rupture behaviour of concrete

    International Nuclear Information System (INIS)

    Concrete quality Bn 350, Bn 450, Bn 550, was investigated with quartzite and calcite added materials. The following stress fields were investigated: biaxial compressive strength, triaxial compressive strength, biaxially one direction compression, the other direction tension, triaxially two directions under compressive stresses and the third direction under tensile stress. Deformation measurements were carried out: for biaxial compressive stress, for triaxial compressive stress, for uniaxial tension and uniaxial compressive stress, for uniaxial tension and biaxial compressive stresses. As has been reported before, concrete always fails on account of cleavage fractures. The fractures surfaces are located either facing the tension-free direction or, in the case of triaxial stress, in the direction of the least tension. (orig./LH)

  5. Non-linear model for compression tests on articular cartilage.

    Science.gov (United States)

    Grillo, Alfio; Guaily, Amr; Giverso, Chiara; Federico, Salvatore

    2015-07-01

    Hydrated soft tissues, such as articular cartilage, are often modeled as biphasic systems with individually incompressible solid and fluid phases, and biphasic models are employed to fit experimental data in order to determine the mechanical and hydraulic properties of the tissues. Two of the most common experimental setups are confined and unconfined compression. Analytical solutions exist for the unconfined case with the linear, isotropic, homogeneous model of articular cartilage, and for the confined case with the non-linear, isotropic, homogeneous model. The aim of this contribution is to provide an easily implementable numerical tool to determine a solution to the governing differential equations of (homogeneous and isotropic) unconfined and (inhomogeneous and isotropic) confined compression under large deformations. The large-deformation governing equations are reduced to equivalent diffusive equations, which are then solved by means of finite difference (FD) methods. The solution strategy proposed here could be used to generate benchmark tests for validating complex user-defined material models within finite element (FE) implementations, and for determining the tissue's mechanical and hydraulic properties from experimental data. PMID:25840005

  6. Three-dimensional conceptual model for the Hanford Site unconfined aquifer system: FY 1994 status report

    Energy Technology Data Exchange (ETDEWEB)

    Thorne, P.D.; Chamness, M.A.; Vermeul, V.R.; Macdonald, Q.C.; Schubert, S.E.

    1994-11-01

    This report documents work conducted during the fiscal year 1994 to development an improved three-dimensional conceptual model of ground-water flow in the unconfined aquifer system across the Hanford Site Ground-Water Surveillance Project, which is managed by Pacific Northwest Laboratory. The main objective of the ongoing effort to develop an improved conceptual model of ground-water flow is to provide the basis for improved numerical report models that will be capable of accurately predicting the movement of radioactive and chemical contaminant plumes in the aquifer beneath Hanford. More accurate ground-water flow models will also be useful in assessing the impacts of changes in facilities and operations. For example, decreasing volumes of operational waste-water discharge are resulting in a declining water table in parts of the unconfined aquifer. In addition to supporting numerical modeling, the conceptual model also provides a qualitative understanding of the movement of ground water and contaminants in the aquifer.

  7. Summary and evaluation of available hydraulic property data for the Hanford Site unconfined aquifer system

    International Nuclear Information System (INIS)

    Improving the hydrologic characterization of the Hanford Site unconfined aquifer system is one of the objectives of the Hanford Site Ground-Water Surveillance Project. To help meet this objective, hydraulic property data available for the aquifer have been compiled, mainly from reports published over the past 40 years. Most of the available hydraulic property estimates are based on constant-rate pumping tests of wells. Slug tests have also been conducted at some wells and analyzed to determine hydraulic properties. Other methods that have been used to estimate hydraulic properties of the unconfined aquifer are observations of water-level changes in response to river stage, analysis of ground-water mound formation, tracer tests, and inverse groundwater flow models

  8. Robust evidence for random fractal scaling of ground water levels in unconfined aquifers

    OpenAIRE

    Little, Max A.; Bloomfield, John P.

    2010-01-01

    This study introduces new approaches to improve the statistical robustness of techniques for quantifying the fractal scaling of groundwater levels, and uses these techniques to investigate scaling of groundwater levels from a consolidated permeable carbonate aquifer. Six groundwater level time series and an associated river stage time series from the unconfined Chalk aquifer (a dual-porosity, fractured limestone aquifer) in the Pang–Lambourn catchment, UK, have been analysed. Surrogate data o...

  9. Measuring the Mechanical Strength and Hardsetting Phenomenon in Selected Soils of Hamadan Province

    Directory of Open Access Journals (Sweden)

    E. Farahani

    2012-10-01

    Full Text Available Hardsetting phenomenon is an indicator of poor soil physical quality. Hardsetting soils are soils with high rate of mechanical strength increase upon drying and are hardened and/or compacted when dry out. It is difficult to till such soils. Hardsetting soils have additional limitations such as poor aeration at wet conditions, low infiltrability and high runoff and erosion. Most of Iran soils have low organic matter content and it is expected that hardsetting phenomenon occurs in some of these soils. This study was conducted to investigate the hardsetting phenomenon on 9 soil series collected from Hamadan province. Three types of mechanical strength consisting tensile strength (ITS, unconfined compressive strength (UCS, and penetration resistance (PR were measured on the repacked soil samples prepared in the lab. The ITS, UCS and PR tests were done on the soil cores which had been prepared at bulk density (BD equal to 90% of critical BD for root growth (0.9BDcritical. The effects of intrinsic properties on the hardsetting phenomenon were studied, too. Based on the suggested definition in “International Symposium on Sealing, Crusting and Hardsetting Soils” to International Union of Soil Science, in which a hardsetting soil has air-dry tensile strength ? 90 kPa, one soil (medium-textured out of the studied soils showed the hardsetting phenomenon at 0.9BDcritical. It might be concluded that medium-textured soils are more susceptible to hardsetting. For all of the studied soils, the ITS increased with the increase in clay content. The increasing impacts of clay and carbonate contents were also observed for the UCS and PR, respectively. Calcium carbonate could act as a cementing agent in between the soil particles and brings about the soil susceptibility to hardsetting. Moreover, the decreasing trend of all soil mechanical strengths was observed with water content increase. Slope (b of the exponential model (fitted to the soil mechanical strength characteristic curve, as an index of hardsetting, had positive correlation with the sand content and negative correlation with the silt content. Overall, texture and calcium carbonate content are major and effective properties in terms of hardsetting phenomenon in Hamadan soils.

  10. Strength Measurements of Archive K Basin Sludge Using a Soil Penetrometer

    International Nuclear Information System (INIS)

    Spent fuel radioactive sludge present in the K East and K West spent nuclear fuel storage basins now resides in the KW Basin in six large underwater engineered containers. The sludge will be dispositioned in two phases under the Sludge Treatment Project: (1) hydraulic retrieval into sludge transport and storage containers (STSCs) and transport to interim storage in Central Plateau and (2) retrieval from the STSCs, treatment, and packaging for shipment to the Waste Isolation Pilot Plant. In the years the STSCs are stored, sludge strength is expected to increase through chemical reaction, intergrowth of sludge crystals, and compaction and dewatering by settling. Increased sludge strength can impact the type and operation of the retrieval equipment needed prior to final sludge treatment and packaging. It is important to determine whether water jetting, planned for sludge retrieval from STSCs, will be effective. Shear strength is a property known to correlate with the effectiveness of water jetting. Accordingly, the unconfined compressive strengths (UCS) of archive K Basin sludge samples and sludge blends were measured using a pocket penetrometer modified for hot cell use. Based on known correlations, UCS values can be converted to shear strengths. Twenty-six sludge samples, stored in hot cells for a number of years since last being disturbed, were identified as potential candidates for UCS measurement and valid UCS measurements were made for twelve, each of which was found as moist or water-immersed solids at least 1/2-inch deep. Ten of the twelve samples were relatively weak, having consistencies described as 'very soft' to 'soft'. Two of the twelve samples, KE Pit and KC-4 P250, were strong with 'very stiff' and 'stiff' consistencies described, respectively, as 'can be indented by a thumb nail' or 'can be indented by thumb'. Both of these sludge samples are composites collected from KE Basin floor and Weasel Pit locations. Despite both strong sludges having relatively high iron concentrations, attribution of their high strengths to this factor could not be made with confidence as other measured sludge samples, also from the KE Basin floor and of high iron concentration, were relatively weak. The observed UCS and shear strengths for the two strong sludges were greater than observed in any prior testing of K Basin sludge except for sludge processed at 185 C under hydrothermal conditions.

  11. Strength Measurements of Archive K Basin Sludge Using a Soil Penetrometer

    Energy Technology Data Exchange (ETDEWEB)

    Delegard, Calvin H.; Schmidt, Andrew J.; Chenault, Jeffrey W.

    2011-12-06

    Spent fuel radioactive sludge present in the K East and K West spent nuclear fuel storage basins now resides in the KW Basin in six large underwater engineered containers. The sludge will be dispositioned in two phases under the Sludge Treatment Project: (1) hydraulic retrieval into sludge transport and storage containers (STSCs) and transport to interim storage in Central Plateau and (2) retrieval from the STSCs, treatment, and packaging for shipment to the Waste Isolation Pilot Plant. In the years the STSCs are stored, sludge strength is expected to increase through chemical reaction, intergrowth of sludge crystals, and compaction and dewatering by settling. Increased sludge strength can impact the type and operation of the retrieval equipment needed prior to final sludge treatment and packaging. It is important to determine whether water jetting, planned for sludge retrieval from STSCs, will be effective. Shear strength is a property known to correlate with the effectiveness of water jetting. Accordingly, the unconfined compressive strengths (UCS) of archive K Basin sludge samples and sludge blends were measured using a pocket penetrometer modified for hot cell use. Based on known correlations, UCS values can be converted to shear strengths. Twenty-six sludge samples, stored in hot cells for a number of years since last being disturbed, were identified as potential candidates for UCS measurement and valid UCS measurements were made for twelve, each of which was found as moist or water-immersed solids at least 1/2-inch deep. Ten of the twelve samples were relatively weak, having consistencies described as 'very soft' to 'soft'. Two of the twelve samples, KE Pit and KC-4 P250, were strong with 'very stiff' and 'stiff' consistencies described, respectively, as 'can be indented by a thumb nail' or 'can be indented by thumb'. Both of these sludge samples are composites collected from KE Basin floor and Weasel Pit locations. Despite both strong sludges having relatively high iron concentrations, attribution of their high strengths to this factor could not be made with confidence as other measured sludge samples, also from the KE Basin floor and of high iron concentration, were relatively weak. The observed UCS and shear strengths for the two strong sludges were greater than observed in any prior testing of K Basin sludge except for sludge processed at 185 C under hydrothermal conditions.

  12. Strength Training

    Science.gov (United States)

    ... big difference between strength training, powerlifting, and competitive bodybuilding! Strength training uses resistance methods like free weights, ... a person can lift at one time. Competitive bodybuilding involves evaluating muscle definition and symmetry, as well ...

  13. Uso de las Redes Neuronales Artificiales en el Modelado del Ensayo de Resistencia a Compresión de Concreto de Construcción según la Norma ASTM C39/C 39M / Use of Artificial Neural Networks for Modeling of the Test of Compressive strength of Construction Concrete According to the Standard ASTM C39/C 39 M

    Scientific Electronic Library Online (English)

    Luis, Acuña; Ana V, Torre; Isabel, Moromi; Francisco, García.

    Full Text Available Se proponen dos modelos de redes neuronales artificiales para la predicción del resultado del ensayo a compresión de un concreto de construcción tras el periodo de curado a partir de datos de fabricación fácilmente medibles. La resistencia a compresión del concreto es uno de los parámetros más impor [...] tantes en su control de calidad. Sin embargo, estos ensayos se realizan tras un periodo de curado que hace que los resultados disten de ser inmediatos a la fabricación del producto. Por lo tanto, se propone un modelo matemático fiable para obtener los resultados del ensayo en forma inmediata. Los modelos propuestos presentan coeficientes de correlación mayores a 0.9 y permiten reducir considerablemente el tiempo en obtener los resultados de la resistencia a compresión. Abstract in english Two artificial neural network models for predicting the results of compressive strength test of a construction concrete after the curing period are proposed. The compressive strength of concrete is one of the most important variables in its quality control. However, these tests are carried out after [...] a period of curing so results of the test are not immediately available. Therefore a reliable mathematical model that would obtain the test results immediately after the curing time These models present correlation coefficients higher than 0.9 and allow reducing the time to obtain the results of compressive strength tests.

  14. An Experimental Study of Unconfined Hydrogen/Oxygen and Hydrogen/Air Explosions

    Science.gov (United States)

    Richardson, Erin; Skinner, Troy; Blackwood, James; Hays, Michael; Bangham, Mike; Jackson, Austin

    2014-01-01

    Development tests are being conducted to characterize unconfined Hydrogen/air and Hydrogen/Oxygen blast characteristics. Most of the existing experiments for these types of explosions address contained explosions, like shock tubes. Therefore, the Hydrogen Unconfined Combustion Test Apparatus (HUCTA) has been developed as a gaseous combustion test device for determining the relationship between overpressure, impulse, and flame speed at various mixture ratios for unconfined reactions of hydrogen/oxygen and hydrogen/air. The system consists of a central platform plumbed to inject and mix component gasses into an attached translucent bag or balloon while monitoring hydrogen concentration. All tests are ignited with a spark with plans to introduce higher energy ignition sources in the future. Surrounding the platform are 9 blast pressure "Pencil" probes. Two high-speed cameras are used to observe flame speed within the combustion zone. The entire system is raised approx. 6 feet off the ground to remove any ground reflection from the measurements. As of this writing greater than 175 tests have been performed and include Design of Experiments test sets. Many of these early tests have used bags or balloons between approx. 340L and approx. 1850L to quantify the effect of gaseous mixture ratio on the properties of interest. All data acquisition is synchronized between the high-speed cameras, the probes, and the ignition system to observe flame and shock propagation. Successful attempts have been made to couple the pressure profile with the progress of the flame front within the combustion zone by placing a probe within the bag. Overpressure and impulse data obtained from these tests are used to anchor engineering analysis tools, CFD models and in the development of blast and fragment acceleration models.

  15. Leachability and strength of kaolin stabilized with cement and rubber

    Directory of Open Access Journals (Sweden)

    Meei-Hoan Ho

    2011-07-01

    Full Text Available Yearly, the disposal of used tyres is a major environmental problem for countries all over the world. This causes environmental hazards such as uncontrolled fire, consume landfill space, breeding ground for mosquitoes and contaminating the soil and vegetation. Hence, urgent steps were identified to produce new methods of recycling the waste tyres to solve this hazard. This study reviews the feasibility of using waste tyres in the form of rubber chips with cement to stabilize soft clay and the effect to the environment. The focus of this study was mainly the strength and leachability characteristics of kaolin as base clay, admixed with cement as the binder and rubber chips as an additive. Leaching test is used to evaluate the performance of cementitious materials for stabilization and solidification (S & S of hazardous materials such as waste or contaminated soil. In this study, cylindrical stabilized clay specimens were prepared with various rubber chips contents and cement, and then aged for 28 days. Cylindrical specimens were then subjected to unconfined compressive strength test (using Geocomp LoadTrac II and the specimens were later dried in oven at 105° before tested for leaching tests. These leaching methods are Acid Neutralization Capacity Test (ANC and Synthetic Precipitation Leaching Procedure (SPLP. The solidified samples were checked on six different heavy metals, namely copper, chromium, cadmium, arsenic, zinc and plumbum. Analysis was carried out by relating the effects of 0, 2 or 4 % cement as well as 0, 5, 10 and 15 % rubber chips addition to the base clay and its leachability. As observed, the curing of specimen for 28 days was in a range of 66.24 to 249.4 kPa. Specimen with 4 % cement is able to produce ANC9 of about 0.13 meq HNO3/g specimen. However specimen with 0 % and 2 % cement for different rubberchips content shows that the specimen do not have the capacity to neutralize acid at pH 9. Therefore, more cement (> 4 % is needed to achieve ANC9. SPLP results showed that all six different heavy metals tested do not exceed the approved limit for drinking water by World Health Organization (WHO, United States Environmental Protection Agency (USEPA and Ministry of Health in Malaysia.

  16. IMPACT STRENGTH OF GLASS AND GLASS CERAMIC

    International Nuclear Information System (INIS)

    Strength of glass and glass ceramic was measured with a bar impact technique. High-speed movies show regions of tensile and compressive failure. The borosilicate glass had a compressive strength of at least 2.2 GPa, and the glass ceramic at least 4 GPa. However, the BSG was much stronger in tension than GC. In ballistic tests, the BSG was the superior armor.

  17. Basin-scale conceptual groundwater flow model for an unconfined and confined thick carbonate region

    Science.gov (United States)

    Mádl-Sz?nyi, Judit; Tóth, Ádám

    2015-06-01

    Application of the gravity-driven regional groundwater flow (GDRGF) concept to the hydrogeologically complex thick carbonate system of the Transdanubian Range (TR), Hungary, is justified based on the principle of hydraulic continuity. The GDRGF concept informs about basin hydraulics and groundwater as a geologic agent. It became obvious that the effect of heterogeneity and anisotropy on the flow pattern could be derived from hydraulic reactions of the aquifer system. The topography and heat as driving forces were examined by numerical simulations of flow and heat transport. Evaluation of groups of springs, in terms of related discharge phenomena and regional chloride distribution, reveals the dominance of topography-driven flow when considering flow and related chemical and temperature patterns. Moreover, heat accumulation beneath the confined part of the system also influences these patterns. The presence of cold, lukewarm and thermal springs and related wetlands, creeks, mineral precipitates, and epigenic and hypogenic caves validates the existence of GDRGF in the system. Vice versa, groups of springs reflect rock-water interaction and advective heat transport and inform about basin hydraulics. Based on these findings, a generalized conceptual GDRGF model is proposed for an unconfined and confined carbonate region. An interface was revealed close to the margin of the unconfined and confined carbonates, determined by the GDRGF and freshwater and basinal fluids involved. The application of this model provides a background to interpret manifestations of flowing groundwater in thick carbonates generally, including porosity enlargement and hydrocarbon and heat accumulation.

  18. Influence of Phreatic Conduit Floods on Matrix Storage in Unconfined Karst

    Science.gov (United States)

    Wilson, J. L.; Koski, K.

    2009-12-01

    Conduits from cm’s to m’s in effective diameter are common features in some karst aquifers, providing most of the flow capacity, but relatively little of the storage. Unconfined karst aquifers have a water table and no caprock. Phreatic conduits are completely submerged below the water table. These conditions are found, for example, in the unconfined Floridan aquifer of the United States and on the Yucatan Peninsula of Mexico. Karst conduits respond quickly to precipitation events, propagating floods that might originate with a sinking stream and eventually discharge to a spring. As the flood passes, water moves from the pressurized conduit to the surrounding rock matrix where it is stored; then, as the flood passes some of the stored flood water returns to the conduit. The amount, pattern and nature of storage is strongly influenced by the presence of an overlying water table and natural recharge. We investigate this influence using mathematical models, with implications for speleogenesis, contaminant sequestration, and aqueous geochemistry.

  19. Basin-scale conceptual groundwater flow model for an unconfined and confined thick carbonate region

    Science.gov (United States)

    Mádl-Sz?nyi, Judit; Tóth, Ádám

    2015-11-01

    Application of the gravity-driven regional groundwater flow (GDRGF) concept to the hydrogeologically complex thick carbonate system of the Transdanubian Range (TR), Hungary, is justified based on the principle of hydraulic continuity. The GDRGF concept informs about basin hydraulics and groundwater as a geologic agent. It became obvious that the effect of heterogeneity and anisotropy on the flow pattern could be derived from hydraulic reactions of the aquifer system. The topography and heat as driving forces were examined by numerical simulations of flow and heat transport. Evaluation of groups of springs, in terms of related discharge phenomena and regional chloride distribution, reveals the dominance of topography-driven flow when considering flow and related chemical and temperature patterns. Moreover, heat accumulation beneath the confined part of the system also influences these patterns. The presence of cold, lukewarm and thermal springs and related wetlands, creeks, mineral precipitates, and epigenic and hypogenic caves validates the existence of GDRGF in the system. Vice versa, groups of springs reflect rock-water interaction and advective heat transport and inform about basin hydraulics. Based on these findings, a generalized conceptual GDRGF model is proposed for an unconfined and confined carbonate region. An interface was revealed close to the margin of the unconfined and confined carbonates, determined by the GDRGF and freshwater and basinal fluids involved. The application of this model provides a background to interpret manifestations of flowing groundwater in thick carbonates generally, including porosity enlargement and hydrocarbon and heat accumulation.

  20. Approaches to the simulation of unconfined flow and perched groundwater flow in MODFLOW

    Science.gov (United States)

    Bedekar, Vivek; Niswonger, Richard G.; Kipp, Kenneth; Panday, Sorab; Tonkin, Matthew

    2012-01-01

    Various approaches have been proposed to manage the nonlinearities associated with the unconfined flow equation and to simulate perched groundwater conditions using the MODFLOW family of codes. The approaches comprise a variety of numerical techniques to prevent dry cells from becoming inactive and to achieve a stable solution focused on formulations of the unconfined, partially-saturated, groundwater flow equation. Keeping dry cells active avoids a discontinuous head solution which in turn improves the effectiveness of parameter estimation software that relies on continuous derivatives. Most approaches implement an upstream weighting of intercell conductance and Newton-Raphson linearization to obtain robust convergence. In this study, several published approaches were implemented in a stepwise manner into MODFLOW for comparative analysis. First, a comparative analysis of the methods is presented using synthetic examples that create convergence issues or difficulty in handling perched conditions with the more common dry-cell simulation capabilities of MODFLOW. Next, a field-scale three-dimensional simulation is presented to examine the stability and performance of the discussed approaches in larger, practical, simulation settings.

  1. A correction for Dupuit-Forchheimer interface flow models of seawater intrusion in unconfined coastal aquifers

    Science.gov (United States)

    Koussis, Antonis D.; Mazi, Katerina; Riou, Fabien; Destouni, Georgia

    2015-06-01

    Interface flow models that use the Dupuit-Forchheimer (DF) approximation for assessing the freshwater lens and the seawater intrusion in coastal aquifers lack representation of the gap through which fresh groundwater discharges to the sea. In these models, the interface outcrops unrealistically at the same point as the free surface, is too shallow and intersects the aquifer base too far inland, thus overestimating an intruding seawater front. To correct this shortcoming of DF-type interface solutions for unconfined aquifers, we here adapt the outflow gap estimate of an analytical 2-D interface solution for infinitely thick aquifers to fit the 50%-salinity contour of variable-density solutions for finite-depth aquifers. We further improve the accuracy of the interface toe location predicted with depth-integrated DF interface solutions by ?20% (relative to the 50%-salinity contour of variable-density solutions) by combining the outflow-gap adjusted aquifer depth at the sea with a transverse-dispersion adjusted density ratio (Pool and Carrera, 2011), appropriately modified for unconfined flow. The effectiveness of the combined correction is exemplified for two regional Mediterranean aquifers, the Israel Coastal and Nile Delta aquifers.

  2. Effet de la combinaison de la chaux et de la pouzzolane naturelle sur le compactage et la résistance des sols mous argileux Effect of the combination of lime and natural pozzolana on the compaction and strength of soft clayey soils

    Directory of Open Access Journals (Sweden)

    Kenai S.

    2012-09-01

    Full Text Available La stabilisation des sols mous a été pratiquée longtemps en mélangeant des ajouts, tels que le ciment, la chaux et les cendres volantes au sol pour augmenter sa résistance. Cependant, il y a un manque d’investigations sur l’utilisation de la pouzzolane naturelle seule ou combinée avec la chaux pour les applications d’amélioration des sols. Un programme expérimental a été entrepris pour étudier l’effet de la chaux, la pouzzolane naturelle ou leur combinaison sur les caractéristiques géotechniques des sols mous. La chaux ou la pouzzolane naturelle ont été ajoutées aux sols par des teneurs de 0-10% et 0-20% respectivement. Les échantillons préparés ont été soumis aux essais de compactage et de résistance à la compression non confinée. Les échantillons ont subis des périodes de cure de 1, 7, 28 et 90 jours après quoi ils ont été soumis aux essais de la résistance à la compression non confinée. Basé sur les résultats favorables obtenus, ilpeut être conclu que les sols mous argileux peuvent être stabilisés avec succès par l’action combinée de la chaux et de la pouzzolane naturelle. Puisque la pouzzolane naturelle est beaucoup moins chère que la chaux, l’addition de la pouzzolane naturelle dans le mélange chaux-sol peut en particulier devenir attirante et avoir comme conséquence une réduction des coûts de la construction. Soft soil stabilization has been practiced for quite some time by mixing additives, such as cement, lime and fly ash to the soil to increase its strength. However, there is a lack of investigations on the use of natural pozzolana alone or combined with lime for ground improvement applications. An experimental program was undertaken to study the effect of using lime, natural pozzolana or a combination of both on the geotechnical characteristics of soft soils. Lime or natural pozzolana was added to soft soils at ranges of 0-10% and 0-20%, respectively. In addition, combinations of limenatural pozzolana were added to soft soils at the same ranges. Test specimens were subjected to compaction tests and unconfined compression tests. Specimens were cured for 1, 7, 28 and 90 days after which they were tested for unconfined compression tests. Based on the favourable results obtained, it can be concluded that the soft soils can be successfully stabilized by the combined action of lime and natural pozzolana. Since natural pozzolana is much cheaper than lime, the addition of natural pozzolana in limesoil mix may particularly become attractive and can result in cost reduction of construction.

  3. Investigating Conversion of Endplate Chondrocytes Induced by Intermittent Cyclic Mechanical Unconfined Compression in Three-Dimensional Cultures

    OpenAIRE

    Xu, H.G.; Zhang, W; Zheng, Q.; Y.F. Yu; Deng, L.F.; H Wang; LIU, P; Zhang, M.

    2014-01-01

    Mechanical stimulation is known to regulate the calcification of endplate chondrocytes. The ANK protein has a strong influence on anti-calcification by transports intracellular inorganic pyrophosphate (PPi) to the extracellular. It is known that TGF-?1 is able to induced Ank gene expression and protect chondrocyte calcification. Intermittent cyclic mechanical tension (ICMT) could induce calcification of endplate chondrocytes by decrease the expression of Ank gene. In this study, we investigat...

  4. Material properties in unconfined compression of human nucleus pulposus, injectable hyaluronic acid-based hydrogels and tissue engineering scaffolds

    OpenAIRE

    Cloyd, Jordan M.; Malhotra, Neil R.; Weng, Lihui; Chen, Weiliam; MAUCK, ROBERT L.; Elliott, Dawn M.

    2007-01-01

    Surgical treatment for lower back pain related to degenerative disc disease commonly includes discectomy and spinal fusion. While surgical intervention may provide short-term pain relief, it results in altered biomechanics of the spine and may lead to further degenerative changes in adjacent segments. One non-fusion technique currently being investigated is nucleus pulposus (NP) support via either an injectable hydrogel or tissue engineered construct. A major challenge for either approach is ...

  5. STRENGTH OF NANOMODIFIED HIGH-STRENGTH LIGHTWEIGHT CONCRETES

    Directory of Open Access Journals (Sweden)

    NOZEMT?EV Alexandr Sergeevich

    2013-02-01

    Full Text Available The paper presents the results of research aimed at development of nanomodified high-strength lightweight concrete for construction. The developed concretes are of low average density and high ultimate compressive strength. It is shown that to produce this type of concrete one need to use hollow glass and aluminosilicate microspheres. To increase the durability of adhesion between cement stone and fine filler the authors offer to use complex nanodimensinal modifier based on iron hydroxide sol and silica sol as a surface nanomodifier for hollow microspheres. It is hypothesized that the proposed modifier has complex effect on the activity of the cement hydration and, at the same time increases bond strength between filler and cement-mineral matrix. The compositions for energy-efficient nanomodified high-strength lightweight concrete which density is 1300…1500 kg/m³ and compressive strength is 40…65 MPa have been developed. The approaches to the design of high-strength lightweight concrete with density of less than 2000 kg/m³ are formulated. It is noted that the proposed concretes possess dense homogeneous structure and moderate mobility. Thus, they allow processing by vibration during production. The economic and practical implications for realization of high-strength lightweight concrete in industrial production have been justified.

  6. Strength Testing.

    Science.gov (United States)

    Londeree, Ben R.

    1981-01-01

    Postural deviations resulting from strength and flexibility imbalances include swayback, scoliosis, and rounded shoulders. Screening tests are one method for identifying strength problems. Tests for the evaluation of postural problems are described, and exercises are presented for the strengthening of muscles. (JN)

  7. Influência da utilização de procedimentos não padronizados de ensaio para a determinação experimental da resistência à compressão simples e do módulo estático de elasticidade do cimento Portland / Influence of non standard test procedures for determination of compressive strength and static modulus of elasticity of Portland cement

    Scientific Electronic Library Online (English)

    Jacinto Manuel Antunes de, Almeida; Bruno do Vale, Silva; Josué Argenta, Chies; Josiane, Gasperin; Luiz Carlos Pinto da Silva, Filho.

    2015-06-01

    Full Text Available A resistência à compressão é um dos parâmetros fundamentais usados para controle e caracterização do cimento. O ensaio padrão para determinação da resistência à compressão simples do cimento Portland, normatizado pela NBR 7215 (1), especifica o uso de areia com granulometria determinada e estabelece [...] procedimentos de mistura rigorosos na preparação dos corpos de prova. Sabe-se que, nem sempre, os procedimentos padrão são rigorosamente seguidos, seja devido a fatores relacionados com competência técnica ou pela simplificação da norma, entre outros fatores. O objetivo principal deste trabalho foi avaliar a influência de determinadas simplificações dos procedimentos padrão de ensaio na determinação experimental da resistência à compressão simples do cimento Portland. Foram testados diferentes procedimentos de mistura e utilizados diferentes tipos de agregado miúdo, especificamente, areia média comum ou com granulometria controlada, tomando como referência a denominada areia do Tietê. Foram utilizadas duas amostras de cimento CPV-ARI, provenientes de fabricantes distintos. Para todas as combinações foram realizados ensaios de resistência à compressão e módulo estático de elasticidade nas idades de 1, 3, 7 e 28 dias. Foi efetuada uma análise de variância (ANOVA) para avaliar se as variáveis estudadas geravam diferenças estatisticamente significativas nos resultados experimentais. Foi possível concluir que, de forma geral, a moldagem simplificada não influenciou significativamente a resistência à compressão simples nem o módulo estático de elasticidade do cimento Portland. Por outro lado, o tipo de agregado miúdo utilizado influenciou significativamente a resistência à compressão, mas não impactou o módulo de elasticidade das amostras. Abstract in english The compressive strength is one of the basic parameters to control and characterization of cement. According to the NBR 7215 (1), the standard test procedure for determination of compressive strength of cement specifies the use of sand with a specific gradation and establishes specific rules for the [...] preparation of the standard mixture of mortar, used to manufacture the test specimens. It is known that these recommendations are not always followed when testing. In the context of the present study, we aimed to investigate the influence of some deviations from the standard procedure in the results of compressive strength and modulus of elasticity of mortar. We've tested a simplified mixing procedure and the use of average sand or with controlled gradation, taking as reference the so-called sand from Tietê. We've also used two samples of CPV-ARI cement from different manufacturers. For all combinations, tests were performed to determine the compressive strength and static modulus of elasticity of mortar at 1, 3, 7 and 28 days of age. An analysis of variance (ANOVA) was performed to assess whether the variables generated significant differences. The results show that the simplified mixing procedure didn't affect the compressive strength neither the modulus of elasticity of Portland cement. The different types of sand tested only affected the compressive strength of Portland cement.

  8. Biosynthetic response of cartilage explants to dynamic compression.

    Science.gov (United States)

    Sah, R L; Kim, Y J; Doong, J Y; Grodzinsky, A J; Plaas, A H; Sandy, J D

    1989-01-01

    The biosynthetic response of calf articular cartilage explants to dynamic compression was examined over a wide range of amplitudes, waveforms, and frequencies. Glycosaminoglycan synthesis was assessed by 35S-sulfate incorporation, and amino acid uptake and protein synthesis were assessed by 3H-proline incorporation. Two culture chambers were designed to allow uniaxial radially unconfined compression and mechanical testing of cartilage disks: one chamber was used inside a standard incubator; the other was used with a mechanical spectrometer and allowed load and displacement to be monitored during compression. Dynamic stiffness measurements of 3-mm diameter disks identified a characteristic frequency [0.001 Hz (cycles/sec)] that separated low- and high-frequency regimes in which different flow and deformation phenomena predominated; e.g., at 0.0001-0.0001 Hz, significant fluid was exuded from cartilage disks, whereas at 0.01-1 Hz, hydrostratic pressure increased within disks. At the higher frequencies, oscillatory strains of only approximately 1-5% stimulated 3H-proline and 35S-sulfate incorporation by approximately 20-40%. In contrast, at the lower frequencies (a) compressions of less than 5% had no effect, consistent with the dosimetry of biosynthetic inhibition by static compression (approximately 25% compression caused a approximately 20% inhibition of radiolabel incorporation), and (b) higher amplitudes (cycling between disk thicknesses of 1.25 and 0.88-1.00 mm) stimulated 3S-sulfate incorporation by approximately 20-40%, consistent with the kinetics of response to a single 2-h compression and release. None of the compression protocols was associated with detectable alterations in (e.g., compression-induced depletion of) total glycosaminoglycan content. This study provides a framework for identifying both the physical and biological mechanisms by which dynamic compression can modulate chondrocyte biosynthesis. In addition, the culture and compression methodology potentially allows in vitro evaluation of clinical strategies of continuous passive motion therapy to stimulate cartilage remodeling. PMID:2760736

  9. Strength properties of concrete at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Freskakis, G.N.; Burrow, R.C.; Debbas, E.B.

    1979-01-01

    A study is presented concerning the compressive strength, modulus of elasticity, and stress-strain relationships of concrete at elevated temperatures. A review of published results provides information for the development of upper and lower bound relationships for compressive strength and the modulus of elasticity and establishes exposure conditions for a lower bound thermal response. The relationships developed from the literature review are confirmed by the results of a verification test program. The strength and elasticity relationships provide a basis for the development of design stress-strain curves for concrete exposed to elevated temperatures.

  10. In situ rock strength and far field stress in the Nankai accretionary complex: Integration of downhole data from multiple wells

    Science.gov (United States)

    Huffman, K. A.; Saffer, D. M.

    2014-12-01

    Knowing the magnitude of tectonic stress and rock strength at seismically active margins is important towards understanding fault strength and failure mechanics, yet both are difficult to measure in situ. Recent work at subduction margins, including Integrated Ocean Drilling Program (IODP) Nankai Trough Subduction Zone Experiment (NanTroSEIZE) drillsites, uses the width of compressional wellbore breakouts (BO), which depends on far field stress conditions, rock strength, and borehole annular pressure (APRS), to estimate the magnitude of horizontal principal stresses (SHmax and Shmin); estimates are problematic due to uncertainty in rock strength (unconfined compressive strength/UCS- for which direct measurements are scarce) and rheology that govern stress distribution at the wellbore. We conduct a novel case study at IODP Site C0002, where a hole was drilled twice with different boundary conditions, providing an opportunity to define in situ stress and strength from field data. Site C0002 is the main deep riser borehole for NanTroSEIZE, located near the seaward edge of the Kumano Basin above the seismogenic plate boundary, ~30 km from the trench. Several boreholes were drilled at the site. During IODP Expedition 314 in 2007, Hole C0002A was drilled with a suite of logging while drilling (LWD) tools to 1401 mbsf in a riserless mode. Hole C0002F, ~70 m away, was drilled to 862 mbsf in riserless mode during Exp. 326 in 2010 and deepened to 2005 mbsf in a riser mode during Expedition 338 in 2012-2013. Increased APRS achieved by riser drilling stabilizes the borehole and suppresses BO, consistent with resistivity imaging data from Exp. 314 that document well-developed, continuous BO throughout the borehole, and data from Expedition 338 indicating few BO. We use a semi-Newtonian approach to solve for stress and UCS consistent with the observed BO width and measured APRS in the two holes over the interval from 862-2005 mbsf. Effective SHmax ranges from ~10-30 MPa and indicate a strike-slip or thrust regime. Our results indicate UCS is higher than predicted by empirical relations and a small suite of laboratory tests by as much as 20 MPa. This apparent discrepancy may indicate that the failure criterion, or assumed distribution of stresses around the wellbore in analyses of far field stress, may not be appropriate in this setting.

  11. Strength of Ship Plates under Combined Loading

    DEFF Research Database (Denmark)

    Cui, W.; Wang, Y.; Pedersen, Preben Terndrup

    2002-01-01

    Strength of ship plates plays a significant role in the ultimate strength analysis of ship structures. In recent years several authors have proposed simplified analytical methods to calculate the ultimate strength of unstiffened plates. The majority of these investigations deal with plates subjected to longitudinal compression only. For real ship structural plating, the most general loading case is a combination of longitudinal stress, transverse stress, shear stress and lateral pressure. In thi...

  12. Strength of ship plates under combined loading

    DEFF Research Database (Denmark)

    Cui, Weiching; Wang, Yongjun; Pedersen, Preben Terndrup

    2000-01-01

    Strength of ship plates plays a significant role for the ultimate strength analysis of ship structures. In recent years several authors have proposed simplified methods to calculate the ultimate strength of unstiffened plates. The majority of these investigations deal with plates subjected to longitudinal compression only. For real ship structural plating, the most general loading case is a combination of longitudinal stress, transverse stress, shear stress and lateral pressure. In this paper, a...

  13. Investigation of strength properties of freshwater ice

    Directory of Open Access Journals (Sweden)

    Bragov A.

    2015-01-01

    Full Text Available A study of the strength and deformation properties of freshwater ice under compression, tension and shear in a wide range of strain rates (10?4 ? 3 ? 103?s?1 and temperatures of ? 5??C, ? 20??C, ? 40??C and ? 60??C was performed. Static stress-strain curves of ice under compression were obtained on which the identified strength properties of ice as well as compressive modulus. To determine the mechanical properties of ice at high-speed loading the Kolsky method was used with various embodiments of split Hopkinson bar. The deformation curves were obtained at various loading conditions. Thereon breaking points were defined as well as their dependence on the strain rate and temperature. Also static and dynamic strength properties of ice at splitting and circular shear were defined. Increase in the dynamic strength properties upon the static ones for all loading conditions was marked.

  14. Investigation of strength properties of freshwater ice

    Science.gov (United States)

    Bragov, A.; Igumnov, L.; Konstantinov, A.; Lomunov, A.; Filippov, A.; Shmotin, Yu.; Didenko, R.; Krundaeva, A.

    2015-09-01

    A study of the strength and deformation properties of freshwater ice under compression, tension and shear in a wide range of strain rates (10-4 - 3 ? 103 s-1) and temperatures of - 5? C, - 20? C, - 40? C and - 60? C was performed. Static stress-strain curves of ice under compression were obtained on which the identified strength properties of ice as well as compressive modulus. To determine the mechanical properties of ice at high-speed loading the Kolsky method was used with various embodiments of split Hopkinson bar. The deformation curves were obtained at various loading conditions. Thereon breaking points were defined as well as their dependence on the strain rate and temperature. Also static and dynamic strength properties of ice at splitting and circular shear were defined. Increase in the dynamic strength properties upon the static ones for all loading conditions was marked.

  15. Importance of Tensile Strength on the Shear Behavior of Discontinuities

    Science.gov (United States)

    Ghazvinian, A. H.; Azinfar, M. J.; Geranmayeh Vaneghi, R.

    2012-05-01

    In this study, the shear behavior of discontinuities possessing two different rock wall types with distinct separate compressive strengths was investigated. The designed profiles consisted of regular artificial joints molded by five types of plaster mortars, each representing a distinct uniaxial compressive strength. The compressive strengths of plaster specimens ranged from 5.9 to 19.5 MPa. These specimens were molded considering a regular triangular asperity profile and were designed so as to achieve joint walls with different strength material combinations. The results showed that the shear behavior of discontinuities possessing different joint wall compressive strengths (DDJCS) tested under constant normal load (CNL) conditions is the same as those possessing identical joint wall strengths, but the shear strength of DDJCS is governed by minor joint wall compressive strength. In addition, it was measured that the predicted values obtained by Barton's empirical criterion are greater than the experimental results. The finding indicates that there is a correlation between the joint roughness coefficient (JRC), normal stress, and mechanical strength. It was observed that the mode of failure of asperities is either pure tensile, pure shear, or a combination of both. Therefore, Barton's strength criterion, which considers the compressive strength of joint walls, was modified by substituting the compressive strength with the tensile strength. The validity of the modified criterion was examined by the comparison of the predicted shear values with the laboratory shear test results reported by Grasselli (Ph.D. thesis n.2404, Civil Engineering Department, EPFL, Lausanne, Switzerland, 2001). These comparisons infer that the modified criterion can predict the shear strength of joints more precisely.

  16. Compressive Fatigue in Wood

    DEFF Research Database (Denmark)

    Clorius, Christian Odin; Pedersen, Martin Bo Uhre; Hoffmeyer, Preben; Damkilde, Lars

    1999-01-01

    An investigation of fatigue failure in wood subjected to load cycles in compression parallel to grain is presented. Small clear specimens of spruce are taken to failure in square wave formed fatigue loading at a stress excitation level corresponding to 80% of the short term strength. Four frequencies ranging from 0.01 Hz to 10 Hz are used. The number of cycles to failure is found to be a poor measure of the fatigue performance of wood. Creep, maximum strain, stiffness and work are monitored thro...

  17. Small scale plasticity and compressive properties of composites

    DEFF Research Database (Denmark)

    Mikkelsen, Lars Pilgaard

    2015-01-01

    The compression strength of uni-directional composite materials is mainly governed by the fiber-misalignment and the plasticity of the matrix material [1]. Therefore, in order to improve the compression behavior of uni-directional composite materials, a focus on those terms is necessary. In the present work, the influence of the mechanical properties of the matrix material on the compression strength is studied by changing the temperature during mechanical testing and thereby making it possible ...

  18. Variação da densidade aparente e resistência à compressão paralela às fibras em função da intensidade de desbaste, adubação e posição radial em Eucalyptus grandis hill ex-maiden / Variation of the specific gravity mass and the compression strength of the thinning intensity, fertilization and the radial position in Eucalyptus grandis hill ex-maiden

    Scientific Electronic Library Online (English)

    Israel Luiz de, Lima; José Nivaldo, Garcia.

    2010-06-01

    Full Text Available O Eucalyptus grandis destaca-se pela produtividade e qualidade de sua madeira. O manejo florestal ideal das árvores em que se obtém maior proporção de madeira e melhor qualidade é uma das questões a serem consideradas nas pesquisas de E. grandis. Este trabalho teve como objetivo estudar a variação d [...] a densidade aparente e da resistência à compressão paralela às fibras em função da intensidade de desbaste, adubação e classe de diâmetro, na posição radial nas árvores de uma população de E. grandis de 21 anos de idade, manejada pelo sistema de desbastes seletivos com aplicação de fertilizantes na época do início dos desbastes, ou seja, aos 5 anos. Os fatores utilizados foram: três intensidades de desbastes seletivos (37, 50 e 75%), presença ou ausência de fertilizantes, três classes de diâmetro e cinco posições radiais. As influências dos fatores e de suas combinações foram avaliadas na densidade aparente e na resistência à compressão da madeira. A densidade aparente da madeira e a resistência à compressão foram influenciadas pelos fatores: adubo e classe de diâmetro em quase todas as posições radiais aumentaram no sentido da medula para a casca. Observou-se relação positiva entre densidade aparente, resistência à compressão e posição radial. Abstract in english The Eucalyptu grandis stands apart for its productivity and quality wood. The ideal forest management where a greater wood ratio and better quality are obtained is one of the questions to be considered in the research of the E. grandis. The present work had as its general objective the study of the [...] variation of the specific gravity and the resistance to the compression as a function of the thinning intensity, fertilization and diameter classes in the radial position in trees of a 21-year old population of E. grandis, managed under the system of selective thinning, with the application of fertilizaers. The factors used in this study were: three intensities of selective thinning (37, 50 and 75%), presence or absence of fertilizers, three diameter classes and five radial positions. The influences of the factors and of their combinations were evaluated regarding specific gravity and compression strength. The specific gravity and compression strength of the wood were influenced by factors such as fertilizer and diameter class in almost all radial positions, increasing significantly from the pith to bark. A good positive relationship was found to exist among the specific mass, compression strength and radial position.

  19. Rayleigh criterion and acoustic energy balance in unconfined self-sustained oscillating flames

    Energy Technology Data Exchange (ETDEWEB)

    Durox, D.; Schuller, T.; Noiray, N.; Birbaud, A.L.; Candel, S. [Ecole Centrale Paris, EM2C Laboratory, CNRS, 92295 Chatenay-Malabry (France)

    2008-11-15

    Instabilities of confined combustion systems are often discussed in terms of the Rayleigh criterion, which provides a necessary condition for unstable operation and is commonly used to distinguish driving and damping regions. The analysis is also carried out in some cases by making use of an acoustic energy balance in which the Rayleigh term acts as a source. The case of unconfined flames is less well documented but of importance in practical systems used in heating and drying. This study is motivated by problems of self-sustained oscillations of radiant burners for domestic or industrial processes and of various other types of open flames. Application of the Rayleigh criterion and of the balance of acoustic energy to oscillations arising in such unconfined systems is examined. The objective is to see if the Rayleigh condition is fulfilled and to show how the different perturbed variables are linked to each other to develop an unstable oscillation. These issues are investigated by experiments in two geometries. The first case relates to a single ''V''- or ''M''-shaped flame formed by a burner behaving like a Helmholtz resonator. The second geometry features a collection of conical flames (CCF) established by a multipoint injector. This system is fed by a manifold that features a set of plane modes and resonates like an organ pipe at frequencies corresponding to odd multiples of the quarter wave. The Rayleigh criterion and a related result written in the form of an acoustic energy balance are used to define conditions of instability. A link is established between the pressure signal radiated by the burner and the total heat release rate perturbation yielding the phase lag between these two variables and providing conditions for unstable operation. Systematic experiments carried out in the two burner geometries and model predictions are in good agreement indicating that the Rayleigh source term is positive and that the criterion is well fulfilled by the wavefield component corresponding to the pressure radiated back by the resonator. The gain and loss terms in the acoustic energy budget are estimated in one typical case, indicating that the source term is balanced by the acoustic power radiated away from the flame region, while dissipation of acoustic energy in the burner is shown to be essentially negligible. (author)

  20. Rayleigh criterion and acoustic energy balance in unconfined self-sustained oscillating flames

    Energy Technology Data Exchange (ETDEWEB)

    Durox, D.; Schuller, T.; Noiray, N.; Birbaud, A.L.; Candel, S. [Ecole Centrale Paris, EM2C Laboratory, CNRS, 92295 Chatenay-Malabry (France)

    2009-01-15

    Instabilities of confined combustion systems are often discussed in terms of the Rayleigh criterion, which provides a necessary condition for unstable operation and is commonly used to distinguish driving and damping regions. The analysis is also carried out in some cases by making use of an acoustic energy balance in which the Rayleigh term acts as a source. The case of unconfined flames is less well documented but of importance in practical systems used in heating and drying. This study is motivated by problems of self-sustained oscillations of radiant burners for domestic or industrial processes and of various other types of open flames. Application of the Rayleigh criterion and of the balance of acoustic energy to oscillations arising in such unconfined systems is examined. The objective is to see if the Rayleigh condition is fulfilled and to show how the different perturbed variables are linked to each other to develop an unstable oscillation. These issues are investigated by experiments in two geometries. The first case relates to a single ''V''- or ''M''-shaped flame formed by a burner behaving like a Helmholtz resonator. The second geometry features a collection of conical flames (CCF) established by a multipoint injector. This system is fed by a manifold that features a set of plane modes and resonates like an organ pipe at frequencies corresponding to odd multiples of the quarter wave. The Rayleigh criterion and a related result written in the form of an acoustic energy balance are used to define conditions of instability. A link is established between the pressure signal radiated by the burner and the total heat release rate perturbation yielding the phase lag between these two variables and providing conditions for unstable operation. Systematic experiments carried out in the two burner geometries and model predictions are in good agreement indicating that the Rayleigh source term is positive and that the criterion is well fulfilled by the wavefield component corresponding to the pressure radiated back by the resonator. The gain and loss terms in the acoustic energy budget are estimated in one typical case, indicating that the source term is balanced by the acoustic power radiated away from the flame region, while dissipation of acoustic energy in the burner is shown to be essentially negligible. (author)

  1. Experimental investigation on the use of steel-concrete bond tests for estimating axial compressive strength of concrete. Part 2: APULOT / Investigação experimental sobre o uso de ensaios de aderência aço-concreto para estimativa da resistência à compressão axial do concreto. Parte 2: APULOT

    Scientific Electronic Library Online (English)

    B. V., Silva; M. P., Barbosa; L. C. P., Silva Filho; M. S., Lorrain.

    2014-10-01

    Full Text Available EA presente pesquisa se propõe a estudar a viabilidade do uso de ensaios de aderência aço-concreto para estimativa da resistência à compressão axial do concreto, com o objetivo de empregá-los como um complemento no controle de qualidade do concreto armado. Lorrain e Barbosa (2008)[1]e Lorrain et al. [...] (2011)[2]justificam a utilização de um ensaio de aderência modificado, denominado APULOT, para estimar a resistência à compressão do concreto, incrementando as possibilidades de controle tecnológico do concreto armado em canteiros de obras. Os mesmos propõem uma adaptação do método pull-out test (POT) tradicional, normalizado pela CEB/FIP RC6:1983[3], por ser este um ensaio de baixa complexidade e de custo reduzido. Para viabilizar o uso do ensaio APULOT como ensaio de controle tecnológico do concreto em canteiro de obras é necessário definir um padrão para o mesmo e adaptá-lo da prática experimental do laboratório para o campo. A primeira parte deste trabalho buscou avaliar a potencialidade de efetuar estimativas da resistência à compressão a partir dos dados da tensão de aderência obtidos com uso do POT. Na segunda parte deste trabalho serão apresentados e discutidos resultados de ensaios realizados com o método APULOT. Foram ensaiadas 2 composições de concreto de classes distintas (25 MPa e 45 MPa), aos 3, 7 e 28 dias. Foram, ainda, usadas na confecção dos corpos de prova barras nervuradas com diâmetros nominais de 8, 10 e 12,5 mm, totalizando 144 ensaios do tipo APULOT. Os resultados obtidos mostram que, sob condições padronizadas de ensaio, a correlação entre a tensão máxima de aderência e a resistência à compressão do concreto é satisfatória, em todas as idades ensaiadas, fortalecendo o propósito de consolidar este ensaio como uma alternativa complementar para controle de qualidade do concreto armado. Abstract in english The scope of this research investigates the feasibility to use steel-concrete bond tests for estimating the compressive strength of concrete to supplementary use it in the quality control of reinforced concrete. Lorrain and Barbosa (2008)[1] and Lorrain et al. (2011)[2] justify the use of a modified [...] bond test, called APULOT, to estimate the compressive strength of concrete, thereby increasing the possibilities for the technological control of reinforced concrete at construction sites. They propose an adaptation of the traditional pull-out test (POT) method, standardized by CEB/FIP RC6:1983[3], as this is a low complexity test with the advantage of reduced costs. The use of the APULOT test as a technological control test of concrete at construction sites requires determining a standard and also adapting it from the experimental laboratory practice to the field. The first part of this work evaluated the potential to perform compressive strength estimates from the bond strength data obtained by the POT test. The second part of this paper will present and discuss the test results achieved by the APULOT method. Two concrete compositions of different classes (25 MPa and 45 MPa) were tested at 3, 7 and 28 days. Ribbed bar specimens (nominal diameters of 8, 10 and 12.5 mm) were also used in the preparation stage of the specimens, totaling 144 APULOT tests. The results show that under standard test conditions, the correlation between the maximum bond strength and the compressive strength of concrete is satisfactory at all ages tested, corroborating the objective of consolidating this test as a complementary alternative for controlling the quality of reinforced concrete.

  2. Establishment of earth tides effect on water level fluctuations in an unconfined hard rock aquifer using spectral analysis

    CERN Document Server

    Maréchal, Jean-Christophe; Ahmed, Shakeel; Lachassagne, Patrick

    2010-01-01

    Short-interval water level measurements using automatic water level recorder in a deep well in an unconfined crystalline rock aquifer at the campus of NGRI, near Hyderabad shows a cyclic fluctuation in the water levels. The observed values clearly show the principal trend due to rainfall recharge. Spectral analysis was carried out to evaluate correlation of the cyclic fluctuation to the synthetic earth tides as well as groundwater withdrawal time series in the surrounding. It was found that these fluctuations have considerably high correlation with earth tides whereas groundwater pumping does not show any significant correlation with water table fluctuations. It is concluded that earth tides cause the fluctuation in the water table. These fluctuations were hitherto unobserved during manual observations made over larger time intervals. It indicates that the unconfined aquifer is characterised by a low porosity.

  3. Wellhead compression

    Energy Technology Data Exchange (ETDEWEB)

    Harrington, Joe [Sertco Industries, Inc., Okemah, OK (United States); Vazquez, Daniel [Hoerbiger Service Latin America Inc., Deerfield Beach, FL (United States); Jacobs, Denis Richard [Hoerbiger do Brasil Industria de Equipamentos, Cajamar, SP (Brazil)

    2012-07-01

    Over time, all wells experience a natural decline in oil and gas production. In gas wells, the major problems are liquid loading and low downhole differential pressures which negatively impact total gas production. As a form of artificial lift, wellhead compressors help reduce the tubing pressure resulting in gas velocities above the critical velocity needed to surface water, oil and condensate regaining lost production and increasing recoverable reserves. Best results come from reservoirs with high porosity, high permeability, high initial flow rates, low decline rates and high total cumulative production. In oil wells, excessive annulus gas pressure tends to inhibit both oil and gas production. Wellhead compression packages can provide a cost effective solution to these problems by reducing the system pressure in the tubing or annulus, allowing for an immediate increase in production rates. Wells furthest from the gathering compressor typically benefit the most from wellhead compression due to system pressure drops. Downstream compressors also benefit from higher suction pressures reducing overall compression horsepower requirements. Special care must be taken in selecting the best equipment for these applications. The successful implementation of wellhead compression from an economical standpoint hinges on the testing, installation and operation of the equipment. Key challenges and suggested equipment features designed to combat those challenges and successful case histories throughout Latin America are discussed below.(author)

  4. Effective pressure interface law for transport phenomena between an unconfined fluid and a porous medium using homogenization

    OpenAIRE

    A Marciniak-Czochra; Mikelic, A.

    2012-01-01

    We present modeling of the incompressible viscous flows in the domain containing an unconfined fluid and a porous medium. For such setting a rigorous derivation of the Beavers-Joseph-Saffman interface condition was undertaken by J\\"ager and Mikeli\\'c [SIAM J. Appl. Math. \\rm 60 (2000), p. 1111-1127] using the homogenization method. So far the interface law for the pressure was conceived and confirmed only numerically. In this article we justify rigorously the pressure jump c...

  5. The effect of heterogeneity on the agreement between analytical and numerical solutions describing the recession flow in unconfined hillslope aquifers

    OpenAIRE

    Rocha, David; Feyen, Jan; Dassargues, Alain

    2007-01-01

    Analytical approximations or linearized versions of the Boussinesq equation, describing recession flow in unconfined hillslope aquifers have been applied extensively in the past. One of the major assumptions in the conceptual formulation is isotropic homogeneity of the aquifer. Notwithstanding the effect of aquifer heterogeneity on recession flow has been pointed out [1], only recent studies are increasingly focusing on the quantification of this effect [2,3]. In the present research, the rel...

  6. Estimation of temporal and spatial variations in groundwater recharge in unconfined sand aquifers using Scots pine inventories

    OpenAIRE

    Ala-aho, P.; Rossi, P. M.; Kløve, B.

    2014-01-01

    Climate change and land use are rapidly changing the amount and temporal distribution of recharge in northern aquifers. This paper presents a novel method for distributing Monte Carlo simulations of 1-D soil profile spatially to estimate transient recharge in an unconfined esker aquifer. The modeling approach uses data-based estimates for the most important parameters controlling the total amount (canopy cover) and timing (depth of the unsaturated zone) of groundwater rech...

  7. Compression Enhanced Shear Yield Stress of Electrorheological Fluid

    International Nuclear Information System (INIS)

    Shear tests of an electrorheological fluid with pre-applied electric field and compression along the field direction are carried out. The results show that pre-compressions can increase the shear yield stress up to ten times. Under the same external electric field strength, a higher compressive strain corresponds to a larger shear yield stress enhancement but with slight current density decrease, which shows that the particle interaction potentials are not increased by compressions but the compression-induced chain aggregation dominates the shear yield stress improvement. This pre-compression technique might be useful for developing high performance flexible ER or magnetorheological couplings

  8. Theory of transient streaming potentials in coupled unconfined aquifer-unsaturated zone flow to a well

    Science.gov (United States)

    Malama, Bwalya

    2014-04-01

    A semianalytical solution is presented for transient streaming potentials associated with flow to a pumping well in an unconfined aquifer, taking into account the effect of flow in the unsaturated zone above the water table. Flow in the unsaturated zone is modeled with a linearized form of Richards' equation using an exponential model for soil moisture retention and unsaturated hydraulic conductivity. Archie's law is invoked for unsaturated electrical conductivity. The unsaturated electrokinetic coupling coefficient is modeled with a decaying exponential, where the maximum value is at and below the water table. The coupled flow and electrokinetic problem is solved using Laplace and Hankel transforms. The results of the model predicted behavior are presented and compared to that observed in laboratory simulations of pumping tests. The early time polarity reversal predicted the model is observable in the experiments. Other nonmonotonic streaming potential behaviors predicted by the model are also evident in experimental measurements. The model is used to estimate hydraulic parameters from SP data and these compare well to those obtained from drawdown data. For example, a hydraulic conductivity of 3.6 × 10-4 m/s is obtained from SP data compared to 3.4 × 10-4 m/s from drawdown data.

  9. The influence of chemical composition on vaporisation of LNG and LPG on unconfined water surfaces

    International Nuclear Information System (INIS)

    A model is proposed for estimating the rate of vaporisation of LNG and LPG cryogen mixtures spreading on unconfined water surfaces. The model is used to examine the influence of chemical composition on the vaporisation rate of LNG and LPG during spreading. Calculations have been performed whereby the vaporisation rate of the LNG and LPG mixtures has been compared to the vaporisation of pure methane and propane, respectively, under the same initial conditions. The detailed results indicate that the vaporisation rate of LNG mixture is markedly different to that of pure methane, while the vaporisation rate of LPG mixture is similar to that of pure propane. The difference can be attributed primarily to the contributions of the direct and indirect component of the total, different, isobaric latent heat to the boiling process. For LNG, as the liquid mixture gets rich in ethane, the total, differential, isobaric latent heat increases rapidly, leading to a large decrease in the vaporisation of LNG compared to pure methane. For LPG, because of the shape of the phase envelope, only a small increase of the total latent heat and the boiling temperature is observed and consequently the change in the vaporisation is marginal. The overall results suggest that treating an LNG spill as a pure methane spill results in underestimation of the total spillage time of the order of 10-15% and in qualitatively wrong dynamics of the rate of vapour formation: thus warranting a full treatment of the thermodynamics of the mixture. (Author)

  10. LES modelling of an unconfined large-scale hydrogen-air deflagration

    International Nuclear Information System (INIS)

    This paper describes the large eddy simulation modelling of unconfined large-scale explosions. The simulations are compared with the largest hydrogen-air deflagration experiment in a 20 m diameter hemispherical polyethylene shell in the open. Two combustion sub-models, one developed on the basis of the renormalization group (RNG) theory and another derived from the fractal theory, were applied. Both sub-models include a sub-grid scale model of the turbulence generated by flame front itself based on Karlovitz's theory and the observation by Gostintsev et al on a critical distance for transition from laminar to self-similar flame propagation regime. The RNG sub-model employs Yakhot's formula for turbulent premixed flame propagation velocity. The best fit flame propagation dynamics is obtained for the fractal sub-model with a fractal dimension D = 2.22. The fractal sub-model reproduces the experimentally observed flame acceleration during the whole duration of explosion, accurately simulating the negative phase of the pressure wave but overestimating by 50% the positive phase amplitude. The RNG sub-model is closer to the experiment in predicting the positive phase but under-predicts by 30% the negative phase amplitude. Both sub-models simulate experimental flame propagation up to 20 m and pressure dynamics up to 80 m with reasonable accuracy

  11. Practical Estimates of Tensile Strength and Hoek-Brown Strength Parameter m i of Brittle Rocks

    Science.gov (United States)

    Cai, M.

    2010-03-01

    By applying the Griffith stress criterion of brittle failure, one can find that the uniaxial compressive strength (?c) of rocks is eight times the value of the uniaxial tensile strength (?t). The Griffith strength ratio is smaller than what is normally measured for rocks, even with the consideration of crack closure. The reason is that Griffith’s theories address only the initiation of failure. Under tensile conditions, the crack propagation is unstable so that the tensile crack propagation stress (?cd)t and the peak tensile strength ?t are almost identical to the tensile crack initiation stress (?ci)t. On the other hand, the crack growth after crack initiation is stable under a predominantly compressive condition. Additional loading is required in compression to bring the stress from the crack initiation stress ?ci to the peak strength ?c. It is proposed to estimate the tensile strength of strong brittle rocks from the strength ratio of R = {{?_{text{c}} }/{left| {?_{text{t} } right|}}} = 8{{?_{text{c}} }/{?_{text{ci} }}}. The term {{?_{text{c}} }/{?_{text{ci} }}} accounts for the difference of crack growth or propagation in tension and compression in uniaxial compression tests. {{?c }/{?_{ci }}} depends on rock heterogeneity and is larger for coarse grained rocks than for fine grained rocks. ?ci can be obtained from volumetric strain measurement or acoustic emission (AE) monitoring. With the strength ratio R determined, the tensile strength can be indirectly obtained from left| {?_{text{t}} } right| = {{?_{text{c}} }/R} = {{?_{text{ci}} }/8}. It is found that the predicted tensile strengths using this method are in good agreement with test data. Finally, a practical estimate of the Hoek-Brown strength parameter m i is presented and a bi-segmental or multi-segmental representation of the Hoek-Brown strength envelope is suggested for some brittle rocks. In this fashion, the rock strength parameters like ?t and m i, which require specialty tests such as direct tensile (or Brazilian) and triaxial compression tests for their determination, can be reasonably estimated from uniaxial compression tests.

  12. A comparative study of several compressibility corrections to turbulence models applied to high-speed shear layers

    Science.gov (United States)

    Viegas, John R.; Rubesin, Morris W.

    1991-01-01

    Several recently published compressibility corrections to the standard k-epsilon turbulence model are used with the Navier-Stokes equations to compute the mixing region of a large variety of high speed flows. These corrections, specifically developed to address the weakness of higher order turbulence models to accurately predict the spread rate of compressible free shear flows, are applied to two stream flows of the same gas mixing under a large variety of free stream conditions. Results are presented for two types of flows: unconfined streams with either (1) matched total temperatures and static pressures, or (2) matched static temperatures and pressures, and a confined stream.

  13. Compressive beamforming

    DEFF Research Database (Denmark)

    Xenaki, Angeliki; Mosegaard, Klaus

    2014-01-01

    Sound source localization with sensor arrays involves the estimation of the direction-of-arrival (DOA) from a limited number of observations. Compressive sensing (CS) solves such underdetermined problems achieving sparsity, thus improved resolution, and can be solved efficiently with convex optimization. The DOA estimation problem is formulated in the CS framework and it is shown that CS has superior performance compared to traditional DOA estimation methods especially under challenging scenario...

  14. Experimental investigation on the use of steel-concrete bond tests for estimating axial compressive strength of concrete: part 1 / Investigação experimental sobre o uso de ensaios de aderência aço-concreto para estimativa da resistência à compressão axial do concreto: parte 1

    Scientific Electronic Library Online (English)

    B. V., Silva; M. P., Barbosa; L. C. P., Silva Filho; M. S., Lorrain.

    2013-10-01

    Full Text Available A presente pesquisa se propõe a estudar a viabilidade do uso de ensaios de aderência aço-concreto para estimativa da resistência à compressão axial do concreto, com o objetivo de empregá-los como um complemento no controle de qualidade do concreto armado. Lorrain e Barbosa (2008) 14] e Lorrain et al [...] . (2011) 15] justificam a utilização de um ensaio de aderência modificado, denominado APULOT, para estimar a resistência à compressão do concreto, incrementando as possibilidades de controle tecnológico do concreto armado em canteiros de obras. Os mesmos propõem uma adaptação do método pull-out test (POT) tradicional, normalizado pela CEB/FIP RC6:1983 8], por ser este um ensaio de baixa complexidade e de custo reduzido. Para viabilizar o uso do ensaio APULOT como ensaio de controle tecnológico do concreto em canteiro de obras é necessário definir um padrão para o mesmo e adaptá-lo da prática experimental do laboratório para o campo. O presente trabalho buscou avaliar num primeiro momento, a potencialidade de efetuar estimativas da resistência à compressão a partir dos dados da tensão de aderência obtidos com uso do POT. Para tanto, foram ensaiadas 2 composições de concreto de classes distintas, aos 3, 7 e 28 dias. Foram, ainda, usadas na confecção dos corpos de prova barras nervuradas com diâmetros nominais de 8, 10 e 12,5 mm, totalizando 108 ensaios do tipo POT. Os resultados obtidos mostram que, sob condições padronizadas de ensaio, a correlação entre a tensão máxima de aderência e a resistência à compressão do concreto é satisfatória, em todas as idades ensaiadas, fortalecendo o propósito de consolidar este ensaio como uma alternativa complementar para controle de qualidade do concreto armado. Na segunda parte deste trabalho serão apresentados e discutidos resultados de ensaios realizados com o método APULOT. Abstract in english This study analyzes the feasibility of using steel-concrete bond tests for determining the compressive strength of concrete in order to use it as a complement in the quality control of reinforced concrete. Lorrain and Barbosa (2008) 14] and Lorrain et al. (2011) 15] justify the use of a modified bon [...] d test, termed APULOT, to estimate the compressive strength of concrete, hence increasing the possibilities for the technological control of reinforced concrete for constructions. They propose an adaptation of the traditional pull-out test (POT) method, standardized by the CEB / FIP RC6: 1983 8], because it is a low complexity and low cost test. To enable the use of the APULOT test as a technological control test of concrete at construction sites requires determining its methodology and adapting the experimental laboratory practice to the construction itself. The aim of this study is to evaluate the possibility of conducting compressive strength estimates using bond stress data obtained by the traditional pull-out tests (POT). Thus, two concrete compositions of different classes were tested at 3, 7 and 28 days. Ribbed bar specimens (nominal diameters of 8, 10 and 12.5 mm) were also used in the preparation stage, totaling 108 POT tests. The results show that the correlation between the maximum bond stress and the compressive strength of concrete is satisfactory in predetermined cases, at all ages tested, reinforcing the purpose of consolidating this test as a complementary alternative to control the quality of reinforced concrete. In the second part of this paper the test results obtained with the APULOT method are presented and discussed.

  15. Geochemical Impacts of Leaking CO2 from Subsurface Storage Reservoirs to Unconfined and Confined Aquifers

    Energy Technology Data Exchange (ETDEWEB)

    Qafoku, Nikolla; Brown, Christopher F.; Wang, Guohui; Sullivan, E. C.; Lawter, Amanda R.; Harvey, Omar R.; Bowden, Mark

    2013-04-15

    Experimental research work has been conducted and is undergoing at Pacific Northwest National Laboratory (PNNL) to address a variety of scientific issues related with the potential leaks of the carbon dioxide (CO2) gas from deep storage reservoirs. The main objectives of this work are as follows: • Develop a systematic understanding of how CO2 leakage is likely to influence pertinent geochemical processes (e.g., dissolution/precipitation, sorption/desorption and redox reactions) in the aquifer sediments. • Identify prevailing environmental conditions that would dictate one geochemical outcome over another. • Gather useful information to support site selection, risk assessment, policy-making, and public education efforts associated with geological carbon sequestration. In this report, we present results from experiments conducted at PNNL to address research issues related to the main objectives of this effort. A series of batch and column experiments and solid phase characterization studies (quantitative x-ray diffraction and wet chemical extractions with a concentrated acid) were conducted with representative rocks and sediments from an unconfined, oxidizing carbonate aquifer, i.e., Edwards aquifer in Texas, and a confined aquifer, i.e., the High Plains aquifer in Kansas. These materials were exposed to a CO2 gas stream simulating CO2 gas leaking scenarios, and changes in aqueous phase pH and chemical composition were measured in liquid and effluent samples collected at pre-determined experimental times. Additional research to be conducted during the current fiscal year will further validate these results and will address other important remaining issues. Results from these experimental efforts will provide valuable insights for the development of site-specific, generation III reduced order models. In addition, results will initially serve as input parameters during model calibration runs and, ultimately, will be used to test model predictive capability and competency. The results from these investigations will provide useful information to support site selection, risk assessment, and public education efforts associated with geological, deep subsurface CO2 storage and sequestration.

  16. Analytical and numerical analyses of an unconfined aquifer test considering unsaturated zone characteristics

    Science.gov (United States)

    Moench, Allen F.

    2008-06-01

    A 7-d, constant rate aquifer test conducted by University of Waterloo researchers at Canadian Forces Base Borden in Ontario, Canada, is useful for advancing understanding of fluid flow processes in response to pumping from an unconfined aquifer. Measured data include not only drawdown in the saturated zone but also volumetric soil moisture measured at various times and distances from the pumped well. Analytical analyses were conducted with the model published in 2001 by Moench and colleagues, which allows for gradual drainage but does not include unsaturated zone characteristics, and the model published in 2006 by Mathias and Butler, which assumes that moisture retention and relative hydraulic conductivity (RHC) in the unsaturated zone are exponential functions of pressure head. Parameters estimated with either model yield good matches between measured and simulated drawdowns in piezometers. Numerical analyses were conducted with two versions of VS2DT: one that uses traditional Brooks and Corey functional relations and one that uses a RHC function introduced in 2001 by Assouline that includes an additional parameter that accounts for soil structure and texture. The analytical model of Mathias and Butler and numerical model of VS2DT with the Assouline model both show that the RHC function must contain a fitting parameter that is different from that used in the moisture retention function. Results show the influence of field-scale heterogeneity and suggest that the RHC at the Borden site declines more rapidly with elevation above the top of the capillary fringe than would be expected if the parameters were to reflect local- or core-scale soil structure and texture.

  17. Strength and water penetrability of fly ash geopolymer concrete

    OpenAIRE

    Monita Olivia; Hamid R. Nikraz

    2011-01-01

    This paper presents a study on the strength development, water absorption and water permeability of low calcium fly ash geopolymer concrete. Geopolymer mixtures with variations of water/binder ratio, aggregate/binder ratio, aggregate grading, and alkaline/fly ash ratio were investigated. OPC (Ordinary Portland Cement) concrete with the same strength level was used as a control mix. Strength was measured by compressive strength, while water penetrability was evaluated by water absorption and w...

  18. Strength and fatigue properties of near-isotropic graphites

    International Nuclear Information System (INIS)

    Recent research activities at JAERI on the mechanical behavior of graphite for HTR will be reviewed. Several kinds of near-isotropic graphites were used for investigation of their strength and fatigue properties. The research items described here are as follows: (1) the effect of nonlinear stress-strain curve on the bending strength of the petroleum coke graphites; (2) the method for evaluating the ring compressive strength; (3) tensile-tensile and compressive-compressive fatigue strengths of petroleum coke graphites; (4) irradiation effects on the strength of isotropic graphites. Main results obtained here are the following: (1) the effect of non-linear stress-strain curves of the graphite on the bending strength should be taken into account when the bending strength is applied to the safety evaluation of core graphite structures of HTR; (2) an improved equation obtained from the curved beam theory is proposed for evaluating the ring compressive strength. The equation gives more reasonable values of the strength than those proposed by other investigators; (3) the statistical analysis based on the normal distribution was successfully applied to evaluate the fatigue strengths, and (4) the maximum elastic strain energy for the graphite materials under irradiation appeared to be dependent on the irradiation temperature and neutron fluence. (author)

  19. Extracellular bone matrix exhibits hardening elastoplasticity and more than double cortical strength: Evidence from homogeneous compression of non-tapered single micron-sized pillars welded to a rigid substrate.

    Science.gov (United States)

    Luczynski, Krzysztof W; Steiger-Thirsfeld, Andreas; Bernardi, Johannes; Eberhardsteiner, Josef; Hellmich, Christian

    2015-12-01

    We here report an improved experimental technique for the determination of Young?s modulus and uniaxial strength of extracellular bone matrix at the single micrometer scale, giving direct access to the (homogeneous) deformation (or strain) states of the tested samples and to the corresponding mechanically recoverable energy, called potential or elastic energy. Therefore, a new protocol for Focused Ion Beam milling of prismatic non-tapered micropillars, and attaching them to a rigid substrate, was developed. Uniaxial strength turns out as at least twice that measured macroscopically, and respective ultimate stresses are preceded by hardening elastoplastic states, already at very low load levels. The unloading portion of quasi-static load-displacement curves revealed Young?s modulus of 29GPa in bovine extracellular bone matrix. This value is impressively confirmed by the corresponding prediction of a multiscale mechanics model for bone, which has been comprehensively validated at various other observation scales, across tissues from the entire vertebrate animal kingdom. PMID:25842157

  20. Confined High Strength Concrete Columns: An Experimental Study

    OpenAIRE

    Jagannathan Saravanan; Suguna, K; P. N. Raghunath

    2010-01-01

    Problem statement: An experimental study on GFRP confined high strength concrete columns has been carried out with a view to evaluate its performances under uni-axial compression in terms of load and deformation capacity. Approach: High strength concrete columns strengthened with different configuration and stiffness of GFRP wraps were tested under axial compression until failure. Their response evaluated at different load levels. Results: The test results clearly indicated GFRP wrapped high ...

  1. Satellite Image JPEG Compression

    OpenAIRE

    Ch. Ramesh; K. Lohitha

    2012-01-01

    This paper proposes a novel compression scheme to compress multi band satellite images using JPEG in efficient manner. Satellite images are multiband images that constitute bands in several regions of theelectromagnetic spectrum. Wavelet transform compression and Bendelet compression Techniques were generally used with satellite images. Here we proposed a scheme to compress satellite images using JPEG.

  2. GEOCHEMICAL ASSESSMENT OF THE UNCONFINED AQUIFER IN A RECENTLY RECLAIMED WETLAND AREA: A CASE STUDY FROM THE PO RIVER DELTA

    Directory of Open Access Journals (Sweden)

    Dario Di Giuseppe

    2013-09-01

    Full Text Available This study focusses on the distribution of main anions and nitrogen species in the unconfined aquifer of a recently reclaimed land. In a 6 ha experimental field, 10 piezometers for water level measurement and groundwater sampling have been installed. After one year of monitoring, results show that the high chloride and ammonium concentrations are due to inherited from the previous brackish conditions and to organic matter mineralization, respectively. Seasonal variations and Cl/Br ratio show that the 1 m deep sub surface drainage system is the main factor conditioning the chemical characteristics and the piezometric depth of the aquifer. 

  3. Artificial Neural Network Model for Predicting Compressive

    Directory of Open Access Journals (Sweden)

    Salim T. Yousif

    2013-05-01

    Full Text Available   Compressive strength of concrete is a commonly used criterion in evaluating concrete. Although testing of the compressive strength of concrete specimens is done routinely, it is performed on the 28th day after concrete placement. Therefore, strength estimation of concrete at early time is highly desirable. This study presents the effort in applying neural network-based system identification techniques to predict the compressive strength of concrete based on concrete mix proportions, maximum aggregate size (MAS, and slump of fresh concrete. Back-propagation neural networks model is successively developed, trained, and tested using actual data sets of concrete mix proportions gathered from literature.    The test of the model by un-used data within the range of input parameters shows that the maximum absolute error for model is about 20% and 88% of the output results has absolute errors less than 10%. The parametric study shows that water/cement ratio (w/c is the most significant factor  affecting the output of the model.     The results showed that neural networks has strong potential as a feasible tool for predicting compressive strength of concrete.

  4. Increase in Strength of Partially Stabilized Zirconia After Shot Peening

    Science.gov (United States)

    Takahashi, Koji; Iwanaka, Kae; Osada, Toshio; Koike, Hitonobu

    2015-09-01

    The effects of shot peening (SP) on the strength of partially stabilized zirconia (PSZ) were studied. The compressive residual stress, apparent fracture toughness ( K C), and bending strength values of specimens subjected to SP were investigated. Results of x-ray diffraction analyses showed that SP introduced large compressive residual stress in specimens. As a result, the K C and bending strength values of specimens having semi-elliptical pre-cracks on their surfaces increased significantly. Shot-peened specimens having surface pre-cracks with lengths less than 140 µm exhibited strength comparable to that of smooth specimens and fractured outside the pre-crack zone, indicating that the pre-cracks were rendered harmless by SP. Thus, the introduction of a compressive residual stress by SP is an effective technique for increasing the strength of PSZ.

  5. Artificial sweeteners as waste water markers in a shallow unconfined aquifer

    Science.gov (United States)

    Bichler, Andrea; Muellegger, Christian; Hofmann, Thilo

    2013-04-01

    One key factor in groundwater quality management is the knowledge of flow paths and recharge. In coupled ground- and surface water systems the understanding of infiltration processes is therefore of paramount importance. Recent studies show that artificial sweeteners - which are used as sugar substitutes in food and beverages - are suitable tracers for domestic wastewater in the aquatic environment. As most rivers receive sewage discharges, artificial sweeteners might be used for tracking surface waters in groundwater. In this study artificial sweeteners are used in combination with conventional tracers (inert anions Cl-, SO42-, stable water isotopes ?18O, ?2H) to identify river water infiltration and the influence of waste water on a shallow unconfined aquifer used for drinking water production. The investigation area is situated in a mesoscale alpine head water catchment. The alluvial aquifer consists of quaternary gravel deposits and is characterized by high hydraulic permeability (kfmax 5 x 10-2 ms-1), high flow velocities (vmax 250 md-1) and a considerable productivity (2,5 m3s-1). A losing stream follows the aquifer in close proximity and is susceptible to infiltrate substantial volumes of water into the alluvial sediments. Water sampling campaigns in March and July 2012 confirmed the occurrence of artificial sweeteners (Acesulfam ACE, Sucralose SUC, Saccharin SAC and Cyclamat CYC) at the investigated site. The local sewage treatment plant was identified as point source of artificial sweeteners in the river water, with ACE concentrations up to 0,6 ?gL-1. ACE concentrations in groundwater where approximately of one order of magnitude lower: ACE was present in 33 out of 40 sampled groundwater wells with concentrations up to 0,07 ?gL-1, thus indicating considerable influence of sewage water loaded surface water throughout the aquifer. Elevated concentrations of ACE and SAC in single observation wells denote other sources of locally limited contamination. Also, the temporal variability of sweeteners in surface water and the drinking water production well is compared with other tracers. ACE, Cl-and SO42- exhibit similar patterns in the river water. However, this behaviour cannot be observed in the production well, where ACE concentrations are varying compared to Cl- and SO42-.This suggests that the production well does receive groundwater being infiltrated prior to the sewage water treatment plant. Time series analysis of 18O, ?2H will give more insight in travel times and the location of infiltration zones.

  6. Part 1: Vadose-zone column studies of toluene (enhanced bioremediation) in a shallow unconfined aquifer

    Science.gov (United States)

    Tindall, J.A.; Friedel, M.J.; Szmajter, R.J.; Cuffin, S.M.

    2005-01-01

    The objectives of the laboratory study described in this paper were (1) to determine the effectiveness of four nutrient solutions and a control in stimulating the microbial degradation of toluene in the unsaturated zone as an alternative to bioremediation methodologies such as air sparging, in situ vitrification, or others (Part I), and (2) to compare the effectiveness of the addition of the most effective nutrient solution from Part I (modified Hoagland type, nitrate-rich) and hydrogen peroxide (H2O2) on microbial degradation of toluene for repeated, simulated spills in the unsaturated zone (Part II). For Part 1, fifteen columns (30-cm diameter by 150-cm height), packed with air-dried, 0.25-mm, medium-fine sand, were prepared to simulate shallow unconfined aquifer conditions. Toluene (10 mL) was added to the surface of each column, and soil solution and soil gas samples were collected from the columns every third day for 21 days. On day 21, a second application of toluene (10 mL) was made, and the experiment was run for another 21 days. Solution 4 was the most effective for microbial degradation in Part I. For Part II, three columns were designated nutrient-rich 3-day toluene columns and received toluene injections every 3 days; three columns were designated as nutrient-rich 7-day columns and received toluene injections every 7 days; and two columns were used as controls to which no nutrient was added. As measured by CO2 respiration, the initial benefits for aerobic organisms from the O2 enhancement were sustained by the bacteria for only a short period of time (about 8 days). Degradation benefits from the nutrient solution were sustained throughout the experiment. The O2 and nutrient-enhanced columns degraded significantly more toluene than the control columns when simulating repeated spills onto the unsaturated zone, and demonstrated a potentially effective in situ bioremediation technology when used immediately or within days after a spill. The combined usage of H 2O2 and nitrate-rich nutrients served to effectively maximize natural aerobic and anaerobic metabolic processes that biodegrade hydrocarbons in petroleum-contaminated media. Applications of this technology in the field may offer economical advantages to other, more intrusive abatement technologies. ?? Springer 2005.

  7. Uncertainty Analysis of Geochemical Parameters Related To CO2 Leakage into an Unconfined Limestone Aquifer

    Science.gov (United States)

    Bacon, D. H.; Keating, E. H.; Viswanathan, H. S.; Dai, Z.

    2011-12-01

    Accurate prediction of the impact of leaking CO2 on groundwater quality is limited by the complexity of subsurface aquifers and the geochemical reactions that control drinking water compositions. As a result there is a high uncertainty associated with any predictions, hampering monitoring plans, interpretation of the monitoring results, and mitigation plans for a given site. Many physical and geochemical characteristics will dictate a drinking water aquifer's response to a CO2 leak. As a part of the National Risk Assessment Program (NRAP), funded by the U.S. Department of Energy, scientists at Pacific Northwest National Laboratory (PNNL) and Los Alamos National Laboratory (LANL) have collaborated on the development of a 3D heterogeneous model of the Edwards Aquifer in Texas to examine the impacts of CO2 leakage into an unconfined, carbonate aquifer. Using the same base case model, LANL has focused on uncertainty quantification (UQ) of the aquifer's hydraulic properties, whereas PNNL has examined the impact of uncertainty related to geochemical parameters. This abstract describes PNNL's work on geochemical UQ. The uncertainty analysis looks at the impact on several model outputs, including CO2 leakage rate from the water table, mean pH value, and pHsimulations we use STOMP-CO2-R, which is a multiphase flow simulator, coupled with the reactive transport module ECKEChem, developed at PNNL to simulate CO2 sequestration in deep saline formations and the associated reactions with formation minerals. For uncertainty quantification, we use the PSUADE code. The user defines a range and/or distribution of key input parameters. PSUADE then generates a number of parameter files containing sample points from prescribed sampling method (i.e. Latin hypercube, Monte Carlo, etc.) and a file that combines the probability distribution functions for the selected parameters. STOMP input files are subsequently developed from each set of PSUADE generated sampling points prior to execution. Output from STOMP is then evaluated with respect to a given objective function. At this point, the response (n-dimensional) hyper-surface of the objective function is conducted and used for a global sensitivity analysis to evaluate the most sensitive parameters. Based on the global sensitivity analysis, the process is repeated, where the number of parameters is reduced to the most sensitive parameters and the number of sampling points increases to enhance resolution in the space of uncertain parameters. Once we have convergence on resolution, then the resulting response surface becomes the reduced order model that will be used to generate the risk profiles over a given time period.

  8. Estimation of Unconfined Aquifer Hydrologic Properties Using Gravity and Drawdown Data

    Science.gov (United States)

    Harry, D. L.; Woodworth, J.; Sanford, W. E.

    2010-12-01

    An unconfined aquifer test using temporal gravity measurements was conducted in shallow alluvium near Fort Collins, Colorado on September 26-27, 2009. Drawdown was recorded in four monitoring wells at distances of 6.34, 15.4, 30.7, and 60.2 m from the pumping well. Continuous gravity measurements were recorded with a Scintrex CG-5 gravimeter near the closest well, at 6.3 m, over several multi-hour intervals during the 27 hour pumping test. Type-curve matching of the drawdown data performed assuming Neuman’s solution yields transmissivity T, specific yield Sy, and elastic component of storativity S estimates of 0.018 m2s-1, 0.041, and 0.0093. The gravitational response to dewatering was modeled assuming drawdown cone geometries consistent with Neuman’s drawdown solution for 4200 realizations of T, Sy, and S. Minimization of the root mean square misfit between the modeled and observed gravity change during drawdown results in T=0.0033 m2s-1, Sy=0.45, and S =0.0052. Drawdown conforming to Neuman’s solution was forward modeled using 1400 realizations of T, Sy, and S. Minimization of the root mean square misfit between these forward models and observed drawdown in the monitoring wells results in T=0.0080 m2s-1, Sy=0.26, and S=0.000004. Discrepancy between type-curve matching results, gravity analysis results, and drawdown modeling is attributed to heterogeneity and anisotropy within the aquifer, and possibly a relatively large drawdown in the aquifer, conditions which fail to satisfy the assumptions made for Neuman’s solution. In this aquifer test, gravity was most sensitive to transmissivity, less sensitive to specific yield, and insensitive to the specific storage-saturated thickness quotient. Simultaneous deployment of multiple gravity stations and consideration of a drawdown solution that includes anisotropy and the possibility that drawdown is large compared to aquifer thickness is recommended to better constrain gravity-derived aquifer property estimates of transmissivity and specific yield during similar tests in the future.

  9. Geochemical Impacts of Leaking CO2 from Subsurface Storage Reservoirs to an Unconfined Oxidizing Carbonate Aquifer

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Guohui; Qafoku, Nikolla; Lawter, Amanda R.; Bowden, Mark E.; Harvey, Omar; Sullivan, E. C.; Brown, Christopher F.

    2015-07-15

    A series of batch and column experiments combined with solid phase characterization studies (i.e., quantitative x-ray diffraction and wet chemical extractions) were conducted to address a variety of scientific issues and evaluate the impacts of the potential leakage of carbon dioxide (CO2) from deep subsurface storage reservoirs. The main objective was to gain an understanding of how CO2 gas influences: 1) the aqueous phase pH; and 2) mobilization of major, minor, and trace elements from minerals present in an aquifer overlying potential CO2 sequestration subsurface repositories. Rocks and slightly weathered rocks representative of an unconfined, oxidizing carbonate aquifer within the continental US, i.e., the Edwards aquifer in Texas, were used in these studies. These materials were exposed to a CO2 gas stream or were leached with a CO2-saturated influent solution to simulate different CO2 gas leakage scenarios, and changes in aqueous phase pH and chemical composition were measured in the liquid samples collected at pre-determined experimental times (batch experiments) or continuously (column experiments). The results from the strong acid extraction tests confirmed that in addition to the usual elements present in most soils, rocks, and sediments, the Edward aquifer samples contain As, Cd, Pb, Cu, and occasionally Zn, which may potentially be mobilized from the solid to the aqueous phase during or after exposure to CO2. The results from the batch and column experiments confirmed the release of major chemical elements into the contacting aqueous phase (such as Ca, Mg, Ba, Sr, Si, Na, and K); the mobilization and possible rapid immobilization of minor elements (such as Fe, Al, and Mn), which are able to form highly reactive secondary phases; and sporadic mobilization of only low concentrations of trace elements (such as As, Cd, Pb, Cu, Zn, Mo, etc.). The results from this experimental research effort will help in developing a systematic understanding of how CO2 leakage is likely to influence pertinent geochemical processes (e.g., dissolution/precipitation, sorption/desorption) in the aquifer sediments and will support site selection, risk assessment, policy-making, and public education efforts associated with geologic carbon sequestration.

  10. Strength of Concrete Containing Basalt Fibre

    Directory of Open Access Journals (Sweden)

    Parvez Imraan Ansari

    2015-04-01

    Full Text Available This paper presents the comparative study of effect of basalt fibre on compressive and split tensile strength of M40 grade concrete. The basalt fibre was mixed in concrete by (0.5%, 1%, and 1.5% of its total weight of cement in concrete. Results indicated that the strength increases with increase of basalt fibre content up to 1.0% beyond that there is a reduction in strength on increasing basalt fibre. The results show that the concrete specimen with 1.0% of basalt fibre gives better performance when it compared with 0.5%and 1.5% basalt fibre mix in concrete specimens.

  11. Effect of Flyash on the Strength Characteristics of Waste Plastic Fibre Reinforced Concrete - an Experimental Investigation

    OpenAIRE

    Prahallada M.C

    2014-01-01

    In this paper an attempt has been made to study the effect of addition of flyash and replacement cement by flyash in different percentages on the properties of workability and strength characteristics of waste plastic fibre reinforced concrete. The strength characteristics viz., compressive strength, tensile strength, flexural strength, impact strength and workability characteristics are found for waste plastic fibre reinforced concrete, when flyash was added in different perc...

  12. Compression limits in cascaded quadratic soliton compression

    DEFF Research Database (Denmark)

    Bache, Morten; Bang, Ole; Krolikowski, Wieslaw; Moses, Jeffrey; Wise, Frank W.

    2008-01-01

    Cascaded quadratic soliton compressors generate under optimal conditions few-cycle pulses. Using theory and numerical simulations in a nonlinear crystal suitable for high-energy pulse compression, we address the limits to the compression quality and efficiency.

  13. Satellite data compression

    CERN Document Server

    Huang, Bormin

    2011-01-01

    Satellite Data Compression covers recent progress in compression techniques for multispectral, hyperspectral and ultra spectral data. A survey of recent advances in the fields of satellite communications, remote sensing and geographical information systems is included. Satellite Data Compression, contributed by leaders in this field, is the first book available on satellite data compression. It covers onboard compression methodology and hardware developments in several space agencies. Case studies are presented on recent advances in satellite data compression techniques via various prediction-

  14. Estimation of temporal and spatial variations in groundwater recharge in unconfined sand aquifers using Scots pine inventories

    Science.gov (United States)

    Ala-aho, P.; Rossi, P. M.; Kløve, B.

    2015-04-01

    Climate change and land use are rapidly changing the amount and temporal distribution of recharge in northern aquifers. This paper presents a novel method for distributing Monte Carlo simulations of 1-D sandy sediment profile spatially to estimate transient recharge in an unconfined esker aquifer. The modelling approach uses data-based estimates for the most important parameters controlling the total amount (canopy cover) and timing (thickness of the unsaturated zone) of groundwater recharge. Scots pine canopy was parameterized to leaf area index (LAI) using forestry inventory data. Uncertainty in the parameters controlling sediment hydraulic properties and evapotranspiration (ET) was carried over from the Monte Carlo runs to the final recharge estimates. Different mechanisms for lake, soil, and snow evaporation and transpiration were used in the model set-up. Finally, the model output was validated with independent recharge estimates using the water table fluctuation (WTF) method and baseflow estimation. The results indicated that LAI is important in controlling total recharge amount. Soil evaporation (SE) compensated for transpiration for areas with low LAI values, which may be significant in optimal management of forestry and recharge. Different forest management scenarios tested with the model showed differences in annual recharge of up to 100 mm. The uncertainty in recharge estimates arising from the simulation parameters was lower than the interannual variation caused by climate conditions. It proved important to take unsaturated thickness and vegetation cover into account when estimating spatially and temporally distributed recharge in sandy unconfined aquifers.

  15. Fens, seasonal wetlands, and the unconfined pumice aquifer east of the Cascade Range, south-central Oregon

    Science.gov (United States)

    Cummings, M. L.; Large, A.; Mowbray, A.; Weatherford, J.; Webb, B.

    2013-12-01

    Fens and seasonal wetlands in the headwaters of the Klamath and Deschutes river basins in south-central Oregon are present in an area blanketed by 2 to 3 m of pumice during the Holocene eruption of Mount Mazama. The lower pumice unit, moderately sorted coarse pumice lapilli to blocks (0.3 to 0.7 cm), phenocrysts, and lithics is 1.5 to 2 m thick; the upper pumice unit, poorly sorted lapilli to blocks (0.2 to 6 cm), minor phenocrysts, and lithics is 1 m thick. Pumice is a perched, unconfined aquifer over low permeability bedrock or pre-eruption fine-grained sediment. Early landscape response included partial erosion of pumice from pre-eruption valleys followed by partial filling by alluvium: phenocryst- and lithic-rich sand grading upward to glassy silt with rounded pumice pebbles. Groundwater-fed wetlands, fens, associated with the unconfined pumice aquifer occur as areas of diffuse groundwater discharge through gently sloping, convex surfaces underlain by up to 1.4 m of peat. Locally, focused discharge through the confining peat layer feeds low discharge streams. Carnivorous plants (sundews and pitcher plants) may be present. The sharp contact between peat and underlying pumice is an erosion surface that cuts progressively deeper into the upper and lower pumice units downslope. At the base of the slope peat with fen discharge feeding surface flow, alluvium with no surface flow, or a subtle berm separating the slope underlain by peat from the valley bottom underlain by alluvium may be present. Distinct vegetation changes take place at this transition. The erosion surface that underlies the peat layer in the fen is at the surface on the opposing valley wall and progressively rises up through the lower and upper pumice units: iron staining and cementation of pumice is locally prominent. Up to 1.5 m difference in water table occurs between the fen and opposing valley wall. Water table in piezometers screened in peat is at the surface. Locally, water table screened in pumice below the peat confining layer is up to 24 cm above the surface. Electrical conductivity in groundwater from the unconfined pumice aquifer ranged between 20 and 45 ?S/cm. Rarely, electrical conductivity greater than 250 ?S/cm is measured. Hydrochemistry indicates these waters are distinctly different (Ca-bicarbonate, [Fe] up to 22 mg/l) from water commonly encountered in the unconfined pumice aquifer (Na-bicarbonate, [Fe] less than 0.07 mg/l). Seasonally elevated water tables are present where pre-eruption topography allows snowmelt to accumulate in the unconfined pumice aquifer in valley bottoms and upland surfaces. Differential hardness of volcanic bedrock units control distribution in valley bottoms; emplacement processes and weathering of flow tops control distribution in upland settings. In both settings the lower pumice unit is saturated, but the upper pumice unit may be absent or thin. Alluvium commonly overlies pumice in valley bottoms. The water table may fluctuate up to 1.5 m from the spring snowmelt to late summer. Electrical conductivity in the pumice aquifer ranges between 19 and 250 ?S/cm and commonly increases at single sites as the dry season progresses.

  16. Compressive properties of aluminum foams by gas injection method

    OpenAIRE

    Zhang Huiming; Chen Xiang; Fan Xueliu

    2012-01-01

    The compressive properties of aluminum foams by gas injection method are investigated under both quasi-static and dynamic compressive loads in this paper. The experimental results indicate that the deformation of the aluminum foams goes through three stages: elastic deforming, plastic deforming and densification stage, during both the quasi-static and dynamic compressions. The aluminum foams with small average cell size or low porosity have high yield strength. An increase in strain rate can ...

  17. Nitrate reduction in an unconfined sandy aquifer : Water chemistry, reduction processes, and geochemical modeling

    DEFF Research Database (Denmark)

    Postma, Diederik Jan; Boesen, Carsten

    1991-01-01

    Nitrate distribution and reduction processes were investigated in an unconfined sandy aquifer of Quaternary age. Groundwater chemistry was studied in a series of eight multilevel samplers along a flow line, deriving water from both arable and forested land. Results show that plumes of nitrate-contaminated groundwater emanate from the agricultural areas and spread through the aquifer. The aquifer can be subdivided into an upper 10- to 15-m thick oxic zone that contains O2 and NO3-, and a lower anoxic zone characterized by Fe2+-rich waters. The redox boundary is very sharp, which suggests that reduction processes of O2 and NO3- occur at rates that are fast compared to the rate of downward water transport. Nitrate-contaminated groundwater contains total contents of dissolved ions that are two to four times higher than in groundwater derived from the forested area. The persistence of the high content of total dissolved ions in the NO3- free anoxic zone indicates the downward migration of contaminants and that active nitrate reduction is taking place. Nitrate is apparently reduced to N2 because both nitrite and ammonia are absent or found at very low concentrations. Possible electron donors in the reduced zone of the aquifer are organic matter, present as reworked brown coal fragments from the underlying Miocene, and small amounts of pyrite at an average concentration of 3.6 mmol/kg. Electron balances across the redoxcline, based on concentrations of O2, NO3-, SO4(2-) and total inorganic carbon (TIC), indicate that pyrite is by far the dominant electron donor even though organic matter is much more abundant. Groundwater transport and chemical reactions were modeled using the code PHREEQM, which combines a chemical equilibrium model with a one-dimensional mixing cell transport model. Only the vertical component of the water transport was modeled since, in contrast to rates along flow lines, the vertical rates are close to constant as required by the one-dimensional model. Average vertical transport rates of water in the saturated zone were obtained by tritium dating. The modeling process is a two-step procedure. First the sediment column is initialized with natural water containing only oxygen as electron acceptor, and subsequently agricultural waters containing both oxygen and nitrate are fed into the column. The nitrate concentration of agricultural waters entering the saturated zone varies with time, and an input function was therefore constructed by linear mixing of natural waters and agricultural waters. This input function was fed into the column initialized with natural water, and the model run forward in time to the year 1988 where field data are available. Comparison with field data shows that the variation in groundwater chemistry is well described by the model when reduction of oxygen and reduction of nitrate by pyrite oxidation are the only redox reactions occurring. Finally, predictions are made for the distribution of water chemistry in the year 2003. Downward progression of the redoxcline is accelerated by afactor of five due to nitrate pollution of the aquifer, but absolute rates remain small, of the order of a few centimeters per year.

  18. Notched Strength Allowables and Inplane Shear Strength of AS4/VRM-34 Textile Laminates

    Science.gov (United States)

    Grenoble, Ray W.; Johnston, William M.

    2013-01-01

    Notched and unnotched strength allowables were developed for a textile composite to provide input data to analytical structural models based on the Pultruded Rod Stiffened Efficient Unitized Structure (PRSEUS) concept. Filled-hole tensile strength, filled-hole compressive strength, and inplane shear strength along stitch lines have been measured. The material system evaluated in this study is based on warp-knitted preforms of AS4 carbon fibers and VRM-34 epoxy resin, which have been processed via resin infusion and oven curing. All specimens were tested in as-fabricated (dry) condition. Filled-hole strengths were evaluated with and without through-thickness stitching. The effects of scaling on filled-hole tensile strength were evaluated by testing specimens in two widths, but with identical width / hole-diameter ratios. Inplane shear specimens were stitched in two configurations, and two specimen thicknesses were tested for each stitch configuration.

  19. From “Smaller is Stronger” to “Size-Independent Strength Plateau”: Towards Measuring the Ideal Strength of Iron

    KAUST Repository

    Han, Wei-Zhong

    2015-04-17

    The trend from “smaller is stronger” to “size-independent strength plateau” is observed in the compression of spherical iron nanoparticles. When the diameter of iron nanospheres is less than a critical value, the maximum contact pressure saturates at 10.7 GPa, corresponding to a local shear stress of ?9.4 GPa, which is comparable to the theoretical shear strength of iron.

  20. The Compressible Ising Spin Glass: Simulation Results

    CERN Document Server

    Marshall, A H

    2006-01-01

    This paper reports numerical studies of a compressible version of the Ising spin glass in two dimensions. Compressibility is introduced by adding a term that couples the spin-spin interactions and local lattice deformations to the standard Edwards-Anderson model. The relative strength of this coupling is controlled by a single dimensionless parameter, mu. The timescale associated with the dynamics of the system grows exponentially as mu is increased, and the energy of the compressible system is shifted downward by an amount proportional to mu times the square of the uncoupled energy. This result leads to the formulation of a simplified model that depends solely on spin variables; analysis and numerical simulations of the simplified model predict a critical value of the coupling strength above which the spin-glass transition cannot exist at any temperature.

  1. Temperature Effects on Brain Tissue in Compression

    CERN Document Server

    Rashid, Badar; Gilchrist, Michael; 10.1016/j.jmbbm.2012.04.005

    2013-01-01

    Extensive research has been carried out for at least 50 years to understand the mechanical properties of brain tissue in order to understand the mechanisms of traumatic brain injury (TBI). The observed large variability in experimental results may be due to the inhomogeneous nature of brain tissue and to the broad range of test conditions. However, test temperature is also considered as one of the factors influencing the properties of brain tissue. In this research, the mechanical properties of porcine brain have been investigated at 22C (room temperature) and at 37C (body temperature) while maintaining a constant preservation temperature of approximately 4-5C. Unconfined compression tests were performed at dynamic strain rates of 30 and 50/s using a custom made test apparatus. There was no significant difference (p = 0.8559 - 0.9290) between the average engineering stresses of the brain tissue at the two different temperature conditions. The results of this study should help to understand the behavior of bra...

  2. Study Of Characteristics Strength of Concrete with Admixtures by Flexural and Disc Bending Test

    Directory of Open Access Journals (Sweden)

    Anant Kumar

    2014-08-01

    Full Text Available Concrete is widely used in structural engineering with its high compressive strength, low cost and abandoned raw material, but common concrete has some deficiency, such as shrinkage and cracking, low tensile strength and flexural strength, high brittleness, that restrict its applications. To overcome these deficiencies’ additional materials are added to improve the performance of the concrete. Super plasticizer is a chemical added to conventional concrete mix that makes the concrete more workable and it can be placed easily. The aim of this project work to study the characteristics strengths of concrete such as compressive strength, flexural strength, split tensile strength, diametric strength and tensile strength by disc bending test. For the experimental work normal concrete M 40 has to be prepared and characteristics strength such as compressive strength, tensile strength, and flexural strength have to be achieved. This strength has to be performed after 7 days and 28 days curing. After that in addition of super plasticizer the study of the strength have to be performed with various % of plasticizer such as 0.60% to 1.2 % by the weight of cement and study of strength of concrete have to be performed at 7 days and 28 days. A relative comparison of the strength of the concrete with addition of admixtures with normal concrete can be study.

  3. Confined High Strength Concrete Columns: An Experimental Study

    Directory of Open Access Journals (Sweden)

    Jagannathan Saravanan

    2010-01-01

    Full Text Available Problem statement: An experimental study on GFRP confined high strength concrete columns has been carried out with a view to evaluate its performances under uni-axial compression in terms of load and deformation capacity. Approach: High strength concrete columns strengthened with different configuration and stiffness of GFRP wraps were tested under axial compression until failure. Their response evaluated at different load levels. Results: The test results clearly indicated GFRP wrapped high strength concrete columns exhibit enhances performance. Conclusion: The study concluded that the three GFRP materials attempted UDC GFRP provided the maximum benefit with respect to load and deformation.

  4. Strength of Ship Stiffened Panels under Combined Loading

    DEFF Research Database (Denmark)

    Weicheng, Cui; Wang, Young-jun; Pedersen, Preben Terndrup

    2000-01-01

    A ship's hull is a box girder structure composed of stiffened panels and therefore, strength of stiffened panels plays a significant role for the ultimate strength analysis of ship structures. In recent years several authors have proposed simplified methods to calculate the ultimate strength of stiffened panels. However, the majority of these investigations deal with stiffened panels subjected to longitudinal compression only. For real ship structural stiffened panels, the most general loading c...

  5. Tensile Strength of Water Exposed to Pressure Pulses

    DEFF Research Database (Denmark)

    Andersen, Anders Peter; MØrch, Knud Aage

    2012-01-01

    It is well known that pressurization for an extended period of time increases the tensile strength of water, but little information is available on the effect of pressure pulses of short duration. This is addressed in the present paper where we first measure the tensile strength of water at an extended water-solid interface by imposing a tensile stress pulse which easily causes cavitation. Next, a compressive pulse of duration ~1 ms and a peak intensity of a few bar is imposed prior to the tensile stress pulse. A dramatic increase of the tensile strength is observed immediately after the compressive pulse, but the effect is shortlived. We presume that diffusion of non-condensable gas from the cavitation nuclei into the liquid at compression, and back again later, is responsible for the changes of tensile strength.

  6. Microbuckling compression failure of a radiation-induced wood/polymer composite

    International Nuclear Information System (INIS)

    A wood/polymer composite was produced by impregnating Ramin wood with methyl methacrylate monomer and subsequently polymerizing it by gamma irradiation. To assess the improvement in compression strength of the wood caused by the polymer impregnation, a microbuckling compression failure mechanism was used to model the compression failure of the composite. Such a mechanism was found to predict a linear relationship between the compression strength and the percentage polymer impregnation (by weight). Uniaxial compression test results at 45(±5)% and 90(±5)% relative humidity levels, after being statistically analysed, showed that such a linear relationship was valid for up to 100% polymer impregnation. (author)

  7. Isostatic compression of buffer blocks. Middle scale

    International Nuclear Information System (INIS)

    Manufacturing of buffer components using isostatic compression method has been studied in small scale in 2008 (Laaksonen 2010). These tests included manufacturing of buffer blocks using different bentonite materials and different compression pressures. Isostatic mould technology was also tested, along with different methods to fill the mould, such as vibration and partial vacuum, as well as a stepwise compression of the blocks. The development of manufacturing techniques has continued with small-scale (30 %) blocks (diameter 600 mm) in 2009. This was done in a separate project: Isostatic compression, manufacturing and testing of small scale (D = 600 mm) buffer blocks. The research on the isostatic compression method continued in 2010 in a project aimed to test and examine the isostatic manufacturing process of buffer blocks at 70 % scale (block diameter 1200 to 1300 mm), and the aim was to continue in 2011 with full-scale blocks (diameter 1700 mm). A total of nine bentonite blocks were manufactured at 70 % scale, of which four were ring-shaped and the rest were cylindrical. It is currently not possible to manufacture full-scale blocks, because there is no sufficiently large isostatic press available. However, such a compression unit is expected to be possible to use in the near future. The test results of bentonite blocks, produced with an isostatic pressing method at different presses and at different sizes, suggest that the technical characteristics, for example bulk density and strength values, are somewhat independent of the size of the block, and that the blocks have fairly homogenous characteristics. Water content and compression pressure are the two most important properties determining the characteristics of the compressed blocks. By adjusting these two properties it is fairly easy to produce blocks at a desired density. The commonly used compression pressure in the manufacturing of bentonite blocks is 100 MPa, which compresses bentonite to approximately half its original volume, doubling its density. (orig.)

  8. Isostatic compression of buffer blocks. Middle scale

    Energy Technology Data Exchange (ETDEWEB)

    Ritola, J.; Pyy, E. [VTT Technical Research Centre of Finland, Espoo (Finland)

    2012-01-15

    Manufacturing of buffer components using isostatic compression method has been studied in small scale in 2008 (Laaksonen 2010). These tests included manufacturing of buffer blocks using different bentonite materials and different compression pressures. Isostatic mould technology was also tested, along with different methods to fill the mould, such as vibration and partial vacuum, as well as a stepwise compression of the blocks. The development of manufacturing techniques has continued with small-scale (30 %) blocks (diameter 600 mm) in 2009. This was done in a separate project: Isostatic compression, manufacturing and testing of small scale (D = 600 mm) buffer blocks. The research on the isostatic compression method continued in 2010 in a project aimed to test and examine the isostatic manufacturing process of buffer blocks at 70 % scale (block diameter 1200 to 1300 mm), and the aim was to continue in 2011 with full-scale blocks (diameter 1700 mm). A total of nine bentonite blocks were manufactured at 70 % scale, of which four were ring-shaped and the rest were cylindrical. It is currently not possible to manufacture full-scale blocks, because there is no sufficiently large isostatic press available. However, such a compression unit is expected to be possible to use in the near future. The test results of bentonite blocks, produced with an isostatic pressing method at different presses and at different sizes, suggest that the technical characteristics, for example bulk density and strength values, are somewhat independent of the size of the block, and that the blocks have fairly homogenous characteristics. Water content and compression pressure are the two most important properties determining the characteristics of the compressed blocks. By adjusting these two properties it is fairly easy to produce blocks at a desired density. The commonly used compression pressure in the manufacturing of bentonite blocks is 100 MPa, which compresses bentonite to approximately half its original volume, doubling its density. (orig.)

  9. Study on Strength Development of High Strength Concrete Containing Fly ash and Silica fume

    OpenAIRE

    A R Hariharan,; A S Santhi,; G Mohan Ganesh

    2011-01-01

    This paper presents the results of an experimental investigation carried out to evaluate the compressive strength of High Strength Concrete. High Strength Concrete is made by partial replacement of cement by fly ash (FA) and silica fume (SF). In this study the Class C fly ash used in various proportions 30%, 40% and 50% and that of silica fume by 6% and 10% by weight of cement. The mix proportions of concrete had a constant water binder ratio of 0.4 and super plasticizer was added based on th...

  10. Maintained ship hull girder ultimate strength reliability considering corrosion and fatigue

    DEFF Research Database (Denmark)

    Hu, Yong; Cui, W.; Pedersen, Preben Terndrup

    2004-01-01

    The prupose of this paper is to propose a methodology to assess the time-variant ultimate strength of ship hull girder under the degradations of corrosion and fatigue. The effects of fatigue cracks on the tensile and compressive residual ultimate strength of stiffened panels and unstiffened plates are analyzed by an FE method. Based on FE analysis restuls, some empirical formulae are provided for effective calculation of the compressive or tensile ultimate strength of cracked or intact unstiffen...

  11. Nondestructive determination of iliac crest cancellous bone strength by pQCT

    DEFF Research Database (Denmark)

    Ebbesen, Ebbe Nils; Thomsen, Jesper Skovhus; Mosekilde, Lis

    1997-01-01

    The close relationship between apparent bone density and compressive strength is well established. In clinical situations, histomorphometry and determination of the compressive strength on bone biopsies are destructive methods and require two separate biopsies from each patient. The aim of this study was to evaluate whether volumetric bone density measured by peripheral quantitative computed tomography (pQCT) could be used as a nondestructive method for estimating trabecular bone strength of ili...

  12. Estimation of temporal and spatial variations in groundwater recharge in unconfined sand aquifers using Scots pine inventories

    Directory of Open Access Journals (Sweden)

    P. Ala-aho

    2014-07-01

    Full Text Available Climate change and land use are rapidly changing the amount and temporal distribution of recharge in northern aquifers. This paper presents a novel method for distributing Monte Carlo simulations of 1-D soil profile spatially to estimate transient recharge in an unconfined esker aquifer. The modeling approach uses data-based estimates for the most important parameters controlling the total amount (canopy cover and timing (depth of the unsaturated zone of groundwater recharge. Scots pine canopy was parameterized to leaf area index (LAI using forestry inventory data. Uncertainty in the parameters controlling soil hydraulic properties and evapotranspiration was carried over from the Monte Carlo runs to the final recharge estimates. Different mechanisms for lake, soil, and snow evaporation and transpiration were used in the model set-up. Finally, the model output was validated with independent recharge estimates using the water table fluctuation method and baseflow estimation. The results indicated that LAI is important in controlling total recharge amount, and the modeling approach successfully reduced model uncertainty by allocating the LAI parameter spatially in the model. Soil evaporation compensated for transpiration for areas with low LAI values, which may be significant in optimal management of forestry and recharge. Different forest management scenarios tested with the model showed differences in annual recharge of up to 100 mm. The uncertainty in recharge estimates arising from the simulation parameters was lower than the interannual variation caused by climate conditions. It proved important to take unsaturated depth and vegetation cover into account when estimating spatially and temporally distributed recharge in sandy unconfined aquifers.

  13. Determining flow, recharge, and vadose zone drainage in an unconfined aquifer from groundwater strontium isotope measurements, Pasco Basin, WA

    International Nuclear Information System (INIS)

    Strontium isotope compositions (87Sr/86Sr) measured in groundwater samples from 273 wells in the Pasco Basin unconfined aquifer below the Hanford Site show large and systematic variations that provide constraints on groundwater recharge, weathering rates of the aquifer host rocks, communication between unconfined and deeper confined aquifers, and vadose zone-groundwater interaction. The impact of millions of cubic meters of wastewater discharged to the vadose zone (103-105 times higher than ambient drainage) shows up strikingly on maps of groundwater 87Sr/86Sr. Extensive access through the many groundwater monitoring wells at the site allows for an unprecedented opportunity to evaluate the strontium geochemistry of a major aquifer, hosted primarily in unconsolidated sediments, and relate it to both long term properties and recent disturbances. Groundwater 87Sr/86Sr increases systematically from 0.707 to 0.712 from west to east across the Hanford Site, in the general direction of groundwater flow, as a result of addition of Sr from the weathering of aquifer sediments and from diffuse drainage through the vadose zone. The lower 87Sr/86Sr groundwater reflects recharge waters that have acquired Sr from Columbia River Basalts. Based on a steady-state model of Sr reactive transport and drainage, there is an average natural drainage flux of 0-1.4 mm/yr near the western margin of the Hanford Site, and ambient drainage may be up to 30 mm/yr in the center of the site assuming an average bulk rock weathering rate of 10-7.5 g/g/yr

  14. Compressive properties of aluminum foams by gas injection method

    Directory of Open Access Journals (Sweden)

    Zhang Huiming

    2012-08-01

    Full Text Available The compressive properties of aluminum foams by gas injection method are investigated under both quasi-static and dynamic compressive loads in this paper. The experimental results indicate that the deformation of the aluminum foams goes through three stages: elastic deforming, plastic deforming and densification stage, during both the quasi-static and dynamic compressions. The aluminum foams with small average cell size or low porosity have high yield strength. An increase in strain rate can lead to an increase of yield strength. The yield strength of the aluminum foams under the dynamic loading condition is much greater than that under the quasi-static loading condition. Dynamic compressive tests show that a higher strain rate can give rise to a higher energy absorption capacity, which demonstrates that the aluminum foams have remarkable strain rate sensitivity on the loading rate.

  15. On the Effect of Curvature in Debonded Sandwich Panels Subjected to Compressive Loading

    DEFF Research Database (Denmark)

    Moslemian, Ramin; Berggreen, Christian; Branner, Kim

    2008-01-01

    The aim of this study is to obtain an understanding of the effect of panel curvature on residual compressive strength in debond damaged sandwich panels. Finite element analysis and linear elastic fracture mechanics are employed to analyze the residual compressive strength of curved panels with a circular debond. The Crack Surface Displacement Extrapolation (CSDE) method is used to calculate fracture parameters in the interface. Compression tests were carried out on two types of debonded curved p...

  16. Strength of Ship Plates under Combined Loading

    DEFF Research Database (Denmark)

    Cui, W.; Wang, Y.

    2002-01-01

    Strength of ship plates plays a significant role in the ultimate strength analysis of ship structures. In recent years several authors have proposed simplified analytical methods to calculate the ultimate strength of unstiffened plates. The majority of these investigations deal with plates subjected to longitudinal compression only. For real ship structural plating, the most general loading case is a combination of longitudinal stress, transverse stress, shear stress and lateral pressure. In this paper, the simplified analytical method is generalized to deal with such combined load cases. The obtained results indicate that the simplified analytical method is able to determine the ultimate strength of unstiffened plates with imperfections in the form of welding-induced residual stresses and geometric deflections subjected to combined loads. Comparisons with experimental results show that the procedure has sufficient accuracy for practical applications in design.

  17. Strength of ship plates under combined loading

    DEFF Research Database (Denmark)

    Cui, Weiching; Wang, Yongjun

    2000-01-01

    Strength of ship plates plays a significant role for the ultimate strength analysis of ship structures. In recent years several authors have proposed simplified methods to calculate the ultimate strength of unstiffened plates. The majority of these investigations deal with plates subjected to longitudinal compression only. For real ship structural plating, the most general loading case is a combination of longitudinal stress, transverse stress, shear stress and lateral pressure. In this paper, a simplified method is generalized to deal with such combined load cases. The obtained results indicate that the simplified method is able to determine the ultimate strength of unstiffened plates with imperfections in the form of welding induced residual stresses and geometric deflections subjected to combined loads. Comparisons with experimental results show that the procedure has sufficient accuracy for practical applications in design.

  18. Strength development in concrete with wood ash blended cement and use of soft computing models to predict strength parameters.

    Science.gov (United States)

    Chowdhury, S; Maniar, A; Suganya, O M

    2015-11-01

    In this study, Wood Ash (WA) prepared from the uncontrolled burning of the saw dust is evaluated for its suitability as partial cement replacement in conventional concrete. The saw dust has been acquired from a wood polishing unit. The physical, chemical and mineralogical characteristics of WA is presented and analyzed. The strength parameters (compressive strength, split tensile strength and flexural strength) of concrete with blended WA cement are evaluated and studied. Two different water-to-binder ratio (0.4 and 0.45) and five different replacement percentages of WA (5%, 10%, 15%, 18% and 20%) including control specimens for both water-to-cement ratio is considered. Results of compressive strength, split tensile strength and flexural strength showed that the strength properties of concrete mixture decreased marginally with increase in wood ash contents, but strength increased with later age. The XRD test results and chemical analysis of WA showed that it contains amorphous silica and thus can be used as cement replacing material. Through the analysis of results obtained in this study, it was concluded that WA could be blended with cement without adversely affecting the strength properties of concrete. Also using a new statistical theory of the Support Vector Machine (SVM), strength parameters were predicted by developing a suitable model and as a result, the application of soft computing in structural engineering has been successfully presented in this research paper. PMID:26644928

  19. Strength development in concrete with wood ash blended cement and use of soft computing models to predict strength parameters

    Directory of Open Access Journals (Sweden)

    S. Chowdhury

    2015-11-01

    Full Text Available In this study, Wood Ash (WA prepared from the uncontrolled burning of the saw dust is evaluated for its suitability as partial cement replacement in conventional concrete. The saw dust has been acquired from a wood polishing unit. The physical, chemical and mineralogical characteristics of WA is presented and analyzed. The strength parameters (compressive strength, split tensile strength and flexural strength of concrete with blended WA cement are evaluated and studied. Two different water-to-binder ratio (0.4 and 0.45 and five different replacement percentages of WA (5%, 10%, 15%, 18% and 20% including control specimens for both water-to-cement ratio is considered. Results of compressive strength, split tensile strength and flexural strength sho