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

    OpenAIRE

    Mshali, M. R.; Visser, A. T.

    2012-01-01

    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 properties 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 volumetri...

  3. Prediction of the unconfined compressive strength of compacted granular soils by using inference systems

    Science.gov (United States)

    Kalkan, Ekrem; Akbulut, Suat; Tortum, Ahmet; Celik, Samet

    2009-10-01

    Adaptive neuro-fuzzy inference system (ANFIS) and artificial neural network (ANN) models have been extensively used to predict different soil properties in geotechnical applications. In this study, it was aimed to develop ANFIS and ANN models to predict the unconfined compressive strength (UCS) of compacted soils. For this purpose, 84 soil samples with different grain-size distribution compacted at optimum water content were subjected to the unconfined compressive tests to determine their UCS values. Many of the test results (for 64 samples) were used to train the ANFIS and the ANN models, and the rest of the experimental results (for 20 samples) were used to predict the UCS of compacted samples. To train these models, the clay content, fine silt content, coarse silt content, fine sand content, middle sand content, coarse sand content, and gravel content of the total soil mass were used as input data for these models. The UCS values of compacted soils were output data in these models. The ANFIS model results were compared with those of the ANN model and it was seen that the ANFIS model results were very encouraging. Consequently, the results of this study have important findings indicating reliable and simple prediction tools for the UCS of compacted soils.

  4. 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%.

  5. 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.

  6. Preliminary Study of S-Wave Velocity and Unconfined Compressive Strength of Cement- Palf Stabilised Kaolin

    Directory of Open Access Journals (Sweden)

    Chee Ming Chan

    2010-09-01

    Full Text Available Clays are notoriously well known for giving rise to myriad problems and difficulties inconstruction due to excessive settlement and limited strength. Hence, there is a need to pretreatthe soils prior to construction, such as improving the engineering properties via thestabilisation technique, before additional load can be applied on it. In soil stabilisation,cement is commonly used as a stabilizing agent, to simultaneously increase the strength andstiffness of the originally weak, soft material. However cement is relatively expensive andpotentially harmful to the environment when admixed with soils. The need for alternativestabilizing agents which could reduce the use of cement is therefore apparent. In this study,natural fibres were retrieved from pineapple leaves, an agricultural waste product typical ofJohor. Next pre-determined quantities of pineapple leaf fibres (PALF were added to anartificial clay, kaolin, together with cement. The mixture was formed into specimens of 38mm diameter and 76 mm high, cured in dry condition before being subjected to the s-wavevelocity and unconfined strength measurements. A range of curing period was introduced toexamine the effect of time on the performance of the stabilised specimens too. It was foundthat the fibres function as a form of reinforcement to the soil. Also, the test data revealed thatPALF alone makes negligible contribution to the improved properties, where cement isnecessary to act as a binder to strengthen the soil matrix. Nevertheless the potential of usingPALF as an additive to cement in soft soil stabilisation is promising, though further work isnecessary to better understand the stabilised material and its long term performance.

  7. Preliminary Study of S-Wave Velocity and Unconfined Compressive Strength of Cement- Palf Stabilised Kaolin

    OpenAIRE

    Chee Ming Chan; S.S. Ch’ng

    2010-01-01

    Clays are notoriously well known for giving rise to myriad problems and difficulties inconstruction due to excessive settlement and limited strength. Hence, there is a need to pretreatthe soils prior to construction, such as improving the engineering properties via thestabilisation technique, before additional load can be applied on it. In soil stabilisation,cement is commonly used as a stabilizing agent, to simultaneously increase the strength andstiffness of the originally weak, soft materi...

  8. Correlation of slake durability index with unconfined compressive strength estimated through indirect methods for carbonate rocks of salt range, pakistan

    International Nuclear Information System (INIS)

    In evaluation of engineering behavior of rock mass and rock materials, slaking of rocks is an important consideration. For the construction industry, a durable rock is usually preferred. About 75% of the rocks outcropping on continents are sedimentary rocks. To determine rock strength and deformation, direct tests such as uniaxial compressive strength are expensive and require considerable time. Hence there is need to explore relations through other indirect methods such as Slake Durability Index, Point Load Strength and Schmidt rebound hammer test. To investigate the correlation between Slake Durability and strength, multidisciplinary approach was adopted. For this study, one of the important industrial rock groups belonging to carbonate geology of Salt Range was selected. The Slake Durability Index test was performed on 32 rock samples collected from different parts of Salt Range and the test results were compared with indirect strength such as Point Load Strength and Schmidt Hammer Hardness. Data was statistically analyzed through linear regression analysis to determine the correlation coefficient and the variability of results for each test. A strong linear correlation of 1st cycle Slake Durability Index exists with Point Load Strength and Schmidt Hammer Hardness. (author)

  9. 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.

  10. 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

  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. 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...

  13. Analysis of Comparison between Unconfined and Confined Condition of Foamed Concrete Under Uni-Axial Compressive Load

    Directory of Open Access Journals (Sweden)

    Mohd Zairul A. Abdul Rahman

    2010-01-01

    Full Text Available Problem statement: Foamed concrete has become most commercial material in construction industry. People in industries were come out with the new mix design of foamed concrete to meet the specification and the requirements needed. Approach: This is because foamed concrete has the possibility as alternative of lightweight concrete for producing intermediate strength capabilities with excellent thermal insulation, freeze-thaw resistance, high-impact resistance and good shock absorption. Results: Currently Standard test to measure the compressive strength of foamed concrete is using standard unconfined compressive test. Several research has been conduct but the compressive strength using standard unconfined compressive test not capture true behavior of foamed concrete because it just achieved only low compressive strength and sample under compression failed due to brittle collapse of the sample. This paper was analyses the comparison between standard compressive test and confined compressive test. The confinement test introduced to prevent sample from brittle collapse. Foamed concrete cylindrical sample has been investigated under the standard compressive test for hard concrete (ASTM-C39. Based on the research, samples are produced under unconfined and confined condition. Analysis has been done and the result show that under standard compressive test, the sample failed due to early crack initiation and failed. Confinement condition was increase the compressive strength but this condition influence the result. Conclusion/Recommendations: Standard test is not suitable to capture the true behavior of foamed concrete, and to prevent the sample from brittle collapse during the test, new testing method was introduced to capture the true behavior of foamed concrete which is using Quasi Static Indentation Test. This test can be used to study about the behaviour of foamed concrete before it can be implemented to its final application.

  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. Thermo-mechanical cementation effects in bentonite investigated by unconfined compression tests

    International Nuclear Information System (INIS)

    Results from the project LOT showed that specimens exposed to warm conditions had a significantly reduced strain at failure compared to reference material. The objective of the present study was to investigate the impact of parameters such as temperature, density, water content and degree of saturation on the occurrence of brittleness at failure of bentonite specimens. To quantify the influence of the different parameters the unconfined compression test was used on specimens with a height and diameter of 20 mm. In this test the relation between stress and strain is determined from axial compression of a cylindrical specimen. Brittle failure is in this investigation mainly seen on specimens having a density of ? ? 2,060 kg/m3 or on specimens exposed to high temperature T ? 150 deg C in the laboratory. Brittle failure behaviour was also seen on unsaturated specimens with a degree of saturation less than Sr i = 0% before saturation, on specimens with a final degree of saturation of Sr ? 97% and also on one specimen subjected to consolidation during preparation. Brittle failure and reduced strain were noticed in the heated field exposed material in the LOT project. Similar behaviour was also observed in the present short term laboratory tests. However, the specimens in the present study showing this behaviour had higher density, lower degree of saturation or were exposed to higher temperatures than the field exposed specimens

  17. Thermo-mechanical cementation effects in bentonite investigated by unconfined compression tests

    Energy Technology Data Exchange (ETDEWEB)

    Dueck, Ann (Clay Technology AB, Lund (Sweden))

    2010-01-15

    Results from the project LOT showed that specimens exposed to warm conditions had a significantly reduced strain at failure compared to reference material. The objective of the present study was to investigate the impact of parameters such as temperature, density, water content and degree of saturation on the occurrence of brittleness at failure of bentonite specimens. To quantify the influence of the different parameters the unconfined compression test was used on specimens with a height and diameter of 20 mm. In this test the relation between stress and strain is determined from axial compression of a cylindrical specimen. Brittle failure is in this investigation mainly seen on specimens having a density of rho >= 2,060 kg/m3 or on specimens exposed to high temperature T >= 150 deg C in the laboratory. Brittle failure behaviour was also seen on unsaturated specimens with a degree of saturation less than Sr < 90%. Failure at reduced strain was seen in this investigation on specimens exposed to T = 150 deg C, on specimens having a water content of w{sub i} = 0% before saturation, on specimens with a final degree of saturation of S{sub r} <= 97% and also on one specimen subjected to consolidation during preparation. Brittle failure and reduced strain were noticed in the heated field exposed material in the LOT project. Similar behaviour was also observed in the present short term laboratory tests. However, the specimens in the present study showing this behaviour had higher density, lower degree of saturation or were exposed to higher temperatures than the field exposed specimens

  18. The Uniaxial Compressive Strength of Soft Rock

    OpenAIRE

    D S Agustawijaya

    2007-01-01

    Soft rock is a term that usually refers to a rock material with a uniaxial compressive strength (UCS) less than 20 MPa. This low strength range might be influenced by physical characteristics, such as size, saturation, weathering and mineral content. A number of uniaxial compression tests have been conducted onto soft rock samples. The results showed that the strength reduced significantly in saturation. The reduction was also caused by weathering, the strength of distinctly weathered rocks w...

  19. 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...

  20. Compressive Strength of Autoclaved Aerated Concrete Blockwork

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    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.

  1. Compressive Strength of Fibre Reinforced Concrete

    OpenAIRE

    Jelus?ic?, Matjaz?

    2009-01-01

    The thesis features an analysis of the time development of compressive strength of fibre reinforced normal and high strength concrete. Concrete mixtures, taken from the doctoral dissertation of assistant Dr Drago Saje, were used as comparable mixtures to fibre reinforced concrete mixtures with different volume shares of fibres. Two types of steel fibres were used, both featuring the same characteristics but having different lengths (16 and 30 mm), as well as polypropylene fibres. The percenta...

  2. 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.

  3. The region-dependent dynamic properties of porcine temporomandibular joint disc under unconfined compression.

    Science.gov (United States)

    Fernández, Pelayo; Jesús Lamela, María; Ramos, Alberto; Fernández-Canteli, Alfonso; Tanaka, Eiji

    2013-02-22

    In this study, the dynamic compressive properties in five different regions of the porcine temporomandibular joint (TMJ) disc are investigated over a wide range of loading frequencies. The aim was, thus far, to evaluate the regional difference and the frequency-related effect of the applied load on these properties. Eleven porcine TMJ discs were used; each disc was divided into 5 regions, anterior, central, posterior, lateral and medial. Sinusoidal compressive strain was applied with an amplitude of 1.0% and a frequency range between 0.01 and 10Hz. The dynamic storage and loss moduli increase with frequency, the highest values being attained at the posterior region, followed by the central and anterior regions. Loss tangent, tan?, ranged from 0.20 to 0.35, which means that the disc is primarily elastic in nature and has a small but not negligible viscosity. The present results suggest that the dynamic viscoelastic compressive modulus is region-specific and depends on the loading frequency, thus having important implications for the transmission of load to the TMJ. PMID:23261240

  4. Post impact compressive strength in composites

    Science.gov (United States)

    Demuts, Edvins; Sandhu, Raghbir S.; Daniels, John A.

    1992-01-01

    Presented in this paper are the plan, equipment, procedures, and findings of an experimental investigation of the tolerance to low velocity impact of a graphite epoxy (AS4/3501-6) and graphite bismaleimide (M6/CYCOM3100) advanced composites. The applied impacts were governed by the Air Force Guide Specification 87221. Specimens of each material system having a common nominal layup (10% 0 deg; 80% +/-45 deg; 10% 90 deg), a common 7 inch (17.78 cm) by 10 inch (25.40 cm) size, five different thicknesses (9, 26, 48, 74, and 96 plies), and ambient moisture content were impacted and strength tested at room temperature. Damaged areas and post impact compression strengths (PICS) were among the most significant findings obtained. While the undamaged per ply compression strength of both materials is a strong function of laminate thickness, the per ply PICS is not. The average difference in per ply PICS between the two material systems is about seven percent. Although a smaller percentage of the applied kinetic energy was absorbed by the Gr/BMI than by the Gr/Epoxy composites, larger damaged areas were produced in the Gr/BMI than in Gr/Epoxy. Within the limitations of this investigation, the Gr/BMI system seems to offer no advantage in damage tolerance over the Gr/Epoxy system examined.

  5. 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.

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

    OpenAIRE

    Kristiawan, S. A.

    2006-01-01

    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 r...

  7. PHYSICAL BEHAVIOUR OF FOAMED CONCRETE UNDER UNI-AXIAL COMPRESSIVE LOAD: CONFINED COMPRESSIVE TEST

    Directory of Open Access Journals (Sweden)

    Ahmad Mujahid Ahmad Zaidi

    2010-01-01

    Full Text Available Foamed concrete now is a common material used in civil engineering work. There are increasing amount in research where foamed concrete are used primarily to resist compression force. In this research, physical behaviour of foamed concrete was investigated. Based on the past research, the compressive strength of foamed concrete typically proportioned to achieve only low compressive strength in unconfined condition. Standard compressive test were performed to obtain the compressive strength of foamed concrete. In this research, the confined condition is produced. Unconfined condition also was done, but here just focused on confined condition. The confined compressive test method consist of applying a compressive axial load to moulded cylinders at a rate which is within a prescribe range until failure occurs. The physical behaviour of foamed concrete under confined condition is the continuity of unconfined condition and will be the guidance to conduct the further researchKeywords: foamed concrete, confined compressive test, mode of failure

  8. Intelligent Estimation of Compressive Strength of the Pavement Layers Stabilized by the Combination of Bitumen Emulsion and Cement

    Directory of Open Access Journals (Sweden)

    Mehrdad Aryafar

    2008-01-01

    Full Text Available The Application of the different types of additive materials such as lime, cement bitumen and the combination of them are considered as a main issue by the relating experts. In order to promote the bearing capacity of road, these materials, individually, or with the attendance of other materials add to sub base layers. During the recent years, road builders have been considering the application of the combination of bitumen emulsion and cement due to the emergence of the modern equipments and machineries in transportation engineering which have been led to the rapid construction of roads and a uniform combination with the suitable compactness properties in soil stabilization too. The compressive strength which can be determined by the Unconfined Compressive Strength (UCS test is one of the most important factors to control the quality of the stabilized materials using bitumen emulsion and cement and also in order to design them much efficiently. Besides, it is necessary to use an analytical method because the laboratory tests are very expensive and in some cases are not available especially in the projects constructing in the remote areas and also the strong need for controlling the obtained results from the insitu tests. In this study, the application of the inelegant neural network is investigated to estimate the 28 days compressive strength of the samples built from the stabilized materials by the combination of bitumen emulsion and cement. The obtained results show that; artificial neural network is very capable in predicting the 28 days compressive strength.

  9. 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.

  10. 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.

  11. Static strength of gold compressed up to 127 GPa

    International Nuclear Information System (INIS)

    Gold powder is compressed non-hydrostatically up to 127 GPa in a diamond anvil cell (DAC), and its angle dispersive X-ray diffraction patterns are recorded. The compressive strength of gold is investigated in a framework of the lattice strain theory by the line shift analysis. The result shows that the compressive strength of gold increases continuously with the pressure up to 106 GPa and reaches 2.8 GPa at the highest experimental pressure (127 GPa) achieved in our study. This result is in good agreement with our previous experimental result in a relevant pressure range. The compressive strength of gold may be the major source of the error in the equation-of-state measurement in various pressure environments

  12. 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.

  13. Compressive strength of concrete and mortar containing fly ash

    Science.gov (United States)

    Liskowitz, John W. (Belle Mead, NJ); Wecharatana, Methi (Parsippany, NJ); Jaturapitakkul, Chai (Bangkok, TH); Cerkanowicz, deceased, Anthony E. (late of Livingston, NJ)

    1998-01-01

    The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction. The invention includes a method for predicting the compressive strength of such a hardenable mixture, which is very important for planning a project. The invention also relates to hardenable mixtures comprising cement and fly ash which can achieve greater compressive strength than hardenable mixtures containing only concrete over the time period relevant for construction. In a specific embodiment, a formula is provided that accurately predicts compressive strength of concrete containing fly ash out to 180 days. In other specific examples, concrete and mortar containing about 15% to 25% fly ash as a replacement for cement, which are capable of meeting design specification required for building and highway construction, are provided. Such materials can thus significantly reduce construction costs.

  14. 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)

  15. Compressive strength and hydration processes of concrete with recycled aggregates

    International Nuclear Information System (INIS)

    This paper deals with the correlation between the time evolution of the degree of hydration and the compressive strength of Recycled Aggregate Concrete (RAC) for different water to cement ratios and initial moisture conditions of the Recycled Concrete Aggregates (RCAs). Particularly, the influence of such moisture conditions is investigated by monitoring the hydration process and determining the compressive strength development of fully dry or fully saturated recycled aggregates in four RAC mixtures. Hydration processes are monitored via temperature measurements in hardening concrete samples and the time evolution of the degree of hydration is determined through a 1D hydration and heat flow model. The effect of the initial moisture condition of RCAs employed in the considered concrete mixtures clearly emerges from this study. In fact, a novel conceptual method is proposed to predict the compressive strength of RAC-systems, from the initial mixture parameters and the hardening conditions. -- Highlights: •The concrete industry is more and more concerned with sustainability issues. •The use of recycled aggregates is a promising solution to enhance sustainability. •Recycled aggregates affect both hydration processes and compressive strength. •A fundamental approach is proposed to unveil the influence of recycled aggregates. •Some experimental comparisons are presented to validate the proposed approach

  16. 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 properties of concrete in compression. Including the measurement and study of the descending branch, a new experimental method has been used to investigate the influence of boundary conditions, loading rate, size effects and the influence of the strength on the fracture energy of high-strength concrete over the range 70 MPa to 150 MPa, expressed in nominal values.

  17. Insulation interlaminar shear strength testing with compression and irradiation

    International Nuclear Information System (INIS)

    The Compact Ignition Tokamak (CIT) project identified the need for research and development for the insulation to be used in the toroidal field coils. The requirements included tolerance to a combination of high compression and shear and a high radiation dose. Samples of laminate-type sheet material were obtained from commercial vendors. The materials included various combinations of epoxy, polyimide, E-glass, S-glass, and T-glass. The T-glass was in the form of a three-dimensional weave. The first tests were with 50 x 25 x 1 mm samples. These materials were loaded in compression and then to failure in shear. At 345-MPa compression, the interlaminar shear strength was generally in the range of 110 to 140 MPa for the different materials. A smaller sample configuration was developed for irradiation testing. The data before irradiation were similar to those for the larger samples but approximately 10% lower. Limited fatigue testing was also performed by cycling the shear load. No reduction in shear strength was found after 50,000 cycles at 90% of the failure stress. Because of space limitations, only three materials were chosen for irradiation: two polyimide systems and one epoxy system. All used boron-free glass. The small shear/compression samples and some flexure specimens were irradiated to 4 x 109 and 2 x 1010 rad in the Advanced Technology Reactor at Idaho National Engineering Laboratory. A lead shield was used to ensure that the majority of the dose was from neutrons. The shear strength with compression before and after irradiation at the lower dose was determined. Flexure strength and the results from irradiation at the higher dose level will be available in the near future. 7 refs., 7 figs., 2 tabs

  18. Residual Compressive Strength of Laterized Concrete Subjected to Elevated Temperatures

    Directory of Open Access Journals (Sweden)

    Robert M. Brooks

    2010-05-01

    Full Text Available This research presents the results of an experimental program to investigate the strength performance of laterized concrete (LATCON when subjected to elevated temperatures of 200, 400 and 600ºC. Six concrete mixes incorporating 0, 10, 20, 30, 40 and 50% Laterite as a replacement by weight of sand was prepared. After heat pretreatment specimens were cooled using either rapid cooling (water-cooling or natural cooling (air-cooling. An analysis of variance test shows that exposure temperature, cooling regime, and their interaction have a significant influence on the compressive strength of the samples. When subjected to the investigated temperatures specimens experienced strength losses that increased with temperature. This study further reveals that air-cooled concrete specimens maintained higher residual strength values than water-cooled specimens. A comparison of the residual compressive strength data obtained in this study with code provisions in Eurocode and CEB design curve shows that these codes could be applied to LATCON subjected to temperature below 400ºC.

  19. 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.

  20. EFFECT OF HISTOMORPHOMETRIC PARAMETERS ON COMPRESSION STRENGTH OF VERTEBRAL BODIES

    Directory of Open Access Journals (Sweden)

    Artur Gadek

    2011-05-01

    Full Text Available Computer aided image analysis was applied to elaborate an automatic method of histomorphometric analysis of trabecular bone samples. Transverse sections of decalcified vertebral bodies were examined using optical microscopy and digital image acquisition system. Further analysis was done by means of a general purpose image analysis package. The same algorithm was applied to all the images tested, thus enabling obtainment of objective and repeatable results. High efficiency in measurements and evaluation of parameters not accessible for manual methods makes this method an interesting alternative for classical histomorphometric analysis. The results obtained demonstrated that assessment of bone mineral density is not sufficient for evaluation of compression strength of vertebral bodies. In contrast, mechanical properties correlate well with histomorphometric parameters. As a consequence it was postulated that compression strength of vertebral bodies is controlled by trabecular structure rather than bone mineral density.

  1. Compressive strength and durability properties of ceramic wastes based concrete

    OpenAIRE

    Torgal, Fernando Pacheco; Jalali, Said

    2010-01-01

    This paper presents an experimental study on the properties and on the durability of concrete containing ceramic wastes. Several concrete mixes possessing a target mean compressive strength of 30 MPa were prepared with 20% cement replacement by ceramic powder (W/B = 0.6). A concrete mix with ceramic sand and granite aggregates were also prepared as well as a concrete mix with natural sand and coarse ceramic aggregates (W/B = 0.5). The mechanical and durability performance of ceramic ...

  2. Compression Strength of Sulfur Concrete Subjected to Extreme Cold

    Science.gov (United States)

    Grugel, Richard N.

    2008-01-01

    Sulfur concrete cubes were cycled between liquid nitrogen and room temperature to simulate extreme exposure conditions. Subsequent compression testing showed the strength of cycled samples to be roughly five times less than those non-cycled. Fracture surface examination showed de-bonding of the sulfur from the aggregate material in the cycled samples but not in those non-cycled. The large discrepancy found, between the samples is attributed to the relative thermal properties of the materials constituting the concrete.

  3. Estimating compressive strength of concrete by mortar testing

    OpenAIRE

    Camo?es, Aires; Aguiar, J. L. Barroso; Jalali, Said

    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...

  4. Strength Tests of Thin-Walled Duralumin Cylinders in Compression

    Science.gov (United States)

    Lundquist, Eugene E

    1934-01-01

    This report is the second of a series presenting the results of strength tests of thin-walled duralumin cylinders and truncated cones of circular and elliptic section. It contains the results obtained from compression tests on 45 thin-walled duralumin cylinders of circular section with ends clamped to rigid bulkheads. In addition to the tests on duralumin cylinders, there are included the results of numerous tests on rubber, celluloid, steel, and brass cylinders obtained from various sources.

  5. The compressive strength of duralumin columns of equal angle section

    Science.gov (United States)

    Lundquist, Eugene E

    1932-01-01

    This report presents a chart giving the compressive strength of duralumin columns of equal angle section. The data used in the construction of the chart were obtained from various published sources and were correlated with theory in the range where secondary failure occurred. Appendices are included giving excerpts from Army and Navy specifications for duralumin and approximate formulas for the properties of the equal angle section.

  6. 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...

  7. Effect of aluminum oxide on the compressive strength of pellets

    Science.gov (United States)

    Zhang, Jian-liang; Wang, Zhen-yang; Xing, Xiang-dong; Liu, Zheng-jian

    2014-04-01

    Analytical-reagent-grade Al2O3 was added to magnetite ore during the process of pelletizing, and the methods of mercury intrusion, scanning electron microscopy, and image processing were used to investigate the effect of Al2O3 on the compressive strength of the pellets. The results showed that, as the Al2O3 content increased, the compressive strength of the pellets increased slightly and then decreased gradually. When a small amount of Al2O3 was added to the pellets, the Al2O3 combined with fayalite (2FeO·SiO2) and the aluminosilicate (2FeO·2Al2O3·5SiO2) was generated, which releases some iron oxide and reduces the inhibition of fayalite to the solid phase of consolidation. When Al2O3 increased sequentially, high melting point of Al2O3 particles hinder the oxidation of Fe3O4 and the recrystallization of Fe2O3, making the internal porosity of the pellets increase, which leads to the decrease in compressive strength of the pellets.

  8. 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.

  9. Flow strength of tantalum under ramp compression to 250?GPa

    International Nuclear Information System (INIS)

    A magnetic loading technique was used to study the strength of polycrystalline tantalum ramp compressed to peak stresses between 60 and 250?GPa. Velocimetry was used to monitor the planar ramp compression and release of various tantalum samples. A wave profile analysis was then employed to determine the pressure-dependence of the average shear stress upon unloading at strain rates on the order of 105?s?1. Experimental uncertainties were quantified using a Monte Carlo approach, where values of 5% in the estimated pressure and 9–17% in the shear stress were calculated. The measured deviatoric response was found to be in good agreement with existing lower pressure strength data as well as several strength models. Significant deviations between the experiments and models, however, were observed at higher pressures where shear stresses of up to 5?GPa were measured. Additionally, these data suggest a significant effect of the initial material processing on the high pressure strength. Heavily worked or sputtered samples were found to support up to a 30% higher shear stress upon release than an annealed material

  10. Toroidal, compression, and vortical dipole strengths in 124Sn

    CERN Document Server

    Kvasil, J; Repko, A; Kleinig, W; Reinhard, P -G; Iudice, N Lo

    2012-01-01

    The toroidal, compression and vortical dipole strength functions in semi-magic $^{124}$Sn (and partly in doubly-magic $^{100,132}$Sn) are analyzed within the random-phase-approximation method with the SkT6, SkI3, SLy6, SV-bas, and SkM* Skyrme forces. The isoscalar (T=0), isovector (T=1), and electromagnetic ('elm') channels are considered. Both convection $j_c$ and magnetization $j_m$ nuclear currents are taken into account. The calculations basically confirm the previous results obtained for $^{208}$Pb with the force SLy6. In particular, it is shown that the vortical and toroidal strengths are dominated by $j_c$ in T=0 channel and by $j_m$ in T=1 and 'elm' channels. The compression strength is always determined by $j_c$. It is also shown that the 'elm' strength (relevant for (e,e') reaction) is very similar to T=1 one. The toroidal mode resides in the region of the pygmy resonance. So, perhaps, this region embraces both irrotational (pygmy) and vortical (toroidal) flows.

  11. Toroidal, compression and vortical dipole strengths in 124Sn

    International Nuclear Information System (INIS)

    The toroidal, compression and vortical dipole strength functions in semi-magic 124Sn (and partly in doubly magic 100,132Sn) are analyzed within the random-phase-approximation method with the SkT6, SkI3, SLy6, SV-bas and SkM* Skyrme forces. The isoscalar (T = 0), isovector (T = 1) and electromagnetic (‘elm’) channels are considered. Both convection jc and magnetization jm nuclear currents are taken into account. The calculations basically confirm the previous results obtained for 208Pb with the force SLy6. In particular, it is shown that the vortical and toroidal strengths are dominated by jc in the T = 0 channel and by jm in the T = 1 and ‘elm’ channels. The compression strength is always determined by jc. It is also shown that the ‘elm’ strength (relevant for the (e,e?) reaction) is very similar to the T = 1 one. The toroidal mode resides in the region of the pygmy resonance. So, perhaps, this region embraces both irrotational (pygmy) and vortical (toroidal) flows. (paper)

  12. 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

  13. 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

  14. Compressive strength test for cemented waste forms: validation process

    International Nuclear Information System (INIS)

    In the Cementation Laboratory (LABCIM), of the Development Centre of the Nuclear Technology (CNEN/CDTN-MG), hazardous/radioactive wastes are incorporated in cement, to transform them into monolithic products, preventing or minimizing the contaminant release to the environment. The compressive strength test is important to evaluate the cemented product quality, in which it is determined the compression load necessary to rupture the cemented waste form. In LABCIM a specific procedure was developed to determine the compressive strength of cement waste forms based on the Brazilian Standard NBR 7215. The accreditation of this procedure is essential to assure reproductive and accurate results in the evaluation of these products. To achieve this goal the Laboratory personal implemented technical and administrative improvements in accordance with the NBR ISO/IEC 17025 standard 'General requirements for the competence of testing and calibration laboratories'. As the developed procedure was not a standard one the norm ISO/IEC 17025 requests its validation. There are some methodologies to do that. In this paper it is described the current status of the accreditation project, especially the validation process of the referred procedure and its results. (author)

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

    OpenAIRE

    Nazari, A.; 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 ...

  16. The Effects of Compressive Preloads on the Compression-After-Impact Strength of Carbon/Epoxy

    Science.gov (United States)

    Nettles, Alan T.

    1994-01-01

    A fixture to apply compressive loads to composite specimens during an impact event was used to assess the effect of prestresses on the compression-after-impact (CAI) strength of 16 ply quasi-isotropic carbon/epoxy test coupons. Advanced design of experiments techniques were used to evaluate a range of prestresses and impact energies on two material systems, T300/934 and IM7/8551-7. An instrumented drop tower supplied impact energies between 1 and 9 Joules for the T300/934 material and between 4 and 16 Joules for the IM7/8551-7 material. The prestress values varied between a low of 5.7 Wa and a high of 287 NDa. Results showed some change in CAI strength that could be attributed to the prestresses on the specimens.

  17. 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.

    1077-10-01

    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.

  18. 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

  19. Investigation of Salinity Effect on Compressive Strength of Reinforced Concrete

    Directory of Open Access Journals (Sweden)

    Akinsola Olufemi Emmanuel

    2012-05-01

    Full Text Available This study adopt laboratory controlled experiment approach, in order to induce the worst scenario of concrete mix and determine the consequent effect on reinforced concrete element; a mix ratio of 1:3:6 was adopted for the experiment. Reinforced concrete elements were cast using both lagoon and ocean water while fresh water was used as a control experiment. These samples were buried at a depth of 1.5m below the ocean and lagoon bed soil characteristics and observed for a period of 150 days. Both the ocean and the lagoon samples increases in compressive strength from 10.65N/mm2 and 10.57N/mm2 on 7th day to 17.05N/mm2 and 18.04N/mm2 on the 21st day respectively as against the 14.20N/mm2 on 7th day to 17.05N/mm2 and 18.04N/mm2 fresh water sample. On 14th day fresh water sample has 17.48N/mm2 as against 12.10N/mm2 and 12.55N/mm2 recorded for both ocean and lagoon water samples. The findings revealed that concrete sample cast and cured with fresh water gained appreciable compressive strength over 150 days period while sample cast and cured with ocean and lagoon water slowly increase in strength but lower when compared with fresh water reinforced concrete element. Therefore the study recommended that a rich mix other than 1:3:6 and 1:3:5 be strictly enforced on construction sites for concrete under saline attack, increase concrete cover be used for protection against corrosion, and that non destructive test be carried out on all formworks under vertical loads like slabs and beams before they are stripped.

  20. 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.

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

    Directory of Open Access Journals (Sweden)

    Abdoullah Namdar

    2014-02-01

    Full Text Available 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 of concrete. The cellulose-Ibeta presences in saw dust, has been modified the surface roughness and hydration of OPC paste, and leads to enhancement of compressive strength of concrete. The compressive strength of OPC paste has been stabilized with increase of age, due to pozzolanic actions. The compressive strength of OPC has been decreased with increase sawdust contents.

  2. Developing an artificial neural network model for predicting concrete’s compression strength and electrical resistivity

    OpenAIRE

    Juan Manuel Lizarazo Marriaga; José Gabriel Gómez Cortés

    2010-01-01

    The present study was conducted for predicting the compressive strength of concrete based on unit weight ultrasonic and pulse velocity (UPV) for 41 different concrete mixtures. This research emerged from the need for a rapid test for predicting concrete’s compressive strength. The research was also conducted for predicting concrete’s electrical resistivity based on unit weight ultrasonic, pulse velocity (UPV) and compressive strength with the same mixes. The prediction was made using sim...

  3. Test results and model for the residual compressive strength of concrete after a fire

    OpenAIRE

    Li, Yi-hai; Franssen, Jean-marc

    2011-01-01

    An investigation into temperature induced degradation of the compressive strength of concrete including that under cooling phase is carried out. The paper gathers and reviews a considerable amount of test data, considering the influence of different test parameters such as initial compressive strength, aggregate type, cooling regime and specimen shape. It is found that the compressive strength of concrete at high temperature is in accordance with the model proposed in the Eurocodes for calcar...

  4. The Analysis of Methodologies for Testing Compressive Strength in Masonry Mortar Joints

    Directory of Open Access Journals (Sweden)

    Tomas Šlivinskas

    2014-12-01

    Full Text Available The article analyzes masonry as composite material and presents the factors that affect the mechanical characteristics of masonry. The article also deals with the most frequently used destructive and non-destructive testing methods for the compressive strength of masonry mortar as well as related advantages and disadvantages. Moreover, the analysis of methods for testing ultrasonic waves has been carried out. The article reveals that for using the methodology of testing a mortar bonded wafer, the compressive strength correlation of masonry mortar is set between the ascertainment of masonry mortar strength using a regular mortar testing methodology (LST EN 1015-11:2004 and the compressive strength of mortar possibly taken from masonry joints. The obtained results of an experimental study on the samples have demonstrated that the strength reduction ratio of masonry mortar depends on the compressive strength of mortar. The value of the ratio is increasing with the descending compressive strength of mortar.

  5. 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.

  6. Compressive strength after blast of sandwich composite materials

    Science.gov (United States)

    Arora, H.; Kelly, M.; Worley, A.; Del Linz, P.; Fergusson, A.; Hooper, P. A.; Dear, J. P.

    2014-01-01

    Composite sandwich materials have yet to be widely adopted in the construction of naval vessels despite their excellent strength-to-weight ratio and low radar return. One barrier to their wider use is our limited understanding of their performance when subjected to air blast. This paper focuses on this problem and specifically the strength remaining after damage caused during an explosion. Carbon-fibre-reinforced polymer (CFRP) composite skins on a styrene–acrylonitrile (SAN) polymer closed-cell foam core are the primary composite system evaluated. Glass-fibre-reinforced polymer (GFRP) composite skins were also included for comparison in a comparable sandwich configuration. Full-scale blast experiments were conducted, where 1.6×1.3?m sized panels were subjected to blast of a Hopkinson–Cranz scaled distance of 3.02?m?kg?1/3, 100?kg TNT equivalent at a stand-off distance of 14?m. This explosive blast represents a surface blast threat, where the shockwave propagates in air towards the naval vessel. Hopkinson was the first to investigate the characteristics of this explosive air-blast pulse (Hopkinson 1948 Proc. R. Soc. Lond. A 89, 411–413 (doi:10.1098/rspa.1914.0008)). Further analysis is provided on the performance of the CFRP sandwich panel relative to the GFRP sandwich panel when subjected to blast loading through use of high-speed speckle strain mapping. After the blast events, the residual compressive load-bearing capacity is investigated experimentally, using appropriate loading conditions that an in-service vessel may have to sustain. Residual strength testing is well established for post-impact ballistic assessment, but there has been less research performed on the residual strength of sandwich composites after blast. PMID:24711494

  7. Compressive strength after blast of sandwich composite materials.

    Science.gov (United States)

    Arora, H; Kelly, M; Worley, A; Del Linz, P; Fergusson, A; Hooper, P A; Dear, J P

    2014-05-13

    Composite sandwich materials have yet to be widely adopted in the construction of naval vessels despite their excellent strength-to-weight ratio and low radar return. One barrier to their wider use is our limited understanding of their performance when subjected to air blast. This paper focuses on this problem and specifically the strength remaining after damage caused during an explosion. Carbon-fibre-reinforced polymer (CFRP) composite skins on a styrene-acrylonitrile (SAN) polymer closed-cell foam core are the primary composite system evaluated. Glass-fibre-reinforced polymer (GFRP) composite skins were also included for comparison in a comparable sandwich configuration. Full-scale blast experiments were conducted, where 1.6×1.3?m sized panels were subjected to blast of a Hopkinson-Cranz scaled distance of 3.02?m?kg(-1/3), 100?kg TNT equivalent at a stand-off distance of 14?m. This explosive blast represents a surface blast threat, where the shockwave propagates in air towards the naval vessel. Hopkinson was the first to investigate the characteristics of this explosive air-blast pulse (Hopkinson 1948 Proc. R. Soc. Lond. A 89, 411-413 (doi:10.1098/rspa.1914.0008)). Further analysis is provided on the performance of the CFRP sandwich panel relative to the GFRP sandwich panel when subjected to blast loading through use of high-speed speckle strain mapping. After the blast events, the residual compressive load-bearing capacity is investigated experimentally, using appropriate loading conditions that an in-service vessel may have to sustain. Residual strength testing is well established for post-impact ballistic assessment, but there has been less research performed on the residual strength of sandwich composites after blast. PMID:24711494

  8. 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)

  9. 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.

  10. 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%.

  11. Effect of Copper Content on Compressive Strength and Microstructure of Dental Amalgams

    Directory of Open Access Journals (Sweden)

    Seyed Abdolkarim Sajjadi

    2012-03-01

    Full Text Available The main goal of this research is to investigate the effect of copper on compressive strength of dental amalgam. For this purpose amalgam capsules with two different content of copper were used. Cylindrical samples with diameter to height ratio 1 to 2, were prepared via molding method. To evaluate the role of copper element on compressive strength, com-pression test was done at different strain rates i.e. 0.02, 0.2, 0.4 and 2 min–1. The results and microscopic evaluations showed that an increase in copper content in amalgam caused to eliminate gamma2 phase and leaded to promote compressive strength.

  12. Effect of size and shape of specimen on compressive strength of glass fiber reinforced concrete (GFRC

    Directory of Open Access Journals (Sweden)

    Krishna Rao M.V.

    2011-01-01

    Full Text Available Concrete is a versatile material with tremendous applications in civil engineering construction. Structural concrete elements are generally made with concrete having a compressive strength of 20 to 35 MPa. Lately, there is an increase in use of high strength concrete (HSC in major construction projects such as high-rise buildings, and bridges involving members of different sizes and shapes. The compressive strength of concrete is used as the most basic and important material property in the design of reinforced concrete structures. It has become a problem to use this value as the control specimen sizes and shapes are different from country to country. In India, the characteristic compressive strength is usually measured based on 150 mm cubes [1]. But, the ACI code of practice specifies the design compressive strength based on the standard 150x300 mm cylinders [2]. The use of 100x200 mm cylinders gained more acceptance as the need to test high strength concrete increases [3]. In this context the size and shape of concrete becomes an important parameter for the compressive strength. In view of the significance of compressive strength of concrete and due to the fact that the structural elements of different sizes and shapes are used, it is proposed to investigate the effect of size and shape of the specimen on the compressive strength of concrete. In this work, specimens of plain as well as Glass Fiber Reinforced Concrete (GFRC specimens are cast in order to carry out a comparative study.

  13. Estimate of Compressive Strength for Concrete using Ultrasonics by Multiple Regression Analysis Method

    International Nuclear Information System (INIS)

    Various types of ultrasonic techniques have been used for the estimation of compressive strength of concrete structures. However, conventional ultrasonic velocity method using only longitudial wave cannot be determined the compressive strength of concrete structures with accuracy. In this paper, by using the introduction of multiple parameter, e. g. velocity of shear wave, velocity of longitudinal wave, attenuation coefficient of shear wave, attenuation coefficient of longitudinal wave, combination condition, age and preservation method, multiple regression analysis method was applied to the determination of compressive strength of concrete structures. The experimental results show that velocity of shear wave can be estimated compressive strength of concrete with more accuracy compared with the velocity of longitudinal wave, accuracy of estimated error range of compressive strength of concrete structures can be enhanced within the range of ± 10% approximately

  14. 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

  15. 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.

  16. 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.

  17. The estimation of compressive strength of normal and recycled aggregate concrete

    OpenAIRE

    Jankovi? Ksenija; Nikoli? Dragan; Bojovi? Dragan; Lon?ar Ljiljana; Romakov Zoran

    2011-01-01

    Estimation of concrete strength is an important issue in ready-mixed concrete industry, especially, in proportioning new mixtures and for the quality assurance of the concrete produced. In this article, on the basis of the existing experimental data of compressive strength of normal and recycled aggregate concrete and equation for compressive strength calculating given in Technical regulation are compared. The accuracies of prediction by experimental data obtained in laboratory as well ...

  18. Effect of size and shape of specimen on compressive strength of glass fiber reinforced concrete (GFRC)

    OpenAIRE

    Krishna Rao M.V.; Kumar Rathish P.; Srinivas B

    2011-01-01

    Concrete is a versatile material with tremendous applications in civil engineering construction. Structural concrete elements are generally made with concrete having a compressive strength of 20 to 35 MPa. Lately, there is an increase in use of high strength concrete (HSC) in major construction projects such as high-rise buildings, and bridges involving members of different sizes and shapes. The compressive strength of concrete is used as the most basic and important material property in the ...

  19. 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.

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

    OpenAIRE

    Ju?lio, Eduardo N. B. S.; Branco, Fernando A. B.; Silva, Vi?tor D.; Lourenc?o, 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 ...

  1. Compressive epitactic layers on single-crystal components for improved mechanical durability and strength

    International Nuclear Information System (INIS)

    Compressive epitactic layers grown on single-crystal substrates are shown to substantially improve mechanical durability. In this study, neodymium-substituted gadolinium gallium garnet (GGG) layers are grown on undoped GGG substrates. The layers are found to dramatically improve the abrasion resistance of the substrates, but to have only a slight effect on strength. Abrasion treatments, which cause up to 20 times decrease in the strength of substrates without epitactic layers, do not cause a significant decrease in the strength of substrates with these compressive surface layers. This permits the high strength of specially prepared strong substrates to be retained after abrasion

  2. 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.

  3. Compressive strength, chloride permeability, and freeze-thaw resistance of MWNT concretes under different chemical treatments.

    Science.gov (United States)

    Wang, Xingang; Rhee, Inkyu; Wang, Yao; Xi, Yunping

    2014-01-01

    This study investigated compressive strength, chloride penetration, and freeze-thaw resistance of multiwalled carbon nanotube (MWNT) concrete. More than 100 cylindrical specimens were used to assess test variables during sensitivity observations, including water-cement ratios (0.75, 0.5, and 0.4) and exposure to chemical agents (including gum arabic, propanol, ethanol, sodium polyacrylate, methylcellulose, sodium dodecyl sulfate, and silane). To determine the adequate sonication time for MWNT dispersal in water, the compressive strengths of MWNT concrete cylinders were measured after sonication times ranging from 2 to 24 minutes. The results demonstrated that the addition of MWNT can increase the compressive strength of concrete by up to 108%. However, without chemical treatment, MWNT concretes tend to have poor freeze-thaw resistance. Among the different chemical treatments, MWNT concrete treated with sodium polyacrylate has the best compressive strength, chloride resistance, and freeze-thaw durability. PMID:25140336

  4. 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...

  5. Hydraulic efficiency compromises compression strength perpendicular to the grain in Norway spruce trunkwood

    OpenAIRE

    ROSNER, SABINE; KARLSSON, BO

    2011-01-01

    The aim of this study was to investigate bending stiffness and compression strength perpendicular to the grain of Norway spruce (Picea abies (L.) Karst.) trunkwood with different anatomical and hydraulic properties. Hydraulically less safe mature sapwood had bigger hydraulic lumen diameters and higher specific hydraulic conductivities than hydraulically safer juvenile wood. Bending stiffness (MOE) was higher, whereas radial compression strength lower in mature than in juvenile wood. A density...

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

    OpenAIRE

    Abiodun Olanipekun; Olugbenga Ata; Kolapo Olusola; Oludare Omojola

    2007-01-01

    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 dec...

  7. The Effects of Different Curing Methods on the Compressive Strength of Terracrete

    OpenAIRE

    O. Alake; J. A. Ayangade; A. B. Wahab

    2009-01-01

    This research evaluated the effects of different curing methods on the compressive strength of terracrete. Several tests that included sieve analysis were carried out on constituents of terracrete (granite and laterite) to determine their particle size distribution and performance criteria tests to determine compressive strength of terracrete cubes for 7 to 35 days of curing. Sand, foam-soaked, tank and open methods of curing were used and the study was carried out under controlled temperatur...

  8. 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...

  9. Point load test application for estimating compressive strength of concrete structures from small core

    OpenAIRE

    A. Zacoeb; Ishibashi, K

    2009-01-01

    To estimate a compressive strength from existing concrete structures by core drilling are usually gathered with a diameter specimen of 100mm or three times of maximum coarse aggregate size and examined by uniaxial compressive strength (UCS) test as stated in JIS A1170. To get an alternative solution with smaller specimen, point load test (PLT) has been selected which is a simple test and widely accepted in rock materials research, but relatively new in concrete. The reliability of PLT is exam...

  10. Estimation of compressive strength of fresh-concrete by using ultrasonic wave propagation velocity

    International Nuclear Information System (INIS)

    The purpose of this work is to give the correlation between ultrasonic wave propagation velocity of fresh concrete and compressive strength of concrete after a age of few days. The ultrasonic wave velocity was measured by using pulse transmission method, and the compressive strength of concrete after 3, 7, and 28 days were measured. For reducing cost, we newly made equipment of measuring the velocity. As results of experiments, regressive equations of which average reliability was about 80%, were proposed.

  11. Correlation between Compressive Strength and Rheological Parameters of High-Performance Concrete

    OpenAIRE

    Sudip Talukdar; Aminul Islam Laskar

    2007-01-01

    Compressive strength is greatly influenced by the performance of concrete in its fresh stage such as uniform mixing, proper compaction, resistance to segregation during transporting and placing. Attempt has, therefore, been made to correlate compressive strength to the rheological behavior of high performance concrete with a modified setup of parallel plate rheometer. Modified setup considers the shearing of concrete at the centre of the cylindrical container that takes into account the resis...

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

    OpenAIRE

    Martins, Francisco F.; Camo?es, 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...

  13. 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)

  14. Estimating the concrete compressive strength using hard clustering and fuzzy clustering based regression techniques.

    Science.gov (United States)

    Nagwani, Naresh Kumar; Deo, Shirish V

    2014-01-01

    Understanding of the compressive strength of concrete is important for activities like construction arrangement, prestressing operations, and proportioning new mixtures and for the quality assurance. Regression techniques are most widely used for prediction tasks where relationship between the independent variables and dependent (prediction) variable is identified. The accuracy of the regression techniques for prediction can be improved if clustering can be used along with regression. Clustering along with regression will ensure the more accurate curve fitting between the dependent and independent variables. In this work cluster regression technique is applied for estimating the compressive strength of the concrete and a novel state of the art is proposed for predicting the concrete compressive strength. The objective of this work is to demonstrate that clustering along with regression ensures less prediction errors for estimating the concrete compressive strength. The proposed technique consists of two major stages: in the first stage, clustering is used to group the similar characteristics concrete data and then in the second stage regression techniques are applied over these clusters (groups) to predict the compressive strength from individual clusters. It is found from experiments that clustering along with regression techniques gives minimum errors for predicting compressive strength of concrete; also fuzzy clustering algorithm C-means performs better than K-means algorithm. PMID:25374939

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

    DEFF Research Database (Denmark)

    Svinning, K.; HØskuldsson, Agnar

    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 and 28 days of 93%, 90%, 79% and 67%, respectively. The high explained variance makes the prediction of the compressive strength up to 28 days from the characteristics reliable. The prediction ability makes it possible in this case to predict strength from cement characteristics and vice versa. Such a prediction can be utilized to design a cement to achieve target strength performance.

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

    DEFF Research Database (Denmark)

    Svinning, K.; HØskuldsson, Agnar

    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 potential compressive strength of clinker up to 28 d from the observed variation in the mineralogy gave a significant variation of the strength at both 1 and 28 d. Sensitivity analysis based on simulation, optimisation and prediction made it possible to study the influence of the mineralogy on the strength in more detail.

  17. 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.

  18. Fracture Energy of High-Strength Concrete in Compression

    OpenAIRE

    Dahl, H.; Brincker, Rune

    2005-01-01

    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...

  19. Influence of Compression and Shear on the Strength of Composite Laminates with Z-Pinned Reinforcement

    Science.gov (United States)

    O'Brien, T. Kevin; Krueger, Ronald

    2005-01-01

    The influence of compression and shear loads on the strength of composite laminates with z-pins is evaluated parametrically using a 2D Finite Element Code (FLASH) based on Cosserat couple stress theory. Meshes were generated for three unique combinations of z-pin diameter and density. A laminated plate theory analysis was performed on several layups to determine the bi-axial stresses in the zero degree plies. These stresses, in turn, were used to determine the magnitude of the relative load steps prescribed in the FLASH analyses. Results indicated that increasing pin density was more detrimental to in-plane compression strength than increasing pin diameter. Compression strengths of lamina without z-pins agreed well with a closed form expression derived by Budiansky and Fleck. FLASH results for lamina with z-pins were consistent with the closed form results, and FLASH results without z-pins, if the initial fiber waviness due to z-pin insertion was added to the fiber waviness in the material to yield a total misalignment. Addition of 10% shear to the compression loading significantly reduced the lamina strength compared to pure compression loading. Addition of 50% shear to the compression indicated shear yielding rather than kink band formation as the likely failure mode. Two different stiffener reinforced skin configurations with z-pins, one quaiisotropic and one orthotropic, were also analyzed. Six unique loading cases ranging from pure compression to compression plus 50% shear were analyzed assuming material fiber waviness misalignment angles of 0, 1, and 2 degrees. Compression strength decreased with increased shear loading for both configurations, with the quasi-isotropic configuration yielding lower strengths than the orthotropic configuration.

  20. Compressive strength of composites: How to measure it and how to improve it

    International Nuclear Information System (INIS)

    The compressive strength of unidirectional fiber composites is an important parameter but is nevertheless much misunderstood. The authors can neither agree on how to measure it, nor what are the physical processes that give rise to it. It is important because it provides a limiting design criterion. Furthermore, the authors cannot start to understand the compressive failure of more complex laminates until the authors understand that of the simplest, i.e. unidirectional laminate. This paper discusses both problems, suggests solutions, and makes recommendations on how to obtain the best compressive strength

  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 strengion 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. Compressive Strength of Volcanic Ash/Ordinary Portland Cement Laterized Concrete

    OpenAIRE

    Olusola K. O.; Olawuyi B.J.

    2010-01-01

    This study investigates the effect of partial replacement of cement with volcanic ash (VA) on the compressive strength of laterized concrete. A total of 192 cubes of 150mm dimensions were cast and cured in water for 7, 14, 21, and 28 days of hydration with cement replacement by VA and sand replacement by laterite both ranging from 0 to 30% respectively, while a control mix of 28-day target strength of 25 N/mm2 was adopted. The results show that the density and compressive strength of concrete...

  4. 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.

  5. Effect of specimen sizes, specimen shapes, and placement directions on compressive strength of concrete

    International Nuclear Information System (INIS)

    The compressive strength of concrete is used as the most basic and important material property when reinforced concrete structures are designed. It has become a problem to use this value, however, because the control specimen sizes and shapes may be different from country to country. In this study, the effect of specimen sizes, specimen shapes, and placement directions on compressive strength of concrete specimens was experimentally investigated based on fracture mechanics. Experiments for the Mode I failure were carried out by using cylinder, cube, and prism specimens. The test results are curve-fitted using least square method (LSM) to obtain the new parameters for the modified size effect law (MSEL). The analysis results show that the effect of specimen sizes, specimen shapes, and placement directions on ultimate strength is present. In addition, correlations between compressive strengths with size, shape, and placement direction of the specimen are investigated

  6. The estimation of compressive strength of normal and recycled aggregate concrete

    Directory of Open Access Journals (Sweden)

    Jankovi? Ksenija

    2011-01-01

    Full Text Available Estimation of concrete strength is an important issue in ready-mixed concrete industry, especially, in proportioning new mixtures and for the quality assurance of the concrete produced. In this article, on the basis of the existing experimental data of compressive strength of normal and recycled aggregate concrete and equation for compressive strength calculating given in Technical regulation are compared. The accuracies of prediction by experimental data obtained in laboratory as well as by EN 1992-1-1, ACI 209 and SRPS U.M1.048 are compared on the basis of the coefficient of determination. The determination of the compressive strengths by the equation described here relies on determination of type of cement and age of concrete with the constant curing temperature.

  7. Compressive strength after blast of sandwich composite materials

    OpenAIRE

    Arora, H.; Kelly, M.; Worley, A; Del Linz, P.; Fergusson, A.; Hooper, P. A.; Dear, J. P.

    2014-01-01

    Composite sandwich materials have yet to be widely adopted in the construction of naval vessels despite their excellent strength-to-weight ratio and low radar return. One barrier to their wider use is our limited understanding of their performance when subjected to air blast. This paper focuses on this problem and specifically the strength remaining after damage caused during an explosion. Carbon-fibre-reinforced polymer (CFRP) composite skins on a styrene–acrylonitrile (SAN) polymer closed...

  8. Evaluation for mechanical properties of gravelly rock. A proposal of evaluation of strength of gravelly rock based on bond strength between gravel and matrix

    International Nuclear Information System (INIS)

    The purpose of this research is to investigate the evaluation method of strength characteristics of gravelly rock. Unconfined compression tests were conducted on three types of artificial gravelly rocks, and box shear tests were performed on the boundary of the gravel and the matrix materials. The results demonstrated that the influence of the bond strength between gravel and matrix was significant on strength of gravelly rocks. Therefore, a simple model was proposed for evaluating strength of gravelly rock based on bond strength between gravel and matrix. The results of unconfined compression tests using artificial and natural gravelly rock samples proved that the proposed model was suitable except the case where the strength ratio of gravel and matrix exceeded 100. (author)

  9. Effect of angle-ply orientation on compression strength of composite laminates

    Energy Technology Data Exchange (ETDEWEB)

    DeTeresa, S J; Hoppel, C P

    1999-03-01

    An experimental program was initiated to investigate the effect of angle-ply orientations on the compressive strength (X{sub 1C}) of 0{degree} plies in fiber reinforced composite laminates. Graphite fiber-reinforced epoxy test coupons with the generic architecture [0{sub 2}/{+-}{theta}] (where {theta} varied between 0{degree} and 90{degree}) and for the quasi-isotropic architecture were evaluated. The effective compressive strength of the 0{degree} plies varied considerably. The results were related to the Poisson's ratios of the laminates with high Poisson's ratios leading to high transverse tensile strains in the test coupons and lower than expected strengths. Specimens with the [O{sub 2}/{+-}30] architecture had both the highest Poisson's ratio and the lowest calculated ply-level compression strength for the 0{degree} plies. This work has implications in the selection of composite failure criterion for compression performance, design of test coupons for acceptance testing, and the selection of laminate architectures for optimum combinations of compressive and shear behavior. Two commonly used composite failure criteria, the maximum stress and the Tsai-Wu, predict significantly different laminate strengths depending on the Poisson's ratio of the laminate. This implies that the biaxial stress state in the laminate needs to be carefully considered before backing out unidirectional properties.

  10. Relationships between microfibril angle, modulus of elasticity and compressive strength in Eucalyptus wood

    Scientific Electronic Library Online (English)

    Paulo Ricardo, Gherardi Hein; José, Tarcísio Lima.

    2012-11-01

    Full Text Available Many traits are known to be important in determining the value of Eucalyptus wood as sawn timber. The commercial importance of the microfibril angle (MFA) for wood quality is well established for a range of softwoods, but is less clear for hardwood species. For instance, the relationships of MFA wit [...] h wood stiffness and compressive strength are unknown in Eucalyptus. Therefore, the aim of this study was to evaluate the correlation between MFA and the modulus of elasticity (Ec0,m) in compression parallel to grain and compressive strength (Fc0,k) using juvenile wood of Eucalyptus grandis from fast-growing plantations. The correlation between wood stiffness and compressive strength was high (0.91). The cellulose microfibril angle presented a correlation of -0.67 with wood stiffness and of -0.52 with compressive strength in Eucalyptus juvenile wood. MFA was found to be important in determining the mechanical behaviour of wood and appears to be a useful parameter to indicate wood stiffness and strength in juvenile Eucalyptus from short-rotation plantations.

  11. Relationships between microfibril angle, modulus of elasticity and compressive strength in Eucalyptus wood

    Directory of Open Access Journals (Sweden)

    Paulo Ricardo Gherardi Hein

    2012-11-01

    Full Text Available Many traits are known to be important in determining the value of Eucalyptus wood as sawn timber. The commercial importance of the microfibril angle (MFA for wood quality is well established for a range of softwoods, but is less clear for hardwood species. For instance, the relationships of MFA with wood stiffness and compressive strength are unknown in Eucalyptus. Therefore, the aim of this study was to evaluate the correlation between MFA and the modulus of elasticity (Ec0,m in compression parallel to grain and compressive strength (Fc0,k using juvenile wood of Eucalyptus grandis from fast-growing plantations. The correlation between wood stiffness and compressive strength was high (0.91. The cellulose microfibril angle presented a correlation of -0.67 with wood stiffness and of -0.52 with compressive strength in Eucalyptus juvenile wood. MFA was found to be important in determining the mechanical behaviour of wood and appears to be a useful parameter to indicate wood stiffness and strength in juvenile Eucalyptus from short-rotation plantations.

  12. Hydraulic efficiency compromises compression strength perpendicular to the grain in Norway spruce trunkwood.

    Science.gov (United States)

    Rosner, Sabine; Karlsson, Bo

    2011-04-01

    The aim of this study was to investigate bending stiffness and compression strength perpendicular to the grain of Norway spruce (Picea abies (L.) Karst.) trunkwood with different anatomical and hydraulic properties. Hydraulically less safe mature sapwood had bigger hydraulic lumen diameters and higher specific hydraulic conductivities than hydraulically safer juvenile wood. Bending stiffness (MOE) was higher, whereas radial compression strength lower in mature than in juvenile wood. A density-based tradeoff between MOE and hydraulic efficiency was apparent in mature wood only. Across cambial age, bending stiffness did not compromise hydraulic efficiency due to variation in latewood percent and because of the structural demands of the tree top (e.g. high flexibility). Radial compression strength compromised, however, hydraulic efficiency because it was extremely dependent on the characteristics of the "weakest" wood part, the highly conductive earlywood. An increase in conduit wall reinforcement of earlywood tracheids would be too costly for the tree. Increasing radial compression strength by modification of microfibril angles or ray cell number could result in a decrease of MOE, which would negatively affect the trunk's capability to support the crown. We propose that radial compression strength could be an easily assessable and highly predictive parameter for the resistance against implosion or vulnerability to cavitation across conifer species, which should be topic of further studies. PMID:22058609

  13. Compressive strength evaluation of structural lightweight concrete by non-destructive ultrasonic pulse velocity method.

    Science.gov (United States)

    Bogas, J Alexandre; Gomes, M Glória; Gomes, Augusto

    2013-07-01

    In this paper the compressive strength of a wide range of structural lightweight aggregate concrete mixes is evaluated by the non-destructive ultrasonic pulse velocity method. This study involves about 84 different compositions tested between 3 and 180 days for compressive strengths ranging from about 30 to 80 MPa. The influence of several factors on the relation between the ultrasonic pulse velocity and compressive strength is examined. These factors include the cement type and content, amount of water, type of admixture, initial wetting conditions, type and volume of aggregate and the partial replacement of normal weight coarse and fine aggregates by lightweight aggregates. It is found that lightweight and normal weight concretes are affected differently by mix design parameters. In addition, the prediction of the concrete's compressive strength by means of the non-destructive ultrasonic pulse velocity test is studied. Based on the dependence of the ultrasonic pulse velocity on the density and elasticity of concrete, a simplified expression is proposed to estimate the compressive strength, regardless the type of concrete and its composition. More than 200 results for different types of aggregates and concrete compositions were analyzed and high correlation coefficients were obtained. PMID:23351273

  14. The Fire Resistance Performance of Recycled Aggregate Concrete Columns with Different Concrete Compressive Strengths

    Directory of Open Access Journals (Sweden)

    Hongying Dong

    2014-12-01

    Full Text Available In order to ascertain the fire resistance performance of recycled aggregate concrete (RAC components with different concrete compressive strengths, four full-scaled concrete columns were designed and tested under high temperature. Two of the four specimens were constructed by normal concrete with compressive strength ratings of C20 and C30, respectively, while the others were made from recycled coarse aggregate (RCA concrete of C30 and C40, respectively. Identical constant axial forces were applied to specimens while being subjected to simulated building fire conditions in a laboratory furnace. Several parameters from the experimental results were comparatively analyzed, including the temperature change, vertical displacement, lateral deflection, fire endurance, and failure characteristics of specimens. The temperature field of specimens was simulated with ABAQUS Software (ABAQUS Inc., Provindence, RI, USA and the results agreed quite well with those from the experiments. Results show that the rate of heat transfer from the surface to the interior of the column increases with the increase of the concrete’s compressive strength for both RAC columns and normal concrete columns. Under the same initial axial force ratio, for columns with the same cross section, those with lower concrete compressive strengths demonstrate better fire resistance performance. The fire resistance performance of RAC columns is better than that of normal concrete columns, with the same concrete compressive strength.

  15. On the compressive strength prediction for concrete masonry prisms

    OpenAIRE

    C. S. Barbosa; Lourenço, Paulo B.; Hanai, J. B.

    2010-01-01

    The results of a combined experimental program and numerical modeling program to evaluate the behavior of ungrouted hollow concrete blocks prisms under uniaxial compression are addressed. In the numerical program, three distinct approaches have been considered using a continuum model with a smeared approach, namely plane-stress, plane-strain and three-dimensional conditions. The response of the numerical simulations is compared with experimental data of masonry prisms using concrete blocks sp...

  16. Numerical validation of compressive strength prediction for hollow concrete blocks

    OpenAIRE

    C. S. Barbosa; Hanai, J. B.; Lourenço, Paulo B.

    2010-01-01

    The results of a numerical modeling program to evaluate the behavior of hollow concrete blocks under uniaxial compression are addressed. It has been considered appropriate to use interface elements to represent the confinement effect at the top and bottom of blocks. The response of the numerical simulations is compared with experimental data of masonry units. Laboratory tests were carried out utilizing standard flat platens and brush platens to evaluate the confinement effect due ...

  17. 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.

  18. 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.

  19. Compressive Strength of Volcanic Ash/Ordinary Portland Cement Laterized Concrete

    Directory of Open Access Journals (Sweden)

    Olusola K. O.

    2010-01-01

    Full Text Available This study investigates the effect of partial replacement of cement with volcanic ash (VA on the compressive strength of laterized concrete. A total of 192 cubes of 150mm dimensions were cast and cured in water for 7, 14, 21, and 28 days of hydration with cement replacement by VA and sand replacement by laterite both ranging from 0 to 30% respectively, while a control mix of 28-day target strength of 25 N/mm2 was adopted. The results show that the density and compressive strength of concrete decreased with increase in volcanic ash content. The 28-day, density dropped from 2390 kg/m3 to 2285 kg/m3 (i.e. 4.4% loss and the compressive strength from 25.08 N/mm2 to 17.98 N/mm2 (i.e. 28% loss for 0-30% variation of VA content with no laterite introduced. The compressive strength also decreased with increase in laterite content; the strength of the laterized concrete however increases as the curing age progresses.

  20. Prediction of Uniaxial Compressive Strength, Tensile Strength and Porosity of Sedimentary Rocks Using Sound Level Produced During Rotary Drilling

    Science.gov (United States)

    Rajesh Kumar, B.; Vardhan, Harsha; Govindaraj, M.

    2011-09-01

    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, tensile strength and percentage porosity of sedimentary rocks. The results were evaluated using the multiple regression analysis taking into account the interaction effects of various predictor variables. Predictor variables selected for the multiple regression model are drill bit diameter, drill bit speed, penetration rate and equivalent sound level produced during rotary drilling ( L eq). The constructed models were checked using various prediction performance indices. Consequently, it is possible to say that the constructed models can be used for practical purposes.

  1. Compressive strength measurements in aluminum for shock compression over the stress range of 4-22 GPa

    International Nuclear Information System (INIS)

    Measurements of the high-pressure compressive strength are presented for several aluminum alloys shocked to 22 GPa. Five well-characterized aluminum materials were studied, including 6061 alloy with three average grain sizes (50, 30, and yield-YHEL), increases with applied stress and plastic strain. A strength model was developed to describe this increase, which fits the data accurately to 55 GPa and reveals that ?Y increases with shock stress in three distinct regions. It also strongly indicates that metallurgical properties, such as impurities and grain size, influence the ambient yield strength, but not the change in strength, which appears to be controlled by the shock-deformed aluminum matrix and possibly grain boundaries

  2. 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.

  3. 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 Z...

  4. 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...

  5. Effect of Cement Stabilized Kaolin Subgrade on Strength Properties

    OpenAIRE

    Nur Akmal Abd Karim; Rashid, Ahmad Safuan A.; 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...

  6. 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

  7. Residual Compressive Strength of Laterized Concrete Subjected to Elevated Temperatures

    OpenAIRE

    Robert M. BROOKS

    2010-01-01

    This research presents the results of an experimental program to investigate the strength performance of laterized concrete (LATCON) when subjected to elevated temperatures of 200, 400 and 600ºC. Six concrete mixes incorporating 0, 10, 20, 30, 40 and 50% Laterite as a replacement by weight of sand was prepared. After heat pretreatment specimens were cooled using either rapid cooling (water-cooling) or natural cooling (air-cooling). An analysis of variance test shows that exposure temperature...

  8. 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.

  9. 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

  10. Strength and Permeability of Stabilized Peat Soil

    OpenAIRE

    Wong, L. S.; Hashim, R.; Ali, F. H.

    2008-01-01

    The aim of this study was to analyze the unconfined compressive strength and initial permeability of peat soil stabilized by a mixture of Ordinary Portland cement, ground granulated blast furnace slag and siliceous sand. An understanding of the stabilized soil properties is of great importance for the design of deep stabilization in peat land for highway construction. Significant evidence on the positive effects of the admixture at stabilizing peat soil was discovered from laboratory t...

  11. Point load test application for estimating compressive strength of concrete structures from small core

    Directory of Open Access Journals (Sweden)

    A. Zacoeb

    2009-09-01

    Full Text Available To estimate a compressive strength from existing concrete structures by core drilling are usually gathered with a diameter specimen of 100mm or three times of maximum coarse aggregate size and examined by uniaxial compressive strength (UCS test as stated in JIS A1170. To get an alternative solution with smaller specimen, point load test (PLT has been selected which is a simple test and widely accepted in rock materials research, but relatively new in concrete. The reliability of PLT is examined by extracting a lot of core drilled specimen from ready mixed concrete blocks with maximum coarse aggregate size, Gmax of 20mm in representative of architectural structures and 40mm in representative of civil structures on the range of concrete grade from 16 to 50. The reference of strength is resulted from concrete core diameter of 100 and 125mm with h/d ratio of 2.0, and examined by UCS test with compressive strength of concrete core of f’cc in results. The core specimen diameters are 35 and 50mm with h/d ratio of 1.5 and 2.0, and examined by PLT with point load index of IS in results. The estimation of compressive strength is conducted by making a linear approximation for IS to f’cc for each group of Gmax and h/d. This study also evaluates the reliability of test results for each core specimen and proposes a new geometric correction factor.

  12. Prediction of the Uniaxial Compressive Strength of a Greywacke by Fuzzy Inference System

    Science.gov (United States)

    Zorlu, Kívanc; Gokceoglu, Candan; Sonmez, Harun

    Rock engineering projects require the uniaxial compressive strength of intact rock. High quality core samples are needed for the application of uniaxial compressive strength in laboratory. In this study, to establish some predictive models taking into consideration multiple regression techniques and fuzzy inference system is aimed. Ankara greywackes is selected as the material, because of its highly problematic nature as mentioned by many previous researchers. For this purpose, a series of rock mechanics tests were carried out, and uniaxial compressive strength, point load index, block punch index, unit weight, apparent porosity, water absorption by weight, P-wave velocity, Schmidt hardness and tensile strength of greywacke were obtained. Using the obtained results, two prediction models were constructed to predict the uniaxial compressive strength of selected greywacke. The values account for and root mean square error indices were calculated as 41.49% and 15.62 the multiple regression model; 81.24% and 13.06 for the fuzzy inference system. As a result, these indices revealed that the prediction performances of the fuzzy model are higher than that of multiple regression equations.

  13. Micromechanical strength effects in shock compression of solids

    International Nuclear Information System (INIS)

    Time-resolved shock-wave measurements and post-shock recovery techniques have long been used as means of inferring the underlying micromechanics controlling high-rate deformation of solids. This approach requires a considerable amount of subjective interpretation. In spite of this feature, progress has been made in experimentation and theoretical interpretation of the shock-compression/release cycle and some of the results are reviewed here for weak shocks. Weak shocks are defined to be those with peak amplitudes (typically 10--20 GPa for most solids) that do not overdrive the elastic precursor. The essential elements of a typical shock-compression/release cycle involve, in order, (a) the elastic precursor, (b) plastic loading wave, (c) pulse duration, (d) release wave, and (e) post-mortem examination. These topics are examined in turn, with some emphasis given to elements (b) and (d). If the plastic loading wave is traveling without change of shape, it is possible to convert the particle-velocity/time records to a shear-stress/plastic-strain-rate path. Shock data in this form can be compared directly with low-to-intermediate strain-rate tests. Results for copper and tantalum show how shock data can be used to determine the transition from the deformation mechanism of thermal activation to that of dislocation drag. An important result of release-wave studies is that the leading observable release disturbance in FCC metals may not be propagating with the ideal, longitunot be propagating with the ideal, longitudinal elastic-wave speed, but at a lower velocity dependent on the elastic bulk and shear moduli and the product of the dislocation density times the pinning separation squared for dislocation segments in the region behind the shock and ahead of the release wave. copyright 1994 American Institute of Physics

  14. Using metakaolin to improve the compressive strength and the durability of fly ash based concrete

    OpenAIRE

    Torgal, Fernando Pacheco; Shahsavandi, Arman; Jalali, Said

    2011-01-01

    Partial replacement of Portland cement by pozzolanic and cimentitious by-products or mineral additions that allow for carbon dioxide emission reductions is a major issue in the current climate change context. However, the use of low pozzolanic activity by-products like fly ash can cause a decrease relatively early in compressive strength. In this paper, the effect of metakaolin and fly ash on strength and concrete durability was investigated. The durability was assessed by different means ...

  15. 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.

  16. Explosive Axial Magnetic Flux Compression Generator Armature Material Strength and Compression Effects

    Science.gov (United States)

    Ruden, E. L.; Kiuttu, G. F.; Peterkin, R. E.; Chase, J. B.

    2004-11-01

    The expansion of the armature of an axial magnetic flux compression generator results in an increase in the armature's electrical resistivity and possible melting due to compression and plastic work heating. If melting occurs, further flux compression is impaired by a greatly enhanced Rayleigh-Taylor instability. Even without melting, the expansion process can become unstable, with the armature fragmenting by plastic instability. These processes result in decreased performance. To complement more detailed modeling via multi-dimensional codes, terms are derived suitable for use in a code that couples a zero dimensional model of the armature to a lumped circuit. For computational simplicity, only armature properties averaged over the armature thickness as functions of axial position and time are modeled. Further simplifications resulting in analytic approximations are presented to provide some preliminary indication of the significance of material effects.

  17. 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.

  18. The Effects of Different Curing Methods on the Compressive Strength of Terracrete

    Directory of Open Access Journals (Sweden)

    O. Alake

    2009-01-01

    Full Text Available This research evaluated the effects of different curing methods on the compressive strength of terracrete. Several tests that included sieve analysis were carried out on constituents of terracrete (granite and laterite to determine their particle size distribution and performance criteria tests to determine compressive strength of terracrete cubes for 7 to 35 days of curing. Sand, foam-soaked, tank and open methods of curing were used and the study was carried out under controlled temperature. Sixty cubes of 100 × 100 × 100mm sized cubes were cast using a mix ratio of 1 part of cement, 1½ part of latrite, and 3 part of coarse aggregate (granite proportioned by weight and water – cement ratio of 0.62. The result of the various compressive strengths of the cubes showed that out of the four curing methods, open method of curing was the best because the cubes gained the highest average compressive strength of 10.3N/mm2 by the 35th day.

  19. 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)

  20. 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.

  1. Effect of Impact Damage and Open Hole on Compressive Strength of Hybrid Composite Laminates

    Science.gov (United States)

    Hiel, Clement; Brinson, H. F.

    1993-01-01

    Impact damage tolerance is a frequently listed design requirement for composites hardware. The effect of impact damage and open hole size on laminate compressive strength was studied on sandwich beam specimens which combine CFRP-GFRP hybrid skins and a syntactic foam core. Three test specimen configurations have been investigated for this study. The first two were sandwich beams which were loaded in pure bending (by four point flexure). One series had a skin damaged by impact, and the second series had a circular hole machined through one of the skins. The reduction of compressive strength with increasing damage (hole) size was compared. Additionally a third series of uniaxially loaded open hole compression coupons were tested to generate baseline data for comparison with both series of sandwich beams.

  2. 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.

  3. 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)

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

    Science.gov (United States)

    Galvão, M. R.; Caldas, S. G. F. R.; Calabrez-Filho, S.; Campos, E. A.; Bagnato, V. S.; Rastelli, A. N. S.; Andrade, M. F.

    2013-04-01

    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 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.

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. Compressive strength and microstructure of carbon nanotubes-fly ash cement composites

    Energy Technology Data Exchange (ETDEWEB)

    Chaipanich, Arnon, E-mail: arnon@chiangmai.ac.th [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, 239 Huay Gaew Road, Suthep District, Chiang Mai 50200 (Thailand); Nochaiya, Thanongsak; Wongkeo, Watcharapong; Torkittikul, Pincha [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, 239 Huay Gaew Road, Suthep District, Chiang Mai 50200 (Thailand)

    2010-02-15

    In this work, carbon nanotubes of 0.5 and 1% by weight were added for the first time in a fly ash cement system to produce carbon nanotubes-fly ash composites in the form of pastes and mortars. Compressive strengths of the composites were then investigated. It was found that the use of carbon nanotubes resulted in higher strength of fly ash mortars. The highest strength obtained for 20% fly ash cement mortars was found at 1% carbon nanotubes where the compressive strength at 28 days was 51.8 MPa. This benefit can clearly be seen in fly ash cement with fly ash of 20% where the importance of the addition of carbon nanotubes means that the relative strength to that of Portland cement became almost 100% at 28 days. In addition, scanning electron micrographs also showed that good interaction between carbon nanotubes and the fly ash cement matrix is seen with carbon nanotubes acting as a filler resulting in a denser microstructure and higher strength when compared to the reference fly ash mix without CNTs.

  10. Compressive strength and microstructure of carbon nanotubes-fly ash cement composites

    International Nuclear Information System (INIS)

    In this work, carbon nanotubes of 0.5 and 1% by weight were added for the first time in a fly ash cement system to produce carbon nanotubes-fly ash composites in the form of pastes and mortars. Compressive strengths of the composites were then investigated. It was found that the use of carbon nanotubes resulted in higher strength of fly ash mortars. The highest strength obtained for 20% fly ash cement mortars was found at 1% carbon nanotubes where the compressive strength at 28 days was 51.8 MPa. This benefit can clearly be seen in fly ash cement with fly ash of 20% where the importance of the addition of carbon nanotubes means that the relative strength to that of Portland cement became almost 100% at 28 days. In addition, scanning electron micrographs also showed that good interaction between carbon nanotubes and the fly ash cement matrix is seen with carbon nanotubes acting as a filler resulting in a denser microstructure and higher strength when compared to the reference fly ash mix without CNTs.

  11. 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

  12. Compressive strength of structural concrete made with locally available coarse aggregates

    International Nuclear Information System (INIS)

    Quality of CA (Coarse Aggregate) is one of the prime factors to control the quality of concrete. But construction industry of Sindh is not very much bothered about the quality of CA in concrete manufacturing. In Sindh, Hyderabad vicinity is comparatively rich in production of CA. This research is to evaluate the compressive strength of structural concrete made with CA obtained from five different crush plants (Petaro, Parker, Palari, Ghulam Hyder Baloch and Ongar), available in the vicinity of Hyderabad. ln total 360 concrete cubes (150x150x150mm) were manufactured, 72 for each source of CA by keeping 1:2:4 and 1:1.5:3 material ratios. The cubes were manufactured with 0.45 w/c (water cement ratio), 0.5 and 0.55 w/c and tested for compressive strength after 3, 7, 14 and 28 days of curing. Results show that performance of CA obtained from all the five crush plants remained in agreement with BS and ACI Code recommendations. Concrete made with CA obtained from Petaro and Parker gave higher early strength than that of others while concrete made with CA obtained from Petaro, Parker together with Palari gave higher 28th day compressive strength. (author)

  13. Development of a Strength Prediction Model for “Green” Compressed Stabilised Earthbricks

    Directory of Open Access Journals (Sweden)

    Chee-Ming Chan

    2010-08-01

    Full Text Available Traditional fired clay bricks are widely used as a fundamental building material in most countries. Availability, low costs and low-skilled labour are main factors that have made the bricks a popular choice. However with rising awareness to reduce carbon footprint and promote sustainable development, earth-making has taken a different path to minimize the environmental impact. Compressed stabilised earthbrick is an example of the alternative building material. Various efforts have been directed to develop these bricks, including the use of different binding agents, raw materials and technology. In conjunction with these progresses, and considering that strength is the primary concern in brick-making, it was conceived that a strength prediction model ought to be established to assist in the bricks’ production, especially in the mix design stage. In collaboration with a local property developer, the Research Centre for Soft Soils (RECESS has embarked on an industrial research project to develop “green” sustainable compressed stabilised earthbricks in situ for a large scale mixed development site. As part of the joint research effort, a series of trial specimens were prepared at different mix ratios using soil samples retrieved from the site. The specimens were next examined with the conventional compressive strength test, coupled with the novel non-destructive S-wave velocity measurement. The test results were then analysed and cross-correlated to establish a strength prediction model for the bricks produced. The charts relating the relevant parameters serve not only as a quick guide to the expected strength, but also provide insights to the behaviour of compressed stabilised material under loading.

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

    Directory of Open Access Journals (Sweden)

    José Vidal Nardi

    2004-06-01

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

    OpenAIRE

    Tickle, Vrushali M.; Madugula, Murty K. S.; Cindy Kumalasari

    2005-01-01

    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...

  16. Effect of non-standard curing methods on the compressive strength of laterized concrete

    OpenAIRE

    Felix F. Udoeyo; Robert Brooks; Christopher Utam; Philip Udo-Inyang; Eno C. Ukpong

    2010-01-01

    Thirty concrete mixes of differing water-binder ratio containing 0, 10, 20, 30, 40 and 50 % laterite as a partial replacement for sand were used to prepare laterized concrete specimens for the study of the effect of nonstandard curing methods on the strength of specimen. The effectiveness of a curing method was measured quantitatively as the ratio of the compressive strength of specimen cured using the non-standard method to those cursed using the standard water-curing method specified in the...

  17. Compressive strength and outgassing characteristics of concrete for large vacuum-system construction

    International Nuclear Information System (INIS)

    Concrete enclosures can be used for vacuum-system construction. However, limited information exists on the behavior of concrete in vacuum. For this reason, concrete testing was performed recently at the Los Alamos National Laboratory to obtain data on outgassing and compressive strength of concrete in vacuum. The results of the experimental program will be presented to support the major conclusion that concrete is suitable for high-vacuum systems without degradation of strength and should be considered for large vacuum-system construction

  18. Behaviour of venous flow rates in intermittent sequential pneumatic compression of the legs using different compression strengths

    International Nuclear Information System (INIS)

    A study with 25 patients was performed in order to find out whether intermittent, sequential, pneumatic leg compression is of value in the preventive management of thrombosis due to its effect on the venous flow rates. For this purpose, xenon 133 was injected into one of the foot veins and the flow rate in each case determined for the distance between instep and inguen using different compression strengths, with pressure being exerted on the ankle, calf and thigh. Increased flow rates were already measured at an average pressure value of 34.5 mmHg, while the maximum effect was achieved by exerting a pressure of 92.5 mmHg, which increased the flow rate by 366% as compared to the baseline value. The results point to a significant improvement of the venous flow rates due to intermittent, sequential, pneumatic leg compression and thus provide evidence to prove the value of this method in the prevention of hemostasis and thrombosis. (TRV)

  19. 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.

  20. 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)

  1. 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)

  2. 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.

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

    OpenAIRE

    MD NOR ATAN; HANIZAM AWANG

    2011-01-01

    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 vi...

  5. 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

  6. Reliability Assessment of Buckling Strength for Compressed Cylindrical Shells with Interacting Localized Geometric Imperfections

    OpenAIRE

    Bahaoui, Jalal E.; Abdellatif Khamlichi; Bakkali, Larbi E.; Ali Limam

    2010-01-01

    Problem statement: Elastic cylindrical shells are common structures in the fields of civil engineering and engineering mechanics. These thin-walled constructions may undergo buckling when subjected to axial compression. Buckling limits to large extent their strength performance. This phenomenon depends hugely on the initial distributed or localized geometric imperfections that are present on the shell structure. Localized geometric imperfections result in general from the operation of welding...

  7. 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.

  8. 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...

  9. Compressive Strength, Chloride Permeability, and Freeze-Thaw Resistance of MWNT Concretes under Different Chemical Treatments

    OpenAIRE

    Xingang Wang; Inkyu Rhee; Yao Wang; Yunping Xi

    2014-01-01

    This study investigated compressive strength, chloride penetration, and freeze-thaw resistance of multiwalled carbon nanotube (MWNT) concrete. More than 100 cylindrical specimens were used to assess test variables during sensitivity observations, including water-cement ratios (0.75, 0.5, and 0.4) and exposure to chemical agents (including gum arabic, propanol, ethanol, sodium polyacrylate, methylcellulose, sodium dodecyl sulfate, and silane). To determine the adequate sonication time for MWNT...

  10. 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

  11. Compressive strength of elderly vertebrae is reduced by disc degeneration and additional flexion.

    Science.gov (United States)

    Maquer, Ghislain; Schwiedrzik, Jakob; Huber, Gerd; Morlock, Michael M; Zysset, Philippe K

    2015-02-01

    Computer tomography (CT)-based finite element (FE) models assess vertebral strength better than dual energy X-ray absorptiometry. Osteoporotic vertebrae are usually loaded via degenerated intervertebral discs (IVD) and potentially at higher risk under forward bending, but the influences of the IVD and loading conditions are generally overlooked. Accordingly, magnetic resonance imaging was performed on 14 lumbar discs to generate FE models for the healthiest and most degenerated specimens. Compression, torsion, bending, flexion and extension conducted experimentally were used to calibrate both models. They were combined with CT-based FE models of 12 lumbar vertebral bodies to evaluate the effect of disc degeneration compared to a loading via endplates embedded in a stiff resin, the usual experimental paradigm. Compression and lifting were simulated, load and damage pattern were evaluated at failure. Adding flexion to the compression (lifting) and higher disc degeneration reduces the failure load (8-14%, 5-7%) and increases damage in the vertebrae. Under both loading scenarios, decreasing the disc height slightly increases the failure load; embedding and degenerated IVD provides respectively the highest and lowest failure load. Embedded vertebrae are more brittle, but failure loads induced via IVDs correlate highly with vertebral strength. In conclusion, osteoporotic vertebrae with degenerated IVDs are consistently weaker-especially under lifting, but clinical assessment of their strength is possible via FE analysis without extensive disc modelling, by extrapolating measures from the embedded situation. PMID:25460926

  12. Compressive strength of concrete using lateritic sand and quarry dust as fine aggregate

    Directory of Open Access Journals (Sweden)

    Joseph O. Ukpata

    2012-01-01

    Full Text Available This paper is part of a study investigating the structural characteristics of concrete using various combinations of lateritic sand and quarry dust as complete replacement for conventional river sand fine aggregate. Samples of concrete (eg. cubes were made using varying contents of laterite and quarry dust as fine aggregate. The quantity of laterite was varied from 0% to 100% against quarry dust at intervals of 25%. The samples were cured for specified periods and tested in the laboratory for compressive strength. Workability tests were earlier carried out to determine the optimum water/cement ratios for three different mixes, namely: 1:1:2, 1:1.5:3 and 1:2:4. It was found that 0.5 water/cement ratio produced higher compressive strengths for 1:1:2 mix, while 0.6 water/cement ratio exhibit better workability for 1:1.5:3 mix proportion. Specifically compressive strength ranged from 17-34.2 N/mm2 for the mixes considered. These results compare favourably with those of conventional concrete. The concrete was found to be suitable for use as structural members for buildings and related structures, where laterite content did not exceed 50%.

  13. Compressive Strength of Shocked Aluminum for Stresses of 4-22 Gpa

    International Nuclear Information System (INIS)

    Measurements of the compressive strength are presented for several aluminum alloys shocked to 22 GPa. Five well characterized alloys were studied, including 6061 with grain sizes of 50, 30 and <5 ?m, and both pure and ultra pure Al with grain sizes of ? 200 and 300 ?m, respectively. The yield strength in the shocked state was estimated using reshock and release techniques. These results show that quasi-elastic recompression occurs for all materials investigated and is independent of grain size and impurity level. The present data, together with other data, illustrate that the yield strength of Al increases with shock stress to 90 GPa and suggest that the increase in strength at the shock state, ?Y (?Y = Yyield - YHEL), increases with applied stress and plastic strain. A new model was developed to describe this increase and fits existing strength data on aluminum accurately to 55 GPa. The agreement strongly indicates that initial material properties, influence the ambient yield strength, but not the change in strength, which appears to be controlled by shock-deformation

  14. The Value Compressive Strength and Split Tensile Strength on Concrete Mixture With Expanded Polystyrene Coated by Surfactant Span 80 as a Partial Substitution of Fine Aggregate

    Science.gov (United States)

    Hidayat, Irpan; Siauwantara, Alice

    2014-03-01

    The value of the density normal concrete which ranges between 2200-2400 kg/m3. Therefore the use of Expanded Polystyrene (EPS) as a subitute to fine aggregate can reduce the density of concrete. The purpose this research is to reduce the density of normal concrete but increase compressive strength of EPS concrete, with use surfactant as coating for the EPS. Variables of substitution percentage of EPS and EPS coated by surfactant are 5%,10%,15%,20%,25%. Method of concrete mix design based on SNI 03-2834-2000 "Tata Cara Pembuatan Rencana Campuran Beton Normal (Provisions for Proportioning Normal Concrete Mixture)". The result of testing, every increase percentage of EPS substitution will decrease the compressive strength around 1,74 MPa and decrease density 34,03 kg/m3. Using Surfactant as coating of EPS , compressive strength increase from the EPS's compressive strength. Average of increasing compressive strength 0,19 MPa and increase the density 20,03 kg/m3,average decrease of the tensile split strength EPS coated surfaktan is 0,84 MPa.

  15. The Value Compressive Strength and Split Tensile Strength on Concrete Mixture With Expanded Polystyrene Coated by Surfactant Span 80 as a Partial Substitution of Fine Aggregate

    Directory of Open Access Journals (Sweden)

    Hidayat Irpan

    2014-03-01

    Full Text Available The value of the density normal concrete which ranges between 2200–2400 kg/m3. Therefore the use of Expanded Polystyrene (EPS as a subitute to fine aggregate can reduce the density of concrete. The purpose this research is to reduce the density of normal concrete but increase compressive strength of EPS concrete, with use surfactant as coating for the EPS. Variables of substitution percentage of EPS and EPS coated by surfactant are 5%,10%,15%,20%,25%. Method of concrete mix design based on SNI 03-2834-2000 “Tata Cara Pembuatan Rencana Campuran Beton Normal (Provisions for Proportioning Normal Concrete Mixture”. The result of testing, every increase percentage of EPS substitution will decrease the compressive strength around 1,74 MPa and decrease density 34,03 kg/m3. Using Surfactant as coating of EPS , compressive strength increase from the EPS’s compressive strength. Average of increasing compressive strength 0,19 MPa and increase the density 20,03 kg/m3,average decrease of the tensile split strength EPS coated surfaktan is 0,84 MPa.

  16. 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.

  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. An Empirical Relationship between Modulus of Elasticity, Modulus of Rupture and Compressive Strength of M60 Concrete Containing Metakaolin

    Directory of Open Access Journals (Sweden)

    K. Anbuvelan

    2014-09-01

    Full Text Available This study presents the relationship between modulus of elasticity and, modulus of rupture relationship with compressive strength of M60 concrete incorporating Metakaolin. Comparing the experimentally obtained result with the mechanical properties calculated using the recommended relationship from the various design codes, one finds substantially variation in the data. A new empirical relationship between elastic modulus, modulus of rupture and compressive strength for Metakolin based M60 concrete is proposed.

  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 noticeining 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. Analysis and Assessment of Strength Development in Compressed FaL-G Blocks

    Science.gov (United States)

    Nagendra Prasad, K.; Vijaya Bhaskar, S.; Narasimhulu, M. L.; Manohara Reddy, R.

    2014-09-01

    Of the several options explored in large scale utilization of fly ash, such as production of blended cements, high volume fly ash cement concretes, fly ash, lime and gypsum (FaL-G) combinations, alkali activated fly ash mortars and concretes are of recent innovations. The last two are non-traditional cementing materials, since no cement is used in processing of these materials. This investigation deals with analysis and assessment of strength development in compressed FaL-G blocks. FaL-G chemistry provides a strong scientific base for understanding the mechanisms of interaction. But an equally strong technological base in the production of FaL-G blocks is the need of the hour. In this investigation, analysis has been made to advance a phenomenological model to arrive at the combinations of the ingredients to produce compressed blocks to meet the strength development desired at specified age, based on carefully planned experimental data generated. The analysis of test results has been done within the framework of Abrams' law, which is extensively used in concrete technology. The validity has been examined with an independent set of experimental data. With incorporation of more data covering still wider spectrum of materials the phenomenological model can further be reinforced as a viable tool in the production of compressed FaL-G blocks.

  1. 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.

  2. Improving the compressive strength of bioceramic robocast scaffolds by polymer infiltration.

    Science.gov (United States)

    Martínez-Vázquez, Francisco J; Perera, Fidel H; Miranda, Pedro; Pajares, Antonia; Guiberteau, Fernando

    2010-11-01

    The effect of polymer infiltration on the compressive strength of ?-tricalcium phosphate (TCP) scaffolds fabricated by robocasting (direct write assembly) is analyzed in this work. Porous structures consisting of a tetragonal three-dimensional mesh of interpenetrating rods were fabricated from concentrated TCP inks with suitable viscoelastic properties. Biodegradable polymers (polylactic acid (PLA) and poly(?-caprolactone) (PCL)) were infiltrated into selected scaffolds by immersion of the structure in a polymer melt. Infiltration increased the uniaxial compressive strength of these model scaffolds by a factor of three (PCL) or six (PLA). It also considerably improved the mechanical integrity of the structures after initial cracking, with the infiltrated structure retaining a significant load-bearing capacity after fracture of the ceramic rods. The strength improvement in the infiltrated scaffolds was attributed to two different contributions: the sealing of precursor flaws in the ceramic rod surfaces and the partial transfer of stress to the polymer, as confirmed by finite element analysis. The implications of these results for the mechanical optimization of scaffolds for bone tissue engineering applications are discussed. PMID:20566307

  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. 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.

  5. 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.

  6. 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)atic test. (author)

  7. 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.

  8. A comparison of pressure compaction and diametral compression tests for determining granule strengths

    Science.gov (United States)

    Glass, S. J.; Newton, C.

    Lightning strikes can cause structural damage, ignite flammable materials, and produce circuit malfunctions in missiles, aircraft, and ground systems. Lightning arrestor connectors (LAC's) are used to divert harmful lightning energy away from these systems by providing less destructive breakdown paths. Ceramic granules in the size range of 150-200 micrometers are used in LAC's to provide physical and electrical separation of contacts (pins) from the surrounding metal web, and to control the voltage breakdown level. Pressure compaction (P-C) tests were used to characterize the strength of ceramic granules. When compaction data are plotted as relative density of the compact versus the compaction pressure two linear regions are generally observed. The intersection of these regions, which is known as the 'breakpoint,' has been used as a semi-quantitative measure of granule strength. Comparisons were made between the P-C breakpoint and strengths of 150-200 micrometers diameter ZnO, TiO2 (rutile), and lead magnesium niobate-lead titanate (PMN-PT) granules, where the strengths were determined by diametral compression (D-C) tests. At high compaction pressures the compliance of the die itself is significant and was accounted for in the analyses. Tests were conducted at different compaction rates, and with different aspect ratio compacts. High aspect ratios and loading rates decrease the slope of the second linear portion of the compaction curve and produce higher apparent P-C breakpoints. Comparison of the P-C breakpoint to the average D-C strength indicates that the D-C strength is approximately fifty percent higher for PMN-PT granules. To eliminate the uncertainty in results due to irregular granules sizes and shapes, comparisons were made for uniform size (210 micrometers) glass spheres. In this case the average D-C strength coincided with a second breakpoint in the P-C data, which occurred after compaction by a mechanism of bridge formation and collapse had ceased.

  9. Microstructure and compression strength of novel TRIP-steel/Mg-PSZ composites

    Science.gov (United States)

    Biermann, H.; Aneziris, C. G.; Kolbe, A.; Martin, U.; Müller, A.; Schärfl, W.; Herrmann, M.

    2010-07-01

    A novel steel-based composite material, composed of metastable austenitic stainless steel as matrix and up to 15 % zirconia as reinforcement, is processed by two powder metallurgy routes. The matrix exhibits the so-called TRIP-effect (TRIP: TRansformation-Induced Plasticity) and shows a deformation-induced formation of martensite. Compression tests of rod samples processed by cold isostatic pressing show increased strength compared to the non-reinforced steel matrix up to 20 % strain. Three-point bending tests show, however, reduced ductility for high zirconia contents. Filigree honeycomb structures were produced by a novel extrusion technique with extraordinary high values of specific energy absorption.

  10. Investigations on the ultimate compressive strength of composite plates with geometrical imperfections

    DEFF Research Database (Denmark)

    Misirlis, K. Newcastle University

    2009-01-01

    A series of studies has been performed within the MARSTRUCT Network of Excellence on Marine Structures in order to investigate the buckling response of glass fibre reinforced polymer plates. These studies include the fabrication, testing and finite element analysis of a large number of plates with initial geometric imperfections. This paper presents the validation of finite element models against a series of plate tests that were performed within this framework and parametric studies that were carried out to identify the effects of geometric imperfections on the ultimate compressive strength of composite plates with three alternative lay-up configurations.

  11. Calcium Phosphate Bone Cements Including Sugar Surfactants: Part One—Porosity, Setting Times and Compressive Strength

    Directory of Open Access Journals (Sweden)

    Juliette Fitremann

    2010-09-01

    Full Text Available Addition of sugar surfactants, sucrose fatty acid esters and alkylpolyglucosides, to calcium phosphate cement designed for bone reconstruction is described. Thanks to their surface activity and through their adsorption at the surface of the calcium phosphate particles, they both induced a strong increase in the porosity (quantified by Image Analysis and brought a very good workability. Other properties typically studied for these cements are reported, including setting times, compressive strength, cohesion in water, and effect of sterilization on these properties. The whole study brought good insight in the interest of adding these mild surfactants to improve several properties of the calcium phosphate cement, without impairing their function.

  12. Break force and tensile strength relationships for curved faced tablets subject to diametrical compression.

    Science.gov (United States)

    Shang, C; Sinka, I C; Jayaraman, B; Pan, J

    2013-02-14

    The break force of flat faced tablets subject to diametrical compression (often referred to as "hardness") can be related to the tensile strength of the material using the Hertz contact theory. For curved tablets analytical solutions do not exist and an empirical equation developed by Pitt and Newton (1988) is usually used. In this paper we measure the break force of curved faced tablets having a range of curvatures pressed at various compaction forces. An empirical equation is proposed to relate the break force of curved faced tablets to the material tensile strength. The proposed equation is simplified and reduced to a form that is consistent with developed by Hertz theory for flat faced tablets. PMID:22975309

  13. 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.

  14. 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.

  15. Prediction of compressive strength of cement mortars with fly ash and activated coal gangue

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Shuangxi; Chen Yimin; Zhou Shuangxi [China Building Materials Academy, Beijing (China)

    2006-07-01

    The pozzolanic activity of coal gangue, which is calcining at 500 to 1,000{sup o} differs distinctly. The simplex - centroid design with upper and lower bounds of component proportion is adopted to study the compressive strength of mortars made with ternary blends of cement. activated coal gangue and fly ash. Based on the results of a minimum of seven design points, three special cubic polynomial models are used to establish the strength predicating equations at different ages for mortars. Five experimental checkpoints were also designed to verify the precision of the equations. The most frequent errors of the predicted values are within 3%. A simple and practical way is provided for determining the optimal proportion of two admixtures when they are used in concrete. 7 refs.

  16. Influence of Curing Age and Mix Composition on Compressive Strength of Volcanic Ash Blended Cement Laterized Concrete

    Directory of Open Access Journals (Sweden)

    Babafemi A.J.

    2012-01-01

    Full Text Available This study investigates the influence of curing age and mix proportions on the compressive strength of volcanic ash (VA blended cement laterized concrete. A total of 288 cubes of 100mm dimensions were cast and cured in water for 3, 7, 28, 56, 90 and 120 days of hydration with cement replacement by VA and sand replacement by laterite both ranging from 0 to 30% respectively while a control mix of 28-day target strength of 25N/mm2 (using British Method was adopted. The results show that the compressive strength of the VA-blended cement laterized concrete increased with the increase in curing age but decreased as the VA and laterite (LAT contents increased. The optimum replacement level was 20%LAT/20%VA. At this level the compressive strength increased with curing age at a decreasing rate beyond 28 days. The target compressive strength of 25N/mm2 was achieved for this mixture at 90 days of curing. VA content and curing age was noted to have significant effect (? ? 0.5 on the compressive strength of the VA-blended cement laterized concrete.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. Effect of non-standard curing methods on the compressive strength of laterized concrete

    Directory of Open Access Journals (Sweden)

    Felix F. Udoeyo

    2010-02-01

    Full Text Available Thirty concrete mixes of differing water-binder ratio containing 0, 10, 20, 30, 40 and 50 % laterite as a partial replacement for sand were used to prepare laterized concrete specimens for the study of the effect of nonstandard curing methods on the strength of specimen. The effectiveness of a curing method was measured quantitatively as the ratio of the compressive strength of specimen cured using the non-standard method to those cursed using the standard water-curing method specified in the BS1881: Part 3:1970 (control. The results of the investigation show that with continuous wetting of the nonstandard curing media by sprinkling with water, the strength of the concrete obtained could be comparable to those cured using the control method. Of the four nonstandard curing methods considered in the study it was observed that the strength of sand- and sawdust-cured specimen were in some instances the same as or higher than those of the standard cured specimens at early age (7days. Although at later age (28 days there were significant differences between the strength of specimens cured using the nonstandard methods and those of corresponding laterite content and water-binder ratio cured using the control method as established by t-test, the designed strength of 20 MPa was attained by all specimens cured using the nonstandard methods, which is indicative that these nonstandard methods could be used as alternative to the standard water curing, especially in situations where much water may not be available for curing specimens.

  2. In vitro comparison of DE-QCT parameters with the compressive strength of cancellous bone

    International Nuclear Information System (INIS)

    Quantitative computed tomography (QCT) is used as a method for assessing bone mineral in patients with osteoporosis. The implication being that if the mass of bone mineral is low enough then the patient is at risk for developing symptoms, i.e., fracture. The authors performed an in vitro test which compared dual-energy-QCT (DE-QCT) parameters with compressive strength. The bone samples were placed in a water bath and CT scanned using a Siemens DR-3. Alternating x-ray pulses of 125 and 85 kVp were used to generate the dual energy images. Four images, high kVp, low kVp, monoenergenic, and calcium equivalent, were reconstructed from each scan. A specially constructed bone mineral calibration phantom, consisting of a polyethylene rod and varying tubes of K2HP04, was placed within the water bath along with the specimens. Comparisons will be made between the various DE parameters and their relationship to the compressive strength of cancellous bone. The critical effect of trabecular bone orientation will also be discussed

  3. 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

  4. Determination of Uniaxial Compressive Strength of Ankara Agglomerate Considering Fractal Geometry of Blocks

    Science.gov (United States)

    Coskun, Aycan; Sonmez, Harun; Ercin Kasapoglu, K.; Ozge Dinc, S.; Celal Tunusluoglu, M.

    2010-05-01

    The uniaxial compressive strength (UCS) of rock material is a crucial parameter to be used for design stages of slopes, tunnels and foundations to be constructed in/on geological medium. However, preparation of high quality cores from geological mixtures or fragmented rocks such as melanges, fault rocks, coarse pyroclastic rocks, breccias and sheared serpentinites is often extremely difficult. According to the studies performed in literature, this type of geological materials may be grouped as welded and unwelded birmocks. Success of preparation of core samples from welded bimrocks is slightly better than unwelded ones. Therefore, some studies performed on the welded bimrocks to understand the mechanical behavior of geological mixture materials composed of stronger and weaker components (Gokceoglu, 2002; Sonmez et al., 2004; Sonmez et al., 2006; Kahraman, et al., 2008). The overall strength of bimrocks are generally depends on strength contrast between blocks and matrix; types and strength of matrix; type, size, strength, shape and orientation of blocks and volumetric block proportion. In previously proposed prediction models, while UCS of unwelded bimrocks may be determined by decreasing the UCS of matrix considering the volumetric block proportion, the welded ones can be predicted by considering both UCS of matrix and blocks together (Lindquist, 1994; Lindquist and Goodman, 1994; Sonmez et al., 2006 and Sonmez et al., 2009). However, there is a few attempts were performed about the effect of blocks shape and orientation on the strength of bimrock (Linqduist, 1994 and Kahraman, et al., 2008). In this study, Ankara agglomerate, which is composed of andesite blocks and surrounded weak tuff matrix, was selected as study material. Image analyses were performed on bottom, top and side faces of cores to identify volumetric block portions. In addition to the image analyses, andesite blocks on bottom, top and side faces were digitized for determination of fractal dimensions. To determine fractal dimensions of more than hundred andesite blocks in cores, a computer program namely FRACRUN were developed. Fractal geometry has been used as practical and popular tool to define particularly irregular shaped bodies in literature since the theory of fractal was developed by Mandelbrot (1967) (Hyslip and Vallejo, 1997; Kruhl and Nega, 1996; Bagde etal., 2002; Gulbin and Evangulova, 2003; Pardini, 2003; Kolay and Kayabali, 2006; Hamdi, 2008; Zorlu, 2009 and Sezer, 2009). Although there are some methods to determine fractal dimensions, square grid-cell count method for 2D and segment count method for 1D were followed in the algorithm of FRACRUN. FRACRUN has capable of determine fractal dimensions of many closed polygons on a single surface. In the study, a database composed of uniaxial compressive strength, volumetric block proportion, fractal dimensions and number of blocks for each core was established. Finally, prediction models were developed by regression analyses and compared with the empirical equations proposed by Sonmez et al. (2006). Acknowledgement This study is a product of ongoing project supported by TUBITAK (The Scientific and Technological Research Council of Turkey - Project No: 108Y002). References Bagde, M.N., Raina, A.K., Chakraborty, A.K., Jethwa, J.L., 2002. Rock mass characterization by fractal dimension. Engineering Geology 63, 141-155. Gokceoglu, C., 2002. A fuzzy triangular chart to predict the uniaxial compressive strength of the Ankara agglomerates from their petrographic composition. Engineering Geology, 66 (1-2), 39-51. Gulbin, Y.L., Evangulova, E.B., 2003. Morphometry of quartz aggregates in granites: fractal images referring to nucleation and growth processes. Mathematical Geology 35 (7), 819-833 Hamdi, E., 2008. A fractal description of simulated 3D discontinuity networks. Rock Mechanics and Rock Engineering 41, 587-599. Hyslip, J.P., Vallejo, L.E., 1997. Fractals analysis of the roughness and size distribution of granular materials. Engineering Geology 48, 231-244. Kahraman, S., Alber, M., Fener, M. and Gu

  5. The effects of expansion strength on large-scale structures in compressible free shear layers

    Science.gov (United States)

    Smith, K. M.; Dutton, J. C.

    2001-07-01

    Planar visualizations of two compressible free shear layers were performed immediately downstream of centered expansions of differing strengths in order to assess the influence of expansion strength on the embedded large-scale structures. The free shear layers studied here were formed through the separation of an approach flow, either a Mach 2.0 stream or a Mach 2.5 stream, from a planar backstep. In addition to side-view and end-view visualizations, spatial correlations (computed from large image ensembles) and laser Doppler velocimetry surveys of the free shear layers were also examined to discern relationships between the structure dynamics and the underlying pre- and postexpansion velocity fields. The instantaneous images clearly illustrate that ellipsoidal, highly coherent structures were present in both shear layers downstream of the expansion corner. The dissimilar expansion strengths did not appear to produce qualitatively different structures in the shear layers; however, as compared to the weaker expansion, the stronger expansion did result in an increase in the growth rate of the large-scale structures, apparently from an augmentation of the ?U/?y production term in the TKE equation. Furthermore, quantitative measurements of the mean structure geometry, as determined from the spatial correlation fields, revealed that a stronger expansion strength resulted in a larger aspect ratio of the mean structures (i.e., the structures were stretched preferentially in the streamwise and transverse directions as compared to the spanwise direction during the expansion process). Quadrant decompositions of the instantaneous velocity fluctuations within the approach boundary layers and within the free shear layers indicated a definite increase in structure organization across the expansion region, which is in contrast with studies of expanded supersonic boundary layers without separation. The instantaneous image data, spatial correlations, and velocity decompositions uniformly suggest that the separation process itself, and not the expansion strength, is the primary influence on initial eddy structure in the postexpansion free shear layer.

  6. Improvement compressive strength of concrete in different curing media by Al2O3 nanoparticles

    International Nuclear Information System (INIS)

    Research highlights: ? Al2O3 nanoparticles. ? Mechanical properties. ? Physical properties. ? Thermal properties. ? Microstructure. - Abstract: In the present work, the effect of curing medium on microstructure together with physical, mechanical and thermal properties of concrete containing Al2O3 nanoparticles has been investigated. Portland cement was partially replaced by Al2O3 nanoparticles with the average particle size of 15 nm and the specimens were cured in water and saturated limewater for specific ages. The results indicate that Al2O3 nanoparticles up to maximum of 2.0% produces concrete with improved compressive strength and setting time when the specimens cured in saturated limewater. The optimum level of replacement for cured specimens in water is 1.0 wt%. Although the limewater reduces the strength of concrete without nanoparticles when it is compared with the specimens cured in water, curing the specimens bearing nanoparticles in saturated limewater results in more strengthening gel formation around Al2O3 nanoparticles causes more rapid setting time together with high strength. 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 Al2O3 nanoparticles cub>O3 nanoparticles could improve mechanical and physical properties of the specimens.

  7. 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.

  8. 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

  9. Predicting the compressive strength of cemented uranium tailings filling body based on adaptive neuron-fuzzy inference system

    International Nuclear Information System (INIS)

    A series uniaxial compressive tests were conducted by using an RMT-150B testing system to investigate the effects of slurry concentration, cement-tailings ratio and curing period on compressive strength of uranium tailings filling body, the stress-strain curve of the backfilling body was obtained, and their failure characteristics were analyzed. On the basis of the test results, an adaptive neuron-fuzzy inference system (ANFIS) model for predicting compressive strength is established using the adaptive neuron-fuzzy inference system based on slurry concentration, cement-tailings ratio and curing period. It was found that there is direct proportion relation between the compressive strength and affecting factors such as slurry concentration, cement-tailings ratio and curing period; the failure law of filling body follows the plastic-elastic-plastic failure model; the ANFIS model provides predictions with high accuracy about 94%, which proves to be a new approach for estimation of compressive strength of uranium tailings filling body. (authors)

  10. Compressive yield strength of the nanocrystalline Cu with Al2O3 dispersoid

    International Nuclear Information System (INIS)

    Research highlights: ? 0.2% yield stress of the HPed nc-Cu with the 4 vol.% of the Al2O3 dispersoids is as high as 863 MPa ? The major contribution to total yield strength of the nc-Cu (25.5 nm) with Al2O3 (4 nm, 4 vol.%) dispersoid is attributed to the grain size of the Cu. - Abstract: Nanocrystalline (nc) Cu with Al2O3 dispersoid (?4 vol.%) was successfully synthesized by simple cryo-milling at 210 K with a mixture of Cu2O, 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 Al2O3 dispersoids. The compressive and micro Vickers hardness tests were performed on the HPed materials (nanocrystalline Cu with 4 vol.% of Al2O3 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, Hv = 3?y in MPa. The grain size of the nc-Cu was estimated by XRD of the nc-Cu was estimated by XRD using Scherrer's formula and TEM observation; the Al2O3 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 Al2O3 dispersoid. Two strengthening mechanisms were proposed for high hardness and yield strength of the materials, i.e., grain size and dispersion hardening effects.

  11. 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.

  12. Compressive strength of titanium alloy skin-stringer panels selectively reinforced with boron-aluminum composite.

    Science.gov (United States)

    Herring, H. W.; Carri, R. L.

    1972-01-01

    Description of a method of selectively reinforcing conventional titanium airframe structure with unidirectional boron-aluminum composite attached by brazing which has been successfully demonstrated based on compression tests of short skin-stringer panels. Improvements in structural performance exceeded 25% on an equivalent weight basis over the range from room temperature to 800 F, both in terms of initial buckling and maximum strengths. Room-temperature performance was not affected by prior exposure at 600 F for 1000 hours in air, or by 400 cycles between -65 and 600 F. The experimental results were generally predictable on the basis of existing analytical procedures. No evidence of failure was observed in the braze bond between the boron-aluminum composite and the titanium alloy.

  13. 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 procedure is checked by comparing the present solutions with the finite-element results for actual ship panels with complex shapes of measured initial deflection. It is concluded that the proposed procedure provides quite accurate solutions for the ultimate loads with extremely short computer time.

  14. 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.

  15. 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.

  16. 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

  17. Effect of the Curing Conditions and Superplasticizer on Compressive Strength of Concrete Exposed To High Ambient Temperature of Nawabshah, Pakistan

    OpenAIRE

    Noor Ahmed Memon, Fahad ul Rehman Abro, Ubaidullah Memon, Salihuddin Radin Sumadi

    2014-01-01

    The overall performance of the hardened concrete is believed to be greatly affected by the type and duration of the curing. The influence of the curing on the strength and durability of concrete becomes more significant when the concrete is to be exposed to high ambient temperature of the local area. This paper presents the results of an experimental study conducted to investigate effect of curing conditions and superplasticizer on compressive strength of concr...

  18. 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.

  19. 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.

  20. Modeling particulate self-healing materials and application to uni-axial compression:

    OpenAIRE

    Herbst, Olaf; Luding, Stefan

    2008-01-01

    Using an advanced history dependent contact model for DEM simulations, including elasto-plasticity, viscosity, adhesion, and friction, pressure-sintered tablets are formed from primary particles. These tablets are subjected to unconfined uni-axial compression until and beyond failure. For fast and slow deformation we observe ductile-like and brittle softening, respectively. We propose a model for local self-healing that allows damage to heal during loading such that the material strength of t...

  1. 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.

  2. Improvement of compressive strength of segmentation of zeolites as absorber of Sr-90 liquid waste using coconut fibres

    International Nuclear Information System (INIS)

    The use of the coconut fibres to increase compressive strength of segmentation of zeolites as absorber of Sr-90 liquid waste was studied. The purpose of this research was to find the optimum content and length of fibres that give maximum compressive strength. This research was done with mortar-zeolites specimen of cylinder 2,2 cm diameter and 4,4 cm high, the content of zeolites was 13% volume of specimen, weight ratio of water and cement 0,3, length of fibres 1,5 cm, 2 cm, 2,5 cm, and 3 cm (aspect ratio ± 60, ± 80, ± 100 and ± 120) with the fibres content of each fibre 0%, 0,5%, 0,10%, 0,25%, 0,50%, 0,75%, and 1,00%. Addition of fibres was done with a direction of orientation longitudinal to the specimen. The specimens were tested on 28 days old test specimens. The result showed that addition of coconut fibres until certain content would increase compressive strength. The optimum size of fibres with 92,313 N/MM2 of compressive strength or increased 119,21% of no fibres specimen were 0,50% of volume and 3 cm in length

  3. 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.

  4. Degradation of the compressive strength of unstiffened/stiffened steel plates due to both-sides randomly distributed corrosion wastage

    Scientific Electronic Library Online (English)

    Zorareh Hadj, Mohammad; Esmaeil, Nouri; Mohammad Reza, Khedmati; Mohammad Mahdi, Roshanali.

    2010-09-01

    Full Text Available The paper addresses the problem of the influence of randomly distributed corrosion wastage on the collapse strength and behaviour of unstiffened/stiffened steel plates in longitudinal compression. A series of elastic-plastic large deflection finite element analyses is performed on both-sides randoml [...] y corroded steel plates and stiffened plates. The effects of general corrosion are introduced into the finite element models using a novel random thickness surface model. Buckling strength, post-buckling behaviour, ultimate strength and post-ultimate behaviour of the models are investigated as results of both-sides random corrosion.

  5. Strength of Tantalum at High Pressures through Richtmyer-Meshkov Laser Compression Experiments and Simulations

    Science.gov (United States)

    John, Kristen Kathleen

    Strength at extreme pressures (>1 Mbar or 100 GPa) and high strain rates (106-108 s-1) of materials is not well characterized. The goal of the research outlined in this thesis is to study the strength of tantalum (Ta) at these conditions. The Omega Laser in the Laboratory for Laser Energetics in Rochester, New York is used to create such extreme conditions. Targets are designed with ripples or waves on the surface, and these samples are subjected to high pressures using Omega's high energy laser beams. In these experiments, the observational parameter is the Richtmyer-Meshkov (RM) instability in the form of ripple growth on single-mode ripples. The experimental platform used for these experiments is the "ride-along" laser compression recovery experiments, which provide a way to recover the specimens having been subjected to high pressures. Six different experiments are performed on the Omega laser using single-mode tantalum targets at different laser energies. The energy indicates the amount of laser energy that impinges the target. For each target, values for growth factor are obtained by comparing the profile of ripples before and after the experiment. With increasing energy, the growth factor increased. Engineering simulations are used to interpret and correlate the measurements of growth factor to a measure of strength. In order to validate the engineering constitutive model for tantalum, a series of simulations are performed using the code Eureka, based on the Optimal Transportation Meshfree (OTM) method. Two different configurations are studied in the simulations: RM instabilities in single and multimode ripples. Six different simulations are performed for the single ripple configuration of the RM instability experiment, with drives corresponding to laser energies used in the experiments. Each successive simulation is performed at higher drive energy, and it is observed that with increasing energy, the growth factor increases. Overall, there is favorable agreement between the data from the simulations and the experiments. The peak growth factors from the simulations and the experiments are within 10% agreement. For the multimode simulations, the goal is to assist in the design of the laser driven experiments using the Omega laser. A series of three-mode and four-mode patterns are simulated at various energies and the resulting growth of the RM instability is computed. Based on the results of the simulations, a configuration is selected for the multimode experiments. These simulations also serve as validation for the constitutive model and the material parameters for tantalum that are used in the simulations. By designing samples with initial perturbations in the form of single-mode and multimode ripples and subjecting these samples to high pressures, the Richtmyer-Meshkov instability is investigated in both laser compression experiments and simulations. By correlating the growth of these ripples to measures of strength, a better understanding of the strength of tantalum at high pressures is achieved.

  6. Predictive equations for compressive strength of concrete based on Schmidt hammer rebound and ultrasonic pulse velocity data

    International Nuclear Information System (INIS)

    The compressive strength of concrete is assessed to ensure uniformity of the placed concretc and adequacy of thc strcngth. Non-destructive test (NDT) techniques of ultrasonic pulse velocity and Schmidt rebound hammer tests are commonly used to estimate concrete strength, but the applicability is dependent on correlation of the data with the compressive strength of concrete, the equipment calibration and interpretation of the data. Twenty four standard concrcte cubes were cast respectively from 3 concrete mixes, and tested after 28 days of curing by ultrasonic velocity, rebound hammer and crushing tests. The data were analysed by regression methods to obtain equations for predicting the compression strength of concrete based on the ultrasonic pulse velocity and rebound number. Accurate prediction of the strength of concrete was made when the ultrasonic pulse velocity and the rebound hammer data were combined than when used separately, as the standard error was least. Comparison on the calibration curves of the prediction equations with published plots showed very good agreement. (au)

  7. Development of a method for evaluating tensile and compressive strengths of discontinuous rock mass considering scale effect

    International Nuclear Information System (INIS)

    The purpose of this research is to develop a method for evaluating tensile and compressive strengths considering scale effect which is an old problem in rock mechanics. The method is based on the results of investigation on geometrical information of discontinuity distribution in rock mass. We created a three-dimensional structural model of rock mass with reference to previous studies. Discontinuities in the 3D model were arranged in the supposed cube which is equal to the size of FEM mesh in stability analysis. We clipped arbitrarily-sized two-dimensional cross-section model from the 3D model and calculated tensile and compressive strengths of the 2D model by the stress analysis method we proposed. The relationship between the strength and the size, or the scale effect can be obtained from the method previously describe. The results of the simulations of the proposed method agree with the past test results that the strength and the rate of change of strength decreases with decreasing scale, and show that the scale effect varies according to conditions of geometrical information of discontinuity, confining stress and compression or tension. (author)

  8. 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.

  9. Reliability Assessment of Buckling Strength for Compressed Cylindrical Shells with Interacting Localized Geometric Imperfections

    Directory of Open Access Journals (Sweden)

    Jalal E. Bahaoui

    2010-01-01

    Full Text Available Problem statement: Elastic cylindrical shells are common structures in the fields of civil engineering and engineering mechanics. These thin-walled constructions may undergo buckling when subjected to axial compression. Buckling limits to large extent their strength performance. This phenomenon depends hugely on the initial distributed or localized geometric imperfections that are present on the shell structure. Localized geometric imperfections result in general from the operation of welding strakes to assemble the shell structure. In this study, reliability of buckling strength as it could be affected by shell material and geometry parameters was investigated. The localized geometric imperfections were chosen to be entering and having either a triangular or a wavelet form. Interaction between three localized imperfections had also been considered. Approach: A special software package which was dedicated to buckling analysis of quasi axisymmetric shells was used in order to compute the buckling load via the linear Euler buckling procedure. A set of five factors including shell aspect ratios, defect characteristics and the distance separating the localized initial geometric imperfections had been found to govern the buckling problem. A parametric study was performed to determine their relative influence on the buckling load reduction. Reliability analysis was carried out by using first order reliability method. Results: Wavelet imperfection was found to be more severe than triangular form in the range of low amplitude imperfections. It was shown also by comparison with the single imperfection case that further diminution of the critical load is obtained for three interacting imperfections. The interval distance separating the localized geometric imperfections was found to have important influence on the reliability index. Conclusion/Recommendations: In the he range of investigated parameters, reliability was found to increase with the distance separating the localized geometric imperfections. This can help performing optimal design of assembled strakes.

  10. Core-log integration for rock mechanics using borehole breakouts and rock strength experiments: Recent results from plate subduction margins

    Science.gov (United States)

    Saito, S.; Lin, W.

    2014-12-01

    Core-log integration has been applied for rock mechanics studies in scientific ocean drilling since 2007 in plate subduction margins such as Nankai Trough, Costa Rica margin, and Japan Trench. State of stress in subduction wedge is essential for controlling dynamics of plate boundary fault. One of the common methods to estimate stress state is analysis of borehole breakouts (drilling induced borehole wall compressive failures) recorded in borehole image logs to determine the maximum horizontal principal stress orientation. Borehole breakouts can also yield possible range of stress magnitude based on a rock compressive strength criterion. In this study, we constrained the stress magnitudes based on two different rock failure criteria, the Mohr-Coulomb (MC) criteria and the modified Wiebols-Cook (mWC) criteria. As the MC criterion is the same as that under unconfined compression state, only one rock parameter, unconfined compressive strength (UCS) is needed to constrain stress magnitudes. The mWC criterion needs the UCS, Poisson's ratio and internal frictional coefficient determined by triaxial compression experiments to take the intermediate principal stress effects on rock strength into consideration. We conducted various strength experiments on samples taken during IODP Expeditions 334/344 (Costa Rica Seismogenesis Project) to evaluate reliable method to estimate stress magnitudes. Our results show that the effects of the intermediate principal stress on the rock compressive failure occurred on a borehole wall is not negligible.

  11. An engineering procedure for calculating compressive strength of isogrid cylindrical shells with buckled skin

    Science.gov (United States)

    Heard, W. L., Jr.; Anderson, M. S.; Slysh, P.

    1976-01-01

    An engineering procedure is presented for calculating the compressive buckling strength of isogrid cylinders using shell of revolution techniques and accounting for loading beyond the material proportional limit and/or local buckling of the skin prior to general buckling. A general nondimensional chart is presented which can be used in conjunction with formulas based on simple deformation plasticity theory to calculate postbuckling stiffnesses of the skin. The stiffening grid system is treated as an equivalent isotropic grid layer. Stiffnesses are determined for this grid layer, when loaded beyond the proportional limit, by the same plasticity theory used for the skin and a nonlinear stress-strain curve constructed from simple isogrid-handbook formulas and standard-reference-manual stress-strain curves for the material involved. Comparison of prebuckling strains and buckling results obtained by this procedure with data from a large isogrid-cylinder test is excellent with the calculated buckling load no more than 4 percent greater than the test value.

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

    Science.gov (United States)

    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 applied to them for 30 sec. All samples were incubated for 7 days at 37°C. The CS test was performed by means of a universal testing machine. The data were analyzed by the two-way analysis of variance (ANOVA) and Tukey’s post hoc tests. The level of significance was set at 0.05. Results: The maximum CS was seen in the amalgamator-mixed samples that did not receive ultrasonic agitation. The CS value of amalgamator-mixed samples was significantly higher than manually-mixed ones (P=0.003). Ultrasonic vibration did not change the CS of specimens. Conclusion: According to the results, mixing with amalgamator increases the CS of CEM cement, while ultrasonic vibration had no positive effect. PMID:25834593

  13. Effect of Incorporating Nanoporous Metal Phosphate Materials on the Compressive Strength of Portland Cement

    Directory of Open Access Journals (Sweden)

    Glen E. Fryxell

    2008-03-01

    Full Text Available Nanoporous metal phosphate (NP-MPO materials are being developed for removal of contaminant oxyanions (As(OHO32−, CrO42−, and TcO4−, and cations (mercury, cadmium, and lead from water and waste streams. Following sequestration, incorporation of metal laden NP-MPOs as a portion of cement formulation would provide an efficient and low-cost way to immobilize metal laden NP-MPOs in an easily handled waste form suitable for permanent disposal. There are no known investigations regarding the incorporation of NP-MPOs in concrete and the effects imparted on the physical and mechanical properties of concrete. Results of this investigation demonstrated that incorporating of NP-MPO materials requires additional water in the concrete formulation which decreases the compressive strength. Thus, incorporation of NP-MPOs in concrete may not serve as an efficient means for long-term disposal.

  14. 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.

  15. Compressive Strength and Water Absorption of Pervious Concrete that Using the Fragments of Ceramics and Roof Tiles

    Science.gov (United States)

    Prahara, E.; Meilani

    2014-03-01

    Pervious concrete was introduced in America in 2003, popularized by Dan Brown and used as a rigid pavement in the open parking lot. Rigid pavement using pervious concrete can absorb water in the surface to go straight through the concrete to the ground below.This water flow is one of the benefit of using the pervious concrete. Using of wastes such as broken roof and ceramics tiles are not commonly used in Indonesia. Utilization these kind of wastes is predicted lower the compressive strength of pervious concrete as they are used as a substitute for coarse aggregate.In this research, pervious concrete is made using a mixture of the fragment of ceramics and roof tiles.This research using broken ceramics and roof tiles with a grain size that loose from 38 mm sieve, retained on 19 mm sieve and the coarse aggregate from crushed stone that loose 12.5 mm sieve, retained on 9.5 mm sieve. The water cement ratio is 0.3 and to assist the mixing process, the addition of addictive in pervious concrete is used.The size of coarse aggregate used in the mixture affects the strength of pervious concrete. The larger the size of aggregate, the obtained compressive strength becomes smaller. It also affects the density of pervious concrete. The using of mixture of ceramics and roof tiles only reduce 2 MPa of pervious concrete compressive strength so this mixture can be used as a substitute for coarse aggregate with a maximum portion of 30 %. The high porosity of the specimens causes the reduction of pervious concrete density that affect the compressive strength. This high level of porosity can be seen from the high level of water absorption that exceed the required limit of water infiltration.

  16. Compressive Strength and Water Absorption of Pervious Concrete that Using the Fragments of Ceramics and Roof Tiles

    Directory of Open Access Journals (Sweden)

    Prahara E.

    2014-03-01

    Full Text Available Pervious concrete was introduced in America in 2003, popularized by Dan Brown and used as a rigid pavement in the open parking lot. Rigid pavement using pervious concrete can absorb water in the surface to go straight through the concrete to the ground below.This water flow is one of the benefit of using the pervious concrete. Using of wastes such as broken roof and ceramics tiles are not commonly used in Indonesia. Utilization these kind of wastes is predicted lower the compressive strength of pervious concrete as they are used as a substitute for coarse aggregate.In this research, pervious concrete is made using a mixture of the fragment of ceramics and roof tiles.This research using broken ceramics and roof tiles with a grain size that loose from 38 mm sieve, retained on 19 mm sieve and the coarse aggregate from crushed stone that loose 12.5 mm sieve, retained on 9.5 mm sieve. The water cement ratio is 0.3 and to assist the mixing process, the addition of addictive in pervious concrete is used.The size of coarse aggregate used in the mixture affects the strength of pervious concrete. The larger the size of aggregate, the obtained compressive strength becomes smaller. It also affects the density of pervious concrete. The using of mixture of ceramics and roof tiles only reduce 2 MPa of pervious concrete compressive strength so this mixture can be used as a substitute for coarse aggregate with a maximum portion of 30 %. The high porosity of the specimens causes the reduction of pervious concrete density that affect the compressive strength. This high level of porosity can be seen from the high level of water absorption that exceed the required limit of water infiltration.

  17. Influence of Curing Age and Mix Composition on Compressive Strength of Volcanic Ash Blended Cement Laterized Concrete

    OpenAIRE

    Babafemi A.J.; Olusola K. O.; Olawuyi B.J.

    2012-01-01

    This study investigates the influence of curing age and mix proportions on the compressive strength of volcanic ash (VA) blended cement laterized concrete. A total of 288 cubes of 100mm dimensions were cast and cured in water for 3, 7, 28, 56, 90 and 120 days of hydration with cement replacement by VA and sand replacement by laterite both ranging from 0 to 30% respectively while a control mix of 28-day target strength of 25N/mm2 (using British Method) was adopted. The results show that the co...

  18. Effect of sintering temperature on microstructure and compressive strength of B4C-AlSi eutectic alloy

    International Nuclear Information System (INIS)

    The block neutron absorber of B4C based on Al-Si eutectic alloy has been prepared by powder-metallurgy method. The effects of sinter temperature on microstructure, compressive strength, and ductility of sintered billets have been investigated. It has been shown that the sintering temperature decides sensitively the compressive strength and ductility of sintered billets. Sintered under 550, 555, 560, and 565 degree C, the billet shows different states, such as sub-sintered, best-sintered, over-sintered, and molten. Sintered under 550 degree C, the powder have not been metallurgically combined with each other. Beyond 560 degree C, the billets are molten. The 555 degree C is the best sintering temperature, under which the powder have been partly melted and the metallurgical combination has been occurred, then the billets have a better ductility. (authors)

  19. 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.

  20. 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.

  1. In situ micropillar compression reveals superior strength and ductility but an absence of damage in lamellar bone

    Science.gov (United States)

    Schwiedrzik, Jakob; Raghavan, Rejin; Bürki, Alexander; Lenader, Victor; Wolfram, Uwe; Michler, Johann; Zysset, Philippe

    2014-07-01

    Ageing societies suffer from an increasing incidence of bone fractures. Bone strength depends on the amount of mineral measured by clinical densitometry, but also on the micromechanical properties of the hierarchical organization of bone. Here, we investigate the mechanical response under monotonic and cyclic compression of both single osteonal lamellae and macroscopic samples containing numerous osteons. Micropillar compression tests in a scanning electron microscope, microindentation and macroscopic compression tests were performed on dry ovine bone to identify the elastic modulus, yield stress, plastic deformation, damage accumulation and failure mechanisms. We found that isolated lamellae exhibit a plastic behaviour, with higher yield stress and ductility but no damage. In agreement with a proposed rheological model, these experiments illustrate a transition from a ductile mechanical behaviour of bone at the microscale to a quasi-brittle response driven by the growth of cracks along interfaces or in the vicinity of pores at the macroscale.

  2. In situ micropillar compression reveals superior strength and ductility but an absence of damage in lamellar bone.

    Science.gov (United States)

    Schwiedrzik, Jakob; Raghavan, Rejin; Bürki, Alexander; LeNader, Victor; Wolfram, Uwe; Michler, Johann; Zysset, Philippe

    2014-07-01

    Ageing societies suffer from an increasing incidence of bone fractures. Bone strength depends on the amount of mineral measured by clinical densitometry, but also on the micromechanical properties of the hierarchical organization of bone. Here, we investigate the mechanical response under monotonic and cyclic compression of both single osteonal lamellae and macroscopic samples containing numerous osteons. Micropillar compression tests in a scanning electron microscope, microindentation and macroscopic compression tests were performed on dry ovine bone to identify the elastic modulus, yield stress, plastic deformation, damage accumulation and failure mechanisms. We found that isolated lamellae exhibit a plastic behaviour, with higher yield stress and ductility but no damage. In agreement with a proposed rheological model, these experiments illustrate a transition from a ductile mechanical behaviour of bone at the microscale to a quasi-brittle response driven by the growth of cracks along interfaces or in the vicinity of pores at the macroscale. PMID:24907926

  3. Studies on the Determination of Compressive Strengths of Different Grades of Rice Husk Ash—An Ecofriendly Concrete

    OpenAIRE

    Patnaikuni Chandan Kumar; Venugopal, Nutulapati V. S.; Palli Malleswara Rao

    2013-01-01

    Rice Husk Ash (RHA) Concrete is an eco friendly concrete and has evolved as an innovative technology, capable of achieving the status of being an outstanding advancement in the sphere of concrete technology. The utilization of Rice Husk Ash (RHA) will reduce the dumping of rice husk as well as reduce the construction cost. In this communication investigations for the determination of residual compressive strength of M30 & 40 grades of RHA concretes exposed at different temperatures were carr...

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

    Science.gov (United States)

    Díaz-Díaz, Floriberto; de J. Cano-Barrita, Prisciliano F.; Balcom, Bruce J.; Solís-Nájera, Sergio E.; Rodríguez, Alfredo O.

    2013-01-01

    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.

  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. The Value Compressive Strength and Split Tensile Strength on Concrete Mixture With Expanded Polystyrene Coated by Surfactant Span 80 as a Partial Substitution of Fine Aggregate

    OpenAIRE

    Hidayat Irpan; Siauwantara Alice

    2014-01-01

    The value of the density normal concrete which ranges between 2200–2400 kg/m3. Therefore the use of Expanded Polystyrene (EPS) as a subitute to fine aggregate can reduce the density of concrete. The purpose this research is to reduce the density of normal concrete but increase compressive strength of EPS concrete, with use surfactant as coating for the EPS. Variables of substitution percentage of EPS and EPS coated by surfactant are 5%,10%,15%,20%,25%. Method of concrete mix design based on...

  7. 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

  8. 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)

  9. 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.

  10. 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).

  11. 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

  12. 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. Th...

  13. Theory of DDT in unconfined flames

    CERN Document Server

    Khokhlov, A M; Wheeler, J C; Wheeler, J Craig

    1996-01-01

    This paper outlines a theoretical approach for predicting the onset of detonation in unconfined turbulent flames which is relevant both to problems of terrestrial combustion and to thermonuclear burning in Type Ia supernovae. Two basic assumuptions are made: 1) the gradient mechanism is the inherent mechanism that leads to DDT in unconfined conditions, and 2) the sole mechanism for preparing the gradient in induction time is by turbulent mixing and local flame quenching. The criterion for DDT is derived in terms of the one-dimensional detonation wave thickness, the laminar flame speed, and the laminar flame thickness in the reactive gas. This approach gives a lower-bound criterion for DDT for conditions where shock preheating, wall effects, and interactions with obstacles are absent. Regions in parameter space where unconfined DDT can and cannot occur are determined. A subsequent paper will address these issues specifically in the astrophysical context.

  14. 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.

  15. Influence Factor Analysis on Strength of Lime-Fly Ash Loess

    OpenAIRE

    Yufen Zhang; Zhiquan Zhang

    2013-01-01

    Lime-fly ash loess is composed of fly ash, lime and loess. It is a new material in subgrade backfill. Main factors to influence the strength of lime-fly ash loess are age, amount of fly ash and lime, ratio of fly ash to lime (1:K), and moisture content. In order to observe the effect of each factor influencing the strength of lime-fly ash loess and find out the relationship between each other, this paper adopted orthogonal test design to conduct unconfined compression tests. The result shows ...

  16. A study on the compressive and tensile strength of foamed concrete containing pulverized bone as a partial replacement of cement

    International Nuclear Information System (INIS)

    In this study, structural properties of foamed aerated concrete with and without pulverized bone were investigated. These properties are workability, plastic and testing densities, compressive strength, and tensile strength at the design density of 1600kg/m/sub 3/. The tensile strength was evaluated by subjecting 150 x 150 x750mm unreinforced foamed concrete beams to flexural test and 150x300mm cylinder specimens were subjected to splitting test. 150mm cube specimens were used for the determination of both the compressive strength and the testing density of the foamed aerated concrete. The plastic density was investigated using a container of known volume, and its workability determined using the slump test. The pulverized bone content was varied from 0 to 20% at interval of 5%. The specimens without the pulverized bone served as the control. At the designed density of 1600 kg/m/sub 3/, the results for the control specimens at 28-day curing age are 15.43 and 13.89N/mm/sub 2/ for air-and water-cured specimens respectively. The modulus of rupture and splitting tensile strength are 2.53 and 1.63N/mm/sub 2/ respectively. The results for specimens with pulverized bone did not differ significantly from the specimens without pulverized bone. From the results of this investigation, it can be concluded that foamed aerated concrete used for this study has potential for structural applications. Also pulverized bone can be used to reduce (partially replace) the quantity of cement used in aerated concrete production; thus ridding our environment of potentially harmful wastes, as well as reduce the consumption of non-renewable resources. (author)

  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. 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...

  19. 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.

  20. Compressive Strength and Water Absorption of Pervious Concrete that Using the Fragments of Ceramics and Roof Tiles

    OpenAIRE

    Prahara E.; Meilani

    2014-01-01

    Pervious concrete was introduced in America in 2003, popularized by Dan Brown and used as a rigid pavement in the open parking lot. Rigid pavement using pervious concrete can absorb water in the surface to go straight through the concrete to the ground below.This water flow is one of the benefit of using the pervious concrete. Using of wastes such as broken roof and ceramics tiles are not commonly used in Indonesia. Utilization these kind of wastes is predicted lower the compressive strength ...

  1. 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

  2. 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

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

    Directory of Open Access Journals (Sweden)

    Pedram Masoud

    2014-03-01

    Full Text Available 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.

  4. 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.

  5. 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.

  6. Shear strengths of aluminium nitride and titanium diboride under plane shock wave compression

    OpenAIRE

    Dandekar, D.

    1994-01-01

    This work compares the estimates of shear strengths of aluminium nitride and titanium diboride obtained (a) from the simultaneous measurements of longitudinal and lateral stress by means of manganin gauges under plane shock wave loading with (b) those calculated from the offset between hydrodynamic and shock Hugoniot of these materials. The results of this work show that whereas the estimates of the shear strength obtained by these two methods for titanium diboride are consistent with one ano...

  7. 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.

  8. 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 ...

  9. Calcium Phosphate Bone Cements Including Sugar Surfactants: Part One—Porosity, Setting Times and Compressive Strength

    OpenAIRE

    Juliette Fitremann; Ariane Bercier; Olivier Lignon; Stéphane Gonçalves

    2010-01-01

    Addition of sugar surfactants, sucrose fatty acid esters and alkylpolyglucosides, to calcium phosphate cement designed for bone reconstruction is described. Thanks to their surface activity and through their adsorption at the surface of the calcium phosphate particles, they both induced a strong increase in the porosity (quantified by Image Analysis) and brought a very good workability. Other properties typically studied for these cements are reported, including setting times, compressive str...

  10. Improvement compressive strength of cementitious composites in different curing media by incorporating ZrO2 nanoparticles

    Directory of Open Access Journals (Sweden)

    Mohammad Hossein Rafieipour

    2012-04-01

    Full Text Available In the present work, the effect of curing medium on microstructure, physical, mechanical and thermal properties of ZrO2 nanoparticles blended concrete has been investigated. ZrO2 nanoparticles were partially used instead of cement by 0.5, 1.0, 1.5 and 2.0 weight percent. Curing of the specimens was carried out in water and saturated limewater for 7, 28 and 90 days. The results indicate that ZrO2 nanoparticles up to maximum of 2.0% produces cementitious composite with improved compressive strength by curing in saturated limewater. The optimum level of replacement for the specimens cured in water was 1.0 weight percent. ZrO2 nanoparticles can improve the filler effects and also the high activity of fine particles substantially increases the quantity of strengthening gel. Although the limewater reduces the strength of concrete without nanoparticles when compared with the specimens cured in water, curing the specimens in saturated limewater results in more strengthening gel formation around ZrO2 nanoparticles blended concrete causes high strength.

  11. Improvement compressive strength of cementitious composites in different curing media by incorporating ZrO2 nanoparticles

    Scientific Electronic Library Online (English)

    Mohammad Hossein, Rafieipour; Ali, Nazari; Mohammad Ali, Mohandesi; Gholamreza, Khalaj.

    2012-04-01

    Full Text Available In the present work, the effect of curing medium on microstructure, physical, mechanical and thermal properties of ZrO2 nanoparticles blended concrete has been investigated. ZrO2 nanoparticles were partially used instead of cement by 0.5, 1.0, 1.5 and 2.0 weight percent. Curing of the specimens was [...] carried out in water and saturated limewater for 7, 28 and 90 days. The results indicate that ZrO2 nanoparticles up to maximum of 2.0% produces cementitious composite with improved compressive strength by curing in saturated limewater. The optimum level of replacement for the specimens cured in water was 1.0 weight percent. ZrO2 nanoparticles can improve the filler effects and also the high activity of fine particles substantially increases the quantity of strengthening gel. Although the limewater reduces the strength of concrete without nanoparticles when compared with the specimens cured in water, curing the specimens in saturated limewater results in more strengthening gel formation around ZrO2 nanoparticles blended concrete causes high strength.

  12. Poly-l-lactide/sodium alginate/chitosan microsphere hybrid scaffolds made with braiding manufacture and adhesion technique: Solution to the incongruence between porosity and compressive strength.

    Science.gov (United States)

    Lin, Jia-Horng; Chen, Chih-Kuang; Wen, Shih-Peng; Lou, Ching-Wen

    2015-07-01

    Bone scaffolds require a three-dimensional structure, high porosity, interconnected pores, adequate mechanical strengths, and non-toxicity. A high porosity is incongruent with mechanical strengths. Therefore, this study combines a braiding method and microsphere solution to create bone scaffolds with a high porosity and sufficient mechanical strengths. First, poly-l-lactide (PLLA) plied yarns are braided into 5-, 10-, 15-, 20-, and 25-layer hollow braids, and then thermally treated at 165°C for various durations. Next, sodium alginate (SA) microspheres, cross-linked with CaCl2 solution with various concentrations, are combined with PLLA porous braided bone scaffolds to form PLLA/SA/CS microsphere hybrid scaffolds, which are then observed for surface observation, and tested for porosity, water contact angle, compressive strength, MTT assay, bioactivity, alkaline phosphatase (ALP) assay, cell attachment, and statistical analyses. The test results show that the layer amount of the bone scaffold is proportional to the compressive strength. With the same number of layers, the compressive strength is inversely proportional to the concentration of the CaCl2 solution. The results of surface observation, porosity, and water contact angle tests show that PLLA/SA/CS microsphere hybrid scaffolds possess a high porosity and good hydrophilicity; as a result, the braiding manufacture and the bonding technique effectively solve the confliction between porosity and mechanical strength. The concentration of CaCl2 does not pertain to cell activity and ALP results, exemplified by good cell attachment on bone scaffolds for each specification. PMID:25953547

  13. Elevated Temperature, Residual Compressive Strength of Impact-Damaged Sandwich Structure Manufactured Out-of-Autoclave

    Science.gov (United States)

    Grimsley, Brian W.; Sutter, James K.; Burke, Eric R.; Dixon, Genevieve D.; Gyekenyesi, Thomas G.; Smeltzer, Stanley S.

    2012-01-01

    Several 1/16th-scale curved sandwich composite panel sections of a 10 m diameter barrel were fabricated to demonstrate the manufacturability of large-scale curved sections using minimum gauge, [+60/-60/0]s, toughened epoxy composite facesheets co-cured with low density (50 kilograms per cubic meters) aluminum honeycomb core. One of these panels was fabricated out of autoclave (OoA) by the vacuum bag oven (VBO) process using Cycom(Registered Trademark) T40-800b/5320-1 prepreg system while another panel with the same lay-up and dimensions was fabricated using the autoclave-cure, toughened epoxy prepreg system Cycom(Registered Trademark) IM7/977-3. The resulting 2.44 m x 2 m curved panels were investigated by non-destructive evaluation (NDE) at NASA Langley Research Center (NASA LaRC) to determine initial fabrication quality and then cut into smaller coupons for elevated temperature wet (ETW) mechanical property characterization. Mechanical property characterization of the sandwich coupons was conducted including edge-wise compression (EWC), and compression-after-impact (CAI) at conditions ranging from 25 C/dry to 150 C/wet. The details and results of this characterization effort are presented in this paper.

  14. 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 87MPa, which was significantly higher than C3S (25MPa) and MPC (64MPa). The setting time could be adjusted between 3min and 29min 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

  15. The strength of single crystal copper under uniaxial shock compression at 100 GPa.

    OpenAIRE

    Murphy, Wj; Higginbotham, A.; Kimminau, G.; Barbrel, B.; Bringa, Em; Hawreliak, J.; Kodama, R.; Koenig, M.; Mcbarron, W.; Meyers, Ma; Nagler, B.; Ozaki, N.; Park, N.; Remington, B.; Rothman, S.

    2010-01-01

    In situ x-ray diffraction has been used to measure the shear strain (and thus strength) of single crystal copper shocked to 100 GPa pressures at strain rates over two orders of magnitude higher than those achieved previously. For shocks in the [001] direction there is a significant associated shear strain, while shocks in the [111] direction give negligible shear strain. We infer, using molecular dynamics simulations and VISAR (standing for 'velocity interferometer system for any reflector') ...

  16. 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 comp...

  17. A Discrete Element Model for Predicting Shear Strength and Degradation of Rock Joint by Using Compressive and Tensile Test Data

    Science.gov (United States)

    Kazerani, T.; Yang, Z. Y.; Zhao, J.

    2012-09-01

    A discrete element model is proposed to examine rock strength and failure. The model is implemented by UDEC, which is developed for this purpose. The material is represented as a collection of irregular-sized deformable particles interacting at their cohesive boundaries. The interface between two adjacent particles is viewed as a flexible contact whose constitutive law controls the material fracture and fragmentation properties. To reproduce rock anisotropy, an orthotropic cohesive law is developed for the contacts, which allows their shear and tensile behaviors to be different from each other. Using a combination of original closed-form expressions and statistical calibrations, a unique set of the contact microparameters are found based on the uniaxial/triaxial compression and Brazilian tension test data of a plaster. Applying the obtained microparameters, joint specimens, made of the same plaster, are simulated, where the comparison of the obtained results to laboratory data shows a reasonable agreement.

  18. Use of steel fibres recovered from waste tyres as reinforcement in concrete: pull-out behaviour, compressive and flexural strength.

    Science.gov (United States)

    Aiello, M A; Leuzzi, F; Centonze, G; Maffezzoli, A

    2009-06-01

    The increasing amount of waste tyres worldwide makes the disposition of tyres a relevant problem to be solved. In the last years over three million tons of waste tyres were generated in the EU states [ETRA, 2006. Tyre Technology International - Trends in Tyre Recycling. http://www.etra-eu.org]; most of them were disposed into landfills. Since the European Union Landfill Directive (EU Landfill, 1999) aims to significantly reduce the landfill disposal of waste tyres, the development of new markets for the tyres becomes fundamental. Recently some research has been devoted to the use of granulated rubber and steel fibres recovered from waste tyres in concrete. In particular, the concrete obtained by adding recycled steel fibres evidenced a satisfactory improvement of the fragile matrix, mostly in terms of toughness and post-cracking behaviour. As a consequence RSFRC (recycled steel fibres reinforced concrete) appears a promising candidate for both structural and non-structural applications. Within this context a research project was undertaken at the University of Salento (Italy) aiming to investigate the mechanical behaviour of concrete reinforced with RSF (recycled steel fibres) recovered from waste tyres by a mechanical process. In the present paper results obtained by the experimental work performed up to now are reported. In order to evaluate the concrete-fibres bond characteristics and to determine the critical fibre length, pull-out tests were initially carried out. Furthermore compressive strength of concrete was evaluated for different volume ratios of added RSF and flexural tests were performed to analyze the post-cracking behaviour of RSFRC. For comparison purposes, samples reinforced with industrial steel fibres (ISF) were also considered. Satisfactory results were obtained regarding the bond between recycled steel fibres and concrete; on the other hand compressive strength of concrete seems unaffected by the presence of fibres despite their irregular geometric properties. Finally, flexural tests furnished in some cases results comparable to those obtained when using ISF as concerns the post-cracking behaviour. PMID:19167204

  19. 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.

  20. 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.

  1. Hierarchical Order of Influence of Mix Variables Affecting Compressive Strength of Sustainable Concrete Containing Fly Ash, Copper Slag, Silica Fume, and Fibres

    OpenAIRE

    Sakthieswaran Natarajan; Ganesan Karuppiah

    2014-01-01

    Experiments have been conducted to study the effect of addition of fly ash, copper slag, and steel and polypropylene fibres on compressive strength of concrete and to determine the hierarchical order of influence of the mix variables in affecting the strength using cluster analysis experimentally. While fly ash and copper slag are used for partial replacement of cement and fine aggregate, respectively, defined quantities of steel and polypropylene fibres were added to the mixes. It is found f...

  2. The effects of geometrical imperfections on the ultimate strength of aluminium stiffened plates subject to combined uniaxial compression and lateral pressure

    OpenAIRE

    Khedmati, Mohammad Reza; Pedram, Masoud; Rigo, Philippe

    2012-01-01

    The present study aims at determining the effects of the geometrical imperfections on the ultimate strength and load-carrying capacity of aluminium stiffened plates under combined axial compression and lateral pressure. The finite element models proposed by the Committee III.1 ‘Ultimate Strength’ of ISSC’2003 are used in the present investigation. Initial imperfections as proposed by ISSC committee as well as those recommended by Ship Structure Committee are considered in the a...

  3. 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.

  4. Hierarchical order of influence of mix variables affecting compressive strength of sustainable concrete containing fly ash, copper slag, silica fume, and fibres.

    Science.gov (United States)

    Natarajan, Sakthieswaran; Karuppiah, Ganesan

    2014-01-01

    Experiments have been conducted to study the effect of addition of fly ash, copper slag, and steel and polypropylene fibres on compressive strength of concrete and to determine the hierarchical order of influence of the mix variables in affecting the strength using cluster analysis experimentally. While fly ash and copper slag are used for partial replacement of cement and fine aggregate, respectively, defined quantities of steel and polypropylene fibres were added to the mixes. It is found from the experimental study that, in general, irrespective of the presence or absence of fibres, (i) for a given copper slag-fine aggregate ratio, increase in fly ash-cement ratio the concrete strength decreases and with the increase in copper slag-sand ratio also the rate of strength decrease and (ii) for a given fly ash-cement ratio, increase in copper slag-fine aggregate ratio increases the strength of the concrete. From the cluster analysis, it is found that the quantities of coarse and fine aggregate present have high influence in affecting the strength. It is also observed that the quantities of fly ash and copper slag used as substitutes have equal "influence" in affecting the strength. Marginal effect of addition of fibres in the compression strength of concrete is also revealed by the cluster analysis. PMID:24707213

  5. 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)

  6. Compressive strength of masonry (f{sub m}{prime}) for the Oak Ridge Y- 12 Plant, Hollow Clay Tile Walls

    Energy Technology Data Exchange (ETDEWEB)

    Fricke, K.E.; Flanagan, R.D.

    1995-04-17

    Prism tests have been performed on the HCT walls. The three groups of data were treated as separate data points and averaged. The recommended effective compressive strengths for HCT walls are 735 psi for single wythe 6- and 8-in. walls, and 495 psi for the double wythe 13-in. walls.

  7. 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.

    -, - (2014). ISSN 1359-5997 R&D Projects: GA MK(CZ) DF11P01OVV001 Keywords : compressive strength * density * in situ testing * non-destructive testing (NDT) * small size loading jack * wood Subject RIV: AL - Art, Architecture, Cultural Heritage Impact factor: 1.714, year: 2014

  8. 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.

  9. 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...

  10. RESISTENCIA A LA COMPRESION DE ANGULOS DOBLES SEPARADOS COMPRESSION / STRENGTH OF FACE TO FACE DOUBLE ANGLES

    Scientific Electronic Library Online (English)

    LUIS, GARZA; LUIS, LARA; JUAN, POSADA.

    2006-03-01

    Full Text Available Siendo una práctica muy difundida en Colombia la construcción de armaduras con ángulos dobles enfrentados en lugar de ángulos espalda con espalda como se hace en la mayor parte del mundo, se realizó una investigación para comparar su comportamiento y calibrar los criterios de diseño de las especific [...] aciones existentes. En este trabajo se muestra que las consideraciones para ángulos espalda con espalda no se pueden aplicar directamente, y se propone una metodología para poder estimar la resistencia de ángulos enfrentados. Abstract in english Is a common practice in Colombia the construction of trusses made up of double angles face to face instead of angles back to back like the worldwide practice An investigation was carried out to compare its behavior and to calibrate the actual design criteria . It is shown in this work that considera [...] tions usually made for back to back angles can not be applied directly, and a methodology is proposed in order to estimate the strength of face to face double angles.

  11. 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.

  12. An Assessment of the Compressive Strength of Glass Reinforced Plastic Waste Filled Concrete for Potential Applications in Construction

    Directory of Open Access Journals (Sweden)

    Asokan Pappu

    2010-03-01

    Full Text Available

    Efforts were made to recycle Glass reinforced plastic (GRP waste powder in concrete products and assess its compressive strength to comply with British Standards for use in construction applications. More than 90 GRP waste-filled concrete specimens were developed using the concentration of 5%, 15%, 30% and 50% (w/w. The findings revealed that the increase in concentration of GRP waste decreased the compressive strength. However, increase in curing duration resulted in improving the compressive strength of concrete. The findings of this work pave the way for further GRP waste recycling in precast construction products for use in various applications.

     

  13. Unconfined Aquifer Flow Theory - from Dupuit to present

    CERN Document Server

    Mishra, Phoolendra K

    2013-01-01

    Analytic and semi-analytic solution are often used by researchers and practicioners to estimate aquifer parameters from unconfined aquifer pumping tests. The non-linearities associated with unconfined (i.e., water table) aquifer tests makes their analysis more complex than confined tests. Although analytical solutions for unconfined flow began in the mid-1800s with Dupuit, Thiem was possibly the first to use them to estimate aquifer parameters from pumping tests in the early 1900s. In the 1950s, Boulton developed the first transient well test solution specialized to unconfined flow. By the 1970s Neuman had developed solutions considering both primary transient storage mechanisms (confined storage and delayed yield) without non-physical fitting parameters. In the last decade, research into developing unconfined aquifer test solutions has mostly focused on explicitly coupling the aquifer with the linearized vadose zone. Despite the many advanced solution methods available, there still exists a need for realism ...

  14. 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.

  15. 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.

  16. 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.

  17. [The design, preparation and compressive strength testing of interbody fusion cages made from a composite of multi-amino acid copolymer/tri-calcium phosphate].

    Science.gov (United States)

    Zhou, Chungnang; Song, Yueming; Tu, Chongqi; Pei, Fuxing; Duan, Hong; Liu, Limin; Li, Hong

    2011-12-01

    This research was to design and prepare interbody fusion cages using composite materials of multi-amino acid copolymer/tri-calcium phosphate (MAACP/TCP) and to test compressive strength of the cages. 16 specimens of C3-4 segments from female adult goats were scanned by X-ray to exclude disease of cervical spine, and then anatomical data were measured, i. e. disc space height of C3-4 segment (DSH), sagittal diameter of C3 lower endplate (SDLE3), sagittal diameter of C4 upper endplate (SDUE4), coronary diameter of C3 lower endplate (CDLE3), and coronary diameter of C4 upper endplate (CDUE4). According to the anatomical data, we designed and prepared the interbody fusion cage using the composite of MAACP/TCP and titanium with the same sizes. The MAACP/TCP Cages were made with the method of injection molding and finish machining, and titanium Cages were made with machining. In the testing of compressive strength of Cages, the specimens were divided into three groups, tricortical iliac crest bone group (isolated from goats), MAACP/TCP Cage group and titanium Cage group. There were 8 specimens in every group with the same sizes, the length of 12 mm, the width of 10 mm, and the height of 6 mm. The compressive strength of all specimens was tested on a universal testing machine. The values of DSH, SDLE3, SDUE4, CDLE3 and CDUE4 were (4.78 +/- 0.17) mm, (15.06 +/- 0.53) mm, (12.46 +/- 0.44) mm, (14.47 +/- 0.51) mm and (12.15 +/- 0.65) mm, respectively. MAACP/TCP Cage was successfully designed and made with a compressive strength of 76.34 MPa, which was much higher than that of tricortical iliac crest bone (18.41 MPa). The maximal loading of universal testing machine was 50 000 N, so the compressive strength of titanium Cages, whose value should be more than 541.35 MPa, could not be tested precisely. It is feasible to make cages with MAACP/TCP composite, and the compressive strength of MAACP/TCP Cages was much higher than that of tricortical iliac crest bone isolated from goats. PMID:22295701

  18. 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

  19. 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.

  20. Modeling decomposition of unconfined rigid polyurethane foam

    International Nuclear Information System (INIS)

    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

  1. Effects of humeral head compression taping on the isokinetic strength of the shoulder external rotator muscle in patients with rotator cuff tendinitis.

    Science.gov (United States)

    Kim, Moon-Hwan; Oh, Jae-Seop

    2015-01-01

    [Purpose] The purpose of this study was to examine the effects of humeral head compression taping (HHCT) on the strength of the shoulder external rotator muscle in patients with rotator cuff tendinitis. [Subjects and Methods] Twenty patients with rotator cuff tendinitis were recruited. The shoulder external rotator strength was measured using a Biodex isokinetic dynamometer system. A paired t-test was performed to evaluate within-group differences in the strength of the shoulder external rotator muscle. [Results] Significantly higher shoulder external rotator peak torque and peak torque per body weight were found in the HHCT condition than in the no-taping condition. [Conclusion] HHCT may effectively increase the shoulder external rotator muscle strength in patients with rotator cuff tendinitis. PMID:25642053

  2. Compressive strength and compressive fatigue limit of conventional and high viscosity posterior resin composites / Resistência a compressão e limite de fadiga compressiva de resinas compostas convencional e de alta viscosidade para dentes posteriores

    Scientific Electronic Library Online (English)

    Letícia, Brandão; Gelson Luis, Adabo; Luís Geraldo, Vaz; José Roberto Cury, Saad.

    2005-12-01

    Full Text Available O objetivo deste estudo foi comparar a resistência à compressão e o limite de fadiga compressiva de três resinas compostas indicadas para dentes posteriores (Filtek P-60, Surefil e Prodigy Condensable) e uma universal (Z-100). Corpos-de-prova cilíndricos (8 mm de altura x 4 mm de diâmetro) foram usa [...] dos. O teste dinâmico foi realizado usando-se o método escada e a relação entre limite de fadiga compressiva, e resistência à compressão também foi calculada (n = 15). Os dados de resistência à compressão e de limite de fadiga compressiva foram submetidos à Anova e ao teste de Tukey. O compósito Z-100 apresentou maior resistência à compressão (307,20 MPa) que Surefil (266,93 MPa) e Prodigy Condensable (222,08 MPa). A resistência de Filtek P-60 (270,44 MPa) foi similar à de Z-100 e à de Surefil, enquanto Prodigy Condensable apresentou a menor resistência à compressão. No teste de limite de fadiga compressiva, Filtek P-60 mostrou maior valor (184,20 MPa) que Prodigy Condensable (155,50 MPa). Os compósitos Surefil (165,74 MPa) e Z-100 (161,22 MPa) mostraram-se similares a Filtek P-60 e Prodigy Condensable. A relação limite de fadiga compressiva/resistência à compressão foi de 70,01% para Prodigy Condensable, 68,11% para Filtek P-60, 62,09% para Surefil e 52,48% para Z-100. Foi concluído que o compósito universal Z-100 foi mais sensível ao teste dinâmico que os materiais de alta viscosidade. Abstract in english The purpose of this study was to compare the compressive strengths and compressive fatigue limits of three posterior composite resins (Filtek P-60, Surefil and Prodigy Condensable) and a universal restorative composite (Z-100). Cylindrical specimens (8 mm in length x 4 mm in diameter) were used. The [...] dynamic test was performed using the staircase method, and the ratio between compressive fatigue limit and compressive resistance was also calculated (n = 15). The compressive strength and compressive fatigue limit data were analyzed by Anova and Tukey’s test. The Z-100 composite demonstrated higher compression strength (307.20 MPa) than Surefil (266.93 MPa) and Prodigy Condensable (222.08 MPa). The resistance of Filtek P-60 (270.44 MPa) was similar to the resistances of Z-100 and Surefil, while Prodigy Condensable presented the lowest compressive strength. In the compressive fatigue limit tests, Filtek P-60 demonstrated a higher value (184.20 MPa) than Prodigy Condensable (155.50 MPa). Surefil (165.74 MPa) and Z-100 (161.22 MPa) presented limits similar to those of Filtek P-60 and Prodigy Condensable. The compressive fatigue limit/compressive strength ratio was 70.01% for Prodigy Condensable, 68.11% for Filtek P-60, 62.09% for Surefil and 52.48% for Z-100. It was concluded that the Z-100 universal composite was more sensitive to the dynamic test than the high viscosity materials.

  3. 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.

  4. 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...

  5. 'Schmidt Hammer Rebound' users guide: IBM-PC/AT computer calculation of uniaxial compressive strength using the Schmidt hammer

    Energy Technology Data Exchange (ETDEWEB)

    Issard, M.; Aston, T.R.C.

    1986-08-01

    The 'Schmidt Hammer Rebound' a computer program calculating the uniaxial compressive strength of rock using Schmidt hammer rebound index values. The program is written in BASIC A version 3.10 for an IBM-PC/AT. Originally developed to determine the surface hardness of concrete the Schmidt hammer has subsequently been used to obtain a simple field index for rock/strata exposures. 5 refs.

  6. Application of support vector machines and relevance vector machines in predicting uniaxial compressive strength of volcanic rocks

    Science.gov (United States)

    Ceryan, Nurcihan

    2014-12-01

    The uniaxial compressive strength (UCS) of intact rocks is an important and pertinent property for characterizing a rock mass. It is known that standard UCS tests are destructive, expensive and time-consuming task, which is particularly true for thinly bedded, highly fractured, foliated, highly porous and weak rocks. Consequently, prediction models have become an attractive alternative for engineering geologists. In the last several years, a new, alternative kernel-based technique, support vector machines (SVMs), has been popular in modeling studies. Despite superior SVM performance, this technique has certain significant, practical drawbacks. Hence, the relevance vector machines (RVMs) approach has been proposed to recast the main ideas underlying SVMs in a Bayesian context. The primary purpose of this study is to examine the applicability and capability of RVM and SVM models for predicting the UCS of volcanic rocks from NE Turkey and comparing its performance with ANN models. In these models, the porosity and P-durability index representing microstructural variables are the input parameters. The study results indicate that these methods can successfully predict the UCS for the volcanic rocks. The SVM and RVM performed better than the ANN model. When these kernel based models are considered, RVM model found successful in terms of statistical performance criterions (e.g., performance index, PI values for training and testing data are computed as 1.579 and 1.449). These values for SVM are 1.509 and 1.307. Although SVM and RVM models are powerful techniques, the RVM run time was considerably faster, and it yielded the highest accuracy.

  7. 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

  8. Laboratory Investigation on Compressive Strength and Micro-structural Features of Foamed Concrete with Addition of Wood Ash and Silica Fume as a Cement Replacement

    Directory of Open Access Journals (Sweden)

    Othuman Mydin M.A.

    2014-01-01

    Full Text Available Wood Ash (WA and Silica Fume (SF exhibit good cementation properties and have great potential as supplementary binder materials for the concrete production industry. This study will focus on enhancing the micro-structural formation and compressive strength of foamed concrete with the addition of WA and SF. A total of 3 mixes were prepared with the addition of WA and SF at various cement replacement levels by total binder weight. For this particular study, the combination of WA (5%, 10%, and 15% by binder weight and SF (5%, 10%, and 15% by binder weight were utilized as supplementary binder materials to produce foamed concrete mixes. As was made evident from micrographs obtained in the study, the improvement observed in the compressive strength of the foamed concrete was due to a significant densification in the microstructure of the cement paste matrix in the presence of WA and SF hybrid supplementary binders. Experimental results indicated that the combination of 15% SF and 5% WA by binder weight had a more substantial influence on the compressive strength of foamed concrete compared to the control mix. Furthermore, the addition of WA and SF significantly prolonged the setting times of the blended cement paste of the foamed concrete.

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

    Directory of Open Access Journals (Sweden)

    Klimchouk, A.B.

    2003-01-01

    Full Text Available 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 and confined settings by the analysis of morphometric parameters of typical cave patterns. Two samples of typical cave systems formed in the respective settings are compared. The sample that represents unconfined speleogenesis consists of solely limestone caves, whereas gypsum caves of this type tend to be less dendritic. The sample that represents confined speleogenesis consists of both limestone and gypsum maze caves. The comparison shows considerable differences in average values of some parameters between the settings. Passage network density (the ratio of the cave length to the area of the cave field, km/km2 is one order of magnitude greater in confined settings than in unconfined (average 167.3 km/km2 versus 16.6 km/km2. Similarly, an order of magnitude difference 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 settings than in unconfined (29.7 % versus 6.4 %. This indicates that conduit permeability in confined aquifers is appreciably easier to target with drilling than the widely spaced conduits in unconfined aquifers.

  10. A numerical investigation into the effects of parabolic curvature on the buckling strength and behaviour of stiffened plates under in-plane compression

    Scientific Electronic Library Online (English)

    Mohammad Reza, Khedmati; Pedram, Edalat.

    2010-09-01

    Full Text Available The main targets of this research are mainly divided in to two parts: (1) identifying the effects of parabolic curvature on the buckling strength and behaviour of stiffened plates under in-plane compression, (2) generating practical graphs for extracting eigenvalue buckling stress of parabolic curve [...] d stiffened plate to dimensionless parameters. A parametric model for study of the problem is created. The model includes different parameters related to plate, stiffeners and also parabolic curvature. Three distinct sensitivity cases are assumed. In each sensitivity case, many different models are analysed and their buckling strengths are obtained using a finite element commercial program (ANSYS). Buckling strength and behaviour of all models with different ratios of parabolic curvature are compared to each other.

  11. 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.

  12. 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...

  13. Specimen size effects on the compressive strength and Weibull modulus of nuclear graphite of different coke particle size: IG-110 and NBG-18

    Science.gov (United States)

    Chi, Se-Hwan

    2013-05-01

    The effects of specimen size on the compressive strength and Weibull modulus were investigated for nuclear graphite of different coke particle sizes: IG-110 and NBG-18 (average coke particle size for IG-110: 25 ?m, NBG-18: 300 ?m). Two types of cylindrical specimens, i.e., where the diameter to length ratio was 1:2 (ASTM C 695-91 type specimen, 1:2 specimen) or 1:1 (1:1 specimen), were prepared for six diameters (3, 4, 5, 10, 15, and 20 mm) and tested at room temperature (compressive strain rate: 2.08 × 10-4 s-1). Anisotropy was considered during specimen preparation for NBG-18. The results showed that the effects of specimen size appeared negligible for the compressive strength, but grade-dependent for the Weibull modulus. In view of specimen miniaturization, deviations from the ASTM C 695-91 specimen size requirements require an investigation into the effects of size for the grade of graphite of interest, and the specimen size effects should be considered for Weibull modulus determination.

  14. Specimen size effects on the compressive strength and Weibull modulus of nuclear graphite of different coke particle size: IG-110 and NBG-18

    International Nuclear Information System (INIS)

    The effects of specimen size on the compressive strength and Weibull modulus were investigated for nuclear graphite of different coke particle sizes: IG-110 and NBG-18 (average coke particle size for IG-110: 25 ?m, NBG-18: 300 ?m). Two types of cylindrical specimens, i.e., where the diameter to length ratio was 1:2 (ASTM C 695-91 type specimen, 1:2 specimen) or 1:1 (1:1 specimen), were prepared for six diameters (3, 4, 5, 10, 15, and 20 mm) and tested at room temperature (compressive strain rate: 2.08 × 10?4 s?1). Anisotropy was considered during specimen preparation for NBG-18. The results showed that the effects of specimen size appeared negligible for the compressive strength, but grade-dependent for the Weibull modulus. In view of specimen miniaturization, deviations from the ASTM C 695-91 specimen size requirements require an investigation into the effects of size for the grade of graphite of interest, and the specimen size effects should be considered for Weibull modulus determination

  15. Empirical relations between rock strength and physical properties in sedimentary rocks

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Chandong; Zoback, Mark D. [Department of Geophysics, Stanford University, Palo Alto, CA 94305-2215 (United States); Khaksar, Abbas [GeoMechanics International, Inc., Perth, WA 6000 (Australia)

    2006-05-16

    In this study, 31 empirical equations are summarized that relate unconfined compressive strength and internal friction angle of sedimentary rocks (sandstone, shale, and limestone and dolomite) to physical properties (such as velocity, modulus, and porosity). These equations can be used to estimate rock strength from parameters measurable with geophysical well logs. The ability of these equations to fit laboratory-measured strength and physical property data that were compiled from the literature is reviewed. Results from this study can be useful for petroleum industry when a range of geomechanical problems such as wellbore stability and in-situ stress measurements should be addressed without direct strength information available. While some equations work reasonably well (for example, some strength-porosity relationships for sandstone and shale), rock strength variations with individual physical property measurements scatter considerably, indicating that most of the empirical equations are not sufficiently generic to fit all the data published on rock strength and physical properties. This emphasizes the importance of local calibration before one utilizes any of the empirical relationships presented. Nonetheless, some reasonable correlations can be found between geophysical properties and rock strength that can be useful for applications related to wellbore stability where having a lower bound estimate of in situ rock strength is especially useful. (author)

  16. Evaluation of Friction Coefficient and Compressive Strength of Graphite Layers of Nuclear Fuel for HTGR by Kinetic Nano-Indentation Technique

    International Nuclear Information System (INIS)

    It is necessary to estimate various mechanical properties such as wear and fatigue resistances of thin coated layers of coated fuel because of the limited test conditions and dimensions. In this study, a method so called 'Kinetic Indentation Technique' was applied to evaluate wear and fatigue behaviors. The method is based on both the proportion of elastic and plastic deformation and values obtained by micro-hardness test. In this study, compressive strength and friction coefficient of graphite layers on nuclear fuel are obtained from the diagram of load-indentation depth time and vilified the values

  17. 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.

  18. Three-dimensional groundwater velocity field in an unconfined aquifer under irrigation

    International Nuclear Information System (INIS)

    A method for three-dimensional flow velocity calculation has been developed to evaluate unconfined aquifer sensitivity to areal agricultural contamination of groundwater. The methodology of Polubarinova-Kochina is applied to an unconfined homogeneous compressible or incompressible anisotropic aquifer. It is based on a three-dimensional groundwater flow model with a boundary condition on the moving surface. Analytical solutions are obtained for a hydraulic head under the influence of areal sources of circular and rectangular shape using integral transforms. Two-dimensional Hantush formulas result from the vertical averaging of the three-dimensional solutions, and the asymptotic behavior of solutions is analyzed. Analytical expressions for flow velocity components are obtained from the gradient of the hydraulic head field. Areal and temporal variability of specific yield in groundwater recharge areas is also taken into account. As a consequence of linearization of the boundary condition, the operation of any irrigation system with respect to groundwater is represented by superposition of the operating wells and circular and rectangular source influences. Combining the obtained solutions with Dagan or Neuman well functions, one can develop computer codes for the analytical computation of the three-dimensional groundwater hydraulic head and velocity component distributions. Methods for practical implementation are discussed. (Author) (20 refs., 4 figs.)

  19. 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.

  20. Controlled low-strength material using fly ash and AMD sludge.

    Science.gov (United States)

    Gabr, M A; Bowders, J J

    2000-09-15

    Controlled low-strength material (CLSM) is a cementitious material with properties similar to stabilized soil. After hardening, CLSM provides adequate strength in bearing capacity and support but can also be easily excavated. To be classified as a CLSM, the material must have a compressive strength between 450 kPa (65 psi) and 8400 kPa (1200 psi). Typical CLSM contains coal-combustion fly ash (FA), cement, water and fine or coarse aggregate. In this paper, physical and strength properties of CLSM formed by combining sludge, a by-product from the treatment of acid mine drainage (AMD), with Class F FA are investigated. The sludge is a lime-based waste product that when combined with FA, exhibits self-hardening characteristics similar to cement. A main focus of this research is to develop a CLSM mix in which by-product material utilization is maximized while satisfying workability and performance requirements. A mixture of 10% AMD sludge, 2.5% Portland cement (PC), 87.5% Class F FA (dry wt.%) with water provided unconfined compressive strength values within the range for classification as CLSM. This mixture satisfies the excavatability and walkability requirements as well as the hardening time and stability criteria. PMID:10936537

  1. Physical-Based Inversion of Confined and Unconfined Aquifers under Unknown Boundary Conditions

    Science.gov (United States)

    Zhang, Y.; Jiao, J.

    2013-12-01

    An inverse method is developed to simultaneously estimate multiple hydraulic conductivities, source/sink strengths, and boundary conditions (BC), for two-dimensional confined and unconfined aquifers under non-pumping or pumping conditions (Jiao & Zhang, 2013). The method is successfully tested on problems with regular and irregular geometries, different heterogeneity variances (maximum Kmax/Kmin is 10,000), and error magnitudes. Under non-pumping conditions, when error-free observed data are used to condition the inversion, the estimated conductivities and recharge rates are accurate within 8% of the true values. When data contain increasing errors, the estimated parameters become less accurate. For problems where the underlying parameter variation is unknown, equivalent conductivities and average recharge rates can be determined. Under pumping (and/or injection) conditions, a hybrid formulation is developed to address local source/sink effects as well as the impact of different types of BCs on drawdowns. Accurate results can be gained without local grid refinement at wells, inversion is thus successful with coarse grids leading to high computation efficiency. Flux measurements are not needed for the inversion to succeed; data requirement of the method is not much different from that of interpreting classic well tests. Finally, inversion accuracy is not sensitive to the degree of nonlinearity of the flow equations. Performance of the inverse method for confined and unconfined aquifer problems is similar in terms of the accuracy of the estimated parameters, the recovered head field (includling the BC), and the speed of the nonlinear solver. A select problem is presented in a set of figures (all relevant quantities have a consistent set of units). J Jiao and Y Zhang (2013) Physical-Based Inversion of Confined and Unconfined Aquifers under Unknown Boundary Conditions, Advances in Water Resources, in review. Unconfined problem with a pair of pumping and injection wells: Q1=-500 and Q2=500. (a) true model with four conductivities (K1=5, K2=50, K3=100, K4=150) and a recharge rate N=0.01. Location of a profile, AB, is shown. (b) head contours of the true model; (c) head contours by inversion with 31 cells when the measured heads contain ×0.25% errors. (d) head profiles along AB by the true model and with inversion under increasing measurement errors.

  2. Distinct signaling mechanisms regulate migration in unconfined versus confined spaces.

    Science.gov (United States)

    Hung, Wei-Chien; Chen, Shih-Hsun; Paul, Colin D; Stroka, Kimberly M; Lo, Ying-Chun; Yang, Joy T; Konstantopoulos, Konstantinos

    2013-09-01

    Using a microchannel assay, we demonstrate that cells adopt distinct signaling strategies to modulate cell migration in different physical microenvironments. We studied ?4?1 integrin-mediated signaling, which regulates cell migration pertinent to embryonic development, leukocyte trafficking, and melanoma invasion. We show that ?4?1 integrin promotes cell migration through both unconfined and confined spaces. However, unlike unconfined (2D) migration, which depends on enhanced Rac1 activity achieved by preventing ?4/paxillin binding, confined migration requires myosin II-driven contractility, which is increased when Rac1 is inhibited by ?4/paxillin binding. This Rac1-myosin II cross talk mechanism also controls migration of fibroblast-like cells lacking ?4?1 integrin, in which Rac1 and myosin II modulate unconfined and confined migration, respectively. We further demonstrate the distinct roles of myosin II isoforms, MIIA and MIIB, which are primarily required for confined and unconfined migration, respectively. This work provides a paradigm for the plasticity of cells migrating through different physical microenvironments. PMID:23979717

  3. Improvement compressive strength of cementitious composites in different curing media by incorporating ZrO2 nanoparticles

    OpenAIRE

    Mohammad Hossein Rafieipour; Ali Nazari; Mohammad Ali Mohandesi; Gholamreza Khalaj

    2012-01-01

    In the present work, the effect of curing medium on microstructure, physical, mechanical and thermal properties of ZrO2 nanoparticles blended concrete has been investigated. ZrO2 nanoparticles were partially used instead of cement by 0.5, 1.0, 1.5 and 2.0 weight percent. Curing of the specimens was carried out in water and saturated limewater for 7, 28 and 90 days. The results indicate that ZrO2 nanoparticles up to maximum of 2.0% produces cementitious composite with improved compressive stre...

  4. 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. ...

  5. Stability of Strength and Deformation Characteristics of Expanded Polystyrene (EPS within the Time of Long-Term Investigation of Creep Strain under Permanent Compressive Loading

    Directory of Open Access Journals (Sweden)

    Saulius VAITKUS

    2013-05-01

    Full Text Available The results of investigation of strength (s10 %, scr and deformability (E characteristics of expanded polystyrene specimens are presented. The results are based on the short-term compression in the organization of long-term creep study. For the experiments identical specimens stored 5 years at ambient temperature (23 ±2 °C and relative humidity (50 ±5 % as well specimens after removal long-term loading were used. There were established, that difference between experimental values of stress and initial modulus of tested expanded polystyrene specimens with confidence probability P = 90 % (on-sided test is negligible (random.DOI: http://dx.doi.org/10.5755/j01.ms.19.2.4442

  6. 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.

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

    International Nuclear Information System (INIS)

    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

  8. 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 ?.

  9. Study on Fatigue Strength of Aluminum-Silicon Alloy and Spheroidal Graphite Cast Iron under Compressive Load

    Science.gov (United States)

    Kawakami, Yoshimichi; Deguchi, Akio

    Fatigue tests of aluminum-silicon alloy A4032FD and spheroidal graphite cast iron FCD600 were carried out under cyclic compressive loading using circumferential notched round bar specimens. Non-propagating cracks were observed at the notch bottom of the specimens after 1×107 load cycles. It is considered that residual tensile stress caused by plastic deformation at the notch bottom is the driving force of crack propagation. Therefore we calculated the range of stress intensity factor ?K of residual stress at the notch bottom. The ?K was also compared with effective threshold stress intensity U·?Kthto predict the crack depth. It is considered that the crack propagation rate disappears when ?K

  10. 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.

  11. Spontaneous Transition of Turbulent Flames to Detonations in Unconfined Media

    CERN Document Server

    Poludnenko, Alexei Y; Oran, Elaine S

    2011-01-01

    Deflagration-to-detonation transition (DDT) can occur in environments ranging from experimental and industrial systems to astrophysical thermonuclear (type Ia) supernovae explosions. Substantial progress has been made in explaining the nature of DDT in confined systems with walls, internal obstacles, or pre-existing shocks. It remains unclear, however, whether DDT can occur in unconfined media. Here we use direct numerical simulations (DNS) to show that for high enough turbulent intensities unconfined, subsonic, premixed, turbulent flames are inherently unstable to DDT. The associated mechanism, based on the nonsteady evolution of flames faster than the Chapman-Jouguet deflagrations, is qualitatively different from the traditionally suggested spontaneous reaction wave model, and thus does not require the formation of distributed flames. Critical turbulent flame speeds, predicted by this mechanism for the onset of DDT, are in agreement with DNS results.

  12. 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

  13. Spontaneous Transition of Turbulent Flames to Detonations in Unconfined Media

    OpenAIRE

    Poludnenko, Alexei Y.; Gardiner, Thomas A.; Oran, Elaine S.

    2011-01-01

    Deflagration-to-detonation transition (DDT) can occur in environments ranging from experimental and industrial systems to astrophysical thermonuclear (type Ia) supernovae explosions. Substantial progress has been made in explaining the nature of DDT in confined systems with walls, internal obstacles, or pre-existing shocks. It remains unclear, however, whether DDT can occur in unconfined media. Here we use direct numerical simulations (DNS) to show that for high enough turbu...

  14. Barometric fluctuations in wells tapping deep unconfined aquifers.

    Science.gov (United States)

    Weeks, E.P.

    1979-01-01

    Barometric effects on water levels in unconfined aquifers can be computed by solution of the differential equation governing the flow of gas in the unsaturated zone subject to the appropriate boundary conditions. Solutions to this equation for two sets of boundary conditions were applied to compute water level response in a well tapping the Ogallala Formation near Lubbock, Texas from simultaneous microbarograph records. -from Author

  15. Dynamic Tensile Strength of Low Temperature Ice and Kuiper Belt Size Distributions

    Science.gov (United States)

    Ahrens, Thomas J.; Fat'yanov, O. V.; Engelhardt, H.; Fraser, W. C.

    2009-09-01

    We model mutual gravitationally driven impact interactions in a nearly gas-free environment of the Kuiper belt (KB) and use low-temperature (annular stainless steel target rings. New measurements were partially confined, in not initially contacting concentric target rings. Later shots used unconfined configurations with ice pellets affixed to aluminum foil. Circumferential confinement is known to increase the material damage threshold upon both compression and tensile loading. Previous confinement in LA is the main cause of the above discrepancy. Present tensile strengths are only a few times higher than 0.7 - 3.0 MPa summarized in Petrovic (2003) for quasistatic tension at 10-7 to 10-3 s-1 strain rate.

  16. Elevated Temperature Compressive Strength Properties of Oxide Dispersion Strengthened NiAl After Cryo-milling and Roasting in Nitrogen

    Science.gov (United States)

    Whittenberger, J. Daniel; Grahle, Peter; Arzt, Eduard; Hebsur, Mohan

    1998-01-01

    In an effort to superimpose two different elevated temperature strengthening mechanisms in NiAl, several lots of oxide dispersion strengthened (ODS) NiAl powder have been cryo-milled in liquid nitrogen to introduce AlN particles at the grain boundaries. As an alternative to cryo-milling, one lot of ODS NiAl was roasted in nitrogen to produce AlN. Both techniques resulted in hot extruded AlN-strengthened, ODS NiAl alloys which were stronger than the base ODS NiAl between 1200 and 1400 K. However, neither the cryo-milled nor the N2-roasted ODS NiAl alloys were as strong as cryo-milled binary NiAl containing like amounts of AlN. The reason(s) for the relative weakness of cryo-milled ODS NiAl is not certain; however the lack of superior strength in N2-roasted ODS NiAl is probably due to its relatively large AlN particles.

  17. A revisit of drawdown behavior during pumping in unconfined aquifers

    Science.gov (United States)

    Mao, Deqiang; Wan, Li; Yeh, Tian-Chyi J.; Lee, Cheng-Haw; Hsu, Kuo-Chin; Wen, Jet-Chau; Lu, Wenxi

    2011-05-01

    In this study, the S-shaped log-log drawdown-time curve typical of pumping tests in unconfined aquifers is reinvestigated via numerical experiments. Like previous investigations, this study attributes the departure of the S shape from the drawdown-time behavior of the confined aquifer to the presence of an "additional" source of water. Unlike previous studies, this source of water is reinvestigated by examining the temporal and spatial evolution of the rate of change in storage in an unconfined aquifer during pumping. This evolution is then related to the transition of water release mechanisms from the expansion of water and compaction of the porous medium to the drainage of water from the unsaturated zone above the initial water table and initially saturated pores as the water table falls during the pumping of the aquifer. Afterward, the 1-D vertical drainage process in a soil column is simulated. Results of the simulation show that the transition of the water release mechanisms in the 1-D vertical flow without an initial unsaturated zone can also yield the S-shaped drawdown-time curve as in an unconfined aquifer. We therefore conclude that the transition of the water release mechanisms and vertical flow in the aquifer are the cause of the S-shaped drawdown-time curve observed during pumping in an unconfined aquifer. We also find that the moisture retention characteristics of the aquifer material have greater impact than its relative permeability characteristics on the drawdown-time curve. Furthermore, influences of the spatial variability of saturated hydraulic conductivity, specific storage, and saturated moisture content on the drawdown curve in the saturated zone are found to be more significant than those of other unsaturated properties. Finally, a cross-correlation analysis reveals that the drawdown at a location in a heterogeneous unconfined aquifer is mainly affected by local heterogeneity near the pumping and observation wells. Applications of a model assuming homogeneity to the estimation of aquifer parameters as such may require a large number of observation wells to obtain representative parameter values. In conclusion, we advocate that the governing equation for variably saturated flow through heterogeneous media is a more appropriate and realistic model that explains the S-shaped drawdown-time curves observed in the field.

  18. 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.

    1268-12-01

    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.

  19. Formulation of the effects of strain rate on concrete strength. No.1. Application of the split Hopkinson pressure bar method to impact test, and the compressive strength test results

    International Nuclear Information System (INIS)

    An impact test apparatus of concrete material was developed with both hydraulic loading system and Split Hopkinson Pressure Bar type loading system. A data processing method to distinguish an incident wave and a reflected wave was developed in the Split Hopkinson Pressure Bar type system to be capable of precise traces of average stresses at the both ends of the test specimen by strain gauges positioned near the test specimen on the pressure bars. In this apparatus, 10 cm diameter bars were used taking account of the maximum aggregate size of the concrete. To mitigate the calculation error in the inversion method due to the stress wave dispersion and radial effect, a shock absorbing material was used to omit the high frequency components of the incident wave and deform the test specimen uniformly. As a result, the estimated errors as to the longitudinal stress distribution were acceptable during the impact loading time to deform an test specimen completely. According to the test results, the strain rate effect on the compressive concrete strength from one-thousandth/sec to one-hundred/sec was made clear. Moreover, a moisture presence in the specimen was regarded as an important factor influencing the strain rate effect on the concrete material. (author)

  20. Two-dimensional physical-based inversion of confined and unconfined aquifers under unknown boundary conditions

    Science.gov (United States)

    Jiao, Jianying; Zhang, Ye

    2014-03-01

    An inverse method is developed to simultaneously estimate multiple hydraulic conductivities, source/sink strengths, and boundary conditions, for two-dimensional confined and unconfined aquifers under non-pumping or pumping conditions. The method incorporates noisy observed data (hydraulic heads, groundwater fluxes, or well rates) at measurement locations. With a set of hybrid formulations, given sufficient measurement data, the method yields well-posed systems of equations that can be solved efficiently via nonlinear optimization. The solution is stable when measurement errors are increased. The method is successfully tested on problems with regular and irregular geometries, different heterogeneity patterns and variances (maximum Kmax/Kmin tested is 10,000), and error magnitudes. Under non-pumping conditions, when error-free observed data are used, the estimated conductivities and recharge rates are accurate within 8% of the true values. When data contain increasing errors, the estimated parameters become less accurate, as expected. For problems where the underlying parameter variation is unknown, equivalent conductivities and average recharge rates can be estimated. Under pumping (and/or injection) conditions, a hybrid formulation is developed to address these local source/sink effects, while different types of boundary conditions can also exert significant influences on drawdowns. Local grid refinement near wells is not needed to obtain accurate results, thus inversion is successful with coarse inverse grids, leading to high computation efficiency. Furthermore, flux measurements are not needed for the inversion to succeed; data requirement of the method is thus not much different from that of interpreting classic well tests. Finally, inversion accuracy is not sensitive to the degree of nonlinearity of the flow equations. Performance of the inverse method for confined and unconfined aquifer problems is similar in terms of the accuracy of the estimated parameters, the recovered head fields, and the solver speed.

  1. 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.

  2. 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.

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

    Directory of Open Access Journals (Sweden)

    Salem, Amin

    2013-04-01

    Full Text Available 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 ºC. 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 ?m. This enhancement in reliability is valuable in packed towers.Para conocer el efecto del tamaño de partícula de nefelina sienita sobre las propiedades fisicoquímicas de los anillos Raschig cerámicos, este fundente fue molido a diferentes tiempos. Las composiciones se prepararon mediante la mezcla de la arcilla caolinítica illitica y las partículas pre-molidas. Los anillos se obtuvieron en una extrusora de laboratorio y luego fueron sinterizados a 1200 ºC. La fiabilidad mecánica de las muestras sinterizadas se describe matemáticamente por la teoría de Weibull y el efecto de pre-molienda del fundente en el módulo de Weibull se evaluó midiendo la resistencia a la compresión diametral. El módulo de Weibull y la resistencia fueron los criterios para seleccionar el rango de tamaño de partícula adecuado de nefelina sienita para la fabricación de los anillos que se determinó estaba entre 53 y 75 ?m comprobándose que influye considerablemente en la microestructura de los mismos. La fiabilidad alcanzada fue muy valiosa para la utilización de estos anillos como relleno en ldistintos tipos de torres.

  4. 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.

  5. 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.

  6. Avaliação da resistência à compressão, resistência à tração e formação de microfissuras em concretos produzidos com diferentes tipos de cimentos, quando aplicado um pré-carregamento de compressão / Evaluation of compressive strength, tensile strength and microcracking formation in concretes produced with different cements, when a preloading of compression is applied

    Scientific Electronic Library Online (English)

    Geilma Lima, Vieira; Denise Carpena Coitinho Dal, Molin.

    2011-03-01

    Full Text Available Muitas empresas construtoras que querem competitividade no mercado buscam soluções para aumentar a velocidade de seus empreendimentos, tal como a redução do tempo de execução da estrutura, redução do tempo de escoramento e execução antecipada das alvenarias, sem respeitar o prazo mínimo de cura do c [...] oncreto. A retirada precoce do escoramento submete a estrutura a uma carga prematura. Os danos causados pela incompleta reação de hidratação e cura do concreto podem desencadear um processo generalizado de formação de microfissuras. O presente estudo avaliou o comportamento de diferentes tipos de concretos produzidos com quatro diferentes tipos de cimentos, quando submetidos a uma carga precoce de compressão, analisando-se suas propriedades mecânicas. A análise incluiu a avaliação da resistência à compressão, resistência à tração e microestrutura interna do concreto, através de microscopia eletrônica de varredura. Os resultados indicaram que há possibilidade de um processo de formação de microfissuras causadas pelo carregamento precoce no concreto e que há tendência de diminuição dos valores de resistência à tração. Entretanto, verificou-se, mediante análise de microscopia, que as microfissuras formadas pelo carregamento precoce tendem a se recuperar se o processo de cura for retomado ou se cessar o pré-carregamento. Abstract in english Many construction companies seeking competitive advantage in the market search for solutions to increase the speed of their projects, such as reducing the structure execution time, cutting shoring time and expediting the construction of masonry walls, disregarding the minimal time limit for curing c [...] oncrete. Early withdrawal of the concrete structure shoring submits it to a premature load. The damage caused by incomplete hydration reaction and curing of the concrete can trigger a widespread process of formation of microcracks. This study examined the behavior of different types of concrete produced with four different types of cements, subjected to an early compressive load, analyzing their mechanical properties. The analysis included an evaluation of the compressive strength, tensile strength and internal microstructure of the concrete, using scanning electron microscopy. The results indicated that there is a possibility of forming microcracks due to preloading on concrete, and that there is a tendency of reaching lower tensile strength values. However, microscopic analysis showed that the microcracks formed by preloading tend to recover if either the curing process is resumed or if early loading stops.

  7. Ensaio de cravação pneumática de pino para avaliação da resistência à compressão de juntas de assentamento de alvenaria estrutural / Pneumatic pin penetration test to evaluate the compressive strength of mortar bedding on structural masonry

    Scientific Electronic Library Online (English)

    Alexandre Lima, Oliveira; Pedro Lehmkuhl, Damiani; Igor Fernando Reitz, Ribeiro; Rafael Andrade, Souza; Luciana Maltez Lengler, Calçada.

    2012-06-01

    Full Text Available Ensaios não destrutivos têm sido propostos e usados para avaliação das condições de alvenarias estruturais, para controle de qualidade e propriedades dos materiais in loco. Entretanto, a maioria dos métodos funciona apenas para argamassas com baixa resistência à compressão ([...] as para avaliação qualitativa, além de não serem práticos para uso em campo, demandando muito tempo para a realização das avaliações. Em função disso, um pinador pneumático foi utilizado para avaliar a profundidade de penetração de pinos de aço e correlacioná-la com a resistência à compressão de argamassas em laboratório. O trabalho mostrou que há uma boa correlação entre a profundidade de cravação de pinos e a resistência à compressão das argamassas, além de ser um ensaio prático, rápido e fácil de ser realizado in loco. Abstract in english Nondestructive tests have been proposed and used for the evaluation of structural masonry conditions, quality control, and properties of materials in-situ. However, most of nondestructive methods work only with mortars with low compressive strength ([...] not practical for in-situ use, requiring too much time to perform evaluations. For those reasons, a pneumatic pin penetration test was used to evaluate the penetration depth of a steel probe and correlate it with the compressive strength of mortar in a laboratory. The study has shown a good correlation between the penetration depth of pins and the compressive strength of mortars, besides proving to be a practical test, which is fast and easy to implement in situ.

  8. 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.

  9. 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.

  10. Probing confined and unconfined hemoglobin molecules with photoacoustics

    Science.gov (United States)

    Saha, Ratan K.; Karmakar, Subhajit; Roy, Madhusudan

    2014-03-01

    Photoacoustic (PA) measurements on confined and unconfined hemoglobin molecules are presented. In vitro experiments were performed with porcine red blood cells (RBCs) at 532 and 1064 nm at various laser fluences. Fluence was gradually changed from 8 to 21 mJ/cm2/pulse for 532 nm and 353 to 643 mJ/cm2/pulse for 1064 nm. PA signals from suspended RBCs (SRBCs) and hemolyzed RBCs (HRBCs) were measured using a needle hydrophone at hematocrits ranging from 10 to 60%. PA amplitude was found to be varied linearly with the laser fluence for each type of samples at the above two optical radiations. At 532 nm, PA signals from SRBCs and HRBCs were measured to be nearly equal, whereas, at 1064 nm, signal amplitude for SRBCs was approximately 2 times higher than that of HRBCs. The results suggest that it may be feasible to detect hemolysis with PAs.

  11. Modeling Decomposition of Unconfined Rigid Polyurethane Foam; TOPICAL

    International Nuclear Information System (INIS)

    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

  12. Solar energy storage and thermal use of an unconfined aquifer

    Science.gov (United States)

    Umemiya, H.; Haga, E.; Miyazawa, R.; Urushidani, M.

    1981-07-01

    An experiment using a large area, shallow aquifer for seasonal thermal storage is discussed. Two wells were drilled 70 m apart and water was pumped up from one well during the winter, and drained over a rooftop to melt snow before running back into another well-bore. During the summer, the well water is pumped up from the cool well, through a solar collector (the rooftop), and back into the warm well. A collection efficiency of 70% was determined for the summer cycle, and winter use from March-December revealed a water temperature of 8.5 C with a total injected volume of 14,700 cu m. The subsequent discovery that water returned to the ground quickly rose 4 C in temperature was taken as proof that the unconfined aquifer washed out the cooler water, implying that a one-well system is sufficient as a snow melter and collector fluid source in the winter.

  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. 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.

  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

    Scientific Electronic Library Online (English)

    Jefferson, Mateus; NestorFernando, Saavedra2; Zuly Calderón, Carrillo3; Darwin, Mateus4.

    2007-12-01

    Full Text Available 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 ca [...] rga 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. Abstract in english 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 loa [...] d 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.

  16. Consolidation, permeability, and strength of crushed salt/bentonite mixtures with application to the WIPP (Waste Isolation Pilot Plant)

    Energy Technology Data Exchange (ETDEWEB)

    Pfeifle, T.W. (RE/SPEC, Inc., Rapid City, SD (USA))

    1991-01-01

    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 {times} 10{sup {minus}17} and 5 {times} 10{sup {minus}17} m{sup 2}. 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.

  17. The influence of post-local buckling mechanics on the stress variations, axial stiffness and ultimate failure strength of uniformly compressed thin-walled i-section struts

    Energy Technology Data Exchange (ETDEWEB)

    Loughlan, J; Yidris, N; Cunningham, P R, E-mail: j.loughlan@lboro.ac.u [Department of Aeronautical and Automotive Engineering, Loughborough University, Loughborough, Leicestershire, LE11 3TU (United Kingdom)

    2009-08-01

    It is well known that thin-walled compression members are subject to the effects of local buckling and that due to these local effects the compressive carrying capability of short strut members can be significantly reduced. Finite element simulation is employed in this paper to examine the post-buckled response of thin-walled sections giving due consideration to the influence of geometric imperfections and to elasto-plastic material behaviour. The findings from this work highlight the complete loading history of the compression struts from the onset of elastic local buckling through the nonlinear elastic and elasto-plastic post-buckling phases of behaviour to final collapse and unloading. A detailed account of the growth and redistribution of stresses as well as the influence of yielding and yield propagation throughout loading is given in the paper. The results from the finite element simulations are shown to compare well with independent simulations using the finite strip method of analysis.

  18. 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.

  19. 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

  20. 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 wctions 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

  1. 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.

  2. Modelling of unconfined aquifer at Kalpakkam Plant site

    International Nuclear Information System (INIS)

    The rainwater is the main source of recharge to the shallow unconfined groundwater system at Kalpakkam plant site. Both single layer and double layer models were conceptualized by employing available geohydrological data in the study area. First considering the sandy formation as a single homogeneous unit layer, the model was constructed and calibrated in two stages viz., steady state flow and transient state flow conditions. During the model calibration, field values of hydraulic conductivity Kx=38.8 m|d, Ky=38.8 m|d, Kz=3.88 m|d for sandy formation and Kx=17.11 m|d, Ky=17.11 m|d, Kz=17.11 m|d for weathered rock, were employed. Similarly the values of (Ss) specific storage 0.0381, 0.000313 were assigned for sandy and weathered rock respectively. The April 2006 water table data were taken as the initial head condition. The constant head boundary was assigned along north, east and west direction. The single layer model was run and calibrated for steady state flow and further developed for transient condition by inputting the successive eight months water table data (May 2006 to December 2006). From the actual lithology of the study area, the model was then developed for double layer system of sand and weathered rock. Since, the water table fluctuations were observed the above two layers per some of the bore wells. The hydraulic conductivity and specific storage of the sandy formation were retac storage of the sandy formation were retained and the appropriate aquifer parameters for weathered zone were also suitably included. The results of single and double layer model were compared with respect to regression coefficients and it was observed that applicability of single or double layer modeling depended on the water column fluctuation at a given bore well location. (author)

  3. 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.

  4. Shock-wave compression and tension of solids at elevated temperatures: superheated crystal states, pre-melting, and anomalous growth of the yield strength

    International Nuclear Information System (INIS)

    Recent studies of the response of metals and alloys to shock-wave loading at elevated temperatures are summarized. Shock-wave tests have been carried out for metal single crystals, polycrystalline metals of different purity, and for alloys. High resistance to sub-microsecond tensile fracture of single crystals is maintained when melting should start. This is treated as evidence of a superheated solid state reached under dynamic tension. In polycrystalline metals, melting starts earlier at grain boundaries; this is known as the pre-melting phenomenon. As a result, their tensile strength drops to zero on approaching the melting curve. Anomalous growth of the dynamic yield stress was observed for low-strength metals, whereas the yield stress of high-strength alloys decreases with temperature. The different behaviour of metals and alloys is treated in terms of the relationship between the phonon drag of the motion of dislocations and the drag forces created by obstacles

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

    Directory of Open Access Journals (Sweden)

    S. M. Marandi

    2008-01-01

    Full Text Available 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 affected by the inclusion of palm fibers. A significant result was the determination that the sliding failure strength controlled the failure of the specimens rather than the rupture failure strength. Overall it was found that reinforced soil using palm fibers as the primary reinforcement are beneficial engineering materials and could potentially be used more often, though additional field use and testing should be carried out. Given the current concern over the environment and greenhouse gas emissions, strengthening soil through the use of natural materials (in this case palm fibers and the promotion of the cultivation of palm groves is one way that engineers and designers can contribute to a greener earth. Add to this the fact that the date palm is one of the most cultivated tree crops in the world with a worldwide distribution of around 100 million palms distributed in 30 countries including the Middle East, Asia, Africa, North America, Mediterranean countries and Australia in a bountiful resource that is available in many places where high technology engineering practices are either not available or too expensive. The use of the date palm for soil reinforcement means that in many areas of the world there is a readily available, effective local source of material for road foundation construction.

  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. Supplement to procedures, analysis, and comparison of groundwater velocity measurement methods for unconfined aquifers

    International Nuclear Information System (INIS)

    This report is a supplement to Procedures, Analysis, and Comparison of Groundwater Velocity Measurement Methods for Unconfined Aquifers and provides computer program descriptions, type curves, and calculations for the analysis of field data in determining groundwater velocity in unconfined aquifers. The computer programs analyze bail or slug tests, pumping tests, Geoflo Meter data, and borehole dilution data. Appendix A is a description of the code, instructions for using the code, an example data file, and the calculated results to allow checking the code after installation on the user's computer. Calculations, development of formulas, and correction factors for the various programs are presented in Appendices B through F. Appendix G provides a procedure for calculating transmissivity and specific yield for pumping tests performed in unconfined aquifers

  9. 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.

  10. 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.

  11. 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

    Directory of Open Access Journals (Sweden)

    C Vergara

    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.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.

  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. 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.

  14. Poro-viscoelastic constitutive modeling of unconfined creep of hydrogels using finite element analysis with integrated optimization method.

    Science.gov (United States)

    Liu, Kaifeng; Ovaert, Timothy C

    2011-04-01

    Hydrogels are cross-linked polymer networks swollen with water and are being considered as potential replacements for deceased load bearing tissues such as cartilage. Hydrogels show nonlinear time dependent behavior, and are a challenge to model. A three-element poro-viscoelastic constitutive model was developed based on the structure and nature of the hydrogel. To identify the material parameters, an inverse finite element (FE) technique was used that combines experimental results with FE modeling and an optimization method. Unconfined compression creep tests were conducted on poly(vinyl alcohol) (PVA) and poly(ethylene-co-vinyl alcohol)-poly(vinyl pyrrolidone) (EVAL-PVP) hydrogels manufactured by injection molding. Results from the creep experiments showed that for PVA hydrogels, an increase in polymer concentration correlates with a decrease in the equilibrium water content (EWC) and the creep strain. In EVAL-PVP hydrogels, an increase in the hydrophobic segments (EVAL) correlates with a decrease in the EWC as well as the creep strain. An inverse FE method was used to identify the viscoelastic material parameters of the hydrogels in combination with creep testing using the poro-viscoelastic three-element constitutive model. The elastic modulus estimated from the inverse FE technique showed good agreement with the modulus estimated directly from the test data. PMID:21316632

  15. 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.

  16. 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.

  17. Compression and compression fatigue testing of composite laminates

    Science.gov (United States)

    Porter, T. R.

    1982-01-01

    The effects of moisture and temperature on the fatigue and fracture response of composite laminates under compression loads were investigated. The structural laminates studied were an intermediate stiffness graphite-epoxy composite (a typical angle ply laimna liminate had a typical fan blade laminate). Full and half penetration slits and impact delaminations were the defects examined. Results are presented which show the effects of moisture on the fracture and fatigue strength at room temperature, 394 K (250 F), and 422 K (300 F). Static tests results show the effects of defect size and type on the compression-fracture strength under moisture and thermal environments. The cyclic tests results compare the fatigue lives and residual compression strength under compression only and under tension-compression fatigue loading.

  18. A test equipment to determine the tension-compression fatigue strength of metallic materials at elevated temperatures and under a simultaneous corrosive attack

    International Nuclear Information System (INIS)

    A test equipment will be described, which enables the performance of fatigue tests at elevated temperatures in a corrosive environment. The specimen is heated up by passing a current through it (electric resistance heating). This method of heating distinguishes itself by a precise temperature control and a low electrical energy consumption. Additionally the specimen can be exposed to a gaseous or vaporous environment. First experiments are carried out with stainless steel X 5 CrNi 18 9 (adequate to AISI 304) up to 6000C in air and in a corrosive medium. With increasing temperature the endurance strength decreases distinctly. Compared with this the effect of a simultaneous corrosive attack is because of the rather short duration of test relatively small. (orig.)

  19. Relação entre a resistência à compressão da argamassa com adição de sílica ativa aplicada ao substrato e àquela obtida em corpos-de-prova cilíndricos normatizados / Relationship between the compressive strength of silica fume mortar applied to the substratum and the one obtained in standardized cylindrical test specimens

    Scientific Electronic Library Online (English)

    N. R., Vaske; J. L., Campagnolo; D. C. C., Dal Molin.

    2010-09-01

    Full Text Available No uso de argamassa com adição de sílica ativa como material de reforço adotam-se valores de resistência à compressão provenientes de ensaios normatizados, que tendem a não representar a resistência à compressão da argamassa após lançada ao substrato. Na execução de um reforço, cada porção de argama [...] ssa que é lançada sofre um adensamento que varia em função da energia com que colide com o substrato, gerando, desta forma, pontos de diferentes resistências à compressão por toda a extensão do reforço, refletindo diretamente sobre a resistência do reforço como um todo, que por sua vez define a nova capacidade de carga do elemento estrutural que esta sendo reforçado. Procurando verificar o comportamento real da argamassa de reforço, executou-se uma placa de argamassa com adição de sílica ativa com dimensões iguais a um reforço de uma das faces de um pilar, sendo extraídas amostras prismáticas desta placa e ensaiadas à compressão. Deste ensaio foi de- terminada uma resistência à compressão média que, comparada com a resistência à compressão média obtida de corpos-de-prova cilíndricos, moldados com a mesma argamassa com que foi executada a placa, demonstrou que a resistência à compressão média das amostras prismáticas extraídas da placa apresenta, particularmente neste estudo, uma redução em relação à resistência à compressão média resultante dos corpos- de-prova cilíndricos da ordem de 35%. Abstract in english Compressive strength values obtained from standardized tests are adopted in the use of silica fume mortar as a reinforcement material, how- ever, they usually do not represent the compressive strength of mortar applied to the substratum. In a reinforcement procedure, each portion of mortar applied t [...] o the substratum undergoes densification according to the energy with which it collides with the substratum, resulting in different compressive strength values along the reinforcement; this affects the overall strength of the reinforcement as a whole, which, in turn, defines the new loading capacity of the reinforced structural element. In order to verify the actual behavior of a reinforcement mortar, a silica fume mortar plate dimensionally similar to a reinforced column face was executed, and prismatic samples extracted from the mortar plate were submitted to compression tests. The average compressive strength obtained was compared with the average compressive strength observed in cylindrical test specimens, molded from the same material used in the mortar plate. The prismatic samples' average compressive strength presented a reduction of 35% in this particular case.

  20. Compression stockings

    Science.gov (United States)

    Compression hose; Pressure stockings; Support stockings; Gradient stockings ... You wear compression stockings to improve blood flow in your legs. Compression stockings gently squeeze your legs to move blood up ...

  1. 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.

  2. Strength Training

    Science.gov (United States)

    ... strength training. Many people tend to lump all types of weightlifting together, but there's a big difference between strength training, powerlifting, and competitive bodybuilding! Strength training uses resistance methods like free weights, weight machines, resistance bands, or ...

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. Hydrological test in weak confined or unconfined area in No.511 deposit Xinjiang

    International Nuclear Information System (INIS)

    There is certain amount tones of uranium metal in prospecting line NO. 20?60 of NO. 511 deposit, which is in weak confined and unconfined aquifer and can't be mined by in-situ leaching. Hydrological test was made to uplift ground water level. The following aims are expected to be reached: (1) Transforming weak confined and unconfined state of ore-bearing aquifer to one with some confined water head; (2) Obtaining the effects of water injection on underground water by observation of water level and judgment of the ground water flow direction of pre-and pose-injection: (3) Verifying feasibility of in situ leaching by pumping test; (4) Calculating hydrogeological parameters by hydrological test in this area. There are benefit for push well layout, intensity of injection and amount of injection and pumping in leaching test. (authors)

  9. 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

  10. 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...

  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. 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.

  13. "Compressed" Compressed Sensing

    OpenAIRE

    Reeves, Galen; Gastpar, Michael

    2010-01-01

    The field of compressed sensing has shown that a sparse but otherwise arbitrary vector can be recovered exactly from a small number of randomly constructed linear projections (or samples). The question addressed in this paper is whether an even smaller number of samples is sufficient when there exists prior knowledge about the distribution of the unknown vector, or when only partial recovery is needed. An information-theoretic lower bound with connections to free probability...

  14. Compressed Air

    Science.gov (United States)

    This website includes an animation which demonstrates a basic overview of compressed air for use in machines. Objective: Describe the different tools that can be used with compressed air. You can find the animation under the heading "Automation Technology."

  15. INFLUENCIA DE LAS PROPIEDADES FÍSICAS DE LOS AGREGADOS EN LA TÉCNICA DE PULSO ULTRASÓNICO PARA PREDECIR LA RESISTENCIA A LA COMPRESIÓN DEL CONCRETO / THE INFLUENCE OF THE PHYSICAL PROPERTIES OF AGGREGATES ON THE ULTRASOUND PULSE TECHNIQUE IN PREDICTING THE COMPRESSIVE STRENGTH OF CONCRETE

    Scientific Electronic Library Online (English)

    Rómel, Solís Carcaño; Julio, Baeza Pereyra.

    2003-04-01

    Full Text Available RESUMEN La técnica de medición de la velocidad de pulso ultrasónico en el concreto ha sido usada por más de medio siglo para evaluar la calidad de este material. Entre otras aplicaciones, se ha utilizado para predecir la resistencia del concreto. En este trabajo se presentan los modelos de regresión [...] obtenidos de las mediciones de velocidad en especimenes cilíndricos de concreto y de los valores alcanzados con su posterior destrucción en pruebas uniaxiales a la compresión. El análisis de los resultados nos permite concluir que la técnica de medición de la velocidad de pulso ultrasónico en el concreto alcanza explicar alrededor de un 70% de la varianza en la resistencia de este material. Lo anterior para una muestra de concretos que fueron preparados con diferentes agregados de la misma región de México. Abstract in english ABSTRACT The ultrasound pulse technique has been used for more than 50 years, for measuring the quality of concrete elements. Among other applications, the technique has been used for predicting the compressive strength of concrete. This work presents regression models between the ultrasound pulse v [...] elocity, and the compressive strength of concrete cylinders, obtained from destructive testing. The results of this research point out that the sole use of the ultrasound technique can predict around 70% of the variability of the compressive strength in the case where the aggregates come from the same region of Mexico.

  16. 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.

  17. Investigating the Effect of Concrete Strength on the Behaviour of Composite Steel-concrete Beams

    OpenAIRE

    Suhaib Yahya Kasim Al-Darzi; Ameer, Usama A.

    2012-01-01

    The present study investigates the effects of increasing the compressive strength of concrete deck on the deflection at midspan and slip at ends of steel-concrete composite beam. In the present study, four groups of steel concrete composite beam were tested to investigate the effects of variation of concrete compressive strength on the deflection, slip, yield strength and ultimate strength of composite beam, using concrete cylinder compressive strength of 21, 42 and 64 MPa. The study al...

  18. Strength Modeling of High-Strength Concrete with Hybrid Fibre Reinforcement

    Directory of Open Access Journals (Sweden)

    A. Ravichandran

    2009-01-01

    Full Text Available The low tensile strength and limited ductility, the unavoidable deficiency, of concrete can be overcome by the addition of fibres. High strength concrete (HSC of 60 MPa containing hybrid fibres, combination of steel and polyolefin fibres, at different volume fraction of 0.5, 1.0, 1.5 and 2.0% were compared in terms of compressive, splitting tensile strength and flexural properties with HSC containing no fibres. Test results showed that the fibres when used in hybrid form could result in enhanced flexural toughness compared to steel fibre reinforced concrete [HSFRC]. The compressive strength of the fibre-reinforced concrete reached maximum at 1.5% volume fractions and the splitting tensile strength and modulus of rupture improved with increasing volume fraction. Strength models were established to predict the compressive and splitting tensile strength and modulus of rupture of the fibre-reinforced concrete. The models give prediction matching the measurements.

  19. 3-D transient hydraulic tomography in unconfined aquifers with fast drainage response

    Science.gov (United States)

    Cardiff, M.; Barrash, W.

    2011-12-01

    We investigate, through numerical experiments, the viability of three-dimensional transient hydraulic tomography (3DTHT) for identifying the spatial distribution of groundwater flow parameters (primarily, hydraulic conductivity K) in permeable, unconfined aquifers. To invert the large amount of transient data collected from 3DTHT surveys, we utilize an iterative geostatistical inversion strategy in which outer iterations progressively increase the number of data points fitted and inner iterations solve the quasi-linear geostatistical formulas of Kitanidis. In order to base our numerical experiments around realistic scenarios, we utilize pumping rates, geometries, and test lengths similar to those attainable during 3DTHT field campaigns performed at the Boise Hydrogeophysical Research Site (BHRS). We also utilize hydrologic parameters that are similar to those observed at the BHRS and in other unconsolidated, unconfined fluvial aquifers. In addition to estimating K, we test the ability of 3DTHT to estimate both average storage values (specific storage Ss and specific yield Sy) as well as spatial variability in storage coefficients. The effects of model conceptualization errors during unconfined 3DTHT are investigated including: (1) assuming constant storage coefficients during inversion and (2) assuming stationary geostatistical parameter variability. Overall, our findings indicate that estimation of K is slightly degraded if storage parameters must be jointly estimated, but that this effect is quite small compared with the degradation of estimates due to violation of "structural" geostatistical assumptions. Practically, we find for our scenarios that assuming constant storage values during inversion does not appear to have a significant effect on K estimates or uncertainty bounds.

  20. 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.

  1. Modeling of hydrological drawdown caused by pumping for unconfined, confined, and half-confined aquifers

    Science.gov (United States)

    Pratama, Angga Bakti; Srigutomo, Wahyu

    2015-04-01

    Simple modeling of hhydrological drawdown for three types of aquifer was conducted. We present the results of the application of the iterative least-squares non-linear Levenberg-Marquardt inversion for the case of unconfined, confined and half-confined aquifer geometries that are usually encountered in the field. The input parameters are the piezometric head, pumping rate, and the initial value of drawdown. Homogeneous assumption of the aquifer thickness and depth are applied. The head drawdown, transmitivity, storativity, and pumping rate are the measured data or responses, whereas the conductivity and acquifer thickness are the sought model parameters.

  2. An experimental approach to strain pattern and folding in unconfined and/or partitioned transpressional deformation

    Science.gov (United States)

    Ghosh, N.; Chakra, M.; Chattopadhyay, A.

    2014-01-01

    Three different series of experiments were carried out with pitch (bitumen) and/or composite pitch-plasticine models to observe the spatial and temporal changes of strain pattern and/or fold styles in a tectonic zone undergoing sinistral-sense unconfined transpression. In the first series, rectangular pitch models with circular strain markers, when subjected to vertically and laterally unconstrained transpression, showed that the circular markers deformed into ellipses with long axes (maximum instantaneous stretching axis: ISAmax) oriented plasticine layer placed over the pitch block initiated parallel to the long axis of the finite strain ellipse in transpression and rotated anticlockwise with increasing strain.

  3. Impact Strength of Glass and Glass Ceramic

    Science.gov (United States)

    Bless, S.; Tolman, J.

    2009-12-01

    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.

  4. 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.

  5. Factors Influencing Groundwater Monitoring Strategies in a System With an Unconfined Aquifer Overlying a Fractured Bedrock Aquifer

    Science.gov (United States)

    Chen, Y.; Smith, L.; Beckie, R.

    2003-12-01

    Factors influencing groundwater monitoring strategies are examined for the case where an unconfined aquifer overlies a fractured bedrock aquifer. A contaminant source is located at the ground surface. Flow and transport in the bedrock aquifer is represented as a three-dimensional discrete fracture network within a permeable rock matrix. Using this scenario, we examine how various factors interact to determine plume geometry, and contaminant detection thresholds in the unconfined and bedrock aquifers as a function of well location within the subsurface. Factors considered include the hydrologic properties of the unconfined aquifer (hydraulic conductivity, porosity), the geometric properties of the fractured network (density, length, aperture), and matrix permeability. These simulation results provide guidelines for the design and evaluation of a subsurface monitoring network.

  6. Reflections about the modelling of unconfined explosions of air-hydrocarbon mixtures

    International Nuclear Information System (INIS)

    To design nuclear power plants structures, an evaluation of hazards which can be induced by the industrial activities is needed. These hazards namely involve explosions of flamable air-hydrocarbon gas clouds. Such clouds can drift before ignition, and, when ignited, the generated pressure wave can cause serious damage, even far from the initial accident location. When the designs an industrial plant, the designer has to predict the overpressures capable of jeopardizing the safety functions of the plant. The analysis of real accidental explosions which have actually occurred, on the basis of a total explosion yield and the TNT equivalency concept, is a first step. Indeed, it allows a total explosion yield to be calculated, an empirical TNT equivalent of hydrocarbon to be deducted. Unfortunately, this TNT equivalency concept is scientifically not satisfying. The modelling of an unconfined air-hydrocarbon detonation can be used for safety analysis, if we assume that an unconfined explosion can be a detonation, which is unlikely. (orig./WL)

  7. 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.

  8. 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.

  9. STUDY ON LONG-TERM STRENGTH OF BRITTLE SOLIDS

    Directory of Open Access Journals (Sweden)

    Dunaev V. I.

    2014-02-01

    Full Text Available Considered theory of termofluktuacion strength of solids. Formulas for predicting long-term strength limits. Set the value of a safe low voltage of compression depends on the physical and mechanical material constants. For a number of technical glass received the numerical estimation of compressive stresses safety.

  10. 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.

  11. Effect of insulating concrete forms in concrete compresive strength

    Science.gov (United States)

    Martinez Jerez, Silvio R.

    The subject presented in this thesis is the effect of Insulating Concrete Forms (ICF's) on concrete compressive strength. This work seeks to identify if concrete cured in ICF's has an effect in compressive strength due to the thermal insulation provided by the forms. Modern construction is moving to energy efficient buildings and ICF's is becoming more popular in new developments. The thesis used a concrete mixture and a mortar mixture to investigate the effects of ICF's on concrete compressive strength. After the experimentations were performed, it was concluded that the ICF's do affect concrete strength. It was found that the forms increase concrete strength without the need for additional curing water. An increase of 50% in strength at 56 days was obtained. It was concluded that the longer concrete cures inside ICF's, the higher strength it reaches, and that ICF's effect on concrete strength is proportional to volume of concrete.

  12. A new package in MODFLOW to simulate unconfined groundwater flow in sloping aquifers.

    Science.gov (United States)

    Wang, Quanrong; Zhan, Hongbin; Tang, Zhonghua

    2014-01-01

    The nonhorizontal-model-layer (NHML) grid system is more accurate than the horizontal-model-layer grid system to describe groundwater flow in an unconfined sloping aquifer on the basis of MODFLOW-2000. However, the finite-difference scheme of NHML was based on the Dupuit-Forchheimer assumption that the streamlines were horizontal, which was acceptable for slope less than 0.10. In this study, we presented a new finite-difference scheme of NHML based on the Boussinesq assumption and developed a new package SLOPE which was incorporated into MODFLOW-2000 to become the MODFLOW-SP model. The accuracy of MODFLOW-SP was tested against solution of Mac Cormack (1969). The differences between the solutions of MODFLOW-2000 and MODFLOW-SP were nearly negligible when the slope was less than 0.27, and they were noticeable during the transient flow stage and vanished in steady state when the slope increased above 0.27. We established a model considering the vertical flow using COMSOL Multiphysics to test the robustness of constrains used in MODFLOW-SP. The results showed that streamlines quickly became parallel with the aquifer base except in the narrow regions near the boundaries when the initial flow was not parallel to the aquifer base. MODFLOW-SP can be used to predict the hydraulic head of an unconfined aquifer along the profile perpendicular to the aquifer base when the slope was smaller than 0.50. The errors associated with constrains used in MODFLOW-SP were small but noticeable when the slope increased to 0.75, and became significant for the slope of 1.0. PMID:24299562

  13. Atmospheric noble gases as tracers of biogenic gas dynamics in a shallow unconfined aquifer

    Science.gov (United States)

    Jones, Katherine L.; Lindsay, Matthew B. J.; Kipfer, Rolf; Mayer, K. Ulrich

    2014-03-01

    Atmospheric noble gases (NGs) were used to investigate biogenic gas dynamics in a shallow unconfined aquifer impacted by a crude oil spill, near Bemidji, MN. Concentrations of 3,4He, 20,22Ne, 36,40Ar, Kr, and Xe were determined for gas- and aqueous-phase samples collected from the vadose and saturated zones, respectively. Systematic elemental fractionation of Ne, Ar, Kr, and Xe with respect to air was observed in both of these hydrogeologic zones. Within the vadose zone, relative ratios of Ne and Ar to Kr and Xe revealed distinct process-related trends when compared to corresponding ratios for air. The degree of NG deviation from atmospheric concentrations generally increased with greater atomic mass (i.e., ?Xe > ?Kr > ?Ar > ?Ne), indicating that Kr and Xe are the most sensitive NG tracers in the vadose zone. Reactive transport modeling of the gas data confirms that elemental fractionation can be explained by mass-dependent variations in diffusive fluxes of NGs opposite to a total pressure gradient established between different biogeochemical process zones. Depletion of atmospheric NGs was also observed within a methanogenic zone of petroleum hydrocarbon degradation located below the water table. Solubility normalized NG abundances followed the order Xe > Kr > Ar > Ne, which is indicative of dissolved NG partitioning into the gas phase in response to bubble formation and possibly ebullition. Observed elemental NG ratios of Ne/Kr, Ne/Xe, Ar/Xe, and Kr/Xe and a modeling analysis provide strong evidence that CH4 generation below the water table caused gas exsolution and possibly ebullition and carbon transfer from groundwater to the vadose zone. These results suggest that noble gases provide sensitive tracers in biologically active unconfined aquifers and can assist in identifying carbon cycling and transfer within the vadose zone, the capillary fringe, and below the water table.

  14. Characterization of Strength of Intact Brittle Rock Considering Confinement-Dependent Failure Processes

    Science.gov (United States)

    Kaiser, Peter K.; Kim, Bo-Hyun

    2015-01-01

    As technologies for deep underground development such as tunneling underneath mountains or mass mining at great depths (>1,000 m) are implemented, more difficult ground conditions in highly stressed environments are encountered. Moreover, the anticipated stress level at these depths easily exceeds the loading capacity of laboratory testing, so it is difficult to properly characterize what the rock behavior would be under high confinement stress conditions. If rock is expected to fail in a brittle manner, behavior changes associated with the relatively low tensile strength, such as transition from splitting to the shear failure, have to be considered and reflected in the adopted failure criteria. Rock failure in tension takes place at low confinement around excavations due to tensile or extensional failure in heterogeneous rocks. The prospect of tensile-dominant brittle failure diminishes as the confinement increases away from the excavation boundary. Therefore, it must be expected that the transition in the failure mechanism, from tensile to shear, occurs as the confinement level increases and conditions for extensional failure are prevented or strongly diminished. However, conventional failure criteria implicitly consider only the shear failure mechanism (i.e., failure envelopes touching Mohr stress circles), and thus, do not explicitly capture the transition of failure modes from tensile to shear associated with confinement change. This paper examines the methodologies for intact rock strength determination as the basic input data for engineering design of deep excavations. It is demonstrated that published laboratory test data can be reinterpreted and better characterized using an s-shaped failure criterion highlighting the transition of failure modes in brittle failing rock. As a consequence of the bi-modal nature of the failure envelope, intact rock strength data are often misinterpreted. If the intact rock strength is estimated by standard procedures from unconfined compression tests (UCS) alone, the confined strength may be underestimated by as much as 50 % (on average). If triaxial data with a limited confinement range (e.g., ?3 ? 0.5 UCS due to cell pressure limitations) are used, the confined strength may be overestimated. Therefore, the application of standard data fitting procedures, without consideration of confinement-dependent failure mechanisms, may lead to erroneous intact rock strength parameters when applied to brittle rocks, and consequently, by extrapolation, to correspondingly erroneous rock mass strength parameters. It follows that the strength characteristics of massive rock differ significantly in the direct vicinity of excavation from that which is remote with higher confinement. Therefore, it is recommended to adopt a differentiated approach to obtain intact rock strength parameters for engineering problems at lower confinement (near excavation; e.g., excavation stability assessment or support design), and at elevated confinement (typically, when the confinement exceeds about 10 % of the UCS) as might be encountered in wide pillar cores.

  15. Spaghetti Strength

    Science.gov (United States)

    American Chemical Society

    2011-01-01

    In this activity on page 7 of the PDF, learners explore how engineers characterize building materials. Learners test the strength of spaghetti and determine how the number of spaghetti strands affects the strength of a bundle of spaghetti. Use this activity to chemical bonds, mechanical testing, and engineering. Note: The pasta strands can be dipped in water and stuck together to more closely mimic the layers within a piece of plywood. More information about this can be found at the top of page 7, directly underneath the cartoon image. Safety note: Do not eat or drink any of the materials in this activity.

  16. Evaluation of trabecular bone strength using ultrasound

    International Nuclear Information System (INIS)

    The prediction of bone strength by ultrasound velocity (UV) and broadband ultrasound attenuation (BUA) was examined. Ultrasound velocity and broadband attenuation were measured for sixty specimens of human trabecular bone. Samples were divided into two equal groups and loaded in compression at the strain rates of 0.0004 sec-1 and of 0.08 sec-1 . The ultimate strength was determined for each specimen. Specimens tested at 0.08 sec-1 had a mean value of strength 63% higher than the specimens tested at 0.0004 sec-1. UV and BUA were significantly associated with compressive strength at both strain rates. Mechanical strength was also correlated strongly with a linear combination of UV and BUA for both the low and high loading rates. The use of ultrasound parameters may provide good clinical means for assessing the resistance of trabecular bone to both low and high energy trauma.

  17. 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

    Directory of Open Access Journals (Sweden)

    Israel Luiz de Lima

    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 da 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.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.

  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. 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.

  20. 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.

  1. Effective pressure interface law for transport phenomena between an unconfined fluid and a porous medium using homogenization

    OpenAIRE

    Marciniak-Czochra, A.; Mikelic, A.

    2011-01-01

    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...

  2. GEOCHEMICAL ASSESSMENT OF THE UNCONFINED AQUIFER IN A RECENTLY RECLAIMED WETLAND AREA: A CASE STUDY FROM THE PO RIVER DELTA

    OpenAIRE

    Dario Di Giuseppe; Barbara Faccini; Micòl Mastrocicco; Nicolò Colombani; Massimo Coltorti; Giacomo Ferretti

    2013-01-01

    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 ...

  3. 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...

  4. Three-dimensional semi-analytical solution to groundwater flow in confined and unconfined wedge-shaped aquifers

    Science.gov (United States)

    Sedghi, Mohammad Mahdi; Samani, Nozar; Sleep, Brent

    2009-06-01

    The Laplace domain solutions have been obtained for three-dimensional groundwater flow to a well in confined and unconfined wedge-shaped aquifers. The solutions take into account partial penetration effects, instantaneous drainage or delayed yield, vertical anisotropy and the water table boundary condition. As a basis, the Laplace domain solutions for drawdown created by a point source in uniform, anisotropic confined and unconfined wedge-shaped aquifers are first derived. Then, by the principle of superposition the point source solutions are extended to the cases of partially and fully penetrating wells. Unlike the previous solution for the confined aquifer that contains improper integrals arising from the Hankel transform [Yeh HD, Chang YC. New analytical solutions for groundwater flow in wedge-shaped aquifers with various topographic boundary conditions. Adv Water Resour 2006;26:471-80], numerical evaluation of our solution is relatively easy using well known numerical Laplace inversion methods. The effects of wedge angle, pumping well location and observation point location on drawdown and the effects of partial penetration, screen location and delay index on the wedge boundary hydraulic gradient in unconfined aquifers have also been investigated. The results are presented in the form of dimensionless drawdown-time and boundary gradient-time type curves. The curves are useful for parameter identification, calculation of stream depletion rates and the assessment of water budgets in river basins.

  5. Impact of internal water reservoirs on the compressive strenght of high strenght concrete

    OpenAIRE

    Legat, Nejc

    2012-01-01

    The present work examines the impact of internal curing on the compressive strength of high strength concrete. High strength concrete is used in more complex structures as it have very good mechanical properties. However, due to low water-binder ratio is more susceptible to shrinkage. Shrinkage of high strength concrete can limited or eliminated with internal curing – internal water reservoirs, but this may affect on the reduction of the compressive strength. In experimantal studies we w...

  6. 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)

  7. 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 ofation: thus warranting a full treatment of the thermodynamics of the mixture. (Author)

  8. Unconfined, melt edge electrospinning from multiple, spontaneous, self-organized polymer jets

    Science.gov (United States)

    Wang, Qingqing; Curtis, Colin K.; Muthuraman Thoppey, Nagarajan; Bochinski, Jason R.; Gorga, Russell E.; Clarke, Laura I.

    2014-12-01

    Commercial grade polyethylene is melt electrospun from a thin film of unconfined molten polymer on a heated, electrically-grounded plate. Under the influence of an applied electric field, the melt spontaneously forms fingering perturbations at the plate edge which then evolve into emitting fiber-forming jets. Jet-to-jet spacing (˜5 mm), which is dependent on the applied voltage amplitude, is in agreement with estimates from a simple theoretical treatment. The broad applicability of the approach is verified by spinning a second polymer—polycaprolactone. In both cases, the fabricated fibers are similar in quality to those obtained under needle melt electrospinning; however for this method, there are no nozzles to clog and an enhanced production rate up to 80 mg min?1 is achieved from approximately 20–25 simultaneous parallel jets. The process of jet formation, effective flow rates, cone-jet diameters, as well as limits on jet density and differences with polymer type are compared with theoretical models. This particular approach allows facile, high throughput micro- and nano-fiber formation from a wide variety of thermoplastics and other high viscosity fluids without the use of solvents or the persistent issues of clogging and pumping that hamper traditional methods, resulting in mechanically strong meso-scale fibers highly desirable for industrial applications.

  9. 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.

  10. High strength cementized dried resins

    International Nuclear Information System (INIS)

    One common method for disposal of radioactive resins is to mix them with cement and cast them into monolithic blocks in rigid liners (containers). In some cases, cementized resin samples have reabsorbed water and swelled until the cement crumbled. Therefore, the NRC Branch Technical Position on waste forms requires cementized bead resin to undergo a 0.34 MPa (50 psi) compressive strength test after immersion in water for 90 days in order to qualify as an acceptable radioactive waste disposal form. Many cementized resin waste forms cannot achieve high radioactive waste loading and still qualify as a waste form after the 90-day immersion strength test. It was found that chemically spent resins pretreated in a high efficiency dryer are nearly impermeable to water and will not reabsorb and swell when immersed. The chemical form of the resins was found to be an important factor in water reabsorption. Fresh resins in the H/sup +/ or OH/sup -/ form were susceptible to water reabsorption after high-efficiency drying. However, depleted resins were found to be well-suited for cement solidification and high-strength waste forms were produced with loadings as high as nearly 28 wt.% dried resins (equivalent to 70 wt.% dewatered resins). These waste forms easily withstood the compressive strength test after initial curing and after 90 days of immersion in water

  11. Comparação de espessura de película e da resistência à compressão dos cimentos vedantes de ionômero de vidro convencional versus reforçado com resina / Comparative evaluation of film thickness and compressive strength of glass ionomer luting cements, conventional versus resin modified glass ionomer

    Scientific Electronic Library Online (English)

    Gustavo Tedesco de, Carvalho; Tsuneharu, Ogasawara.

    2006-09-01

    Full Text Available O objetivo deste trabalho foi avaliar, em cimentos utilizados exclusivamente para cimentação de trabalhos protéticos indiretos, as reais melhorias mecânicas dos ionômeros modificados com resina em relação aos ionômeros convencionais. Desenvolvimentos termodinâmicos foram realizados para melhor compr [...] eender os vidros componentes dos cimentos estudados, bem como melhor interpretar resultados experimentais. O trabalho experimental realizado com três cimentos ( Ketac Cem - ESPE, Fuji Plus - GC e Vitremer - 3M) caracterizados como cimentantes, isto é, utilizados na cimentação de trabalhos odontológicos indiretos, consistiu em: caracterização do pó original dos cimentos através de microscopia eletrônica de varredura; determinação da espessura de película de cimentação; análise por microscopia ótica de seções de corte de amostras de cimento curado; e ensaios de resistência à compressão em amostras de cimento curado. Foram obtidos os resultados de análises estatísticas dos dados coletados sobre espessura de película de cimento vedante e da resistência à compressão do mesmo. Concluiu-se que a espessura de película do cimento Vitremer é significativamente menor do que aquela do cimento Ketac Cem, que por sua vez é significativamente menor do que a do cimentoFuji Plus; a resistência à compressão do cimento Fuji plus é significativamente maior do que aquela do cimento Vitremer, que é por sua vez significativamente maior do que aquela do cimento Ketac Cem. Abstract in english The objective of this work was to evaluate, in cements exclusively used for luting indirect prosthetic works, the effective mechanical improvements of resin modified glass-ionomer compared to those of conventional glass-ionomers. Thermodynamic developments were carried out in order to better underst [...] and the glass components making part the glass ionomer cements. The experimental work performed with 3 luting cements (Ketac Cem - ESPE, Fuji Plus - GC and Vitremer - 3M) consisted of characterization of the original cement powders by SEM; determination of the thickness of the luting cement; optical microscopy analysis of the cross sections from cured cement samples; and compression strength tests on cured cement samples. Results of the statistical analyses from data collected on luting cement thickness and on compressive strength of the cements were obtained. The following conclusions were achieved: Vitremer cement thickness is significantly smaller than that of Ketac Cem cement, which in turn is significantly smaller than that of Fuji Plus; the compressive strength of the Fuji Plus cement is significantly higher than that of Vitremer cement, which in turn is significantly higher than that of Ketac Cem cement.

  12. Strength measurement of impulse compacted moulding sand

    Directory of Open Access Journals (Sweden)

    T. Mikulczy?ski

    2011-01-01

    Full Text Available Analysis of impulse compaction process shows that during compaction process moulding sand is subject to deformation and changes oftotal pressure, measured inside compacted moulding sand, represent fading sinusoid. Measured pressure values in stationary states (aftercompaction process are equal to the sum of squeezing pressure pc and the pressure resulting from compacting the sandmix pu, whichexpresses the obtained strength. Therefore experimental research of moulding sands were conducted. Strength factor Rc and pressure puvalues were determined as a function of densening degree ?. Analysis of presented results proves that pu pressure resulting fromcompacting of the moulding sand expresses compressive strength factor Rc. This confirms that developed methodology permits strengthmeasurements of moulding sand in the mould. Moreover as it is possible to determine pu values with simulation research of developedmathematical model of impulse process it is possible to determine compressive strength factor.

  13. Estimation of compressive strength based on Pull-Out bond test results for on-site concrete quality control / Estimativa da resistência à compressão a partir de resultados de ensaios de aderência tipo Pull-Out para controle da qualidade do concreto na obra

    Scientific Electronic Library Online (English)

    M. S., Lorrain; M. P., Barbosa; L. C. P., Silva Fº.

    2011-10-01

    Full Text Available O controle de qualidade do concreto estrutural vem sendo realizado, há várias décadas, baseado principalmente nos resultados de ensaios de compressão axial. Este tipo de ensaio, embora amplamente utilizado, não está isento de erros e tem algumas desvantagens consideráveis que podem afetar sua confia [...] bilidade, tais como a necessidade de condicionamento adequado e cuidadoso dos corpos-de-prova e de adoção de adequadas técnicas de nivelamento e capeamento. Por estas razões, seria útil ter maneiras complementares ou alternativas para verificar a resistência à compressão, a fim de melhorar o processo de controle de qualidade do concreto. O uso de um ensaio de arrancamento para monitorar a resistência do concreto está sendo proposto por um consósrcio internacional de pesquisadores da França, Tunísia e Brasil como um meio potencial de atingir essa meta. Dado que a existência de uma relação direta entre a tensão de aderência e a resistência do concreto já está bem estabelecida, este tipo de teste parece ser uma alternativa viável aos métodos tradicionais. No entanto, para verificar se o princípio subjacente é valido quando usado em diferentes circunstâncias, o grupo tem buscado recolher dados de vários estudos, realizados por diferentes pesquisadores, em diversos países, com concretos e barras de armadura de distintos tipos. Uma análise dos dados coletados confirma que há uma correlação clara e um forte vínculo entre a tensão de aderência e a resistência à compressão, independentemente da influência de outras variáveis. Esses resultados validam a idéia básica de usar um teste de Pull Out adequado (denominado APULOT) para avaliar a resistência do concreto. Se o princípio geral é válido para dados aleatórios obtidos em diferentes estudos, a definição de um procedimento de teste claro e adequado provavelmente levará à redução erros experimentais e aumentará a estimativa da precisão obtidas por esse método. Abstract in english Quality control of structural concrete has been conducted for several decades based mainly on the results of axial compression tests. This kind of test, although widely used, is not exempt from errors and has some considerable drawbacks that may affect its reliability, such as the need for appropria [...] te and careful specimen conditioning and adoption of adequate capping techniques. For these reasons, it would be useful to have complementary or alternative ways to check compressive strength, in order to improve concrete quality control. The use of a bond test to monitor concrete strength is being proposed by an international group of researchers from France, Tunisia and Brazil as a potential means to this end. Given the fact that the link between bond resistance and concrete strength is already well established, this type of test seems to be a viable alternative to traditional methods. Nonetheless, to check if the underlying principle is sound when used in different circumstances, the group has been gathering data from several studies conducted by different researchers in various countries, with distinct concretes and rebar types. An analysis of the data collected shows that there is a clear and strong correlation between bond resistance and compressive strength, no matter the influence of other variables. This result validates the basic idea of using an Appropriate Pull-Out (APULOT) bond test to assess concrete strength. If the general principle is valid for random data obtained from different studies, the definition of a clear and appropriate test will probably lead to the reduction of experimental noise and increase the precision of the strength estimates obtained using this method.

  14. Strength and water penetrability of fly ash geopolymer concrete

    OpenAIRE

    Monita Olivia; Nikraz, Hamid R.

    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...

  15. Prediction of strength of wood composite materials using ultrasonic

    International Nuclear Information System (INIS)

    Wood is a biological material integrating a very large variability of its mechanical properties (tensile and compressive), on the two directional longitudinal and transverse Ultrasonic method has been utilized to measure both wood physical and / or wood mechanical properties. The aim of this article is to show the development of ultrasonic technique for quality evaluation of trees, wood material and wood based composites. For quality assessment of these products we discuss the nondestructive evaluation of different factors such as: moisture content, temperature, biological degradation induced by bacterial attack and fungal attack. These techniques were adapted for trees, timber and wood based composites. The present study discusses the prediction of tensile and compressive strength of wood composite materials using ultrasonic testing. Empirical relationships between the tensile properties, compression strength and ultrasonic were proposed. The experimental results indicate the possibility of establishing a relationship between tensile strength and compression values. Moreover, the fractures in tensile and compressive are discussed by photographic

  16. 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.

  17. Use of gravity and drawdown information to estimate hydraulic properties during unconfined aquifer testing

    Science.gov (United States)

    Blainey, J. B.; Ferre, T. P.

    2007-12-01

    High-resolution gravimetry measured at the ground surface may offer a cost-effective method to augment aquifer tests in unconfined aquifers without the expense of installing additional monitoring wells or piezometers. However, evaluating the usefulness of gravity, used either alone or together with piezometric measurements, to help constrain hydraulic parameters through aquifer testing is difficult because observations of drawdown in a monitoring well and gravity measurements respond to different physical states of the system at different spatial scales. Measurements of drawdown provide a direct measure of the energy potential local to the observation location, while measurements of gravity change indirectly measure changes in water storage and depend on the spatially-weighted average of the subsurface density change integrated over a large measurement volume. Hydrogeophysical numerical experiments are conducted to examine the value of drawdown and gravity responses for constraining aquifer test analyses based on synthetic measurements at nine ground-surface locations after seven days of pumping. We confirm that the conditions conducive to this use of gravity measurements are those that lead to a sufficiently large change in gravity signal: high drainable porosity of the aquifer, low depth to the water table, and small distance from the pumping well to a gravity measurement location. However, we further demonstrate that the ability of a gravimeter to detect a signal above the noise in the data is not a sufficient condition to guarantee utility of the measurement method to constrain hydraulic parameter estimation. Specifically, the inference of hydraulic properties requires consideration of parameter interaction and parameter sensitivity to instrument responses in addition to instrument resolution and signal detectability. For conditions amenable to gravity monitoring, combined use of drawdown and gravity data resulted in unbiased and precise estimates of both hydraulic conductivity and specific yield. This offers improvement over monitoring drawdown alone, which often provides poor estimates of specific yield.

  18. Numerical predictions of flows past two tandem cylinders of different diameters under unconfined and confined flows

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Renjie; Lin, Jianzhong [Department of Mechanics, Zhejiang University, Hangzhou 310027 (China); Ku, Xiaoke, E-mail: mecjzlin@public.zju.edu.cn [Faculty of Science and Technology, University of Twente, 7500-AE Enschede (Netherlands)

    2014-04-01

    Flows past two tandem cylinders of different diameters placed in a free-stream velocity and between two parallel walls are numerically studied via a lattice Boltzmann method. In both the big–small arrangement (BSA) and the small–big arrangement (SBA), the diameter of the big cylinder is adopted as the characteristic length and the diameter ratios of two cylinders are 0.5, 0.625, 0.75 and 0.875, respectively. The effects of the Reynolds number, diameter ratio, arrangement pattern, cylinder spacing and plane boundaries on the flows are systematically investigated. In the binary-vortex regime, the results show that for both the unconfined and confined cases, vortices are shed from both cylinders in a coupled frequency which is mainly dependent on the front cylinder in contrast with the case of an isolated cylinder. The vortex structures in BSA are more regular than those observed in SBA and the plane boundaries have a modulation effect on the flow. In SBA, the flow structure becomes more irregular as the diameter ratio is decreased and as the Reynolds number is increased and the mechanism of such a phenomenon is also discussed. In both BSA and SBA, when the cylinder spacing is increased to a threshold, the wake structure translates from the reattachment regime to the co-shedding regime and the critical spacing in BSA is smaller than that in SBA. As the cylinders are placed in proximity to each other, the negative and positive drag coefficients of the downstream cylinder are observed in BSA and SBA, respectively. The positive drag coefficient in SBA decreases as the diameter ratio is increased. (paper)

  19. Numerical predictions of flows past two tandem cylinders of different diameters under unconfined and confined flows

    International Nuclear Information System (INIS)

    Flows past two tandem cylinders of different diameters placed in a free-stream velocity and between two parallel walls are numerically studied via a lattice Boltzmann method. In both the big–small arrangement (BSA) and the small–big arrangement (SBA), the diameter of the big cylinder is adopted as the characteristic length and the diameter ratios of two cylinders are 0.5, 0.625, 0.75 and 0.875, respectively. The effects of the Reynolds number, diameter ratio, arrangement pattern, cylinder spacing and plane boundaries on the flows are systematically investigated. In the binary-vortex regime, the results show that for both the unconfined and confined cases, vortices are shed from both cylinders in a coupled frequency which is mainly dependent on the front cylinder in contrast with the case of an isolated cylinder. The vortex structures in BSA are more regular than those observed in SBA and the plane boundaries have a modulation effect on the flow. In SBA, the flow structure becomes more irregular as the diameter ratio is decreased and as the Reynolds number is increased and the mechanism of such a phenomenon is also discussed. In both BSA and SBA, when the cylinder spacing is increased to a threshold, the wake structure translates from the reattachment regime to the co-shedding regime and the critical spacing in BSA is smaller than that in SBA. As the cylinders are placed in proximity to each other, the negative and positive drag coefficients of the downstream cylinder are observed in BSA and SBA, respectively. The positive drag coefficient in SBA decreases as the diameter ratio is increased. (paper)

  20. 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.

  1. A comprehensive study of the lift generation in soft porous media under rapid compression

    Science.gov (United States)

    Wu, Qianhong; Nathan, Rungun; Crawford, Robert; Vu Cbmss Team

    2013-11-01

    Lift generation in soft porous media under rapid compaction is a new concept for porous media flow, which has broad applications in biological systems, squeeze damping, and soft lubrication, etc. Previous studies on this topic share a common feature of neglecting the lift contribution of the undeformed porous structures surrounding the compressed porous media, thus deviated from real applications. Herein we report a comprehensive experimental and theoretical approach to treat this shortcoming. A soft, polyester, fibrous, porous material with specified micro-structure, porosity and permeability was dynamically compressed by a loaded piston in a porous-walled cylinder-piston apparatus. Pore air was forced out radially either directly to the ambient (``unconfined'' case) or to the surrounding undeformed porous media (``confined'' case). Detailed pressure measurements indicate that the air lifting force underneath the piston was enhanced by 25% to 30% for the ``confined'' case as compared to the ``unconfined'' case. A consolidation theory was developed to characterize this process, which shows very good agreements with the experimental data. This study significantly improves our understanding of the dynamic response of soft porous media under rapid compression.

  2. Strength Properties of Concrete Containing Waste Glass Powder

    Directory of Open Access Journals (Sweden)

    Mohd Vasique Hussain

    2015-04-01

    Full Text Available The aim of this paper is to study the behavior of M-30 grade of concrete to determine the compressive strength and split tensile strength by partially replacement of cement by waste glass powder. Cement was partially replaced by waste glass powder in 10%, 20% and 30% by weight. All the tests were performed according to Bureau of Indian standards. The results thus obtained were compared and examined with respect to the control specimen. The addition of waste glass powder enhances its compressive strength as well as split tensile strength. The optimum percentage of partially replacing cement by glass powder was 10% which showed the maximum improvement in compressive and split tensile strength.

  3. Laboratory and Full-Scale Simulations of the Behaviour of Reinforced Cement-Admixed Non-Plastic Soil for Deep Mixing Applications

    Directory of Open Access Journals (Sweden)

    Randy P. Asturias

    2015-05-01

    Full Text Available This paper proposes a new soil treatment method that employs reinforced deep mixing method (RDMM. In this method, the deep mixing pile is reinforced in a manner similar to a spirally reinforced concrete column. This paper aimed to evaluate the effectiveness of RDMM on improving the strength and deformation properties of a non-plastic soil. Four (4 experimental phases are conducted in this study and these are: 1 Physical property tests of the base soil, (2 Unconfined compressive strength (UCS tests on unreinforced cementadmixed soil specimens, (3 Unconfined compressive strength tests on reinforced cement-admixed soil specimens, and (4 Construction and load testing of full-scale reinforced deep mixing pile. The results unconfined compressive strength tests revealed that the influence of longitudinal bars on the unconfined compressive strength of reinforced cementadmixed non-plastic soil is pronounced at low cement content

  4. 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...

  5. 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.

  6. A mini slug test method for determination of a local hydraulic conductivity of an unconfined sandy aquifer

    OpenAIRE

    Hinsby, Klaus; Bjerg, Poul Løgstrup; Andersen, Lars J.; Skov, Bent Henning; Clausen, Erik V.

    2011-01-01

    A new and efficient mini slug test method for the determination of local hydraulic conductivities in unconfined sandy aquifers is developed. The slug test is performed in a small-diameter (1 inch) driven well with a 0.25 m screen just above the drive point. The screened drive point can be driven from level to level and thereby establish vertical profiles of the hydraulic conductivity. The head data from the test well are recorded with a 10 mm pressure transducer, and the initial head differen...

  7. 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. 

  8. Application of Strength Diagnosis.

    Science.gov (United States)

    Newton, Robert U.; Dugan, Eric

    2002-01-01

    Discusses the various strength qualities (maximum strength, high- and low-load speed strength, reactive strength, rate of force development, and skill performance), noting why a training program design based on strength diagnosis can lead to greater efficacy and better performance gains for the athlete. Examples of tests used to assess strength

  9. Satellite Image JPEG Compression

    OpenAIRE

    Ch. Ramesh; Lohitha, K.

    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.

  10. Image data compression

    OpenAIRE

    Goldberg, Mark A.

    1997-01-01

    The tutorial will expand on all of the topics outlined above and will provide additional information on other compression techniques. The practical implications of data compression and the important considerations in choosing a compression scheme will also be discussed. Development of new compression algorithms remains an active area of investigation and will continue to increase the degree of compression possible.

  11. Compressed convolution

    CERN Document Server

    Elsner, F

    2013-01-01

    We introduce the concept of compressed convolution, a technique to convolve a given data set with a large number of non-orthogonal kernels. In typical applications our technique drastically reduces the effective number of computations. The new method is applicable to convolutions with symmetric and asymmetric kernels and can be easily controlled for an optimal trade-off between speed and accuracy. It is based on linear compression of the collection of kernels into a small number of coefficients in an optimal eigenbasis. The final result can then be decompressed in constant time for each desired convolved output. The method is fully general and suitable for a wide variety of problems. We give explicit examples in the context of simulation challenges for upcoming multi-kilo-detector cosmic microwave background (CMB) missions. For a CMB experiment with O(10,000) detectors with similar beam properties, we demonstrate that the algorithm can decrease the costs of beam convolution by two to three orders of magnitude...

  12. 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.

  13. Experimental evaluation of connectivity influence on dispersivity under confined and unconfined radial convergent flow conditions

    Science.gov (United States)

    Guzzi, Silvia; Molinari, Antonio; Fallico, Carmine; Pedretti, Daniele

    2014-05-01

    Heterogeneity and connectivity have a significant impact on the fate and transport of contaminants due to the occurrence of formations with largest permeability than the surrounding geological materials, which can originate preferential pathways in groundwater system. These issues are usually addressed by tracer tests and a radial convergent (RC) flow setting is typically selected for convenience but more complicated for model interpretation than uniform flow transport. An experimental investigation was performed using RC tracer tests in a 3D intermediate scale physical model to illustrate the role of connected features on the estimation of dispersivity using the classical Sauty solution and the method of moments, under confined and unconfined aquifer conditions. The physical model consists of 26 piezometers located at difference distances from a constant-discharge central pumping well. The box is filled with gravel channels embedded in a sandy matrix and organized in different layers. Materials have been well characterized before and after the test. For the confined configuration, a silt layer was placed above the previous layers. Tracer tests were performed using potassium iodide solutions with concentration of 3•10-3 M and under a constant pumping flow rate of 0.05 L/s. To mimic a pulse injection in each piezometer we used syringes and pipes, whereas a probe allowed continuous measuring of tracer concentration. Average velocity and longitudinal dispersion coefficient were defined from the first and second central moment of the observed breakthrough curves for each piezometer (integrated over the outflow boundary of the domain) and using the classical curve matching from the Sauty's solution at different Péclet numbers. Results reveal in some cases that estimates of hydrodynamic parameters from the Sauty solution and the method of moments seem to be different. This is related to the different basic assumptions of the two methods applied, and especially because of the presence of preferential flow paths which have been found to strongly control the highest values of the average velocity at the source and affect the resulting longitudinal dispersion coefficient. This study showed additional lights on the impact of connectivity on transport and its role to obtain effective measurements of macrodispersion throughout the aquifer under RC transport. Reference: Fernàndez-Garcia D. et al. (2002) Convergent-flow tracer tests in heterogeneous media. Journal of Contaminant Hydrology 57 129-145. Fischer H. B. (1966) Longitudinal Dispersion in Laboratory and Natural Streams. Technical Rep. KH-R-12, California Institute of Technology, Pasadena, California. Gaspar E. (1987) Modern Trends in Tracer Hydrology, Volume II. CRC Press, Inc., Boca Raton, FL, USA.

  14. Response of a shallow sandy unconfined aquifer to tidal loading from a low-relief estuary

    Science.gov (United States)

    Enot, P.; Mao, X.; Barry, D. A.; Li, L.; Binley, A.

    2004-12-01

    A field study of the physical and chemical processes occurring in a sandy, unconfined aquifer (Scotland, UK), connected to a low-relief estuary was performed, with an emphasis on groundwater salinization and water table fluctuations. Data were collected from two adjacent monitoring transects located 20 m apart. These extended from the line of zero flux inland towards the estuary. Drill logs show that geological variations between the two monitoring transects are negligible. One transect consisted of three Multi-Level Sampling (MLS) boreholes, allowing detailed depth-specific pore water collection. Water level measurements were derived from pressure transducers located in fully slotted boreholes in the second transect. Water table elevations, pore water Electrical Conductivity (EC) and salinity data, concentrations of halogen ions Cl and Br as well as exchangeable cations Mg, Ca, K and Na were collected during 2001-4 along the monitoring transects. The aquifer response induced by high-low and neap-spring tidal estuarine oscillations was measured. Water level data indicate groundwater fluctuations are influenced by tidal loading from the estuary. Spectral analyses of ground and estuary water level time-series indicate the dominance of the principal lunar semi-diurnal frequency. For all frequencies, damping increases rapidly inland; phase shifts are also observed. The influence of the site settings (especially beach slope) on the tidal signal propagation is discussed. Pore water chemistry indicates a limited salinization zone at depth in the aquifer, and Br/Cl ratio calculations confirm its marine origin. Variations in EC and Cl concentrations do not follow any tidal pattern even near the shore, but are more likely influenced by seasonally varying groundwater recharge. Exchangeable cation concentrations in the aquifer salinization zone show no significant changes over time , except very near to the estuary. Here, the link between observed groundwater chemistry variations and tidal forcing is established by cross-analysis of physical and chemical data. This saline zone where exchange processes are influenced by tidal loading, has been identified as the landward front of the active estuarine intrusion in the aquifer.

  15. 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.

  16. Linear stability of the confined compressible reacting mixing layer

    Science.gov (United States)

    Shin, D. S.; Ferziger, J. H.

    1993-03-01

    This paper investigates the linear stability of confined mixing layers with special emphasis on the effects of heat release and compressibility. The results show that reflection of supersonic disturbances by the walls makes the confined supersonic mixing layer more unstable than the unconfined free shear layer. Decreasing the distance between the walls makes the flow more unstable. However, subsonic disturbances are relatively unaffected by the walls. Heat release and Mach number hardly change the growth rates of supersonic disturbances. The most unstable supersonic disturbances are two-dimensional in rectangular channel flows, but three-dimensional in partially confined flows. Finally, the reactants are not strongly mixed by supersonic instabilities, which mainly disturb one side of the layer.

  17. Linear stability of the confined compressible reacting mixing layer

    Science.gov (United States)

    Shin, D. S.; Ferziger, J. H.

    1993-01-01

    This paper investigates the linear stability of confined mixing layers with special emphasis on the effects of heat release and compressibility. The results show that reflection of supersonic disturbances by the walls makes the confined supersonic mixing layer more unstable than the unconfined free shear layer. Decreasing the distance between the walls makes the flow more unstable. However, subsonic disturbances are relatively unaffected by the walls. Heat release and Mach number hardly change the growth rates of supersonic disturbances. The most unstable supersonic disturbances are two-dimensional in rectangular channel flows, but three-dimensional in partially confined flows. Finally, the reactants are not strongly mixed by supersonic instabilities, which mainly disturb one side of the layer.

  18. Compressive beamforming.

    Science.gov (United States)

    Xenaki, Angeliki; Gerstoft, Peter; Mosegaard, Klaus

    2014-07-01

    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 scenarios such as coherent arrivals and single-snapshot data. An offset and resolution analysis is performed to indicate the limitations of CS. It is shown that the limitations are related to the beampattern, thus can be predicted. The high-resolution capabilities and the robustness of CS are demonstrated on experimental array data from ocean acoustic measurements for source tracking with single-snapshot data. PMID:24993212

  19. 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 scenarios such as coherent arrivals and single-snapshot data. An offset and resolution analysis is performed to indicate the limitations of CS. It is shown that the limitations are related to the beampattern, thus can be predicted. The high-resolution capabilities and the robustness of CS are demonstrated on experimental array data from ocean acoustic measurements for source tracking with single-snapshot data.

  20. Mechanical behavior assessment of concrete block masonry prisms under compression

    OpenAIRE

    Mohamad, Gihad; Lourenço, Paulo B.; Roman, Humberto R.

    2005-01-01

    The aim of this work is to critically assess a stress-strain model using experimental masonry prisms constructed from different blocks and mortar. The following conclusion may be drawn from this work: mortar is mostly responsible for the non-linear behavior of masonry. The initial tangent modulus, obtained taking into account the compressive strength, provides a strongly non-linear relationship between elasticity modulus and compressive strength.

  1. Concreto usinado: análise da variação da resistência à compressão e de propriedades físicas ao longo da descarga do caminhão betoneira / Ready mixed concrete: variability analysis of the compressive strength and physical properties along the unloading of the truck mixer

    Scientific Electronic Library Online (English)

    R., Mascolo; A. B., Masuero; D. C. C., Dal Molin.

    2013-04-01

    Full Text Available Visto a prática comum nos canteiros de obra da região de Porto Alegre, de coleta de amostras, para fins de ensaio e moldagem dos corpos-de-prova, logo da primeira porção do concreto descarregado do caminhão betoneira, somada à inexistência de normatização para aferição da qualidade do misturador e u [...] niformidade da mistura e a importância dos ensaios de controle de qualidade dos concretos. O presente trabalho tem como meta analisar a uniformidade de misturas de concreto em caminhão betoneira. A fim de atingir os objetivos realizaram-se coletas de amostras em cinco pontos distintos, ao longo da descarga do concreto do caminhão betoneira, para 13 lotes (amassadas) de concreto convencional. Não houve a formação de um perfil representativo das variações de resistência conforme o ponto de coleta e não foi constatada variação significativa entre pontos de coleta. Abstract in english The common practice, in construction sites of the region of Porto Alegre, to collect samples for testing, of the first portion of the concrete discharged from the truck mixer, and the lack of standardization to measure the quality of the mixer and uniformity of mixing and the importance of quality c [...] ontrol testing of concrete, this paper aims to examine the uniformity of ready mixed concrete. To achieve the aim was collected samples at five different points along the discharge of ready mixed concrete, for 13 lots of conventional concrete. There was not the formation of a representative profile of compressive resistance as the different collection point and there was not significant variation between the collection points.

  2. Shear strength properties of wet granular materials.

    Science.gov (United States)

    Richefeu, Vincent; El Youssoufi, Moulay Saïd; Radjaï, Farhang

    2006-05-01

    We investigate shear strength properties of wet granular materials in the pendular state (i.e., the state where the liquid phase is discontinuous) as a function of water content. Sand and glass beads were wetted and tested in a direct shear cell and under various confining pressures. In parallel, we carried out three-dimensional molecular dynamics simulations by using an explicit equation expressing capillary force as a function of interparticle distance, water bridge volume, and surface tension. We show that, due to the peculiar features of capillary interactions, the major influence of water content over the shear strength stems from the distribution of liquid bonds. This property results in shear strength saturation as a function of water content. We arrive at the same conclusion by a microscopic analysis of the shear strength. We propose a model that accounts for the capillary force, the granular texture, and particle size polydispersity. We find fairly good agreement of the theoretical estimate of the shear strength with both experimental data and simulations. From numerical data, we analyze the connectivity and anisotropy of different classes of liquid bonds according to the sign and level of the normal force as well as the bond direction. We find that weak compressive bonds are almost isotropically distributed whereas strong compressive and tensile bonds have a pronounced anisotropy. The probability distribution function of normal forces is exponentially decreasing for strong compressive bonds, a decreasing power-law function over nearly one decade for weak compressive bonds, and an increasing linear function in the range of tensile bonds. These features suggest that different bond classes do not play the same role with respect to the shear strength. PMID:16802930

  3. 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-

  4. Dynamic Relative Compression

    OpenAIRE

    Bille, Philip; Cording, Patrick Hagge; Gørtz, Inge Li; Skjoldjensen, Frederik Rye; Vildhøj, Hjalte Wedel; Vind, Søren

    2015-01-01

    Given a static reference string $R$ and a source string $S$, a relative compression of $S$ with respect to $R$ is an encoding of $S$ as a sequence of references to substrings of $R$. Relative compression schemes are a classic model of compression and have recently proved very successful for compressing highly-repetitive massive data set such as genomes and web-data. We initiate the study of relative compression in a dynamic setting where the compressed source string $S$ is s...

  5. Evaluation of High Temperature Strength and Emissivity of Nuclear Graphite

    International Nuclear Information System (INIS)

    The purpose of present study is to develop basic reference physical property data and evaluation techniques for selection and qualification of VHTR graphite core components. Properties and evaluation techniques examined in the present study include: - High Temperature Strength of Nuclear Graphite - Diametral Compressive Strength of Nuclear Graphite - Ultrasonic evaluation techniques - Emissivity - Coefficient of thermal expansion (CTE)

  6. 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.

  7. Compression limits in cascaded quadratic soliton compression

    DEFF Research Database (Denmark)

    Bache, Morten; Bang, Ole

    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.

  8. 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 ...

  9. Ground Rupturing Due to Entrapped Air/Gas in the Unconfined Zone

    OpenAIRE

    Manas Banerjee; Vimla Prasad Singh; Hridaya Narain Singh; Daya Shankar; Sun jay; Uma Shanker Singh

    2010-01-01

    The sudden and large oscillation of pressure of compressed air/gas entrapped in porous medium due to the changes in the actual pore-fluid pressure, during recharge of water following intense rainfall after a prolonged period of dryness such that the rainfall intensity exceeding infiltration capacity, leads to the generation of hydo-tremors. These hydro-tremors cause ground rupturing, subsidence, developments of cracks in the building, etc. A theoretical model has been presented to estimate th...

  10. 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.

  11. From “Smaller is Stronger” to “Size-Independent Strength Plateau”: Towards Measuring the Ideal Strength of Iron