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

Energy Technology Data Exchange (ETDEWEB)

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 25/sup 0/C and 100/sup 0/C; time, 3.5 x 10/sup 3/s and 950 x 10/sup 3/s (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/sup -5/s/sup -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.

Pfeifle, T.W.; Senseny, P.E.; Mellegard, K.D.

1987-01-01

2

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

International Nuclear Information System (INIS)

[en] 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

1987-01-01

3

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

Directory of Open Access Journals (Sweden)

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 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 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%.

M R Mshali; A T Visser

2012-01-01

4

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

International Nuclear Information System (INIS)

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

2008-01-01

5

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-02-20

6

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english 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 drill 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 (more) 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.

Kelessidis, V.C

2011-06-01

7

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english 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 strengt (more) h (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%.

Mshali, M R; Visser, A T

2012-01-01

8

Behavior of Stabilized Peat Soils in Unconfined Compression Tests  

Directory of Open Access Journals (Sweden)

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.

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

2008-01-01

9

Determination of friction coefficient in unconfined compression of brain tissue.  

UK PubMed Central (United Kingdom)

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 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 ? 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 ? was equal to 0.09±0.03, 0.18±0.04, 0.18±0.04 and 0.20±0.02 at strain rates of 1, 30, 60 and 90/s, respectively. Additional tests were also performed to analyze brain tissue under lubricated and bonded conditions, with and without initial contact of the top platen with the brain tissue, with different specimen aspect ratios and with different lubricants (Phosphate Buffer Saline (PBS), Polytetrafluoroethylene (PTFE) and Silicone). The test conditions (lubricant used, biological tissue, loading velocity) adopted in this study were similar to the studies conducted by other research groups. This study will help to understand the amount of friction generated during unconfined compression of brain tissue for strain rates of up to 90/s.

Rashid B; Destrade M; Gilchrist MD

2012-10-01

10

Determination of Friction Coefficient in Unconfined Compression of Brain Tissue  

CERN Multimedia

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...

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

2013-01-01

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)

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 resultado

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

2008-01-01

12

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish 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 (more) 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, 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 (more) 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 simultan

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

2008-12-01

13

Poroviscoelastic modeling of liver biomechanical response in unconfined compression.  

Science.gov (United States)

Mechanistic modeling approaches are important for understanding how fluid and solid components of the liver interact during impact trauma. This study uses poroviscoelasticity (PVE) theory to simulate liver biomechanical response in unconfined compression stress relaxation experiments, for variable ramp strain rates ranging from 0.001 to 0.1 s(-1). Specimens included 17 ex vivo porcine liver samples tested in a humidified temperature-controlled chamber. Liver response was modeled using ABAQUS, and best-fit parameters were determined using non-linear least-squares algorithms. The PVE model was able to capture the behavior of porcine liver in unconfined compression, with regression analyses for the ramp phase demonstrating high correlation between model and experiment (R(2) > 0.993, slope > 0.833, p < 0.05). The advantage of PVE modeling over traditional viscoelastic modeling is the ability to examine interstitial fluid pressure as a contributor to tissue mechanical response. This strategy creates new opportunities for quantifying an injury mechanism (burst injury) that is common in blunt abdominal trauma, and will lead to advancement of high-fidelity virtual crash test dummies, and improved vehicle safety. PMID:20177783

Raghunathan, Smitha; Evans, Douglas; Sparks, Jessica L

2010-02-23

14

Poroviscoelastic modeling of liver biomechanical response in unconfined compression.  

UK PubMed Central (United Kingdom)

Mechanistic modeling approaches are important for understanding how fluid and solid components of the liver interact during impact trauma. This study uses poroviscoelasticity (PVE) theory to simulate liver biomechanical response in unconfined compression stress relaxation experiments, for variable ramp strain rates ranging from 0.001 to 0.1 s(-1). Specimens included 17 ex vivo porcine liver samples tested in a humidified temperature-controlled chamber. Liver response was modeled using ABAQUS, and best-fit parameters were determined using non-linear least-squares algorithms. The PVE model was able to capture the behavior of porcine liver in unconfined compression, with regression analyses for the ramp phase demonstrating high correlation between model and experiment (R(2) > 0.993, slope > 0.833, p < 0.05). The advantage of PVE modeling over traditional viscoelastic modeling is the ability to examine interstitial fluid pressure as a contributor to tissue mechanical response. This strategy creates new opportunities for quantifying an injury mechanism (burst injury) that is common in blunt abdominal trauma, and will lead to advancement of high-fidelity virtual crash test dummies, and improved vehicle safety.

Raghunathan S; Evans D; Sparks JL

2010-05-01

15

Effect of multiple unconfined compression on cellular dense collagen scaffolds for bone tissue engineering.  

UK PubMed Central (United Kingdom)

Plastic compression of hydrated collagen gels rapidly produces biomimetic scaffolds of improved mechanical properties. These scaffolds can potentially be utilised as cell seeded systems for bone tissue engineering. This work investigated the influence of multiple unconfined compression on the biocompatibility and mechanical properties of such systems. Single and double compressed dense collagen matrices were produced and characterised for protein dry weight, morphology and mechanical strength. Compression related maintenance of the seeded HOS TE85 cell line viability in relation to the extent of compression was evaluated up to 10 days in culture using the TUNEL assay. Fluorescence Live/Dead assay was conducted to examine overall cell survival and morphology. Cell induced structural changes in the dense collagenous scaffolds were assessed by routine histology. The mechanical properties of the cellular scaffolds were also evaluated as a function of time in culture. It is clear that a single plastic compression step produced dense collagenous scaffolds capable of maintaining considerable cell viability and function as signs of matrix remodeling, and maintenance of mechanical properties were evident. Such scaffolds should therefore be further developed as systems for bone tissue regeneration.

Bitar M; Salih V; Brown RA; Nazhat SN

2007-02-01

16

Effect of multiple unconfined compression on cellular dense collagen scaffolds for bone tissue engineering.  

Science.gov (United States)

Plastic compression of hydrated collagen gels rapidly produces biomimetic scaffolds of improved mechanical properties. These scaffolds can potentially be utilised as cell seeded systems for bone tissue engineering. This work investigated the influence of multiple unconfined compression on the biocompatibility and mechanical properties of such systems. Single and double compressed dense collagen matrices were produced and characterised for protein dry weight, morphology and mechanical strength. Compression related maintenance of the seeded HOS TE85 cell line viability in relation to the extent of compression was evaluated up to 10 days in culture using the TUNEL assay. Fluorescence Live/Dead assay was conducted to examine overall cell survival and morphology. Cell induced structural changes in the dense collagenous scaffolds were assessed by routine histology. The mechanical properties of the cellular scaffolds were also evaluated as a function of time in culture. It is clear that a single plastic compression step produced dense collagenous scaffolds capable of maintaining considerable cell viability and function as signs of matrix remodeling, and maintenance of mechanical properties were evident. Such scaffolds should therefore be further developed as systems for bone tissue regeneration. PMID:17323154

Bitar, Malak; Salih, Vehid; Brown, Robert A; Nazhat, Showan N

2007-02-01

17

Compressive strength of terrigenous lignite  

Energy Technology Data Exchange (ETDEWEB)

This article discusses the results of a research project which set out to study the factors affecting the strength and deformation characteristics of lignite from the Megalopolis region of Greece by referring to the strength characteristics under uni-axial compression; the anisotropy and effect of the deformation rate were previously examined in a series of simple-compression tests. (12 refs.)

Anagnostopoulos, A.G.

1982-02-01

18

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

1993-01-01

19

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 (...

Tan, Ö.; Sahin Zaimoglu, A.

20

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-01-15

 
 
 
 
21

Saturated-Unsaturated flow in a Compressible Leaky-unconfined Aquifer  

CERN Document Server

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...

Mishra, Phoolendra K; Kuhlman, Kristopher L

2011-01-01

22

The Uniaxial Compressive Strength of Soft Rock  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

D. S. Agustawijaya

23

The Uniaxial Compressive Strength of Soft Rock  

Directory of Open Access Journals (Sweden)

Full Text Available 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 were lower than that of partially weathered rocks. In conjunction with the uniaxial compression test, point load strength index tests, IS(50), have also been conducted in order to obtain a correlation between the UCS and the point load strength index IS(50). The results showed that the IS(50) could well be correlated with the UCS. A conversion factor of 14 is proposed for soft rock materials.

D. S. Agustawijaya

2007-01-01

24

Confined compressive strength analysis can improve PDC bit selection. [Polycrystalline Diamond Compact  

Energy Technology Data Exchange (ETDEWEB)

A rock strength analysis program, through intensive log analysis, can quantify rock hardness in terms of confined compressive strength to identify intervals suited for drilling with polycrystalline diamond compact (PDC) bits. Additionally, knowing the confined compressive strength helps determine the optimum PDC bit for the intervals. Computing rock strength as confined compressive strength can more accurately characterize a rock's actual hardness downhole than other methods. the information can be used to improve bit selections and to help adjust drilling parameters to reduce drilling costs. Empirical data compiled from numerous field strength analyses have provided a guide to selecting PDC drill bits. A computer analysis program has been developed to aid in PDC bit selection. The program more accurately defines rock hardness in terms of confined strength, which approximates the in situ rock hardness downhole. Unconfined compressive strength is rock hardness at atmospheric pressure. The program uses sonic and gamma ray logs as well as numerous input data from mud logs. Within the range of lithologies for which the program is valid, rock hardness can be determine with improved accuracy. The program's output is typically graphed in a log format displaying raw data traces from well logs, computer-interpreted lithology, the calculated values of confined compressive strength, and various optional rock mechanic outputs.

Fabain, R.T. (Hycalog, Houston, TX (United States))

1994-05-16

25

Unconfined compression experiments on Topopah Spring Member tuff at 22{degrees}C and a strain rate of 10{sup {minus}9} s{sup {minus}1}: Data report; Yucca Mountain Site Characterization Project  

Energy Technology Data Exchange (ETDEWEB)

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{sup {minus}9} s{sup {minus}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{sup {minus}9} s{sup {minus}1}.`` The mean and standard deviation values of ultimate strength, Young`s modulus and Poisson`s ratio determined from these experiments are 85.4{plus_minus}21.7 MPa, 33.9{plus_minus}4.6 GPa, and 0.09{plus_minus}0.07, respectively.

Martin, R.J. III; Boyd, P.J.; Noel, J.S. [New England Research, Inc., White River Junction, VT (United States); Price, R.H. [Sandia National Labs., Albuquerque, NM (United States)

1993-08-01

26

Confined compressive strength of saline ice at intermediate strain rates  

Energy Technology Data Exchange (ETDEWEB)

Detailed knowledge of the mechanical behavior of saline ice at elevated confining pressure and at intermediate strain rates is essential input to predictive models used to advance technology for projectile penetration of ice. We present here our results on ice behavior at confining pressures of 0.1 to 50 MPa, temperatures of -10 to -20/sup 0/C, strain rates of 10/sup -2/ and 0.5/s. These results indicate stress-strain behavior in directions perpendicular and parallel to a sheet of first-year sea ice. Results show that at a strain rate of 1.0 x 10/sup -2//s and -10/sup 0/C, values of ultimate stress for unconfined vertical and horizontal orientations are in the range of 4 to 5 MPa. When the strain rate is raised to 0.5/s, at the same temperature, ultimate stress for unconfined vertical and horizontal samples increases from 5 to 8 MPa and 4.5 to 5.5 MPa, respectively. The ultimate stress for confined vertical samples at 10/sup -2//s is much higher than that of confined horizontal samples, and although the horizontal samples become ductile at a mean stress of about 7.5 MPa and have a corresponding ultimate stress of 12 MPa, vertical samples remain brittle at mean stresses as high as 26 MPa with a corresponding ultimate stress of 24 MPa. Horizontal samples tested at 0.5/s have much higher confined compressive strength, and the mean stress associated with the brittle-to-ductile transition increases to more than 30 MPa.

Blair, S.C.

1986-06-01

27

Tests for Strength Characteristics of a Schistose Gneiss. Preliminary Tests.  

Science.gov (United States)

This report presents the strength characteristics of schistose gneiss as revealed by laboratory tests for shear, compressive, and tensile strength of the material. Unconfined compression and direct tension tests were made of intact rock while triaxial com...

E. J. Deklotz T. L. Neff W. J. Heck

1965-01-01

28

COMPRESSIVE STRENGTH TESTING OF EARTH MORTARS  

Directory of Open Access Journals (Sweden)

Full Text Available This paper discusses the compressive strength of earth mortars. The goal is to use these mortars for masonry construction. Although it is necessary to study the whole masonry behaviour, the scope of this paper refers to the mortar only, without taking into account the blocks. As with other masonry units, compressive strength is a basic measure of quality for masonry mortars. However, there is a great variety of methodology for determining their parameters and properties, such as different samples geometry, the way strains are measured and also the platen restraint effect adopted. The present paper outlines certain experimental devices used to determine compressive strength of earth mortars and tries to show their influence on the properties determined. Proposals for the future development of testing earth mortars are outlined.

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

2007-01-01

29

Compressive Strength of Autoclaved Aerated Concrete Blockwork  

Directory of Open Access Journals (Sweden)

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.

Y.A. Daou

2001-01-01

30

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

Directory of Open Access Journals (Sweden)

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.

Tan, Ö.; Sahin Zaimoglu, A.

2007-01-01

31

Improved solution for saturated-unsaturated flow to a partially penetrating well in a compressible unconfined aquifer  

Science.gov (United States)

Tartakovsky and Neuman [2007] developed an analytical solution for flow to a partially penetrating well pumping at a constant rate from a compressible unconfined aquifer considering an unsaturated zone of infinite thickness. In their solution three-dimensional, axially symmetric unsaturated flow was described by a linearized version of Richards’ equation in which both relative hydraulic conductivity and water content vary exponentially with incremental capillary pressure head relative to its air entry value. Both exponential functions were characterized by a common exponent. We present an improved solution in which relative hydraulic conductivity and water content are characterized by separate parameters and the unsaturated zone has finite thickness. Our four-parameter representation of these functions is more flexible than the three-parameter version of Mathias and Butler [2006], who consider flow in the unsaturated zone to be strictly vertical and the pumping well to be fully penetrating. We investigate the effects of unsaturated zone thickness and constitutive parameters on drawdown in the unsaturated and saturated zones as functions of position and time. We then use our new solution to analyze data from synthetic and real pumping tests.

Mishra, P. K.; Neuman, S. P.

2009-12-01

32

Improved forward and inverse analyses of saturated-unsaturated flow toward a well in a compressible unconfined aquifer  

Science.gov (United States)

We present an analytical solution for flow to a partially penetrating well in a compressible unconfined aquifer that allows inferring its saturated and unsaturated hydraulic properties from drawdowns recorded in the saturated and/or unsaturated zone. We improve upon a previous such solution due to Tartakovsky and Neuman (2007) by (1) adopting a more flexible representation of unsaturated zone constitutive properties and (2) allowing the unsaturated zone to have finite thickness. Both solutions account for horizontal as well as vertical flows throughout the system. We investigate the effects of unsaturated zone constitutive parameters and thickness on drawdowns in the saturated and unsaturated zones as functions of position and time; demonstrate the development of significant horizontal hydraulic gradients in the unsaturated zone in response to pumping; validate our solution against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van Genuchten-Mualem constitutive model; use our solution to analyze drawdown data from a pumping test conducted by the U.S. Geological Survey at Cape Cod, Massachusetts; and compare our estimates of van Genuchten-Mualem parameters with laboratory values obtained for similar materials in the area.

Mishra, Phoolendra Kumar; Neuman, Shlomo P.

2010-07-01

33

Hydrodynamic compressibility of high-strength ceramics  

Energy Technology Data Exchange (ETDEWEB)

In this study we have developed the techniques to investigate the hydrodynamic response of high-strength ceramics by mixing these powders with copper powder, preparing compacts, and performing shock compression tests on these mixtures. Hydrodynamics properties of silicon carbide, titanium diboride, and boron carbide to 30 GPa were examined by this method, and hydrodynamic compression data for these ceramics have been determined. We have concluded, however, that the measurement method is sensitive to sample preparation and uncertainties in shock wave measurements. Application of the experimental technique is difficult and further efforts are needed.

Grady, D.E.

1993-08-01

34

Temperature dependence of uniaxial compressive strength of Hnilec granite  

Directory of Open Access Journals (Sweden)

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

Laba? Milan

1997-01-01

35

Long-term compressive strength and some other properties of controlled low strength materials made with pozzolanic cement and Class C fly ash.  

UK PubMed Central (United Kingdom)

Controlled low strength material (CLSM) is a flowable mixture that can be used as a backfill material in place of compacted soils. CLSM (or flowable fill) require no tamping or compaction to achieve its compressive strength and typically has a load carrying capacity much higher than that of compacted soils, but can be proportioned to allow future excavation. In this study, several different CLSM mixtures containing Class C fly ash (FA) obtained from Soma Thermal Power Plant in Turkey, crushed limestone sand (CLS), and a minimal amount of pozzolanic cement (PZC) were produced. The mass of PZC was kept constant for all mixtures at 5% of FA by mass. The mechanical and physical properties of CLSM mixtures such as unconfined compressive strength, water absorption by capillarity and EP toxicity were investigated by a series of laboratory tests. CLSM mixtures with low PZC contents and high Class C FA and CLS contents can be produced with excellent flowability and low unconfined compressive strengths in the range of 1.16-2.80 MPa at 365-days age when re-excavation at later ages might be needed. The results presented here show a new field of application for Soma FA in CLSM mixtures, resulting in great advantages in waste minimization, as well as, conservation of resources and environment.

Türkel S

2006-09-01

36

Compressive strength of delaminated aerospace composites.  

UK PubMed Central (United Kingdom)

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

Butler R; Rhead AT; Liu W; Kontis N

2012-04-01

37

Study on compressive strength characteristics of Bio-Coal  

Energy Technology Data Exchange (ETDEWEB)

In this paper, we aim at dealing with the compressive strength characteristics of Bio-Coal including theoretical analysis and experimental research. The essential theoretical analysis is based up on particulates and intermolecular forces mechanics. The orthogonality design principle proves to be useful in the scientific arranging experimentions. The method of making use of deviation analysis is capable of providing some useful conclusions. Namely, the main influence factors of Bio-Coal on compressive strength characteristics are found out. From our orthogonality design experiments, the authors come to realize the primary and secondary sequence of influence on compressive strength of Bio-Coal. In addition, the formula of best compressive strength was found out. And then recent single factor experiments in this area suggested that the actual regularity of the influence on compressive strength of Bio-Coal was consistent with its theoretical analysis.

Liu Weijun; Fu Guomin [Harbin Univ. of Science & Technology (China); Zhang Shuhua [Inst. of Harbin Cable Works (China); Li Songsheng [Harbin Boiler Works (China)

1997-07-01

38

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

Directory of Open Access Journals (Sweden)

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

Ahmad Mujahid Ahmad Zaidi

2010-01-01

39

Mechanical strength in sod peat. Development of laboratory testing methods for determination of tumbler strength and compression strength  

Energy Technology Data Exchange (ETDEWEB)

In this report tumbler strength has been evaluated in combination with compression strength. During the project a high pressure press was modified. At the compression a thrust load equivalent to a ground pressure of 0-5 kp/cm/sup 2/ was used. Low humified sphagnumpeat had the best strength, both with and without compression. For low humified sphagnumpeat, compressed with 2 kp/cm/sup 2/ and then tumbled in a rotating drum, the crush content increased to about 5% absolute numbers for pieces less than 45 mm, while the other types of peat increased to 12-15%, in comparison with the tumbler strength merely. These studies show that compression strength in combination with tumbler strength elaborate on the results we have received from tumbler strength only. In this investigation we have not found any further information about low humified sphagnumpeat as compared to other kinds of peat. The precision of the method combining tumbler strength with compression strength is not satisfying. In the future, the sod peat machinery will probably produce a more tenable sod peat. It means that compression strength should be a part of the investigation of the mechanical strength for sod peat. For additional studies in the future, a better equipment for compression strength ought to be developed, and further knowledge studies must be done.

Sandstroem, T.; Burvall, J.

1985-08-01

40

STRENGTH SHRINKAGE AND CREEP OF CONCRETE IN TENSION AND COMPRESSION  

Directory of Open Access Journals (Sweden)

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

S A Kristiawan

2006-01-01

 
 
 
 
41

Ultimate strength property of concrete under triaxial compressive stresses  

International Nuclear Information System (INIS)

[en] The purpose was to examine the ultimate strength criteria of concrete under short-term multiaxial compressive stresses, as an aid to designing and analyzing the concrete structures subjected to multiaxial stresses, such as prestressed or reinforced concrete vessel structures. The ultimate strength of concrete under multiaxial stresses is a function of the state of stress. Therefore, the ultimate strength of concrete elements can be properly determined only by considering the interaction of the various components of the state of stress. The paper attempts to define such ultimate strength criteria as a function of the state of stress, valid for concrete under biaxial and triaxial compressive stress states. In mathematical description of ultimate strength criteria for concrete under combined states of stress, the ultimate strength under multiaxial compressive stresses was defined as the maximum load-carrying capacity of a test specimen. (orig./HP)

1983-01-01

42

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

Directory of Open Access Journals (Sweden)

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.

Mehrdad Aryafar; Abdoul R. Ghotbi; Mehdi Aryafar; Amin Avaei

2008-01-01

43

Compressive strength of brick masonry made with weak mortars  

DEFF Research Database (Denmark)

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.

Pedersen, Erik Steen; Hansen, Klavs Feilberg

2013-01-01

44

Evaluation of Adhesive and Compressive Strength of Glass Ionomer Cements  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim of the study was to assess, compare and evaluate the adhesive strength and compressive strength of different brands of glass ionomer cements to a ceramometal alloy. (A) Glass ionomer cements: GC Fuji II (GC Corporation, Tokyo), Chem Flex (Dentsply DeTrey, Germany), Glass ionomer FX (Shofu-11...

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

45

Effect of Hand Mixing on the Compressive Strength of Concrete  

Directory of Open Access Journals (Sweden)

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.

James Isiwu AGUWA

2010-01-01

46

Compressive Strength of Longitudinally Stiffened GRP Panels  

DEFF Research Database (Denmark)

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

Böhme, J.; Noury, P.

1996-01-01

47

PREPARATION OF BIOACTIVE NANOSTRUCTURE SCAFFOLD WITH IMPROVED COMPRESSIVE STRENGTH  

Directory of Open Access Journals (Sweden)

Full Text Available Highly porous scaffolds with open structure are today the best candidates for bone substitution to ensure bone oxygenation and angiogenesis. In this study, we developed a new route to enhance the compressive strength of porous hydroxyapatite scaffold made of natural bone. Briefly, the spongy bone of an adult bovine was extracted, annealed, and coated by a nanostructure bioactive glass layer to be subsequently sintered at different temperatures. The apatite formation ability on the surfaces of the coated scaffolds was investigated by standard procedures. Our results showed that the scaffold and coating microstructure consisted of the grains smaller than 100 nm. These nanostructures improved the compressive strength and bioactivity of highly porous scaffold. The results showed that with increasing the sintering temperature, the compressive strength of scaffolds increased while their in vitro bioactivity decreased.

F. TAVANGARIAN; R. EMADI

2011-01-01

48

Compressive strength of concrete and mortar containing fly ash  

Energy Technology Data Exchange (ETDEWEB)

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 specifications required for building and highway construction, are provided. Such materials can thus significantly reduce construction costs.

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

1997-01-01

49

Compressive strength of concrete and mortar containing fly ash  

Energy Technology Data Exchange (ETDEWEB)

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.

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

50

Compressive strength of concrete and mortar containing fly ash  

Science.gov (United States)

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 specifications required for building and highway construction, are provided. Such materials can thus significantly reduce construction costs. 33 figs.

Liskowitz, J.W.; Wecharatana, M.; Jaturapitakkul, C.; Cerkanowicz, A.E.

1997-04-29

51

Standard test methods for flatwise compressive strength of sandwich cores  

Energy Technology Data Exchange (ETDEWEB)

These methods cover determination of the compressive properties of sandwich cores. These properties are usually determined for design purposes, in a direction normal to the plane of facings as the core would be placed in a structural sandwich construction. The test procedures pertain to compression in this direction in particular, but also can be applied with possible minor variations to determining compressive properties in other directions. Two test methods are described as follows: method A provides complete deformation data, and; method B, an alternative method, measures crushing strength only.

1980-01-01

52

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

International Nuclear Information System (INIS)

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

2002-01-01

53

Hyphal content determines the compression strength of Candida albicans biofilms.  

UK PubMed Central (United Kingdom)

Candida albicans is the most frequently isolated human fungal pathogen among species causing biofilm-related clinical infections. Mechanical properties of Candida biofilms have hitherto been given no attention, despite the fact that mechanical properties are important for selection of treatment or dispersal of biofilm organisms due to a bodily fluid flow. The aim of this study was to identify the factors that determine the compression strength of Candida biofilms. Biofilms of C. albicans wild-type parental strain Caf2-1, mutant strain Chk24 lacking Chk1p [known to be involved in regulation of morphogenesis (yeast-to-hyphae transition)] and gene-reconstructed strain Chk23 were evaluated for their resistance to compression, along with biofilms of Candida tropicalis GB 9/9 and Candida parapsilosis GB 2/8, derived from used voice prosthetic biofilms. Additionally, cell morphologies within the biofilm, cell-surface hydrophobicities and extracellular polymeric substance composition were determined. Our results suggest that the hyphae-to-yeast ratio influences the compression strength of C. albicans biofilms. Biofilms with a hyphal content >50 % possessed significantly higher compressive strength and were more difficult to destroy by vortexing and sonication than biofilms with a lower hyphal content. However, when the amount of extracellular DNA (eDNA) in biofilms of C. albicans Caf2-1 and Chk24 increased, biofilm strength declined, suggesting that eDNA may influence biofilm integrity adversely.

Paramonova E; Krom BP; van der Mei HC; Busscher HJ; Sharma PK

2009-06-01

54

Estimating rock compressive strength from Rock Abrasion Tool (RAT) grinds  

Science.gov (United States)

Each Mars Exploration Rover carries a Rock Abrasion Tool (RAT) whose intended use was to abrade the outer surfaces of rocks to expose more pristine material. Motor currents drawn by the RAT motors are related to the strength and hardness of rock surfaces undergoing abrasion, and these data can be used to infer more about a target rock's physical properties. However, no calibration of the RAT exists. Here, we attempt to derive an empirical correlation using an assemblage of terrestrial rocks and apply this correlation to data returned by the rover Spirit. The results demonstrate a positive correlation between rock strength and RAT grind energy for rocks with compressive strengths less than about 150 MPa, a category that includes all but the strongest intact rocks. Applying this correlation to rocks abraded by Spirit's RAT, the results indicate a large divide in strength between more competent basaltic rocks encountered in the plains of Gusev crater (Adirondack-class rocks) and the weaker variety of rock types measured in the Columbia Hills. Adirondack-class rocks have estimated compressive strengths in the range of 70-130 MPa and are significantly less strong than fresh terrestrial basalts; this may be indicative of a degree of weathering-induced weakening. Rock types in the Columbia Hills (Wishstone, Watchtower, Clovis, and Peace class) all have compressive strengths <50 MPa and are consistent with impactites or volcanoclastic materials. In general, when considered alongside chemical, spectral, and rock textural data, these inferred compressive strength results help inform our understanding of rock origins and modification history.

Thomson, B. J.; Bridges, N. T.; Cohen, J.; Hurowitz, J. A.; Lennon, A.; Paulsen, G.; Zacny, K.

2013-06-01

55

Compressive shear bond strength of core buildup materials.  

Science.gov (United States)

New tooth-colored restorative materials have been developed with the goal of replacing amalgam. These restoratives are marketed as packable composite and ormocer. The purpose of the present study was to compare the compressive shear bond strengths of these new materials with that of hybrid composite and amalgam as core materials. Standardized core buildups were made on four groups of extracted molars, with 10 teeth per group. Three tooth-colored restorative materials (Filtek Z 250, Filtek P 60, and Definite) and an amalgam (SDI Permite) were used. Specimens were placed in a special jig at a 45-degree angle. The compressive shear bond strength was obtained using a universal testing machine. The Kruskal-Wallis test was used to compare the groups, and pairwise comparisons were made by Mann-Whitney U test (P ormocer (Definite) had the lowest. The strengths of packable composite, hybrid composite, and amalgam as core materials were not significantly different (P > .05). PMID:16642907

Görücü, Jale; Saygili, Gülbin; Ozgünaltay, Gül

2006-04-01

56

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

1989-01-01

57

Insulation interlaminar shear strength testing with compression and irradiation  

Energy Technology Data Exchange (ETDEWEB)

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 {times} 25 {times} 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 {times} 10{sup 9} and 2 {times} 10{sup 10} 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.

McManamy, T.J.; Brasier, J.E.; Snook, P. (Oak Ridge National Lab., TN (USA); Idaho National Engineering Lab., Idaho Falls, ID (USA); Princeton Univ., NJ (USA))

1989-01-01

58

Compressive shear bond strength of core buildup materials.  

UK PubMed Central (United Kingdom)

New tooth-colored restorative materials have been developed with the goal of replacing amalgam. These restoratives are marketed as packable composite and ormocer. The purpose of the present study was to compare the compressive shear bond strengths of these new materials with that of hybrid composite and amalgam as core materials. Standardized core buildups were made on four groups of extracted molars, with 10 teeth per group. Three tooth-colored restorative materials (Filtek Z 250, Filtek P 60, and Definite) and an amalgam (SDI Permite) were used. Specimens were placed in a special jig at a 45-degree angle. The compressive shear bond strength was obtained using a universal testing machine. The Kruskal-Wallis test was used to compare the groups, and pairwise comparisons were made by Mann-Whitney U test (P < .05). Filtek P 60, a packable composite resin, had the greatest compressive shear bond strength values in all instances, and the ormocer (Definite) had the lowest. The strengths of packable composite, hybrid composite, and amalgam as core materials were not significantly different (P > .05).

Görücü J; Saygili G; Ozgünaltay G

2006-04-01

59

A thermodynamic criterion of strength of crystals: Nonhydrostatic compression  

Energy Technology Data Exchange (ETDEWEB)

We formulated a thermodynamic criterion with the theoretical strength of crystals according to which the ultimate strength of the solid is linked with the condition of its local thermodynamic equilibrium with the liquid. Theoretical estimates of the tensile strength of a number of defect-free whisker crystals are in satisfactory agreement with the experimental data. This criterion can be used not only in tensile loading of the crystals but also in their compression. In the latter case, however, the tensile strength should be linked not with mechanical rupture of the system but with a certain mechanism of its ductility represented by recrystallization through a {open_quotes}virtual{close_quotes} liquid phase. 17 refs., 5 figs.

Naumov, I.I.; Ol`khovik, G.A.; Panin, V.E. [Inst. of Physics of Strength and Mfaterials Science, Tomsk (Russian Federation)

1992-01-01

60

Residual Compressive Strength of Laterized Concrete Subjected to Elevated Temperatures  

Directory of Open Access Journals (Sweden)

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.

Robert M. Brooks

2010-01-01

 
 
 
 
61

Experimental and analytical studies on compression strength of anisotropic rocks  

Energy Technology Data Exchange (ETDEWEB)

The paper presents results of investigations into anisotropy of uniaxial compression strength of two types of sandstone, two types of claystone and two types of siltstone from underground black coal mines of the Upper Silesian basin. Several analytical criteria are compared: criterion of an open elliptical crack, criterion of a closing crack, criterion of a mathematical crack without and with friction, criterion of a single plane of weakness, criterion of continuously variable shear strength and criterion of an open elliptical hole. Mechanical properties of six rock types from Upper Silesia are characterized using the analytical criteria. The results of analyses are shown in 7 diagrams and 14 tables. (32 refs.) (In Polish)

Borecki, M.; Kwasniewski, M.

1982-01-01

62

Tow collapse model for compression strength of textile composites  

Energy Technology Data Exchange (ETDEWEB)

The unidirectional composite compression strength model based on microbuckling of fibers embedded in a rigid-plastic matrix was extended to multiaxial laminates and textile composites. The resulting expression is a function of matrix yield strength under the fiber constraint, fiber misalignment angle, fiber volume fraction, and the area fractions of various sets of inclined tows. The analysis was verified by experimentation. Compression tests were conducted on laminated, three-dimensional triaxially braided and orthogonally woven composites using the IITRI test specimen. The laminate specimens were made up of AS4/3501-6 graphite/epoxy composite with (0){sub 24}, (0/30/0/{minus}30){sub 3S}, and ((0/90)6/0){sub S} stacking sequence. Textile composites were made of BASF G30-500 graphite fiber tows (tow size is 6K) and Dow Chemicals Tactix 123 matrix. Fiber preform architecture of braided and woven composites before resin consolidation was 0/{+-}17 and 0/90, respectively and after consolidation it was about (7/{+-}20) and (5/90/90), respectively. The analysis agreed reasonably well with the test data for all cases considered. The axial fiber/tow misalignment angle for laminated, braided, and woven composites were about 4, 7, and 5 degrees, respectively. The compression strength was found to be strongly dependent on the percentage of axial tows and its misalignment angle. A small variation in the off-axis fiber/tow orientation had marginal effect on the compression strength. Hence, the off axis tow misalignment angle can be assumed to be same as the initial laminate or the two orientation angle.

Emehel, T.C.; Shivakumar, K.N. [North Carolina A and T State Univ., Greensboro, NC (United States)

1995-12-31

63

INTRA-RING COMPRESSION STRENGTH OF LOW DENSITY HARDWOODS  

Directory of Open Access Journals (Sweden)

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

Audrey Zink-Sharp; Carlile Price

2006-01-01

64

Natural minerals mixture for enhancing concrete compressive strength  

Directory of Open Access Journals (Sweden)

Full Text Available The construction material quality is required to be improved in order to enhancing structure stability, optimizing construction cost and quality. The kaolin and bentonite have been mixed in equal quantity and treated by heat for 1 hour under 600 ºC, 800 ºC and 1000 ºC to create new minerals under high temperature condition to introduce an acceptable concrete additive for achieving concrete compressive strength in early age. To study micro properties of additive-cement mixture, X-ray and FESEM experiments have been used. The results indicate that acceptable proportion of unheated kaolin-bentonite is improving the concrete compressive response. But if kaolin-bentonite mixture treated by heat under 800 ºC and in quantity of 12 % has been used in concrete mixed design, then the concrete compressive strength of 7 days shows the best result. The result is due to the development of new minerals under high temperature condition in mineral mixture and also kaolin-bentonite additive change cement past crystal and lead to enhancement of nano structural cement bonding

Abdoullah Namdar

2012-01-01

65

Concrete aggregate and cement mass content effects on compressive strength  

Directory of Open Access Journals (Sweden)

Full Text Available The mass content of aggregate (ma) and of cement (mc) of concrete comprise coefficient calculated as ma/mc. Some methods used for designing of concrete mixtures take into consideration this coefficient. In this paper, concrete mixtures were prepared so that mass of cement, water cement factor and granulometric composition have been varied. Values of the coefficient ma/mc in experimental research ranged between 7,20 in concrete mixtures mixed with 250 kg of cement to 3,60 in concrete mixtures mixed with 500 kg per 1m3. From the aspect of compressive strength of concrete, it has been established that optimum values of the coefficient ma/mc depend on the granulometric composition and water cement factor. At higher water cement factors, larger values of ma/mc coefficient are required to achieve the maximum strength under the given conditions.

Grdi? Zoran; Topli?i?-?ur?i? Gordana; Stoji? Nikola

2010-01-01

66

Strength and stiffness of thermally rectified eucalyptus wood under compression  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english 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 furnace 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 affect (more) ed 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.

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

2013-10-01

67

Strength and stiffness of thermally rectified eucalyptus wood under compression  

Directory of Open Access Journals (Sweden)

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 furnace 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.

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

2013-01-01

68

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 resistance between concrete and the vertical side of the wall. It has been observed that compressive strength increases steeply as the yield strength increases up to a certain level. Plastic viscosity, however, shows optimum value for maximum compressive strength.

Aminul Islam Laskar; Sudip Talukdar

2007-01-01

69

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

Directory of Open Access Journals (Sweden)

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%.

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

2008-01-01

70

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

Directory of Open Access Journals (Sweden)

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.

Akram Hasheminezhad; Seyed Mojtaba Zebarjad; Seyed Abdolkarim Sajjadi; Laleh Rahanjam

2012-01-01

71

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

Energy Technology Data Exchange (ETDEWEB)

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

Ericksen, R.H.

1986-08-01

72

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

Directory of Open Access Journals (Sweden)

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.

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

2011-01-01

73

Influence of Plastic Waste Fibers on the Strength of Lime-Rice Husk Ash Stabilized Clay Soil  

Directory of Open Access Journals (Sweden)

Full Text Available A study has been undertaken to investigate the strength of stabilized clay-soil reinforced with randomly distributed discrete plastic waste fibers by carrying out unconfined compressive strength and tensile-split strength test. In this study, the clay soil was stabilized with lime and rice husk ash mixtures. The effect of the fiber length and content on the compressive and split tensile strength was investigated. The laboratory investigation results show that inclusion of the plastic waste fiber increased significantly both the unconfined compressive strength and tensile-split strength of the stabilized clay soil. The fiber length plays a significant contribution in increasing the soil strength. To contribute for any significant improvement on compression as well as tensile strength, the fiber length should be in range of 20 mm to 40 mm. Fiber reinforcements also reduced soil brittleness by providing smaller loss of post-peak strength.

A. S. Muntohar

2009-01-01

74

Sublaminate buckling and compression strength of stitched uniweave graphite/epoxy laminates  

Energy Technology Data Exchange (ETDEWEB)

Effects of through-the-thickness stitching on the sublaminate buckling and residual compression strength (often referred as compression-after-impact or CAI strength) of graphite/epoxy uniweave laminates are experimentally investigated. Primarily, three stitching variables: type of stitch yarn, linear density of stitch yam and stitch density were studied. Delaminations were created by implanting teflon inserts during processing. The improvement in the CAI strength of the stitched laminates was up to 400% compared to the unstitched laminates. Stitching was observed to effectively restrict sublaminate buckling failure of the laminates. The CAI strength increases rapidly with increase in stitch density. It reaches a peak CAI strength that is very close to the compression strength of the undamaged material. All the stitch yams in this study demonstrated very close performance in improving the CAI strength. It appears that any stitch yarn with adequate breaking strength and stiffness successfully restricts the sublaminate buckling.

Sharma, S.K. [GE Corporate R and D Center, Schenectady, NY (United States); Sankar, B.V. [Univ. of Florida, Gainesville, FL (United States). Dept. of Aerospace Engineering, Mechanics and Engineering Science

1995-12-31

75

Compression Strength of Fir and Beech Wood Modified by Citric Acid  

Directory of Open Access Journals (Sweden)

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.

Bogoslav Šefc; Jelena Trajkovi?; Tomislav Sinkovi?; Marin Hasan; Iva Ištok

2012-01-01

76

Influence of Plastic Waste Fibers on the Strength of Lime-Rice Husk Ash Stabilized Clay Soil  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A study has been undertaken to investigate the strength of stabilized clay-soil reinforced with randomly distributed discrete plastic waste fibers by carrying out unconfined compressive strength and tensile-split strength test. In this study, the clay soil was stabilized with lime and rice husk ash...

A. S. Muntohar

77

The effect of various mixing and placement techniques on the compressive strength of mineral trioxide aggregate.  

UK PubMed Central (United Kingdom)

INTRODUCTION: The aim of this study was to evaluate the effect of various mixing techniques including mechanical and manual mixing as well as the effect of ultrasonic agitation during placement on the compressive strength of mineral trioxide aggregate (MTA). METHODS: Tooth-colored ProRoot MTA (Dentsply Maillefer, Ballaigues, Switzerland) and white MTA Angelus (Angelus Soluções Odontologicas, Londrina, Brazil) were used. One gram of each powder was mixed with a 0.34-g aliquot of distilled water. Specimens were mixed either by mechanical mixing of capsules for 30 seconds at 4,500 rpm or by a saturation technique and the application of a condensation pressure of 3.22 MPa for 1 minute. Half of the specimens were placed in stainless steel molds and agitated using indirect ultrasonic activation. All specimens were subjected to compressive strength testing after 4 days. RESULTS: The compressive strength values of ProRoot MTA were significantly greater than those of MTA Angelus (P < .05). The highest compressive strength values were recorded from ProRoot MTA samples that were mixed mechanically and placed using ultrasonic activation (mean = 101.71 MPa), whereas the lowest values were recorded for MTA Angelus samples that were mixed manually and placed without ultrasonic activation (mean = 53.47 MPa). Ultrasonically agitated groups had higher compressive strength values (P < .001). The specimens mixed mechanically had higher compressive strength values than those mixed manually (P < .05). CONCLUSIONS: The compressive strength values of ProRoot MTA were significantly greater than those of MTA Angelus. Mechanical mixing enhanced the compressive strength of the material. Regardless of the mixing techniques applied, ultrasonic agitation improved the compressive strength of the material.

Basturk FB; Nekoofar MH; Günday M; Dummer PM

2013-01-01

78

[Production of denture by preform compression molding method. Part 3. Retentive strength of artificial teeth  

UK PubMed Central (United Kingdom)

A preform compression molding method to make a polysulfone denture has been reported. Retentive strength of artificial teeth to the denture base was examined to select artificial teeth for the compression molding method. Ceramic teeth with metal pins and polysulfone teeth heated at above 140 degrees C were retained to the denture base by useful retentive strength. Acrylic teeth on which the adhesive was used were also retained by useful strength. Each of the teeth, acrylic teeth, ceramic teeth and polysulfone teeth, could be used in the compression molding method.

Kimura H; Teraoka F; Saitoh Y; Tamura M

1989-05-01

79

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

Directory of Open Access Journals (Sweden)

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 strength steel fiber reinforced concrete mixes (NSSFRC) was 0.55, and the water-cementitious ratio (w/c+s) for the high strength fiber reinforced concrete mixes (HSSFRC) was 0.31. For each mix, three 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.

Khaled Marara; Özgür Erenb; ?brahim Yitmena

2011-01-01

80

Simplified and unified approach to characterization of compressive residual strength of impact-damaged CFRP laminates  

Energy Technology Data Exchange (ETDEWEB)

A new simplified and unified approach was proposed based on a coupon specimen to characterize compressive residual strength of impact-damaged CFRP laminates both on destructive and non-destructive basis. Impact load was applied directly to a coupon specimen by using a drop-weight impact test tower, and impact-damaged area of the specimen was measured by ultrasonic C-scan method. After the impact test, compressive load was applied with a newly developed compression test fixture without any additional device to prevent buckling. The residual compressive strength was characterized in terms of the effect of applied impact damage, damage area and dent of the specimens. It was shown that the residual compressive strength could be estimated by non-destructive means such as acoustic emission and vibration pattern imaging applied to the damaged coupon specimen. (orig.) 10 refs.

Kimpara, I.; Kageyama, K.; Suzuki, T.; Ohsawa, I. [Tokyo Univ. (Japan). Dept. of Naval Architecture and Ocean Engineering

1998-05-01

 
 
 
 
81

Compressive strength of various honeycombs; Kakushu hanikamu kozo no asshuku kyodo ni tsuite  

Energy Technology Data Exchange (ETDEWEB)

Among the mechanical properties of honeycomb and structure of honeycomb sandwich, the relation between compressive strength when compressive load is applied along the height direction of honeycomb core and honeycomb density was analyzed using classical buckling stress based on the classical linear theory of cylindrical shell that receives compressive load on axial direction. For each aluminium, aramid and polyimide honeycomb along with the honeycomb sandwich structure, the error with the experiment value in case of induction method using cylindrical shell without rib was less than that of cylindrical shell with a fixed rib. The theoretical curve of compressive strength of aluminium honeycomb differed greatly with the experimental curve. In case of aramid honeycomb and polyimide honeycomb, the experimental curve of compressive strength and density showed good coincident with the theoretical curve. Besides, polyimide honeycomb sandwich structure showed the same trend as that of polyimide honeycomb. 21 refs., 8 figs., 5 tabs.

Ogawa, T. [Kanazawa Inst. of Technology, Ishikawa (Japan); Okazaki, N. [Kanazawa Inst. of Technology, Ishikawa (Japan). Graduate Student

1993-07-15

82

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

Energy Technology Data Exchange (ETDEWEB)

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 the compressive strength of the substrate concrete improves the bond strength and changes the rupture mode from adhesive to monolithic. A finite element analysis showed that, increasing the difference between the compressive strengths of the added concrete and the substrate concrete, higher values of normal stress are present in the interface, for the same level of shear stress. The study presented in this paper reveals that the added concrete, normally with higher compressive strength than the substrate concrete, may possibly have an influence on concrete-to-concrete bond strength. Therefore, design of shear at the interface between concrete cast at different ages, according to Eurocode 2, could be improved, since here only the lowest strength concrete is considered. (author)

Julio, Eduardo N.B.S. [University of Coimbra-Polo II, Coimbra (Portugal). Department of Civil Engineering; Branco, Fernando A.B. [IST, Lisbon (Portugal). Department of Civil Engineering; Silva, Vitor D. [University of Coimbra-Polo II, Coimbra (Portugal). Department of Civil Engineering; Lourenco, Jorge F. [ISEC, Coimbra (Portugal). Department of Civil Engineering

2006-12-15

83

Functional relation between mineral composition and compression strength of carboniferous rocks from the pilot mine Bogdanka  

Energy Technology Data Exchange (ETDEWEB)

Investigations of dependence of mechanical properties of carboniferous rocks of the Lublin Coal Basin on their mineral composition are discussed. Determining mechanical properties of rocks surrounding coal seams is necessary for optimization of roof control methods and forecasting subsidence, deformations of walls of workings and roof, and floor tendency to swelling. Twenty five rock samples from the Bogdanka mine were tested: sandstones, mudstones, claystones, sideritic claystone, siderites and coal. The following properties were tested: compression strength of rock samples with natural moisture content, compression strength of dried rock samples, compression strength of rock with maximum moisture content, tensile properties and shear properties. Investigations show that compression strength of rock samples with natural moisture content increases with increasing content of quartz and feldspars and decreases with increasing content of coal and and silty minerals. No functional relationship between mechanical properties of sedimentary rocks and proportion of carbonates or siderite can be established. (4 refs.) (In Polish)

Kowalski, W.M.; Motyczka, A.; Stalega, S.; Motyczka, W.

1981-01-01

84

A new approach to determination of compressive strength of fly ash concrete using fuzzy logic  

Energy Technology Data Exchange (ETDEWEB)

In this study, determination of effect of fly ash (FA) content on the compressive strength of concrete depending on water/cement ratio and concrete age was investigated by use of fuzzy logic (FL) approach. In the approach of modelling with FL, compressive strength values of various sample of concrete that produced by replacement of cement by F class of FA by ratio of 0 (control), 10%, 20% and 30% were used. Water/binder ratio of these concrete samples was varied between 0.27-0.60 in six different values. Experimental compressive strength values of the concrete specimens at 3, 7, 28, 90, 180 and 365 days compared with FL values obtained using the fuzzy sets. Optimum FA content and water/binder ratio for the best compressive strength for early age and hardened concrete can be obtained with FL.

Tayfun Uygunoglu; Osman Unal

2006-11-15

85

The correlation of layer waviness defect on compression strength of carbon fiber composite material  

International Nuclear Information System (INIS)

[en] As advanced composite materials having superior physical and mechanical properties are being developed, optimization of their production process is eagerly being sought. One of the most common defects in production of structural composites is layer waviness. Layer waviness is more pronounced in thick section flat and cylindrical laminates that are extensively used in missile casings. Submersibles and space platforms. Layer waviness undulates the entire layer of a multidirectional laminate in through-the-thickness direction leading to gross deterioration of its compression strength. This research investigates the influence of multiple layer waviness in a double nest formation on the compression strength of a composite laminate. Different wave fractions of wavy 0 degree layer were fabricated in IM/855 1- 7 carbon- epoxy composite laminate on a steel mold using single step fabrication procedure. The laminate was cured on a heated press according to specific curing cycle. Static compression testing was performed using short block compression fixture on an universal testing machine. The purpose of these tests was to determine the effects of multiple layer wave regions on the compression strength of composite laminate. The experimental and analytical results revealed that up to about 35% fraction of wavy 0 degree layers. The reduction in compression strength of composite laminate was constant after fraction of wavy 0 degree layers exceeded 35%. This analysis indicated that the percentage of 0 degree wavy layer may be used to estimate the reduction in compression strength of a composite laminate under restricted conditions. (author)

2005-01-01

86

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

Energy Technology Data Exchange (ETDEWEB)

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)

Moelholt Jensen, F.

2003-06-01

87

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 streng...

Li, Yi-Hai; Franssen, Jean-Marc

88

Green and early age compressive strength of extruded cement mortar monitored with compression tests and ultrasonic techniques  

International Nuclear Information System (INIS)

Knowledge about the early age compressive strength development of cementitious materials is an important factor for the progress and safety of many construction projects. This paper uses cylindrical mortar specimens produced with a ram extruder to investigate the transition of the mortar from plastic and deformable to hardened state. In addition, wave transmission and reflection measurements with P- and S-waves were conducted to obtain further information about the microstructural changes during the setting and hardening process. The experiments have shown that uniaxial compression tests conducted on extruded mortar cylinders are a useful tool to evaluate the green strength as well as the initiation and further development of the compressive strength of the tested material. The propagation of P-waves was found to be indicative of the internal structure of the tested mortars as influenced, for example, by the addition of fine clay particles. S-waves used in transmission and reflection mode proved to be sensitive to the inter-particle bonding caused by the cement hydration and expressed by an increase in compressive strength.

2006-01-01

89

Effect of size, shape and end condition of test specimen on compressive strength of high-strength concrete  

Energy Technology Data Exchange (ETDEWEB)

Compressive testing of high-strength concrete is a critical issue on which no consensus has yet been reached. Among the many factors that are mostly under discussion are the size, shape and end condition of test specimens for high-strength concrete. The experimental program described herein was designed primarily to investigate the effects and the possible interactions of the above-mentioned factors on compressive strength of high-strength concrete. Three levels of specimen sizes, three methods of specimen capping (mould surface, sulphur capping, grinding) and four grades of concrete strengths were selected. A 3x3x4 factorial experimental design was adopted with two replicates (each an average of three specimens), giving a total of 72 test values (216 specimen). The strictest possible precautions were taken to ensure that all other factors which would conceivably effect the compressive strength were held constant. The statistical methods utilized included analyses of variance, linear regressions and pairwise comparisons of factor main effects.

Ipatti, A.

1992-12-31

90

Tests of cold-formed high strength stainless steel compression members  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The paper describes a test program on cold-formed high strength stainless steel compression members. The duplex stainless steel having the yield stress and tensile strength up to 750 and 850 MPa, respectively, was investigated. The material properties of the test specimens were obtained from tensile...

Young, B; Lui, WM

91

Fracture Energy of High-Strength Concrete in Compression  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Dahl, Henrik; Brincker, Rune

92

Effect of lightweight aggregate intrinsic Strength on lightweight concrete compressive strength and modulus of elasticity  

Directory of Open Access Journals (Sweden)

Full Text Available The study of Structural Lightweight Concrete (SLC), which is a material generally composed of cement, water and lightweight aggregate, has been mainly focused on developing particular cases. Then, the main objective of this research was to generalise the knowledge of this type of material. Particularly, the effect of replacing conventional coarse aggregate by lightweight aggregate on mechanical properties of concrete was studied. SLC may be conceived as a two -phase material. The first phase, composed of cement, water and siliceous natural sand, is called the "resistant phase", and contributes to the structural strength. The second phase is the lightweight phase, comprised of coarse lightweight aggregate, and it is meant to decrease the concrete density. In this way it would be possible to describe the mechanical behaviour of concrete, based on lightweight aggregate and the cement mortar parameters. The obtained results allow for the proposition of relationships between mechanical properties of SLC (such as compressive strength and modulus of elasticity) and the constituent materials properties and amount. At the same time, an easily measured index representing the structural capability of lightweight aggregate is also proposed, this index allows to estimate the potential mechanical properties of concrete which could be obtained by using a particular aggregate.El estudio del Hormigón Ligero Estructural (HLE), material compuesto generalmente por cemento, agua y árido ligero, ha estado enfocado principalmente al desarrollo de casos particulares. Por lo anterior, el objetivo principal de esta investigación fue generalizar el conocimiento sobre este material. En particular, la meta de este trabajo fue estudiar el efecto que tiene el reemplazo de árido convencional por un árido ligero, en las propiedades mecánicas del hormigón. El modelo aplicado conceptualiza al HLE como un material de dos fases, una denominada "soportante", constituida por pasta de cemento más arena normal y otra "ligera", formada por árido grueso ligero. La primera aporta la resistencia estructural y la segunda disminuye la densidad del hormigón. De esta forma sería posible describir el comportamiento mecánico del hormigón en función de parámetros del árido ligero y del mortero de cemento. A partir de los resultados se proponen relaciones entre las propiedades mecánicas del HLE (resistencia a compresión y rigidez) y las propiedades y cantidad de los materiales constituyentes. Asimismo, se propone un índice para caracterizar la capacidad estructural del árido ligero, que es de fácil medición y permite estimar las propiedades mecánicas potenciales del hormigón que se podrían obtener con el uso de un árido determinado.

Videla, C.; López, M.

2002-01-01

93

Prediction of the compressive strength of vertebral bodies of the lumbar spine by quantitative computed tomography  

Energy Technology Data Exchange (ETDEWEB)

The ultimate compressive strength of 36 thoracolumbar vertebrae was determined experimentally. In addition, the trabecular bone mineral content was measured by single energy quantitative computed tomography. The areas of fractured endplates were also determined by computed tomography. The results show that a linear relationship exists betwen the compressive strength and the product of bone density and endplate area. These data allow an in vivo prediction of vertebral body strength using a noninvasive method with a standard error of estimate amounting to less than 0.95 kN.

Biggemann, M.; Hilweg, D.; Brinckmann, P.

1988-06-01

94

CEMENT TYPE KNEADED MOLDED ARTICLE HAVING HIGH BENDING STRENGTH AND COMPRESSIVE STRENGTH, AND METHOD OF PRODUCTION THEREOF  

UK PubMed Central (United Kingdom)

A molded cured product obtained from a kneaded material using hydraulic powdery material, latent hydraulic fine powder, compounding water and if necessary, fine aggregate is hot aged under a specific condition so that silicic acid anion of at least a trimer is formed in calcium silicate hydrate formed in the texture of this molded cured product. This molded cured product has a compressive strength of at least 1,000 kgf/cm<2> and a bending strength of at least 150 kgf/cm<2>, and can suitably improve strength characteristics, particularly the bending strength as characterising drawback of cement type products, without using a specific reinforcing material and a compounding material such as a fiber, or even when these reinforcing material and compounding material are used, by drastically reducing their quantities.; Accordingly, the present invention can advantageously provide a unique and novel cement type product. Incidentally, beautiful mortar or concrete products by glost firing, which has not been able to be practised due to unavoidable drop of strength characteristics, can be produced and provided as products having desirable bending strength, compressive strength and elastic modulus.

SONODA HIROKI; KAGA KIKUO; NITTA TATSUO; TOYAMA MASAKAZU; OSAWA SEIHACHI; KATO KAZUMI

95

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

Science.gov (United States)

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. PMID:24094224

Wang, Ai-Juan; Yuan, Zhi-Long; Zhang, Jiao; Liu, Lin-Tao; Li, Jun-Ming; Liu, Zheng

2013-09-06

96

The estimation of compressive strength of normal and recycled aggregate concrete  

Directory of Open Access Journals (Sweden)

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.

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

2011-01-01

97

The influence of double nested layer waviness on compression strength of carbon fiber composite materials  

International Nuclear Information System (INIS)

[en] As advanced composite materials having superior physical and mechanical properties are being developed, optimization of their production processes in eagerly being sought. One of the most common defect in production of structural composites is layer waviness. Layer waviness is more pronounced in thick section flat and cylindrical laminates that are extensively used in missile casings, submersibles and space platforms. Layer waviness undulates the entire layers of a multidirectional laminate in through-the-thickness direction leading to gross deterioration of its compression strength. This research investigates the influence of multiple layer waviness in a double nest formation on the compression strength of a composite laminate. Different wave fractions of wave 0 degree centigrade layer fabricated in IM/85510-7 carbon - epoxy composite laminate on a steel mold using single step fabrication procedure. The laminate was cured on a heated press according to specific curing cycle. Static compression testing was performed using NASA short block compression fixture on an MTS servo Hydraulic machine. The purpose of these tests was to determine the effects of multiple layer wave regions on the compression strength of composite laminate. The experimental and analytical results revealed that up to about 35% fraction of wave 0 degree layer exceeded 35%. This analysis indicated that the percentage of 0 degree wavy layer may be used to estimate the reduction in compression strength of a composite laminate under restricted conditions. (author)

1997-01-01

98

Compressive Strength of Notched Poly(Phenylene Sulfide) Aerospace Composite: Influence of Fatigue and Environment  

Science.gov (United States)

The purpose of this work is to evaluate the influences of fatigue and environmental conditions (-55 °C, 23 °C, and 82 °C/Wet) on the ultimate compression strength of notched carbon-fiber-reinforced poly(phenylene sulfide) composites by performing open-hole compression (OHC) tests. Analysis of the fatigue effect showed that at temperatures of -55 and 23 °C, the ultimate OHC strengths were higher for fatigued than for not-fatigued specimens; this could be attributed to fiber splitting and delamination during fatigue cycling, which reduces the stress concentration at the hole edge, thus increasing the composite strength. This effect of increasing strength for fatigued specimens was not observed under the 82 °C/Wet conditions, since the test temperature near the matrix glass transition temperature ( T g) together with moisture content resulted in matrix softening, suggesting a reduction in fiber splitting during cycling; similar OHC strengths were verified for fatigued and not-fatigued specimens tested at 82 °C/Wet. Analysis of the temperature effect showed that the ultimate OHC strengths decreased with increasing temperature. A high temperature together with moisture content (82 °C/Wet condition) reduced the composite compressive strengths, since a temperature close to the matrix T g resulted in matrix softening, which reduced the lateral support provided by the resin to the 0° fibers, leading to fiber instability failure at reduced applied loads. On the other hand, a low temperature (-55 °C) improved the compressive strength because of possible fiber-matrix interfacial strengthening, increasing the fiber contribution to compressive strength.

Niitsu, G. T.; Lopes, C. M. A.

2013-08-01

99

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

UK PubMed Central (United Kingdom)

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.

Bogas JA; Gomes MG; Gomes A

2013-07-01

100

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

Science.gov (United States)

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

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

2013-01-03

 
 
 
 
101

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english 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 (more) (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.

Gherardi Hein, Paulo Ricardo; Tarcísio Lima, José

2012-11-01

102

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

Directory of Open Access Journals (Sweden)

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.

Paulo Ricardo Gherardi Hein; José Tarcísio Lima

2012-01-01

103

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

Energy Technology Data Exchange (ETDEWEB)

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.

DeTeresa, S J; Hoppel, C P

1999-03-01

104

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

Directory of Open Access Journals (Sweden)

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

Gokhan Gunduz; Suleyman Korkut; Deniz Aydemir; Ilter Bekar

2009-01-01

105

Investigation of adding fluoroapatite nanoparticles on compressive strength and corrosion behaviour of dental amalgams  

Directory of Open Access Journals (Sweden)

Full Text Available In recent years, there have been many efforts to improve biological and biocompatibility features of amalgam. The aim of this research was investigating the effect of adding fluoroapatite (FA) nanoparticles on compressive strength and corrosion behaviour of dental amalgam. An amalgam alloy powder was mixed with 1, 3 and 5 wt.% of FA nanoparticles to form composite powders. Compressive strength of the corresponding dental amalgam samples was measured on the first and seventh day after preparation and the corrosion behaviour was investigated by potentiodynamic polarization electrochemical test in 0.9 wt.% salt solution (physiologic serum). The results showed that the amalgam containing 1 wt.% FA nanoparticles has higher compressive strength then the pure amalgam and with increasing the FA content in amalgam to 3 and 5 wt.%, the compressive strength decreases. The results also indicated that the corrosion behaviour of the amalgam sample with 1 wt.% FA is similar to the corrosion behaviour of the original amalgam, while with increasing the weight percentage of fluorapatite, the corrosion resistance decreases. The results of this research showed that adding FA nanoparticles in amounts of up to 1 wt.% to amalgam alloy improve compressive strength, has no destructive effect on corrosion behaviour of the material and can increase its biocompatibility and biological activity.

Fahimeh Mirlohi; Ali Doostmohammadi; Ahmad Monshi

2012-01-01

106

Comparison on compressive strength of paraffin waste form with H/D ratio and loading rate  

International Nuclear Information System (INIS)

[en] In case that the mixing weight ratio of waste form between boric acid and paraffin was 3.3/1, which had been adopted in the concentrate waste drying system (CWDS) of domestic nuclear power plants. Using several specimens with different diameters and heights, 50/100mm specimens. Compressive strength were measured. The experiment result showed that the small diameter specimens of compressive strength are increased more than large diameter specimens. (d=50> 75 >100 mm) The average compressive strength of specimens showed that the range from 22.43 kgf/cm2 to 38.57 Kgf/cm2(NRC standard?4.1 Kgf/cm2). NRC standard is recommended that the compressive strength test specimens be right circular cylinders, 2 to 3 inches in diameter, with a height-to-diameter (H/D) ratio of approximately two and compressive strength were increased more than large loading rate. As test result, this conditions are a good agreement, and estimated

2003-01-01

107

Comparison on compressive strength of paraffin waste form with H/D ratio and loading rate  

Energy Technology Data Exchange (ETDEWEB)

In case that the mixing weight ratio of waste form between boric acid and paraffin was 3.3/1, which had been adopted in the concentrate waste drying system (CWDS) of domestic nuclear power plants. Using several specimens with different diameters and heights, 50/100mm specimens. Compressive strength were measured. The experiment result showed that the small diameter specimens of compressive strength are increased more than large diameter specimens. (d=50> 75 >100 mm) The average compressive strength of specimens showed that the range from 22.43 kgf/cm{sup 2} to 38.57 Kgf/cm{sup 2}(NRC standard{>=}4.1 Kgf/cm{sup 2}). NRC standard is recommended that the compressive strength test specimens be right circular cylinders, 2 to 3 inches in diameter, with a height-to-diameter (H/D) ratio of approximately two and compressive strength were increased more than large loading rate. As test result, this conditions are a good agreement, and estimated.

Kwak, K. K.; Yoo, Y. G. [KAERI, Taejon (Korea, Republic of)

2003-07-01

108

Ultrasonic inspection and compressive strength of composites with surface wrinkles  

Energy Technology Data Exchange (ETDEWEB)

Surface wrinkles in composites can adversely affect mechanical performance as well as inspection results. During conventional ultrasonic C-scan inspections, the bulging of the wrinkle scatters the sound beam and makes it difficult to detect voids beneath the wrinkles. This paper describes fabrication procedures adopted to introduce simulated surface wrinkles with pre-determined geometries as well as an ultrasonic inspection method to detect voids under wrinkles. The inspection technique is based on launching the ultrasonic beam at oblique angles enabling separation of scattering echoes from those of internal flaws. Preliminary results of compression tests on wrinkled specimens with or without simulated voids as compared to virgin specimens are also presented.

Fahr, A.; Forsyth, D.; Bullock, M.; Poon, C. [National Research Council of Canada, Ottawa, Ontario (Canada)

1995-10-01

109

Compressive Strength of Volcanic Ash/Ordinary Portland Cement Laterized Concrete  

Directory of Open Access Journals (Sweden)

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.

Olawuyi B.J.; Olusola K. O.

2010-01-01

110

Retentive and compressive strengths of modified zinc oxide-eugenol cements.  

UK PubMed Central (United Kingdom)

OBJECTIVES: This investigation sought to improve the handling and physical properties of a commonly used temporary zinc oxide-eugenol cement by changing the base/accelerator (B/A) ratio or combining it with a petroleum jelly or fluoride varnish. METHODS: Twelve modifications of a temporary cement were evaluated in terms of retentive strength, compressive strength at 24 h, film thickness and by scanning electron microscopy. RESULTS: Decreasing the B/A mixing ratio increased the retentive and compressive strengths, but reduced the film thickness of the cement. By increasing the percentage of incorporated petroleum jelly or fluoride varnish in the cement, there was a progressive decrease in the retentive and compressive strengths and in film thickness. CONCLUSIONS: Modifications of a zinc oxide-eugenol temporary cement to change the B/A ratio or to incorporate additives resulted in variations in physical properties. All modified forms of the cement had a film thickness less than 25 microns and a compressive strength below 35 MPa. With a wide range of retentive strength, modified forms of zinc oxide-eugenol cement may be found to have diverse clinical applications.

Lee SY; Wang CC; Chen DC; Lai YL

2000-01-01

111

Effect of pH on compressive strength of some modification of mineral trioxide aggregate  

Science.gov (United States)

Objectives: Recently, it was shown that NanoMTA improved the setting time and promoted a better hydration process which prevents washout and the dislodgment of this novel biomaterial in comparison with WTMA. This study analyzed the compressive strength of ProRoot WMTA (Dentsply), a NanoWMTA (Kamal Asgar Research Center), and Bioaggregate (Innovative Bioceramix) after its exposure to a range of environmental pH conditions during hydration. Study Design: After mixing the cements under aseptic condition and based on the manufacturers` recommendations, the cements were condensed with moderate force using plugger into 9 × 6 mm split molds. Each type of cement was then randomly divided into three groups (n=10). Specimens were exposed to environments with pH values of 4.4, 7.4, or 10.4 for 3 days. Cement pellets were compressed by using an Instron testing machine. Values were recorded and compared. Data were analyzed by using one-way analysis of variance and a post hoc Tukey’s test. Results: After 3 days, the samples were solid when probed with an explorer before removing them from the molds. The greatest mean compressive strength 133.19±11.14 MPa was observed after exposure to a pH value of 10.4 for NanoWMTA. The values decreased to 111.41±8.26 MPa after exposure to a pH value of 4.4. Increasing of pH had a significant effect on the compressive strength of the groups (p<0.001). The mean compressive strength for the NanoWMTA was statistically higher than for ProRoot WMTA and Bioaggregate (p<0.001). Moreover, increasing of pH values had a significant effect on compressive strength of the experimental groups (p<0.001). Conclusion: The compressive strength of NanoWMTA was significantly higher than WMTA and Bioaggregate; the more acidic the environmental pH, the lower was the compressive strength. Key words:Compressive strength, mineral trioxide aggregate, Nano.

Saghiri, Mohammad A.; Garcia-Godoy, Franklin; Asatourian, Armen; Lotfi, Mehrdad; Khezri-Boukani, Kaveh

2013-01-01

112

Microstructure and compressive strength of SiC-platelet-reinforced borosilicate composites  

Energy Technology Data Exchange (ETDEWEB)

The microstructure and compressive strength of SiC-platelet-reinforced borosilicate composites have been examined in this study. During sintering, following cold compaction, borosilicate glass crystallized into cristobalite, and the thermal expansion mismatch between the parent glass and the crystallized phase led to extensive microcracking of the matrix. Cristobalite growth (hence cracking) could be suppressed to some extent by opting for a rapid hot-pressing cycle. Composites fabricated with various volume fractions of SiC platelets were tested in compression. A maximum compressive strength of 510 MPa was observed at 40 vol% of platelets. Further, the compressive flow behavior of these composites has been explored in the vicinity of the glass transition temperature. At temperatures above 625 C, borosilicate glass and its composites exhibited Newtonian viscous flow characteristics. Their flow stress at a given strain rate is, however, seen to increase with increasing volume fraction of SiC platelets.

Verma, A.R.B.; Murthy, V.S.R.; Murty, G.S. [Indian Inst. of Tech., Kanpur (India). Dept. of Materials and Metallurgical Engineering

1995-10-01

113

Effect of Different Cure Conditions on Compressive Strength of Concrete Having Different Properties  

Directory of Open Access Journals (Sweden)

Full Text Available This research was carried out to determine unit weights and compressive strengths for the concrete samples produced with normal aggregate obtained Erzurum province and lightweight aggregate obtained Van-Ercis province and cured under different conditions. Unit weights of concrete specimens produced with normal aggregate were 2325 under air cure, 2360 under water cure, 2358 kg m-3 under steam cure. Unit weights of concrete specimens produced with lightweight aggregate were 906 under air cure, 1060 under water cure, 972 kg m-3 under steam cure. In average, 28 days compressive strength of concrete specimens produced with normal aggregate were 180.3 under air cure, 270.0 under water cure, 240.1 kgf cm-2 under steam cure. In average 28 days compressive strength of concrete specimens produced with lightweight aggregate were 60.0 under air cure, 45.2 under water cure, 52.4 kgf cm-2 under steam cure.

Bahar Kocaman; Recep Yanik; Canan Kose; Adem Ozturk

2011-01-01

114

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

International Nuclear Information System (INIS)

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

2009-01-01

115

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

International Nuclear Information System (INIS)

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

2003-01-01

116

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

UK PubMed Central (United Kingdom)

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 polytetrafluoroethylene 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 37 degrees C +/- 2 degrees C 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 (p<0.05). For the composite resin, light curing with the QTH source did not produce statistically significant difference (p>0.05) 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.

Silva CM; Dias KR

2009-01-01

117

Effect of Specimen Size on Compressive, Modulus of Rupture and Splitting Strength of Cement Mortar  

Directory of Open Access Journals (Sweden)

Full Text Available It is well known that the strength of any tested matrix materials like concrete or mortar is affected by the specimen size; therefore it is important to consider the effect of specimen size when estimating the ultimate strength of such materials. This study presents the effect of specimen size on the mechanical properties of cement mortar. These include the compressive, splitting strength and modulus of rupture. For the compressive strength three different sizes of cylinder and three sizes of cubes are used and the same sample sizes are used for testing the splitting strength. Also three different sizes of specimen are used for modulus of rupture. Preparation, casting and testing procedures are carried out according to ASTM specifications using constant mix proportion of cement/sand and water cement ratio. The obtained results show that the three mechanical properties of mortar affected by the specimen size specially the compressive strength and splitting strength of cylinders. Some best fit relationships that relate these properties are presented in this study although it cannot be generalized due to the fact that the presented results are based on limited number of tested specimens with constant mix proportion.

Sura A. Majeed

2011-01-01

118

Effects of compressive prestress on bending strength of nuclear-grade isotropic graphite  

Energy Technology Data Exchange (ETDEWEB)

Changes in Young's modulus, electrical resistivity, and bending strength of IG-11 graphite. in the directions parallel to and perpendicular to compressive prestress were measured, and a model for compressive deformation of polycrystalline graaphite was proposed. The electrical resistivity decreased with increase in compressive prestress up to 0.4 sigmasub(f), where sigmasub(f) denotes the average compressive strength, 80 MPa, of the graphite. Then it increased abruptly with increasing the prestress to above 0.4 sigmasub(f), whereas that in the direction perpendicular to the loading axis increased over the whole prestress level. Young's modulus was unchanged with increase in the prestress up to 0.4 sigmasub(f) and it decreased abruptly above 0.4 sigmasub(f), whereas that in the direction perpendicular to the axis decreased with increase in the prestress up to 0.4 sigmasub(f) and decreased slightly above 0.4 sigmasub(f). Bending strength increased with increase in the prestress up to 0.4 sigmasub(f) and decreased above 0.4 sigmasub(f), whereas the strength in the two directions perpendicular to the loading axis unchanged up to 0.2 sigmasub(f) thereafter those decreased abruptly. A model was proposed for compressive deformation mechanism of polycrystalline graphite.

Yoda, S.; Oku, T. (Japan Atomic Energy Research Inst., Tokai, Ibaraki. Tokai Research Establishment); Kougo, Y.

1983-07-01

119

Micromechanical strength effects in shock compression of solids  

Energy Technology Data Exchange (ETDEWEB)

Time-resolved shock-wave measurements and post-shock recovery have long been used for inferring the underlaying micromechanics controlling high-rate deformation of solids; this requires considerable subjective interpretation. In spite of this, 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. This cycle involves the elements of the elastic precursor, plastic loading wave, pulse duration, release wave, and post-mortem examination. Those topics are examined, with emphasis on the second and fourth elements. Cu and Ta results show how shock data can be used to determine the transition from deformation mechanism of thermal activation to that of dislocation drag. Release-wave studies indicate that the leading observable release disturbance in fcc metals may not be propagating with the ideal longitudinal elastic-wave speed. 5 figs, 18 refs.

Johnson, J.N.

1993-06-01

120

Micromechanical strength effects in shock compression of solids  

Energy Technology Data Exchange (ETDEWEB)

Time-resolved shock-wave measurements and post-shock recovery have long been used for inferring the underlaying micromechanics controlling high-rate deformation of solids; this requires considerable subjective interpretation. In spite of this, 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. This cycle involves the elements of the elastic precursor, plastic loading wave, pulse duration, release wave, and post-mortem examination. Those topics are examined, with emphasis on the second and fourth elements. Cu and Ta results show how shock data can be used to determine the transition from deformation mechanism of thermal activation to that of dislocation drag. Release-wave studies indicate that the leading observable release disturbance in fcc metals may not be propagating with the ideal longitudinal elastic-wave speed. 5 figs, 18 refs.

Johnson, J.N.

1993-01-01

 
 
 
 
121

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

Directory of Open Access Journals (Sweden)

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

M - Sabouhi; N Hekmat; N Baiatabadi

2005-01-01

122

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

Directory of Open Access Journals (Sweden)

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.

Labaš Milan; Krepelka František

2002-01-01

123

Determining the strength of ice with monoaxial compression  

Energy Technology Data Exchange (ETDEWEB)

The strength parameters of ice were studied with consideration of different factors such as temperature, salt content, density structure and so on in order to evaluate the loads from an ice field on the support part of an oil and gas field facility in laboratory and field conditions. The studies showed that the speeds of deformation with interaction with hydrotechnical structures has a wide range: from low speeds with a slow change in the temperature stresses of the ice cover to greater ones with seismic fluctuations.

Yevdokimov, G.N.

1983-01-01

124

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

Directory of Open Access Journals (Sweden)

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.

A. Zacoeb; K. Ishibashi

2009-01-01

125

Unified compaction curve model for tensile strength of tablets made by roller compaction and direct compression.  

UK PubMed Central (United Kingdom)

A model that describes the relationship between roller-compaction conditions and tablet strength is proposed. The model assumes that compaction is cumulative during roller compaction and subsequent granule compaction, and compact strength (ribbon and tablet) is generated irreversibly as if strength is controlled by plastic deformation of primary particles only. Roller-compaction is treated as a compaction step where the macroscopic ribbon strength is subsequently destroyed in milling. This loss in strength is irreversible and tablets compressed from the resulting granulation are weaker than those compressed by direct compression at the same compression force. Roller-compacted ribbons were produced at a range of roll forces for three formulations and subsequently milled and compacted into tablets. Once the total compaction history is taken in account, the compaction behavior of the uncompacted blends and the roller-compacted granules ultimately follow a single master compaction curve--a unified compaction curve (UCC). The model successfully described the compaction behavior of DC grade starch and formulations of lactose monohydrate with 50% or more microcrystalline cellulose, and may be more generally applicable to systems containing significant proportions of any plastically deforming material, including MCC and starch.

Farber L; Hapgood KP; Michaels JN; Fu XY; Meyer R; Johnson MA; Li F

2008-01-01

126

The effects of compressive prestress on bending strength of nuclear-grade isotropic graphite  

International Nuclear Information System (INIS)

[en] Changes in Young's modulus, electrical resistivity, and bending strength of IG-11 graphite in the directions parallel to and perpendicular to compressive prestress were measured. and a model for compressive deformation of polycrystalline graphite was proposed. The electrical resistivity decreased with increase in compressive prestress up to 0.4 ?sub(f), where ?sub(f) denotes the average compressive strength, 80 MPa, of the graphite. Then it increased abruptly with increasing the prestress to above 0.4 ?sub(f), whereas that in the direction perpendicular to the loading axis increased over the whole prestress level. Young's modulus was unchanged with increase in the prestress up to 0.4 ?sub(f) and it decreased abruptly above 0.4 ?sub(f), whereas that in the direction perpendicular to the axis decreased with increase in the prestress up to 0.4 ?sub(f) and decreased slightly above 0.4 ?sub(f). Bending strength increased with increase in the prestress up to 0.4 ?sub(f) and decreased above 0.4 ?sub(f), whereas the strength in the two directions perpendicular to the loading axis unchanged up to 0.2 ?sub(f) thereafter those decreased abruptly. A model was proposed for compressive deformation mechanism of polycrystalline graphite: In the case of low compressive stress pore and/or microcracks on the basal plane perpendicular to the loading axis in the grain would be shrunk or closed. On the basal plane parallel to the loading axis formation of microcracks would occur because of plastic flow in the direction perpendicular to the loading axis. On removal of compressive stress tensile stress is expected to be generated on account of release of elastic strain around the grains which are deformed plastically in the loading direction. The tensile stress naturally produces many cleavage microcracks on the basal plane perpendicular to loading axis. (author)

1983-01-01

127

Strength of rhenium from x-ray diffraction experiments under nonhydrostatic compression to 250 GPa  

International Nuclear Information System (INIS)

Polycrystalline rhenium in the form of a powder contained in a two-stage gasket was compressed in a diamond anvil cell. No pressure medium was used to ensure that maximum nonhydrostatic stresses that rhenium can support were produced. The pressure was increased in steps to a maximum of 250 GPa and the diffraction pattern recorded at each pressure using energy dispersive technique. The differential stress t, a measure of the compressive strength, was determined at any given pressure from the offset between the measured unit cell volume and volume computed from the pressure-volume relation under hydrostatic pressure. The data suggest that t is 2.5 GPa at a pressure of 5 GPa and increases linearly to 26 GPa at 250 GPa. The present data agree well with those obtained from the radial diffraction data to 37 GPa in an earlier study but differ significantly from the results of another study. Though comparable with the theoretical strength of ideal solids, the observed strengths are extremely large for a polycrystalline aggregate of a solid. The pure pressure effect on the strength described by the shear modulus scaling is inadequate to account for such a large increase of strength with pressure . It is suggested that the major contribution to strength comes from the strain hardening of rhenium that arises due to plastic deformat ion of the sample during nonhydrostatic compression in a diamond anvil cell.

2012-07-30

128

Risk of vertebral insufficiency fractures in relation to compressive strength predicted by quantitative computed tomography  

International Nuclear Information System (INIS)

Vertebral insufficiency fractures may result from excessive loading of normal and routine loading of osteoporotic spines. Fractures occur when the mechanical load exceeds the vertebral compressive strength, i.e., the maximum load a vertebra can tolerate. Vertebral compressive strength is determined by trabecular bone density and the size of end-plate area. Both parameters can be measured non-invasively by quanti-tative computed tomography (QCT). In 75 patients compressive strength (i.e., trabecular bone density and endplate area) of the vertebra L3 was determined using QCT. In addition, conventional radiographs of the spines were analysed for the prevalence of insufficiency fractures in each case. By relating fracture prevalence to strength, 3 fracture risk groups were found: a high-risk group with strength values of L35 kN and a fracture risk near 0 percent. Biomechanical measurements and model calculations indicate that spinal loads of 3 to 4 kN at L3/4 will be common in everyday activities. These data and the results described above suggest that spines with strength values of L3

1991-01-01

129

Strength Behavior Study of Apples under Compression Loading  

Directory of Open Access Journals (Sweden)

Full Text Available The mechanical properties data of fruits are important in the design of various handling, packing, storage and transportation systems. In this research some mechanical properties of two Iranian apple varieties (Golab Kohanz and Shafi Abadi) were analyzed in moisture contents 86% and 84% (W.b) for Golab Kohanz and Shafi Abadi varieties, respectively. Mechanical properties including rupture force and energy, deformation to rupture point, failure stress and strain, Young’s modulus (initial tangent modulus, secant modulus, tangent modulus and chard modulus), toughness and hardness were studied under compression loading using standard methods and so firmness was determined by puncture test. Average values of rupture force and energy, failure stress, failure strain, deformation, toughness and hardness were determined,57.81N, 285.88 mJ, 0.37 MPa, 31.2%, 7.77 mm,  0.06 J/cm3, 9.14 N/mm for Shafi Abadi variety, respectively. The corresponding values for Golab Kohanz variety were obtained 51.11 N, 157.51 mJ, 0.32 MPa, 23.36%, 5.6 mm, 0.04 J/cm3 and 7.79 N/mm, respectively. Initial tangent modulus, secant modulus, tangent modulus and chard modulus were obtained 0.93, 1.76, 2.27 and 2.11 MPa for Shafi Abadi variety and 0.81, 1.52, 2.08 and 2.04 MPa for Golab Kohanz variety, respectively. The firmness obtained 59.26 N for Shafi Abadi variety and corresponding value was 47.69 N for Golab Kohanz variety, respectively. According to results Shafi Abadi variety had stiffer and resisterer issue to mechanical forces than Golab Kohanz variety.

Abbas Gorji Chakespari; Ali Rajabipour; Hossein Mobli

2010-01-01

130

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 materi...

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

131

Effect of Different Cure Conditions on Compressive Strength of Concrete Having Different Properties  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This research was carried out to determine unit weights and compressive strengths for the concrete samples produced with normal aggregate obtained Erzurum province and lightweight aggregate obtained Van-Ercis province and cured under different conditions. Unit weights of concrete specimens produced ...

Bahar Kocaman; Recep Yanik; Canan Kose; Adem Ozturk

132

Influence of environmental temperatures on the concrete compressive strength: simulation of hot and cold weather conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This work has as objective to study the influence of mixing hour in the concrete properties such as workability and compressive strength in hot and cold weather conditions from an industrially applied point of view. The foremost studied variable was the concrete mixing hour, having used five mixing ...

Ortiz Lozano, José Angel; Aguado de Cea, Antonio; Agulló Fité, Luís; García Vicente, Tomàs

133

METHOD OF IMPROVING THE CRUSHING STRENGTH, IMPACT RESISTANCE AND COMPRESSIBILITY OF UREA, AND UREA COMPOSITION  

UK PubMed Central (United Kingdom)

A method of improving the crushing strength, impact resistance and the compressibility of urea granules by the addition of a compound to the molten urea, wherein the compound comprises both a polyvinyl compound and an organic molecule consisting of 1-10 carbon atoms and 1-10 polar organic groups.

BIJPOST Erik; VANMARCKE Luc; VAN DER HOEVEN John; VAN BELZEN Ruud

134

Method of improving the crushing strength, impact resistance and compressibility of urea, and urea composition  

UK PubMed Central (United Kingdom)

A method of improving the crushing strength, impact resistance and the compressibility of urea granules by the addition of a compound to the molten urea, wherein the compound comprises both a polyvinyl compound and an organic molecule consisting of 1-10 carbon atoms and 1-10 polar organic groups.

BIJPOST ERIK; VANMARCKE LUC; VAN DER HOEVEN JOHN; VAN BELZEN RUUD

135

Strength and Compressibility Characteristics of Reconstituted Organic Soil at Khulna Region of Bangladesh  

Directory of Open Access Journals (Sweden)

Full Text Available This study depicts the experimental investigations into the effect of organic content on the shear strength and compressibility parameters of reconstituted soil. To these attempts, disturbed soil samples were collected from two selected locations of Khulna region. The reconstituted soil having organic content of 5-35 % were prepared in the laboratory to mix at various proportions of inorganic and organic soil at the water content equal to 1.25 times of liquid limits of collected samples .The usual procedure of preparation of soil slurry, deposition in a mold and application of surcharge were used to reconstitute sample. The mold diameter was 152 mm and height 222 mm and applied ultimate surcharge was about 60kN/m2. In the laboratory, ASTM (2004) methods were followed for the determination of strength properties and compressibility parameters of reconstituted soil at varying organic content. Here, it can be depicted that organic content significantly influence the shear strength and compressibility parameters of reconstituted soils. Moreover, some important correlations were developed based on strength and compressibility parameters and organic content which can be expressed by equations that may be proposed to estimate the various properties of soil of Khulna region using its organic content.

Tahia Rabbee; Islam M. Rafizul

2012-01-01

136

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Uniaxial compressive strength (UCS) is the mechanical properties currently used in geotechnical works design, namely in jet grouting (JG) treatments. However, when working with this soil improvement technology, due to its inherent geological complexity and high number of variables involved, such des...

Tinoco, Joaquim; Correia, A. Gomes; Cortez, Paulo, 1971-

137

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

DEFF Research Database (Denmark)

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.

NØkkentved, Alexandros; Lundsgaard-Larsen, Christian

2005-01-01

138

Optimum Compressive Strength of Hardened Sandcrete Building Blocks with Steel Chips  

Directory of Open Access Journals (Sweden)

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.

Alohan Omoregie

2013-01-01

139

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

Directory of Open Access Journals (Sweden)

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

Akaninyene Afangide Umoh; Kolapo O. Olusola

2012-01-01

140

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

Directory of Open Access Journals (Sweden)

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).

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

2005-01-01

 
 
 
 
141

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english 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 Gillmor (more) e 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

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

2010-06-01

142

Pressure-constrained deformation and superior strength: Compressed graphite versus diamond  

Science.gov (United States)

We show by first-principles calculations that high-pressure confinement suppresses the usual ambient or low-pressure deformation modes for compressed graphite toward low-density phases under large shear deformation and promotes alternative structural evolution to high-density phases that possess enhanced shear strength surpassing that of diamond. This finding explains the puzzling experimental observation of compressed graphite cracking diamond anvil [W. L. Mao , ScienceSCIEAS0036-807510.1126/science.1089713 302, 425 (2003)] and suggests different principles for determining material strength at high pressure. It also underscores the need to go beyond empirical hardness formulas that are unable to account for changes in pressure-constrained structural evolution and their influence on strength.

Zhou, Wei; Sun, Hong; Zhang, Yi; Chen, Changfeng

2013-09-01

143

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.

1999-01-01

144

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.

2010-02-15

145

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

Directory of Open Access Journals (Sweden)

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.

Chee-Ming Chan; Liang-Pin Low

2010-01-01

146

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).

1984-01-01

147

Determination of composition of pozzolanic waste mixtures with optimized compressive strength  

Directory of Open Access Journals (Sweden)

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.

José Vidal Nardi; Dachamir Hotza

2004-01-01

148

Correlation between the uniaxial compressive strength and the point load strength index of the Pungchon limestone, Korea  

Science.gov (United States)

Recently, the use of underground openings for various purposes is expanding, particularly for the crushing and processing facilities in open-pit limestone mines. The suitability of current rockmass classification systems for limestone or dolostone is therefore one of the major concerns for field engineers. Consequently, development of the limestone mine site characterization model(LSCM) is underway through the joint efforts of some research institutes and universities in Korea. An experimental program was undertaken to investigate the correlation between rock properties, for quick adaptation of the rockmass classification system in the field. The uniaxial compressive strength(UCS) of rock material is a key property for rockmass characterization purposes and, is reasonably included in the rock mass rating(RMR). As core samples for the uniaxial compression test are not always easily obtained, indirect tests such as the point load test can be a useful alternative, and various equations between the UCS and the point load strength index(Is50) have been reported in the literature. It is generally proposed that the relationship between the Is50 and the UCS value depends on the rock types and, also on the testing conditions. This study investigates the correlation between the UCS and the Is50 of the Pungchon limestone, with a total of 48 core samples obtained from a underground limestone mine. Both uniaxial compression and point load specimens were prepared from the same segment of NX-sized rock cores. The derived equation obtained from regression analysis of two variables is UCS=26Is50, with the root-mean-square error of 13.18.

Baek, Hwanjo; Kim, Dae-Hoon; Kim, Kyoungman; Choi, Young-Sup; Kang, Sang-Soo; Kang, Jung-Seock

2013-04-01

149

Design of a gun system for in-situ compressive strength measurements  

Energy Technology Data Exchange (ETDEWEB)

This report summarizes a six-month effort aimed at developing concepts and preliminary designs of a remotely operated gun system that can be lowered into a main emplacement hole. The gun will perform penetration tests which produce in-situ compressive strength data for the geological materials surrounding a nuclear device. Such information is needed to support the modeling of the containments of nuclear explosions. 2 refs., 18 figs., 2 tabs.

Lynch, C.S.; Charest, J.A. (Dynasen, Inc., Goleta, CA (USA))

1989-11-01

150

Deformation and strength properties of three structural varieties of Carboniferous sandstone in conventional triaxial compression  

Energy Technology Data Exchange (ETDEWEB)

Three structural types of quartzitic Carboniferous sandstone from the Rybnik Coalfield were tested in conditions of conventional triaxial compression at confining pressures up to 60 MPa. The effects of confining pressure on a number of deformational and strength parameters were determined, as well as the conditions of transition from the brittle state to the ductile. The test results were analysed, taking account of the grain size of the sandstones, their porosity and mineral composition.

Kwasniewski, M.

1983-01-01

151

Tensile-compressive yield asymmetries in high strength wrought magnesium alloys  

Energy Technology Data Exchange (ETDEWEB)

Owing to magnesium's very low density (of 1.7 g/cm[sup 3]) there is potential for producing Mg alloys with higher specific strengths than those of existing aluminium alloys for applications where weight savings are at a premium. Magnesium alloys can also have greater creep resistance and superior elevated temperature specific tensile properties than those of Al. However, the hexagonal crystal structure of magnesium severely limits its available slip systems and preferred orientations can develop during working processes, slip occurring predominantly on the basal planes which leads to their alignment parallel to the direction of metal flow. As a geometric consequence of the c/a ratio of magnesium being less than ideal, twinning can theoretically only occur in compression, parallel to the basal planes, which would be expected to result in there being large asymmetries between the tensile and compressive yield stresses in textured wrought products. The compressive yield stresses in wrought magnesium alloys have been previously found in forgings to the 0.6--0.7 times those of the tensile. Such an asymmetric yield behavior, resulting in a poor compressive yield stress, would prohibit many potential applications for wrought Mg alloys. The aim of this paper is to investigate how significant the problem of yield asymmetry can be in two typical high strength wrought Mg alloys, the Mg-Y-Nd mischmetal based alloy, WE54, and the Mg-Zn-Cu based alloy, ZC71.

Ball, E.A.; Prangnell, P.B. (Univ. of Manchester (United Kingdom). Manchester Materials Science Centre UMIST, Manchester (United Kingdom))

1994-07-15

152

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

International Nuclear Information System (INIS)

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

1986-01-01

153

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

Directory of Open Access Journals (Sweden)

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

Alexandre Costa Reis BRITO; Cintia Fernandes do COUTO; Cresus Vinícius Depes de GOUVÊA

2007-01-01

154

Intermittent pneumatic compression effect on eccentric exercise-induced swelling, stiffness, and strength loss.  

UK PubMed Central (United Kingdom)

OBJECTIVE: The purpose was to determine if intermittent pneumatic compression (IPC) affects muscle swelling, stiffness, and strength loss resulting from eccentric exercise-induced injury of the elbow flexors. We hypothesized that the compression would decrease swelling and stiffness. DESIGN: Repeated measures design with a before-after trial comparison within each day. SETTING: Conducted at a university Somatic Dysfunction Laboratory. SUBJECTS: Twenty-two college women students were studied. They had not been lifting weights or otherwise participating in regular arm exercise for the 6 months before the study. They had no history of upper extremity injury or cardiovascular disease. INTERVENTIONS: Subjects performed one bout of eccentric exercise at a high load to induce elbow flexor muscle injury. Uniform IPC was applied on the day of exercise and daily for 5 days at 60mmHg, 40 seconds inflation, 20 deflation for 20 minutes. MAIN OUTCOME MEASURES: Measurements of arm circumference, stiffness, and isometric strength were recorded before exercise, then before and after IPC for 5 days after exercise. Passive muscle stiffness was measured on a device that extends the elbow stepwise and records the torque required to hold the forearm at each elbow angle. RESULTS: Circumference and stiffness increased and strength decreased during the 5 days post-exercise (p < .05). IPC significantly decreased circumference and stiffness most notably on days 2 and 3 after exercise (p < .05). The strength loss was not affected by IPC. CONCLUSION: IPC is effective in temporarily decreasing the swelling and stiffness after exercise-induced muscle injury.

Chleboun GS; Howell JN; Baker HL; Ballard TN; Graham JL; Hallman HL; Perkins LE; Schauss JH; Conatser RR

1995-08-01

155

Effect of overglazed and polished surface finishes on the compressive fracture strength of machinable ceramic materials.  

Science.gov (United States)

Controversy prevails over the effect of overglazing on the fracture strength of ceramic materials. Therefore, the effects of different surface finishes on the compressive fracture strength of machinable ceramic materials were investigated in this study. Plates prepared from four commercial brands of ceramic materials were either surface-polished or overglazed (n=10 per ceramic material for each surface finish), and bonded to flat surfaces of human dentin using a resin cement. Loads at failure were determined and statistically analyzed using two-way ANOVA and Bonferroni test. Although no statistical differences in load value were detected between polished and overglazed groups (p>0.05), the fracture load of Vita Mark II was significantly lower than those of ProCAD and IPS Empress CAD, whereas that of IPS e.max CAD was significantly higher than the latter two ceramic materials (p<0.05). It was concluded that overglazed and polished surfaces produced similar compressive fracture strengths irrespective of the machinable ceramic material tested, and that fracture strength was material-dependent. PMID:21099163

Asai, Tetsuya; Kazama, Ryunosuke; Fukushima, Masayoshi; Okiji, Takashi

2010-11-19

156

Compressive strength of radiation-induced polymer impregnated hardened cement pastes  

International Nuclear Information System (INIS)

Hardened cement paste (HPC) specimens with 0.22, 0.30, 0.40 and 0.50 W/C ratios were prepared by curing under water for 1, 3, 7 and 28 days. Impregnation was carried out under vacuum with methyl methacrylate, styrene and 60:40 wt% styrene-acrylonitrile mixture. Polymerization has been induced by ?-ray irradiation of wrapped specimens with different absorbed dose levels depending on the type of monomer used for impregnation. Considerable improvement in compressive strength has been achieved for impregnated HCP specimens over unirradiated controls. The extent of strength improvement is larger for early curing ages than for later ones. Also, impregnation with the styrene-acrylonitrile copolymer gave the best strength results, followed by polymethyl methacrylate and then polystyrene. The results are discussed in terms of the structure of HCP, the nature of the monomer and the radiation dose. (author)

1981-01-01

157

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english 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 (more) Cs 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.

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

2008-03-01

158

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

Directory of Open Access Journals (Sweden)

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.

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

2008-01-01

159

Nonhydrostatic compression of gold powder to 60 GPa in a diamond anvil cell: estimation of compressive strength from x-ray diffraction data  

International Nuclear Information System (INIS)

[en] Two gold powder samples, one with average crystallite size of ?30 nm (n-Au) and another with ?120 nm (c-Au), were compressed under nonhydrostatic conditions in a diamond anvil cell to different pressures up to ?60 GPa and the x-ray diffraction patterns recorded. The difference between the axial and radial stress components (a measure of the compressive strength) was estimated from the shifts of the diffraction lines. The maximum micro-stress in the crystallites (another measure of the compressive strength) and grain size (crystallite size) were obtained from analysis of the line-width data. The strengths obtained by the two methods agreed well and increased with increasing pressure. Over the entire pressure range, the strength of n-Au was found to be significantly higher than that of c-Au. The grain sizes of both n-Au and c-Au decreased under pressure. This decrease was much larger than expected from the compressibility effect and was found to be reversible. An equation derived from the dislocation theory that predicts the dependence of strength on the grain size and the shear modulus was used to interpret the strength data. The strength derived from the published grain size versus hardness data agreed well with the present results

2006-06-28

160

Impact of Vibration Time on Compressive Strength of Hardened Sandcrete Building Blocks  

Directory of Open Access Journals (Sweden)

Full Text Available The majority of the sandcrete blocks used in the Nigerian building industry fall short of the minimum specification standards. There is evidence to suggest a wide variation in compressive strength from one block manufacturer to another and also within block samples from a single source. This problem has been attributed to poor quality control and substandard constituent materials. Also very alarming is the ignorance surrounding the usage and engineering properties of some of the widely used fine aggregate deposits. As a way forward, this paper aims to re-establish the impact of vibration time in sandcrete block production using six fine aggregate deposits found within Benin City (Midwestern Nigeria) and their various pair combinations. Some of the basic properties like silt content, grading parameters—co-efficient of uniformity (Cu), curvature co-efficient (Cc) and the fineness modulus (Fm)—of these fine aggregates were established by laboratory means. In addition, the wet and dry compressive strength of these sandcrete blocks made from these sands were established. A total of 1,080 block samples produced under very controlled conditions were used in this investigation. It was revealed that the utility value of sand can be improved when the weaker and commonly used sands were combined with those that are better, more expensive and less frequently used at different vibration periods and ratios. Findings further revealed that sand types and the sand combination approach adopted were very significant to grading parameters and strength; at a much higher vibration time the compressive strength and durability properties were also considerably improved.

Alohan Omoregie

2012-01-01

 
 
 
 
161

Uniaxial compression test series on Bullfrog Tuff  

Energy Technology Data Exchange (ETDEWEB)

Nineteen uniaxial compressive experiments were performed on samples of the Bullfrog Member of the Crater Flat Tuff, obtained from drillhole USW-G1 at Yucca Mountain on the Nevada Test Site. The water saturated samples were deformed at a nominal strain rate of 10{sup -5} sec{sup -1}, atmospheric pressure and room temperature. Resultant unconfined compressive strengths, axial strains to failure, Young`s moduli and Poisson`s ratios ranged from 4.63 to 153. MPa, .0028 to .0058, 2.03 to 28.9 GPa and .08 to .16, respectively.

Price, R.H.; Jones, A.K.; Nimick, K.G.

1982-04-01

162

Compressive strength of autologous and allogenous bone grafts for thoracolumbar and cervical spine fusion.  

Science.gov (United States)

The selection of the bone graft type for stabilization of spinal fusion depends on availability, the clinical situation, and the desired mechanical stability. The authors determined the potential immediate postoperative compressive strength of various types of bone grafts under axial compression on a material testing machine. The fibular strut graft (5,070 +/- 3,250 N, mean +/- standard deviation [SD]) was significantly stronger (P less than 0.05) than the anterior (1,150 +/- 487 N) and posterior (667 +/- 311 N) iliac crest grafts, and the rib grafts (452 +/- 192 N). Hydroxyapatite grafts with a pore size of 200 mu were significantly stronger (P less than 0.05) than those with a pore size of 500 mu (1,420 +/- 480 N versus 338 +/- 78 N). Ethylenoxide sterilization had no significant effect on the immediate compressive strength. Bicortical and tricortical Bailey-Badgley and Cloward bone grafts also were compared. Results showed that all cervical graft types may be sufficiently strong to support sizable loads. PMID:2263975

Wittenberg, R H; Moeller, J; Shea, M; White, A A; Hayes, W C

1990-10-01

163

Compressive strength of autologous and allogenous bone grafts for thoracolumbar and cervical spine fusion.  

UK PubMed Central (United Kingdom)

The selection of the bone graft type for stabilization of spinal fusion depends on availability, the clinical situation, and the desired mechanical stability. The authors determined the potential immediate postoperative compressive strength of various types of bone grafts under axial compression on a material testing machine. The fibular strut graft (5,070 +/- 3,250 N, mean +/- standard deviation [SD]) was significantly stronger (P less than 0.05) than the anterior (1,150 +/- 487 N) and posterior (667 +/- 311 N) iliac crest grafts, and the rib grafts (452 +/- 192 N). Hydroxyapatite grafts with a pore size of 200 mu were significantly stronger (P less than 0.05) than those with a pore size of 500 mu (1,420 +/- 480 N versus 338 +/- 78 N). Ethylenoxide sterilization had no significant effect on the immediate compressive strength. Bicortical and tricortical Bailey-Badgley and Cloward bone grafts also were compared. Results showed that all cervical graft types may be sufficiently strong to support sizable loads.

Wittenberg RH; Moeller J; Shea M; White AA 3rd; Hayes WC

1990-10-01

164

Factors influencing the strength of cement fly ash base courses  

Energy Technology Data Exchange (ETDEWEB)

Fly ash is a waste produced in coal-fired thermal power stations. It has pozzolonic properties and can therefore be stabilized with either cement or lime to achieve the strength required for use as base courses in pavements. Agencies such as the Electric Power Research Institute (EPRI) have specified criteria and guidelines for the determination of the stabilizer content. This requires carrying out unconfined compression tests on stabilized fly ash specimens prepared and cured as per standard procedures. The stabilizer content is the minimum amount of the stabilizer for which the unconfined compressive strength of the specimens complies with the specified values. The actual curing conditions of the stabilized fly ash bases in the field, however, will differ from those of the laboratory specimens. This will affect the strength development of the bases, their durability, and their performance. The paper explains the details and results of a laboratory experimental program carried out to study the influence of curing conditions and other factors on the development of strength. The program comprised compaction tests and unconfined compression tests. Two Indian fly ashes and a commercial portland cement were used in the study. Six different curing conditions, including controlled and ambient conditions, were adopted. The influence of differences in the dry unit weight and water content was also investigated.

Kaniraj, S.R.; Gayathri, V. [Indian Institute of Technology, New Delhi (India). Dept. of Civil Engineering

2003-10-01

165

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

DEFF Research Database (Denmark)

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.

Ebbesen, E N; Thomsen, Jesper Skovhus

1999-01-01

166

Statistical microbuckling propagation model for compression strength prediction of fiber-reinforced composites  

Energy Technology Data Exchange (ETDEWEB)

Compressive strength prediction for a fiber-reinforced composite material still remains an unresolved topic when dealing with composites in the design process. Although significant scatter is present in the experimental data, experimental test results are the only criteria on which to base design parameters. Although significant advances have been accomplished recently by various modeling techniques, only quantitative comparison with experimental data may be realized. This quantitative comparison requires the use of a semi-empirical parameter into the model formulation, which is usually set as the fiber misalignment. By using a single value of the fiber misalignment within the composite, model predictions easily match the experimental data because of the extreme sensitivity of the model with respect to fiber misalignment. However, it is well known that thee is not a unique value of fiber misalignment for all the fibers but rather a distribution of misalignments throughout the composite. In this paper, using the complete fiber misalignment distribution, stability theory is coupled with continuous damage mechanics to generate a model for compressive strength of continuous fiber-reinforced composites. Sample results are also presented showing the correlation of the analytical model with experimentally measured strengths.

Tomblin, J.S. [Wichita State Univ., KS (United States). Dept. of Aerospace Engineering; Barbero, E.J. [West Virginia Univ., Morgantown, WV (United States). Dept. of Mechanical and Aerospace Engineering

1997-12-31

167

Dynamics of unconfined spherical flames  

CERN Multimedia

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.

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

2012-01-01

168

A theoretical model for determining the compressive strength across the width of a long pillar  

Energy Technology Data Exchange (ETDEWEB)

From the strata control point of view, pillars in a panel and pillar system of mining are used to provide support to the gate entries, and control subsidence if required. For the appropriate design of such pillars, it is necessary to evaluate their load carrying capacities and the extent of the crushed zones at the edges, since they directly influence the stability of the roof, floor and sides of the gate entries. This paper reviews the current methods for predicting pillar strengths. A two-dimensional model is proposed for determining the compressive strength across the width of a long pillar. The model can be used to determine pillar strength and the depth of the crushed (i.e. yielding) zone from the pillar edges. The values of the parameters in the model, namely the cohesion and internal friction angle of the coal seam, friction angles at the contact of the coal seam with the roof and floor are determined by matching the strengths predicted by this model with the Bieniawski pillar strength formula for pillar width to height ratios up to 5. It is found that the derived values of these parameters are quite close to the results from laboratory tests. Based on the model, a preliminary analysis of pillar stability is made. The model, presented in the paper is considered to be a first step in simulating the deformation behaviour of a coal seam being mined and the surrounding area. (author). 7 figs., 20 refs.

Zhang, M.; Bhattacharyya, A.K. [New South Wales Univ., Kensington, NSW (Australia)

1995-12-31

169

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese 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 bipartida 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 (more) 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 polytetrafluoroethylene 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 wi (more) th 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.

Silva, Cecy Martins; Dias, Katia Regina Hostilio Cervantes

2009-01-01

170

Investigation of compressive strength of concrete with slag and silica fu  

International Nuclear Information System (INIS)

[en] Without doubt, concrete has special place in construction of different types of structures, and used as one of the most important materials in construction industry. Today, with development and modernization of human knowledge in construction industry, it is possible to reach high performance concrete. Mechanical properties and durability of high performance concrete is quite better than that of conventional concrete. In present, the use of supplementary cementitious materials, mainly silica fume, fly ash and blast furnace slag has become increasingly common for reasons of economy and technical benefits imparted by these materials. The aim of present research is investigation and comparison compressive strength of concrete specimens due to variation of water to cementitious materials ratio (W/C M), silica fume and slag percent and their proportions as cement replacement. Furthermore, it is intended to determine best combination of these materials with cement in concrete (optimum percent) to reach to maximum compressive strength. In the current study, specimens were made in 0.5,0.4 and 0.3 W/C M ratio contained 0,20,35 and 50 percent of slag as cement replacement, where in each slag replacement percent, 0, 5, 10 and 15 percent of of silica fume were used as cement replacement. Results of the current study show that the combination effect of slag and silica fume replacement in concrete leads to the maximum compressive strength in concrete; also there are some optimum percents for replacement of slag and silica fume to cement to get the best results

2002-01-01

171

Steelmaking slag as aggregate for mortars: effects of particle dimension on compression strength.  

UK PubMed Central (United Kingdom)

The present paper reports on the results of some experiments obtained from the production, hydration and subsequent measurement of the mechanical properties of several mortars prepared using a commercial CII/B-LL Portland cement, steelmaking slag, superplasticizer and water. Relevant parameters for the mortar preparation are the weight ratios of cement/water, the weight ratio superplasticizer/cement and between fine and granulated coarse particles. It has been demonstrated that optimisation of such parameters leads to the production of materials with mechanical properties suitable for civil engineering applications. Moreover, materials with improved compressive strength can be prepared by the use of slag containing extensive amounts of large particles.

Faraone N; Tonello G; Furlani E; Maschio S

2009-11-01

172

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

DEFF Research Database (Denmark)

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.

Misirlis, K. Newcastle University

2009-01-01

173

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

Directory of Open Access Journals (Sweden)

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.

Ariane Bercier; Stéphane Gonçalves; Olivier Lignon; Juliette Fitremann

2010-01-01

174

Compressive strength at high temperatures of a concrete made with recycled tire textile and steel fibers  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents the results of a research work on the evaluation of the compressive strength at high temperatures of a concrete made with recycled tire steel and textile fibers. It was considered five different concrete compositions, with a water/cement ratio (W/C = 0.43), differ only in the type and amount of fibers. The compositions with smaller amounts of textile fibers were those that gave better results. The compositions with steel fibers showed a less explosive rupture showing the effectiveness of this type of fibers in the spalling and cracking control.

Santos Cristina Calmeiro; Rodrigues João Paulo C.

2013-01-01

175

Method for increasing the rate of compressive strength gain in hardenable mixtures containing fly ash  

Energy Technology Data Exchange (ETDEWEB)

The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction. The invention provides a method for increasing the rate of strength gain of a hardenable mixture containing fly ash by exposing the fly ash to an aqueous slurry of calcium oxide (lime) prior to its incorporation into the hardenable mixture. The invention further relates to such hardenable mixtures, e.g., concrete and mortar, that contain fly ash pre-reacted with calcium oxide. In particular, the fly ash is added to a slurry of calcium oxide in water, prior to incorporating the fly ash in a hardenable mixture. The hardenable mixture may be concrete or mortar. In a specific embodiment, mortar containing fly ash treated by exposure to an aqueous lime slurry are prepared and tested for compressive strength at early time points.

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

1997-01-01

176

Method for increasing the rate of compressive strength gain in hardenable mixtures containing fly ash  

Science.gov (United States)

The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction. The invention provides a method for increasing the rate of strength gain of a hardenable mixture containing fly ash by exposing the fly ash to an aqueous slurry of calcium oxide (lime) prior to its incorporation into the hardenable mixture. The invention further relates to such hardenable mixtures, e.g., concrete and mortar, that contain fly ash pre-reacted with calcium oxide. In particular, the fly ash is added to a slurry of calcium oxide in water, prior to incorporating the fly ash in a hardenable mixture. The hardenable mixture may be concrete or mortar. In a specific embodiment, mortar containing fly ash treated by exposure to an aqueous lime slurry are prepared and tested for compressive strength at early time points. 2 figs.

Liskowitz, J.W.; Wecharatana, M.; Jaturapitakkul, C.; Cerkanowicz, A.E.

1997-10-28

177

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

UK PubMed Central (United Kingdom)

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.

Shang C; Sinka IC; Jayaraman B; Pan J

2013-02-01

178

Tension-compression strength asymmetry of nanocrystalline ?-Fe2O3+fcc-Al ceramic-metal composites  

International Nuclear Information System (INIS)

The dependence on composition and loading direction of the strength of nanocrystalline ?-Fe2O3+fcc-Al composites is analyzed using molecular dynamics simulations with a recently developed multicomponent interatomic potential. Compressive strength values are found to be higher than the tensile strength values at all volume fractions of the phases. Reverse Hall-Petch relations are observed for tension and forward Hall-Petch relations are observed for compression. The observed asymmetry in behavior and the direct or reverse nature of the Hall-Petch relations are found to reflect the different manners in which pairwise electrostatic forces influence grain boundary sliding which is the primary deformation mechanism.

2006-06-05

179

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

Directory of Open Access Journals (Sweden)

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.

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

2012-01-01

180

Application of alkaliphilic biofilm-forming bacteria to improve compressive strength of cement-sand mortar.  

UK PubMed Central (United Kingdom)

The application of microorganisms in the field of construction material is rapidly increasing worldwide; however, almost all studies that were investigated were bacterial sources with mineral-producing activity and not with organic substances. The difference in the efficiency of using bacteria as an organic agent is that it could improve the durability of cement material. This study aimed to assess the use of biofilm-forming microorganisms as binding agents to increase the compressive strength of cement-sand material. We isolated 13 alkaliphilic biofilmforming bacteria (ABB) from a cement tetrapod block in the West Sea, Korea. Using 16S RNA sequence analysis, the ABB were partially identified as Bacillus algicola KNUC501 and Exiguobacterium marinum KNUC513. KNUC513 was selected for further study following analysis of pH and biofilm formation. Cement-sand mortar cubes containing KNUC513 exhibited greater compressive strength than mineral-forming bacteria (Sporosarcina pasteurii and Arthrobacter crystallopoietes KNUC403). To determine the biofilm effect, Dnase I was used to suppress the biofilm formation of KNUC513. Field emission scanning electron microscopy image revealed the direct involvement of organic-inorganic substance in cement-sand mortar.

Park SJ; Chun WY; Kim WJ; Ghim SY

2012-03-01

 
 
 
 
181

Thermal conductivity and compressive strength of expanded perlite aggregate concrete with mineral admixtures  

Energy Technology Data Exchange (ETDEWEB)

This paper studies the influence of two admixtures on expanded perlite aggregate concrete. Both silica fume and fly ash were added as replacement for cement by decreasing the cement weights in the ratios of 10, 20 and 30% by weight. The binder dosage was kept constant at 200 kg/m{sup 3} throughout this study. Superplasticizer was used 1.5% by weight of Portland cement to reduce w/c ratios. The obtained results showed that: the thermal conductivity decreased with the increase of silica fume and fly ash as replacement for portland cement up to 14 and 18%, respectively. Densities of all samples decreased from 522 to 483 kg/m{sup 3} with the increase of both admixtures. Silica fume and fly ash decreased the density of samples. The compressive strengths decreased 12, 19, 29 for 7 days, and increased 9, 13%, 4%, for 28 days due to 10, 20 and 30% silica fume, respectively. Fly ash induced to reductions in the compressive strength up to 36% at 7 days and 27% at 28 days. (Author)

Demirboga, R.; Guel, R. [Atarturk Univ., Erzurum (Turkey). Dept. of Civil Engineering

2003-12-01

182

Development of ultra-lightweight slurries with high compressive strength for use in oil wells  

Energy Technology Data Exchange (ETDEWEB)

Formations with low fracture gradients or depleted reservoirs often lead to difficult oil well cementing operations. Commonly employed cement slurries (14.0 to 15.8 lb/gal), generate an equivalent circulating density (ECD) higher than the fracture gradient and ultimately lead to formation damage, lost circulation and a decreased top of cement. Given the high price of oil, companies are investing in those and other wells that are difficult to explore. Naturally, lightweight cement slurries are used to reduce the ECD (10.0 to 14.0 lb/gal), using additives to trap water and stabilize the slurry. However, when the density reaches 11.0 lb/gal, the increase in water content may cause a change in characteristics. The focus of this study is extreme cases where it is necessary to employ ultra-lightweight cement slurries (5.5 to 10.0 lb/gal). Foamed slurries have been widely used, and the objective is to set an alternative by developing cement slurries containing uncompressible microspheres, aiming for a density of 7.5 lb/gal as well as high compressive strength. Another benefit in contrast to preparing foamed cement slurries is that there is no requirement for special equipment in the field. Routine laboratory tests such as fluid-loss control, sedimentation, thickening time, free water, compressive strength, and rheology (at room and high temperatures) were performed. Thus, it was concluded that the proposed cement slurries can be used in oil wells. (author)

Suzart, J. Walter P. [Halliburton Company, Houston, TX (United States); Farias, A.C. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil); Ribeiro, Danilo; Fernandes, Thiago; Santos, Reened [Halliburton Energy Services Aberdeen, Scotland (United Kingdom)

2008-07-01

183

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)

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).

Rolando, A.

2006-01-01

184

The unconfined quarks and gluons  

International Nuclear Information System (INIS)

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

1977-01-01

185

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

Directory of Open Access Journals (Sweden)

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

Homwuttiwong, S.; Vivatanachang, N.; Jaturapitakkul, C.

2004-01-01

186

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

International Nuclear Information System (INIS)

[en] 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)

2012-01-01

187

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

Directory of Open Access Journals (Sweden)

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

B. Bhattacharjee; Maneek Kumar; Shweta Goyal

2008-01-01

188

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

Energy Technology Data Exchange (ETDEWEB)

Lightning strikes can cause structural damage, ignite flammable materials, and produce circuit malfunctions in missiles, aircraft, and ground systems. Lightning arrestor connectors (LACs) 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 {micro}m are used in LACs 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 {micro}m diameter ZnO, TiO{sub 2} (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 {micro}m) 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.

Glass, S.J.; Newton, C.

1994-12-31

189

Effect of water curing conditions on the hydration degree and compressive strengths of fly ash-cement paste  

Energy Technology Data Exchange (ETDEWEB)

This paper explains the effect of water curing condition on compressive strengths of fly ash-cement paste by quantitative data of hydration degree. Hydration of fly ash-cement paste was estimated by Rietveld analysis and selective dissolution. The result shows that the hydration degree of belite is affected by water curing conditions, more so than that of fly ash and alite. Fly ash still continues to hydrate even without an extra, external supply of water. The strong dependence of fly ash-cement concrete on curing conditions does not come from the hydration degree of fly ash, but rather comes from the hydration degree of cement, especially belite. When the water to binder ratio is low enough, the hydration of cement plus small hydration of fly ash are considered to be enough for adequate compressive strength at the beginning. Then, compressive strength of fly ash-cement paste becomes less sensitive to the water curing period.

Pipat Termkhajornkit; Toyoharu Nawa; Kiyofumi Kurumisawa [Hokkaido University, Sapporo (Japan). Division of Environment and Resources Engineering, Graduate School of Engineering

2006-10-15

190

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

Directory of Open Access Journals (Sweden)

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.

Waldemir Rodrigues; Mariano Martínez Espinosa; Wagner Luis Polito

2004-01-01

191

Effects of material properties and speed of compression on microbial survival and tensile strength in diclofenac tablet formulations.  

UK PubMed Central (United Kingdom)

A work has been done to study the effects of material properties and compression speed on microbial survival and tensile strength in diclofenac tablet formulations. Tablets were produced from three formulations containing diclofenac and different excipients (DC, DL and DDCP). Two types of machines (Hydraulic hand press and single punch press), which compress the tablets at different speeds, were used. The compression properties of the tablets were analyzed using Heckel and Kawakita equations. A 3-dimensional plot was produced to determine the relationship between the tensile strength, compression speed and percentage survival of Bacillus subtilis in the diclofenac tablets. The mode of consolidation of diclofenac was found to depends on the excipient used in the formulation. DC deformed mainly by plastic flow with the lowest Py and Pk values. DL deformed plastically at the initial stage, followed by fragmentation at the later stage of compression, whereas DDCP deformed mainly by fragmentation with the highest Py and Pk values. The ranking of the percentage survival of B. subtilis in the formulations was DDCP > DL > DC, whereas the ranking of the tensile strength of the tablets was DDCP > DL > DC. Tablets produced on a hydraulic hand press with a lower compression speed had a lower percentage survival of microbial contaminants than those produced on a single punch press, which compressed the tablets at a much higher speed. The mode of consolidation of the materials and the speed at which tablet compression is carried out have effects on both the tensile strength of the tablets and the extent of destruction of microbial contaminants in diclofenac tablet formulations.

Ayorinde JO; Itiola OA; Odeniyi MA

2013-03-01

192

Ultimate strength of a square plate with a longitudinal/transverse dent under axial compression  

Energy Technology Data Exchange (ETDEWEB)

Thin shell structures are efficient structures because of their high load-carrying capacity and small weight. Thin plates are one of the common structural elements. Their load-carrying capacity mainly depends on their buckling behavior, which is in turn affected by the imperfections present in them. Dent is one of the common geometrical imperfections in thin shell structures, which may be formed in the plate as an impact of sharp objects, among other reasons. Using ANSYS nonlinear FEA, the present work conducts a numerical study of the effect of various dent parameters on the ultimate strength of a thin plate, with a longitudinal or a transverse dent located centrally on the plate, under uniaxial compressive loading with simply supported boundary conditions.

Raviprakash, A. V.; Prabu, B.; Alagumurthi, N. [Pondicherry Engineering College, Puducherry (India)

2011-09-15

193

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

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Full Text Available This study was carried out to design and fabricate a cost effective and efficient compression strength tester to carter for the needs of stakeholders in the blocks and bricks industries. In carrying out the project work a thorough study of the foreign testers and the requirements of the Nigerian industrial standards, NIS 87:2000 and NIS 74:1976 for blocks and clay bricks respectively was done. Design drawings and calculations were established and the machine was fabricated with well selected materials and components all sourced locally. The performance of the fabricated machine was finally evaluated against a standard foreign machine in the Standards Organisation of Nigeria using statistical methods and the result showed that the locally fabricated machine is 97% effective.

Abdulkadir Baba HASSAN; Yahaya Ahmed BUKAR

2009-01-01

194

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english 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 superior vibration damping characteristics and reduced processing cycle over cast iron. The investigated processing variables were epoxy content and particle size and the mechanical c (more) haracterization 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.

Piratelli-Filho, Antonio; Shimabukuro, Frank

2008-12-01

195

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

Directory of Open Access Journals (Sweden)

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 superior 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.

Antonio Piratelli-Filho; Frank Shimabukuro

2008-01-01

196

Compressive Strength and Water Permeability Performance of Micronised Biomass Silica Concrete  

Directory of Open Access Journals (Sweden)

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.

S.H. Adnan; I. Abdul Rahman; Y.L. Lee; H. Yusof

2009-01-01

197

Effect of microwave disinfection on compressive and tensile strengths of dental stones.  

UK PubMed Central (United Kingdom)

BACKGROUND AND AIMS: Although microwave irradiation has been used for disinfection of dental stone casts, there are concerns regarding mechanical damage to casts during the process. The aim of this study was to evaluate the effect of microwave irradiation on the compressive strength (CS) and diametral tensile strength (DTS) of stone casts. MATERIALS AND METHODS: In this in vitro study, 80 cylindrical type III and IV stone models (20 × 40 mm) were prepared and divided into 8 groups of 10. The DTS and CS of the specimens were measured by a mechanical testing machine at a crosshead speed of 0.5 cm/min after 7 times of frequent wetting, irradiating at an energy level of 600 W for 3 minutes and cooling. Data were analyzed by Student's t-test. RESULTS: Microwave irradiation significantly increased DTS of type III and IV to 5.23 ± 0.64 and 8.17 ± 0.94, respectively (P < 0.01). CONCLUSION: According to the results, microwave disinfection increases DTS of type III and IV stone casts without any effects on their CS.

Robati Anaraki M; Moslehifard E; Aminifar S; Ghanati H

2013-01-01

198

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

Scientific Electronic Library Online (English)

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

Kahraman, S; Fener, M; Kozman, E

2012-05-01

199

Strength improvement in transformation toughened ceramics using compressive residual surface stresses  

International Nuclear Information System (INIS)

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

1987-01-01

200

Comparison of low-strength compression stockings with bandages for the treatment of recalcitrant venous ulcers.  

UK PubMed Central (United Kingdom)

OBJECTIVE: To compare the proportion and rate of healing, pain, and quality of life of low-strength medical compression stockings (MCS) with traditional bandages applied for the treatment of recalcitrant venous leg ulcers. METHODS: A single-center, randomized, open-label study was performed with consecutive patients. Sigvaris prototype MCS providing 15 mm Hg-25 mm Hg at the ankle were compared with multi-layer short-stretch bandages. In both groups, pads were placed above incompetent perforating veins in the ulcer area. The initial static pressure between the dressing-covered ulcer and the pad was 29 mm Hg and 49 mm Hg with MCS and bandages, respectively. Dynamic pressure measurements showed no difference. Compression was maintained day and night and changed every week. The primary endpoint was healing within 90 days. Secondary endpoints were healing within 180 days, time to healing, pain (weekly Likert scales), and monthly quality of life (ChronIc Venous Insufficiency Quality of Life [CIVIQ] questionnaire). RESULTS: Of 74 patients screened, 60 fulfilled the selection criteria and 55 completed the study; 28 in the MCS and 27 in the bandage group. Ulcers were recurrent (48%), long lasting (mean, 27 months), and large (mean, 13 cm2). All but one patient had deep venous reflux and/or incompetent perforating veins in addition to trunk varices. Characteristics of patients and ulcers were evenly distributed (exception: more edema in the MCS group; P = .019). Healing within 90 days was observed in 36% with MCS and in 48% with bandages (P = .350). Healing within 180 days was documented in 50% with MCS and in 67% with bandages (P = .210). Time to healing was identical. Pain scored 44 and 46 initially (on a scale in which 100 referred to maximum and 0 to no pain) and decreased within the first week to 20 and 28 in the MCS and bandage groups, respectively (P < .001 vs .010). Quality of life showed no difference between the treatment groups. In both groups, pain at 90 days had decreased by half, independent of completion of healing. Physical, social, and psychic impairment improved significantly in patients with healed ulcers only. CONCLUSION: Our study illustrates the difficulty of bringing large and long-standing venous ulcers to heal. The effect of compression with MCS was not different from that of compression with bandages. Both treatments alleviated pain promptly. Quality of life was improved only in patients whose ulcers had healed.

Brizzio E; Amsler F; Lun B; Blättler W

2010-02-01

 
 
 
 
201

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

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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.

Borvorn Israngkura Na Ayudhya

2011-01-01

202

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.

2002-10-15

203

Improvement of the compressive strength of a cuttlefish bone-derived porous hydroxyapatite scaffold via polycaprolactone coating.  

Science.gov (United States)

Cuttlefish bones (CBs) have emerged as attractive biomaterials because of their porous structure and components that can be converted into hydroxyapatite (HAp) via a hydrothermal reaction. However, their brittleness and low strength restrict their application in bone tissue engineering. Therefore, to improve the compressive strength of the scaffold following hydrothermal conversion to a HAp form of CB (CB-HAp), the scaffold was coated using a polycaprolactone (PCL) polymer at various concentrations. In this study, raw CB was successfully converted into HAp via a hydrothermal reaction. We then evaluated their surface properties and composition by scanning electron microscopy and X-ray diffraction analysis. The CB-HAp coated with PCL showed improved compressive performance and retained a microporous structure. The compressive strength was significantly increased upon coating with 5 and 10% PCL, by 2.09- and 3.30-fold, respectively, as compared with uncoated CB-HAp. However, coating with 10% PCL resulted in a reduction in porosity. Furthermore, an in vitro biological evaluation demonstrated that MG-63 cells adhered well, proliferated and were able to be differentiated on the PCL-coated CB-HAp scaffold, which was noncytotoxic. These results suggest that a simple coating method is useful to improve the compressive strength of CB-HAp for bone tissue engineering applications. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 101B: 1302-1309, 2013. PMID:23661509

Kim, Beom-Su; Kang, Hyo Jin; Lee, Jun

2013-05-10

204

Unconfined linear flow to a horizontal well.  

UK PubMed Central (United Kingdom)

The validity of a previously proposed but untested modification to equations for flow to a horizontal well is assessed using a specially developed finite-difference model. This modification extends confined flow equations to allow the head in the well and the saturated depth at the well to be estimated in unconfined conditions. The study is limited to the case of two-dimensional flow with no flow in the direction parallel to the line of the well. The results show that the modified equations for both a finite unconfined aquifer and, by inference, an infinite unconfined aquifer are adequately accurate for practical application.

Wojciech Kawecki M; Al-Subaikhy HN

2005-07-01

205

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english 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 randomly 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. Buckl (more) ing strength, post-buckling behaviour, ultimate strength and post-ultimate behaviour of the models are investigated as results of both-sides random corrosion.

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

2010-09-01

206

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english 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 variat (more) ion 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.

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

2012-08-01

207

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 carried. Almost all specimens of M30 & 40 grades of RHA concrete and normal concrete exhibited zero strength at a temperature of 1000°C. It shows that concrete cannot withstand a temperature of 1000°C and above. It was also concluded that compressive strength of RHA concrete was higher at °emperature below 500°C and decreases above 500°C.

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

2013-01-01

208

Influence of carbonation on the compressive strength and thermal conductivity of autoclaved aerated concrete masonry units; Zum Einfluss der Carbonatisierung auf die Druckfestigkeit und Waermeleitfaehigkeit von Porenbetonplansteinen  

Energy Technology Data Exchange (ETDEWEB)

Within a limited research project the influence of carbonation on the compressive strength and the thermal conductivity of commercially available autoclaved aerated concrete masonry units were investigated. Therefor samples have been cut out of complete masonry units and stored at different climate conditions. Subsequent the compressive strength and the thermal conductivity were determined and compared with the declared values of the manufacturers.

Stegmaier, Michael [Materialpruefungsanstalt Universitaet Stuttgart (Otto-Graf-Institut), Abteilung Mineralische Baustoffe, Stuttgart (Germany)

2011-10-15

209

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

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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.

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

2010-01-01

210

Biocements based on a mixture of TCP-PHA with improved compressive strength  

UK PubMed Central (United Kingdom)

Powder mixture used for bone cements comprises tricalcium phosphate, a cation-defined precipitated hydroxyapatite and a further phosphorus-containing inorganic compound(s) Powder mixture with a high compression strength comprises tricalcium phosphate (TCP), 30-70% of which being of particle size 0.1-7 microns and 10-60% being 40-100 microns in size, precipitated hydroxyapatite (PHA), comprising a cation-defined HA, and a further phosphorus-containing inorganic compound(s). Powder mixture comprises tricalcium phosphate (TCP), 30-70% of which being of particle size 0.1-7 microns and 10-60% being 40-100 microns in size, precipitated hydroxyapatite (PHA), comprising a cation-defined HA of formula (I), and a further phosphorus-containing inorganic compound(s) (II). Ca8.75V(Ca)1.25((HPO4)5.5-x(CO3)0.5)(OH)xV(OH)2-x (I) x = 0-2.

Wenz Robert Dr.; Driessens Ferdinand Prof.

211

Evaluation of Shear Strength and Cone Penetration Resistance Behavior of Tropical Silt Loam Soil under Uni-Axial Compression  

Directory of Open Access Journals (Sweden)

Full Text Available Laboratory investigations were conducted to study strength characteristics of silt loam soil of Ilorin, Kwara State, Nigeria, under uni-axial compression tests. The main objective of this study was to evaluate the effects of applied pressure and moisture content on strength indices such as bulk density, penetration resistance and shear strength of the soil and to develop relationships between the strength indices for predictive purposes necessary in soil management. The compression was carried out at different moisture contents determined according to the consistency limits of the soil. The applied pressure ranged from 75 to 600 kPa. Values of bulk density, penetration resistance and shear strength increased with increase in moisture content up to peak values after which the values decreased with further increase in moisture content. Regression models were used to describe the trends in the results for the soil. Results also showed that bulk density and soil strength normally regarded as indicators of soil quality are affected by moisture content and applied pressure and that these properties can be predicted using the models generated from the study.

Seth I. Manuwa; Omolola C. Olaiya

2012-01-01

212

An experimental study of the strength of composite-reinforced beams and bars in transverse bending and axial compression  

Energy Technology Data Exchange (ETDEWEB)

Experimental data are presented on the strength and fracture characteristics of composite-reinforced beams and short and long bars of aluminum alloys in transverse bending and axial compression. The reinforcement materials include carbon and boron composites with a polymer matrix as well as boron/aluminum. The results demonstrate the effectiveness of using structures reinforced by unidirectional composites. In aerospace applications, the use of composite reinforcements can significantly reduce the weight of structures. 6 refs.

Dzhankhotov, S.O.; Panfilov, B.V.; Spichkova, L.E.

1989-01-01

213

Mechanical properties of the Ca exchanged and Ca bentonite. Swelling pressure, hydraulic conductivity, compressive strength and elastic modulus  

Energy Technology Data Exchange (ETDEWEB)

The buffer material component of the engineered barrier system of the radioactive waste repository, functions to maintain low groundwater flow and mechanical stability in the repository for long periods of time. If Na bentonite is used as a buffer material, it is possible that the Na bentonite will change to Ca bentonite by exposure to Ca ions derived from calcite in the ground water. In the TRU waste disposal repository if cementitious materials are used, the change from Na to Ca bentonite may be almost immediate. Therefore it is important to investigate the mechanical properties of Ca bentonite as part of TRU waste disposal research and development. This paper reports the results of swelling pressure, water permeability and compressive strength tests for compacted Ca bentonite and for bentonite which has undergone Na-Ca exchange. Maximum and equilibrium swelling pressure tests and water permeability tests were performed. Compressive strength tests produced compressive strength and elastic modulus values for unsaturated compacted bentonite. The results of these test correlate with the dry density and sand mixing contents of bentonite. Finally, the relative properties of Ca, Na and Ca-Na exchanged bentonite were compared. It is clear that the maximum and equilibrium swelling pressures and hydraulic conductivity of compacted Ca-Na exchanged bentonite are the same as Na bentonite when both their dry density was about 1.8 g/cm{sup 3}. The compressive strength and elastic modulus of compacted Ca-Na exchanged bentonite are a little higher than Na bentonite. When compacted, results are the same for either Ca bentonite (dry density 1.4 g/cm{sup 3}) or Ca-Na exchanged bentonite compared with Na bentonite (dry density 1.6-1.8 g/cm{sup 3}). (author)

Maeda, Munehiro [Kobori Research Complex INC. (Japan); Tanai, Kenji; Ito, Masaru; Mihara, Morihiro; Tanaka, Masuhiro

1998-03-01

214

Compressive strength of CFRP-laminated composites with impact damage; Shogeki sonsho wo uketa CFRP sekisoban no asshuku kyodo ni tsuite  

Energy Technology Data Exchange (ETDEWEB)

This report describes the influence of impact damage on the compressive strength of CFRP-laminated panels. The panels with impact damage are subjected to compressive loads for evaluation of their residual strength. The interlaminar failure of the panels with impact damage is investigated using ultrasonic inspection techniques and optical microscopy. The test results are summarized as follows. The area of delamination on the reverse surface is larger than that on the impact surface. The shape of the area is an ellipse whose major axis corresponds to the fiber direction of the surface laminate. In addition, the area size is approximately proportional to the impact energy. The compressive residual strength decreased with increasing impact damage. The compressive residual strength with impact damage of 70J/cm is reduced to about 75% of the strength without impact damage. 11 refs., 23 figs., 1 tab.

Nohara, T.; Matsushita, M. [National Aerospace Laboratory, Tokyo (Japan)

1995-02-01

215

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

Directory of Open Access Journals (Sweden)

Full Text Available Normal 0 false false false MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} 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.  

Mohamed Osmani; Asokan Pappu

2010-01-01

216

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

Science.gov (United States)

Statement of Problem: Acrylic resins have been in the center stage of Prosthodontics for more than half a century. The flexural fatigue failure of denture base materials is the primary mode of clinical failure. Hence there is a need for superior physical and mechanical properties. Purpose: This in vitro study compared the transverse strength of specimens of thermopressed injection-molded and conventional compression-molded polymethylmethacrylate polymers and examined the morphology and microstructure of fractured acrylic specimens. Materials and Methods: The following denture base resins were examined: Brecrystal (Thermopressed injection-molded, modified polymethylmethacrylate) and Pyrax (compression molded, control group). Specimens of each material were tested according to the American Society for Testing and Materials standard D790-03 for flexural strength testing of reinforced plastics and subsequently examined under SEM. The data was analyzed with Student unpaired t test. Results: Flexural strength of Brecrystal (82.08 ± 1.27 MPa) was significantly higher than Pyrax (72.76 ± 0.97 MPa). The tested denture base materials fulfilled the requirements regarding flexural strength (>65 MPa). The scanning electron microscopy image of Brecrystal revealed a ductile fracture with crazing. The fracture pattern of control group specimens exhibited poorly defined crystallographic planes with a high degree of disorganization. Conclusion: Flexural strength of Brecrystal was significantly higher than the control group. Brecrystal showed a higher mean transverse strength value of 82.08 ± 1.27 MPa and a more homogenous pattern at microscopic level. Based on flexural strength properties and handling characteristics, Brecrystal may prove to be an useful alternative to conventional denture base resins. PMID:24025885

Raut, Anjana; Rao, Polsani Laxman; Vikas, Bvj; Ravindranath, T; Paradkar, Archana; Malakondaiah, G

217

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

UK PubMed Central (United Kingdom)

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

Raut A; Rao PL; Vikas B; Ravindranath T; Paradkar A; Malakondaiah G

2013-05-01

218

Effect of moisture content on the mechanical properties of coal measure rocks (II): variations in uniaxial compression strength due to hygroscopicity, water absorptivity and moisture content  

Energy Technology Data Exchange (ETDEWEB)

An experimental study was made of the effect of water absorptivity and moisture content on the uniaxial compression strength of coal measure rocks. The aim of these investigations was to gather data relevant to the maintenance of roadways in coal mines and to the optimum control of working faces. The relation between moisture content, absorption swelling and uniaxial compression strength was clarified for rock from several Kyushu coal mines. These results suggest that there is a correlation between weight percentage water content and equivalent montmorillonite content, and that increasing water content causes a drop in uniaxial compression strength. 5 references.

Ichinose, M.; Uchino, K.; Park, H.M.

1983-01-01

219

Theory of DDT in unconfined flames  

CERN Multimedia

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.

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

1996-01-01

220

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

Science.gov (United States)

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.

Li, Wangnan; Cai, Hongneng; Li, Chao

2013-01-01

 
 
 
 
221

Effect of early mobilisation on grip strength, pinch strength and work of hand muscles in cases of closed diaphyseal fracture radius-ulna treated with dynamic compression plating.  

Directory of Open Access Journals (Sweden)

Full Text Available AIMS: The purpose of the study was to objectively determine the effects of early mobilisation in terms of grip strength and work of hand muscles in cases of closed diaphyseal fracture radius - ulna treated with dynamic compression plating. SUBJECTS AND METHODS: Fifty normal subjects and Twenty-one patients, (Eleven patients treated with early active and resistive goal directed mobilisation and Ten control group) were assessed for pinch strength and grip strength on Pinch Dynamometer and Jamar Dynamometer and work of hand muscles on Ergograph. Standardised positions of the equipments and patients were maintained throughout the study. RESULTS: Results showed highly significant reduction in performance in patients treated with early mobilisation as compared to normal subjects in their first assessment (Fourth week post operatively). These patients showed significant improvement in successive assessments (sixth & eighth post operative week) on exercising in between these assessments. CONCLUSIONS: There are significant effects on grip strength and work of hand muscles in patients treated with that early active and resistive goal directed mobilisation.

Solanki P; Mulgaonkar K; Rao S

2000-01-01

222

Effect of early mobilisation on grip strength, pinch strength and work of hand muscles in cases of closed diaphyseal fracture radius-ulna treated with dynamic compression plating.  

UK PubMed Central (United Kingdom)

AIMS: The purpose of the study was to objectively determine the effects of early mobilisation in terms of grip strength and work of hand muscles in cases of closed diaphyseal fracture radius - ulna treated with dynamic compression plating. SUBJECTS AND METHODS: Fifty normal subjects and Twenty-one patients, (Eleven patients treated with early active and resistive goal directed mobilisation and Ten control group) were assessed for pinch strength and grip strength on Pinch Dynamometer and Jamar Dynamometer and work of hand muscles on Ergograph. Standardised positions of the equipments and patients were maintained throughout the study. RESULTS: Results showed highly significant reduction in performance in patients treated with early mobilisation as compared to normal subjects in their first assessment (Fourth week post operatively). These patients showed significant improvement in successive assessments (sixth & eighth post operative week) on exercising in between these assessments. CONCLUSIONS: There are significant effects on grip strength and work of hand muscles in patients treated with that early active and resistive goal directed mobilisation.

Solanki PV; Mulgaonkar KP; Rao SA

2000-04-01

223

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

Energy Technology Data Exchange (ETDEWEB)

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.

Pinkerton, G.W.

1993-12-31

224

Compression Strength Testing for Automotive Brake Pads Used in Earthquake Energy Dampers  

Directory of Open Access Journals (Sweden)

Full Text Available In order to calibrate a friction damper which uses automotive brake pads it is necessary to determine the compression behaviour of the friction material. This paper summarizes the experimental results obtained for a set of automotive brake pads made in Romania. These results are useful in order to determine the slip load level in a seismic energy dissipation mechanism which uses this type of friction pads. The paper presents the experimental set up and the compression behaviour curves obtained for a set of four commercial brake pads. The testing was performed by the author as a part of his research work, using a hydraulic compression press.

Drago? Voiculescu

2010-01-01

225

Study on the testing method and procedures for engineering properties of NPP site : compressive strength and rock mass deformation modulus  

Energy Technology Data Exchange (ETDEWEB)

This study have been carried out for attempting to develop the minimum requirements of testing methods and procedures for determining engineering properties for foundation bedrock at NPP site. As a first phase study, for the compressive strength and deformation modulus of rock important to the safety evaluation of the bearing capacity and settlement of the foundation, the testing methods and procedures for determining the two characteristic values were reviewed and comparison between each value of the sites under studying was carried out. The data originated from Wolsong 1 spent fuel dry storage site and the NPP sites of Yonggwang 3 {center_dot} 4, Wolsong 2{center_dot}3{center_dot}4, and Ulchin 3{center_dot}4. Also, re-evaluation was made for the data excluded from original analysis, and especially re-calculation of rock mass deformation modulus of Wolsong unit 2 was conducted by using the settlement data. The analysis result show that the uniaxial compressive and point load tests had been conducted for compressive strength and the jack test, hydraulic pressure meter test, and correlation methods using RQD, RMR, and velocity index were conducted for rock mass deformation modulus. It is also found that there was a tendency to decide characteristic values by selecting the lower value among various test results rather than considering the credibility of the test results.

Shim, T. M.; Lee, S. K.; Noh, M. H.; Lee, H. W. [KINS, Taejon (Korea, Republic of)

2001-05-01

226

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)

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.

Roman Popil

2012-01-01

227

Research into the utilization of coal ash as a civil engineering material (IX): the density, fluidity and strength of coal ash/volcanic ash/cement slurries  

Energy Technology Data Exchange (ETDEWEB)

The authors report tests of the effect of the addition of sandy soil to coal ash slurries. Specifically, volcanic ash, cement and sea-water were kneaded with wet fly ash and measurements made of slump and unconfined compression strength (qu). The following findings are reported. 1) Qu decreased with increasing void ratio. 2) Qu increased with increasing proportion of coal ash in the slurry. 3) The various constituent materials began to separate when more than 60% volcanic ash was added. 4) To be a satisfactory material for incorporation into soil structure, slurries of the sort under test should have a wet density of 1.7 g/cm/sup 3/, an unconfined compression strength of 3 kgf/cm/sup 2/, and a slump value of 12 cm. 3 references, 6 figures, 1 table.

Horiuchi, S.; Onoue, A.; Yamada, S.

1986-01-01

228

A summary of the strength and modulus of ice samples from multi-year pressure ridges  

Energy Technology Data Exchange (ETDEWEB)

Over two hundred unconfined compression tests were performed on vertical ice samples obtained from 10 multi-yr pressure ridges in the Beaufort Sea. The tests were performed on a closed-loop electrohydraulic testing machine at two strain rates (10/sup -5/ and 10/sup -3/ s/sup -1/) and two temperatures (-20/sup 0/ and -5/sup 0/C). This paper summarizes the sample preparation and testing techniques used in the investigation and presents data on the compressive strength and initial tangent modulus of the ice.

Cox, G.F.N.; Mellor, M.; Richter, J.A.; Weeks, W.F.

1985-03-01

229

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish 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 (more) 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 requires high-quality core samples having regular geometry. Empirical equations were thus proposed for predicting UCS as a function of rocks' index properties. Analytical hierarch (more) y 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

Hakan, Ersoy; Kanik, Derya

2012-06-01

230

Evaluation of Soil Compaction Strength (Pre-Compaction Stress) Using Plate Sinkage and Uniaxial Confined Compression Tests  

Directory of Open Access Journals (Sweden)

Full Text Available For prevention of soil compaction, knowledge of allowable compression stress limit (compaction strength) in soil is important. Pre-compaction stress ( ?pc) was introduced as soil compaction strength and often used as a criterion for evaluation of soil susceptibility to compaction. In this research, pre-compaction stress was measured for a sandy loam soil with plate sinkage (PST) and confined compression (CCT) tests. To prepare soil samples with different initial compactness, two soil water contents (17 and 19%db) and six pre-loading stresses (0, 25, 50, 100, 150 and 200 kPa) were used. The effects of soil water content and pre-loading stress on estimated pre-compaction stress were studied using a factorial experiment in a completely randomized design with three replications. The ?pcvalues were significantly influenced by loading combination and soil water content. For PST, pre-load increase and higher soil water content resulted in higher and lower values of ?pc , respectively. However, predicted ?pc value increased with higher soil water content for CCT. The results also showed that the ?pc predicted with PST was accurate, whereas the values obtained with CCT were 4.5 (at 17 %db) and 8.5 (at 19 %db) times higher than the applied pre-loads. Overall, the findings indicated that ?pc prediction depends on the compression test, and PST could be a suitable method for soil pre-compaction stress (compaction strength) determination in sustainable soil management, i.e., soil trafficability and tillage. The PST method is also suitable to assess the effect of managing factors on pre-compaction stress.

M. Tahmasbi; A. Hemmat; M. Vafaian; M. R. Masaddeghi

2008-01-01

231

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish 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 o (more) xígeno 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 materials. Mixes of the combination of granulated ground blast furnace slag, basic oxygen slag, cement kiln dust and plasterboard gypsum were used for optimising the binders, acc (more) ording 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.

Lizarazo Marriaga, Juan Manuel; Claisse, Peter

2009-08-01

232

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

Directory of Open Access Journals (Sweden)

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

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

2013-01-01

233

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Tinic, C.; Brühwiler, E.

234

Mechanical behavior and dynamic failure of high-strength ultrafine grained tungsten under uniaxial compression  

International Nuclear Information System (INIS)

We have systematically investigated the quasi-static and dynamic mechanical behavior (especially dynamic failure) of ultra-fine grained (UFG) tungsten (W) under uniaxial compression. The starting material is of commercial purity and large grain size. We utilized severe plastic deformation to achieve the ultrafine microstructure characterized by grains and subgrains with sizes of ?500 nm, as identified by transmission electron microscopy. Results of quasi-static compression show that the UFG W behaves in an elastic-nearly perfect plastic manner (i.e., vanishing strain hardening), with its flow stress approaching 2 GPa, close to twice that of conventional coarse grain W. Post-mortem examinations of the quasi-statically loaded samples show no evidence of cracking, in sharp contrast to the behavior of conventional W (where axial cracking is usually observed). Under uniaxial dynamic compression (strain rate ?103 s-1), the true stress-true strain curves of the UFG W exhibit significant flow softening, and the peak stress is ?3 GPa. Furthermore, the strain rate sensitivity of the UFG W is reduced to half the value of the conventional W. Both in situ high-speed photography and post-mortem examinations reveal shear localization and as a consequence, cracking of the UFG W under dynamic uniaxial compression. These observations are consistent with recent observations on other body-centered cubic metals with nanocrystalline or ultrafine microstructures. The experimental results are discussed using existing models for adiabatic shear localization in metals.

2006-01-01

235

Toroidal, compression, and vortical dipole strengths in $^{144-154}$Sm: Skyrme-RPA exploration of deformation effect  

CERN Multimedia

A comparative analysis of toroidal, compressional and vortical dipole strengths in the spherical $^{144}$Sm and the deformed $^{154}$Sm is performed within the random-phase-approximation using a set of different Skyrme forces. Isoscalar (T=0), isovector (T=1), and electromagnetic excitation channels are considered. The role of the nuclear convection $j_{\\text{con}}$ and magnetization $j_{\\text{mag}}$ currents is inspected. It is shown that the deformation leads to an appreciable redistribution of the strengths and causes a spectacular deformation splitting (exceeding 5 MeV) of the isoscalar compressional mode. In $^{154}$Sm, the $\\mu$=0 and $\\mu$=1 branches of the mode form well separated resonances. When stepping from $^{144}$Sm to $^{154}$Sm, we observe an increase of the toroidal, compression and vortical contributions in the low-energy region (often called pygmy resonance). The strength in this region seems to be an overlap of various excitation modes. The energy centroids of the strengths depend signific...

Kvasil, J; Kleinig, W; Bozik, D; Reinhard, P -G; Iudice, N Lo

2013-01-01

236

The Strength of Single Crystal Copper under Uniaxial Shock Compression at Mbar pressures  

Energy Technology Data Exchange (ETDEWEB)

In situ x-ray diffraction has been used to measure the shear strain (and thus strength) of single crystal copper shocked to Mbar pressures along the [001] and [111] axes. These direct shear strain measurements indicate shear strengths at these ultra-high strain rates (of order 10{sup 9} s{sup -1}) of a few GPa, which are both broadly in agreement with the extrapolation of lower strain-rate data and with non-equilibrium molecular dynamics simulations.

Murphy, W; Higginbotham, A; Kimminau, G; Barbrel, B; Bringa, E; Hawreliak, J; Koenig, M; McBarron, W; Meyers, M; Nagler, B; Ozaki, N; Park, N; Remington, B; Rothman, S; Vinko, S M; Whitcher, T; Wark, J

2009-05-21

237

The Strength of Single Crystal Copper under Uniaxial Shock Compression at Mbar pressures  

International Nuclear Information System (INIS)

[en] In situ x-ray diffraction has been used to measure the shear strain (and thus strength) of single crystal copper shocked to Mbar pressures along the (001) and (111) axes. These direct shear strain measurements indicate shear strengths at these ultra-high strain rates (of order 109 s-1) of a few GPa, which are both broadly in agreement with the extrapolation of lower strain-rate data and with non-equilibrium molecular dynamics simulations.

2010-02-17

238

An extrapolation method for compressive strength prediction of hydraulic cement products  

Energy Technology Data Exchange (ETDEWEB)

The basis for the AMEBA Method is presented. A strength-time function is used to extrapolate the predicted cementitious material strength for a late (ALTA) age, based on two earlier age strengths--medium (MEDIA) and low (BAIXA) ages. The experimental basis for the method is data from the IPT-Brazil laboratory and the field, including a long-term study on concrete, research on limestone, slag, and fly-ash additions, and quality control data from a cement factory, a shotcrete tunnel lining, and a grout for structural repair. The method applicability was also verified for high-performance concrete with silica fume. The formula for predicting late age (e.g., 28 days) strength, for a given set of involved ages (e.g., 28,7, and 2 days) is normally a function only of the two earlier ages` (e.g., 7 and 2 days) strengths. This equation has been shown to be independent on materials variations, including cement brand, and is easy to use also graphically. Using the AMEBA method, and only needing to know the type of cement used, it has been possible to predict strengths satisfactorily, even without the preliminary tests which are required in other methods.

Siqueira Tango, C.E. de [IPT-Technological Research Inst., Sao Paulo (Brazil)

1998-07-01

239

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

Directory of Open Access Journals (Sweden)

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.

Seyed Abolhassan Naeini; Masoud Ghorbanalizadeh

2010-01-01

240

Effect of fabric on the strength of granular materials in biaxial compression  

Science.gov (United States)

An equation is presented to unify the strength of granular materials in the presence of inherent and induced anisotropy. By applying a Fourier series that was developed to model fabric, direct incorporation of the fabric in the strength of granular materials is done. Based on the experimental data, in the presence of the same density, fabric is a main parameter to determine the shear strength of the granular materials. The difference between (?1/?2)f for the specimens have a same density (or void ratio), is attributed to this equation. Applying this equation the different trends between the samples with different bedding angles can be simulated. Verifying with the experimental data reveals the validity of this formulation.

Shaverdi, Homayoun; Taha, Mohd Raihan; Kalantary, Farzin

2013-06-01

 
 
 
 
241

Influence ot the curing temperatures on the evolution of the compression strength of concretes made with different typer of cements  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper we present the results obtained in the studies carried out on evolution of the compressive strength of identical concretes made with different types of cements based on the spanish standard UNE 80 301 when they are subjected to critical temperatures (5 °C and 35 °C), compared with the same concretes cured under normalysed conditions. The number of the different cements used was eight. The behaviour of the concretes was analysed through the results of the compression strengths at 3, 7, 14, 28 and 90 days, determining the grades of relative maturity of these concretes subjerted to the different temperatures. From the work it can be concluded that these concretes made of different cements fulfill with their forecasted strength at 28 days.En este trabajo se presentan los resultados obtenidos en un estudio sobre la evolución de las resistencias a compresión de hormigones idénticos confeccionados con distintos tipos de cementos de la norma española UNE 80 301 cuando son sometidos a temperaturas extremas de curado (5 °C y 35 °C), comparándola con la de los mismos hormigones curados en condiciones normalizadas a 2QP C. El número de cementos distintos empleados ha sido de ocho. El comportamiento de estos hormigones se ha analizado a través de los resultados de las resistencias a compresión a 3, 7, 14, 28 y 90 días, determinándose los grados de madurez relativos de los hormigones sometidos a las diferentes temperaturas. Del trabajo se concluye que los hormigones en los que se emplean diferentes tipos de cementos cumplen perfectamente con las previsiones en cuanto a sus resistencias a 28 días.

Fernández Cánovas, Manuel

1991-01-01

242

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

Energy Technology Data Exchange (ETDEWEB)

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') measurements, that the strength of the material increases dramatically (to approx1 GPa) for these extreme strain rates.

Murphy, W J; Higginbotham, A; Kimminau, G; Nagler, B; Vinko, S M; Whitcher, T; Wark, J S [Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Barbrel, B; Koenig, M [Laboratoire pour l' Utilisation des Lasers Intenses, UMR7605, CNRS-CEA-Universite Paris VI-Ecole Polytechnique, 91128 Palaiseau (France); Bringa, E M [Instituto de Ciencias Basicas, Universidad Nacional de Cuyo, Mendoza (Argentina); Hawreliak, J; Remington, B [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Kodama, R; Ozaki, N [Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871 (Japan); McBarron, W; Park, N; Rothman, S [Material Modelling Group, AWE, Aldermaston, Reading, Berkshire RG7 4PR (United Kingdom); Meyers, M A, E-mail: justin.wark@physics.ox.ac.u [Materials Science and Engineering Program, University of California, San Diego, CA 92093 (United States)

2010-02-17

243

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

International Nuclear Information System (INIS)

[en] 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') measurements, that the strength of the material increases dramatically (to ?1 GPa) for these extreme strain rates.

2010-02-17

244

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

Directory of Open Access Journals (Sweden)

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.

Li Qiang; Zhang Fengfeng; Yu Jingyuan

2013-01-01

245

Property of compressed creep for pillar components by using high strength concrete; Kokyodo concrete wo mochiita hashira buzai no asshuku kuripu seijo  

Energy Technology Data Exchange (ETDEWEB)

Many experiments on behaviors of the compressed creep for high strength concrete been performed until now. Since most of those experiments were carried out by using small-sized specimens, water fugacity to outside in concrete is different compared to practical components of structures. For its application to practical structures, the influence on size effect is necessarily clarified. In this paper, for clarifying the influences of section sizes, loading stresses and lasting conditions on the compressed creep of high strength concrete with the compressed strength {sigma}b = 1000 kgf/cm{sup 2} and 600 kgf/cm{sup 2}, experimental results of the compressed creep on practical-sized pillar components made by steel concrete and small-sized specimens in a load-lasting period of one year were reported. The comparison results to the reported creep properties of concrete with normal strength level of the compressed strength {sigma}b = 300 kgf/cm{sup 2} were also reported. 12 refs., 13 figs., 3 tabs.

Yasuda, M. [Toyo Construction Co. Ltd., Tokyo (Japan); Tobisaka, M. [Japan Testing Center for Construction Materials, Tokyo (Japan); Masuda, Y.; Abe, M. [Building Research Inst., Tokyo (Japan); Kawase, K. [Niigata Univ., Niigata (Japan); Takaha, N. [Nihon Cement Co. Ltd., Tokyo (Japan); Yamashita, T.

1994-08-01

246

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Murphy, WJ; Higginbotham, A; Kimminau, G; Barbrel, B; Bringa, EM

247

Changes in compressive strength on ageing in glass polyalkenoate (glass-ionomer) cements prepared from acrylic/maleic acid copolymers.  

UK PubMed Central (United Kingdom)

Previous studies have shown that glass-ionomers made from acrylic/maleic copolymers stored in water reach a maximum strength at about 1 week, and after 4 months have become significantly weaker. This finding, which contrasts with the behaviour of glass-ionomers based on poly(acrylic acid), was originally attributed to hydrolytic instability. This interpretation has been tested in the current work. Specimens of glass-ionomer prepared from acrylic/maleic acid copolymer have been stored for up to 4 months in different media, namely deionized water, dry air and vegetable oil, then tested for compressive strength. Specimens were in the form of cylinders of dimensions 6 mm high x 4 mm diameter, and storage temperature was 37 degrees C. Data were analysed using two-way analysis of variance (ANOVA) and in all three media specimens became weaker at 4 months than they had been at 1 week (P < 0.05). However, for the specimens stored in dry air and in water, the 1-week values were not the maximum. The fact that there was a loss of strength under all conditions led to the conclusion that it is not, after all, due to hydrolysis.

Nicholson JW; Abiden F

1997-01-01

248

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

Directory of Open Access Journals (Sweden)

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.

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

2012-01-01

249

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english 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 impr (more) oved 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.

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

2012-04-01

250

Prediction of 28-day compressive strength of concrete on the third day using artificial neural networks  

Directory of Open Access Journals (Sweden)

Full Text Available In recent decades, artificial neural networks are known as intelligent methods formodeling of behavior of physical phenomena. In this paper, implementation of anartificial neural network has been developed for prediction of compressivestrength of concrete. A MISO (Multi Input Single Output) adaptive system hasbeen introduced which can model the proposed phenomenon. The data hasbeen collected by experimenting on concrete samples and then the neuralnetwork has been trained using these data. From among 432 specimens, 300data sample has been used for train, 66 data sample for validation and 66 datasample for the final test of the network. The 3-day strength parameter of concretein the introduced structure also has been used as an important index forpredicting the 28-day strength of the concrete. The simulations in this paper arebased on real data obtained from concrete samples which indicate the validity ofthe proposed tool.

Vahid. K. Alilou; Vahid. K. Alilou

2010-01-01

251

The variation of compressive strength of AGR moderator graphite with increasing thermal weight loss  

Energy Technology Data Exchange (ETDEWEB)

Two hundred specimens of AGR moderator graphite were thermally oxidised up to 80% weight loss and tested in compression. Samples that were disintegrated during the oxidation process were included in the subsequent analysis. The results showed that there is no strong evidence to suggest that any established empirical relationship from previous studies, based on the Knudsen model, is optimistic by excluding highly oxidised or irregular samples. Analysis of the Knudsen relationship derived in this work, and in particular the value of the exponent b, showed that the Knudsen relationship is reliable up to 40% thermal weight loss with a constant value of b. However, at above 40% weight loss, there is evidence to suggest that the value of the exponent b increases to reflect the acceleration of the degradation of mechanical properties with increasing thermal weight loss. There is little evidence to suggest that samples with low weight losses will disintegrate within the weight loss range of the empirically derived Knudsen relationship.

Neighbour, G.B.; Hacker, P.J. [Nuclear Materials Group, Department of Engineering and Applied Science, University of Bath, Claverton Down, Bath, BA2 7AY Somerset (United Kingdom)

2001-11-01

252

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

Science.gov (United States)

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

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

2009-01-22

253

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

UK PubMed Central (United Kingdom)

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.

Aiello MA; Leuzzi F; Centonze G; Maffezzoli A

2009-06-01

254

Development of superhigh-strength mortars with compressive strength of 3000kgf/cm sup 2 or higher. 3000kgf/cm sup 2 ijo no asshuku kyodo wo motsu mortar no kaihatsu  

Energy Technology Data Exchange (ETDEWEB)

This paper discusses the preparation factors and curing conditions of superhigh-strength mortar, and explains a method of manufacturing superhigh-strength mortar having still higher strength and its superhigh strength generating mechanism. A recommended cement material for the superhigh-strength mortar is a Portland cement mixed with a high-purity silica at 20% and silica fume at 20%. This was made to a water-cement material ratio of 15% and fine aggregate cement material ratio of 1.06, cured in an autoclave, and further heat-cured at 200{degree}C for one day to obtain a superhigh-strength mortar. The compression and bending strengths reach 2,200 kgf/cm{sup 2} and 180 kgf/cm{sup 2} respectively when used with silica sand, and 3000 kgf/cm{sup 2} and 220 kgf/cm{sup 2} or more when used with stainless steel grits. The heat curing at 200{degree}C for a day increases remarkably the compression strength of the superhigh-strength mortar regardless of the curing conditions before the heat curing. 7 refs., 11 figs., 1 tab.

Ohama, Y.; Izumura, K. (Nihon University, Tokyo (Japan). Collete of Engineering); Hayashi, S. (Onoda Cement Co. Ltd., Yamaguchi (Japan))

1991-08-01

255

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

Directory of Open Access Journals (Sweden)

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

JAI PRAKASH SHARMA; SACHIN CHATURVEDI; PAWAN ARORA

2012-01-01

256

Method of increasing the phase stability and the compressive yield strength of uranium-1 to 3 wt. % zirconium alloy  

Energy Technology Data Exchange (ETDEWEB)

A uranium-1 to 3 wt. % zirconium alloy characterized by high strength, high ductility and stable microstructure is fabricated by an improved thermal mechanical process. A homogenous ingot of the alloy which has been reduced in thickness of at least 50% in the two-step forging operation, rolled into a plate with a 75% reduction and then heated in vacuum at a temperature of about 750.degree. to 850.degree. C. and then quenched in water is subjected to further thermal-mechanical operation steps to increase the compressive yield strength approximately 30%, stabilize the microstructure, and decrease the variations in mechanical properties throughout the plate is provided. These thermal-mechanical steps are achieved by cold rolling the quenched plate to reduce the thickness thereof about 8 to 12%, aging the cold rolled plate at a first temperature of about 325.degree. to 375.degree. C. for five to six hours and then aging the plate at a higher temperature ranging from 480.degree. to 500.degree. C. for five to six hours prior to cooling the billet to ambient conditions and sizing the billet or plate into articles provides the desired increase in mechanical properties and phase stability throughout the plate.

Anderson, Robert C. (Crossville, TN)

1986-01-01

257

A comparative evaluation of curing depth and compressive strength of dental composite cured with halogen light curing unit and blue light emitting diode: an in vitro study.  

UK PubMed Central (United Kingdom)

PURPOSE: To evaluate the curing depth and compressive strength of dental composite using halogen light curing unit and light emitting diode light curing unit. MATERIALS AND METHODS: Eighty cylindrical composite specimens were prepared using posterior composite P60(3M). Forty specimens, out of which 20 samples (group A) cured with halogen light and 20 samples (group B) cured using light emitting diode (LED) light were checked for curing depth according to ISO 4049. Remaining 40 samples out of which 20 samples (group I) cured using halogen light and 20 samples (group II) cured using LED light were checked for compressive strength using Instron universal testing machine. RESULTS: Twenty samples (group A) cured with halogen light showed better curing depth than 20 samples (group B) cured with LED light. Twenty samples (group I) cured with halogen light showed almost similar results as 20 samples (group II) cured with LED light for compressive strength. CONCLUSION: Halogen light commonly used to cure composite resin have greater depth of cure, when compared to LED light, while both the lights produced compressive strength which is almost similar. CLINICAL SIGNIFICANCE: Lower depth of cure with the LED unit, compared to the QTH unit, is associated with different light scattering due to differences in spectral emission. LED technology differs from QTH by the spectral emission that favorably matches the absorption spectrum of camphorquinone.

Kumar CN; Gururaj M; Paul J

2012-11-01

258

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1995-04-17

259

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 expe...

Saulius VAITKUS; Ivan GNIP; Sigitas V?JELIS

260

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

Directory of Open Access Journals (Sweden)

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

Fernández-Jiménez, A.; Palomo, A.

2007-01-01

 
 
 
 
261

Unconfined Aquifer Flow Theory - from Dupuit to present  

CERN Multimedia

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 ...

Mishra, Phoolendra K

2013-01-01

262

Differential blood contamination levels and powder-liquid ratios can affect the compressive strength of calcium phosphate cement (CPC): a study using a transpedicular vertebroplasty model.  

UK PubMed Central (United Kingdom)

PURPOSE: Calcium phosphate cement (CPC) is a potentially useful alternative to polymethylmethacrylate (PMMA) for transpedicular injection into osteoporotic vertebral fractures. Unlike PMMA, CPC is both biocompatible and osteoconductive without producing heat from polymerization, but it has lower compressive strength compared to PMMA. This in vitro model experiment analyzed how different CPC powder-liquid ratios (P/L ratios) and injection methods may minimize blood contamination in the CPC and, thereby its reduction in compressive strength. METHODS: (1) CPC of different P/L ratios of 4.0, 3.5, and 3.2 was equally mixed with different amounts of freshly obtained human venous blood, producing cylindrically shaped CPC samples. (2) Using a transpedicular vertebroplasty model containing blood in the bottom, CPC pastes of different P/L ratios were injected with the nozzle of an injection gun affixed either to the bottom (Bottom method) or to the top of the container (Top method). All cylindrical CPC samples thus obtained were immersed in simulated body fluid and then underwent compressive strength tests at 3 h-7 days post-immersion. RESULTS: In CPC equally mixed with blood, lower P/L ratios and a larger amount of blood contamination reduced compressive strength more significantly. Of the two methods of CPC injection, the 'Bottom method' produced significantly greater compressive strength values than the 'Top method'. CONCLUSIONS: When performing CPC-assisted vertebroplasty, a greater load bearing-support can be obtained by injecting CPC paste of a high P/L ratio of 4.0 into the deepest part of the space inside the vertebral body to minimize blood contamination.

Kiyasu K; Takemasa R; Ikeuchi M; Tani T

2013-07-01

263

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)

Full Text Available Abstract in portuguese 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 modelo foram realizadas variações na resistência à compressão do concreto de modo a se observar modificações no comportamento estrutural do elemento. A aná (more) lise 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] (more) . 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.

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

2013-02-01

264

Effect of heat treatment on bending strength, compressive strength and interfacial shear strength of carbon fiber reinforced aluminium alloys; Tanso sen`i/aruminiumu gokin fukugo zairyo no netsu shori ni yoru kaimen tsuyosa no henka to sono rikigakuteki tokusei eno eikyo  

Energy Technology Data Exchange (ETDEWEB)

Changes of matrix and interface by heat treatment are investigated for CF/Al alloy FRM (fiber reinforced material) which has been prepared on an experimental basis by pressure impregnation using 2 kinds of PAN base high elastic yarn and one kind of PAN based high elastic yarn, and the changes in the correlation among the bending strength, compression strength, and interfacial strength are investigated. The bending strength decreases rapidly from 1,200MPa to about 550MPa with the increase of the interfacial strength from 5MPa to about 25MPa and remains almost constant 450MPa with larger than 30MPa interfacial strength. The compressive strength shows no change even when the interfacial strength increases from 5MPa to 25MPa, but rapidly increases when the interfacial strength increases from 25MPa to 40MPa, and remains constant at about 1,600MPa when the interfacial strength increases higher than 40MPa. When the interfacial structure increases from 25MPa to 40MPa, the compressive strength increases from 600MPa to 900MPa. 14 refs., 7 figs., 2 tabs.

Yamada, K. [Toyo Exterior Co. Ltd., Nagano (Japan); Sekiguchi, S. [Nippon Steel Technoresearch Corp., Kawasaki (Japan); Inoue, T. [Nippon Steel Corp., Tokyo (Japan)

1997-03-15

265

Modeling Decomposition of Unconfined Rigid Polyurethane Foam  

Energy Technology Data Exchange (ETDEWEB)

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.

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

1999-11-08

266

Image compression in morphometry studies requiring 21 CFR Part 11 compliance: procedure is key with TIFFs and various JPEG compression strengths.  

UK PubMed Central (United Kingdom)

This study aims to compare the integrity and reproducibility of measurements created from uncompressed and compressed digital images in order to implement compliance with 21 CFR Part 11 for image analysis studies executed using 21 CFR Part 58 compliant capture systems. Images of a 400-mesh electron microscope grid and H&E stained rat liver tissue were captured on an upright microscope with digital camera using commercially available analysis software. Digital images were stored as either uncompressed TIFFs or in one of five different levels of JPEG compression. The grid images were analyzed with automatic detection of bright objects while the liver images were segmented using color cube-based morphometry techniques, respectively, using commercially-available image analysis software. When comparing the feature-extracted measurements from the TIFF uncompressed to the JPEG compressed images, the data suggest that JPEG compression does not alter the accuracy or reliability to reproduce individual data point measurements in all but the highest compression levels. There is, however, discordance if the initial measure was obtained with a TIFF format and subsequently saved as one of the JPEG levels, suggesting that the use of compression must precede feature extraction. It is a common practice in software packages to work with TIFF uncompressed images. However, this study suggests that the use of JPEG compression as part of the analysis work flow was an acceptable practice for these images and features. Investigators applying image file compression to other organ images will need to validate the utility of image compression in their work flow. A procedure to digitally acquire and JPEG compress images prior to image analysis has the potential to reduce file archiving demands without compromising reproducibility of data.

Tengowski MW

2004-03-01

267

Image compression in morphometry studies requiring 21 CFR Part 11 compliance: procedure is key with TIFFs and various JPEG compression strengths.  

Science.gov (United States)

This study aims to compare the integrity and reproducibility of measurements created from uncompressed and compressed digital images in order to implement compliance with 21 CFR Part 11 for image analysis studies executed using 21 CFR Part 58 compliant capture systems. Images of a 400-mesh electron microscope grid and H&E stained rat liver tissue were captured on an upright microscope with digital camera using commercially available analysis software. Digital images were stored as either uncompressed TIFFs or in one of five different levels of JPEG compression. The grid images were analyzed with automatic detection of bright objects while the liver images were segmented using color cube-based morphometry techniques, respectively, using commercially-available image analysis software. When comparing the feature-extracted measurements from the TIFF uncompressed to the JPEG compressed images, the data suggest that JPEG compression does not alter the accuracy or reliability to reproduce individual data point measurements in all but the highest compression levels. There is, however, discordance if the initial measure was obtained with a TIFF format and subsequently saved as one of the JPEG levels, suggesting that the use of compression must precede feature extraction. It is a common practice in software packages to work with TIFF uncompressed images. However, this study suggests that the use of JPEG compression as part of the analysis work flow was an acceptable practice for these images and features. Investigators applying image file compression to other organ images will need to validate the utility of image compression in their work flow. A procedure to digitally acquire and JPEG compress images prior to image analysis has the potential to reduce file archiving demands without compromising reproducibility of data. PMID:15200165

Tengowski, Mark W

268

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

Directory of Open Access Journals (Sweden)

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.

Dr.H.Sudarsana Rao; Sri. H. M. Somasekharaiah; Dr.Vaishali. G.Ghorpade

2012-01-01

269

Evaluation of the effect of blood contamination on the compressive strength of MTA modified with hydration accelerators  

Science.gov (United States)

Objectives This study was performed to evaluate the effect of blood contamination on the compressive strength (CS) of Root MTA (RMTA) modified with Calcium chloride (CaCl2) and Disodium hydrogen phosphate (Na2HPO4) as setting accelerators over time. Materials and Methods A total of 110 cylindrical specimens of RMTA were divided into 6 experimental groups as follows: Group1, RMTA; Group 2, RMTA modified with CaCl2 (RMTA-C); Group 3, RMTA modified with Na2HPO4 (RMTA-N); Group 4, RMTA contaminated with blood; Group 5, RMTA-C contaminated with blood; Group 6, RMTA-N contaminated with blood. The CS of specimens in all groups was evaluated after 3 hr, 24 hr, and 1 wk. In the modified groups (groups 2, 3, 5, and 6) the CS of five specimens per group was also evaluated after 1 hr. Results Blood contamination significantly reduced the CS of all materials at all time intervals (p < 0.05). After 3 hr, the CS of specimens in the RMTA groups (with and without blood contamination) was significantly lower than those in the RMTA-C and RMTA-N groups (p < 0.05). The CS values were not significantly different at the other time intervals. In all groups, the CS of specimens significantly increased over time (p < 0.05). Conclusions Blood contamination decreased the CS of both original and accelerated RMTA.

Oloomi, Kaveh; Saberi, Eshaghali; Mokhtari, Hadi; Mokhtari Zonouzi, Hamid Reza; Nosrat, Ali; Dummer, Paul Michael Howell

2013-01-01

270

Measurement of heat transfer and change in compressive strength of waste derived solid fuels due to devolatisation  

Energy Technology Data Exchange (ETDEWEB)

Solid waste derived fuels are being increasingly considered for application in waste-to-energy processes. This thermal treatment methodology is becoming more popular since it deals with two major issues; the disposal of solid wastes and the production of a biomass-derived energy source. This paper is concerned with the analysis of a variety of waste derived fuels including mixed RDF, wood and paper, in comparison with coal. A specially designed chamber was developed to heat the fuels in an inert atmosphere whilst simultaneously measuring the internal temperatures of the pellets. The pellets were also tested for compressive strength, to determine how the devolatilisation process affected the integrity of the pellets. Results showed that small RDF pellets devolatilise very quickly in a high temperature environment, whereas larger paper pellets have far longer lifespans. Waste derived pellets lose structural integrity far quicker than coal-based fuels, which was identified as being linked to the composition of the materials and the mode by which they are held together. 22 refs., 14 figs., 2 tabs.

R. Marsh; A.J. Griffiths; K.P. Williams [Cardiff University, Cardiff (United Kingdom). School of Engineering

2008-07-15

271

Strength characteristics of undisturbed intermediate soil; Shizen taiseki shita chukando no kyodo tokusei  

Energy Technology Data Exchange (ETDEWEB)

As for soil design, soil is classified into two types and they are sand and clay, however, as for real soil there exist a soil between sand and clay and it does resemble neither of them and this is called in general the intermediate soil. Determination of its strength constant has been a problem. In this report, laboratory experiment using undisturbed sample, electrostatic cone penetration test (CPT) and in-situ test using dilatometer test (DMT) were carried out. From the suction test, it was understood that the residual effective stress inside the test specimen decreased sharply because the intermediate soil is effected greatly by the stress released during sampling. Therefore, strength reduction due to tension is caused and strength was evaluated little in case of unconfined compression test with no confined pressure. Accordingly, it was understood that the reconsolidation method consolidated with the in-situ confined pressure is effective to determine the strength of the intermediate soil. 14 refs., 15 figs.

Tanaka, H.; Tanaka, M.; Tsuchida, T. [Port and Harbour Research Inst., Yokosuka (Japan)

1998-03-21

272

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

Directory of Open Access Journals (Sweden)

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.

Yu Jingyuan; Li Qiang; Tang Ji

2011-01-01

273

Unconfined versus confined speleogenetic settings: variations of solution porosity.  

Directory of Open Access Journals (Sweden)

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

Klimchouk Alexander

2006-01-01

274

Unconfined versus confined speleogenetic settings: variations of solution porosity  

Directory of Open Access Journals (Sweden)

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.

Klimchouk, A.B.

2003-01-01

275

Nematode Locomotion in Unconfined and Confined Fluids  

CERN Multimedia

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...

Bilbao, Alejandro; Vanapalli, Siva; Blawzdziewicz, Jerzy

2013-01-01

276

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 the successive values of compressed air/gas pressures due to the successive development of actual pore-fluid pressures and effective stresses during recharge of water of the unconfined zone during the onset of the summer monsoon of 2008 in the northern parts of India.

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

2010-01-01

277

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

Directory of Open Access Journals (Sweden)

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

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

2012-01-01

278

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2005-02-01

279

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.)

1990-01-01

280

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

DEFF Research Database (Denmark)

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

McAllister, Iain Wilson; Crichton, George C

1997-01-01

 
 
 
 
281

Ideal shear strength under compression and tension in C, Si, Ge, and cubic SiC: an ab initio density functional theory study  

International Nuclear Information System (INIS)

Ideal shear strength under superimposed normal stress of cubic covalent crystals (C, Si, Ge, and SiC) is evaluated by ab initio density functional theory calculation. Shear directions in [11 2-bar] and [1 1-bar 0] on the (111) plane are examined. The critical shear stress along the former direction is lower than that along the latter in all the crystals unless the hydrostatic tension is extremely high. In both the [11 2-bar]-shear and [1 1-bar 0]-shear, critical shear stress is increased by compression in C but is decreased in the other crystals. The different response of the critical shear stress to normal stress is due to the strength of the bond-order term, i.e. dependence of the short-range interatomic attraction on the bond-angle. (paper)

2011-09-28

282

Study on shear strength and deformation characteristics of marine clays investigated by direct shear test; Ichimen sendan shiken kara erareta kaisei nendo no henkei oyobi kyodo tokusei  

Energy Technology Data Exchange (ETDEWEB)

Shear strength and deformation characteristics of marine clays from various places in the world were determined by the direct shear test (DST). These were compared with those from unconfined compression test (UCT), triaxial compression/extension tests (CK0TCT/CK0TET), direct simple shear test (DSST), field vane test (FVT) and cone penetration test (CPT). The results obtained are as follows. For marine clays obtained in Asia, the increase rate of strength by DST under the normal compression condition was between 0.27 and 0.32 independent of plasticity index and regions. The shear strength by DST was well related to the compression and tensile strength by CK0TCT/CK0TET. The shear strength values by DST and DSST agreed well by correcting the loading rate and shear mechanism. The apparent shear compressibility decreased with increasing the plasticity index. The normalized values between 50 and 300 were obtained. It was considered that the DST method can be applied to the analysis of large deformation problems. 16 refs., 17 figs., 4 tabs.

Tsuji, K.; Hanzawa, H. [Toa Corp., Tokyo (Japan)

1998-06-21

283

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)

Full Text Available Abstract in portuguese 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, def (more) ormações 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 compressive strength, strain and failure modes of all the prism configurations were recorded. These results were then compared with different theoretical models for predicting co (more) mpressive 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.

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

2011-12-01

284

Distinct signaling mechanisms regulate migration in unconfined versus confined spaces.  

UK PubMed Central (United Kingdom)

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.

Hung WC; Chen SH; Paul CD; Stroka KM; Lo YC; Yang JT; Konstantopoulos K

2013-09-01

285

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

International Nuclear Information System (INIS)

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

2005-07-01

286

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)

Full Text Available Abstract in english 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, compressiv (more) e 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

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

2012-10-01

287

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

Science.gov (United States)

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

Sim, Jongsung; Park, Cheolwoo

2011-07-23

288

The effect of tensile and compressive loading on the hierarchical strength of idealized tropocollagen-hydroxyapatite biomaterials as a function of the chemical environment  

Energy Technology Data Exchange (ETDEWEB)

Hard biomaterials such as bone, dentin and nacre have primarily a polypeptide phase (e.g. tropocollagen (TC)) and a mineral phase (e.g. hydroxyapatite (HAP) or aragonite) arranged in a staggered manner. It has been observed that the mechanical behaviour of such materials changes with the chemical environment and the direction of applied loading. In the presented investigation, explicit three-dimensional molecular dynamics (MD) simulations based analyses are performed on idealized TC-HAP composite biomaterial systems to understand the effects of tensile and compressive loadings in three different chemical environments: (1) unsolvated, (2) solvated with water and (3) calcinated and solvated with water. The MD analyses are performed on two interfacial supercells corresponding to the lowest structural level (level n) of TC-HAP interactions and on two other supercells with HAP supercells arranged in a staggered manner (level n+1) in a TC matrix. The supercells at level n+1 are formed by arranging level n interfacial supercells in a staggered manner. Analyses show that at level n, the presence of water molecules results in greater stability of TC molecules and TC-HAP interfaces during mechanical deformation. In addition, water also acts as a lubricant between adjacent TC molecules. Under the application of shear stress dominated loading, water molecules act to strengthen the TC-HAP interfacial strength in a manner similar to the action of glue. An overall effect of the observed mechanisms is that, in a staggered arrangement, tensile strength increases in the presence of water and calcinated water environments. On the other hand, corresponding compressive strength decreases under similar circumstances. Fundamentally, supercells with primarily normal load transfer at the TC-HAP interfaces are stronger in tensile shear loading. On the other hand, supercells with primarily tangential or shear load transfer at the TC-HAP interfaces are stronger in compressive shear loading. A combination of changes in chemical environment from vacuum to calcinated water and changes in interfacial configurations in a staggered arrangement could be chosen to make the TC-HAP material stronger under applied deformation.

Dubey, Devendra K; Tomar, Vikas [Aerospace and Mechanical Engineering, University of Notre Dame, IN 46556 (United States)], E-mail: vikas.tomar@nd.edu

2009-05-20

289

[The influence of the number of bars on the axial compressive strength of uniplanar external fixators in polyurethane tibia models].  

UK PubMed Central (United Kingdom)

OBJECTIVE: This is an experimental study with the objective of analyses the increase of rigidity in synthetic tibia bones with external fixators, with single and double connecting rods and with stable and unstable fracture patterns. METHODS: The external fixators were used in the monoplanar, half pin configuration submitted to an axial compression load using the connecting bar in different patterns. Forty-eight similar models to the human tibia had been used. In all the models were left an interval of 0,5 cm between the fragments and were made cuts of 15 masculine and 45 masculine to simulate stable and unstable fracture patterns, respectively. The models had been divided in four groups in accordance with the cut (15 masculine and 45 masculine) and the number of metallic bars in assembly (1 and 2 bars). The study used the Instron testing machine which the models were submitted to the axial load until the fragments that were separated by a gap made full contact. RESULTS: The instability forces in the assembly with a double bar had been sufficiently superior to the forces with only one bar. It was still observed that the group with unstable fracture pattern and with only one connecting rod had a lesser variability compared with the other groups and presented more homogeneous results, with a minor average. CONCLUSION: The assembly with a double longitudinal connecting rod in the studied models is more stable than the others to stand compression load.

Kume MH; Malafaia O; Dietz UA; Deeke M; Borsato KS; Menegotto FG; Pundek MR

2010-02-01

290

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)

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

Saulius VAITKUS; Ivan GNIP; Sigitas V?JELIS

2013-01-01

291

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1988-09-01

292

High power light emitting diode (LED) arrays versus halogen light polymerization of oral biomaterials: Barcol hardness, compressive strength and radiometric properties.  

UK PubMed Central (United Kingdom)

The clinical performance of light polymerized dental composites is greatly influenced by the quality of the light curing unit (LCU) used. Commonly used halogen LCUs have some specific drawbacks such as decreasing light output with time. This may result in a low degree of monomer conversion of the composites with negative clinical implications. Previous studies have shown that blue light emitting diode (LED) LCUs have the potential to polymerize dental composites without having the drawbacks of halogen LCUs. Since these studies were carried out LED technology has advanced significantly and commercial LED LCUs are now becoming available. This study investigates the Barcol hardness as a function of depth, and the compressive strength of dental composites that had been polymerized for 40 or 20s with two high power LED LCU prototypes, a commercial LED LCU, and a commercial halogen LCU. In addition the radiometric properties of the LCUs were characterized. The two high power prototype LED LCUs and the halogen LCU showed a satisfactory and similar hardness-depth performance whereas the hardness of the materials polymerized with the commercial LED LCU rapidly decreased with sample depth and reduced polymerization time (20 s). There were statistically significant differences in the overall compressive strengths of composites polymerized with different LCUs at the 95% significance level (p = 0.0016) with the two high power LED LCU prototypes and the halogen LCU forming a statistically homogenous group. In conclusion, LED LCU polymerization technology can reach the performance level of halogen LCUs. One of the first commercial LED LCUs however lacked the power reserves of the high power LED LCU prototypes.

Mills RW; Uhl A; Blackwell GB; Jandt KD

2002-07-01

293

Raman spectroscopic determination of the length, strength, compressibility, Debye temperature, elasticity, and force constant of the C-C bond in graphene.  

UK PubMed Central (United Kingdom)

From the perspective of bond relaxation and bond vibration, we have formulated the Raman phonon relaxation of graphene, under the stimuli of the number-of-layers, the uni-axial strain, the pressure, and the temperature, in terms of the response of the length and strength of the representative bond of the entire specimen to the applied stimuli. Theoretical unification of the measurements clarifies that: (i) the opposite trends of the Raman shifts, which are due to the number-of-layers reduction, of the G-peak shift and arises from the vibration of a pair of atoms, while the D- and the 2D-peak shifts involve the z-neighbor of a specific atom; (ii) the tensile strain-induced phonon softening and phonon-band splitting arise from the asymmetric response of the C(3v) bond geometry to the C(2v) uni-axial bond elongation; (iii) the thermal softening of the phonons originates from bond expansion and weakening; and (iv) the pressure stiffening of the phonons results from bond compression and work hardening. Reproduction of the measurements has led to quantitative information about the referential frequencies from which the Raman frequencies shift as well as the length, energy, force constant, Debye temperature, compressibility and elastic modulus of the C-C bond in graphene, which is of instrumental importance in the understanding of the unusual behavior of graphene.

Yang XX; Li JW; Zhou ZF; Wang Y; Yang LW; Zheng WT; Sun CQ

2012-01-01

294

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

Directory of Open Access Journals (Sweden)

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 ?.

A. Kurzawa; J. W. Kaczmar

2011-01-01

295

Analytical solution for drainage and recession from an unconfined aquifer.  

UK PubMed Central (United Kingdom)

One-dimensional transient groundwater flow from a divide to a river in an unconfined aquifer described by the Boussinesq equation was studied. We derived the analytical solution for the water table recession and drainage change process described with a linearized Boussinesq equation with a physically based initial condition. A method for determining the average water table in the solutions was proposed. It is shown that the solution derived in the form of infinite series can be well approximated with the simplified solution which contains only the leading term of the original solution. The solution and their simplification can be easily evaluated and used by others to study the groundwater flow problems, such as drainage and base flow estimation, in an unconfined aquifer.

Liang X; Zhang YK

2012-09-01

296

Spontaneous Transition of Turbulent Flames to Detonations in Unconfined Media  

CERN Multimedia

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.

Poludnenko, Alexei Y; Oran, Elaine S

2011-01-01

297

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

UK PubMed Central (United Kingdom)

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.

Gabr MA; Bowders JJ

2000-09-01

298

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese 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 processos de preparação da madeira (preservação ou tratamentos ignífugos), analisar o efeito dessa exposição nas propriedades mecânicas da madeira. O presente artig (more) o 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), implies 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 microwav (more) e 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.

Machado, José Saporiti

2006-06-01

299

A stable and efficient numerical algorithm for unconfined aquifer analysis  

Energy Technology Data Exchange (ETDEWEB)

The non-linearity of equations governing flow in unconfined aquifers poses challenges for numerical models, particularly in field-scale applications. Existing methods are often unstable, do not converge, or require extremely fine grids and small time steps. Standard modeling procedures such as automated model calibration and Monte Carlo uncertainty analysis typically require thousands of forward model runs. Stable and efficient model performance is essential to these analyses. We propose a new method that offers improvements in stability and efficiency, and is relatively tolerant of coarse grids. It applies a strategy similar to that in the MODFLOW code to solution of Richard's Equation with a grid-dependent pressure/saturation relationship. The method imposes a contrast between horizontal and vertical permeability in gridblocks containing the water table. We establish the accuracy of the method by comparison to an analytical solution for radial flow to a well in an unconfined aquifer with delayed yield. Using a suite of test problems, we demonstrate the efficiencies gained in speed and accuracy over two-phase simulations, and improved stability when compared to MODFLOW. The advantages for applications to transient unconfined aquifer analysis are clearly demonstrated by our examples. We also demonstrate applicability to mixed vadose zone/saturated zone applications, including transport, and find that the method shows great promise for these types of problem, as well.

Keating, Elizabeth [Los Alamos National Laboratory; Zyvoloski, George [Los Alamos National Laboratory

2008-01-01

300

A stable and efficient numerical algorithm for unconfined aquifer analysis.  

UK PubMed Central (United Kingdom)

The nonlinearity of equations governing flow in unconfined aquifers poses challenges for numerical models, particularly in field-scale applications. Existing methods are often unstable, do not converge, or require extremely fine grids and small time steps. Standard modeling procedures such as automated model calibration and Monte Carlo uncertainty analysis typically require thousands of model runs. Stable and efficient model performance is essential to these analyses. We propose a new method that offers improvements in stability and efficiency and is relatively tolerant of coarse grids. It applies a strategy similar to that in the MODFLOW code to the solution of Richard's equation with a grid-dependent pressure/saturation relationship. The method imposes a contrast between horizontal and vertical permeability in gridblocks containing the water table, does not require "dry" cells to convert to inactive cells, and allows recharge to flow through relatively dry cells to the water table. We establish the accuracy of the method by comparison to an analytical solution for radial flow to a well in an unconfined aquifer with delayed yield. Using a suite of test problems, we demonstrate the efficiencies gained in speed and accuracy over two-phase simulations, and improved stability when compared to MODFLOW. The advantages for applications to transient unconfined aquifer analysis are clearly demonstrated by our examples. We also demonstrate applicability to mixed vadose zone/saturated zone applications, including transport, and find that the method shows great promise for these types of problem as well.

Keating E; Zyvoloski G

2009-07-01

 
 
 
 
301

Initial study of thermal energy storage in unconfined aquifers. [UCATES  

Energy Technology Data Exchange (ETDEWEB)

Convective heat transport in unconfined aquifers is modeled in a semi-analytic way. The transient groundwater flow is modeled by superposition of analytic functions, whereby changes in the aquifer storage are represented by a network of triangles, each with a linearly varying sink distribution. This analytic formulation incorporates the nonlinearity of the differential equation for unconfined flow and eliminates numerical dispersion in modeling heat convection. The thermal losses through the aquifer base and vadose zone are modeled rather crudely. Only vertical heat conduction is considered in these boundaries, whereby a linearly varying temperature is assumed at all times. The latter assumption appears reasonable for thin aquifer boundaries. However, assuming such thin aquifer boundaries may lead to an overestimation of the thermal losses when the aquifer base is regarded as infinitely thick in reality. The approach is implemented in the computer program UCATES, which serves as a first step toward the development of a comprehensive screening tool for ATES systems in unconfined aquifers. In its present form, the program is capable of predicting the relative effects of regional flow on the efficiency of ATES systems. However, only after a more realistic heatloss mechanism is incorporated in UCATES will reliable predictions of absolute ATES efficiencies be possible.

Haitjema, H.M.; Strack, O.D.L.

1986-04-01

302

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

Energy Technology Data Exchange (ETDEWEB)

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

Salem, A.; Rostami, N.

2013-06-01

303

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

International Nuclear Information System (INIS)

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

2013-01-01

304

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

Energy Technology Data Exchange (ETDEWEB)

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

Salem, A.; Rostami, N.

2013-05-01

305

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

International Nuclear Information System (INIS)

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

2013-01-01

306

Size effect on strength and strain hardening of small-scale [1 1 1] nickel compression pillars  

International Nuclear Information System (INIS)

This study investigates uniaxial compression behavior of focused ion beam (FIB) manufactured [1 1 1] nickel (Ni) small-scale pillars, ranging in diameter from approximately 25 ?m to below 200 nm, in order to examine the effect of crystallographic orientation on the mechanical properties. This study is unique from other micro-pillar studies in that the [1 1 1] orientation has a considerably lower Schmid factor, and has multiple slip systems available. The [1 1 1] Ni pillars show a strong increase in yield stress and work hardening with decreasing diameter. The relationship between yield stress and diameter (?y ? d-0.69) matches well with previous small-scale pillar studies. Strain hardening, which has been inconsistently observed in other micro-pillar studies, is found to be a function of both diameter and orientation. Although the precise mechanism for hardening is unknown, transmission electron microscopy reveals dislocations throughout the pillar and into the base material suggesting that dislocation interactions and deformation below the pillar play a role in the observed strain hardening. Furthermore, a slight crystallographic rotation of the pillar is observed likely contributing to the observed mechanical properties. By exploring the role of crystallography on the plastic deformation behavior, this study provides additional insight into the nature of the size effect.

2008-08-20

307

Desarrollo de un modelo de redes neuronales artificiales para predecir la resistencia a la compresión y la resistividad eléctrica del concreto Developing an artificial neural network model for predicting concrete’s compression strength and electrical resistivity  

Directory of Open Access Journals (Sweden)

Full Text Available En esta investigación se busca obtener un método para predecir la resistencia a la compresión mediante el peso unitario y la velocidad de pulso ultrasónico usando 41 mezclas de concreto diferentes. El estudio ha sido por la necesidad de obtener un método rápido para predecir la resistencia a la compresión del concreto. De la misma manera, la investigación también busca predecir la resistividad eléctrica del concreto mediante el peso unitario, la velocidad de pulso ultrasónico y la resistencia a la compresión. El modelo para predecir se realizó utilizando una regresión simple y un modelo de redes neuronales. Los resultados mostraron que los modelos de redes neuronales para predecir la resistencia a la compresión y la resistividad eléctrica del concreto funcionan adecuadamente.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 simple regression analysis and artificial neural networks. The results revealed that artificial neural networks can be used for effectively predicting compressive strength and electrical resistivity.

Lizarazo Marriaga Juan Manuel; Gómez Cortés José Gabriel

2007-01-01

308

Desarrollo de un modelo de redes neuronales artificiales para predecir la resistencia a la compresión y la resistividad eléctrica del concreto/ Developing an artificial neural network model for predicting concrete?s compression strength and electrical resistivity  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish En esta investigación se busca obtener un método para predecir la resistencia a la compresión mediante el peso unitario y la velocidad de pulso ultrasónico usando 41 mezclas de concreto diferentes. El estudio ha sido por la necesidad de obtener un método rápido para predecir la resistencia a la compresión del concreto. De la misma manera, la investigación también busca predecir la resistividad eléctrica del concreto mediante el peso unitario, la velocidad de pul (more) so ultrasónico y la resistencia a la compresión. El modelo para predecir se realizó utilizando una regresión simple y un modelo de redes neuronales. Los resultados mostraron que los modelos de redes neuronales para predecir la resistencia a la compresión y la resistividad eléctrica del concreto funcionan adecuadamente. Abstract in english 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 (more) was made using simple regression analysis and artificial neural networks. The results revealed that artificial neural networks can be used for effectively predicting compressive strength and electrical resistivity.

Lizarazo Marriaga, Juan Manuel; Gómez Cortés, José Gabriel

2007-04-01

309

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

Science.gov (United States)

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

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

2013-04-01

310

Probability distribution of uniaxial compression strength and failure life in air-dried and water-saturated conditions; Kikan jotai to shitsujun jotai deno ichijiku asshuku kyodo to kuripu jumyo no bunpu tokusei  

Energy Technology Data Exchange (ETDEWEB)

There is a way of thinking that the scattering of strength in rock is based on scattering of length and angles of cracks. Another way is based on the stochastic process theory, and providing the primary Poisson process is assumed to be satisfied, not only scattering of strength but also scattering of failure life can be discussed simultaneously. Uniaxial compression and creep test were carried out under air-dried and water-saturated conditions. Sample rocks were Sanjome andesite and Tage tuff. The experimental results indicate that uniaxial compression strength followed the Weibull distribution for both rocks whether in air-dried condition or in water-saturated condition. The logarithm of probability P of survival in creep test was plotted against the failure life t. Curves opening upwards were obtained except for Sanjome andesite in water-saturated condition, and the curves opening upwards meant large scattering. Failure life also followed the Weibull distribution approximately. 19 refs., 6 figs., 3 tabs.

Okubo, S. [Tokyo Univ. (Japan). Faculty of Engineering; Chu, Seokyeon [The Univ. of Tokyo, Tokyo (Japan). Graduate School

1994-06-25

311

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)

1997-01-01

312

Effect of Heat Treatment Upon the Compression Strength of Black Pine and Spruce – A Comparison Between Wood Originating From Mature Trees Vs. Thinnings  

Directory of Open Access Journals (Sweden)

Full Text Available The paper presents the results of anexperimental study performed with black pine (Pinusnigra L.) and spruce (Picea abies L.) wood, originatingfrom mature trees and thinnings cut from the sameparcel from the Stroesti-Arges region in Romania.After air drying and conditioning, the defect-freetest boards were cut into standard 20x20x60mmsamples for the compression test. The compressionstrength was measured and the rupture mode incompression was analyzed.Therefore, the sampleswere first dried to oven-dry state, then heat-treated athigh temperatures (180 and 200ºC) for 1, 2, 3 and 4hours. Sets of 10 samples from each wood species,wood assortment and treating regime were tested.The obtained results were comparativelyanalyzed for the two species (pine vs. spruce) and forthe two wood assortments (mature wood vs, thinwood). Then they were also expressed relatively tothe mass loss, considered to be the main indiactor ofthe degradation suffered by wood during the heattreatment.A graph was drawn for each species andassortment in order to establish the optimum treatingregime, considering the correlated influence of theheat treatment conditions upon all three analyzedproperties (mass loss, dimensional stability andcompression strength).The results of the present research are to bevalorized at the manufacturing of solid wood panelsmade from heat-treated lamellas.

Cristina OLARESCU; Mihaela CAMPEAN; Mihaela POROJAN

2013-01-01

313

Métodos de fixação de fraturas mandibulares em cães: resistência mecânica à compressão Strength to compression of fractured mandible fixed with different methods in dogs  

Directory of Open Access Journals (Sweden)

Full Text Available Foi testada a resistência mecânica à compressão em 30 hemimandíbulas coletadas de cadáveres caninos. Dez. hemimandíbulas foram mantidas íntegras (grupo 1 = controle). As outras 20 foram submetidas inicialmente a fraturas oblíquas simples, entre o segundo e terceiro pré-molares e, posteriormente, imobilizadas por meio do emprego de resina acrílica aplicada diretamente sobre as superfícies dentárias em conjunto com o fio metálico interdental (grupo 2) ou interfragmentar (grupo 3). A análise estatística mostrou diferença significativa entre os grupos (Gl>G2>G3). Foi possível concluir que o método empregado no grupo 2, além de ser menos invasivo e não ter o perigo de danificar as raízes dentárias, é mecanicamente mais resistente do que o utilizado no grupo 3.Strength to compression of 30 hemimandibles obtained from canine cadavers was tested. Ten intact hemimandibles were used as controls (group 1). The other twenty hemimandibles were submitted to simple oblique fractures between the second and third premolars. The hemimandibles were fixed with acrylic resin applied to the tooth crown surface combined with interdental wire (group 2) or interfragmentary wire (group 3). The method used in hemimandibles of group 2 was more resistam than that used in the group 3. Besides that it was less invasive and did not damage the tooth roots.

Sheila Canevese Rahal; Paulo Afonso Franciscone; Simone Iwabe; Flávia de Paula Soares

1998-01-01

314

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)

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.

Salem, Amin; Rostami, Nazila

2013-01-01

315

Compressive strain-dependent bending strength property of Al2O3-ZrO2 (1.5 mol% Y2O3) composites performance by HIP  

International Nuclear Information System (INIS)

Nanometric powders and sintered ceramics of Al2O3-ZrO2 (1.5 mol% Y2O3) prepared by hot isostatic pressing HIP have been studied. A detailed crystallographic study has been performed through X-ray diffraction, Williamson-Hall method, Rietveld method and high-resolution electron microscopy HREM analysis. The crystallographic structure data, such as domain size, lattice parameters, wt% phase, and micro-strain direction have been obtained using Rietveld refinement and Williamson-Hall methods. The results revealed that the compressive strain (?) increased from 0.56 to 1.18 (10-3) as the t-ZrO2 content increased too. The HREM interface study conducted along the [0 0 0 1]Al2O3||[0 0 1]ZrO2 zone axis revealed a micro-strain lattice distortion accumulated at the grain boundary due to the ZrO2 martensitic phase transformation on cooling, t-ZrO2 grains coalescence and to the grain growth of ?-Al2O3 which cause elongated tetragonal crystals. Micro-strain lattice distortion is adjusted by the shear displacements of the planes (1 1 0) and (11-bar0) along [1-bar10] and [1-bar1-bar0] crystallographic directions, respectively; these planes are arrested by the (101-bar0) alumina plane. In this case, semi-coherent interfaces were observed along the grain boundary. It is verified that the bending strength increased in connection with the strain accumulation and amount of tetragonal structure

2009-04-15

316

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)

Full Text Available Abstract in portuguese 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). Neste 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, (more) 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 rupt (more) ure 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.

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

2011-09-01

317

Influence Factor Analysis on Strength of Lime-Fly Ash Loess  

Directory of Open Access Journals (Sweden)

Full Text Available 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 that 90d strength can be considered to calculate the strength of lime-fly ash loess in practice. And the most important factor to influence the 90d strength of lime-fly ash loess is the amount of fly ash and lime, the second is moisture content, and then is the ratio of fly ash to lime (1:K). These achievements are significant to the design and application of lime-fly ash loess in subgrade construction of loess areas.

Yufen Zhang; Zhiquan Zhang

2013-01-01

318

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)

Full Text Available Abstract in portuguese 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 finalidade. 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 carr (more) egamento 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 regul (more) arity. 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.

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

2012-09-01

319

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  

Directory of Open Access Journals (Sweden)

Full Text Available 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.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 finalidade. 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.

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

2012-01-01

320

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)

Full Text Available Abstract in portuguese 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 concreto. A retirada precoce do escoramento submete a estrutura a uma carga prematura. Os danos causados pela incompleta reação de hidratação e cura do concreto p (more) odem 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 concrete. 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 tr (more) igger 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.

Vieira, Geilma Lima; Molin, Denise Carpena Coitinho Dal

2011-03-01

 
 
 
 
321

Simulation of flame acceleration in unconfined vapor cloud explosions  

Science.gov (United States)

The feasibility of numerical simulation in accident and safety analysis of unconfined vapor cloud explosions, and simulation of flame acceleration phenomenon from published data of experiments were studied. Two explosion experiments were simulated with the PHOENICS-code. The flame acceleration, mainly due to the enhanced combustion from turbulence generation at obstacles in the flow regime, can be simulated. The computation gives correct order of magnitude for the maximum overpressure in both explosions, of which one was weak and the other strong. The differences between the computed results and experiments are discussed and suggestions on how to improve the simulation model are given. More simulations of explosions and detailed experimental information of the initial conditions and development of the explosions are needed before simulations can reliably be used in accident and safety analysis.

Kjaeldman, L.; Huhtanen, R.

1985-08-01

322

Physical model simulations of seawater intrusion in unconfined aquifer  

Directory of Open Access Journals (Sweden)

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

Tanapol Sriapai; Chaowarin Walsri; Decho Phueakphum; Kittitep Fuenkajorn

2012-01-01

323

Strength and durability properties of core lithologies from coal-bearing Tyonek formation, Cook Inlet region, Alaska  

Energy Technology Data Exchange (ETDEWEB)

The Tyonek Formation (late Oligocene to middle Miocene) is a nonmarine unit of sandstone, siltstone, and claystone that contains large quantities of strippable subbituminous coal and lignite. The geotechnical properties, determined by field and laboratory tests on core from the Capps and Chuitna coalfields, dictate the equipment needs for excavation, determination of pit slope angle for mine planning, and durability of excavated spoil to weathering degradation. Point-load strength index tests are rapid and inexpensive field tests approximating the tensile and unconfined compressive strength of rock types. These tests, combined with laboratory uniaxial compression tests, were used to rank the formation lithologies in order of decreasing strength: coal (2670 psi), carbonaceous claystone (835 psi), siltstone (435 psi), claystone (375 psi), and sandstone (145 psi). Except for coal, the lithologies range in hardness from soft soil to soft rock. Laboratory slake durability index tests, which measure the deterioration potential of rock masses as a result of cyclic wetting and drying, were used to rank lithologies in order of decreasing durability: claystone (49%), carbonaceous claystone (46%), siltstone (40%), and sandstone (20%). The cored Tyonek lithologies are noncarbonate, and their strength and durability increase with decreasing grain size and increasing clay-particle content. Compressional wave velocity, combined with point-load data, indicates that most of the rocks could be removed by bull-dozers with ripping blades or by scrapers and shovels. However, coal (with rare exceptions, the strongest lithology tested) would require blasting before removal.

Odum, J.K.

1985-04-01

324

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)

Full Text Available Abstract in portuguese 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 ((more) inador 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 ((more) 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.

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

2012-06-01

325

Improvement of the mechanical properties of new calcium phosphate bone cements in the CaHPO4-alpha-Ca3(PO4)2 system: compressive strength and microstructural development.  

UK PubMed Central (United Kingdom)

The hardening properties of calcium phosphate cements in the CaHPO4-alpha-Ca3(PO4)2 (DCP-alpha-TCP) system have been investigated with interest focused on the compressive strength and microstructure development. Previous studies have shown that the addition of CaCO3(CC) leads to a modification of the calcium-deficient apatite structure of the reaction product, which results in a material more similar to the apatite in bone mineral. The addition of 10% w/w of CC to the initial DCP-alpha-TCP powder mixture resulted, with time, in a retardation of the development of compressive strength. However, the optimum compressive strength reached values up to 40% higher than CC-free samples. This retarding effect also has been monitored as a function of the calcium to phosphorus (Ca/P) ratio of the DCP and alpha-TCP mixture, showing the importance of the final cement properties of the relative quantities of the reactants in the mixture.

Fernández E; Gil FJ; Best SM; Ginebra MP; Driessens FC; Planell JA

1998-09-01

326

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)

Full Text Available Abstract in portuguese Comparou-se a Resistência à Compressão (RC) e à Tração Diametral (TD) de um cimento de ionômero de vidro de alta viscosidade [Fuji IX (GC Corporation)] e de dois novos cimentos Brasileiros [Vitro Molar (DFL) e Bioglass R (Biodinamica)], recentemente lançados no mercado, ambos indicados para o Tratamento Restaurador Atraumático (ART), em diferentes períodos de tempo. Foram confeccionados quinze corpos-de-prova com 6,0 mm de diâmetro x 3,0 mm de altura para o tes (more) te 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 Atraumatic Restorative Treatment (ART) technique. Fifteen disk specimens (6.0mm diameter x 3.0mm height) for the diametral tensile strength (DTS) test and fifteen cylindrical specimen (more) s (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.

Bresciani, Eduardo; Barata, Terezinha de Jesus Esteves; Fagundes, Ticiane Cestari; Adachi, Akimi; Terrin, Marina Martins; Navarro, Maria Fidela de Lima

2004-12-01

327

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

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Full Text Available The aim of this study was to compare, in different periods of time, the compressive and diametral tensile strength of a traditional high viscous glass ionomer cement: Fuji IX (GC Corporation), with two new Brazilian GIC's: Vitro-Molar (DFL) and Bioglass R (Biodinamica), all indicated for the Atraumatic Restorative Treatment (ART) technique. Fifteen disk specimens (6.0mm diameter x 3.0mm height) for the diametral tensile strength (DTS) test and fifteen cylindrical specimens (6.0mm diameter x 12.0mm height) for the compressive strength (CS) test were made of each GIC. Specimens were stored in deionized water at 37º C and 100% of humidity in a stove until testing. Five specimens of each GIC were submitted to CS and DTS test in each period, namely 1 hour, 24 hours and 7 days. The specimens were tested in a testing machine (Emic) at a crosshead speed of 1.0mm/min for CS and 0.5mm/min for the DTS test until failure occurred. The data were submitted to two-way ANOVA and Tukey tests (alpha=0.05). The mean CS values ranged from 42.03 to 155.47MPa and means DTS from 5.54 to 13.72 MPa, with test periods from 1h to 7 days. The CS and DTS tests showed no statistically significant difference between Fuji IX and Vitro Molar, except for CS test at 1-hour period. Bioglass R had lowest mean value for CS of the cements tested. In DTS test Bioglass R presented no statistically significant differences when compared with all others tested GICs at 1-hour period and Bioglass R presented no difference at 24-hour and 7-day periods when compared to Vitro-Molar. Further studies to investigate other physical properties such as fracture toughness and wear resistance, as well as chemical composition and biocompatibility, are now needed to better understand the properties of these new Brazilian GIC's.Comparou-se a Resistência à Compressão (RC) e à Tração Diametral (TD) de um cimento de ionômero de vidro de alta viscosidade [Fuji IX (GC Corporation)] e de dois novos cimentos Brasileiros [Vitro Molar (DFL) e Bioglass R (Biodinamica)], recentemente lançados no mercado, ambos indicados para o Tratamento Restaurador Atraumático (ART), em diferentes períodos de tempo. Foram confeccionados quinze corpos-de-prova com 6,0 mm de diâmetro x 3,0 mm de altura para o teste de TD e quinze com 6,0 mm de diâmetro e 12,0 mm de altura para o teste de RC, para cada ionômero a ser testado. Os corpos-de-prova foram armazenados em recipientes plásticos, com água deionizada, e mantidos em estufa a 37ºC e 100% de umidade, até a realização dos testes. Cinco corpos-de-prova de cada material foram submetidos aos testes de TD e RC em cada período de tempo: 1-hora, 24-horas e 7-dias, em uma máquina de testes universal (EMIC - DL 500) a uma velocidade de 1,0 mm/min para RC e 0,5mm/min para TD. Os dados obtidos foram submetidos aos testes ANOVA a dois critérios e Tukey (á=0,05). Os valores médios de RC e TD variaram de 42,03 a 155.47 MPa e de 5,54 a 13,72 MPa, respectivamente para os períodos analisados. O Fuji IX e o Vitro Molar não apresentaram diferenças em relação aos testes de RC e TD, exceto para RC no período de 1-hora. O Bioglass R apresentou os menores valores de RC dos cimentos testados. Na TD o Bioglass R não apresentou diferença em relação aos outros cimentos testados no período de 1-hora e não foi diferente do Vitro-Molar nos períodos de 24-horas e 7-dias. Mais estudos são necessários para avaliar outras propriedades mecânicas desses novos cimentos de ionômero de vidro brasileiros, tais como: tenacidade e desgaste, bem como composição química e biocompatibilidade.

Eduardo Bresciani; Terezinha de Jesus Esteves Barata; Ticiane Cestari Fagundes; Akimi Adachi; Marina Martins Terrin; Maria Fidela de Lima Navarro

2004-01-01

328

Finite-element model for concurrent confined-unconfined zones in an aquifer  

Energy Technology Data Exchange (ETDEWEB)

The numerical simulation of the situation of concurrent confined and unconfined zones in a groundwater aquifer system is conducted by using the finite-element method with 4-sided mixed-curved isoparametric elements. The model is limited to the steady state and is based on Dupuit's assumptions. The results of the model for a test situation indicate that the model can be used for prediction of the occurrence of unconfined regions around over-pumped wells in an originally confined aquifer of which the interfaces between the confined and unconfined regions may be estimated.

Elango, K.; Swaminathan, K.

1980-04-01

329

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  

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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.

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

2007-01-01

330

The influence of strain rate and sample inhomogeneity on the moduli and strength of welded tuff  

International Nuclear Information System (INIS)

A series of constant strain rate, unconfined compression experiments was performed on saturated welded tuff specimens collected from Busted Butte near Yucca Mountain, Nevada. Twenty specimens were loaded to failure at strain rates ranging from 10-9s-1 to 10-3s-1, under ambient pressure and temperature conditions. The strength of the specimens showed a continuous decrease with decreasing strain rate between 10-9 s-1 and 10-5 s-1. At the highest strain rate, 10-3 s-1, strengths were less than those observed at 10-5 s-1, likely due to hydrofracturing within the specimen at rapid loading rates. Reduction in strength, corresponding to the decrease in strain rate, is explained in terms of stress corrosion cracking. A detailed examination of six specimens tested at a strain rate of 10-9 s-1, using acoustic wave velocities and CT scans, shows a correlation between the nature of the microstructure of the specimens and the observed strengths and elastic moduli.

1992-01-01

331

Time dependent strength and stiffness of PCC bottom ash-bentonite mixtures  

Energy Technology Data Exchange (ETDEWEB)

Utilization of bottom ash from burning of pulverized coal in construction-related applications has received some attention within the last decade. Its use in geotechnical engineering applications is still very limited. However within the last few years several studies have been completed to evaluate strength, stiffiness, and durability properties of pulverized coal combustion (PCC) bottom ash mixed with various admixtures. Studies have shown that the physical properties of bottom ash obtained from burning of pulverized coal are similar to that of natural sand with particle sizes ranging from fine gravel to fine sand and low percentages of silt and clay sized particles. However unlike sand, chemical composition of bottom ash results in change of strength and stiffiness characteristics of the bottom ash-admixture mixtures with time. In this study, change in strength and stiffness characteristics of Illinois PCC bottom ash and bentonite mixtures with time are evaluated. A series of unconfined compression tests on bottom ash-bentonite mixtures at various curing ages was performed in the laboratory. Results presented show that strength and stiffness of bottom ash-bentonite mixtures changed significantly with time.

Kumar, S.; Vaddu, P. [South Illinois University, Carbondale, IL (United States). Dept. of Civil Engineering

2004-07-01

332

Transient radial flow to a well in an unconfined aquifer  

Energy Technology Data Exchange (ETDEWEB)

The analytic solutions of Boulton (1954) and Neuman (1972) for transient flow to a well in an unconfined aquifer are based on the assumption that the role of the unsaturated zone can be adequately accounted for by restricting attention to the release of water from the zone through which the water table moves. Both researchers mathematically treat this released water as a time-dependent source term. The differences between the models of Boulton and Neuman are that the former neglects vertical components of flow in the aquifer, but allows for an exponential process for the release of water as a function of time, whereas the latter assumes instantaneous release from storage, but accounts for vertical components of flow. Given this set of assumptions, we examine the applicability of these two methods using a general purpose numerical model through a process of verification extension and comparison. The issues addressed include: the role of well-bore storage in masking intermediate-time behavior, combined effects of exponential release as well as vertical flow, logic for vertical averaging of drawdowns, and the sensitivity of system response to the magnitude of specific yield. The issue of how good the assumptions of Boulton and Neuman are in the context of the general theory of unsaturated flow is addressed in part 2 of this two-part series of reports.

Narasimhan, T.N.; Zhu, Ming.

1991-08-01

333

Capillary effect on water table fluctuations in unconfined aquifers  

Science.gov (United States)

Parlange and Brutsaert (1987) derived a modified Boussinesq equation to account for the capillary effect on water table dynamics in unconfined aquifers. Barry et al. (1996) solved this equation subject to a periodic boundary condition. Their solution shows significant influence of capillarity on water table fluctuations, which evolve to finite-amplitude standing waves at the high frequency limit. Here we propose a new governing equation for the water table, which considers both horizontal and vertical flows in an unsaturated zone of finite thickness. An approximate analytical solution for periodic water table fluctuations based on the new equation was derived. In agreement with previous results, the analytical solution shows that the unsaturated zone's storage capacity permits water table fluctuations to propagate more readily than predicted by the Boussinesq equation. Furthermore, the new solution reveals a capping effect of the unsaturated zone on both the amplitude and phase of the water table fluctuations as well as the water table overheight. Due to the finite thickness of the unsaturated zone, the capillary effect on water table fluctuations is modified mainly with reduced amplitude damping and phase shift.

Kong, Jun; Shen, Cheng-Ji; Xin, Pei; Song, Zhiyao; Li, Ling; Barry, D. A.; Jeng, D.-S.; Stagnitti, F.; Lockington, D. A.; Parlange, J.-Y.

2013-05-01

334

Slug test in an unconfined aquifer: A Richards` equation perspective  

Energy Technology Data Exchange (ETDEWEB)

Slug tests have been used for over 30 years as a means of evaluating hydraulic parameters of aquifers. The interpretation of transient water level data from these tests has almost exclusively been based on fitting the data to analytical solutions or on using semi-analytical methods. Because these methods are constrained by simplifying assumptions, it is useful to investigate the conditions under which these assumptions are reasonable so that the interpretation of field data can be carried out with increased confidence. To this end, the authors investigate the transient flow of water in an unconfined aquifer during a slug test, using a numerical model that solves the generalized Richards` equation. The model accounts for saturated-unsaturated flow, time-dependent seepage face in the well, various combinations of blank casings and well screens, and injection or withdrawal tests. Parametric studies were conducted using a fully penetrating well in a 10 meter thick, homogeneous, isotropic aquifer with an initial hydrostatic condition in order to provide insights into such issues as (1) the difference in response between injection and bail-out tests, (2) the significance of flow through the transient seepage face, and (3) the role of the unsaturated zone. An examination of the flow anatomy suggests that flow in the unsaturated zone is significant and important, although the response of the water level in the well may not be very sensitive to the unsaturated zone processes. A second part of the present study investigated the reasonableness of widely used techniques of interpretation.

Weeber, P. [HSI Geotrans, Roswell, GA (United States); Narasimhan, T.N. [Lawrence Berkeley National Lab., CA (United States)

1997-10-01

335

Compressive strength of resin-modified glass ionomer restorative material: effect of P/L ratio and storage time Resistência à compressão de ionômeros de vidro modificados por resina: efeito da relação P/L e tempos de armazenagem  

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Full Text Available The aim of this study was to evaluate the compressive strength of resin-modified glass ionomer cement Fuji II LC and Vitremer, in powder/liquid ratios of 1:1, 1:2 and 1:3, at three periods (24 hours, 7 and 28 days) of storage in distilled water at 37ºC. For each material, P/L ratio and storage time, 5 cylindrical specimens were prepared, with 4mm diameter and 6mm height, in silicon moulds. Specimens were light-cured for 40 seconds at each extremity, removed from the moulds and laterally light-cured (perpendicular to long axis) for 40 seconds, protected as recommended by the manufacturers and immersed for the time tested. The specimens were submitted to compressive strength testing in an Instron machine at a crosshead speed of 1.0mm/min until failure. Data were submitted to ANOVA and Tukey's test (5%), and showed that the compressive strength of resin-modified glass ionomer cement was reduced when P/L ratio was reduced and that the storage in water had little influence on compressive strength.O objetivo deste estudo foi avaliar a resistência à compressão dos cimentos de ionômero de vidro modificados por resina Vitremer e Fuji II LC, nas relações pó/líquido 1:1, 1:2 e 1:3, por três períodos de armazenagem (24 horas, 7 e 28 dias) em água destilada a 37 ºC. Para cada material, relação pó/líquido e tempo de armazenagem, cinco corpos-de-prova cilíndricos foram preparados com 4 mm de diâmetro por 6 mm de altura, em moldes de silicone. Os corpos-de-prova foram fotoativados por 40 segundos, em cada extremidade, removidos dos moldes, fotoativado lateralmente (perpendicular ao longo eixo) por 40 segundos, protegidos conforme as instruções dos fabricantes e imersos pelo tempo de teste. Os corpos-de-prova foram submetidos à compressão em uma Instron, à velocidade de 1,0 mm/min até a falha. Os dados foram submetidos à análise de variância e ao teste de Tukey (5%), e mostraram que a resistência à compressão do cimento de ionômero de vidro modificado por resina foi reduzida quando a relação P/L foi diminuída e a armazenagem em água destilada teve pouca influência na resistência à compressão.

Mônica Aratani; Antônio Carlos Pereira; Lourenço Correr-Sobrinho; Mário Alexandre Coelho Sinhoreti; Simonides Consani

2005-01-01

336

Optimization of unconfined shallow aquifer water storage for irrigation  

Energy Technology Data Exchange (ETDEWEB)

A physically based simulation model was developed to optimize pumping from shallow unconfined aquifers for irrigation. The model uses evapotranspiration, rainfall, crop, soil, and aquifer properties to calculate runoff, recharge, rejected recharge, and water table depth. The model predicted water table elevations over the five-year period with reasonable accuracy using the data from a small watershed in northwest Bangladesh. Four optimized pumping regimes were developed for shallow deep tubewell irrigation of rice and wheat grown in the Rabi (dry) sea-Bon. The improved irrigation system management increased groundwater recharge, thereby decreasing rejected recharge. Under improved management, pumping of groundwater was distributed over three crop: growing seasons, increasing total crop production as the cropping intensity increased. The net benefits for crop production from the improved management with the rice-based cropping pattern were 15 percent and 27 percent more with shallow and deep tubewells, respectively, than with the existing irrigation management. The average yearly rejection of rainfall recharge decreased from 590 mm under rain fed cropping to 440 mm for the existing irrigation management when irrigation was applied only in the Rabi season. When irrigation was applied in all three crop seasons under an improved irrigation management system, the rejection of recharge was only 160 mm. Thus it was possible to minimize the rejection of recharge by optimizing pumping and thereby to significantly increase the available irrigation water supply. Minimizing the rejected recharge reduced the surface runoff that contributes to the flooding that occurs most years in Bangladesh. By irrigating less than 100 percent of the area with tubewells, it was possible to avoid the overdraft of groundwater. The model can be used for other areas where soil, aquifer, crop, and weather data are available.

Roy, K.C.

1989-01-01

337

Water table waves in an unconfined aquifer: Experiments and modeling  

Science.gov (United States)

Comprehensive measurements are presented of the piezometric head in an unconfined aquifer during steady, simple harmonic oscillations driven by a hydrostatic clear water reservoir through a vertical interface. The results are analyzed and used to test existing hydrostatic and nonhydrostatic, small-amplitude theories along with capillary fringe effects. As expected, the amplitude of the water table wave decays exponentially. However, the decay rates and phase lags indicate the influence of both vertical flow and capillary effects. The capillary effects are reconciled with observations of water table oscillations in a sand column with the same sand. The effects of vertical flows and the corresponding nonhydrostatic pressure are reasonably well described by small-amplitude theory for water table waves in finite depth aquifers. That includes the oscillation amplitudes being greater at the bottom than at the top and the phase lead of the bottom compared with the top. The main problems with respect to interpreting the measurements through existing theory relate to the complicated boundary condition at the interface between the driving head reservoir and the aquifer. That is, the small-amplitude, finite depth expansion solution, which matches a hydrostatic boundary condition between the bottom and the mean driving head level, is unrealistic with respect to the pressure variation above this level. Hence it cannot describe the finer details of the multiple mode behavior close to the driving head boundary. The mean water table height initially increases with distance from the forcing boundary but then decreases again, and its asymptotic value is considerably smaller than that previously predicted for finite depth aquifers without capillary effects. Just as the mean water table over-height is smaller than predicted by capillarity-free shallow aquifer models, so is the amplitude of the second harmonic. In fact, there is no indication of extra second harmonics (in addition to that contained in the driving head) being generated at the interface or in the interior.

Cartwright, Nick; Nielsen, Peter; Dunn, Scott

2003-12-01

338

Characterization of controlled low-strength material obtained from dewatered sludge and refuse incineration bottom ash: Mechanical and microstructural perspectives.  

UK PubMed Central (United Kingdom)

Potential reuse of dewatered sludge (DS) and municipal solid waste incineration (MSWI) bottom ash as components to develop controlled low-strength material (CLSM) was explored. The effects of DS:MSWI bottom ash:calcium sulfoaluminate (CS¯A) cement ratio and thermal treatment of MSWI bottom ash at 900 °C on the mechanical and microstructural properties of CLSM were intensively studied to optimize the process. Results showed DS and MSWI bottom ash could be utilized for making CLSM. The CLSM prepared with milled MSWI bottom ash gave higher unconfined compressive strength (UCS) of 2.0-6.2 MPa following 1 year of curing at 1.0:0.1:0.9 ? DS:MSWI bottom ash:CS¯A ? 1.0:0.8:0.2. However, the corresponding strengths for CLSM containing thermally treated MSWI bottom ash ranged from 0.7 to 4.6 MPa, decreasing 26-65%. The microstructural analysis by X-ray powder diffraction (XRD), Fourier transforms infrared spectroscopy (FT-IR), as well as scanning electron microscopy (SEM) combined with an energy dispersive X-ray spectroscopy (EDS) revealed that ettringite (C3A·3CS¯·H32, or AFt) crystals were the most important strength-producing constituents which grew into and filled the CLSM matrix pores. Milled MSWI bottom ash addition favored the formation of highly crystalline AFt phases and accordingly enhanced compressive strengths of CLSM specimens. In contrast, thermal treatment at 900 °C produced new phases such as gehlenite (Ca2Al2SiO7) and hydroxylapatite (Ca5(PO4)3(OH)), which deteriorated the pozzolanic activity of bottom ash and caused the strengths to decrease. Leaching tests evidenced that leachable substances from CLSM samples exhibited negligible health and environmental risks. The results of this study suggested that MSWI bottom ash can be effectively recycled together with DS in developing CLSM mixtures with restricted use of CS¯A cement.

Zhen G; Lu X; Zhao Y; Niu J; Chai X; Su L; Li YY; Liu Y; Du J; Hojo T; Hu Y

2013-11-01

339

Characterization of controlled low-strength material obtained from dewatered sludge and refuse incineration bottom ash: Mechanical and microstructural perspectives.  

Science.gov (United States)

Potential reuse of dewatered sludge (DS) and municipal solid waste incineration (MSWI) bottom ash as components to develop controlled low-strength material (CLSM) was explored. The effects of DS:MSWI bottom ash:calcium sulfoaluminate (CS¯A) cement ratio and thermal treatment of MSWI bottom ash at 900 °C on the mechanical and microstructural properties of CLSM were intensively studied to optimize the process. Results showed DS and MSWI bottom ash could be utilized for making CLSM. The CLSM prepared with milled MSWI bottom ash gave higher unconfined compressive strength (UCS) of 2.0-6.2 MPa following 1 year of curing at 1.0:0.1:0.9 ? DS:MSWI bottom ash:CS¯A ? 1.0:0.8:0.2. However, the corresponding strengths for CLSM containing thermally treated MSWI bottom ash ranged from 0.7 to 4.6 MPa, decreasing 26-65%. The microstructural analysis by X-ray powder diffraction (XRD), Fourier transforms infrared spectroscopy (FT-IR), as well as scanning electron microscopy (SEM) combined with an energy dispersive X-ray spectroscopy (EDS) revealed that ettringite (C3A·3CS¯·H32, or AFt) crystals were the most important strength-producing constituents which grew into and filled the CLSM matrix pores. Milled MSWI bottom ash addition favored the formation of highly crystalline AFt phases and accordingly enhanced compressive strengths of CLSM specimens. In contrast, thermal treatment at 900 °C produced new phases such as gehlenite (Ca2Al2SiO7) and hydroxylapatite (Ca5(PO4)3(OH)), which deteriorated the pozzolanic activity of bottom ash and caused the strengths to decrease. Leaching tests evidenced that leachable substances from CLSM samples exhibited negligible health and environmental risks. The results of this study suggested that MSWI bottom ash can be effectively recycled together with DS in developing CLSM mixtures with restricted use of CS¯A cement. PMID:23933484

Zhen, Guangyin; Lu, Xueqin; Zhao, Youcai; Niu, Jing; Chai, Xiaoli; Su, Lianghu; Li, Yu-You; Liu, Yuan; Du, Jingru; Hojo, Toshimasa; Hu, Yong

2013-08-07

340

Buckling strength of composite laminated plates with initial imperfections under uniaxial compression; Shoki fusei wo yusuru fukugo zairyo sekisoban no asshuku zakutsu kyodo  

Energy Technology Data Exchange (ETDEWEB)

As for the composite laminated plates under compressive loads, the behavior after primary buckling when initial imperfection was considered, was analyzed as an example of CFRP cross ply laminated plate. Unstable phenomenon after primary buckling whose research cases were still rare, in short, the necessity of secondary buckling phenomena was proved by stable division method using secondary variation of total potential energy. And this proved that there was load resistance power even after primary buckling, and the effect of various factors on secondary buckling phenomenon was studied by analytical method. When nondimensional average compression stress was constant, the average axial compression of laminated plates became greater for imperfection w{sub 11}>0 than that of imperfection w{sub 11}<0 and it shifted to danger side when displacement was taken as base. From the relation of each initial imperfection and secondary buckling, the value for secondary buckling was 89.586 when there was no primary imperfection, and the effect was thought to be small because this value did not differ much with that of secondary buckling for a small primary imperfection. 7 refs., 3 figs., 3 tabs.

Kasuya, H. [Tokai Univ., Tokyo (Japan). Faculty of Engineering; Minobe, A. [Ishikawajima Harima Heavy Industries Co. Ltd., Tokyo (Japan). Research Inst.

1993-07-15

 
 
 
 
341

Resistência à compressão do solo-cimento com substituição parcial do cimento Portland por resíduo cerâmico moído Compressive strength of soil-cement with partial replacement of the Portland cement by crushed ceramic waste  

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Full Text Available Neste trabalho, apresenta-se o estudo experimental da resistência à compressão do solo-cimento, com substituição parcial do cimento Portland por resíduo cerâmico moído. Para tanto, foram ensaiados 81 espécimenes cilíndricos desse material à compressão, em que parte do cimento foi substituída por material cerâmico moído. Realizou-se uma programação fatorial, na qual três variáveis foram selecionadas para estudo: o teor de material ligante (cimento + resíduo cerâmico), a umidade do solo e o teor de resíduo cerâmico adicionado. É apresentado um estudo estatístico através de análise de variância da massa específica do material e da resistência a compressão. Tal estudo permitiu concluir-se que substituições de 25 e 57% do teor de cimento por material cerâmico podem produzir blocos de solo-cimento com resistências superiores a 2 MPa, com teor de material ligante de 6 e 8%, respectivamente.In this paper, an experimental study of the compressive strength of soil-cement with partial replacement of the Portland cement by crushed ceramic waste is presented and discussed. For this, eighty-one cylindrical specimens of soil-cement were tested, where part of cement percentage was replaced by crushed ceramic waste. The experiment was conducted in factorial design and three variables were selected and studied: the binding material content (cement + ceramic waste), soil moisture content and the ratio of ceramic waste. A statistical study using variance analysis of the specific mass and compressive strength of the material is presented. This study concluded that replacement ratios of 25 and 57% of the Portland cement by crushed ceramic material can be used to fabricate soil-cement bricks with strength higher than 2 MPa, for a binding material content of 6 and 8% respectively.

Rivanildo Dallacort; Humberto C. Lima Júnior; Fábio L. Willrich; Normando P. Barbosa

2002-01-01

342

Resistência à compressão do solo-cimento com substituição parcial do cimento Portland por resíduo cerâmico moído/ Compressive strength of soil-cement with partial replacement of the Portland cement by crushed ceramic waste  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Neste trabalho, apresenta-se o estudo experimental da resistência à compressão do solo-cimento, com substituição parcial do cimento Portland por resíduo cerâmico moído. Para tanto, foram ensaiados 81 espécimenes cilíndricos desse material à compressão, em que parte do cimento foi substituída por material cerâmico moído. Realizou-se uma programação fatorial, na qual três variáveis foram selecionadas para estudo: o teor de material ligante (cimento + res? (more) ?duo cerâmico), a umidade do solo e o teor de resíduo cerâmico adicionado. É apresentado um estudo estatístico através de análise de variância da massa específica do material e da resistência a compressão. Tal estudo permitiu concluir-se que substituições de 25 e 57% do teor de cimento por material cerâmico podem produzir blocos de solo-cimento com resistências superiores a 2 MPa, com teor de material ligante de 6 e 8%, respectivamente. Abstract in english In this paper, an experimental study of the compressive strength of soil-cement with partial replacement of the Portland cement by crushed ceramic waste is presented and discussed. For this, eighty-one cylindrical specimens of soil-cement were tested, where part of cement percentage was replaced by crushed ceramic waste. The experiment was conducted in factorial design and three variables were selected and studied: the binding material content (cement + ceramic waste), so (more) il moisture content and the ratio of ceramic waste. A statistical study using variance analysis of the specific mass and compressive strength of the material is presented. This study concluded that replacement ratios of 25 and 57% of the Portland cement by crushed ceramic material can be used to fabricate soil-cement bricks with strength higher than 2 MPa, for a binding material content of 6 and 8% respectively.

Dallacort, Rivanildo; Lima Júnior, Humberto C.; Willrich, Fábio L.; Barbosa, Normando P.

2002-12-01

343

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

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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.

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

1991-01-01

344

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

International Nuclear Information System (INIS)

[en] Three tests were performed to measure the consolidation, permeability, and compressive strength of specimens prepared from bentonite/crushed salt mixtures. Each mixture comprised 30% bentonite and 70% crushed salt based on total dry weight. Brine was added to each mixture to adjust its water content to either 5 or 10% (nominal) of the total dry weight of the mixture. In the consolidation tests, each specimen was subjected to multiple stages of successively higher hydrostatic stress (pressure). During each stage, the pressure was maintained at a constant level and volumetric strain data were continuously logged. By using multiple stages, consolidation data were obtained at several pressures and the time required to consolidate the specimens to full saturation was reduced. Once full saturation was achieved, each specimen was subjected to a final test stage in which the hydrostatic stress was reduced and a permeability test performed. Permeability was measured using the steady flow of brine and was found to range between 1 x 10-17 and 5 x 10-17 m2. After the final test stage, unconfined compressive strength was determined for each specimen and was found to range between 0.5 and 8.1 MPa. Two constitutive models were fitted to the consolidation data. One relatively simple model related volumetric strain to time while the other related instantaneous density to time, pressure, and initial density. 8 refs., 9 figs., 8 tabs

1991-01-01

345

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  

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Full Text Available Abstract in spanish 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 evaluar la resistencia a la compresión de Ionofil Molar® y Vitremer®, según tiempo de exposición en saliva artificial. Materiales y Métodos: Se prepararon 5 muestras pa (more) ra 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 compressive 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 (more) 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.

Hernández González, R; Moraga Castillo, R; Velásquez Castilla, M; Gutiérrez Flores, F

2013-08-01

346

Compressible Modules  

CERN Document Server

The main purpose of this paper is to study under what condition compressible modules are critically compressible. A sufficient condition for the injective hull of a critically compressible module to be critically compressible is also provided. Furthermore we prove sufficient conditions for a critically compressible module to be continuous. In addition, some characterization of critically compressible modules in terms of CS modules, nonsingular modules and cyclic modules are also provided

Singh, Abhay K

2012-01-01

347

Dissolution rates and vadose zone drainage from strontium isotope measurements of groundwater in the Pasco Basin, WA unconfined aquifer  

International Nuclear Information System (INIS)

Strontium isotope compositions measured in groundwater samples from 273 wells in the Pasco Basin unconfined aquifer below the Hanford Site show large and systematic variations that provide constraints on groundwater recharge, weathering rates of the aquifer host rocks, communication between unconfined and deeper confined aquifers, and vadose zone-groundwater interaction. This article describes the evaluation of strontium geochemistry of a major aquifer.

2006-04-30

348

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  

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Full Text Available Abstract in spanish 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, (more) 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 (more) 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.

Bernal López, Susan; Gordillo, Marisol; Mejía de Gutiérrez, Ruby; Rodríguez Martínez, Erich; Delvasto Arjona, Silvio; Cuero, Robert

2009-09-01

349

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)

Full Text Available Abstract in spanish 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 contr (more) ol (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 re (more) sin-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.

Vergara, C; Uribe, S

2012-04-01

350

Compressive strength of glass ionomer cements using different specimen dimensions Resistência à compressão de cimentos de ionômero de vidro utilizando-se diferentes tamanhos de corpos-de-prova  

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Full Text Available The purpose of this study was to evaluate the compressive strength of two glass ionomer cements, a conventional one (Vitro Fil® - DFL) and a resin-modified material (Vitro Fil LC® - DFL), using two test specimen dimensions: One with 6 mm in height and 4 mm in diameter and the other with 12 mm in height and 6 mm in diameter, according to the ISO 7489:1986 specification and the ANSI/ADA Specification No. 66 for Dental Glass Ionomer Cement, respectively. Ten specimens were fabricated with each material and for each size, in a total of 40 specimens. They were stored in distilled water for 24 hours and then subjected to a compressive strength test in a universal testing machine (EMIC), at a crosshead speed of 0.5 mm/min. The data were statistically analyzed using the Kruskal-Wallis test (5%). Mean compressive strength values (MPa) were: 54.00 ± 6.6 and 105.10 ± 17.3 for the 12 mm x 6 mm sample using Vitro Fil and Vitro Fil LC, respectively, and 46.00 ± 3.8 and 91.10 ± 8.2 for the 6 mm x 4 mm sample using Vitro Fil and Vitro Fil LC, respectively. The resin-modified glass ionomer cement obtained the best results, irrespective of specimen dimensions. For both glass ionomer materials, the 12 mm x 6 mm matrix led to higher compressive strength results than the 6 mm x 4 mm matrix. A higher variability in results was observed when the glass ionomer cements were used in the larger matrices.Este estudo teve como objetivo avaliar a resistência à compressão de dois cimentos de ionômero de vidro, um convencional (Vitro Fil® - DFL) e outro modificado por resina (Vitro Fil LC® - DFL), utilizando-se dois tamanhos de amostras: uma com 6 mm de altura e 4 mm de diâmetro e outra com 12 mm de altura e 6 mm de diâmetro, seguindo-se a especificação 7489:1986 da ISO e a especificação n. 66 da ANSI/ADA para Cimento Dental de Ionômero de Vidro, respectivamente. Foram confeccionados 10 corpos-de-prova (CP) de cada material para cada tamanho de amostra, totalizando 40 CP. Estes CP foram armazenados em água destilada e ensaiados 24 horas após a manipulação do material, sob uma carga de compressão em uma Máquina de Ensaio Universal (EMIC) a uma velocidade de 0,5 mm/min. Foi realizada a análise estatística para comparação dos resultados utilizando-se o teste Kruskal-Wallis (5%). As médias dos testes de resistência à compressão (MPa) foram: 54,00 ± 6,6 e 105,10 ± 17,3 para a amostra de 12 mm x 6 mm utilizando-se Vitro Fil e Vitro Fil LC, respectivamente, e 46,00 ± 3,8 e 91,10 ± 8,2 para a amostra de 6 mm x 4 mm utilizando-se Vitro Fil e Vitro Fil LC, respectivamente. O cimento de ionômero de vidro modificado por resina obteve melhores resultados independentemente do tamanho do corpo-de-prova. Para ambos os cimentos de ionômero de vidro, a matriz de 12 mm x 6 mm apresentou maiores valores de resistência que a matriz de 6 mm x 4 mm. Uma maior variabilidade nos resultados pôde ser observada quando os cimentos ionoméricos foram utilizados nas matrizes maiores.

André Mallmann; Jane Clei Oliveira Ataíde; Rosa Amoedo; Paulo Vicente Rocha; Letícia Borges Jacques

2007-01-01

351

Compressive strength of glass ionomer cements using different specimen dimensions/ Resistência à compressão de cimentos de ionômero de vidro utilizando-se diferentes tamanhos de corpos-de-prova  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Este estudo teve como objetivo avaliar a resistência à compressão de dois cimentos de ionômero de vidro, um convencional (Vitro Fil® - DFL) e outro modificado por resina (Vitro Fil LC® - DFL), utilizando-se dois tamanhos de amostras: uma com 6 mm de altura e 4 mm de diâmetro e outra com 12 mm de altura e 6 mm de diâmetro, seguindo-se a especificação 7489:1986 da ISO e a especificação n. 66 da ANSI/ADA para Cimento Dental de Ionômero de Vidro, respectivamente. (more) Foram confeccionados 10 corpos-de-prova (CP) de cada material para cada tamanho de amostra, totalizando 40 CP. Estes CP foram armazenados em água destilada e ensaiados 24 horas após a manipulação do material, sob uma carga de compressão em uma Máquina de Ensaio Universal (EMIC) a uma velocidade de 0,5 mm/min. Foi realizada a análise estatística para comparação dos resultados utilizando-se o teste Kruskal-Wallis (5%). As médias dos testes de resistência à compressão (MPa) foram: 54,00 ± 6,6 e 105,10 ± 17,3 para a amostra de 12 mm x 6 mm utilizando-se Vitro Fil e Vitro Fil LC, respectivamente, e 46,00 ± 3,8 e 91,10 ± 8,2 para a amostra de 6 mm x 4 mm utilizando-se Vitro Fil e Vitro Fil LC, respectivamente. O cimento de ionômero de vidro modificado por resina obteve melhores resultados independentemente do tamanho do corpo-de-prova. Para ambos os cimentos de ionômero de vidro, a matriz de 12 mm x 6 mm apresentou maiores valores de resistência que a matriz de 6 mm x 4 mm. Uma maior variabilidade nos resultados pôde ser observada quando os cimentos ionoméricos foram utilizados nas matrizes maiores. Abstract in english The purpose of this study was to evaluate the compressive strength of two glass ionomer cements, a conventional one (Vitro Fil® - DFL) and a resin-modified material (Vitro Fil LC® - DFL), using two test specimen dimensions: One with 6 mm in height and 4 mm in diameter and the other with 12 mm in height and 6 mm in diameter, according to the ISO 7489:1986 specification and the ANSI/ADA Specification No. 66 for Dental Glass Ionomer Cement, respectively. Ten specimens were (more) fabricated with each material and for each size, in a total of 40 specimens. They were stored in distilled water for 24 hours and then subjected to a compressive strength test in a universal testing machine (EMIC), at a crosshead speed of 0.5 mm/min. The data were statistically analyzed using the Kruskal-Wallis test (5%). Mean compressive strength values (MPa) were: 54.00 ± 6.6 and 105.10 ± 17.3 for the 12 mm x 6 mm sample using Vitro Fil and Vitro Fil LC, respectively, and 46.00 ± 3.8 and 91.10 ± 8.2 for the 6 mm x 4 mm sample using Vitro Fil and Vitro Fil LC, respectively. The resin-modified glass ionomer cement obtained the best results, irrespective of specimen dimensions. For both glass ionomer materials, the 12 mm x 6 mm matrix led to higher compressive strength results than the 6 mm x 4 mm matrix. A higher variability in results was observed when the glass ionomer cements were used in the larger matrices.

Mallmann, André; Ataíde, Jane Clei Oliveira; Amoedo, Rosa; Rocha, Paulo Vicente; Jacques, Letícia Borges

2007-09-01

352

Development of a high-performance spacer for cryogenic use. Compressive property and thermal strain of hybrid composites reinforced with high-strength polyethylene and glass fiber; Kyokuteionyo koseino spacer no kaihatsu - kokyodo polyethylene sen`i/glass sen`ikei ichihoko kyoka fukugo zairyo no asshuk  

Energy Technology Data Exchange (ETDEWEB)

As for the unidirectional-fiber reinforced plastics (UD-FRP) of the Dyneema fiber reinforced plastics (DFRP), glass fiber reinforced plastics (GFRP) and DF/GF mixing reinforced plastics (DGFRP) composite materials, the application of cryogenic spacer was thought, and the characteristics of compression and thermal strain are discussed comparatively. Unidirectional hybrid composites reinforced with high-strength polyethylene fiber and glass fiber were prepared to develop a spacer having a low thermal expansion coefficient for cryogenic use. The thermal expansion coefficient and compressive strength of the hybrid composites were measured together with the effect of thermal cycling between room and cryogenic temperatures. Though the hybrid composites showed anisotropy in the thermal expansion coefficient, the coefficient could be calculated simply by the law of mixtures. The thermal expansion coefficient became zero when the ratio between polyethylene and glass fiber volume was 3/7. The compressive strength and thermal expansion coefficient did not change after 5 heat cyclings. The compressive modulus of the hybrid composite was approximately 50 GPa at small strain and then decreased slightly. It was found that the compressive strength of the hybrid composite could be expressed by the law of mixtures. 8 refs., 10 figs.

Yamanaka, A.; Kashima, T. [Toyobo Co., Ltd., Shiga (Japan). Research Institute; Nishijima, S.; Okada, T. [Osaka University, Osaka (Japan). Institute of Science and Industrial Reseach

1997-07-25

353

Efecto del envejecimiento artificial acelerado sobre la resistencia a compresión de resinas compuestas Effect of artificial accelerated aging on compression strength of composite resin  

Directory of Open Access Journals (Sweden)

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.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 each 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.

Priscila Nogueira Gomes; José Carlos Rabelo Ribeiro; Marcos Ribeiro Moysés; Andréa Candido Dias; Sérgio Candido Dias

2009-01-01

354

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)

Full Text Available Abstract in spanish 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 l (more) amina 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 each 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 (more) 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.

Nogueira Gomes, Priscila; Rabelo Ribeiro, José Carlos; Ribeiro Moysés, Marcos; Candido Dias, Andréa; Candido Dias, Sérgio

2009-03-01

355

Laboratory testing of rock and salt samples for static moduli, dynamic moduli, and uniaxial and triaxial compressive strength from the Detten No. 1 (PD-6) Well, G. Friemel No. 1 (PD-5) Well, Mansfield No. 1 (PD-4) Well, and Zeeck No. 1 (PD-7) Well - Palo Duro Basin, Texas: unanalyzed data  

International Nuclear Information System (INIS)

[en] This report contains the laboratory test procedures, graphical representations of the raw data, and test results for the Detten Well No. 1 (Chapters 1 and 2), G. Friemel Well No. 1 (Chapters 3 and 4), Mansfield Well No. 1 (Chapters 5 and 6), and Zeech Well No. 1 (Chapters 7 and 8) in the Permian Basin, Texas. The laboratory tests were performed for static moduli, dynamic moduli, uniaxial compressive strength, and triaxial compressive strength determinations. These data are preliminary. They have been neither analyzed nor evaluated

1984-01-01

356

Performance of industrial by-products in controlled low-strength materials (CLSM).  

UK PubMed Central (United Kingdom)

As the construction industry continues to recognise the importance of sustainable development, technologies such as controlled low-strength material (CLSM) have come to the forefront as viable means of safely and efficiently using by-product and waste materials in infrastructure applications. CLSM, also known as flowable fill, can be defined as an engineered backfill material containing fine aggregates, Portland cement, water and a by-product material. CLSM can provide an economically and technically feasible alternative to conventional fill materials because of potential cost savings related to its unique and often superior technical properties. In this present experimental study, three industrial by-products, namely fly ash (FA), rice husk ash (RHA) and quarry dust (QD), were used as constituent materials in CLSM. Mixture proportions were developed for CLSM containing these industrial by-products and were tested in the laboratory for various properties, such as flowability, unconfined compressive strength (UCS), stress-strain behaviour, density, water absorption and volume changes. Comparison between the two pozzolanic materials, namely FA and RHA, for their potential to produce an effective CLSM has been made. It can be observed from the results that by-product materials such as FA, RHA and QD can be successfully used in CLSM. This successful utilization of by-product materials is important to sustainable development and is the focus of this research.

Nataraja MC; Nalanda Y

2008-01-01

357

An evaluation of aquifer intercommunication between the unconfined and Rattlesnake Ridge aquifers on the Hanford Site  

Energy Technology Data Exchange (ETDEWEB)

During 1986, Pacific Northwest Laboratory conducted a study of a portion of the Rattlesnake Ridge aquifer (confined aquifer) that lies beneath the B Pond - Gable Mountain Pond area of the Hanford Site. The purpose was to determine the extent of intercommunication between the unconfined aquifer and the uppermost regionally extensive confined aquifer, referred to as the Rattlesnake Ridge aquifer. Hydraulic head data and chemical data were collected from the ground water in the study area during December 1986. The hydraulic head data were used to determine the effects caused by water discharged to the ground from B Pond on both the water table of the unconfined aquifer and the potentiometric surface of the confined aquifer. The chemical data were collected to determine the extent of chemical constituents migrating from the unconfined aquifer to the confined aquifer. Analysis of chemical constituents in the Rattlesnake Ridge aquifer demonstrated that communication between the unconfined and confined aquifers had occurred. However, the levels of contaminants found in the Rattlesnake Ridge aquifer during this study were below the DOE Derived Concentration Guides.

Jensen, E.J.

1987-10-01

358

An evaluation of aquifer intercommunication between the unconfined and Rattlesnake Ridge aquifers on the Hanford Site  

International Nuclear Information System (INIS)

During 1986, Pacific Northwest Laboratory conducted a study of a portion of the Rattlesnake Ridge aquifer (confined aquifer) that lies beneath the B Pond - Gable Mountain Pond area of the Hanford Site. The purpose was to determine the extent of intercommunication between the unconfined aquifer and the uppermost regionally extensive confined aquifer, referred to as the Rattlesnake Ridge aquifer. Hydraulic head data and chemical data were collected from the ground water in the study area during December 1986. The hydraulic head data were used to determine the effects caused by water discharged to the ground from B Pond on both the water table of the unconfined aquifer and the potentiomet