WorldWideScience
1

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)

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

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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

2012-01-01

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Dataset of rock mass of the relationship between unconfined compressive strength and various parameters. Set of data  

International Nuclear Information System (INIS)

This report summary the dataset of the relationship between unconfined compressive strength and various parameters of the rock mass described in supporting report 2; repository design and engineering technology of second progress report (H12 report) on research and development for the geological disposal of HLW in Japan. (author)

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

International Nuclear Information System (INIS)

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

6

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

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

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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 correspononducted in order to develop the corresponding experimental correlations. Two hundred indentation tests were also simultaneously conducted on shale fragments extracted from each plug surroundings in order to simulate the caving obtained from reservoir drilled. Results of both tests were correlated using the Minimum Square technique, seeking the best correlation that shall represent result behavior, thus obtaining two 2nd-degree polynomial correlations. Correlation coefficients of 0.6513 were determined for the (IM) - (UCS) correlation and 0.8111 for the (CTF) - (UCS) correlation. This demonstrates that the highest correlation between indentation parameters and (UCS) is obtained with the Critical Transition Force (CTF)

8

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

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English 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 prop [...] erties of materials, including plasticity index and compacted density. The objective of this paper is to investigate the influence of mica on the unconfined compressive strength (UCS) and volumetric changes of a cement-treated gravel material. Free mica (muscovite) was added in predetermined percentages by mass to neat gravel (G5) and specimens subjected to a series of standard laboratory tests. The results show that UCS of greater than 3 MPa is achievable by stabilising less than 5% mica content gravel material with at least 4% cement. Mica content beyond 10% results in very low UCS, even for cement content greater than 6%.

M R, Mshali; A T, Visser.

9

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

International Nuclear Information System (INIS)

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

10

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

2008-01-01

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Determination of Friction Coefficient in Unconfined Compression of Brain Tissue  

OpenAIRE

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 overesti...

Rashid, Badar; Destrade, Michel; Gilchrist, M. D.

2013-01-01

12

Determination of Friction Coefficient in Unconfined Compression of Brain Tissue  

CERN Document Server

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

13

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

Directory of Open Access Journals (Sweden)

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

Mohd Zairul A. Abdul Rahman

2010-01-01

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Elimination of the friction effects in unconfined compression tests of biomaterials and soft tissues.  

Science.gov (United States)

The mechanical properties of biomaterials and soft tissues are determined conventionally using unconfined compression tests. In such tests, frictionless specimen/platen contact in unconfined compression tests has to be assumed in determining the material properties of the materials. Previous theoretical analysis demonstrated, however, that the effects of the friction at the specimen/platen contact interface on the measured stress responses are non-negligible. In this study, a computational approach was proposed to eliminate the effects of friction. The friction coefficient between the specimen and the compression platens is measured first. Using a finite element model, the stress-strain relationship, without the influence of the friction effects, can be derived from the experimental data obtained in conventional unconfined compression tests. In order to validate the proposed approach, unconfined compressive tests of rubber have been performed. PMID:14982344

Wu, J Z; Dong, R G; Smutz, W P

2004-01-01

15

Experimental Study of the Brittle Behavior of Clay shale in Rapid Unconfined Compression  

Science.gov (United States)

The mechanical behavior of clay shales is of great interest in many branches of geo-engineering, including nuclear waste disposal, underground excavations, and deep well drilling. Observations from test galleries (Mont Terri, Switzerland and Bure, France) in these materials have shown that the rock mass response near the excavation is associated with brittle failure processes combined with bedding parallel shearing. To investigate the brittle failure characteristics of the Opalinus Clay recovered from the Mont Terri Underground Research Laboratory, a series of 19 unconfined uniaxial compression tests were performed utilizing servo-controlled testing procedures. All specimens were tested at their natural water content with loading approximately normal to the bedding. Acoustic emission (AE) measurements were utilized to help quantify stress levels associated with crack initiation and propagation. The unconfined compression strength of the tested specimens averaged 6.9 MPa. The crack initiation threshold occurred at approximately 30% of the rupture stress based on analyzing both the acoustic emission measurements and the stress-strain behavior. The crack damage threshold showed large variability and occurred at approximately 70% of the rupture stress.

Amann, Florian; Button, Edward Alan; Evans, Keith Frederick; Gischig, Valentin Samuel; Blümel, Manfred

2011-07-01

16

Viscoelastic characterisation of pig liver in unconfined compression.  

Science.gov (United States)

Understanding and modelling liver biomechanics represents a significant challenge due to the complex nature of this organ. Unfortunately, there is no consensus on liver viscoelastic properties, and results are strongly dependent on sample type and status, adopted testing method, and testing conditions. Standard force-triggered tests (e.g. step response or dynamic mechanical tests) necessitate an initial contact between sample and testing apparatus, which may result in significant pre-stress to very soft and highly hydrated samples. In a previous study we proposed the epsilon dot method (??M): a testing and analysis framework to address the drawbacks of standard mechanical tests. Focusing on ex-vivo unconfined bulk compressive tests, here we use both the ??M and dynamic mechanical analysis (DMA) to derive liver viscoelastic parameters in the region of small strains or the linear viscoelastic region (LVR). As liver samples were visibly deteriorated at the end of frequency sweep tests, a modified approach was adopted to reduce DMA testing times. This approach, termed step-reconstructed DMA (SRDMA), is based on dynamic measurements around specific frequencies and then reconstruction of liver behaviour in the entire frequency range of interest. The instantaneous elastic modulus obtained from SRDMA tests (2.65 ± 0.30 kPa) was significantly higher than that obtained with the ??M (2.04 ± 0.01 kPa). We show that the overestimation of stiffness is due to data acquisition in a local rather than an absolute LVR, highlighting the importance of using a rapid and zero pre-stress approach to characterise very soft and highly hydrated biological tissues. PMID:25017301

Mattei, G; Tirella, A; Gallone, G; Ahluwalia, A

2014-08-22

17

A transversely isotropic biphasic model for unconfined compression of growth plate and chondroepiphysis.  

Science.gov (United States)

Using the biphasic theory for hydrated soft tissues (Mow et al., 1980) and a transversely isotropic elastic model for the solid matrix, an analytical solution is presented for the unconfined compression of cylindrical disks of growth plate tissues compressed between two rigid platens with a frictionless interface. The axisymmetric case where the plane of transverse isotropy is perpendicular to the cylindrical axis is studied, and the stress-relaxation response to imposed step and ramp displacements is solved. This solution is then used to analyze experimental data from unconfined compression stress-relaxation tests performed on specimens from bovine distal ulnar growth plate and chondroepiphysis to determine the biphasic material parameters. The transversely isotropic biphasic model provides an excellent agreement between theory and experimental results, better than was previously achieved with an isotropic model, and can explain the observed experimental behavior in unconfined compression of these tissues. PMID:10412420

Cohen, B; Lai, W M; Mow, V C

1998-08-01

18

Analysis of effects of friction on the deformation behavior of soft tissues in unconfined compression tests.  

Science.gov (United States)

Frictionless specimen/platen contact in unconfined compression tests has traditionally been assumed in determining material properties of soft tissues via an analytical solution. In the present study, the suitability of this assumption was examined using a finite element method. The effect of the specimen/platen friction on the mechanical characteristics of soft tissues in unconfined compression was analyzed based on the published experimental data of three different materials (pigskin, pig brain, and human calcaneal fat). The soft tissues were considered to be nonlinear and viscoelastic; the friction coefficient at the contact interface between the specimens and platens was assumed to vary from 0.0 to 0.5. Our numerical simulations show that the tissue specimens are, due to the specimen/platen friction, not compressed in a uniform stress/strain state, as has been traditionally assumed in analytical analysis. The stress of the specimens obtained with the specimen/platen friction can be greater than those with the frictionless specimen/platen contact by more than 50%, even in well-controlled test conditions. PMID:14672579

Wu, John Z; Dong, Ren G; Schopper, Aaron W

2004-01-01

19

A fibril-network-reinforced biphasic model of cartilage in unconfined compression.  

Science.gov (United States)

Cartilage mechanical function relies on a composite structure of a collagen fibrillar network entrapping a proteoglycan matrix. Previous biphasic or poroelastic models of this tissue, which have approximated its composite structure using a homogeneous solid phase, have experienced difficulties in describing measured material responses. Progress to date in resolving these difficulties has demonstrated that a constitutive low that is successful for one test geometry (confined compression) is not necessarily successful for another (unconfined compression). In this study, we hypothesize that an alternative fibril-reinforced composite biphasic representation of cartilage can predict measured material responses and explore this hypothesis by developing and solving analytically a fibril-reinforced biphasic model for the case of uniaxial unconfined compression with frictionless compressing platens. The fibrils were considered to provide stiffness in tension only. The lateral stiffening provided by the fibril network dramatically increased the frequency dependence of disk rigidity in dynamic sinusoidal compression and the magnitude of the stress relaxation transient, in qualitative agreement with previously published data. Fitting newly obtained experimental stress relaxation data to the composite model allowed extraction of mechanical parameters from these tests, such as the rigidity of the fibril network, in addition to the elastic constants and the hydraulic permeability of the remaining matrix. Model calculations further highlight a potentially important difference between homogeneous and fibril-reinforced composite models. In the latter type of model, the stresses carried by different constituents can be dissimilar, even in sign (compression versus tension) even though strains can be identical. Such behavior, resulting only from a structurally physiological description, could have consequences in the efforts to understand the mechanical signals that determine cellular and extracellular biological responses to mechanical loads in cartilage. PMID:10396701

Soulhat, J; Buschmann, M D; Shirazi-Adl, A

1999-06-01

20

Heterogeneous three-dimensional strain fields during unconfined cyclic compression in bovine articular cartilage explants.  

Science.gov (United States)

Articular cartilage provides critical load-bearing and tribological properties to the normal function of diarthrodial joints. The unique properties of cartilage, as well as heterogeneous deformations during mechanical compression, are due to the nonuniform microstructural organization of tissue components such as collagens and proteoglycans. A new cartilage deformation by tag registration (CDTR) technique has been developed by the authors to determine heterogeneous deformations in articular cartilage explants. The technique uses a combination of specialized MRI methods, a custom cyclic loading apparatus, and image processing software. The objective of this study was to use the CDTR technique to document strain patterns throughout the volume of normal bovine articular cartilage explants during cyclic unconfined compression at two physiologically-relevant applied normal stress levels (1.29 and 2.57 MPa). Despite simple uniaxial cyclic compressive loading with a flat, nonporous indenter, strain patterns were heterogeneous. Strains in the thickness direction (E(yy)) were compressive, varied nonlinearly with depth from the articular surface from a maximum magnitude of 11% at the articular surface, and were comparable despite a 2-fold increase in applied normal stress. Strains perpendicular to the thickness direction (E(xx) and E(zz)) were tensile, decreased linearly with depth from the articular surface from a maximum of 7%, and increased in magnitude 2.5-fold with a 2-fold increase in applied normal stress. Shear strains in the transverse plane (E(xz)) were approximately zero while shear strains in the other two planes were much larger and increased in magnitude with depth from the articular surface, reaching maximum magnitudes of 2% at the articular cartilage-subchondral bone interface. In general, strain patterns indicated that cartilage osteochondral explants exhibited depth-dependent nonisotropic behavior during uniaxial cyclic loading. These results are useful in verifying constitutive formulations of articular cartilage during cyclic unconfined compression and in characterizing the micromechanical environment likely experienced by individual chondrocytes throughout the tissue volume. PMID:15972257

Neu, C P; Hull, M L; Walton, J H

2005-11-01

21

A comparison of cartilage stress-relaxation models in unconfined compression: QLV and stretched exponential in combination with fluid flow.  

Science.gov (United States)

Cartilage exhibits nonlinear viscoelastic behaviour. Various models have been proposed to explain cartilage stress relaxation, but it is unclear whether explicit modelling of fluid flow in unconfined compression is needed. This study compared Fung's quasi-linear viscoelastic (QLV) model with a stretched-exponential model of cartilage stress relaxation and examined each of these models both alone and in combination with a fluid-flow model in unconfined compression. Cartilage explants were harvested from bovine calf patellofemoral joints and equilibrated in tissue culture for 5 days before stress-relaxation testing in unconfined compression at 5% nominal strain. The stretched exponential models fit as well as the QLV models. Furthermore, the average stretched exponential relaxation time determined by this model lies within the range of experimentally measured relaxation times for extracted proteoglycan aggregates, consistent with the hypothesis that the stretched exponential model represents polymeric mechanisms of cartilage viscoelasticity. PMID:22149471

June, Ronald K; Fyhrie, David P

2013-01-01

22

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

International Nuclear Information System (INIS)

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

23

Material properties in unconfined compression of gelatin hydrogel for skin tissue engineering applications.  

Science.gov (United States)

Gelatin (Gel) has been reported as a promising candidate in tissue engineering owing to its easy availability, biocompatibility, and biodegradability. Gel hydrogel is of potential to be cross-linked with different materials to enhance their biocompatibility for cell culture for tissue engineering applications. The mechanical properties of this versatile material, however, have not been thoroughly determined. In this study, the linear elastic (Young's modulus and maximum stress) and non-linear hyperelastic (hyperelastic coefficients) mechanical properties of prepared hydrogels at different contents of Gel (wt%) were measured, and its Young's modulus was compared with that of skin tissue. The prepared cylindrical Gel hydrogels were subjected to a series of unconfined compression tests. The hyperelastic strain energy density function was calibrated using the compressive experimental data. The potential ability of the Yeoh hyperelastic constitutive equation, which has been proposed as the best material model to represent the non-linear behavior of hydrogels, was verified using finite element (FE) simulations. The results revealed that the Young's modulus and maximum stress of hydrogels are increased by the addition of Gel. The highest Young's modulus (81 kPa) and maximum stress (24 kPa) were observed for hydrogels with 15 wt% Gel. Results also showed that the hydrogels with a relatively lower content (7.5 wt%) for skin tissue engineering. The Yeoh material model was closely fitted with the experimental data and could be used in further biomechanical simulations of the hydrogels. The experimental results were also compared well with those predicted by the FE models. The results of this study might have implications not only for the understanding of the mechanical properties of Gel hydrogel but also for the fabrication of polymeric substrate materials suitable for skin tissue engineering applications. PMID:24988278

Karimi, Alireza; Navidbakhsh, Mahdi

2014-12-01

24

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

25

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

26

Saturated-unsaturated flow in a compressible leaky-unconfined aquifer  

Science.gov (United States)

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

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

2012-06-01

27

Compressive Strength of Autoclaved Aerated Concrete Blockwork  

OpenAIRE

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

Daou, Y. A.

2001-01-01

28

Effect of non-uniform thickness of samples in stress relaxation tests under unconfined compression of samples of articular discs.  

Science.gov (United States)

A precise information of the biomechanical properties of soft tissues is required to develop a suitable simulation model, with which the distribution of stress and strain in the complex structures can be estimated. Many soft tissues have been mechanically characterized by stress relaxation tests under unconfined or confined compression. In general, full-thickness samples are extracted to reduce the damage in the tissue as much as possible. However, it is not guaranteed that these samples have a uniform thickness or, in other words, planar parallel faces. In particular, in the articular disc of the temporomandibular joint, many studies can be found testing full-thickness samples for which that thickness is known to be non-uniform, while making the assumption of uniaxial stress state to extract the mechanical properties from those tests. That inaccuracy may have a strong influence in some cases and needs a profound revision. The main goal of this work is to quantify the error committed in that assumption and the influence of the variation of thickness on that error in a particular test: stress relaxation tests under unconfined compression. Based on this error and defining an allowable tolerance, a criterion is established to reject samples depending on their aspect ratio. PMID:24581817

Commisso, Maria S; Martínez-Reina, Javier; Mayo, Juana; Domínguez, Jaime; Tanaka, Eiji

2014-04-11

29

Saturated-unsaturated flow to a well with storage in a compressible unconfined aquifer  

Science.gov (United States)

Mishra and Neuman (2010) developed an analytical solution for flow to a partially penetrating well of zero radius in a compressible unconfined aquifer that allows inferring its saturated and unsaturated hydraulic properties from responses recorded in the saturated and/or unsaturated zones. Their solution accounts for horizontal as well as vertical flows in each zone. It represents unsaturated zone constitutive properties in a manner that is at once mathematically tractable and sufficiently flexible to provide much improved fits to standard constitutive models. In this paper we extend the solution of [2010] to the case of a finite diameter pumping well with storage; investigate the effects of storage in the pumping well and delayed piezometer response on drawdowns in the saturated and unsaturated zones as functions of position and time; validate our solution against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the [1980]- [1976] model; use our solution to analyze 11 transducer-measured drawdown records from a seven-day pumping test conducted by University of Waterloo researchers at the Canadian Forces Base Borden in Ontario, Canada; validate our parameter estimates against manually-measured drawdown records in 14 other piezometers at Borden; and compare (a) our estimates of aquifer parameters with those obtained on the basis of all these records by [2008], (b) on the basis of 11 transducer-measured drawdown records by [2007], (c) our estimates of van Genuchten-Mualem parameters with those obtained on the basis of laboratory drainage data from the site by [1992], and (d) our corresponding prediction of how effective saturation varies with elevation above the initial water table under static conditions with a profile based on water contents measured in a neutron access tube at a radial distance of about 5 m from the center of the pumping well. We also use our solution to analyze 11 transducer-measured drawdown records from a 7 day pumping test conducted by University of Waterloo researchers at the Canadian Forces Base Borden in Ontario, Canada. We validate our parameter estimates against manually measured drawdown records in 14 other piezometers at Borden. We compare our estimates of aquifer parameters with those obtained on the basis of all these records by Moench (2008) and on the basis of 11 transducer-measured drawdown records by Endres et al. (2007), and we compare our estimates of van Genuchten-Mualem parameters with those obtained on the basis of laboratory drainage data from the site by Akindunni and Gillham (1992); finally, we compare our corresponding prediction of how effective saturation varies with elevation above the initial water table under static conditions with a profile based on water contents measured in a neutron access tube at a radial distance of about 5 m from the center of the pumping well.

Mishra, Phoolendra Kumar; Neuman, Shlomo P.

2011-05-01

30

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

2007-06-01

31

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

32

Compressive Strength of Fibre Reinforced Concrete  

OpenAIRE

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

Jelus?ic?, Matjaz?

2009-01-01

33

(Finite) statistical size effects on compressive strength.  

Science.gov (United States)

The larger structures are, the lower their mechanical strength. Already discussed by Leonardo da Vinci and Edmé Mariotte several centuries ago, size effects on strength remain of crucial importance in modern engineering for the elaboration of safety regulations in structural design or the extrapolation of laboratory results to geophysical field scales. Under tensile loading, statistical size effects are traditionally modeled with a weakest-link approach. One of its prominent results is a prediction of vanishing strength at large scales that can be quantified in the framework of extreme value statistics. Despite a frequent use outside its range of validity, this approach remains the dominant tool in the field of statistical size effects. Here we focus on compressive failure, which concerns a wide range of geophysical and geotechnical situations. We show on historical and recent experimental data that weakest-link predictions are not obeyed. In particular, the mechanical strength saturates at a nonzero value toward large scales. Accounting explicitly for the elastic interactions between defects during the damage process, we build a formal analogy of compressive failure with the depinning transition of an elastic manifold. This critical transition interpretation naturally entails finite-size scaling laws for the mean strength and its associated variability. Theoretical predictions are in remarkable agreement with measurements reported for various materials such as rocks, ice, coal, or concrete. This formalism, which can also be extended to the flowing instability of granular media under multiaxial compression, has important practical consequences for future design rules. PMID:24733930

Weiss, Jérôme; Girard, Lucas; Gimbert, Florent; Amitrano, David; Vandembroucq, Damien

2014-04-29

34

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.

Sahin Zaimoglu, A.

2007-12-01

35

Temperature dependence of uniaxial compressive strength of Hnilec granite  

OpenAIRE

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

36

A microfabricated platform for high-throughput unconfined compression of micropatterned biomaterial arrays.  

Science.gov (United States)

High-throughput screening techniques for cellular response are often unable to account for several factors present in the in vivo environment, many of which have been shown to modulate cellular response to the screened parameter. Culture in three-dimensional biomaterials and active mechanical stimulation are two such factors. In this work, we integrate these microenvironmental parameters into a versatile microfabricated device, capable of simultaneously applying a range of cyclic, compressive mechanical forces to cells encapsulated in an array of micropatterned biomaterials. The fabrication techniques developed here are broadly applicable to the integration of three-dimensional culture systems in complex multilayered polymeric microdevices. Compressive strains ranging from 6% to 26% were achieved simultaneously across the biomaterial array. As a first demonstration of this technology, nuclear and cellular deformation in response to applied compression was assessed in C3H10T1/2 mouse mesenchymal stem cells encapsulated within poly(ethylene glycol) hydrogels. Biomaterial, cellular, and nuclear deformations were non-linearly related. Parametric finite element simulations suggested that this phenomenon was due to the relative stiffness differences between the hydrogel matrix and that of the encapsulated cell and nucleus, and to strain stiffening of the matrix with increasing compression. This complex mechanical interaction between cells and biomaterials further emphasizes the need for high-throughput approaches to conduct mechanically active experiments in three-dimensional culture. PMID:19819010

Moraes, Christopher; Wang, GongHao; Sun, Yu; Simmons, Craig A

2010-01-01

37

Predicting mechanical properties of enhanced performance concrete using compressive strength  

OpenAIRE

Mechanical properties of concrete are usually evaluated from compressive strength test results. Extensive literature, codes and regulations recommend the prediction of mechanical properties such as splitting and flexural tensile strength using the compressive strength of cylindrical specimens. These expressions are not related with the type of concrete and, generally, are only a function of the cylindrical compressive strength. It is the objective of this research work to in...

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

2004-01-01

38

Compressive and diametral tensile strengths of current adhesive luting agents.  

Science.gov (United States)

Strength parameters greatly influence the selection of luting agents. This study compared the compressive and diametral tensile strengths of six classes of new adhesive luting agents (ALAs) with zinc phosphate as the controls. The 11 materials tested were prepared according to the manufacturers' instructions for use as luting agents. Mean compressive and diametral strengths and standard errors were calculated for each luting agent (n = 10). Analysis of variance was computed (p liquid glass ionomer ALAs, an encapsulated glass ionomer ALA, a composite resin-glass ionomer hybrid ALA, and the composite resin ALAs demonstrated significantly greater compressive and diametral strengths than the zinc phosphate cements. PMID:8391577

White, S N; Yu, Z

1993-06-01

39

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

40

Studies of fiber-matrix adhesion on compression strength  

Science.gov (United States)

A study was initiated on the effect of the matrix polymer and the fiber matrix bond strength of carbon fiber polymer matrix composites. The work includes tests with micro-composites, single ply composites, laminates, and multi-axial loaded cylinders. The results obtained thus far indicate that weak fiber-matrix adhesion dramatically reduces 0 degree compression strength. Evidence is also presented that the flaws in the carbon fiber that govern compression strength differ from those that determine fiber tensile strength. Examination of post-failure damage in the single ply tests indicates kink banding at the crack tip.

Bascom, Willard D.; Nairn, John A.; Boll, D. J.

1991-01-01

41

Compressive strength and compressive fatigue limit of conventional and high viscosity posterior resin composites.  

Science.gov (United States)

The purpose of this study was to compare the compressive strengths and compressive fatigue limits of three posterior composite resins (Filtek P-60, Surefil and Prodigy Condensable) and a universal restorative composite (Z-100). Cylindrical specimens (8 mm in length x 4 mm in diameter) were used. The dynamic test was performed using the staircase method, and the ratio between compressive fatigue limit and compressive resistance was also calculated (n = 15). The compressive strength and compressive fatigue limit data were analyzed by Anova and Tukeys test. The Z-100 composite demonstrated higher compression strength (307.20 MPa) than Surefil (266.93 MPa) and Prodigy Condensable (222.08 MPa). The resistance of Filtek P-60 (270.44 MPa) was similar to the resistances of Z-100 and Surefil, while Prodigy Condensable presented the lowest compressive strength. In the compressive fatigue limit tests, Filtek P-60 demonstrated a higher value (184.20 MPa) than Prodigy Condensable (155.50 MPa). Surefil (165.74 MPa) and Z-100 (161.22 MPa) presented limits similar to those of Filtek P-60 and Prodigy Condensable. The compressive fatigue limit/compressive strength ratio was 70.01% for Prodigy Condensable, 68.11% for Filtek P-60, 62.09% for Surefil and 52.48% for Z-100. It was concluded that the Z-100 universal composite was more sensitive to the dynamic test than the high viscosity materials. PMID:16491255

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

2005-01-01

42

Compressive strength and rheology of environmentally-friendly binders  

Directory of Open Access Journals (Sweden)

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

Juan Manuel Lizarazo Marriaga

2010-07-01

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

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

Directory of Open Access Journals (Sweden)

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

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

2013-05-01

45

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

Science.gov (United States)

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

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

2011-01-01

46

Static strength of gold compressed up to 127 GPa  

International Nuclear Information System (INIS)

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

47

(Finite) statistical size effects on compressive strength  

OpenAIRE

The larger structures are, the lower their mechanical strength. Already discussed by Leonardo da Vinci and Edmé Mariotte several centuries ago, size effects on strength remain of crucial importance in modern engineering for the elaboration of safety regulations in structural design or the extrapolation of laboratory results to geophysical field scales. Under tensile loading, statistical size effects are traditionally modeled with a weakest-link approach. One of its prominent results is a pre...

Weiss, Je?ro?me; Girard, Lucas; Gimbert, Florent; Amitrano, David; Vandembroucq, Damien

2014-01-01

48

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

2010-12-01

49

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 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

Effect Of Salt Water On Compressive Strength Of Concrete  

OpenAIRE

In this research work, the effect of salt water on the compressive strength of concrete was investigated. This paper therefore presents the result and findings of an experimental research on the effect of salt water on compressive strength of concrete. For this concrete cubes were cast using fresh wi and salt water for a design mix of M-30 1:1.8:3.31 by weight of concrete, and 0.45 water- cement ratio. Half of concrete cubes were cast and cured with fresh water and remaining ha...

Preeti Tiwari; Rajiv Chandak

2014-01-01

51

Relationship between the Compressive and Tensile Strength of Recycled Concrete  

International Nuclear Information System (INIS)

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

52

Goose`s eggshell strength at compressive loading  

Directory of Open Access Journals (Sweden)

Full Text Available The paper deals with the study of the goose eggs behaviour under compressive loading between two plates using testing device TIRATEST. The influences of the loading orientation as well as the effect of compressive velocity are studied. 226 eggs from Landes geese were chosen for the experiment. Eggs have been loaded between their poles and in the equator plane. Five different compressive velocities (0.0167, 0.167, 0.334, 1.67 and 5 mm.s-1 were used. The increase in rupture force with loading rate was observed for loading in all direction (along main axes. Dependence of the rupture force on loading rate was quantifies and described. The highest rupture force was obtained when the eggs were loaded along their axes of symmetry (X-axis. Compression in the equator plane (along the Z-axis required the least compressive force to break the eggshells. The eggshell strength was described by the rupture force, specific rupture deformation and by the absorbed energy. The rupture force is highly dependent on compression speeds. The dependence of the rupture force on the compression velocity can be described by a power function. The same is valid for the rate dependence of the energy absorbed by the egg up to the fracture. The rate sensitivity of the Goose's eggshells strength is significantly higher than that reported for the hen's eggs

Šárka Nedomová

2014-02-01

53

The compressive modulus and strength of saturated calcium sulphate dihydrate cements: implications for testing standards.  

Science.gov (United States)

Calcium sulphate-based bone cement is a bone filler with proven biological advantages including biodegradability, biocompatibility and osteoconductivity. Mechanical properties of such brittle ceramic cements are frequently determined using the testing standard designed for ductile acrylic cements. The aims of the study were (1) to validate the suitability of this common testing protocol using saturated calcium sulphate dihydrate (CSD), and (2) to compare the strength and effective modulus of non-saturated and saturated CSD, in order to determine the changes in the mechanical behavior of CSD upon saturation. Unconfined compression tests to failure were performed on 190 cylindrical CSD samples. The samples were divided into four groups having different saturation levels (saturated, non-saturated) and end conditions (capped and non-capped). Two effective moduli were calculated per sample, based on the deformations measured using the machine platens and a sample-mounted extensometer. The effective moduli of non-saturated groups were found to be independent of the end conditions. The saturated and capped group showed no difference in the effective moduli derived from different measurement methods, while the saturated and non-capped group showed a significant difference between the machine platen- and extensometer-derived moduli. Strength and modulus values were significantly lower for saturated samples. It was assumed that the existence of water in saturated CSD alters the mechanical response of the material due to the changes in chemical and physical behaviors. These factors are considered to play important roles to decrease the shear strength of CSD. It was proposed that the reduction in CSD shear strength evokes local deformation at the platen-sample boundary, affecting the strength and effective moduli derived from the experiments. The results of this study highlighted the importance of appropriate and consistent testing methods when determining the mechanical properties of saturated ceramic cements. PMID:24603215

Koh, Ilsoo; López, Alejandro; Helgason, Benedikt; Ferguson, Stephen J

2014-06-01

54

Evaluation of Adhesive and Compressive Strength of Glass Ionomer Cements  

OpenAIRE

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

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

2011-01-01

55

Compression Strength of Composite Primary Structural Components  

Science.gov (United States)

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

Johnson, Eric R.

1998-01-01

56

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

OpenAIRE

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

Prof Nanak J Pamnani, Dr A. K. Verma

2013-01-01

57

Compressive strength and hydration processes of concrete with recycled aggregates  

International Nuclear Information System (INIS)

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

58

Unfired clay bricks – moisture properties and compressive strength  

DEFF Research Database (Denmark)

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

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

2002-01-01

59

Compressive strength and hydration processes of concrete with recycled aggregates  

Energy Technology Data Exchange (ETDEWEB)

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

Koenders, Eduardus A.B., E-mail: e.a.b.koenders@coc.ufrj.br [COPPE-UFRJ, Rio de Janeiro (Brazil); Microlab, Delft University of Technology (Netherlands); Pepe, Marco, E-mail: mapepe@unisa.it [Dept. of Civil Engineering, University of Salerno (Italy); Martinelli, Enzo, E-mail: e.martinelli@unisa.it [Dept. of Civil Engineering, University of Salerno (Italy)

2014-02-15

60

Prediction of Compressive Strength of Concrete using Artificial Neural Network  

Directory of Open Access Journals (Sweden)

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

Wankhade M W

2013-07-01

61

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

2010-05-01

62

Compression Strength of Sulfur Concrete Subjected to Extreme Cold  

Science.gov (United States)

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

Grugel, Richard N.

2008-01-01

63

Compressive strength and durability properties of ceramic wastes based concrete  

OpenAIRE

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

Torgal, Fernando Pacheco; Jalali, Said

2010-01-01

64

Estimating compressive strength of concrete by mortar testing  

OpenAIRE

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

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

2005-01-01

65

Compressive Strength and Microstructure of Sugar Cane Bagasse Ash Concrete  

OpenAIRE

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

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

2014-01-01

66

Compressive Strength and Microstructure of Sugar Cane Bagasse Ash Concrete  

Directory of Open Access Journals (Sweden)

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

Asma Abd Elhameed Hussein

2014-03-01

67

Effect of Coarse Aggregate Size on the Compressive Strength and the Flexural Strength of Concrete Beam  

Directory of Open Access Journals (Sweden)

Full Text Available Concrete structures deflect, crack, and loose stiffness when subjected to external load. Loss of flexural strength of concrete is largely responsible for cracks in structure. In reinforced concrete structures, the mix proportions of the materials of the concrete and aggregate type determine the compressive strength while the composite action of concrete and steel reinforcement supplies the flexural strength. In occasion of loss of stiffness, steel reinforcement no longer supports flexural stresses; concrete in turn is subjected to flexure. The compressive strength and flexural strength therefore play a crucial role. Effect of varying coarse aggregate size on the flexural and compressive strengths of concrete beam was investigated. Concrete cubes and beams were produced in accordance with BS 1881-108 (1983 and ASTM C293 with varying aggregate sizes 9.0mm, 13.2mm, 19mm, 25.0mm and 37.5mm, using a standard mould of internal dimension 150x150x150 for the concrete cubes and a mould of internal dimension of 150 x 150 x 750mm for the reinforced concrete beam. The water cement ratio was kept at 0.65 with a mix proportion of 1:2:4. The specimen produced were all subjected to curing in water for 28days and were all tested to determine the compressive strength and flexural strength using Universal Testing Machine. Compressive strength of cubes is 21.26N/mm2 , 23.41N/mm2 , 23.66N/mm2 , and 24.31N/mm2 for coarse aggregate sizes 13.2mm, 19mm, 25.0mm and 37.5mm respectively. That of flexural strength of test beams is 4.93N/mm2 , 4.78N/mm2 , 4.53N/mm2 , 4.49N/mm2 , 4.40N/mm2 respectively. In conclusion, concrete to be used mostly to resist flexural stresses should be made of finer coarse aggregates.

S.O. Ajamu

2015-01-01

68

Toroidal, compression and vortical dipole strengths in 124Sn  

International Nuclear Information System (INIS)

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

69

Toroidal, compression, and vortical dipole strengths in 124Sn  

CERN Document Server

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

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

2012-01-01

70

Flow strength of tantalum under ramp compression to 250?GPa  

International Nuclear Information System (INIS)

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

71

INTRA-RING COMPRESSION STRENGTH OF LOW DENSITY HARDWOODS  

Scientific Electronic Library Online (English)

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

Audrey, Zink-Sharp; Carlile, Price.

72

Compressive strength and microstructural properties of lightweight high-strength cement mortar reinforced with eloxal  

International Nuclear Information System (INIS)

An investigation was carried out to evaluate the results of the compressive strength of high-strength lightweight eloxal reinforced cement mortar subject to short term loads. An experimental method similar to the one proposed by the author on chilled aluminum-quartz reinforced metal matrix composite was used. Eloxal (in the solid slag form) is a waste obtained during the production of aluminum in the plant. It is mainly of aluminum oxide, SiO2, CaO, MgO and other substances. It is a hard substance, having sufficient strength with additive properties and bonds very rapidly. Eloxal reinforced cement mortar in the present investigation are tested for its compressive and microstructural behavior. Data were obtained pertaining to compressive strength, role of moisture and drying effects. Deformation under compressive load were studied to provide insight into the internal behavior and failure mechanism of lightweight eloxal reinforced cement mortar. To analyze the mode of failure under compression, distribution of eloxal particles in cement mortar and the deformation behavior, several optical and scanning electron microscope photographs were taken to study the mechanism. Results of the tests of eloxal reinforced cement mortar are compared with unreinforced cement mortar and information obtained else where in earlier tests of normal weight cement mortar. Structural composite materials offer an excellent opportunity to produce components that achieve weight savingsuce components that achieve weight savings and improved properties. The eloxal particles (dispersoid) added to cement mortar in the present investigation is varied from 20 to 40 wt% in steps of 10 wt%. The resulting composite blocks cast were tested for their properties

73

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

2010-01-01

74

Compressive strength and hydrolytic stability of fly ash based geopolymers  

Directory of Open Access Journals (Sweden)

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

Nikoli? Irena

2013-01-01

75

High strain rate compression and tension characterization of high strength (automotive) sheet steels  

International Nuclear Information System (INIS)

Compression and tension split Hopkinson bar techniques are used to characterize high strength automotive sheet steels at strain rates of 500/s and 1000/s. Compression and tension data on two representative steel grades are given. There are differences in the measured compression and tension flow stresses for both the steels. The effect of strain rate and steel strength on these differences is discussed

76

Compressive strength and hardness of metal matrix syntactic foams  

Energy Technology Data Exchange (ETDEWEB)

Six types of metal matrix syntactic foams (MMSFs) were produced by pressure infiltration technique. The foams were investigated by upsetting tests at increased (220{sup 0}C) and at room (25{sup 0}C) temperature. The parameters were the constituents of the composites and the aspect ratio (height-diameter ratio, H/D) of the specimens. The characteristic properties were: the compressive strength, the fracture strain, the structural stiffness of the foams and the absorbed energy. The strength, the strain and the energy were decreased while the stiffness was increased by increasing the H/D. Increased temperature caused {approx}25 % drop in the strength and in the stiffness. Macrohardness, depth sensitive and dynamic hardness tests were also performed on MMSF blocks: macrohardness is a structural property and independent from the matrix material. The depth sensitive hardness is sensitive to the deformation capability of the matrix and to a possible change reaction. The dynamic hardnesses of the MMSFs were higher than the hardness of the matrices and this is a microballoon related property.

Orbulov, I N; Nemeth, A [Department of Materials Science and Engineering, Budapest University of Technology and Economics, Goldmann Gy. ter 3., Budapest, H-1111 (Hungary); Dobranszky, J, E-mail: orbulov@gmail.co [Research Group for Metals Technology of the Hungarian Academy of Sciences, Goldmann Gy. ter 3., Budapest, H-1111 (Hungary)

2010-07-01

77

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

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, enhancement of compressive strength of OPC paste is main objective. 1% and 4% of sawdust powder has been blended to Ordinary Portland Cement (OPC paste. The compressive strength has been measured on 7, 28, 56 and 90 days. The micro properties of OPC paste has been investigated by using X-ray diffraction (XRD and Atomic Force Microscopy (AFM. The best quantity for replacement of sawdust is 1%. The mixture of 4% sawdust to OPC paste has also been improved compressive strength of concrete. The cellulose-Ibeta presences in saw dust, has been modified the surface roughness and hydration of OPC paste, and leads to enhancement of compressive strength of concrete. The compressive strength of OPC paste has been stabilized with increase of age, due to pozzolanic actions. The compressive strength of OPC has been decreased with increase sawdust contents.

Abdoullah Namdar

2014-02-01

78

Compressive strength after blast of sandwich composite materials.  

Science.gov (United States)

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

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

2014-05-13

79

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

OpenAIRE

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

Juan Manuel Lizarazo Marriaga; José Gabriel Gómez Cortés

2010-01-01

80

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

OpenAIRE

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

Li, Yi-hai; Franssen, Jean-marc

2011-01-01

81

Influence of pore structure on compressive strength of cement mortar.  

Science.gov (United States)

This paper describes an experimental investigation into the pore structure of cement mortar using mercury porosimeter. Ordinary Portland cement, manufactured sand, and natural sand were used. The porosity of the manufactured sand mortar is higher than that of natural sand at the same mix proportion; on the contrary, the probable pore size and threshold radius of manufactured sand mortar are finer. Besides, the probable pore size and threshold radius increased with increasing water to cement ratio and sand to cement ratio. In addition, the existing models of pore size distribution of cement-based materials have been reviewed and compared with test results in this paper. Finally, the extended Bhattacharjee model was built to examine the relationship between compressive strength and pore structure. PMID:24757414

Zhao, Haitao; Xiao, Qi; Huang, Donghui; Zhang, Shiping

2014-01-01

82

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

DEFF Research Database (Denmark)

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

Hasholt, Marianne Tange; Jespersen, Morten H. Seneka

2010-01-01

83

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

Directory of Open Access Journals (Sweden)

Full Text Available 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.

Juan Manuel Lizarazo Marriaga

2010-04-01

84

Numerical analysis of the spacer grids' compression strength  

International Nuclear Information System (INIS)

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

85

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

2008-01-01

86

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

International Nuclear Information System (INIS)

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

87

Compressive strength, microstructure and hydration products of hybrid alkaline cements  

Scientific Electronic Library Online (English)

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

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

2014-08-01

88

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

89

Multiple Regression Model for Compressive Strength Prediction of High Performance Concrete  

OpenAIRE

A mathematical model for the prediction of compressive strength of high performance concrete was performed using statistical analysis for the concrete data obtained from experimental work done in this study. The multiple non-linear regression model yielded excellent correlation coefficient for the prediction of compressive strength at different ages (3, 7, 14, 28 and 91 days). The coefficient of correlation was 99.99% for each strength (at each age). Also, the model gives high correlat...

Zain, M. F. M.; Abd, S. M.

2009-01-01

90

Developing a forecasting model of concrete compressive strength using relevance vector machines  

OpenAIRE

We analyze results of two experiments that tested effect of adding Silica on the compressive strength of concrete at early stage and after long period. The two experiments evaluated different silica/cement ratios for different mixing periods. Adding Silica to concrete mix produce high early strength material which is highly desirable in airports and highways. More than 90 samples of different silica/cement ratios are tested for compressive strength at 3 and 28 days. Test results showed high e...

Mohammad Awwad

2014-01-01

91

The estimation of compressive strength of normal and recycled aggregate concrete  

OpenAIRE

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 ...

Jankovi? Ksenija; Nikoli? Dragan 2; Bojovi? Dragan; Lon?ar Ljiljana; Romakov Zoran

2011-01-01

92

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

2011-01-01

93

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

Directory of Open Access Journals (Sweden)

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

Sudin M.A.S.

2014-03-01

94

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

OpenAIRE

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 fi...

Muntohar, A. S.

2009-01-01

95

Experimental study on ultimate strength and strain behavior of concrete under biaxial compressive stresses  

International Nuclear Information System (INIS)

The purpose of this investigation was to study the ultimate strength failure mode and deformation behavior of concrete under short-term biaxial compressive stresses, as an aid to design and analyze the concrete structures subjected to multiaxial compression such as prestressed or reinforced concrete vessel structures. The experimental work on biaxial compression was carried out on the specimens of three mix proportions and different ages with 10cm x 10cm x 10cm cubic shape in a room controlled at 200C. The results are summarized as follows. (1) To minimize the surface friction between specimens and loading platens, the pads of teflon sheets coated with silicone grease were used. The coefficient of friction was measured and was 3 percent on the average. (2) The test data showed that the strength of the concrete subjected to biaxial compression increased as compared to uniaxial compressive strength, and that the biaxial strength increase was mainly dependent on the ratio of principal stresses, and it was hardly affected by mix proportions and ages. (3) The maximum increase of strength, which occurred at the stress ratio of approximately sigma2/sigma1 = 0.6, was about 27 percent higher than the uniaxial strength of concrete. (4) The ultimate strength in case of biaxial compression could be approximated by the parabolic equation. (Kako, I.)

96

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

OpenAIRE

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 ...

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

2006-01-01

97

Effect of luting media on the compressive strengths of two types of all-ceramic crown.  

Science.gov (United States)

This study evaluated the effect of selected luting media on the compressive strength of two types of all-ceramic crown. Tooth preparation was standardized; each preparation had a shoulder width of approximately 1.2 mm, and all internal preparation angles were rounded. Hi-Ceram and Dicor all-ceramic crowns were fabricated and cemented into the preparations with zinc phosphate, glass-ionomer, or composite resin cement. Coronal compressive fracture strengths were determined, using a set of unrestored teeth as a control. There were no statistically significant differences among the mean compressive strengths of the three luting media, and there was no statistically significant difference between the mean compressive strength of Dicor and that of the natural tooth control. PMID:8234646

McCormick, J T; Rowland, W; Shillingburg, H T; Duncanson, M G

1993-06-01

98

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

Science.gov (United States)

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

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

2014-01-01

99

Determine the compressive strength of calcium silicate bricks by combined nondestructive method.  

Science.gov (United States)

The paper deals with the application of combined nondestructive method for assessment of compressive strength of calcium silicate bricks. In this case, it is a combination of the rebound hammer method and ultrasonic pulse method. Calibration relationships for determining compressive strength of calcium silicate bricks obtained from nondestructive parameter testing for the combined method as well as for the L-type Schmidt rebound hammer and ultrasonic pulse method are quoted here. Calibration relationships are known for their close correlation and are applicable in practice. The highest correlation between parameters from nondestructive measurement and predicted compressive strength is obtained using the SonReb combined nondestructive method. Combined nondestructive SonReb method was proved applicable for determination of compressive strength of calcium silicate bricks at checking tests in a production plant and for evaluation of bricks built in existing masonry structures. PMID:25276864

Brozovsky, Jiri

2014-01-01

100

Face compression yield strength of the copper-Inconel composite specimen  

International Nuclear Information System (INIS)

A new equation for the face compression yield strength of copper-Inconel composite material has been derived. Elastic-plastic finite element analyses were also made for composite specimens with various aspect ratios to examine the edge effect of the specimen. According to the results of both the new equation and the analyses, the face compression yield strength of the composite should be decreased by about 25% from the value obtained with Becker's equation

101

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

International Nuclear Information System (INIS)

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

102

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

OpenAIRE

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

Jiri Brozovsky

2014-01-01

103

Fracture Energy of High-Strength Concrete in Compression  

OpenAIRE

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

Dahl, H.; Brincker, Rune

2011-01-01

104

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

105

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

Science.gov (United States)

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

Nagwani, Naresh Kumar; Deo, Shirish V

2014-01-01

106

Differences between the tensile and compressive strengths of bovine tibial trabecular bone depend on modulus.  

Science.gov (United States)

The conflicting conclusions regarding the relationship between the tensile and compressive strengths of trabecular bone remain unexplained. To help resolve this issue, we compared measurements of the tensile (n = 22) and compressive (n = 22) yield strengths, and yield strains, of trabecular bone specimens taken from 38 bovine proximal tibiae. We also studied how these failure properties depended on modulus and apparent density. To enhance accuracy, trabecular orientation was controlled, and each specimen had a reduced section where strains were measured with a miniature extensometer. We found that the mean yield strength was 30% lower for tensile loading. However, the difference between individual values of the tensile and compressive strengths increased linearly with increasing modulus and density, being negligible for low moduli, but substantial for high moduli. By contrast, both the tensile and compressive yield strains were independent of modulus and density, with the yield strain being 30% lower for tensile loading. Thus, the difference between the tensile and compressive strengths of bovine tibial trabecular bone depends on the modulus, but the difference between yield strains does not. This phenomenon may explain in part that conflicting conclusions reached previously on the tensile and compressive strengths of trabecular bone since the mean modulus has varied among different studies. Realizing that our data pertain only directly to bovine tibial trabecular bone for longitudinal loading, our results nevertheless suggest that failure parameters based on strains may provide more powerful and general comparisons of the failure properties for trabecular bone than measures based on stress. PMID:7929463

Keaveny, T M; Wachtel, E F; Ford, C M; Hayes, W C

1994-09-01

107

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

DEFF Research Database (Denmark)

The influence of the characteristics or the microstructure of Portland cement on compressive strength up to 28 days has been statistically investigated by application of partial least square (PLS) analysis. The main groups of characteristics were mineralogy and superficial microstructure represented by curves from X-ray diffraction analysis and differential thermogravimetric analysis, as well as particle size distributions. PLS gave maximum explained variance in compressive strength at 1, 2, 7 and 28 days of 93%, 90%, 79% and 67%, respectively. The high explained variance makes the prediction of the compressive strength up to 28 days from the characteristics reliable. The prediction ability makes it possible in this case to predict strength from cement characteristics and vice versa. Such a prediction can be utilized to design a cement to achieve target strength performance.

Svinning, K.; HØskuldsson, Agnar

2008-01-01

108

Prediction of potential compressive strength of Portland clinker from its mineralogy  

DEFF Research Database (Denmark)

Based on a statistical model first applied for prediction of compressive strength up to 28 d from the microstructure of Portland cement, potential compressive strength of clinker has been predicted from its mineralogy. The prediction model was evaluated by partial least squares regression. The mineralogy was described by patterns from X-ray diffraction analysis in the 20-regions 29.88-30.70 degrees and 32.90-34.10 degrees (using CuK alpha-radiation). It has been shown that prediction of potential compressive strength of clinker up to 28 d from the observed variation in the mineralogy gave a significant variation of the strength at both 1 and 28 d. Sensitivity analysis based on simulation, optimisation and prediction made it possible to study the influence of the mineralogy on the strength in more detail.

Svinning, K.; HØskuldsson, Agnar

2010-01-01

109

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

Scientific Electronic Library Online (English)

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

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

110

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

111

Experimental Study of Confined Low-, Medium- and High-Strength Concrete Subjected to Concentric Compression  

Directory of Open Access Journals (Sweden)

Full Text Available An experimental study of 23 low-, medium- and high-strength concrete columns is presented in this paper. Square-confined concrete columns without longitudinal reinforcement were designed, and tested under concentric axial compression. The columns were made of concrete with a compressive strength ranging between 30 MPa and 70 MPa. The test parameters in the study are concrete compressive strengths and confining steel properties, i.e. spacing, volumetric ratios and configurations. The effects of these parameters on the strength and ductility of square-confined concrete were evaluated. Of the specimens tested in this study, the columns made with higher-strength concrete produced less strength enhancement and ductility than those with lower-strength concrete. The steel configurations were found to have an important role in governing the strength and ductility of the confined high-strength concrete. Moreover, several models of strength enhancement for confined concrete available in the literature turned out to be quite accurate in predicting the experimental results.

Antonius

2012-11-01

112

Estimation of hardness and compressive strength of SP 100 aluminum powder epoxy  

International Nuclear Information System (INIS)

In this study, we performed experimental tests on five SP 100 aluminum powder epoxy specimens with several after curing conditions in order to estimate their hardness with temperature and compressive strength. In the surface hardness test, it was found that the higher the after curing temperature, the higher was the hardness. In particular, it was found that the hardness of the specimens in cases 3 and 4 was much higher than in the other cases. In addition, in the compression tests carried out to evaluate the compressive strength, it was found that the specimens showed relatively similar stiffness and strength with after curing, and specimens with no after curing showed compression stress strain curves similar to those of thermoplastic resins

113

Estimation of hardness and compressive strength of SP 100 aluminum powder epoxy  

Energy Technology Data Exchange (ETDEWEB)

In this study, we performed experimental tests on five SP 100 aluminum powder epoxy specimens with several after curing conditions in order to estimate their hardness with temperature and compressive strength. In the surface hardness test, it was found that the higher the after curing temperature, the higher was the hardness. In particular, it was found that the hardness of the specimens in cases 3 and 4 was much higher than in the other cases. In addition, in the compression tests carried out to evaluate the compressive strength, it was found that the specimens showed relatively similar stiffness and strength with after curing, and specimens with no after curing showed compression stress strain curves similar to those of thermoplastic resins.

Han, Jeong Young [Pusan National Univ., Busan (Korea, Republic of); Kim, Myung Hun [Korea Institute of Footwear and Leather Technology, Busan (Korea, Republic of); Kang, Sung Soo [Jeonju Univ., Jeonju (Korea, Republic of)

2012-09-15

114

Improving the Bearing Strength of Sandy Loam Soil Compressed Earth Block Bricks Using Sugercane Bagasse Ash  

Directory of Open Access Journals (Sweden)

Full Text Available The need for affordable and sustainable alternative construction materials to cement in developing countries cannot be underemphasized. Compressed Earth Bricks have gained acceptability as an affordable and sustainable construction material. There is however a need to boost its bearing capacity. Previous research show that Sugarcane Bagasse Ash as a soil stabilizer has yielded positive results. However, there is limited research on its effect on the mechanical property of Compressed Earth Brick. This current research investigated the effect of adding 3%, 5%, 8% and 10% Sugarcane Bagasse Ash on the compressive strength of compressed earth brick. The result showed improvement in its compressive strength by 65% with the addition of 10% Sugarcane Bagasse Ash.

Ramadhan W. Salim

2014-06-01

115

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

International Nuclear Information System (INIS)

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

116

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

2011-01-01

117

INTRA-RING COMPRESSION STRENGTH OF LOW DENSITY HARDWOODS  

OpenAIRE

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 propertie...

Audrey Zink-Sharp; Carlile Price

2006-01-01

118

Numerical validation of compressive strength prediction for hollow concrete blocks  

OpenAIRE

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

Barbosa, C. S.; Hanai, J. B.; Lourenc?o, Paulo B.

2010-01-01

119

On the compressive strength prediction for concrete masonry prisms  

OpenAIRE

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

Barbosa, C. S.; Lourenc?o, Paulo B.; Hanai, J. B.

2010-01-01

120

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

2013-07-01

121

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

Directory of Open Access Journals (Sweden)

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

Hongying Dong

2014-12-01

122

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

123

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

International Nuclear Information System (INIS)

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

124

Residual Compressive Strength of Laterized Concrete Subjected to Elevated Temperatures  

OpenAIRE

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...

Brooks, Robert M.

2010-01-01

125

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.

Canan Kose

2011-01-01

126

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)

127

An investigation of the compressive strength of Kevlar 49/epoxy composites  

Science.gov (United States)

Tests were performed to evaluate the effect of a wide range of variables including matrix properties, interface properties, fiber prestressing, secondary reinforcement, and others on the ultimate compressive strength of Kevlar 49/epoxy composites. Scanning electron microscopy is used to assess the resulting failure surfaces. In addition, a theoretical study is conducted to determine the influence of fiber anisotropy and lack of perfect bond between fiber and matrix on the shear mode microbuckling. The experimental evaluation of the effect of various constituent and process characteristics on the behavior of these unidirectional composites in compression did not reveal any substantial increase in strength. However, theoretical evaluations indicate that the high degree of fiber anisotropy results in a significant drop in the predicted stress level for internal instability. Scanning electron microscope data analysis suggests that internal fiber failure and smooth surface debonding could be responsible for the measured low compressive strengths.

Kulkarni, S. V.; Rosen, B. W.; Rice, J. S.

1975-01-01

128

A Study of Compressive Strength Characteristics of Laterite Sand Hollow Blocks  

Directory of Open Access Journals (Sweden)

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

Abiodun Olanipekun

2007-01-01

129

Dynamic compressive and tensile strengths of spark plasma sintered alumina  

Science.gov (United States)

Fully dense submicron grain size alumina samples were manufactured from alumina nano-powder using Spark Plasma Sintering and tested in two kinds of VISAR-instrumented planar impact tests. In the first kind, samples were loaded by 1-mm tungsten impactors, accelerated to a velocity of about 1 km/s. These tests were aimed at studying the Hugoniot elastic limit (HEL) of Spark Plasma Sintering (SPS)-processed alumina and the decay, with propagation distance, of the elastic precursor wave. In the tests of the second kind, alumina samples of 3-mm thickness were loaded by 1-mm copper impactors accelerated to 100-1000 m/s. These tests were aimed at studying the dynamic tensile (spall) strength of the alumina specimens. The tensile fracture of the un-alloyed alumina shows a monotonic decline of the spall strength with the amplitude of the loading stress pulse. Analysis of the decay of the elastic precursor wave allowed determining the rate of the irreversible (inelastic) strains in the SPS-processed alumina at the initial stages of the shock-induced inelastic deformation and to clarify the mechanisms responsible for the deformation. The 1-% addition of Cr2O3 decreases the HEL of the SPS-processed alumina by 5-% and its spall strength by 50% but barely affects its static properties.

Girlitsky, I.; Zaretsky, E.; Kalabukhov, S.; Dariel, M. P.; Frage, N.

2014-06-01

130

Dynamic compressive and tensile strengths of spark plasma sintered alumina  

International Nuclear Information System (INIS)

Fully dense submicron grain size alumina samples were manufactured from alumina nano-powder using Spark Plasma Sintering and tested in two kinds of VISAR-instrumented planar impact tests. In the first kind, samples were loaded by 1-mm tungsten impactors, accelerated to a velocity of about 1?km/s. These tests were aimed at studying the Hugoniot elastic limit (HEL) of Spark Plasma Sintering (SPS)-processed alumina and the decay, with propagation distance, of the elastic precursor wave. In the tests of the second kind, alumina samples of 3-mm thickness were loaded by 1-mm copper impactors accelerated to 100–1000?m/s. These tests were aimed at studying the dynamic tensile (spall) strength of the alumina specimens. The tensile fracture of the un-alloyed alumina shows a monotonic decline of the spall strength with the amplitude of the loading stress pulse. Analysis of the decay of the elastic precursor wave allowed determining the rate of the irreversible (inelastic) strains in the SPS-processed alumina at the initial stages of the shock-induced inelastic deformation and to clarify the mechanisms responsible for the deformation. The 1-% addition of Cr2O3 decreases the HEL of the SPS-processed alumina by 5-% and its spall strength by 50% but barely affects its static properties.

131

Dynamic compressive and tensile strengths of spark plasma sintered alumina  

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-06-28

132

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

OpenAIRE

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

Rami?rez-rico, J.; Bautista, M. A.; Marti?nez-ferna?ndez, Julia?n; Singh, M.

2011-01-01

133

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

134

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

2005-01-01

135

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

International Nuclear Information System (INIS)

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

136

Effect of resin-based material combination on the compressive and the flexural strength.  

Science.gov (United States)

The mechanical properties, elasticity and compressive strength, of restorative materials play a crucial role during mastication for clinical performance of materials in particular stress bearing areas at posterior regions. This in vitro study was objected to evaluate the changes in the compressive and flexural strength of tooth-coloured resin-based dental restorations placed on flowable composites. Specimens in the control group were produced in cylindrical form for testing compressive strength and in quadrangular prism form for flexural strength test. Tetric Ceram, Charisma, Surefil, Admira and two compomers; Dyract AP and Compoglass F in test group specimens were fabricated by placing the control materials on different flowables. The material combinations were as follows: Tetric Ceram/Tetric Flow Charisma/Flowline, Surefil/Dyract Flow, Admira/Admira Flow, Dyract AP/Dyract Flow, Compoglass F/Compoglass Flow. Compressive strength values were measured at the Instron Testing Machine with a cross-head speed of 10 mm min(-1) while flexural strength were determined in three-point bending with a cross-head speed of 1 mm min(-1). One-way anova and Tukey's multiple comparison tests were performed for the statistical analysis. The flexural strength values of Tetric Ceram/Tetric Flow (135.9 +/- 3.2), Charisma/Flowline (120.4 +/- 5.6) and Compoglass F/Compoglass Flow (108.2 +/- 5.2) combinations were statistically greater than Tetric Ceram (110.8 +/- 10.5), Charisma (95.3 +/- 5.3) and Compoglass F (86.9 +/- 4.9). The results of the present study support the idea that the placement of flowable composite as a liner under the resin-based composite restoratives increase the flexural strength. PMID:15641978

Gömeç, Y; Dörter, C; Dabanoglu, A; Koray, F

2005-02-01

137

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

International Nuclear Information System (INIS)

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 tion 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)

138

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

Science.gov (United States)

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

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

2013-09-01

139

Uniaxial compression tests on diesel contaminated frozen silty soil specimens  

International Nuclear Information System (INIS)

Results of a uniaxial, unconfined compression test on artificial diesel-contaminated and uncontaminated frozen silty soils are discussed. The testing program involved 59 specimens. The results show that for the same fluid content, diesel contamination reduced the strength of the frozen specimens by increasing the unfrozen water content. For example, in specimens containing 50 per cent diesel oil of the fluid content by weight the maximum strength was reduced by 95 per cent compared to the strength of an uncontaminated specimen. Diesel contamination was also shown to contribute to the slippage between soil particles by acting as a lubricant, thus accelerating the loss of compressive strength.13 refs., 18 figs

140

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

Science.gov (United States)

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

Hiel, Clement; Brinson, H. F.

1993-01-01

141

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

142

Strength and Permeability of Stabilized Peat Soil  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this study was to analyze the unconfined compressive strength and initial permeability of peat soil stabilized by a mixture of Ordinary Portland cement, ground granulated blast furnace slag and siliceous sand. An understanding of the stabilized soil properties is of great importance for the design of deep stabilization in peat land for highway construction. Significant evidence on the positive effects of the admixture at stabilizing peat soil was discovered from laboratory testing investigation of the study. Results from the investigation indicated that addition of the admixture was able to increase unconfined compressive strength and reduce initial permeability of the stabilized soil as compared to those of untreated peat.

L.S. Wong

2008-01-01

143

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

International Nuclear Information System (INIS)

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

144

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2006-02-01

145

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

2013-02-01

146

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

2012-11-01

147

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

Directory of Open Access Journals (Sweden)

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

MD NOR ATAN

2011-12-01

148

Effect of Cement Stabilized Kaolin Subgrade on Strength Properties  

OpenAIRE

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

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

2014-01-01

149

Strength and Permeability of Stabilized Peat Soil  

OpenAIRE

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

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

2008-01-01

150

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

151

Analyses of spacer grids compression strength and fuel assemblies structural behavior  

International Nuclear Information System (INIS)

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

152

A low cost method of testing compression-after-impact strength of composite laminates  

Science.gov (United States)

A method was devised to test the compression strength of composite laminate specimens that are much thinner and wider than other tests require. The specimen can be up to 7.62 cm (3 in) wide and as thin as 1.02 mm (.04 in). The best features of the Illinois Institute of Technology Research Institute (IITRI) fixture are combined with an antibuckling jig developed and used at the University of Dayton Research Institute to obtain a method of compression testing thin, wide test coupons on any 20 kip (or larger) loading frame. Up to 83 pct. less composite material is needed for the test coupons compared to the most commonly used compression-after-impact (CAI) tests, which calls for 48 ply thick (approx. 6.12 mm) test coupons. Another advantage of the new method is that composite coupons of the exact lay-up and thickness of production parts can be tested for CAI strength, thus yielding more meaningful results. This new method was used to compression test 8 and 16 ply laminates of T300/934 carbon/epoxy. These results were compared to those obtained using ASTM standard D 3410-87 (Celanese compression test). CAI testing was performed on IM6/3501-6, IM7/SP500 and IM7/F3900. The new test method and associated fixture work well and is a valuable asset to MSFC's damage tolerance program.

Nettles, Alan T.

1991-01-01

153

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

OpenAIRE

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

Marandi, S. M.; Bagheripour, M. H.; Rahgozar, R.; Zare, H.

2008-01-01

154

Compressive strength of structural concrete made with locally available coarse aggregates  

International Nuclear Information System (INIS)

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

155

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

2010-08-01

156

Determination of composition of pozzolanic waste mixtures with optimized compressive strength  

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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

2004-06-01

157

Determination of composition of pozzolanic waste mixtures with optimized compressive strength  

Scientific Electronic Library Online (English)

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 propert [...] ies 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.

2004-06-01

158

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

International Nuclear Information System (INIS)

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

159

Column and Plate Compressive Strengths of Aircraft Structural Materials: Extruded 24S-T Aluminum Alloy  

Science.gov (United States)

Column and plate compressive strengths of extruded 24S-T aluminum alloy were determined both within and beyond the elastic range from tests of thin-strip columns and local-instability tests of H-, Z-,and channel-section columns. These tests are part of an extensive research investigation to provide data on the' structural strength of various aircraft materials. The results are presented in the form of curves and charts that are suitable for use in the design and analysis of aircraft structures.

Heimerl, George J.; Roy, J Albert

1945-01-01

160

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

OpenAIRE

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

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

2010-01-01

161

Tensile strength and internal stress determination in salt compacts by diametrical and axial compression tests  

International Nuclear Information System (INIS)

Due to the brittle character of the material an indirect method (diametrical and axial compression testing) was adopted for tensile strength determination. Two lots of compacts were prepared from salt powder, by pressing it in steel dyes by means of a hydraulic press. For uniaxial tests, cylindrical compacts were used. Biaxial tests were done on disk-shaped compacts, each disk having a diametrical V-shaped cut on one of its plane areas. The punches used for compression tests, were designed to obtain a ratio of 1.2 between their curvature radius and sample radius. At the same time with the tensile strength, the stress intensity factor (KIC and KIIC values) has been obtained. The results obtained are in good agreement with the mechanical properties of the salt, previously reported. (Authors)

162

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

International Nuclear Information System (INIS)

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

163

Influence of Fly Ash on the Compressive Strength of Foamed Concrete at Elevated Temperature  

Directory of Open Access Journals (Sweden)

Full Text Available Foamed concrete is a lightweight concrete that is widely used in the construction industry recently. This study was carried out to investigate the influence of fly ash as a cement replacement material to the residual compressive strength of foamed concrete subjected to elevated temperature. For this study, the foamed concrete density was fixed at 1300 kg/m3 and the sand-cement ratio and water-cement was set at 1:2 and 0.45, respectively. The samples were prepared and tested at the age of 28 days. Based on the results, it has been found that with 25% inclusion of fly ash, the percentage of compressive strength loss was decreased by 3 – 50%.

Ahmad H.

2014-01-01

164

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

Scientific Electronic Library Online (English)

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

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

2014-08-01

165

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

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

Vijaykumar H.K

2014-07-01

166

A Finite Element Analysis for Predicting the Residual Compression Strength of Impact-Damaged Sandwich Panels  

Science.gov (United States)

A simple analysis method has been developed for predicting the residual compression strength of impact-damaged sandwich panels. The method is tailored for honeycomb core-based sandwich specimens that exhibit an indentation growth failure mode under axial compression loading, which is driven largely by the crushing behavior of the core material. The analysis method is in the form of a finite element model, where the impact-damaged facesheet is represented using shell elements and the core material is represented using spring elements, aligned in the thickness direction of the core. The nonlinear crush response of the core material used in the analysis is based on data from flatwise compression tests. A comparison with a previous analysis method and some experimental data shows good agreement with results from this new approach.

Ratcliffe, James G.; Jackson, Wade C.

2008-01-01

167

A Finite Element Analysis for Predicting the Residual Compressive Strength of Impact-Damaged Sandwich Panels  

Science.gov (United States)

A simple analysis method has been developed for predicting the residual compressive strength of impact-damaged sandwich panels. The method is tailored for honeycomb core-based sandwich specimens that exhibit an indentation growth failure mode under axial compressive loading, which is driven largely by the crushing behavior of the core material. The analysis method is in the form of a finite element model, where the impact-damaged facesheet is represented using shell elements and the core material is represented using spring elements, aligned in the thickness direction of the core. The nonlinear crush response of the core material used in the analysis is based on data from flatwise compression tests. A comparison with a previous analysis method and some experimental data shows good agreement with results from this new approach.

Ratcliffe, James G.; Jackson, Wade C.

2008-01-01

168

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English 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). Bov [...] ine teeth molds were used for simulating a clinical ultrasonic excitation. The data were submitted to three-way ANOVA and Tukey tests (P

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

2008-03-01

169

Validation of analytical and continuum numerical methods for estimating the compressive strength of masonry  

OpenAIRE

The advances in computational mechanics witnessed in the last decades have made available a large variety of numerical tools. Sophisticated non-linear models are now standard in several finite element based programs. This paper addresses the ability of continuum numerical methods, based on plasticity and cracking, as well as on analytical methods to provide reliable estimations of masonry compressive strength. In addition, a discussion on the load transfer between masonry components is presen...

Lourenc?o, Paulo B.; Henriques, J. Pina

2006-01-01

170

Studies on Compressive Strength Of Ternary Blended Concretes At Different Water Binder Ratios  

OpenAIRE

The Present experimental investigation is carried out in the optimisation of a Ternary Blended Cementitious system based on Ordinary Portland Cement (OPC)/ Fly Ash / Micro Silica for the development of high- performance concrete. Compressive Strength of Ternary Blended Concrete at the ages of 28, 90, 180 days for various combinations of Fly Ash and Micro Silica mixes were investigated. Fly Ash was replaced by 0%, 15% and 20% along with Micro Silica of 0%, 5%, and 10%. All the mixes were st...

Audinarayana, D.

2013-01-01

171

Compression behaviour and shear strength characteristics of a natural silty clay sedimented in the laboratory  

OpenAIRE

?The compression behaviour, shear strength characteristics, and material properties of dense slurries and soft settled beds of natural fine-grained sediments were studied experimentally. Slurries of varying initial density, initial height, and pore fluid salinity were settled one-dimensionally, by self-weight, in the laboratory. Settling behaviour was studied in terms of slurry appearance, particle segregation, height of surface versus time, sediment surface and element se...

Bowden, Robert Kirk

1988-01-01

172

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

OpenAIRE

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

Turel, Marko

2006-01-01

173

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

Directory of Open Access Journals (Sweden)

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

Hanifi B?N?C?

2000-03-01

174

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

OpenAIRE

This study investigates the compressive and flexural strengths of self-compacting concrete incorporating raw rice husk ash, individually and in combination with other types of mineral additives, as partial cement replacement. The additives paired with raw rice husk ash were fine limestone powder, pulverized fuel ash and silica fumes. The mix design was based on the rational method where solid constituents were fixed while water and superplasticizer contents were adjusted to produce optimum vi...

MD NOR ATAN; HANIZAM AWANG

2011-01-01

175

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

Directory of Open Access Journals (Sweden)

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

Ravindra N. Thakur

2009-06-01

176

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

Directory of Open Access Journals (Sweden)

Full Text Available Normal 0 7.8 ? 0 2 false false false EN-US ZH-CN X-NONE This study presents the analysis and the benefits from using Micronized Biomass Silica (MBS of rice husk which comprises of high content of silica. MBS was generated from controlled burning of the husk into off-white biomass silica ash and crushing the ash into micronized size. Concrete samples containing various percentages of MBS were tested for workability, compressive strength and also water permeability performances. It was found that the optimum percentage of MBS added to the concrete that lead to good performance of concrete in terms of compressive strength and water permeability was 12%. The compressive strength increased up to 43% when 12% of MBS was added to the concrete after 90 days period. Increasing the content of MBS exceeding the optimum percentage showed inferior performance of the concrete. It indicates that the pozzolanic reaction properties of MBS could improve the compressive strength and water permeability of concrete. /* Style Definitions */ table.MsoNormalTable {mso-style-name:????; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; 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","serif";}

Suraya Hani Adnan

2012-10-01

177

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

OpenAIRE

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 asepti...

Saghiri, Mohammad A.; Garcia-godoy, Franklin; Asatourian, Armen; Lotfi, Mehrdad; Banava, Sepideh; Khezri-boukani, Kaveh

2013-01-01

178

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

International Nuclear Information System (INIS)

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

179

Effects of fiber, matrix, and interphase on carbon fiber composite compression strength  

Science.gov (United States)

The major goal of this project was to obtain basic information on compression failure properties of carbon fiber composites. To do this, we investigated fiber effects, matrix effects, and fiber/matrix interface effects. Using each of nine fiber types, we prepared embedded single-fiber specimens, single-ply specimens, and full laminates. From the single-fiber specimens, in addition to the standard fragmentation test analysis, we were able to use the low crack density data to provide information about the distribution of fiber flaws. The single-ply specimens provided evidence of a correlation between the size of kink band zones and the quality of the interface. Results of the laminate compression experiments mostly agreed with the results from single-ply experiments, although the ultimate compression strengths of laminates were higher. Generally, these experiments showed a strong effect of interfacial properties. Matrix effects were examined using laminates subjected to precracking under mixed-mode loading conditions. A large effect of precracking conditions on the mode 1 toughness of the laminates was found. In order to control the properties of the fiber/matrix interface, we prepared composites of carbon fiber and polycarbonate and subjected these to annealing. The changes in interfacial properties directly correlated with changes in compression strength.

Nairn, John A.; Harper, Sheila I.; Bascom, Willard D.

1994-01-01

180

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

Science.gov (United States)

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

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

2015-02-01

181

Deflagration explosion of an unconfined fuel vapor cloud  

International Nuclear Information System (INIS)

In the reported study, explosions are produced by injecting a small amount of liquefied petroleum gas (LPG) into air. The ignition and subsequent evolution of the explosion of the unconfined vapor cloud are observed by the simultaneous use of direct photographs and pressure recording. The intensity of the compression waves generated by unconfined combustion are modeled on the basis of the solution of the conservation equations for the flow associated with a spherically symmetric expanding piston. The obtained results are compared with the measurements. It is pointed out that the development of unconfined fuel vapor cloud explosions can be divided into two stages, including a deflagration propagating in premixed gases, which is followed by a diffusion flame promoted by buoyancy and convection. The experimental result from the pressure measurement is found to be quantitatively consistent with the result obtained from the spherical piston model

182

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

Science.gov (United States)

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

Hidayat, Irpan; Siauwantara, Alice

2014-03-01

183

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

Science.gov (United States)

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

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

2015-01-01

184

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

2008-03-01

185

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

OpenAIRE

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

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

2012-01-01

186

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

Science.gov (United States)

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

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

2014-09-01

187

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, Ebbe Nils; Thomsen, Jesper Skovhus

1999-01-01

188

[Study on fatigue toughness of dental materials. 1. Compressive strength on various luting cements and composite resin cores].  

Science.gov (United States)

In this study, we investigated compressive strength of various luting cements and composite resin cores in both dry and wet condition, and then influences of repeating load on compressive strength in wet condition of distilled water at 37 degrees C. As frequency of repeating load increased, compressive strength of all materials decreased. It means that the repeated load cycling test used in this study is adequate for evaluating durability of various dental materials. The results were as follows: 1. In the condition of no loading in both dry and wet condition, resin cement indicated the highest compressive strength of all cements examined and was followed by glass ionomer cement, zinc phosphate cement and polycarboxylate cement. Glass ionomer cement was notably influenced in wet condition. 2. After 10,000 cycles of loading in wet condition, resin cement indicated the highest compressive strength again and was followed by glass ionomer cement, polycarboxylate cement and zinc phosphate cement. In particular, compressive strength of zinc phosphate cement decreased remarkably. 3. In the condition of no loading, visible light-cured composite resin core was superior to chemical one. Visible light one was notably influenced in wet condition. 4. After 10,000 cycles of loading, visible light-cured composite resin core was superior to chemical one. PMID:2489748

Miyamoto, S; Takagawa, T; Nozaki, A; Yanaka, N; Nakamura, Y; Imai, Y; Noguchi, S; Hanamura, N

1989-08-01

189

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

Scientific Electronic Library Online (English)

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

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

190

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

Directory of Open Access Journals (Sweden)

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

Ortega, J. M.

2014-03-01

191

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

Directory of Open Access Journals (Sweden)

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

Ahmadian Khoshemehr Leila

2009-09-01

192

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

OpenAIRE

The purpose of this study was to compare the compressive strengths and compressive fatigue limits of three posterior composite resins (Filtek P-60, Surefil and Prodigy Condensable) and a universal restorative composite (Z-100). Cylindrical specimens (8 mm in length x 4 mm in diameter) were used. The dynamic test was performed using the staircase method, and the ratio between compressive fatigue limit and compressive resistance was also calculated (n = 15). The compressive strength and compres...

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

2005-01-01

193

Influence of Fly Ash on the Compressive Strength of Foamed Concrete at Elevated Temperature  

OpenAIRE

Foamed concrete is a lightweight concrete that is widely used in the construction industry recently. This study was carried out to investigate the influence of fly ash as a cement replacement material to the residual compressive strength of foamed concrete subjected to elevated temperature. For this study, the foamed concrete density was fixed at 1300 kg/m3 and the sand-cement ratio and water-cement was set at 1:2 and 0.45, respectively. The samples were prepared and tested at the age of 28 d...

Ahmad H.; Wahid N.; Rahman M.F.A.; Karim N.A.

2014-01-01

194

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

International Nuclear Information System (INIS)

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

195

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

196

Nondestructive testing of the low-level radioactive waste drums for uni-axial compressive strength and free liquid content  

International Nuclear Information System (INIS)

This paper summarizes the nondestructive test to determine the uni-axial compressive strength and free water content of solidified low level radioactive waste. The uni-axial compressive strength is determined by ultrasonic wave propagation speed, and the results are compared with those of compressive tests. Three methods of detecting the surface free water by ultrasonic testing are established, the ultrasonic wave speed, wave form and pulse height are used to determine the existence and amount of the surface free liquid. Possible difficulties are discussed. (author)

197

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

Directory of Open Access Journals (Sweden)

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

Yu Chang-Li

2015-06-01

198

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.

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

199

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

International Nuclear Information System (INIS)

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

200

Uniaxial compression test series on Bullfrog Tuff  

International Nuclear Information System (INIS)

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 10-5 sec-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

201

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.

2006-09-01

202

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

Directory of Open Access Journals (Sweden)

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

Felix F. Udoeyo

2010-02-01

203

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

204

Compressive strength and microstructural characteristics of class C fly ash geopolymer  

Energy Technology Data Exchange (ETDEWEB)

Geopolymers prepared from a class C fly ash (CFA) and a mixed alkali activator of sodium hydroxide and sodium silicate solution were investigated. A high compressive strength was obtained when the modulus of the activator viz., molar ratio of SiO{sub 2}/Na{sub 2}O was 1.5, and the proper content of this activator as evaluated by the mass proportion of Na{sub 2}O to CFA was 10%. The compressive strength of these samples was 63.4 MPa when they were cured at 75{sup o}C for 8 h followed by curing at 23{sup o}C for 28 d. In FTIR spectroscopy, the main peaks at 1036 and 1400 cm{sup -1} have been attributed to asymmetric stretching of Al-O/Si-O bonds, while those at 747 cm{sup -1} are due to the Si-O-Si/Si-O-Al bending band. The main geopolymeric gel and calcium silicate hydrate (C-S-H) gel co-exist and bond some remaining unreacted CFA spheres as observed in XRD and SEM-EXDA. The presence of gismondine (zeolite) was also observed in the XRD pattern.

Xiaolu Guo; Huisheng Shi; Warren A. Dick [Key Laboratory of Advanced Civil Engineering Materials (Tongji University), Shanghai (China)

2010-02-15

205

Mechanical behavior of the human lumbar spine. II. Fatigue strength during dynamic compressive loading.  

Science.gov (United States)

Seventeen cadaveric human lumbar motion segments from eight spines were cyclically loaded in vitro under axial compression. Loading frequency and magnitude were chosen to simulate rigorous activity within an in vivo physiological level. The load magnitude was determined as a percentage of the ultimate compressive load, the latter estimated from the bone mineral content (BMC) of lumbar vertebrae determined by dual-photon absorptiometry. Following testing, the degree of macroscopic disc degeneration was assessed and the type of fracture in each specimen was determined from serial sagittal sections. Fractures were found in all but one specimen. Three types of fractures were formed: the node of Schmorl and Junghanns (type I), central endplate fracture (type II), and a crush or burst fracture (type III). The results suggested that type I fractures were predominantly associated with segments with normal discs, type II fractures were found primarily in segments with moderately degenerated discs, and type III fractures were associated with segments that failed on the first cycle. Segment stiffness and fatigue strength (cycles to failure) were correlated with disc degeneration, age, and segment BMC, the latter an in vivo measure of bone density. Fatigue strength also decreased in proportion to a power coefficient with increasing relative stress (cyclic stress range/ultimate stress). PMID:3681522

Hansson, T H; Keller, T S; Spengler, D M

1987-01-01

206

Long-Term Isothermal Aging Effects on Carbon Fabric-Reinforced PMR-15 Composites: Compression Strength  

Science.gov (United States)

A study was conducted to determine the effects of long-term isothermal thermo-oxidative aging on the compressive properties of T-650-35 fabric reinforced PMR-15 composites. The temperatures that were studied were 204, 260, 288, 316, and 343 C. Specimens of different geometries were evaluated. Cut edge-to-surface ratios of 0.03 to 0.89 were fabricated and aged. Aging times extended to a period in excess of 15,000 hours for the lower temperature runs. The unaged and aged specimens were tested in compression in accordance with ASTM D-695. Both thin and thick (plasma) specimens were tested. Three specimens were tested at each time/temperature/geometry condition. The failure modes appeared to be initiated by fiber kinking with longitudinal, interlaminar splitting. In general, it appears that the thermo-oxidative degradation of the compression strength of the composite material may occur by both thermal (time-dependent) and oxidative (weight-loss) mechanisms. Both mechanisms appear to be specimen-thickness dependent.

Bowles, Kenneth J.; Roberts, Gary D.; Kamvouris, John E.

1996-01-01

207

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

International Nuclear Information System (INIS)

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

208

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

International Nuclear Information System (INIS)

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

209

Repeatability and Reproducibility of Compression Strength Measurements Conducted According to ASTM E9  

Science.gov (United States)

Ten commercial laboratories participated in an interlaboratory study to establish the repeatability and reproducibility of compression strength tests conducted according to ASTM International Standard Test Method E9. The test employed a cylindrical aluminum AA2024-T351 test specimen. Participants measured elastic modulus and 0.2 % offset yield strength, YS(0.2 % offset), using an extensometer attached to the specimen. The repeatability and reproducibility of the yield strength measurement, expressed as coefficient of variations were cv(sub r)= 0.011 and cv(sub R)= 0.020 The reproducibility of the test across the laboratories was among the best that has been reported for uniaxial tests. The reported data indicated that using diametrically opposed extensometers, instead of a single extensometer doubled the precision of the test method. Laboratories that did not lubricate the ends of the specimen measured yield stresses and elastic moduli that were smaller than those measured in laboratories that lubricated the specimen ends. A finite element analysis of the test specimen deformation for frictionless and perfect friction could not explain the discrepancy, however. The modulus measured from stress-strain data were reanalyzed using a technique that finds the optimal fit range, and applies several quality checks to the data. The error in modulus measurements from stress-strain curves generally increased as the fit range decreased to less than 40 % of the stress range.

Luecke, William E.; Ma, Li; Graham, Stephen M.; Adler, Matthew A.

2010-01-01

210

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

Energy Technology Data Exchange (ETDEWEB)

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

Rossi, Paolo, E-mail: paolo.rossi@enea.it [Associazione EURATOM-ENEA sulla Fusione, C.R. Frascati, C.P. 65, 00044 Frascati (Rome) (Italy); Capobianchi, Mario; Crescenzi, Fabio; Massimi, Alberto; Mugnaini, Giampiero; Nardi, Claudio; Pizzuto, Aldo [Associazione EURATOM-ENEA sulla Fusione, C.R. Frascati, C.P. 65, 00044 Frascati (Rome) (Italy); Bettinali, Livio [Consorzio CREATE, Via Claudio 21, 80125 Napoli (Italy); Knaster, Juan [ITER, Route de Vinon-sur-Verdon CS 90 046, 13067, St. Paul-lez-Durance Cedex (France); Rajainmaki, Hannu [FUSION FOR ENERGY, Josep Pla no 2, Torres Diagonal Litoral Edificio B3, 08019 Barcelona (Spain); Evans, David [Advanced Cryogenic Materials, Abingdon, Oxon (United Kingdom)

2011-10-15

211

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

212

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

2004-06-01

213

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

Science.gov (United States)

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

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

2014-01-01

214

The Effect of Different Parameters on the Development of Compressive Strength of Oil Palm Shell Geopolymer Concrete  

Science.gov (United States)

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

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

2014-01-01

215

Mixed-mode fracture criteria for the materials with different yield strengths in tension and compression  

Science.gov (United States)

The Nadai elastic-plastic boundary is introduced to define the core region, instead of a core region with a constant distance r from the crack tip and a core region with the Mises elastic-plastic boundary. Taking into account fracture parameters along the Nadai elastic-plastic boundary, two improved fracture criteria are presented for the two commonly used fracture criteria, the maximum tangential-stress criterion and the minimum strain-energy-density criterion. Using the two improved fracture criteria, the effect of properties of the material with different yield strengths in tension and compression on the mixed-mode crack fracture can be revealed. It is shown by analysis that the fracture of the mixed-mode crack is affected by this kind of property of the material. Many results are given by using the two improved fracture criteria, and they are compared with those obtained by using the commonly used mixed-mode fracture criteria.

Yan, Xiangqiao; Zhang, Zeha; Du, Shanyi

1992-05-01

216

Enhancing Ultimate Compressive Strength of Notch Embedded Steel Cylinders Using Overwrap CFRP Patch  

Science.gov (United States)

In this study, the application of Fiber Reinforced Polymer (FRP) patch for strengthening of the damaged area in thin walled steel cylinders under compression loading was investigated. In this direction, some experimental tests were carried out on the selected notch induced specimens with unique diameter-to-thickness ratio (D/t). The obtained results were compared to the intact cylinder in order to find out the reduction effect of notch on the buckling load of cylinders. Following that, the notched specimens were treated using externally FRP by wrapping around the notched area and the stability strength of the retrofitted specimens was measured experimentally. The investigation was also carried out in numerical analysis using FEM in order to develop the proposed technique for determination of optimum FRP configurations and also better understanding of the experimental observations considering the nonlinear behavior and failure modes for composite member.

Kabir, Mohammad Z.; Nazari, Alireza

2012-06-01

217

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

Science.gov (United States)

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

Nettles, Alan T.

2009-01-01

218

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

Directory of Open Access Journals (Sweden)

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

Mücteba Uysal

2011-12-01

219

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

Scientific Electronic Library Online (English)

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

Antonio, Piratelli-Filho; Frank, Shimabukuro.

2008-12-01

220

Dynamics of unconfined spherical flames  

CERN Document Server

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

221

Estimate of compressive strength of an unidirectional composite lamina using cross-ply and angle-ply laminates  

Directory of Open Access Journals (Sweden)

Full Text Available In this work has been estimated the compressive strength of a unidirectional lamina of a carbon/epoxy composite material, using the cross-ply and angle-ply laminates. Over the years various methods have been developed to deduce compressive properties of composite materials reinforced with long fibres. Each of these methods is characterized by a specific way of applying load to the specimen. The method chosen to perform the compression tests is the Wyoming Combined Loading Compression (CLC Test Method, described in ASTM D 6641 / D 6641M-09. This method presents many advantages, especially: the load application on the specimen (end load combined with shear load, the reproducibility of measurements and the experimental equipment quite simplified. Six different laminates were tested in compressive tests. They were realized by the same unidirectional prepreg, but with different stacking sequences: two cross-ply [0/90]ns, two angle-ply [0/90/±45]ns and two unidirectional laminates [0]ns and [90]ns. The estimate of the compressive strength of the unidirectional laminates at 0°, was done by an indirect analytical method, developed from the classical lamination theory, and which uses a multiplicative parameter known as Back-out Factor (BF. The BF is determined by using the experimental values obtained from compression tests.

M. Scafè

2014-07-01

222

Formulation of reduction rate for ultimate compressive strength of stiffened panel induced by opening  

Science.gov (United States)

The main objective of this study is to numerically investigate the characteristics of ultimate compressive strength of stiffened panels with opening and also to fit the design-oriented formulae. For this purpose, three series of well executed experimental data on longitudinally stiffened steel plates with and without opening subjected to the uniform axial in-pane load which is carried out to study the buckling and post-buckling up to the final failure are chosen. Also, a nonlinear finite element method capable of efficiently analyzing the large elasto-plastic deflection behavior of stiffened panels is developed and used for simulation. The feasibility of the present simulation process is confirmed by a good agreement with the experimental results. More case studies are developed employing the simulation process to analyze the influence of various design variables on the reduction rate of ultimate strength of stiffened panel induced by opening. Based on the computed results, two design formulae are fitted and the accuracy of design formulae is studied. Furthermore, the viability of the design formulae for practical engineering is proved.

Yu, Chang-li; Lee, Joo-sung

2014-08-01

223

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

Directory of Open Access Journals (Sweden)

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

Mydin M.A.O.

2014-01-01

224

A Comparative Study on Compressive and Flexural Strength of Concrete Containing Different Admixtures as Partial Replacement of Cement  

OpenAIRE

Concrete is the most widely used material in the world today. This paper is about the comparative study of the flexural strength and compressive strength of concrete when different admixtures are used as partial replacement of cement in the concrete mix. The mineral admixtures that are used here are Silica Fume, Rice Husk Ash and Iron slag as partial replacement of cement. All these materials are industrial waste products and are abundantly available nowadays. These materials ...

Apoorv Singh; Patel, Prof R. D.

2014-01-01

225

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

226

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

LENUS (Irish Health Repository)

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

Dowling, Adam H

2012-03-01

227

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

Directory of Open Access Journals (Sweden)

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

FAREED AHMED MEMON

2013-02-01

228

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 SciELO Brazil | Language: English 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 randoml [...] y corroded steel plates and stiffened plates. The effects of general corrosion are introduced into the finite element models using a novel random thickness surface model. Buckling strength, post-buckling behaviour, ultimate strength and post-ultimate behaviour of the models are investigated as results of both-sides random corrosion.

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

2010-09-01

229

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

International Nuclear Information System (INIS)

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

230

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English 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 variation of the pitting corrosion geometry are evaluated. A proposal on the effective thickness is concluded in order to estimate the ultimate strength and explore the post-buckling behaviour of pitted steel plates under uniaxial compression.

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

2012-08-01

231

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

2013-04-01

232

A Comparative Study on Compressive and Flexural Strength of Concrete Containing Different Admixtures as Partial Replacement of Cement  

Directory of Open Access Journals (Sweden)

Full Text Available Concrete is the most widely used material in the world today. This paper is about the comparative study of the flexural strength and compressive strength of concrete when different admixtures are used as partial replacement of cement in the concrete mix. The mineral admixtures that are used here are Silica Fume, Rice Husk Ash and Iron slag as partial replacement of cement. All these materials are industrial waste products and are abundantly available nowadays. These materials have high silica content and pozzolanic properties and can be effectively used as a replacement of cement during the formation of High Performance Concrete. Compressive and Flexural strength are the two most important characteristic of concrete and are calculated for the hardened concrete to analyze the load bearing capacity for design purposes. Thus for the effective judgment of type of mineral admixtures to be used a comparative study is very useful.

Apoorv Singh

2014-09-01

233

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

Science.gov (United States)

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

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

1944-01-01

234

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

Directory of Open Access Journals (Sweden)

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

2010-01-01

235

Fundamental parameters for the stiffness and strength control of artificially cemented sands  

OpenAIRE

The treatment of soils with cement is an attractive technique when the project requires improvement of the local soil for the construction of subgrades for rail tracks, as a support layer for shallow foundations and to prevent sand liquefaction. As reported by Consoli et al. in 2007, a unique dosage methodology has been established based on rational criteria where the voids/cement ratio plays a fundamental role in the assessment of the target unconfined compressive strength. The present study...

Nilo Cesar Consoli; António Viana da Fonseca; Rodrigo Caberlon Cruz; Karla Salvagni Heineck

2009-01-01

236

Uniaxial-compression-test series on Tram tuff  

International Nuclear Information System (INIS)

Twenty-five uniaxial compression experiments were performed on samples of the Tram Member of the Center Flat Tuff obtained from drill hole USW-G1 at Yucca Mountain on the Nevada Test Site. The water saturated samples were deformed at nominal strain rates ranging from 10-2 to 10-6 sec-1, atmospheric pressure and room temperature. Resultant unconfined compressive strengths, axial strains to failure, Young's moduli and Poisson's ratios ranged from 14.5 to 69.2 MPa, .0029 to .0052, 5.17 to 22.5 GPa and .09 to .38, respectively

237

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

Directory of Open Access Journals (Sweden)

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

Glen E. Fryxell

2008-03-01

238

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

Science.gov (United States)

Introduction: The aim of this experimental laboratory study was to evaluate the effect of different mixing and placement techniques on compressive strength (CS) of calcium-enriched mixture (CEM) cement. Methods and Materials: CEM powder was mixed with its liquid either by hand mixing or amalgamator mixing. The mixture was loaded to cylindrical acrylic molds with 6.0±0.1 mm height and 4.0±1 mm diameter. Half of the specimens in each group were selected randomly and ultrasonic energy was applied to them for 30 sec. All samples were incubated for 7 days at 37°C. The CS test was performed by means of a universal testing machine. The data were analyzed by the two-way analysis of variance (ANOVA) and Tukey’s post hoc tests. The level of significance was set at 0.05. Results: The maximum CS was seen in the amalgamator-mixed samples that did not receive ultrasonic agitation. The CS value of amalgamator-mixed samples was significantly higher than manually-mixed ones (P=0.003). Ultrasonic vibration did not change the CS of specimens. Conclusion: According to the results, mixing with amalgamator increases the CS of CEM cement, while ultrasonic vibration had no positive effect.

Sahebi, Safoora; Sadatshojaee, Nooshin; Jafari, Zahra

2015-01-01

239

Correlation development between indentation parameters and uniaxial compressive strength for Colombian sandstones  

International Nuclear Information System (INIS)

A new 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 and 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 sandstone. These correlations were obtained using o set of 248 indentation tests and separate compression fasts 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 is 0.81 and 0.70 respectively. The use of the correlations 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

240

The effect of shredding and test apparatus size on compressibility and strength parameters of degraded municipal solid waste.  

Science.gov (United States)

In many situations, MSW components are processed and shredded before use in laboratory experiments using conventional soil testing apparatus. However, shredding MSW material may affect the target property to be measured. The objective of this study is to contribute to the understanding of the effect of shredding of MSW on the measured compressibility and strength properties. It is hypothesized that measured properties can be correlated to an R-value, the ratio of waste particle size to apparatus size. Results from oedometer tests, conducted on 63.5 mm, 100 mm, 200 mm diameter apparatus, indicated the dependency of the compressibility parameters on R-value. The compressibility parameters are similar for the same R-value even though the apparatus size varies. The results using same apparatus size with variable R-values indicated that shredding of MSW mainly affects initial compression. Creep and biological strain rate of the tested MSW are not significantly affected by R-value. The shear strength is affected by shredding as the light-weight reinforcing materials are shredded into smaller pieces during specimen preparation. For example, the measured friction angles are 32 degrees and 27 degrees for maximum particle sizes of 50 mm and 25 mm, respectively. The larger MSW components in the specimen provide better reinforcing contribution. This conclusion is however dependent on comparing specimen at the same level of degradation since shear strength is also a function of extent of degradation. PMID:19395251

Hossain, M S; Gabr, M A; Asce, F

2009-09-01

241

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.

Omolola C. Olaiya

2012-06-01

242

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

Directory of Open Access Journals (Sweden)

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

Fareed Ahmed Memon

2012-03-01

243

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

Science.gov (United States)

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

Prahara, E.; Meilani

2014-03-01

244

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

Directory of Open Access Journals (Sweden)

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

Prahara E.

2014-03-01

245

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

Directory of Open Access Journals (Sweden)

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

Floriberto Díaz-Díaz

2013-11-01

246

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

Science.gov (United States)

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

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

2014-07-01

247

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

Science.gov (United States)

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

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

2014-07-01

248

Compressive strength of masonry made of clay bricks and cementmortar: Estimation based on Neural Networks and Fuzzy Logic  

OpenAIRE

The use of mathematical tools such as Artificial Neural Networks and Fuzzy Logic has been shown to be useful for solving complex engineering problems, without the need to reproduce the phenomenon under study, when the only information available consists of the parameters of the problem and the desired results. Based on a collection of 96 laboratory tests, this paper uses Artificial Neural Networks and Fuzzy Logic to determine the compressive strength of a masonry structure composed of clay br...

Garzo?n Roca, Julio; Obrer Marco, Creu; Adam Marti?nez, Jose? Miguel

2013-01-01

249

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

OpenAIRE

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

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

2013-01-01

250

Analysis of moisture state of recycled coarse aggregate and its influence on compression strength of the concrete  

OpenAIRE

This article analyzes the impact of the moisture level of recycled coarse aggregate additions to concrete on its compression strength, with the goal of finding a logical development process that can be reproduced at an industrial level and provide acceptable results for concrete production. This study takes into account the reality in the process of the production of concrete; while many authors suggest the use of recycled coarse aggregates in a saturated state to ensure the desired ratio wat...

Pelufo Carbonell, Mari?a Jose?; Domingo Cabo, Alberto; Ulloa Mayorga, Vivia?n Andrea; Vergara Acun?a, Needy Nayiv

2009-01-01

251

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

OpenAIRE

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

Hidayat Irpan; Siauwantara Alice

2014-01-01

252

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

International Nuclear Information System (INIS)

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

253

The effect of gamma irradiation on the strength and elasticity of climax stock and westerly granites  

International Nuclear Information System (INIS)

The authors performed compression tests on Climax Stock quartz monzonite (CSQM), half of which had received a gamma ray dose of 9 +- MGy (0.9 Grad) and half of which had not. They performed similar tests on Westerly granite. The experiment on CSQM was capable of detecting a 7% change in the unconfined strength level of 200 MPa. The experiment showed no statistically significant change. Null results were also found for the effect of gamma irradiation Young's modulus and Poisson's ratio in CSQM and for that on the compressional strength of Westerly granite. They thus conclude that gamma irradiation has no effect on the strengths of either CSMQ or Westerly grainite

254

Use of nonlinear prediction tool to estimate uniaxial compressive strength and modulus of elasticity of some granitic rocks  

Science.gov (United States)

In several rock engineering applications, various prediction tools have been used to estimate strength and deformation parameters of intact rock. Commony, simple and linear multivariable regression methods have been employed. However, recently, some soft computing methods such as fuzzy inference systems, artificial neural Networks and neuro-fuzzy models have been used and they have yielded successful results, because the problems at hand have generally nonlinear nature. The purpose of the present study is to apply neuro-fuzzy modeling to estimate uniaxial compressive strength and modulus of elasticity of some granitic rocks from their physical and index properties. For the purpose of the study, sampling works on seven different granitic rocks from different locations in Turkey were performed. On these samples, unit weight, porosity, void ratio, water absorption by weight, P-wave velocity, point load index, block punch index, tensile strength, uniaxial compressive strength and modulus of elasticity were determined in laboratory. A total of 88 specimens were used during the laboratory tests. In the first stage of the analyses, stepwise multiple regression analyses were performed. By using the input parameters of the most successful regression models, some models based on adaptive neuro-fuzzy inference system (ANFIS) were developed to predict uniaxial compressive strength and modulus of elasticity. The general performances of the ANFIS models are considerably high. This results show that prediction of some intact rock properties is a nonlinear problem. For this reason, when predicting the intact rock properties, the nonlinear methods such as fuzzy inference system, artificial neural networks, adaptive neuro-fuzzy inference system or nonlinear multiple regression methods should be considered.

Gultekin, Nurgul; Sezer, Ebru; Gokceoglu, Candan

2010-05-01

255

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

2000-04-01

256

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

2014-11-01

257

Evidence for a Long-Term Strength Threshold in Crystalline Rock  

Science.gov (United States)

The mechanical response of brittle rock to long-duration compression loading is of particular concern in underground disposal of nuclear waste, where radionuclides must be isolated from the biosphere for periods of the order of a million years. Does the strength decrease without limit over such time, or is there, for some rock types, a lower “threshold” strength below which the rock will cease to deform? This paper examines the possibility of such a threshold in silicate crystalline rocks from several perspectives, including: (1) interpretation of the results of short-term creep tests on rock; (2) numerical analysis of the effect of decrease in fracture toughness due to stress corrosion on the strength of a crystalline rock; and (3) evidence from plate tectonics, and observations of in situ rock stress in granite quarries. The study concludes that there is clear e vidence of threshold strength. The threshold is of the order of 40% of the unconfined compressive strength or higher for laboratory specimens under unconfined compressive loading, and increases rapidly in absolute value with confinement. Field evidence also leads to the conclusion that the long-term strength of crystalline rock in situ is of comparable magnitude to the laboratory value.

Damjanac, Branko; Fairhurst, Charles

2010-09-01

258

X-ray diffraction from stishovite under nonhydrostatic compression to 70 GPa: Strength and elasticity across the tetragonal ? orthorhombic transition  

Science.gov (United States)

The tetragonal phase of silica (stishovite) was synthesized at high pressure and temperature in a laser-heated diamond anvil cell. Nonhydrostatic pressure condition was produced by pressurizing the sample without any pressure transmitting medium. The tetragonal ? orthorhombic transition could be detected from the X-ray diffraction patterns at ˜40 GPa. In contrast, the orthorhombic phase has been reported to occur only above ˜60 GPa in an earlier experiments under hydrostatic pressure. However, the transition pressures derived from the square of the symmetry-breaking strain versus pressure data in the two cases differ only marginally, the values being 44(8) GPa and 49(2) GPa under nonhydrostatic and hydrostatic compressions, respectively. We combine the d-spacings measured under nonhydrostatic and hydrostatic compressions to derive a parameter Q(hkl) that contains the information on differential stress t (a measure of compressive strength) and single-crystal elasticity. The compressive strengths derived from the average value of Q(hkl) and line-width analysis agree well. It increases from ˜4 GPa at 20 GPa to ˜8 GPa at 40 GPa and decreases as the transition pressure is approached. In the orthorhombic phase, t increases with pressure monotonically. The mean crystallite size of the sample decreases from ˜5000 Å to ˜1000 Å as the pressure is increased from 20 GPa to 45 GPa and remains nearly unchanged between 45 GPa and 70 GPa. The single-crystal elastic moduli derived from the X-ray diffraction data indicate that (C11-C12) decreases rapidly as the transition pressure is approached. Line-width analysis of the diffraction lines suggests that near-hydrostatic pressure condition is achieved by laser annealing of the compressed sample.

Singh, Anil K.; Andrault, Denis; Bouvier, Pierre

2012-10-01

259

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

260

ENVIRONMENTAL IMPACT RESULTING FROM UNCONFINED ANIMAL PRODUCTION  

Science.gov (United States)

This report outlines and evaluates current knowledge related to environmental effects of unconfined animal production. Animal species directly addressed include cattle, sheep, and hogs. All available date indicate that pollutant yields from pasture and rangeland operations are no...

261

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

Directory of Open Access Journals (Sweden)

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

S. S, Pathak

2012-10-01

262

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

LENUS (Irish Health Repository)

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

Dowling, Adam H

2011-06-01

263

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

OpenAIRE

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

Yu Jingyuan; Li Qiang; Tang Ji

2011-01-01

264

Further investigation on the dynamic compressive strength enhancement of concrete-like materials based on split Hopkinson pressure bar tests Part II Numerical Simulations  

OpenAIRE

Abstract Split Hopkinson pressure bars (SHPB) have been used widely to measure the dynamic compressive strength of concrete-like materials at high strain-rate between 101 and 103 s?1. It has been shown in companion paper (Zhang et al. 2009) that the axial strain acceleration is normally unavoidable in an SHPB test on brittle materials. Axial strain acceleration introduces radial confinement in the SHPB specimens and consequently enhances the compressive strength of concrete-like ...

Li, Q. M.; Lu, Y. B.; Meng, H.

2009-01-01

265

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

OpenAIRE

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 obtaine...

Drago? Voiculescu

2010-01-01

266

Improving the Bearing Strength of Sandy Loam Soil Compressed Earth Block Bricks Using Sugercane Bagasse Ash  

OpenAIRE

The need for affordable and sustainable alternative construction materials to cement in developing countries cannot be underemphasized. Compressed Earth Bricks have gained acceptability as an affordable and sustainable construction material. There is however a need to boost its bearing capacity. Previous research show that Sugarcane Bagasse Ash as a soil stabilizer has yielded positive results. However, there is limited research on its effect on the mechanical property of Compressed Earth Bri...

Salim, Ramadhan W.; Ndambuki, Julius M.; Adedokun, David A.

2014-01-01

267

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

International Nuclear Information System (INIS)

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

268

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

2012-04-01

269

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. R. Masaddeghi

2008-07-01

270

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

OpenAIRE

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

Prahara E.; Meilani

2014-01-01

271

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

OpenAIRE

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

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

2013-01-01

272

Effect of impact damage and open holes on the compression strength of tough resin/high strain fiber laminates. [graphite-epoxy composites  

Science.gov (United States)

Structural damage and design-based inclusions such as cutouts can reduce significantly the strength of graphite-epoxy laminates. One composite mechanics research activity at the Langley Research Center is to assess and improve the performance of composite structures in strength are common to both tension and compression loaded laminates; however, the problem associated with compression performance is the most illusive to solve. Compression failure involves both shear crippling and delamination modes. Several graphite-epoxy material systems proposed for improved damage-tolerance were studied. Material parameters included both tough resin formulations and high strain fibers.

Williams, J. G.

1984-01-01

273

Compression and strength of dense sand at high pressures and elevated temperatures  

Energy Technology Data Exchange (ETDEWEB)

The paper examines the stress-strain behaviour of densely compacted sand tested at pressures up to 80 MPa in one-dimensional compression and 7.2 MPa confining pressure in triaxial tests. Tests were performed at temperatures up to 100{sup o}C. The testing relates to a proposal by Atomic Energy of Canada Limited to fill containers of waste nuclear fuel with a crushed quartz sand to provide additional stiffness. No significant effects of temperature were encountered in either isotropic compression or triaxial shear. (author)

Graham, J.; Alfaro, M. [Univ. of Manitoba, Dept. of Civil Engineering, Winnipeg, Manitoba (Canada)]. E-mail: jgraham@cc.umanitoba.ca; Ferris, G. [BGC Engineering Inc., Calgary, Alberta (Canada)

2004-12-15

274

Compression and strength of dense sand at high pressures and elevated temperatures  

International Nuclear Information System (INIS)

The paper examines the stress-strain behaviour of densely compacted sand tested at pressures up to 80 MPa in one-dimensional compression and 7.2 MPa confining pressure in triaxial tests. Tests were performed at temperatures up to 100oC. The testing relates to a proposal by Atomic Energy of Canada Limited to fill containers of waste nuclear fuel with a crushed quartz sand to provide additional stiffness. No significant effects of temperature were encountered in either isotropic compression or triaxial shear. (author)

275

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

Directory of Open Access Journals (Sweden)

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

Pedram Masoud

2014-03-01

276

Processing of bulk metallic glasses with high strength and large compressive plasticity in Cu50Zr50  

International Nuclear Information System (INIS)

Fully metallic glassy rods of 1.5 mm diameter were successfully prepared in binary Cu50Zr50 alloy by copper mould injection casting method. The samples were characterized by X-ray diffraction, differential scanning calorimetry and high-resolution transmission electron microscopy (HRTEM). Room temperature uniaxial compression tests for the Young's modulus, fracture strength and total strain yield values of about 88 GPa, 2550 MPa and 11.7%, respectively. Significant work hardening is also observed from the stress-strain curves. The 1-2 nm scale medium-range ordering revealed by HRTEM investigations is thought to be responsible for the high strength, significant work hardening and large plasticity of the samples

277

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 ,

2013-08-01

278

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.alline or ultrafine microstructures. The experimental results are discussed using existing models for adiabatic shear localization in metals

279

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

Directory of Open Access Journals (Sweden)

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

Pudjisuryadi, P.

2013-01-01

280

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

281

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

OpenAIRE

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

Dandekar, D.

1994-01-01

282

Pharmaceutical binders and their function in directly compressed tablets : Mechanistic studies on the effect of dry binders on mechanical strength, pore structure and disintegration of tablets  

OpenAIRE

In this thesis, the strength-enhancing mechanisms of dry binders in direct compression were studied. The systems investigated were binary mixtures containing various compounds and binders. Among the binders used were a series of different molecular weights of polyethylene glycol. The proposed simplified tablet model describing the fracture path in a tablet during strength testing offers an explanation for the increase in tablet strength caused by the binder. The model and results in this thes...

Mattsson, Sofia

2000-01-01

283

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

International Nuclear Information System (INIS)

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

284

Influence Factor Analysis on Strength of Lime-Fly Ash Loess  

OpenAIRE

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 ...

Yufen Zhang; Zhiquan Zhang

2013-01-01

285

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

OpenAIRE

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

Ashton, M.; Parry, D.

1997-01-01

286

The effects of friction on the compressive behaviour of high strength steels  

International Nuclear Information System (INIS)

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

287

Study of the compressive strength of concrete block prisms : stack and running bond  

OpenAIRE

The main goal of this work is to investigate the nonlinear behavior of concrete block masonry prisms under compression, with an emphasis in the prism deformability and the failure modes. A total of 18 stack-bonded prisms have been tested, using hollow blocks of a single geometry and two different mortar types. To investigate the effect of vertical joints, the bond pattern – stack and running bond – in the prism was varied, by using half units. Finite element analysis of hollow masonry pri...

Mohamad, Gihad; Lourenc?o, Paulo B.; Roman, Humberto R.

2011-01-01

288

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

International Nuclear Information System (INIS)

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

289

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

2013-07-01

290

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English 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 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.

2012-04-01

291

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

Science.gov (United States)

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

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

2012-01-01

292

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

OpenAIRE

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...

Ferna?ndez-jime?nez, Ana; Palomo, A.

2007-01-01

293

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

Science.gov (United States)

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

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

2012-09-01

294

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

International Nuclear Information System (INIS)

A method is described for increasing the phase stability and the compressive yield strength of a corrosion resistant uranium-1 to 3 wt.% zirconium alloy comprising the steps of reducing the thickness of a homogeneous ingot of the alloy by upset forging, rolling the forged ingot into a plate, heating the plate in vacuum to a temperature about the gamma transformation temperature and water quenching the plate to ambient temperature with the alloy exhibiting alpha prime and equilibrium alpha plus delta phases. The improvement described here consists of the steps of cold rolling the plate after the quenching to further reduce the thickness of the plate, aging the cold rolled plate at a first temperature, thereafter aging the cold rolled plate at a second temperature higher than the first temperature for converting alpha prime phase into additional equilibrium alpha and delta phases, and cooling the plate to ambient temperatures

295

Effects of crushing degree of coal mixture components on coke compression strength  

Energy Technology Data Exchange (ETDEWEB)

Analyzes effects of selective crushing of a coking mixture consisting of black coal types Zh, OS, G, K and GZh on mechanical coke properties. Coal of the Zh, K and OS classes was crushed to below 3 mm. Size of the G and GZh coal ranged from 0 to 20 mm. Effects of mean grain size of the G and GZh coal classes on the M25 coke compression index and the M10 coke wear index are comparatively evaluated using regression analysis. Curves describing dependence of coke mechanical properties on grain size of 2 mixture components are plotted. Optimum grain size of the G and GZh components was determined: GZh grain size below 3 mm, G grain size 3-20 mm. 6 refs.

Balabanov, V.A.; Gulyamov, Yu.M.; Panchenko, N.I.; Mikhno, S.I.; Romanenko, V.N.; Boiko, V.N.

1988-08-01

296

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

Science.gov (United States)

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

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

2015-02-01

297

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

OpenAIRE

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

Li Qiang; Zhang Fengfeng; Yu Jingyuan

2013-01-01

298

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

OpenAIRE

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

Sakthieswaran Natarajan; Ganesan Karuppiah

2014-01-01

299

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

Science.gov (United States)

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

Yu, Yuying; Tan, Ye; Dai, Chengda; Li, Xuemei; Li, Yinghua; Wu, Qiang; Tan, Hua

2014-11-01

300

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

Science.gov (United States)

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

Natarajan, Sakthieswaran; Karuppiah, Ganesan

2014-01-01

301

Distribution of oscillator strengths in centrosymmetrical models of a ''compressed'' hydrogen atom  

International Nuclear Information System (INIS)

The possibility of describing the effect of nonideality on the optical spectra of plasma near photoionization thresholds with the help of centrosymmetrical models of an atom with a short-range potential is studied. It is shown that the average density of the oscillator strengths of the hydrogen atom df/dE = f/sub n/(dE/dn)-1 in such models does not depend on the method used to deform the tail of the Coulomb electron--ion potential (transforming it into a short-range potential) and coincides with the analogous quantity for the undeformed Coulomb potential. It corresponds to the quasicontinuum of the broadened and coalesced spectral lines. Transmission-window effects do not appear in centrosymmetrical potential models. The results are compared with those of preceding works. It is proposed that the presence of plasma microfields and interaction of highly excited electrons with nearby charged particles must be taken into account in order to give an adequate description of prethreshold spectra in a nonideal plasma

302

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-07-01

303

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

Science.gov (United States)

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

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

2015-01-01

304

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

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.

 

Asokan Pappu

2010-03-01

305

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

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

2013-02-01

306

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

2012-01-01

307

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

International Nuclear Information System (INIS)

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

308

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

Science.gov (United States)

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

Kim, Moon-Hwan; Oh, Jae-Seop

2015-01-01

309

Uniaxial and triaxial compression test series on Topopah Spring tuff  

International Nuclear Information System (INIS)

Fifteen uniaxial and triaxial compression experiments were performed on samples of the Topopah Spring Member of the Paintbrush Tuff obtained from drill hole USW-G1 at Yucca Mountain on the Nevada Test Site. The water saturated test specimens were deformed at nominal strain rates of 10-2, 10-4, 10-5 and 10-6 s-1; confining pressures of 0.1, 5 and 10 MPa; and room temperature. Resultant unconfined compressive strengths, axial strains to failure, Young's moduli and Poisson's ratios ranged from 44.9 to 176.6 MPa, .0034 to .0057, 22.9 to 40.8 GPa and .15 to .33, respectively

310

Uniaxial and triaxial compression test series on Calico Hills tuff  

International Nuclear Information System (INIS)

Forty-four uniaxial and triaxial compression experiments were performed on samples of the Tuffaceous beds of Calico Hills obtained from drill hole USW-G1 at Yucca Mountain on the Nevada Test Site. Water saturated and room dry test specimens were deformed at nominal strain rates of 10-3, 10-5 and 10-7 s-1; confining pressures of 0.1, 10 and 20 MPa; and room temperature. Resultant unconfined compressive strengths, axial strains to failure, Young's moduli and Poisson's ratios ranged from 14.2 to 42.0 MPa, 0.0037 to 0.0087, 2.52 to 9.72 GPA and 0.17 to 0.37, respectively

311

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

Scientific Electronic Library Online (English)

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

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

2005-12-01

312

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

Directory of Open Access Journals (Sweden)

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

Letícia Brandão

2005-12-01

313

Slump loss and compressive strength of concrete made with WRR and HRWR admixtures and subjected to prolonged mixing. [Water Reducing Retarders, High-Range Water Reducing  

Energy Technology Data Exchange (ETDEWEB)

The effect of four water-reducing and retarding admixtures, and three superplasticizers on the consistency (slump) of fresh concrete, was studied at 21 C and 32 C in concrete mixes, made of OPC containing 10% fly ash, and subjected to prolonged mixing for up to 180 min. The effect of such mixing on compressive strength of concrete, at the ages of 3, 7, 28 and 90 days, was also studied. It was found that the admixtures in question accelerated the rate of slump loss and at all ages, concrete compressive strength linearly increased with mixing time. The rate of slump loss, and the water demand of the concrete mixes increased within the temperature range studied.

Ravina, D.; Soroka, I. (Technion-Israel Inst. of Tech., Haifa (Israel))

1994-01-01

314

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

2011-08-01

315

Fly and bottom ashes from biomass combustion as cement replacing components in mortars production: rheological behaviour of the pastes and materials compression strength.  

Science.gov (United States)

In the present research mortar pastes obtained by replacing a commercial cement with the equivalent mass of 5, 10, 20 and 30 wt.% of fly ash or bottom ash from fir chips combustion, were prepared and rheologically characterized. It was observed that the presence of ash modifies their rheological behaviour with respect to the reference blend due to the presence, in the ashes, of KCl and K2SO4 which cause precipitation of gypsum and portlandite during the first hydration stages of the pastes. Hydrated materials containing 5 wt.% of ash display compression strength and absorption at 28 d of same magnitude as the reference composition; conversely, progressive increase of ash cause a continuous decline of materials performances. Conversely, samples tested after 180 d display a marked decline of compression strength, as a consequence of potassium elution and consequent alkali-silica reaction against materials under curing. PMID:21762950

Maschio, Stefano; Tonello, Gabriele; Piani, Luciano; Furlani, Erika

2011-10-01

316

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

OpenAIRE

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 o...

Vaitkus, Saulius; Gnip, Ivan; Ve?jelis, Sigitas

2013-01-01

317

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

Directory of Open Access Journals (Sweden)

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

Othuman Mydin M.A.

2014-01-01

318

Unconfined Aquifer Flow Theory - from Dupuit to present  

CERN Document Server

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

319

Strength and Micro-strain Distribution of Shock Compressed Aluminum Single Crystals Determined from Real-time X-ray Diffraction  

Science.gov (United States)

Shock compressed Al(100) single crystals were examined using x-ray diffraction (XRD) and velocity interferometry. Mo K? x-rays were used to obtain high resolution XRD measurements of the Al 200, 400, and 600 peaks. The XRD measurements were obtained at the rear surface of the Al after a partial stress release due to reflection of the plastic wave at an Al/vitreous carbon interface. Analytic methods were developed to determine macroscopic strength and local micro-strain distributions from XRD measurements and were applied to the Al(100) XRD data. The Al crystals are shown to strain harden; for the highest stress experiment (12.7 GPa Al input stress and 7.1 GPa reflected stress), the strength is 0.52 GPa compared to a strength of 0.025 GPa at the HEL. The distribution of local micro-strains is used to estimate the distribution of local maximum stress differences. The FWHM of the distribution of local maximum stress differences is about 50% of the macroscopic stress difference (or strength) for shock compressed Al(100). Work supported by DOE/NNSA.

Turneaure, Stefan; Gupta, Y. M.

2011-06-01

320

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

Science.gov (United States)

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

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

2014-12-15

321

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

Scientific Electronic Library Online (English)

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

Mohammad Reza, Khedmati; Pedram, Edalat.

2010-09-01

322

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 which contained an encapsulated component. Predictions of center, midradial, and component temperatures, as well as regression of the foam surface, were in agreement with measurements using thermocouples and X-ray imaging.

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

1999-11-01

323

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

324

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

Scientific Electronic Library Online (English)

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

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

2014-10-01

325

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

Science.gov (United States)

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

Chi, Se-Hwan

2013-05-01

326

Interfacial strength of compression-molded specimens between PMMA powder and PMMA/MMA monomer solution-treated ultra-high molecular weight polyethylene (UHMWPE) powder.  

Science.gov (United States)

The interface between bone cement and ultra-high molecular weight polyethylene (UHMWPE) has been considered a weak link of cemented UHMWPE acetabular cup in total hip replacement (THR). For the improvement of this weak interface, adhesion between the UHMWPE acetabular cup and bone cement made of polymethylmethacrylate (PMMA) has been investigated in our laboratory. Virgin UHMWPE powders were treated with methyl methacrylate (MMA) monomer and PMMA/MMA solution. The treated UHMWPE powders were then compression-molded with virgin UHMWPE powders or PMMA powders, creating two different interfaces, i. e., treated/virgin UHMWPE powder and treated UHMWPE/PMMA powder. For the present study, the interfacial strengths between PMMA powder and the treated UHMWPE power were investigated following the same protocol previously set. The maximum interfacial strength was 17.0 +/- 0.25MPa with the same molding condition of 166.5 degrees C, 38.7 MPa and l h. In addition to the molding condition, we tested the strengths for the treated UHMWPE powders, which have different ratios between PMMA/MMA solution and MMA-treated UHMWPE powders. Significant differences on the interfacial strengths resulted due to the ratio change; more PMMA in the PMMA/MMA solution-treated UHMWPE powder exhibited higher interfacial strength. Scanning electron microscopic (SEM) pictures showed that the interface is composed of three major portions: PMMA powder, UHMWPE, and coated PMMA, indicating strong mechanical interlocking of UHMWPE and PMMA powder matrix and chemical bonding between PMMA powder and the precoated PMMA onto the UHMWPE. In addition, another interfacial strength between PMMA powder, which is equivalent to the outermost part of the cup, and bone cement was investigated. The average strength reached up to 42.4 +/- 3.6 MPa, close to the tensile strength of bone cement itself. PMID:11074434

Park, K D; Park, J B

2000-01-01

327

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  

OpenAIRE

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-f...

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

2012-01-01

328

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 SciELO Brazil | Language: English 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 b [...] y using microwave drying. OBJECTIVE: This study evaluated the influence of drying techniques at room temperature and microwave oven on the linear dimensional change, compressive strength and detail reproduction in type IV dental stones. MATERIAL AND METHODS: Three type IV dental stone brands were selected; elite Rock, Shera Premium and Durone IV. Two different drying protocols were tested in 4 groups (n=10); G1 - room temperature (25±4ºC) dried for 2 hours; G2 - room temperature dried for 24 hours; G3 - room temperature dried for 7 days and G4 - microwave oven dried at 800 W for 5 minutes and after 2 hours at room temperature. After drying, the samples were assayed for dimensional charges. The sample surface was submitted to the ImageTool 3.0 software for compressive strength in a universal testing machine with a cell load of 50 KN at a crosshead speed of 0.5 mm/minutes and the detail reproduction was analyzed with a stereomicroscope at 25x magnification. The statistical analysis of the linear dimensional change and compressive strength data were conducted by the ANOVA test followed by the Tukey test (p

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

2012-10-01

329

Elastic moduli and strength of nanocrystalline cubic BC2N from x-ray diffraction under nonhydrostatic compression  

Science.gov (United States)

The stress behavior of nanocrystalline cubic boron carbon nitride (c-BC2N) was investigated using radial and axial x-ray diffractions in the diamond-anvil cell under nonhydrostatic compression up to ~100 GPa. The radial x-ray diffraction (RXRD) data yield a bulk modulus K0=276±20GPa with a fixed pressure derivative K0'=3.4 at ?=54.7° , which corresponds to the hydrostatic compression curve. The bulk modulus obtained from axial x-ray diffraction (AXRD) gives a value of 420±11GPa . A comparative study of the observed compression curves from radial and axial diffractions shows that the ruby-fluorescence pressure scale may reflect the maximum stress under nonhydrostatic compression. It was found that nanocrystalline c-BC2N sample could support a maximum differential stress of ~38 GPa when it started to yield at ~66 GPa under uniaxial compression. Moreover, the aggregate elastic moduli of the nanocrystalline c-BC2N have been determined from the RXRD data at high pressures.

Dong, Haini; He, Duanwei; Duffy, Thomas S.; Zhao, Yusheng

2009-01-01

330

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

International Nuclear Information System (INIS)

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

331

Radial flow towards well in leaky unconfined aquifer  

Science.gov (United States)

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

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

2012-12-01

332

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

333

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

334

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 SciELO Brazil | Languages: English, Portuguese 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, deformações e modos de ruptura. Posteriormente, esses resultados foram comparados com diferentes modelos teóricos de previsão de resistência, baseados nas resistências individuais de cada material, nas suas deformações de ruptura e no efeito de cintamento introduzido pelos blocos no sistema. Entre os modelos estudados, verificou-se que os que conduziram à melhores resultados foram aqueles em que foi considerado o efeito do cintamento proporcionado pelo bloco de concreto e, ainda, uma alteração na deformação de ruptura do graute. Abstract in english This paper compares different models for predicting the compressive strength of concrete block masonry prisms. Four different prism configurations were studied experimentally, each of which was tested without grout (ungrouted prisms) and with grout and reinforcement (reinforced prisms). The axial co [...] mpressive strength, strain and failure modes of all the prism configurations were recorded. These results were then compared with different theoretical models for predicting compressive strength, based on the individual strength of each material, its break strain and the strapping effect of the blocks on the system. Among the models studied here, the best results were obtained with those that consider the strapping effect of the concrete block, as well as a change in the break strain of grout.

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

2011-12-01

335

Nematode Locomotion in Unconfined and Confined Fluids  

CERN Document Server

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

336

Axial compression behavior of concrete filled steel tubular stub columns using high strength materials; Kokyodo zairyo wo mochiita concrete juten kokan tanchu no jikuasshuku tokusei  

Energy Technology Data Exchange (ETDEWEB)

Experimental discussions have been given to identify basic properties of concrete filled steel tubular (CFT) columns. The discussions have conducted center compression experiments on short CFT columns using combination of material strengths of wide range (concrete: 20 MPa to 90 MPa and steel tubes: 400 MPa to 780 MPa) and width to thickness ratio (circular cross section: 17 to 152 and rectangular cross section: 19 to 74). The experiments have investigated rise in withstand strength after yield as a result of difference in fracture profiles, and effects on deformation capacity. Force application was conducted having the confining condition above and below a test body fixed. Loading, which is monotonous loading, has been executed until axial strain reached 5%. As a result, the fracture profiles of the CFT columns were found classifiable into three types, which exhibited close relationship between the maximum withstand strength and the deformation capacity. Major factor affecting structural performances such as fracture profile, deformation capacity and maximum withstand strength is the confining force of the steel tubes on concrete. It was found that these structural performances may be estimated by using the confining force of the steel tubes. 11 refs., 7 figs., 5 tabs.

Fujimoto, T.; Kumai, A.; Nishiyama, I.; Imai, E.; Kai, M.; Tanaka, Y.; Tokinoya, H.; Noguchi, T.; Baba, T.; Fukumoto, N.; Murata, Y.; Sakino, K.; Morino, S.

1997-08-30

337

Effects of augmented trunk stabilization with external compression support on shoulder and scapular muscle activity and maximum strength during isometric shoulder abduction.  

Science.gov (United States)

The aim of the present study was to investigate the effects of augmented trunk stabilization with external compression support (ECS) on the electromyography (EMG) activity of shoulder and scapular muscles and shoulder abductor strength during isometric shoulder abduction. Twenty-six women volunteered for the study. Surface EMG was used to monitor the activity of the upper trapezius (UT), lower trapezius (LT), serratus anterior (SA), and middle deltoid (MD), and shoulder abductor strength was measured using a dynamometer during three experimental conditions: (1) no external support (condition-1), (2) pelvic support (condition-2), and (3) pelvic and thoracic supports (condition-3) in an active therapeutic movement device. EMG activities were significantly lower for UT and higher for MD during condition 3 than during condition 1 (p<0.05). The MD/UT ratio was significantly higher during condition 3 than during conditions 1 and 2, and higher during condition 2 than during condition 1 (p<0.05). Shoulder abductor strength was significantly higher during condition 3 than during condition 1 (p<0.05). These findings suggest that augmented trunk stabilization with the ECS may be advantageous with regard to reducing the compensatory muscle effort of the UT during isometric shoulder abduction and increasing shoulder abductor strength. PMID:25586003

Jang, Hyun-Jeong; Kim, Suhn-Yeop; Oh, Duck-Won

2015-04-01

338

Loading simulation of lumbar spine vertebrae during a compression test using the finite elements method and trabecular bone strength properties, determined by means of nanoindentations.  

Science.gov (United States)

The mechanical strength properties of lumbar spine vertebrae are of great importance in a wide range of applications. Herein, through nanoindentations and appropriate evaluation of the corresponding results, trabecular bone struts stress-strain characteristics can be determined. In the frame of the present paper, an L2 fresh cadaveric vertebra, from which posterior elements were removed, was subjected to compression. With the aid of developed finite elements method based algorithms, the cortical shell and the cancellous core bulk elasticity moduli and stresses were determined, whereas the tested vertebra geometrical model used in these algorithms was considered as having a compound structure, consisting of the cancellous bone surrounded by the cortical shell. Moreover nanoindentations were conducted and an appropriate evaluation method of the obtained results was applied to extract stress-strain curves of individual lumbar spine vertebra trabecular bone struts. These data were used in the mathematical description of the vertebrae compression test. The vertebral cancellous bone structure was simulated by a beam elements network, possessing an equivalent porosity and different stiffnesses in vertical and horizontal direction. Thus, the measured course of the compression load versus the occurring specimen deformation was verified. PMID:15615116

Bouzakis, K D; Mitsi, S; Michailidis, N; Mirisidis, I; Mesomeris, G; Maliaris, G; Korlos, A; Kapetanos, G; Antonarakos, P; Anagnostidis, K

2004-06-01

339

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

340

Effect of Cement Stabilized Kaolin Subgrade on Strength Properties  

Directory of Open Access Journals (Sweden)

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

Nur Akmal Abd Karim

2014-01-01

341

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

2011-11-01

342

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

Science.gov (United States)

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

2009-05-01

343

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

International Nuclear Information System (INIS)

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 obseion 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.

344

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

OpenAIRE

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

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

2012-01-01

345

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.)

346

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

2011-04-01

347

Dynamic Strength Analysis of Tantalum using a Multimode Rippled Target under Laser Driven Quasi-Isentropic Compression  

Science.gov (United States)

We present results from a material strength analysis of tantalum using a multimode rippled target under quasi-isentropic plasma loading at pressure greater than 100GPa and strain rate above 106 s-1. The results are compared with test data measured at Omega Laser. A conventional approach [1,2] utilizes the RTI (Rayleigh-Taylor Instability) mechanism to infer material strength from the growth of a single sinusoidal mode pre-imposed on a target. This method was proven reliable [2,3], but there is room for improvement in efficiency. By deploying an initial perturbation with two or more sinusoidal modes superimposed onto a single target, we are able to collect more test data in a single experiment. Presented in this paper are the verification of a multimode approach against single mode; mode coupling development during the loading sequence; the behavior of induced modes; and the detection of those modes in both simulation and test measurements.[4pt] [1] B.A. Remington et at., Material Science and Technology, Vol. 22, No. 4, 2006[0pt] [2] H.S. Park et al., PRL. 104, 135504 (2010)[0pt] [3] N. R. Barton et al., J. of Applied Physics, 109, 073501, 2011

Qian, Ping; Cavallo, Robert; Park, Hye-Sook; Plechaty, Chris; Prisbrey, Shon; Wilson, Mike; Maddox, Brian; Blobaum, Kerri; May, Robert

2012-10-01

348

Strength development in underground high-sulphate paste backfill operation  

Energy Technology Data Exchange (ETDEWEB)

The effectiveness of different binding agents in a paste backfilling operation suitable for a sulphide-rich environment was evaluated in a laboratory study which involved the use of binding agents of different combinations of Portland cement, type C fly ash and ferrous slag. The unconfined compressive strength of the samples was measured for an extended curing period of 365 days. A second phase involved the use of ferrous slag as the principal binder. It was shown that Portland Cement alone is not a suitable binder to provide long-term sufficient strength for paste backfilling operations involving high-sulphide minerals. This is because for higher binding contents, the addition of Portland cement lead to higher availability of calcium hydroxide and calcium aluminate which are susceptible to deterioration from sulphate attack. It was shown that the strength of the binding agent increased up to 0.5 MPa with the addition of 3 per cent slag. Slag reduced the permeability and availability of calcium hydroxide and diluted the calcium aluminate ions, thereby reducing the potential for sulphate attack. It was noted that careful attention must still be given to ensure that the gypsum which eventually forms, does not have the same negative effects on the strength of the treated matrix. It was also shown that a more resilient mixture to sulphate attack can be created by mixing Portland cement with different percentages of type C fly ash. 13 refs., 2 tabs., 8 figs.

Hassani, F.P.; Ouellet, J. [McGill Univ., Montreal, PQ (Canada); Hossein, M. [Dames and Moore Group, New York, NY (United States)

2001-05-01

349

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

Scientific Electronic Library Online (English)

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

José Saporiti, Machado.

2006-06-01

350

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

Science.gov (United States)

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

Zhang, Y.; Jiao, J.

2013-12-01

351

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

Scientific Electronic Library Online (English)

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

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

2012-06-01

352

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 SciELO Colombia | Language: Spanish 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 comp [...] resión 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. 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 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.

Juan Manuel, Lizarazo Marriaga; José Gabriel, Gómez Cortés.

2007-04-01

353

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

Scientific Electronic Library Online (English)

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

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

1268-12-01

354

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

355

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)

356

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 g strength increased in connection with the strain accumulation and amount of tetragonal structure

357

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

2013-06-01

358

TNT Equivalency of Unconfined Aerosols of Propylene Oxide  

Directory of Open Access Journals (Sweden)

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

A. Apparao

2014-09-01

359

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

360

A stable and efficient numerical algorithm for unconfined aquifer analysis.  

Science.gov (United States)

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. PMID:19341374

Keating, Elizabeth; Zyvoloski, George

2009-01-01

361

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

362

A revisit of drawdown behavior during pumping in unconfined aquifers  

Science.gov (United States)

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

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

2011-05-01

363

Optical Studies of Unconfined Energy States and Characterizations of GALLIUM-ARSENIDE/ALUMINUM(X)GALLIUM(1 - Superlattices.  

Science.gov (United States)

Optical transitions involving unconfined states in GaAs/Al_{rm x}Ga _{rm 1-x}As superlattices have been studied as a function of the barrier width experimentally as well as theoretically. The strength of the transition involving the first unconfined heavy-hole to the first unconfined conduction states is found to depend strongly on the barrier width. For superlattices with 150 A wells and barriers with aluminum concentrations of 0.2, the transition is very strong for 150 A barriers, but insignificant for barrier widths of 70 and 30 A. The peaks arising from the transitions between the first unconfined subbands are found to be doublets. The separations of the doublet peaks have also been studied as a function of barrier width. It corresponds to the energy difference between the transitions at the Brillouin zone center and at the Brillouin zone boundary along the superlattice growth direction. The sensitivity of the energy splitting to the width of the barrier provides a useful analytical tool in determining this quantity, in much the same way that the confined transition energies relate to the well width. These unconfined transition doublet peaks have been confirmed by resonance Raman spectroscopy. Secondly, excitonic effects associated with saddle points for n = 1 confined transitions in GaAs/Al _{rm x}Ga_ {rm 1-x}As superlattices have been systematically studied as a function of the barrier width. Saddle -point associated excitonic effects have been identified and they are shown to be very sensitive to the barrier width. For example, significantly different spectra were observed with the change of the barrier width from 60 to 35 A when L_{rm z} and x were fixed at 75 A and 0.18, respectively. Thirdly, photoluminescence (PL) spectroscopy with tunable light source has been demonstrated to determine the sample quality along the sample growth direction. An emphasis was placed on the analysis of the changes of the PL spectra when varying the excitation wavelength in GaAs/Al _{rm x}Ga _{rm 1-x}As superlattices. Although interpretations of the PL results were derived with several assumptions, they could not have been easily deduced in cases of traditional PL spectroscopy employing the only one wavelength of the excitation beam. Photoluminescence excitation spectroscopy, Raman spectroscopy, x-ray double crystal diffractometry and cross-sectional transmission electron microscopy have also been demonstrated to determine the superlattice sample parameters. The values obtained by each technique are in excellent agreements with each other. Advantages and drawbacks of each technique have been discussed. (Copies available exclusively from Micrographics Department, Doheny Library, USC, Los Angeles, CA 90089 -0182.).

Yoon, Yung Sup

364

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

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

2011-09-01

365

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

2012-09-01

366

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

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

2012-09-01

367

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

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

2011-03-01

368

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

Scientific Electronic Library Online (English)

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

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

2012-01-01

369

Evaluation of oxidation characteristics of fine-grained graphites (IG-110 and IG-430) for very high temperature reactor. Changes in density distribution and compressive strength caused by air-oxidation  

International Nuclear Information System (INIS)

Graphite materials are used for in-core components of High Temperature Gas-cooled Reactor (HTGR) and Very High Temperature Reactor (VHTR) of Generation IV reactor system. Graphite components may be oxidized by small amount of impurities in coolant helium-gas even at normal operation, as well as by air at air-ingress accident. Therefore, it is indispensable to evaluate oxidation characteristics and associated decrease in strength. In this study, by air-oxidation test at 520-900degC, oxidation characteristics of IG-110 and IG-430 graphites, supposed to be used for the core components of HTGR (including VHTR), and associated decrease in compressive strength were examined. The following results were obtained. 1) The activation energy of the air-oxidation for IG-430 is 176kJ/mol being almost same as for IG-110, though the oxidation rate for IG-430 is less than a half of that for IG-110. 2) There are correlations between density change and decrease in compressive strength. Decrease in strength is the largest in case that the oxidation temperature is lower than 600degC where the homogenous oxidation occurs. 3) In the process of oxidation, amorphous binder regions are predominantly oxidized. It suggests that peeling-off of cokes grains is necessary to be considered for oxidation weight loss, as well as gasification. (author)

370

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

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

2004-12-01

371

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

Directory of Open Access Journals (Sweden)

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

2004-12-01

372

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

Scientific Electronic Library Online (English)

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

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

2008-08-01

373

Wellhead protection strategies in unconfined fractured-rock aquifers  

International Nuclear Information System (INIS)

The US EPA has published guidelines for delineating wellhead protection areas (WPHAs) in granular, porous, unconfined aquifers. This study was funded by the US EPA to test methods for WHPA delineation in unconfined fractured-rock settings. The authors tested several delineation methods at two sites in Wisconsin. At Junction City, in central Wisconsin, fractured Precambrian metavolcanic rocks supply water for a village well. At Sevastopol, in northeastern Wisconsin, fractured Silurian dolomite forms an important regional aquifer. Field data collected at each site showed that WHPA delineation in such settings is complex and can require transient, three-dimensional analyses. At Sevastopol, borehole television, flowmeter, temperature, and other geophysical logs delineated conductive horizontal zones in the dolomite. At Junction City most groundwater movement occurs through a shallow fractured zone, and few fractures occur at greater depth. After determining the local hydrogeologic settings, the authors delineated WHPAs at both sites using a variety of methods ranging from simple arbitrary approaches to complex numerical models. The most straightforward method involved calculating the zone of contribution based on water-table maps and well hydraulics. This flow-system mapping method assumes that the approach utilized isotopic (tritium, oxygen-18) and other geochemical indicators to estimate the age and source of groundwater. The final method included detailed numerical modnal method included detailed numerical modeling coupled with an advective particle-tracking code

374

Chemical Stabilisation of Sand Part IX: Orthophthalate type Unsaturated Polyester Resin for Inducing Fast setting Behaviour and High Strength  

Directory of Open Access Journals (Sweden)

Full Text Available Polymer concrete composites have been made from orthophthalate-type unsaturated polyester resin, methyl ethyl ketone peroxide as initiator, cobalt naphthenate as accelerator and desert sand as filler. Composites preferred using resin (10-25 per cent, initiator (4 per cent and accelerator (2 per cent with representative desert sand samples of different particle sizes (0.2-0.02 mm, 2-0.2 mm and 4-2 mm as filler recorded unconfined compression strength ranging from 4 to 442 kg/cm/sup 2/ after curing at 50 degree centigrade in an oven for 0.5-24 h. Using coarse and fine sand samples with 10 and 15 per cent resin systems the maximum strength of 391 and 326 kg/cm/sup 2/ respectively was attained after 2 h of curing at 50 degree centigrade. The fast setting resin system with strength in this range is quite adequate for the construction of chemically stabilised surfaces, which withstand trafficability of vehicles, operation of helicopters and aircraft's requiring a maximum strength up to 275 kg/cm/sup 2/. These composites may prove useful for rapid repair of roads, helipads and runways damaged during operational activities. A mathematical model has been developed for predicting resin percentage needed for obtaining composite material of requisite strength. The observed and model predicted values have been found to show close agreement.

B. P. Gupta

2013-04-01

375

Projection-based Model Reduction of Unconfined Groundwater Systems  

Science.gov (United States)

Groundwater management is enhanced by the development and implementation of mathematical models to evaluate the effects on an aquifer system of various management actions. These evaluations often require a large number of simulations to conduct advanced analyses such as optimization of pumping schedules. Such analyses are intractable for complex, highly-discretized, or regional-scale models with large computational requirements. Therefore, reducing the computational burden associated with these models will provide opportunities for the application of optimization tools and other advanced analyses to a wider spectrum of groundwater management problems. Projection-based model reduction techniques have been shown to be very effective for reducing the computational burden of large-scale simulations. This type of model reduction involves construction of a projection matrix that is used to reduce the state dimensionality of a model by applying principal component analysis (PCA) to identify the components of the original model that have the largest impact on its output. It is also referred to as Proper Orthogonal Decomposition (POD). The projection-based reduction technique preserves the underlying physics of the system and removes components that do not provide significant information to the simulation. Previous researchers have reduced the dimensionality of the confined groundwater equation by three orders of magnitude using POD. To date, POD has only been applied to linear models such as the confined groundwater equation. A novel approach is proposed in this paper that combines the Newton formulation of the unconfined groundwater equation with a projection-based model reduction technique similar to POD. The proposed methodology is applied to the Newton formulation of MODFLOW (MODFLOW-NWT). We first validate the proposed methodology on a 1-D, unconfined MODFLOW-NWT model that solves 100 equations per time step (100-node model) and produced equivalent results by solving 10 equations per time step. We then apply the methodology to a 3-D, unconfined MODFLOW-NWT model. The original full-scale model with 500,000 nodes is reduced to 100 nodes, with about 1% error.

Nishikawa, T.; Boyce, S. E.; Yeh, W.

2013-12-01

376

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

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

2012-06-01

377

Unconfined deflagrative explosions without turbulence: experiments and model  

International Nuclear Information System (INIS)

This paper reviews laboratory, balloon and open field experiments which have been performed to study the deflagration regime in free air. In a first part, are considered different models available to estimate deflagrative unconfined explosions effects, without turbulence. Then, a description is given of the known performed tests, which indicate the effective scale of various experiments, their operating conditions and the type of measurements carried out. Results are presented and discussed. The influence on the explosion force of different parameters (fuel concentration gradients, flammable mixture shape and size, ignition energy) is estimated. The overall conclusion of this survey is that flammable mixtures drifting over open field and ignited, will burn with low flame speed and consequently will generate very weak pressure effects

378

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

Scientific Electronic Library Online (English)

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

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

2005-12-01

379

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  

OpenAIRE

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 ligh...

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

2005-01-01

380

Compósitos de cimento Portland com adição de nanotubos de carbono (NTC): Propriedades no estado fresco e resistência à compressão / Portland cement composites with carbon nanotubes (CNT) addition: Properties in freshly state and compressive strength  

Scientific Electronic Library Online (English)

Full Text Available Alguns estudos têm sido desenvolvidos sobre a adição de nanotubos de carbono (NTCs) em compósitos cimentícios e indicam melhorias nas propriedades mecânicas, como aumento da resistência à compressão, à tração e diminuição da porosidade. Com base nessas possíveis melhorias, essa pesquisa foi realizad [...] a para analisar a influência dos NTCs na resistência à compressão e fluidez de compósitos de cimento Portland que possam ser usados para reabilitação de estruturas de concreto. Desse modo, foram realizados ensaios de resistência à compressão, squeeze flow, flow table, funil de Marsh e miniabatimento. Foram fixadas uma argamassa e uma pasta de referência (sem adição de nanotubos de carbono), que foram replicadas com mesmo traço e a incorporação de 5 teores de NTCs em relação à massa de cimento: 0,1%, 0,2%, 0,3%, 0,4% e 0,5%. Estes teores foram escolhidos de modo a abranger a faixa de teores mais usadas nas pesquisas sobre NTCs adicionados aos compósitos de cimento Portland. Com relação aos ensaios de medição de fluidez, foi constatado que quanto maior o teor de NTC, mais consistente o compósito cimentício, com indícios de que os teores menores ou iguais a 0,3% são mais adequados para manter a fluidez do compósito de cimento Portland. No caso da resistência à compressão, os resultados indicam que a adição de 0,40% de nanotubos de carbono tende a elevar a resistência em 27%. Por outro lado, a adição de 0,5% de NTC deixou o compósito tão consistente que dificultou a moldagem e a elevação da resistência foi nula comparada a série de referência. Abstract in english Currently there are some studies on the addition of carbon nanotubes (CNTs) in cement composites. These studies indicate enhancements in the mechanical properties, such as increase in compressive strength, tensile strength and durability, and porosity decrease. Based on these possible improvements, [...] this research was conducted to analyze the influence of CNTs on the compressive strength of mortar for rehabilitation of concrete structures, as well as in their consistency. Compressive strength, squeeze flow, flow table, marsh funnel and mini-slump tests were carried. A control mortar and paste were used (without carbon nanotubes added), which was replicated with the same mix proportioning and the incorporation of 5 levels of CNTs related to the cement mass: 0.1%, 0.2%, 0.3%, 0.4% to 0.5%. These concentrations were chosen to cover the commonly range used in researches about Portland cement composites with CNTs addition. Regarding the tests for measuring the fluidity of mortars and pastes, it was found that the higher the percentage of CNT, more consistent the cement Portland composite became, with evidence that smaller or equal to 0.3% levels of NTCs are more adequate to maintain the fluidity of the Portland cement composite. Results indicate that the addition of 0.40% of carbon nanotubes increases the compressive strength by 27%. On the other hand, addition of 0.5% of CNT became the Portland cement composite very consistent, making difficult the molding process, so that the increase in compressive strength was zero compared to the control mortar.

Marcelo Henrique Farias de, Medeiros; Francielle, Dranka; Alécio Júnior, Mattana; Marienne do Rocio de Mello Maron da, Costa.

2015-03-01

381

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

382

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

2013-11-15

383

Pull Off test to evaluate the compressive strength of concrete: an alternative to Brazilian standard techniques / Ensaio de "Pull Off" para avaliar a resistência à compressão do concreto: uma alternativa aos ensaios normalizados no Brasil  

Scientific Electronic Library Online (English)

Full Text Available Estimar a resistência à compressão do concreto é uma necessidade em muitos trabalhos de inspeção de estruturas de concreto armado. No Brasil, as ferramentas regulamentadas pela ABNT para este fim são a extração de testemunho, a esclerometria e o ultrassom. Nos Estados Unidos e Europa também são regu [...] lamentadas outras técnicas. O objetivo deste trabalho é estudar a viabilidade do uso do ensaio de "Pull Off" como ferramenta de inspeção em concreto e ainda divulgar a possibilidade de emprego de técnicas complementares as normalizadas no Brasil. Os resultados demonstram que o ensaio "Pull Off" apresenta alto índice de correlação (R²>0,93) com o resultado de resistência à compressão medido tanto em corpos de prova cilíndricos como nos prismáticos. A técnica de esclerometria não apresentou correlação satisfatória (R²?0,6) para o caso de corpos de prova cilíndricos e o ultrassom apresentou alta correlação (R²>0,98), mas se comporta diferente com a mudança de forma dos corpos de prova. Abstract in english To estimate the compressive strength of concrete is necessary in many reinforced concrete structures inspection works. In Brazil, the standard tests for this purpose are: Compressive test in drilled cores, rebound hammer test and ultrasonic test. In the United States and Europe are also regulated ot [...] her techniques. The aim of this paper is to analyze the use of Pull Off test as an inspection tool of concrete and also disclose the possibility of use of complementary techniques to the standard ones in Brazil. The results show that the Pull Off test results in high correlation (R²> 0.93) with the compressive strength, measured in cylindrical and prismatic specimens. The rebound hammer test did not show satisfactory correlation (R²?0.6) for the case of cylindrical specimens. The ultrasonic test showed high correlation (R²> 0.98), but behaves differently with the shape changing of the specimens.

E., Pereira; M. H. F. de, Medeiros.

2012-12-01

384

Synthesis of Zinc Oxide Nanoparticles and Their Effect on the Compressive Strength and Setting Time of Self-Compacted Concrete Paste as Cementitious Composites  

Directory of Open Access Journals (Sweden)

Full Text Available In the present study, the mechanical properties of self-compacting concrete were investigated after the addition of different amounts of ZnO nanoparticles. The zinc oxide nanoparticles, with an average particle size of about 30 nm, were synthesized and their properties studied with the help of a scanning electron microscope (SEM and X-ray diffraction. The prepared nanoparticles were partially added to self-compacting concrete at different concentrations (0.05, 0.1, 0.2, 0.5 and 1.0%, and the mechanical (flexural and split tensile strength of the specimens measured after 7, 14, 21 and 28 days, respectively. The present results have shown that the ZnO nanoparticles were able to improve the flexural strength of self-compacting concrete. The increased ZnO content of more than 0.2% could increase the flexural strength, and the maximum flexural and split tensile strength was observed after the addition of 0.5% nanoparticles. Finally, ZnO nanoparticles could improve the pore structure of the self-compacted concrete and shift the distributed pores to harmless and less-harmful pores, while increasing mechanical strength.

Mohammad Reza Arefi

2012-04-01

385

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

OpenAIRE

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 o...

Olarescu, Cristina; Campean, Mihaela; Porojan, Mihaela

2013-01-01

386

Strength properties of sandy soil-cement admixtures  

OpenAIRE

This paper will focus on the sensitivity of strength and stiffness properties of silty-sands, from granitic residual soil, which can be converted to a highly improved material if stabilized with cement. The study of soil stabilization with cement demands to quantify the influence of the cement percentage, porosity and water content adopted in the admixing process for different stresses and physical states. Firstly, this influence was quantified in terms of the unconfined strength and maximum ...

Sara Rios; António Joaquim Pereira Viana Da Fonseca

2009-01-01

387

Tidal influence on seawater intrusion in unconfined coastal aquifers  

Science.gov (United States)

Studies of seawater intrusion in unconfined coastal aquifers typically neglect oceanic oscillations such as tides and assume a static seaward boundary condition defined by the mean sea level. Laboratory experiments and numerical simulations were conducted to investigate the influence of tidal oscillations on the behavior of the saltwater wedge. For the conditions examined, the experiments showed that an upper saline plume formed in the intertidal zone due to tide-induced seawater circulation. The presence of the upper saline plume shifted the fresh groundwater discharge zone seaward to the low-tide mark and restricted the intrusion of the saltwater wedge. The overall seawater intrusion extent, as indicated by the wedge toe location, was reduced significantly compared with the nontidal (static) case. Results from the numerical model matched these experimental observations and further demonstrated the similar type of tidal influence on the saltwater wedge in a field-scale aquifer system. The Glover (1959) solution for predicting the saltwater wedge was modified to account for the tidal effect by including the tide-induced circulation as a "recharge" to the aquifer. The findings highlight the significant impact of the tide in modulating the groundwater behavior and salt-freshwater dynamics, not only within but also landward of the intertidal zone.

Kuan, Woei Keong; Jin, Guangqiu; Xin, Pei; Robinson, Clare; Gibbes, Badin; Li, Ling

2012-02-01

388

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

389

Temperature and moisture content effects on compressive strength parallel to the grain of paricá / Efeito da temperature e do teor de umidade na resistência à compressão paralela às fibras do paricá  

Scientific Electronic Library Online (English)

Full Text Available O objetivo deste estudo é avaliar o efeito da temperatura e do teorde umidade na resistência à compressão paralela às fibras do paricá (Schizolobium amazonicum Huber ex. Ducke) de florestas plantadas. Os experimentos foram realizados em 3 amostras de madeira em diferentes condições: aquecida (HT), t [...] ratamento térmico (TT), e saturada em água (WS). A amostra HT consistiu-se de 105 corpos de prova classificados em 15 grupos, a amostra TT consistiu-se em corpos de prova classificados em 15 grupos, a amostra WS consistiu-se em 90 corpos de prova classificados em 9 grupos. Os corpos de prova das amostras HT e WS foram testados em uma faixa de temperatura de 20 a 230 ºC e de 20 a 100 ºC, respectivamente. Os corpos de prova da amostra HT foram testados à temperatura ambiente, mas após serem submetidos a um tratamento térmico. As amostras HT, TT e WS apresentaram redução da resistência à compressão, as quais atingiram 65%, 76% e 59% da resistência à compressão à temperatura ambiente, respectivamente. A redução da resistência à compressão das amostras de HT e WS pode ser associada à degradação térmica dos polímeros da madeira e da redução do teor de umidade. Para a amostra TT, a resistência dos corpos de prova aumentou para uma temperatura de pré-aquecimento de até 170 °C, devido à redução do teor de umidade. Abstract in english The aim of this study is to evaluate the effect of the temperature and moisture content on the compressive strength parallel to the grain of paricá (Schizolobium amazonicum Huber ex. Ducke) from cultivated forests. The experiments were carried out on 3 timber samples under different conditions: heat [...] ed (HT), thermal treatment (TT) and water saturated (WS). The HT sample consisted of 105 clear specimens assembled in 15 groups, the TT consisted of 90 clear specimens assembled in 15 groups and the WS consisted of 90 clear specimens assembled in 9 groups. The specimens from HT and WS samples were tested at a temperature range from 20 to 230 ºC and 20 to 100 ºC, respectively. The HT specimens were tested at ambient temperature, but after being submitted to thermal treatment. The HT, TT and WS samples present a decrease in the compressive strength, reaching 65%, 76% and 59% of the compressive strength at room temperature, respectively. The decrease in the compressive strength of the HT and WS samples can be associated to the thermal degradation of wood polymers and the moisture content. For the TT sample, the strength increased for a pre-heating temperature of up to 170 °C due to the reduction in the moisture content of the specimens.

Manuel Jesús Manríquez, Figueroa; Poliana Dias de, Moraes; Fernanda Almeida, Maestri.

2015-03-01

390

Modelamiento de la resistencia a la compresión de concretos alternativos, usando la metodología de superficie de respuesta / Modeling of the compressive strength of alternative concretes using the response surface methodology  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish 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 3,6 y 4,4. Los resultados a 28 días de curado se analizaron a través de la Metodología de Superficie de Respuesta (M.S.R) considerando como variables en estudio: el contenido de MK en el cementante (CMK) y la relación molar SiO2/Al2O3 (Rm). A partir del modelo estadístico obtenido, se presentan los contornos de resistencia a la compresión de estos materiales en función de los factores en estudio y se predice que los concretos producidos con cementos alternativos con una relación GBFS/(GBFS+MK) de 0,9 y con un Rm de 4,2, podrían desarrollar resistencias a la compresión de hasta 74 MPa. Cabe anotar que los concretos basados en sistemas binarios de GBFS/ MK presentan resistencias a la compresión de hasta 56 MPa y 80 MPa, a 7 y 180 días de curado respectivamente, comportamiento característico de materiales de alto desempeño mecánico. Abstract in english In this paper is to present the compressive strength reported by alternative concrete at ages of curing of 7, 28, 90 and 180 days. These materials were produced applying alkaline activation processes to binary systems based on granulated-blast furnace slag (GBFS) and high purity metakaolin (MK). As [...] alkali-activator a waterglass solution (Na2SiO3.nH2O + NaOH) was used and its dosages were adjusted in order to get a SiO2/Al2O3 molar ratio between 3.6 and 4.4. The results at 28 days of curing were analyzed through the statistical methodology of response surface (M.S.R). As study factors have been considered: the amount of MK into the binder (CMK) and the SiO2/Al2O3 molar ratio in the binder (Rm). From the proposed statistical model the compressive strength contours, as function of the binder variables, are identified and it is predicted that concretes elaborated from alternative binders with a GBFS/(GBFS+MK) ratio of 0.9 and Rm of 4.2, it is possible to obtain compressive strengths up to 74 MPa. It important stand out that concrete composed by binary systems of GBFS/MK to develop compressive strengths up to 56 MPa at 7 days of curing and up to 80 MPa at 180 days of curing, which is expected for high mechanical performance materials.

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

2009-09-01

391

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 Objetivo: Evaluar in vitro la resistencia compresiva de un sellante resinoso fluorado (F) pre y post liberación de flúor luego de la inmersión en agua. Método: Se utilizaron 40 probetas de 6 mm de alto y 20 mm de diámetro de sellante resinoso fluorado (FluroShield, Brasil, Dentsply) y de sellante no [...] fluorado (Concise(TM) Light Cured White Sealant, USA, 3M ESPE). Las probetas fueron divididas en cuatro grupos, dos de sellante resinoso fluorado (F1 y F2) y dos de control (C1 y C2). Un grupo de probetas de sellante fluorado y un grupo del control (F1/C1) se mantuvieron sin exposición al agua, mientras que los grupos restantes (F2/C2) fueron inmersos en agua destilada por 30 días. Se midió la liberación de flúor desde el grupo F2 mediante el método de electrodo selectivo los días 1, 2, 3 y 30. Posteriormente se midió la resistencia compresiva mediante una máquina de ensayos mecánicos universales (Lloyd, LR 100, UK) con una velocidad de cruceta de 1 mm/min. Las comparaciones entre los grupos F1 vs F2 y C1 vs C2 se analizaron con t-Student. El nivel de significancia se estableció a 0.05. Resultados: La resistencia compresiva en MPa antes y después de la inmersión en agua para el sellante resinoso fluorado fue 337.2 y 337.4, mientras que la del sellante control fue 203.8 y 213.4. Para ambos grupos las diferencias observadas no fueron significativas. Se observó un patrón de liberación de flúor inicial de 1.9 ppm durante las primeras 24 horas para luego decaer a 0.0 ppm al tercer día de liberación. Conclusión: La liberación de flúor desde un sellante resinoso fluorado no afectó su resistencia compresiva en este estudio in vitro. Abstract in english Aim: To evaluate in vitro compressive strength of fluoride-containing resin-based sealant (F) before and after fluoride release in water. Materials and Methods: We used 40 specimens with 6 mm of height and 20 mm of diameter using fluoride-containing resin-based sealant (FluroShield,Brasil, Dentsply) [...] and non-fluoride-containing resin-based sealant (Concise (TM) Light Cured White Sealant, USA, 3M ESPE). The specimens were divided into four groups, two fluoride-containing resin-based sealants (F1 and F2) and two like control groups (C1 and C2). A group of specimens of fluoride-containing resin-based sealant and a control group (F1/C1) remained without exposure to water, while other groups (F2/C2) were immersed in distilled water for 30 days. The release of fluoride from the F2 was measured through selective electrode method on days 1, 2, 3 and 30. Subsequently, the compressive strength was measured using a universal testing machine (Lloyd, LR 100, UK) with a crosshead speed of 1 mm/min. Comparisons between groups F1 vs F2 and C1 vs C2 were analyzed with t-Student. The significance level was set at 0.05. Results: The compressive strength (Mpa) before and after immersion in water for fluoride-containing resin-based sealant was 337.2 and 337.4, while the control sealant was 203.8 and 213.4. For both groups the observed differences were not significant. The initial fluoride release was 1.9 ppm during the first 24 hours and then declined to 0.0 ppm during the third day of release. Conclusion: In this in vitro study, the release of fluoride from a fluoride-containing resin-based sealant does not affect compressive strength.

C, Vergara; S, Uribe.

2012-04-01

392

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

Science.gov (United States)

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