Showing papers on "Compressive strength published in 2008"
TL;DR: The following are described with regard to biomedical applications of titanium alloys: the Young's modulus, wear properties, notch fatigue strength, fatigue behaviour on relation to ageing treatment, and multifunctional deformation behaviours of Titanium alloys.
Abstract: Young's modulus as well as tensile strength, ductility, fatigue life, fretting fatigue life, wear properties, functionalities, etc., should be adjusted to levels that are suitable for structural biomaterials used in implants that replace hard tissue. These factors may be collectively referred to as mechanical biocompatibilities. In this paper, the following are described with regard to biomedical applications of titanium alloys: the Young's modulus, wear properties, notch fatigue strength, fatigue behaviour on relation to ageing treatment, improvement of fatigue strength, fatigue crack propagation resistance and ductility by the deformation-induced martensitic transformation of the unstable beta phase, and multifunctional deformation behaviours of titanium alloys.
1,022 citations
TL;DR: In this paper, the authors used regression analysis to determine the correlation of the yield strength and the tensile strength to the diamond pyramid hardness values for over 150 nonaustenitic, hypoeutectoid steels.
Abstract: Hardness values as well as yield and tensile strength values were compiled for over 150 nonaustenitic, hypoeutectoid steels having a wide range of compositions and a variety of microstructures. The microstructures include ferrite, pearlite, martensite, bainite, and complex multiphase structures. The yield strength of the steels ranged from approximately 300 MPa to over 1700 MPa. Tensile strength varied over the range of 450-2350 MPa. Regression analysis was used to determine the correlation of the yield strength and the tensile strength to the diamond pyramid hardness values for these steels. Both the yield strength and tensile strength of the steels exhibited a linear correlation with the hardness over the entire range of strength values. Empirical relationships are provided that enable the estimation of strength from a bulk hardness measurement. A weak effect of strain-hardening potential on the hardness-yield strength relationship was also observed.
701 citations
TL;DR: In this article, a rice husk ash (RHA) prepared from the boiler burnt husk residue of a particular rice mill has been evaluated for optimal level of replacement as blending component in cements.
513 citations
TL;DR: This study insures that reusing waste plastic as a sand-substitution aggregate in concrete gives a good approach to reduce the cost of materials and solve some of the solid waste problems posed by plastics.
438 citations
TL;DR: Training and testing results have shown that artificial neural networks and fuzzy logic systems have strong potential for predicting 7, 28 and 90 days compressive strength of concretes containing fly ash.
407 citations
25 Oct 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the authors investigated the mechanical properties of polypropylene hybrid fiber-reinforced concrete and showed that the compressive strength, splitting tensile strength, and flexural properties of the hybrid fiber reinforced concrete are better than the properties of single fiber-based concrete.
Abstract: This paper investigates the mechanical properties of polypropylene hybrid fiber-reinforced concrete. There are two forms of polypropylene fibers including coarse monofilament, and staple fibers. The content of the former is at 3 kg/m3, 6 kg/m3, and 9 kg/m3, and the content of the latter is at 0.6 kg/m3. The experimental results show that the compressive strength, splitting tensile strength, and flexural properties of the polypropylene hybrid fiber-reinforced concrete are better than the properties of single fiber-reinforced concrete. These two forms of fibers work complementarily. The staple fibers have good fineness and dispersion so they can restrain the cracks in primary stage. The monofilament fibers have high elastic modulus and stiffness. When the monofilament fiber content is high enough, it is similar to the function of steel fiber. Therefore, they can take more stress during destruction. In addition, hybrid fibers disperse throughout concrete, and they are bond with mixture well, so the polypropylene hybrid fiber-reinforced concrete can effectively decrease drying shrinkage strain.
367 citations
TL;DR: In this article, the authors investigated the relationship between strength and petrographical properties of sandstones, to construct a database as large as possible, to perform a logical parameter selection routine, and to develop a general prediction model for the uniaxial compressive strength.
360 citations
TL;DR: A major conclusion of this investigation is that the role of the organic layer is primarily to subdivide the CaCO(3) matrix into platelets with thickness of 0.5 microm, which may not be significant in providing a glue between adjacent tiles.
Abstract: The nacreous portion of the abalone shell is composed of calcium carbonate crystals interleaved with layers of viscoelastic proteins. The resulting structure yields unique mechanical properties. In this study, we focus on the thin viscoelastic layers between the tiles and on their role on the mechanical properties of the shell. Both SEM and AFM show that the thin (approximately 30 nm) organic layer is porous, containing holes with diameter of approximately 50 nm. These holes enable the formation of mineral bridges between adjacent tile layers. The mineral bridges play a pivotal role in growth and ensure the maintenance of the same crystallographic relationship through tile growth in the 'terraced cone' mode. The existence of mineral bridges is consistent with the difference between tensile and compressive strength of the abalone. Mechanical tests with loading applied perpendicular to the plane of the organic layers reveal a tensile strength lower than 10 MPa, whereas the compressive strength is approximately 300-500 MPa. These nanoscale bridges have, by virtue of their dimensions (50 nm diameter x 30 nm length), a strength that reaches their theoretical value. The calculated tensile strength based on the theoretical strength predicts a bridge density of approximately 2.25/microm(2). A major conclusion of this investigation is that the role of the organic layer is primarily to subdivide the CaCO(3) matrix into platelets with thickness of 0.5 microm. Its intrinsic effect in providing a glue between adjacent tiles may not be significant.
343 citations
TL;DR: In this paper, numerical analyses are performed to investigate the compressive behavior of concrete-like material at high strain rates using a homogeneous macro-scale model and a heterogeneous mesoscale model.
330 citations
TL;DR: In this paper, the flexural behavior of fiber reinforced cementitious composites (FRCC) with four different types of fibers and two volume fraction contents (0.4% and 1.2%) within a nominally identical mortar matrix (56 MPa compressive strength).
Abstract: This research investigates the flexural behavior of fiber reinforced cementitious composites (FRCC) with four different types of fibers and two volume fraction contents (0.4% and 1.2%) within a nominally identical mortar matrix (56 MPa compressive strength). The four fibers are high strength steel twisted (T-), high strength steel hooked (H-), high molecular weight polyethylene spectra (SP-), and PVA-fibers. The tests were carried out according to ASTM standards. The T-fiber specimens showed best performance in almost all aspects of behavior including load carrying capacity, energy absorption capacity and multiple cracking behavior, while the PVA-fiber specimens exhibited comparatively the worst performance in all aspects of response. The only category in which SP-fiber specimens outperformed T-fiber specimens was deflection capacity, where SP-specimens exhibited the highest deflection at maximum load. By comparing the test results to data from an additional test program involving the use of a higher strength mortar (84 MPa) with both H- and T-fibers, it is shown that, again, T-fibers perform significantly better than H-fibers in a higher strength matrix. The test results from both experimental programs were used to critique the new ASTM standard [C 1609/C 1609M-05], and a few suggestions were made for improving the applicability of the standard to deflection-hardening FRCCs.
320 citations
TL;DR: In this article, the authors investigated the shear strength of beams and one-way slabs without stirrups based on the opening of a critical shear crack, and developed a rational model to estimate the strength of members without shear reinforcement.
Abstract: This paper investigates the shear strength of beams and one-way slabs without stirrups based on the opening of a critical shear crack. The shear-carrying mechanisms after the development of this crack are investigated. On this basis, a rational model is developed to estimate the shear strength of members without shear reinforcement. The proposed model is based on an estimate of the crack width in the critical shear region, taking also into account the roughness of the crack and the compressive strength of concrete. The proposed model is shown to properly describe a large set of available test data. A simplified method adopted by the Swiss code for structural concrete (SIA 262) is also introduced. Comparisons with other codes of practice are finally presented, with a highlight on the main differences between them.
TL;DR: In this paper, the authors used X-ray diffraction to determine the lime carbonatation kinetics of bricks made of a mixture of lime and hemp shives and found that both thermal conductivity and mechanical properties increase with the mortar density.
TL;DR: In this article, a NiAl-Mo eutectic was directionally solidified to produce composites with well-aligned single-crystal Mo-alloy fibers embedded in NiAl matrix, and then the matrix was etched away to expose free-standing micropillars having different sizes (360-1400 nm) and different amounts of pre-strain (0-11%).
TL;DR: This paper makes an attempt to apply a promising set of genetic programming techniques which are known as multi expression programming, gene expression programming (GEP) and linear genetic programming (LGP) to the uniaxial compressive strength (UCS) and tensile strength prediction of chalky and clayey soft limestone.
Abstract: Accurate determination of compressive and tensile strength of limestone is an important subject for the design of geotechnical structures. Although there are several classical approaches in the literature for strength prediction their predictive accuracy is generally not satisfactory. The trend in the literature is to apply artificial intelligence based soft computing techniques for complex prediction problems. Artificial neural networks which are a member of soft computing techniques were applied to strength prediction of several types of rocks in the literature with considerable success. Although artificial neural networks are successful in prediction, their inability to explicitly produce prediction equations can create difficulty in practical circumstances. Another member of soft computing family which is known as genetic programming can be a very useful candidate to overcome this problem. Genetic programming based approaches are not yet applied to the strength prediction of limestone. This paper makes an attempt to apply a promising set of genetic programming techniques which are known as multi expression programming (MEP), gene expression programming (GEP) and linear genetic programming (LGP) to the uniaxial compressive strength (UCS) and tensile strength prediction of chalky and clayey soft limestone. The data for strength prediction were generated experimentally in the University of Gaziantep civil engineering laboratories by using limestone samples collected from Gaziantep region of Turkey.
TL;DR: In this article, 68 reinforced concrete columns were tested under uniaxial compression after being jacketed externally with carbon fiber-reinforced polymer (CFRP) sheets.
Abstract: In this study, 68 reinforced concrete columns were tested under uniaxial compression after being jacketed externally with carbon fiber-reinforced polymer (CFRP) sheets. Forty specimens were cast using low strength concrete and inadequate internal transverse reinforcement, while 28 specimens were cast with medium strength concrete and adequate internal transverse reinforcement. Thickness of the CFRP jacket, cross-section shape, concrete strength, amount of internal transverse reinforcement, corner radius, existence of predamage, loading type (monotonic or cyclic), and the bonding pattern (orientation, spacing, anchorage details, additional corner supports) of CFRP sheets were the main test parameters of this extensive experimental work. Test results showed that external confinement of columns with CFRP sheets resulted in an increase in ultimate strength and ductility. While the strength enhancement was more pronounced for specimens with circular cross section, specimens with square and rectangular cross sections exhibited larger ultimate axial deformations without a substantial loss in strength. The efficiency of retrofitting was much more pronounced in the case of relatively lower strength concrete. The proposed model, together with two other available models, were used for predicting the strength and corresponding axial deformations of more than 300 specimens tested by other researchers, as well as more than 100 specimens tested by the writers during this study and before. It was shown that the predicted results by the proposed model were in reasonable agreement with this extensive database of experimental studies.
TL;DR: In this article, the authors investigated the effect of using steel fiber and silica fume on the properties of concrete and found that the use of steel fiber increased both the mechanical strength and the modulus of the elasticity of concrete.
TL;DR: In this article, the mechanical properties of one igneous, three sedimentary and three metamorphic rock types were determined in the laboratory and correlated with P-wave velocity, which may avoid the necessity for time-consuming and tedious laboratory testing.
Abstract: Impact strength index, slake durability index and uniaxial compressive strength (UCS) are important properties of a rock mass which are used widely in geological and geotechnical engineering. In this study, the mechanical properties of one igneous, three sedimentary and three metamorphic rock types were determined in the laboratory and correlated with P-wave velocity. Empirical equations have been developed to predict the impact strength index, slake durability index and UCS from P-wave velocity, which may avoid the necessity for time-consuming and tedious laboratory testing. To check the sensitivity of the empirical relations, a t test was performed which confirmed the validity of the proposed correlations.
TL;DR: The effects of nano-SiO(2) on three ash particle sizes in mortar were studied by replacing a portion of the cement with incinerated sewage sludge ash and results indicate that the amount of water needed at standard consistency increased and a reduction in setting time became noticeable for smaller ash particles.
TL;DR: In this paper, the influence of fly ash (FA) on the properties of self-compacting concrete (SCC) is investigated and the results indicate that high volume FA can be used in SCC to produce high strength and low shrinkage.
TL;DR: The robocast calcium phosphate scaffolds were found to exhibit excellent mechanical performances in terms of strength, especially the HA structures after SBF immersion, indicating a great potential of this type of scaffolds for use in load-bearing bone tissue engineering applications.
Abstract: The mechanical behavior under compressive stresses of β-tricalcium phosphate (β-TCP) and hydroxyapatite (HA) scaffolds fabricated by direct-write assembly (robocasting) technique is analyzed. Concentrated colloidal inks prepared from β-TCP and HA commercial powders were used to fabricate porous structures consisting of a 3-D tetragonal mesh of interpenetrating ceramic rods. The compressive strength and elastic modulus of these model scaffolds were determined by uniaxial testing to compare the relative performance of the selected materials. The effect of a 3-week immersion in simulated body fluid (SBF) on the strength of the scaffolds was also analyzed. The results are compared with those reported in the literature for calcium phosphate scaffolds and human bone. The robocast calcium phosphate scaffolds were found to exhibit excellent mechanical performances in terms of strength, especially the HA structures after SBF immersion, indicating a great potential of this type of scaffolds for use in load-bearing bone tissue engineering applications. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res 2008
TL;DR: A literature survey was carried out to collect data on the properties of granites at high temperatures including Young's modulus, uniaxial compressive strength, tensile strength, Poisson's ratio, coefficient of linear thermal expansion, creep behaviour and the development of micro-crack on heating using scanning electron microscope (SEM) as mentioned in this paper.
TL;DR: The results have indicated that the systems under investigation are suited for the manufacture of pre-formed building blocks at room temperature.
TL;DR: In this paper, the properties of plain concrete and steel fiber reinforced concrete (SFRC) containing fibres of mixed aspect ratio were investigated, and various tests such as inverted cone time, Vebe time, compaction factor, and compressive strength, split tensile and static flexural strength tests were conducted.
TL;DR: In this article, three series of concretes with different compressive strength levels are presented, each series includes a reference concrete prepared with natural crushed stone and two RAC prepared with two coarse aggregates obtained by crushing a normal strength and a high strength concrete.
TL;DR: In this paper, the authors compared the properties of 12 alkali-activated mortars and a control ordinary portland cement (OPC) mortar, and found that the compressive strength development of alkali activated mortar was significantly dependent on the proposed alkali quality coefficient.
TL;DR: In this article, the authors studied the effect of the water to cement ratio (W/C), admixture and mixing time on porous concrete properties and showed that the strength of porous concrete could be estimated from strength equation of porous brittle material.
TL;DR: In this paper, the effect of different amounts of silica fume (SF) and water to cement ratios (w/c) on the residual compressive strength of high-strength concrete after exposure to high temperatures was investigated.
Abstract: This paper presents the results of an experimental investigation on the effect of different amounts of silica fume (SF) and water to cement ratios (w/c) on the residual compressive strength of high-strength concrete after exposure to high temperatures. Based on the results obtained the rates of strength loss for concrete specimens containing 6% and 10% SF at 600 °C were 6.7% and 14.1% lower than those of the ordinary concrete. The dosage of SF had no significant effect on the relative residual compressive strength at 100 and 200 °C, whereas the amount of SF had considerable influences on the residual compressive strength above 300 °C similar to the response at 600 °C. The optimum dosage of SF and w/c was found to be 6% and 0.35, respectively.
TL;DR: In this article, the authors investigated the influence of the shape and size of the specimens on the compressive strength of high-strength concrete and found that the post-peak behavior of the cubes is milder than that of the cylinders, which results in a strong energy consumption after the peak.
TL;DR: In this article, statistical equations have been determined for estimating the mechanical properties of rocks using non-destructive and indirect test methods and 19 different rock types were tested to obtain the relationships between Shore hardness, point load index, sound velocity, Schmidt hardness and porosity and uniaxial compressive strength, indirect tensile strength and abrasion resistance.
Abstract: Statistical equations have been determined for estimating the mechanical properties of rocks using non-destructive and indirect test methods. Nineteen different rock types were tested to obtain the relationships between Shore hardness, point load index, sound velocity, Schmidt hardness and porosity and uniaxial compressive strength, indirect tensile strength and abrasion resistance. Results of regression analyses showed satisfactory correlations.
TL;DR: In this article, the use of metakaolin (MK) as a supplementary cementing material to improve the performance of concrete was investigated and the results revealed that the inclusion of MK remarkably reduced the drying shrinkage strain, but increased the strength of the concretes in varying magnitudes, depending mainly on the replacement level of MK, w/cm ratio, and age of testing.
Abstract: This paper presents the results of an investigation on the use of metakaolin (MK) as a supplementary cementing material to improve the performance of concrete. Two MK replacement levels were employed in the study: 10% and 20% by weight of the Portland cement used. Plain and PC-MK concretes were designed at two water–cementitious materials (w/cm) ratios of 0.35 and 0.55. The performance characteristics of the concretes were evaluated by measuring compressive and splitting tensile strengths, water absorption, drying shrinkage, and weight loss due to the corresponding drying. The porosity and pore size distribution of the concretes were also examined by using mercury intrusion porosimetry (MIP). Tests were conducted at different ages up to 120 days. The results revealed that the inclusion of MK remarkably reduced the drying shrinkage strain, but increased the strengths of the concretes in varying magnitudes, depending mainly on the replacement level of MK, w/cm ratio, and age of testing. It was also found that the ultrafine MK enhanced substantially the pore structure of the concretes and reduced the content of the harmful large pores, hence made concrete more impervious, especially at a replacement level of 20%.