• Geomechanics and Engineering
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• v.17 no.3
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• pp.261-270
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• 2019

Because the estimation of the tensile strength is very important in any geotechnical project, many attempts have been made to determine. But the immediate determination of the tensile strength is usually difficult owing to well-shaped specimens, time-consuming, expensive and sometimes unreliable. In this study, engineering properties of several ultramafic rock samples were measured to assess the correlations between the Brazilian Tensile Strength (BTS) and degree of serpentinization, physical, dynamic and mechanical characteristics. For this purpose, a comprehensive laboratory testing program was conducted after collecting thirty-two peridotite and fifty-one serpentinite rock samples, taken from central Greece, in accordance with ASTM and ISRM standards. In addition, a representative number of them were subjected to petrographic studies and the obtained results were statistically described and analysed. Simple and multiple regression analyses were used to investigate the relationships between the Brazilian Tensile Strength and the other measured properties. Thus, empirical equations were developed and they showed that all of the properties are well correlated with Brazilian Tensile Strength. The curves with the $45^{\circ}$ line (y = x) were extracted for evaluating the validity degree of concluded empirical equations which approved approximately close relationships between Brazilian Tensile Strength and the measured properties.

• International Journal of Concrete Structures and Materials
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• v.10 no.1
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• pp.29-37
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• 2016

The paper presents a research project on the tensile properties of RPC mixed with both steel and polypropylene fibers after exposure to $20-900^{\circ}C$. The direct and the indirect tensile strength (in bending) were measured through tensile experiment on dog-bone specimens and bending experiment on $40{\times}40{\times}160mm$ prisms. RPC microstructure was analyzed using scanning electron microscope. The results indicate that, steel fibers can significantly improve the tensile performance of hybrid fiber-reinforced RPC, whereas polypropylene fibers have no obvious effect on the tensile performance. With increasing temperature, the flexural and axial tensile strength of hybrid fiber-reinforced RPC substantially decrease linearly, which attributes to the deteriorating microstructure. Based on the experimental results, equations are established to express the decay of the flexural and tensile strength with increasing temperature.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.4
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• pp.83-92
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• 1989

For many of the rigid pavements the observations of significantly different performances were explained to relate distress mechanisms to distress manifestation and to develope better prediction of performance. This paper summarizes the result of an investigation of the resilient elastic and fatigue behavior of inservice cement concrete pavements. Static indirect tensile tests were. conducted in order to estimate the average tensile strength of each of the projects Repeat-load indirect tensile tests were conducted to determine the fatigue and resilient elastic characteristics and the relationship between fatigue life and stress/strength ratio. Deformation measurements were taken during fatigue testing in order to determine the resilient elastic properties of the material and the changes in these properties during the test period.

• International Journal of Highway Engineering
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• v.4 no.3 s.13
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• pp.35-42
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• 2002

Many temperature-related problems are created in asphalt pavement due to the low temperature. In particular, loss of tensile strength due to low temperature is known to be responsible for thermal failure of pavements in cold regions under $-20^{\circ}C$. The objective of this study is to evaluate characteristics of resistance against low-temperature cracking of polymer asphalt concrete mixtures modified with LDPE and SBS. The test results showed that the mixtures had the maximum indirect tensile strength(ITS) at low temperature ranging from $-10^{\circ}C. It was proved through ITS test that the stress due to differential thermal contraction over the tensile strength did generate internal damage at the temperature below $-20^{\circ}C$. It was shown that the asphalt mixtures modified with polymer had better ITS than the normal asphalt mixture at the temperature below $-20^{\circ}C$. Thus the effect of modification was revealed as tensile strength improvement. From the results of this study, it was recommended that polymer-modified asphalt should be used in order to prevent low-temperature cracking in cold region.

• Advances in concrete construction
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• v.4 no.3
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• pp.207-220
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• 2016

The objective of this study was to evaluate the influence of recycled materials, namely, shredded scrap tire (SST), reclaimed asphalt pavement (RAP) and class C fly ash (CFA) on compressive and tensile strength of concrete. Either SST or RAP was used as an aggregate replacement and class C fly ash (CFA) as Portland cement replacement for making concrete. A total of two types of SST and RAP, namely, chips and screenings were used for replacing coarse and fine aggregates, respectively. A total of 26 concrete mixes containing different replacement level of SST or RAP and CFA were designed. Using the mix designs, cylindrical specimens of concrete were prepared, cured in water tank, and tested for unconfined compressive strength (UCS) and indirect tensile strength (IDT) after 28 days. Experimental results showed aggregate substitution with SST decreased both UCS and IDT of concrete. On the contrary, replacement of aggregate with RAP improved UCS values. Specimens containing RAP chips resulted in concrete with higher IDT values as compared to corresponding specimens containing RAP screenings. Addition of 40% CFA was found to improve UCS values and degrade IDT values of SST containing specimens. Statistical analysis showed that IDT of SST and RAP can be estimated as approximately 13% and 12% of UCS, respectively.

• Geomechanics and Engineering
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• v.23 no.2
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• pp.165-178
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• 2020

This paper investigates the effect of the jaw's curvature, also known by contact angle and jaw arc central angle (2α), of the Brazilian test apparatus on indirect tensile strength of various rock types. That's why, ten rock samples including limestone, marble, skarn, granite, diorite, and granodiorite were collected from some quarries in different provinces of Iran. Petrographic, mineralogical and textural investigations were performed using thin section analyses. Physical properties of the selected rock samples namely dry and saturated unit weights, porosity, water absorption, and specific gravity were determined for the rock samples. In addition, Brazilian tensile strength at different 2α angles (i.e., 2α = 0°, 10°, 15°, 20°, 45°, and 60°) were determined for the rocks in the laboratory. Results show that the parameter for the rocks is between 3.81 MPa at 2α=0° and 54.76 MPa at 2α=60°. This means that Brazilian tensile strength increased with increasing 2α angle from 0° to 60°. Also, it was found that the highest change rate of the Brazilian tensile strength occurs in range of 2α=15°-30° for most studied rock samples. In some tested samples, the parameter is decreased only at 2α = 60°. The values of Brazilian tensile strength of the rocks tested by flat and standard jaws are near to each other.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.947-954
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• 2014

In general, Fracture of the material is not occurring of the maximum normal stress or the maximum shear stress failure in the state. Maximum normal stress and maximum shear stress in the state of Critical coupling from being destroyed based on the Mohr-Coulomb theory. Couple of different mixtures, including permeable asphalt pavement, SMA and dense-graded asphalt mixture, were used for compression triaxial test at $45^{\circ}C$ and $60^{\circ}C$. Mohr-Coulomb theory to the analysis of compression triaxial test result of the internal friction angle $38.9^{\circ}{\sim}46.9^{\circ}$ measured somewhat irregularly, but in the case of cohesion, depending on whether the temperature and immersion of the specimen appeared differently. In addition, Indirect tensile test and compression triaxial test of the asphalt mixture to determine the correlation between compression triaxial test results assessed as cohesion and internal friction angle calculated using the theoretical Indirect tensile strength and measured indirectly tensile strength were analyzed. The Measured & Predicted IDT St values tended to be proportional.

• Geomechanics and Engineering
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• v.10 no.6
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• pp.775-791
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• 2016

The indirect tensile strengths (ITSs) of different cemented paste backfill mixes with different curing times were determined by considering crack initiation and fracture toughness concepts under different loading conditions of steel loading arcs with various contact angles, flat platens and the standard Brazilian test jaw. Because contact area of the ITS test discs developes rapidly and varies in accordance with the deformability, ITSs of curing materials were not found convenient to determine under the loading apparatus with indefinite contact angle. ITS values increasing with an increase in contact angle can be measured to be excessively high because of the high contact angles resulted from the deformable characteristics of the soft paste backfill materials. As a result of the change of deformation characteristics with the change of curing time, discs have different contact conditions causing an important disadvantage to reflect the strength change due to the curing reactions. In addition to the experimental study, finite element analyses were performed on several types of disc models under various loading conditions. As a result, a comparison between all loading conditions was made to determine the best ITSs of the cemented paste backfill materials. Both experimental and numerical analyses concluded that loading arcs with definite contact angles gives better results than those obtained with the other loading apparatus without a definite contact angle. Loading arcs with the contact angle of $15^{\circ}$ was found the most convenient loading apparatus for the typical cemented paste backfill materials, although it should be used carefully considering the failure cracks for a valid test.

• International Journal of Highway Engineering
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• v.17 no.1
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• pp.77-82
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• 2015

PURPOSES : The purpose of this paper is to evaluate the moisture susceptibility of asphalt mixtures containing developed liquid anti-stripping agents using the boiling water test as a screening test. METHODS : The boiling water test was used to evaluate the moisture susceptibility of asphalt mixtures containing different anti-stripping agents. The tensile strength ratio was calculated to compare the moisture susceptibility of the asphalt mixtures after indirect strength tests were performed. Additionally, image analysis techniques were used to calculate and analyze the quantity of stripped area in the asphalt mixtures. RESULTS : In general, the asphalt mixtures containing anti-stripping agents showed a higher resistance of anti-stripping based on the boiling water test and tensile strength ratio. CONCLUSIONS : The boiling water test can be used to differentiate the resistance of moisture susceptibility of asphalt mixtures, except for asphalt mixtures containing hydrated lime. The boiling water test can be used as a screening test for asphalt mixtures before conducting time consuming and expensive indirect tensile strength tests.

• Geomechanics and Engineering
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• v.16 no.5
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• pp.559-567
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• 2018

Technological innovations in sustainable materials for soil improvement have attracted considerable interest due to energy crisis and environmental concerns in recent years. This study presents results of a comprehensive investigation on utilization of nanocarbons in reinforcement of a residual soil mixed with 0, 10 and 20% bentonite. Effects of adding proportionate quantities (0, 0.05, 0.075, 0.1 and 0.2%) of carbon nanotubes and carbon nanofibers to soil samples of different plasticities were evaluated. The investigation revealed that the inclusion of nanocarbons into the soil samples significantly improved unconfined compressive strength, Young's modulus and indirect tensile strength. It was observed that carbon nanofibers showed better performance as compared to carbon nanotubes. The nanosized diameter and high aspect ratio of nanocarbons make it possible to distribute the reinforcing materials on a much smaller scale and bridge the inter-particles voids. As a result, a better 'soil-reinforcing material' interaction is achieved and desired properties of the soil are improved at nanolevel.