• Journal of the Korea Concrete Institute
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• v.15 no.2
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• pp.246-253
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• 2003

Although concrete members are not normally designed to resist direct tension, the knowledge of tensile strength is of value in estimating the cracking load. In general, there are three types of test method for tensile strength ; direct tension test, flexural tension test, and splitting tension test. Though direct tensile strength represents the real tensile strength of concrete, direct tension tests are seldom carried out, mainly because it is very difficult to applicate a pure tension force. The purpose of this paper is to investigate the test methods, effect of aspect ratio, and the size effect on the direct tensile strength. Direct tension test, using bonded end plates, follows RILEM and U.S.Bureau of Reclamation. And other test methods follow ASTM provisions. Four kinds of aspect ratio and two kinds of size effect are tested. Same variables are tested by direct tension test and splitting tension test for comparison between the two test methods. Test results show that direct tensile strength of concrete is more affected by aspect ratio and size than other kinds of strength.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.27-33
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• 2018

PURPOSES : The purpose of this study is to estimate the optimum content of an inorganic additive for cold-recycled asphalt mixtures and evaluate its performance. METHODS : An indirect tensile test, a tensile-strength ratio test, and an indirect tensile-fatigue test were conducted on cold-recycling asphalt mixtures with various additives. RESULTS : The laboratory performance tests indicated that granulated blast-furnace slag mixed with inorganic and cement activators provided optimum performance. The performance results of the cold-recycled asphalt pavement were similar to the inorganic and cement activators' performance in terms of the indirect tensile strength, tensile strength ratio, and indirect tensile-fatigue test. CONCLUSIONS : Overall, the performance of a cold-recycled asphalt mixture using inorganic additives and emulsion asphalt was comparable to a warm-recycled asphalt mixture. However, more experiments aimed at improving its performance and studying the effect of the inorganic additives must be conducted.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.2
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• pp.82-94
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• 1988

The purpose of this study is to introduce the Double Punch test method which is an indirect testing method of tensile strength of concrete, and to compare with the tensile strength of concrete as determined by the split-cylinder test, a practical method for performing the Double Punch test to obtain the tensile strength of concrete is proposed and recommended for general use. In this study, the dimensions of cylindrical specimens used in the Double-Punch test were 15X30cm, 15X15cm, 10${\times}$(20cm, and 5${\times}$l0cm, and in the split-cylinder test were 15${\times}$(30cm, 15${\times}$(15cm, and 10${\times}$(20cm. And the diameters of loading punches used in the Double-Punch test were 1.5cm, 2.5cm, and 3.5 cm. The results obtained from tests are summarized as follows ; 1. In the split-cylinder test, the tensile strength of concrete by the linear elasticity theory is similar to that of plasticity theory. 2. Both split-cylinder test and Double-Punch test, tensile strength of concrete is increased with decreasing specimen size. This tendency is identical when the ratio of specimen diameter to height is 1: 2, but that tendency is quite different when the ratio is 1: 3. In the Double-Punch test, if specimen size is constant, by increasing the punch size, tensile strength of concrete is increased, too. 4. Using a 15 ${\times}$( 15 cm cylinder specimen and 3.5 cm diameter punch in the Double Punch test would give the most uniform and consistent result in tensile strength, and the result showed a gQod correlation with splitting tensile strength from 15 x 30cm specimen. 5. In order to obtain satisfactory results and to nuninuze variability, it is proposed that specimens of 15 cm in diameter and 15 cm in height with two 3.5 cm diameter punches should be used. It seems, therefore, reasonable tt) take f't=0.0024 P(kg / cm$^2$) as a working formula for computing the tensile strength in the Double Punch test for concrete.

• International Journal of Highway Engineering
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• v.19 no.2
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• pp.137-142
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• 2017

PURPOSES :The objective of this study is to evaluate the performance of asphalt mixtures containing inorganic additive and a high content of reclaimed asphalt pavement (RAP). METHODS : The laboratory tests verified the superior laboratory performance of inorganic additive compared to cement, in cold recycled asphalt mixtures. To investigate the moisture susceptibility of the specimens, tensile strength ratio (TSR) tests were performed. In addition, dynamic modulus test was conducted to evaluate the performance of cold recycled asphalt mixture. RESULTS :It was determined that NaOH solution mixed with $Na_2SiO_3$ in the ratio 75:10 provides optimum performance. Compared to Type B and C counterparts, Type A mixtures consisting of an inorganic additive performed better in the Indirect tensile strength test, tensile strength ratio test, and dynamic modulus test. CONCLUSIONS : The use of inorganic additive enhances the indirect strength and dynamic modulus performance of the asphalt mixture. However, additional experiments are to be conducted to improve the reliability of the result with respect to the effect of inorganic additive.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.11
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• pp.147-154
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• 2019

The purpose of this study is to evaluate the effect of admixtures as blast-furnace slag(BF) and fly ash(FA) on tensile and adhesive properties of polymer cement mortar(PCM) with EVA emulsion. The test specimens are prepared with five polymer-cement ratio(P/C) and five admixture contents, and tested for tensile strength and adhesion in tension. From the test results, the tensile strength and adhesion in tension could be improved by an appropriate combination of P/C and admixture contents. In particular, the maximum of tensile strength of PCM with P/C 10% and BF content of 10% is 4.70MPa which is about 1.55 times higher than that of plain mortar, and about 1.22 times that of PCM that does not contain any mixture. The ratio of adhesion in tension to tensile strength of PCM with admixtures averaged 55.8%. It is also apparent that admixture contents of 5% or 10% could be proposed for improvement of tensile strength and adhesion in tension of PCM.

• Journal of Ocean Engineering and Technology
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• v.26 no.6
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• pp.19-26
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• 2012

Recently the world has been suffering from difficulties related to the demand and supply of energy due to the democratic movements sweeping across the Middle East. Consequently, many have turned their attention to never-developed extreme regions such as the polar lands or deep sea, which contain many underground resources. This research investigated the strength and initial elastic modulus values of eternally frozen ground through a uniaxial compression test and indirect tensile test using frozen artificial soil specimens. To ensure accurate test results, a sandymud mixture of standard Jumunjin sand and kaolinite (20% in weight) was used for the specimens in these laboratory tests. Specimen were prepared by varying the water content ratio (7%, 15%, and 20%). Then, the variation in the strength value, depending on the water content, was observed. This research also established three kinds of environments under freezing temperatures of $-5^{\circ}C$, $-10^{\circ}C$, and $-15^{\circ}C$. Then, the variation in the strength value was observed, depending on the freezing environment. In addition, the tests divided the loading rate into 6 phases and observed the variation in the stress-strain ratio, depending on the loading rate. The test data showed that a lower freezing temperature resulted in a larger strength value. An increase in the ice content in the specimen with the increase in the water content ratio influenced the strength value of the specimen. A faster load rate had a greater influence on the uniaxial compression and indirect tensile strengths of a frozen specimen and produced a different strength engineering property through the initial tangential modulus of elasticity. Finally, the long-term strength under a constant water content ratio and freezing temperature was checked by producing stress-strain ratio curves depending on the loading rate.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.8
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• pp.131-138
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• 2019

Since concrete has a low tensile strength compared to the compressive strength, reinforced concrete flexural members represent easy crack occurance under a small load. In order to overcome this problem, steel fiber reinforced concrete has been developed to compensate the tensile strength and brittleness of members. However, in the design formula of the domestic building code, it is not specified in the design formula reflecting the material characteristics. Therefore, the field application of the steel fiber reinforced concrete have had many restrictions. In this study, a flexural tensile strength model of steel fiber reinforced concrete is proposed by collecting and analyzing the material properties of material test results conducted by various researchers, and verified by the test results of cracking and stiffness evaluation of flexural members based on the proposed model. As a result of this study, the flexural tensile strength model of steel fiber reinforced concrete which can reflect the mixing ratio and aspect ratio of the steel fiber was proposed and the validity of the proposed material model equation was evaluated from the load-deflection relationship in the flexural test of the slab member.

• Structural Engineering and Mechanics
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• v.60 no.6
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• pp.939-952
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• 2016

A compression to tensile load transforming (CTT) device was developed to determine indirect tensile strength of concrete material. Before CTT test, Particle flow code was used for the determination of the standard dimension of physical samples. Four numerical models with different dimensions were made and were subjected to tensile loading. The geometry of the model with ideal failure pattern was selected for physical sample preparation. A concrete slab with dimensions of $15{\times}19{\times}6cm$ and a hole at its center was prepared and subjected to tensile loading using this special loading device. The ratio of hole diameter to sample width was 0.5. The samples were made from a mixture of water, fine sand and cement with a ratio of 1-0.5-1, respectively. A 30-ton hydraulic jack with a load cell applied compressive loading to CTT with the compressive pressure rate of 0.02 MPa per second. The compressive loading was converted to tensile stress on the sample because of the overall test design. A numerical modeling was also done to analyze the effect of the hole diameter on stress concentrations of the hole side along its horizontal axis to provide a suitable criterion for determining the real tensile strength of concrete. Concurrent with indirect tensile test, the Brazilian test was performed to compare the results from two methods and also to perform numerical calibration. The numerical modeling shows that the models have tensile failure in the sides of the hole along the horizontal axis before any failure under shear loading. Also the stress concentration at the edge of the hole was 1.4 times more than the applied stress registered by the machine. Experimental Results showed that, the indirect tensile strength was clearly lower than the Brazilian test strength.

• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.223-234
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• 2016

In this study, direct tension test for hybrid steel fiber reinforced ultra-high performance concrete (UHPC) containing two different steel fibers with a length of 16 and 19 mm was performed to investigate the fracture behavior of UHPC. Test results showed that crack strength and tensile strength, and fracture energy increased with increasing the fiber volume ratio. Based on the test results, the peak cohesive stress at the crack tip, tensile strength, and fracture energy depending on the fiber volume ratio were proposed. The proposed tensile strength of UHPC was suggested as a function of the fiber volume ratio and compressive strength. The peak cohesive stress at the crack tip and fracture energy were also proposed as a function of the tensile strength. The predicted values were relatively agree well with the test results. Thus, the proposed equations is expected to be applicable to UHPC with a compressive strength of 140~170 MPa and a fiber volume ratio of less than 2%.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2374-2382
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• 2002

Aluminum alloy/aramid fiber reinforced plastic(Al/AFRP) laminates consists of high strength metal(A15052) and laminated aramid fiber with structural adhesive bond. The mixture ratio effect of epoxy resin curing agent accelerator on the tensile strength and T-peel strength characteristic in Al AFRP laminates were investigated in this study. The epoxy. diglycidylether of bisphenol A(DCEBA), It'as cured by methylene dianiline(MDA) with or without an accelerator(K-54). Eight different kinds of resin mixture ratios were selected for the test , five kinds of Al/AFRP laminates were named as Al/AFRP(1) and three others of Al/AFRP laminates were named as Al/AFRP(2). The comparison of tensile strength and T-peel strength with variation of resin mixture ratio were studied. Respectively. Al/AFRP(1) and Al/AFRP(2) indicated approximately 6.0 times and 7.0 times more improved maximum tensile strength in comparison with those of monolithic A15052. Al/AFRP(2) indicated approximately 1.5 times more impoved maximum T-peel strengths in comparison with those of Al/AFRP(1). As results. Al/AFRP(2) turned out to have more effective characteristics on the tensile strength and T-peel strength than those of Al/AFRP(1).