• Computers and Concrete
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• v.12 no.4
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• pp.377-392
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• 2013

This paper investigates prediction models estimating the hydration properties of concrete, such as the compressive strength, the splitting tensile strength, the elastic modulus,and the autogenous shrinkage. A prediction model is suggested on the basis of an equation that is formulated to predict the compressive strength. Based on the assumption that the apparent activation energy is a characteristic property of concrete, a prediction model for the compressive strength is applied to hydration-related properties. The hydration properties predicted by the model are compared with experimental results, and it is concluded that the prediction model properly estimates the splitting tensile strength, elastic modulus, and autogenous shrinkage as well as the compressive strength of concrete.

• Advances in concrete construction
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• v.1 no.4
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• pp.305-318
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• 2013

Engineering properties such as compressive strength, splitting tensile strength, modulus of rupture, modulus of elasticity and Poisson's ratio of geopolymer concrete (GPC) and steel fibre reinforced geopolymer concrete (SFRGPC) have been obtained from standard tests and compared. A total of 15 specimens were tested for determining each property. The grade of concrete used was M 40. The percentages of steel fibres considered include 0.25%, 0.5%, 0.75% and 1%. In general, the addition of fibres improved the mechanical properties of both GPC and SFRGPC. However the increase was found to be nominal in the case of compressive strength (8.51%), significant in the case of splitting tensile strength (61.63%), modulus of rupture (24%), modulus of elasticity (64.92%) and Poisson's ratio (50%) at 1% volume fraction of fibres. An attempt was made to obtain the relation between the various engineering properties with the percentage of fibres added.

• Advances in materials Research
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• v.8 no.2
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• pp.103-115
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• 2019

Polypropylene (PP) fibers for making fabric which is used for packing cement have a high strength and high tear resistance. Due to these excellent properties the present study investigates the effect of PP fibers on the mechanical strength of concrete. Mechanical strength parameters such as compressive strength, splitting tensile strength and flexural strength are evaluated. Structural integrity of concrete using Ultrasonic Pulse Velocity (UPV) was also studied. Concrete containing PP fibers in percentage of 0%, 0.15%, 0.25%, 0.5% and 0.75% was developed with a characteristic compressive strength of 25 MPa. Concrete cubes, cylinder and prismatic specimens were cast and tested. It was found that the UPV values recorded for all specimens were of the similar order. Test results indicated the used of PP fibers can significantly improve the flexural and splitting tensile strengths of concrete materials whereas it resulted a decreased in compressive strength. The relative increase in split tensile and flexural strength was optimum at a fiber dosage of 0.5% and a mild decreased were observed in 28 days compressive strength. The findings in this paper suggested that PP fibers deriving from these waste cement bags are a feasible fiber option for fiber-reinforced concrete productions.

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.53-60
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• 2012

The main object of this paper is to investigate the effects of high temperatures on the physical and mechanical properties of natural sand concrete(NSC) and crushed sand concrete(CSC). Test samples were exposed to high temperature ranging from $200^{\circ}C$ to $800^{\circ}C$. After exposure, various tests were conducted. Color image analysis and weight losses were determined and compressive strength test and splitting tensile strength test were conducted. The results indicated that weight losses increased as exposure temperature increased with comparable decreasing rate. The results also showed that compressive strength and splitting tensile strength and modulus of elasticity decreased as exposure temperature increased. The results also showed that residual compressive strength of NSC decreased more drastically than that of CSC at $200^{\circ}C$ and $400^{\circ}C$. Residual splitting tensile strength of NSC decreased more than that of CSC at $200^{\circ}C$, while NSC and CSC showed comparable residual strength ratio at $800^{\circ}C$.

• Journal of the Korea Institute of Building Construction
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• v.5 no.2 s.16
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• pp.89-95
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• 2005

Various tests are performed with the recycled concrete including compressive strength, flexural strength, splitting tensile strength, bonding strength and chloride ion penetration test. The basic data obtained from the presented test could be accumulated for the purpose of utilization in concrete structure. Most of the strength tests show that strength decrease a little extent with increasing substitution ratio of recycled coarse aggregate except splitting tensile test for the concrete with $100\%$ recycled fine aggregate. But in case of the $50\%$ substitution of recycled coarse aggregate, compressive strength, flexural strength and bonding strength are almost equal to the normal concrete. Chloride ion penetration test shows that the penetration amounts of chloride ion becomes more in proportion to the substitution ratio of recycled aggregate. But most of the results show that the permeability of recycled concrete is proper to use. The results of present study nay imply that the use of recycled aggregate for steam curing concrete is possible but the substitution ratio of recycled aggregate should be determined through further studies.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.41-49
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• 2014

In order to investigation splitting bond strength of the deformed longitudinal reinforcing bars in the R C members strengthened laterally with the external steel-band, a total 9 sets of test re-bars with and without active confining force given by the external steel-band are pulled monotonically until failure. Test results indicate that the bond strength becomes higher with the increase in number of steel-band sets and their initial stress magnitude. This is due to the active confining force given by the steel-band, and passive confining forces given by the steel-band and transverse reinforcements, in which the passive confinement effect varies depending on the magnitude of active confining force. An equation to estimate the splitting bond strengths for the R C members strengthened laterally with the external steel-band is developed based on the several experimental results of the present study.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.5
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• pp.25-33
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• 2011

In this paper, the effects of aggregate and curing temperature on strength development characteristics of UP (Unsaturated Polyester)-MMA (Methyl Methacrylate) based polymer mortar under sub-zero temperature are experimentally investigated to provide a criterion for repair and production of precast products. The result showed that the setting time of the binder was 4 minutes at $20^{\circ}C$ whereas 35 minutes at $-20^{\circ}C$. The result also revealed that the compressive, flexural, and splitting tensile strengths of UP-MMA based polymer mortar significantly decreased as the aggregate and curing temperatures decreased. However, sufficient strengths which can be implemented in actual practices -36.6 MPa of compressive strength, 6.11 MPa of flexural strength, and 5.81 MPa of splitting tensile strength - were obtained even though both aggregate and curing temperatures were $-20^{\circ}C$. Strength development of polymer mortar is largely affected by curing temperature rather than aggregate temperature. It was found that the effects of aggregate temperature on strength development become smaller as the curing temperature becomes lower. Also, toughness, a ratio of compressive strength to flexural strength, increased from 3.5 to 5.9 as both aggregate and curing temperatures decreased from $20^{\circ}C$ to $-20^{\circ}C$.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.112-115
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• 2004

Bond between reinforcing bar and surrounding concrete is supposed to transfer load safely in the process of design of reinforced concrete structures. Bond failure of reinforcing bar generally take place by splitting of the concrete cover as bond force between concrete and reinforcing bars exceeds the confinement of the concrete cover and reinforcement. However, the confinement force has a limitation. Thus, the only variable is the bearing angle corresponding to the change of bond force. Higher rib height bars possessing higher shearing resistance can maintain higher bearing angle and higher splitting resistance when bars are highly confined, and consequently higher bond strength, than lower rib higher bars. In this study, from the evaluate bond strength of high Relative Rib Area Bars Using beam-end test specimens are compared with the current provisions for development of reinforcement, and the improved design method of bond strength is proposed.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.437-440
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• 2003

This study has focused on the possibility for recycling of tailings from the Sangdong tungsten mine as powder of self-compacting concrete(SCC). The experimental tests for slump-flow, reaching time to the slump-flow of 500mm, V-funnel and U-box were carried out in accordance with the specified by the Japanese Society of Civil Engineering(JSCE). The result of this study, in case of SCC mixed with tailings, slump-flow was decreased with increasing mixing ratio. But reaching time slump-flow of 500mm, V-funnel and U-box were satisfied a prescribed range. The mechanical properties including compressive strength, splitting tensile strength and static modulus of elasticity were checked with the requirements specified by Korean Industrial Standard(KS). The compressive strength of SCC was decreased with increasing replacement, splitting tensile strength and static modulus were similar to those of normal concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.120-123
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• 2003

In order to evaluate the applicability of steel slag aggregates for tetrapod concrete, the properties of concrete as structural material were investigated. The biochemical research of marine concrete using steel slag aggregates was also carried out. The tested concrete properties are slump, air content, compressive strength, splitting tensile strength, elastic modulus, carbonation, hydration heat, freezing and thawing, sulfate attack, drying shrinkage, etc. The biochemical experiments are carried to research the propagation and reproduction of seaweeds and survival of bottom dwelling species. According to the experimental results, the steel slag aggregate content did not have a significant effect on compressive strength, splitting tensile strength and elastic modulus. The durability of concrete was not influenced by the steel slag aggregate content. From the biochemical research, steel slag aggregate can be evaluated as the material that is ideally suited for promoting propagation and reproduction of seaweeds and survival of bottom dwelling species.