• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.905-908
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• 2006

In this study examines physical and mechanical properties the use of domestic low grade meta-kaolin in light weight porous concrete. For this purpose light weight porous concrete incorporating low grade meta-kaolin admixture, was tested for tensile strength and acoustic characteristics. Checking tensile strength of cement and low grade meta-kaolin mixture was used to determine the optimum mix proportion of the low grade meta-kaolin admixture. In this paper sound absorbing material has been investigated by using the light weight porous concrete.

• Journal of Industrial Technology
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• v.27 no.A
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• pp.31-38
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• 2007

Recently produced concrete has a tendency to overcome environmental defects. Porous and planting Eco-concrete requires the neutralization process and enough void in concrete to contain water, to pass air freely, and provides necessary nutrients to vegetation roots. The biological environment in concrete is not suitable for planting because the concrete possesses strong alkali constituent of pH 11-13. This study evaluated the strength and serviceability of concrete as well as the chemical characteristics of concrete mixed by low-grade iron ore left in the abandoned mine and treated by Ammonium monohydrogen phosphate, $(NH_4)_2HPO_4$. Test variables include two kinds of coarse aggregates such as crushed stones and low-grade iron ore, the duration time and the period for neutralization treatment by Ammonium monohydrogen phosphate, $(NH_4)_2HPO_4$, and the proportion ratio of cement, blast furnace slag and silica fume.

• Steel and Composite Structures
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• v.14 no.3
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• pp.229-242
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• 2013

Corrosion is important reason for the deterioration of the bond between reinforcing steel and the surrounding concrete. Corrosion of the steel mainly depends on its microstructure. Smooth S220, ribbed S420 and S500 grade reinforcing steels were used in the experiments. Samples were subjected to accelerated corrosion. Pullout tests were carried out to evaluate the effects of corrosion on bond strength of the specimens. S500 grade steel which has tempered martensite microstructure showed lower corrosion rate in concrete than S220 and S420 steels which have ferrite+perlite microstructure. S500 grade steel showed highest bond strength among the other steel grades in concrete. Bond strength between reinforcing steel and concrete increased with increase in the strength of steel and concrete. It also depends on whether reinforcing bar is ribbed or not.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.83-84
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• 2020

The purpose of this study is to achieve a sufficient fluidity without segregation for normal compressive strength grade concrete mixture. The major obstacle of achieving fluidity of normal compressive strength grade concrete mixture is segregation. Therefore, in this research, the proper use of VMA was suggested to prevent segregation.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.56-57
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• 2020

The purpose of this study is to achieve a sufficient fluidity without segregation for normal compressive strength grade concrete mixture. The major obstacle of achieving fluidity of normal compressive strength grade concrete mixture is segregation. Hence, in this research, VMA was used to prevent segregation.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.449-452
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• 2006

This study inhence the strength of concrete by using domestic low grade kaolin. In conclusion, we confirmed to inhence the strength of concrete when added the low grade kaolin(heated in $800^{\circ}C$) about 10%.

• Smart Structures and Systems
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• v.26 no.2
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• pp.147-156
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• 2020

This numerical study demonstrates the porosity conditions and the intensity of the interactions with the aggressive agents. It is established that the density as well as the elastic modulus are correlated to ultrasonic velocity The following investigation assessed the effects of cement grade and porosity on tensile strength, flexural and compressive of Ultra High Performance Concrete (UHPC) as a numerical model in PLAXIS 2d Software. Initially, the existing strength-porosity equations were investigated. Furthermore, comparisons of the proposed equations with the existing models suggested the high accuracy of the proposed equations in predicting, cement grade concrete strength. The outcome obtained showed a ductile failure when un-corroded reinforced concrete demonstrates several bending-induced cracks transfer to the steel reinforcement. Moreover, the outcome also showed a brittle failure when wider but fewer transverse cracks occurred under bending loads. Sustained loading as well as initial pre-cracked condition during the corrosion development have shown to have significant impact on the corrosion behavior of concrete properties. Moreover, greater porosity was generally associated with lower compressive, flexural, and tensile strength. Higher cement grade, on the other hand, resulted in lower reduction in concrete strength. This finding highlighted the critical role of cement strength grade in determining the mechanical properties of concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.75-76
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• 2019

The purpose of this study is to achieving a sufficient fluidity without segregation for normal strength grade concrete mixture. therefore in this research, by analyzing the various superplasticizer dosages on the concrete mixture, the segregation range was analyzed to provide a proper concrete mix design with sufficient fluidity.

• International Journal of Concrete Structures and Materials
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• v.6 no.2
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• pp.79-85
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• 2012

This paper presents the differences in growth of time-dependent strain values in reinforced cement concrete (RCC) and pre-stressed concrete (PSC) flexural members through experiment. It was observed that at any particular age, the time-dependent strain values were less in RCC beams than in PSC beams of identical size and grade of concrete. Variables considered in the study were percentage area of reinforcement, span of members for RCC beams and eccentricity of applied pre-stress force for PSC beams. In RCC beams the time-dependent strain values increases with reduction in percentage area of reinforcement and in PSC beams eccentricity directly influences the growth of time-dependent strain. With increase in age, a non-uniform strain develops across the depth of beams which influence the growth of concave curvature in RCC beams and convex curvature in PSC beams. The experimentally obtained strain values were compared with predicted strain values of similar size and grade of plane concrete (PC) beam using ACI 318 Model Code and found more than RCC beams but less than PSC beams.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.207-208
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• 2012

This study is aimed to utilize for basic material of concrete quality management through evaluate properties of fresh and hardened concrete with the aggregate quality. As a result, fine aggregate's slump change of between one grade was 8~82% and in case of coarse aggregate, slump change of between one grade was 2~22% on same mixing condition. The unit water for same workability condition, unit water was increased 16kg/㎥ with decreasing of one grade for fine aggregate and unit water was increased 5kg/㎥ with decreasing of one grade for coarse aggregate.