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재생골재를 사용한 콘크리트의 초기재령 수축에 관한 연구
구봉근 ( Koo Bong-kuen ),서상구 ( Seo Sang-gu ),라재웅 ( Rha Jae-woong ),박재성 ( Park Jae-seong ) 한국구조물진단유지관리공학회 2003 한국구조물진단유지관리공학회 논문집 Vol.7 No.2
Cracks in reinforced concrete structures reduce overall durability by allowing the penetration of water and aggressive agents, thereby accelerating the deterioration of the reinforcing steel. Highway pavement and bridge decks are especially susceptible to this type of deterioration since these structures exhibit high rates of shrinkage and are frequently exposed to aggressive environmental conditions. The objectives of this investigation included the development of experimental procedures for assessing shrinkage cracking potential of recycled aggregate concrete, the evaluation of mix composition on shrinkage cracking potential, and the development of theoretical models to simulate early-age cracking behavior. Specifically, the influences of shrinkage-reducing admixture(SRA) and recycled aggregate concrete were investigated. The shrinkage-reducing admixture substantially reduces free shrinkage and restrains shrinkage cracking while providing similar mechanical properties. A fracture mechanics modeling approach was developed to predict the behavior of a variety of restrained concrete specimens. This modeling approach was used to successfully explain experimental results from a variety of mixture compositions. The model was used to demonstrate the influence of material and structural properties on the potential for cracking.
구봉근,라재웅,이재범,류연종,이현석 충북대학교 건설기술연구소 2003 建設技術論文集 Vol.22 No.2
As concrete is prevented from shrinking freely, tensile stresses develop which frequently result in cracking. Cracks in reinforced concrete structures reduce overall durability by allowing the penetration of water and aggressive agents, thereby accelerating the deterioration of the reinforcing steel. Highway pavement, bridge decks, and industrial floors are especially susceptible to this type of deterioration since these structures exhibit high rates of shrinkage and are frequently exposed to aggressive environmental conditions. The objectives of this investigation included the implement of experimental procedures for assessing shrinkage cracking behavior on recycled aggregate concrete, the selection of replacement rate and mix composition on recycled aggregate concrete. Specifically, the influence of a shrinkage reducing admixture(SRA) and recycled aggregate concrete was investigated. The shrinkage reducing admixture substantially reduces free, shrinkage and restrained shrinkage cracking while providing similar mechanical properties. Restrained shrinkage experiments were developed and shrinkage cracking was shown to be size dependent and recycled aggregate replacement rate. A mechanical properties experiment approach was developed to predict the behavior of a variety of recycled aggregate concrete specimens. This experimentally approach was used to successfully explain experimental results from a variety of mixture compositions and recycled aggregate concrete. This experiment was used to demonstrate the influence of material and structural properties on the potential for cracking.
김영의,김태봉,구봉근,라재웅 충북대학교 건설기술연구소 1994 建設技術論文集 Vol.13 No.1
The fatigue tests were performed on the high strength concrete beams with single edged notch which was reinforced steel fiber. The steel fibers were used 1.0 percent by volume fraction and the lengths of the steel fiber were 30㎜ and 60㎜. These were tested consists of constant amplitude tests for different levels of loading. The test program included endurance limit with repect to flexural fatigue and relation of load-CMOD(crack mouth opening displacement). The results of test, it was found from S-N curve that the fatigue strength for a life of 2 million cycles of load was approximately 70 percent with respect to the static ultimate strength. And the static strength of SFRC after fatigue test was increased average 27% than the static strength that had been not fatigue loading. It is because strain hardening of steel fiber.