순환 굵은골재의 혼입률에 따른 콘크리트와 이형철근의 부착 거동

In this study, mixed recycled coarse aggregate (RCA) was produced by mixing RCA from waste concrete in order to evaluate a new method of RCA production. Bond strength between reinforcing bars and RCA concrete was qualitatively evaluated as a part of continuous studies to establish design code of reinforced concrete structural members using recycled aggregate. For practical application, specimens were manufactured with the ready mix RCA concrete. Parameters investigated include: concrete compressive strength (i.e 21, 27 and 40 ㎫), replacement levels (i.e 0, 30, 60 and 100%), bar position (i.e vertical and horizontal) and bar location (75 and 225 ㎜). For the pull-out test, each specimen was in the form of a cube, with each side of 150 ㎜ in length and a deformed bar, 16 ㎜ in diameter, was embedded in the center of each specimen. From the test results, the most of HT type specimen with compressive strength of 21 and 27 ㎫ showed lower bond strength than the ones provided in CEB-FIP and considered in reinforcement location factor (α = 1.3). It was reasoned that bonded area of top bar specimen was reduced at the soffit of reinforcement because of bleed water of fresh concrete. Therefore the reinforcement location factor in current KCI design code should be reviewed and modified.