Mechanical behavior of reinforced recycled aggregate concrete short columns under axial compression after high temperature

The mechanical behavior of recycled aggregate concrete axial compression short columns after high temperature was investigated. Five parameters including recycled coarse aggregate replacement ratio, high temperature, the highest temperature duration, concrete strength and stirrup spacing were taken into consideration. Based on the static load tests of 32 specimens after high temperature and 8 contrastive specimens at ambient temperature, the failure mode was observed and the ultimate bearing capacity, rigidity, ductility and energy dissipation were obtained. Furthermore, the effects of different parameters on mechanical performance index mentioned above were analyzed. A calculation means was provided which can be used to calculate the ultimate bearing capacity of recycled aggregate concrete axial compression short columns after high temperature. The results indicate that after increasing the temperature, concrete surfaces change from cinereous to grey, and the quality ignition loss rate increases gradually. It is shown that the ultimate bearing capacity and the initial rigidity decrease with an increased temperature. With an increased replacement ratio, the bearing capacity and the initial rigidity vary slightly. It also indicates that the bearing capacity and the initial rigidity increase with higher concrete strength. However, difference of the highest temperature durations have little influence on behaviors of specimens as well as stirrup spacing.