Behavior of steel tube columns filled with steel-fiber-reinforced self-stressing recycled aggregate concrete under axial compression

Faced with the large annual output of construction and demolition waste, cyclic utilization of recycled coarse aggregate (RCA) is inevitable. This study uses steel-fiber-reinforced recycled aggregate concrete (RAC) in the manufacture of concrete-filled steel tube columns, to improve the utilization of RAC. A comprehensive study of the axial behavior of 54 steel-fiber-reinforced self-stressing recycled aggregate concrete-filled steel tube (SSRCFST) columns was conducted. The variables in the experiments included the steel fiber content, self-stress, quality replacement rate of RCA, concrete strength grade, and steel tube thickness. The experimental results show that a poor concrete strength is obtained with increasing RCA content. However, under tri-axial stress in the steel tube, the negative influence of RCA is weakened. An enhancement of the ductility of SSRCFST columns can be achieved by adding a moderate amount of steel fiber. Self-stress can significantly improve the ultimate capacity and stiffness of SSRCFST columns. Moreover, design equations for the ultimate capacity of SSRCFST columns are proposed, and the predictions agree satisfactorily with the experimental results.