Flexural behavior of steel fiber reinforced self-stressing recycled aggregate concrete-filled steel tube

Abstract Recycled aggregate concrete (RAC) has the potential to escape the predicament of our cities being surrounded by construction waste, while its application is limited due to the defective mechanical properties. This paper aims to improve the performance behavior of RAC, thereby extending its engineering application. A new-style green RAC is prepared by recycled aggregate, steel fiber and sulphoaluminate cement, as infilling into steel tube to manufacture CFST columns. A comprehensive study for 41 concrete mixes and 54 CFST columns subjected to bending is presented. The parameters are steel fiber volume content, recycled aggregate dosage, water cement ratio, cement type and steel tube thickness. The test result reveals that, through reasonable mix design, steel fiber reinforced self-stressing recycled aggregate concrete-filled steel tube can exhibit similar flexural behavior with the normal CFST. Steel fibers prolong the elastic extent and improve the flexural capacity, meanwhile 1.2% of steel fiber is recommended for the optimal improvement. Self-stress induced by the expansive sulphoaluminate cement contributes to the elastic stage, and is beneficial to flexural capacity and stiffness.