Analytical and experimental investigation of the axial compressive behaviour of recycled brick-concrete aggregate CFST

Abstract

The mixture of recycled concrete aggregate (RCA) and recycled brick aggregate (RBA) is named as recycled brick-concrete aggregate (RBCA). Filling RBCA concrete into steel tubes to form RBCA concrete-filled steel tube (RBCA-CFST) not only enhances the mechanical properties of the RBCA concrete but also addresses the issue of construction waste disposal. This research investigated the axial compressive behaviours of RBCA-CFST through experimental and numerical methods. The experimental variables included RBA replacement ratio, the concrete strength and the thickness and shape of steel tubes. The results demonstrated that the RBA replacement ratio did not affect the failure mode of RBCA-CFSTs. The axial bearing capacity and the peak strain of circular and square specimens exhibited a descending trend with the increase of the RBA replacement ratio. Upon increasing the concrete strength from 30 MPa to 45 MPa, the axial bearing capacity of RBCA-CFSTs increased by 21.0%, while the ductility decreased by 3.4%. Higher steel tube thickness enhanced the axial bearing capacity and deformability. The DBJ 13–51–2010 specification accurately estimated the axial bearing capacity of RBCA-CFSTs while maintaining a conservative safety margin. The simulated load-displacement curves showed good agreement with the experimental results, and a parametric study was also conducted.