Investigation on bond strength between recycled aggregate concrete (RAC) and steel tube in RAC-filled steel tubes

Abstract

This paper reviews the previous studies on bond behaviour of concrete-filled steel tubes (CFST) and recycled aggregate concrete-filled steel tubes (RAC-FST). The bond behaviour between the steel tube and the recycled aggregate concrete (RAC) of RAC-FST is experimentally investigated then. A series of push-out tests on 56 RAC-FST specimens are conducted with parameters of cross-section type, cross-sectional dimension, strength of RAC, replacement rate of recycled coarse aggregate and interface treatment (i.e. oilin, polishing). Mechanism of the effects of chemical adhesion, micro-interlocking and macro-interlocking on the bond strength is discussed and investigated based on the testing results. The analytical results show that the cross-section type and cross-sectional dimension are two main parameters that influence the bond strength between the steel tube and the RAC core. It can be concluded that, in general, the bond behavior of the RAC-FST is similar to that of the steel-concrete surface in concrete-filled steel tubes (CFST). Finally, empirical formulas are proposed for the calculations of the bond strength between the core concrete and the outer steel tubes.