Failure mechanism of interface bond behavior between circular steel tube and recycled aggregate concrete by push-out test

In order to reveal the interaction failure mechanism of bond performance at the interface of recycled aggregate concrete filled circular steel tubes (RACFCST), a total of 15 RACFCST short column specimens were designed for push-out test. Three test parameters of replacement rate of recycled coarse aggregate (RCA), concrete strength grade and length to diameter ratio were considered to research their influences on bond behavior of RACFCST. Load-slip curves, distribution laws of bond strain and bond load for RACFCST specimens were obtained. For contrastive computation, practical formulas for bond strength of concrete filled steel tube (CFST) were used to calculate that of the RACFCST. The regression bond strength formula was put forward. The results show that the initial slip at the loading end develops earlier than that at the free end. The longitudinal strains of steel tube in the early and late loading stages respectively exhibit a negative exponent distribution and linear distribution. Along with the increasing of the ratio of length to diameter, the bond load of RACFCST will be increased to some extent. The development of interfacial bond damage can be advanced with the increasing of RCA replacement rate. At the same time, energy dissipation of bond slip is much better along with the increasing of interface embedded length.