Abstract: On the basis of statistical data of interfacial bonding test between steel bar and recycled concrete under freezing-thawing environment, we built a model of bonding degradation in line with the gemetric damage theory. By fitting the bond strength-slip curve using exponential function, we established a bond-slip damage constitutive relation between steel bar and recycled concrete in freezing-thawing environment. Moreover, we analyzed the interfacial bonding energy consumption by defining the bonding energy factor to quantify the changes of interfacial bonding performance under different freeze-thaw cycles. Results revealed that the bonding energy of specimen with zero recycled aggregate was close to that with 100% of recycled aggregate, both larger than those with 30% and 60% of recycled aggregate. Given the same replacement ratio of recycled aggregate, the bonding energy factor declined with the proceeding of freezing-thawing cycles, indicating evident reduction of energy consumption ability; at the same cycle, the bonding energy factor first increased while then dropped with the augment of recycled aggregate ratio; when the replacement ratio of recycled aggregate was 30%, the energy consumption ability reached the optimum. The research findings revealed the failure mechanism and influencing factors for the interface between steel bar and recycled concrete in freeze-thaw environment, helped improving the basic theoretical system of recycled concrete, and offered reference for the application of recycled concrete in practical engineering.

Key words: recycled concrete, freezing-thawing environment, constitutive relation, degradation of bonding, interface damage