Abstract: To study the failure characteristics of recycled coarse aggregate concrete under uniaxial compression, the strain change law of concrete cube in the failure process was recorded by digital image correlation technology, and the width and porosity of interfacial transition zones were characterized by microhardness test and backscattered electron imaging. The experimental results show that the compressive strength of recycled concrete increases by 17.86% and 35.55% compared with untreated samples after aggregate reinforcement and mortar reinforcement, respectively. It indicates that mortar reinforcement is more helpful for improving the compressive strength of recycled concrete. The microhardness of the old mortar increases, and the porosity of the interface transition zone between old aggregate and old mortar is reduced by aggregate reinforcement. The microhardness of new mortar increases, and the porosity of the interface transition zone between old aggregate and new mortar and between old mortar and new mortar is reduced by mortar reinforcement. The probability of passing penetrating cracks decreases for reinforcement interfaces.

Key words: recycled coarse aggregate concrete, failure mechanism, interfacial transition zone, aggregate reinforcement, mortar reinforcement, microhardness, porosity