Steel corrosion and corrosion-induced cracking in reinforced concrete with carbonated recycled aggregate

Accelerated carbonation treatment was proposed as an environmentally friendly and promising method to strengthen the old mortar attached to the surface of recycled aggregate (RA), thereby improving the properties of recycled aggregate concrete (RAC). However, the steel corrosion and corrosion-induced cracking in concrete with the carbonated RA (CRAC), as the potential threats to the application in structural concrete, received little consideration in previous studies. In this study, RA was modified by accelerated carbonation treatment and the effects on the physical properties of RA were evaluated. Moreover, the compressive strength, resistance to steel corrosion and resistance to corrosion-induced cracking of RAC and CRAC were experimentally investigated. In addition, the pore structure test of old mortar adhered to RA and the microhardness test of interfacial transition zones (ITZs) in concrete were conducted to reveal the enhancement mechanism of accelerated carbonation treatment. The results show that the carbonated RA exhibits lower water absorption and slightly higher apparent density due to the enhancement of pore structure; CRAC exhibits higher compressive strength, better resistance to steel corrosion and less corrosion-induced cracks, which can be explained by an improvement in the micro -hardness of ITZ between new and old mortar in RAC.