Evaluation of the damage process of recycled aggregate concrete under sulfate attack and wetting-drying cycles

The evaluation of the damage process of recycled aggregate concrete made with different recycled coarse aggregate (RCA) replacements (30%, 50%, 70% and 100%) exposed to sodium sulfate solution (50 g/l) under wetting-drying cycles is investigated in this paper. Fly ash and granulated blast-furnace slag modified recycled aggregate concrete were examined by comparison with plain recycled aggregate concrete. Mass change, relative dynamic modulus of elasticity and water-soluble SO42− contents of the specimens were measured. XRD, ESEM and XCT were used to investigate the changing of corrosion products and microstructure of interior concrete. The results indicate that the incorporation of RCA shows an obvious impact on the resistance of concrete against sulfate attack under wetting-drying cycles. Additionally, the FA and GBFS modified recycled aggregate concretes exhibit better resistance than plain recycled aggregate concrete. The analysis of corrosion products from XRD and microstructure from XCT and ESEM is in accordance with the results of water-soluble SO42− contents, mass change and Erd.