Freeze-thaw resistance of recycled aggregate concrete damaged by simulated acid rain

Abstract

Acid rain severely decreases the durability of ordinary concrete structures; however, the effect of acid rain on recycled aggregate concrete (RAC) remains unclear. To fill this gap, this study investigated the freeze-thaw resistance of RAC in response to simulated acid rain spraying. The effects of replacement ratios of recycled coarse aggregate (20%, 35%, and 50% by mass), acidity of simulated solutions (pH of 2.5 and 3.5), erosion time (0, 20 d, and 40 d), and the number of freeze-thaw cycles on the apparent state, quality loss, and relative dynamic elastic modulus (RDEM) of RAC were evaluated. The results demonstrate that the freeze-thaw resistance of RAC with different replacement ratios is unsatisfactory in comparison to ordinary concrete. Acid rain attack has no obvious effect on the mass loss rate of RAC, but it significantly influences the RDEM. The RDEM results indicate that acid rain attack weakens the capacity of RAC to resist freezing and thawing. Moreover, the freeze-thaw resistance of RAC decreases strongly with prolonged acid rain spraying time or with increased acidity of acid rain. These test results indicate several theoretical suggestions and potential implications for government and industry to increase energy conservation, pollution reduction, and recycling of resources.