Carbonation behavior of recycled concrete with CO2-curing recycled aggregate under various environments

A CO2-curing treatment is frequently used to modify the properties of recycled aggregate (RA); however, the carbonation behavior of concrete with CO2-curing recycled aggregate (CRA) has not been investigated in previous investigations. This research focuses on investigating the carbonation behavior of concrete containing CRA when exposed to various environments. The results show that the CO2-curing treatment improves RA property, and there is an obvious reduction in water absorption of CRA. The CRA concrete has higher compressive strength and a lower carbonation depth than RA concrete; in addition, the decrease in the carbonation depth is more obvious when the CO2-curing recycled fine and coarse aggregates are added; for example, the maximum carbonation depth of CRA concrete is approximately 42.5 % lower than that of RA concrete. The carbonation depth increases linearly with the square root of carbonation time. When subjected to the freeze-thaw conditions, incorporating CRA improves the freezing-thawing resistance of concrete, and CRA concrete has better carbonation resistance than RA concrete after undergoing the same number of freeze-thaw cycles. An induced initial crack deteriorates the carbonation resistance of CRA concrete, but CRA concrete still has better carbonation resistance than RA concrete when the induced initial crack and carbonation duration are the same.