Influence of carbonated recycled concrete aggregate on properties of cement mortar

• Carbonation treatment increased the physical properties of recycled concrete aggregate (RCA).
• Mortar made with carbonated RCA exhibited better workability than the uncarbonated RCA mortar.
• Carbonation of RCA improved both original ITZ and newly formed ITZ in the RCA and RCA mortar.

This work investigated the effect of carbon dioxide treatment of recycled concrete aggregate (RCA) on the performance of RCA and RCA mortar. The results indicated that carbonation increased the apparent density, and reduced both water absorption and the crushing value of the RCA. The flowability and compressive strength of the RCA mortar were lower than those of natural sand mortar. However, the properties of mortar made with carbon dioxide treated RCA were very similar to those of natural sand mortar. Compared with the mortar made of un-carbonated RCA, the mortar made with carbonated RCA showed increased autogenous shrinkage, reduced drying shrinkage, water absorption, and chloride migration coefficient. Scanning electron microscope (SEM) examination on the interfacial transition zone (ITZ) in the RCA and RCA mortar found that carbonation treatment of RCA not only improved the original ITZ in the RCA, but also improved the newly formed ITZ in the RCA mortar.