Valorization of low-quality recycled concrete aggregates in cement-based systems through carbonation: assessment of engineering performance

Abstract With the continuous rise in construction and demolition waste (CDW) generation and the increasing demand for sustainable construction materials, this study aims to explore the potential of utilizing recycled concrete aggregate (RCA)—the most abundant component of CDW—as a replacement for natural aggregate (NA). Mortar samples incorporating untreated recycled fine aggregate (RFA), natural fine aggregate (NFA), and carbonated RFA (CRFA) were produced to determine whether the mechanical and durability drawbacks of RFA can be mitigated through accelerated carbonation. In this context, the workability, mechanical strength, water absorption capacity, capillary water absorption behavior, freeze–thaw and chloride permeability properties of the mortars were analyzed. The results indicate that the negative impact of RFA on engineering properties can be significantly reduced through accelerated carbonation. Despite all aggregates being in a saturated surface dry state, RFA exhibited the lowest flowability, while NFA had the highest. In strength tests, CRFA-containing mortars achieved performance levels comparable to those with NA. However, RFA mixtures demonstrated considerably higher water absorption and permeability than NA, while CRFA improved these properties. Additionally, RFA mortars experienced greater weight loss during freeze–thaw cycles, but carbonation treatment helped mitigate this deterioration. These findings highlight the potential of accelerated carbonation treatment as an effective method for upgrading RCAs, contributing to more sustainable construction practices.