How the Carbonation Treatment of Different Types of Recycled Aggregates Affects the Properties of Concrete

In this research work, two types of recycled aggregates were used: (1) the recycled concrete aggregate, RCA, obtained by crushing the parent concrete produced using limestone cement and (2) the recycled concrete aggregate RCA-FA produced by crushing parent concrete made with FA blended cement. After the carbonation treatment process, the carbonated RCA-C and RCA-FA-C recycled aggregates were produced. The recycled concrete mixtures were prepared using the four types of recycled aggregates (RCA, RCA-FA, RCA-C, and RCA-FA-C) in 50% (by volume) to replace natural coarse aggregates. The physical and mechanical properties and durability (sorptivity, chloride ion penetration, and carbonation resistance) were determined and analysed. The obtained results were also compared with those of conventional concrete (CC). It was concluded that the physical and mechanical properties of recycled concrete improved when RCA-C were employed in concrete production. In contrast, the recycled concrete produced with RCA-FA-C was found to have the worst property values. According to durability properties, the concrete made with RCA-C and RCA-FA aggregates achieved the highest chloride resistance, similar to CC concrete. Nevertheless, the concrete produced with uncarbonated RCA acquired carbonation resistance equivalent to CC concrete.