Property Enhancement of Recycled Coarse Aggregate and Its Concrete under CO₂-Accelerated Curing Treatment

The poor properties of recycled coarse aggregate (RCA) and recycled coarse aggregate concrete (RCAC) are considered key constraints hindering the reuse of this waste resource in marine engineering. The CO₂-based accelerated carbonation method, which utilizes the alkali aggregate properties of RCA to achieve CO₂ uptake and sequestration while significantly enhancing its properties, has attracted widespread attention. However, the degree of improvement in the properties of RCA under different initial moisture conditions (IMCs) and aggregate particle sizes (APSs) after CO₂-accelerated carbonation remains unclear. Moreover, the quantitative effect of carbonated recycled coarse aggregate (CRCA), which is obtained from RCA samples with the optimal initial moisture conditions, on the improvement of RCAC under optimal accelerated carbonation modification conditions still needs to be studied in depth. For this investigation, a CO₂-accelerated carbonation experiment was carried out on RCA samples with different IMCs and APSs, and the variations in the properties of RCA with respect to its IMC and APS were assessed. The degree of accelerated carbonation modification of RCA under different IMCs and APSs was quantified, and the optimal initial moisture conditions for enhancing the properties of the RCA were confirmed. By preparing concrete specimens based on the natural coarse aggregate, RCA, and CRCA with the best initial moisture conditions (considering the same concrete-water proportion), the effect of CRCA on the workability, mechanical properties, and durability of the corresponding concrete specimen was determined. The findings of this study can be used to effectively promote the sustainable development of marine science and engineering in the future and contribute to global dual-carbon goals, which are of great practical significance and scientific value.