Global CO2 sequestration potential of recycled aggregates: Modeling, life cycle analysis, and accelerated carbonation strategies.

Recycled aggregates (RAs) carbonation shows great potential for CO2 reduction. This study developed a CO2 sequestration model for RAs based on the conservation of carbonated elements, considering the service-life, production, and storage stages of RAs. Moreover, the uncertainty analysis was conducted on the predicted CO2 sequestration. The results indicate that the annual CO2 sequestration in the service-life stage rises rapidly before 2048, then slows with a gradual and fluctuating increase. The mean value of carbon emissions of RAs' production with one-time crushing method is 2.5 kg CO2 /t RAs, of which 60-90 % comes from crushing. In the storage stage, CO2 sequestration demonstrates a skewed distribution under the pile packing mode, while the tile packing and accelerated carbonation modes follow a normal distribution. The pile packing mode assumes limited air penetration, which remains to be experimentally verified. Total CO2 sequestration under the three packing modes from 2020 to 2060 are 12.4 GtC, 26.4 GtC, and 26.8 GtC, respectively. The proposed framework contributes to achieving carbon-neutral construction strategies.