Fully utilizing carbonated recycled aggregates in concrete: Strength, drying shrinkage and carbon emissions analysis

In this study, natural aggregates, recycled aggregates (RAs), and carbonated RAs were combined to prepare concrete. Strength, drying shrinkage, microstructures, and the carbon emissions of concrete prepared with different aggregate combinations were explored and compared. The results show that the compressive strengths of carbonated fully recycled aggregate concrete (CFRAC) increased by 20.9% and the drying shrinkage at 180 days decreased by 23.3% compared with that of concrete with RAs due to the reduction of water absorption of RAs and the additional water. The pore structure of CFRAC was densified and improved by carbonation treat-ment on RAs. Furthermore, the carbon emission analysis showed that CFRAC had 7.1%-13.3% lower carbon emission and 13.4%-18.4% lower CO2 intensity than natural/recycled aggregate concrete due to the shorter transportation distance and the carbon absorption. Generally, CFRAC had improved properties and environ-mental benefits, which shows carbonation treatment is a valuable way to promote waste concrete recycling.