Large-Scale Carbonation of Recycled Concrete Aggregates (RCA): Aggregate Properties and Implications to Transportation Geotechnics

Concrete is one of the most widely used construction materials, but recycling it into recycled concrete aggregates (RCA) often results in high porosity, elevated water absorption, and reduced durability. Carbonation treatment offers a dual benefit: improving RCA performance while capturing CO2. This study investigated the effect of carbonation duration on RCA under large-scale conditions using a 500-gal. chamber, with treatment times ranging from 2 to 72 h. Results showed that most improvements in freeze-thaw resistance occurred within the first 24 h, with only marginal gains thereafter. Normalized CO2 consumption was quantified and applied to national-scale estimates of sequestration potential. At a 50% substitution rate of natural aggregate with CO2-treated RCA in US road construction, up to 467,000 t of CO2 could be sequestered annually, alongside cost savings of approximately $267 million. These findings demonstrate the technical and economic feasibility of large-scale RCA carbonation as a strategy to enhance material performance while contributing to carbon reduction in infrastructure development.