Maximizing the use of recycled aggregates from combined thermal/mechanical and accelerated carbonation treatment

The global emphasis on using recycled concrete aggregates (RCA) to reduce the depletion of natural resources has grown significantly. However, the presence of adhered mortar limits their usage in concrete to the coarse fraction and at low replacement rates, as complete replacement remains a challenge. This study aims to improve concrete with low-quality recycled aggregates through thermal/mechanical treatment combined with accelerated carbonation. Physical, chemical and mechanical properties of concretes with 100% coarse and fine RCA were evaluated. Results revealed that after the combined treatment the water absorption of coarse and fine RCA decreased by 18% and 6%, respectively. SEM images showed the precipitation of calcite with better crystallinity, resulting in a denser cement matrix, although water absorption and porosity were slightly improved. Furthermore, compressive and flexural strength of treated concrete achieved 91% and 96% of the control series, considering full RCA replacement and a higher w/c ratio. [Display omitted] •The behavior of the combined treatment was analyzed to improve low-quality RCA.•The combined treatment sealed pores and thus densified the cement matrix of the RCA.•A better-quality ITZ was achieved after the treatments applied to the RCA.•The mechanical and physical properties of concretes with treated RCA were improved.