Insights into enhancing recycled aggregate pervious concrete via optimised multi-phase collaborative carbonation: mechanical strength and its mechanism

Excessive CO2 emissions bring great challenges to environmental sustainability. This work examined three carbonation treatments: carbonation strengthening of recycled coarse aggregate (RCA), carbonation curing of pervious concrete, and their synergistic effect. Treatment parameters were optimised to investigate strength development and microscale mechanisms. Results show that the optimal parameters are 30 °C, 0.3 MPa, 24 h and 25% initial water content for RCA strengthening, and 40 °C, 0.4 MPa, 10 h and 0.25 water-to-cement ratio for pervious concrete curing. Under optimal conditions, compressive and flexural strengths increased by 20.7% and 15.5%, respectively. Carbonation curing enhances 7d flexural strength but negatively affects 28d performance. Synergistic carbonation reduces the volumes of different harmful pores by 31.4%, 62.9% and 49.5%. The carbon sequestration rates of RCA-strengthened and carbonation-cured pervious concrete reach 8.42% and 9.27%, respectively.