CO2 sequestration and mechanical properties of recycled concrete

This study investigated CO2 sequestration in recycled concrete using baking soda (2 %) and quicklime (5 %) as additives, replacing 50 % of fine aggregate with waste concrete aggregate and 50 % of coarse aggregate with aircooled blast furnace slag. Accelerated carbonation curing was applied under two durations and pressures, with two strategies: post-demolding carbonation and pre-carbonation of aggregates. Results showed that CO2 absorption was significantly influenced by carbonation curing duration and pressure. Under 6 h of carbonation curing and a pressure of 4.08 bar, various types of concrete achieved maximum carbon absorption. Pure concrete specimens exhibited the highest carbonation rate at 6.08 %, followed by specimens with 2 % baking soda at 4.69 %. Considering both carbon absorption efficiency and compressive strength, the optimal mix proportions were determined to be 2 % baking soda, 5 % quicklime, 50 % waste concrete aggregate, and 50 % air-cooled blast furnace slag.