Accelerated carbonation of steel slag for enhanced carbon capture and utilization as aggregate in alkali-activated materials

Accelerated carbonation of Ca- and Mg-rich solid wastes is a transformative method to control CO2 emissions and eliminate waste and by-products, such as basic oxygen furnace slag (BOFS). This technology is considered a feasible method to limit volumetric instability and bring economic and environmental value to BOFS aggregates. This study evaluated the effect of pre-treatment carbonation conditions (temperature, moisture conditions and CO2 pressure) of BOFS subsequently used as aggregates for alkali-activated mortars. The mechanical, physical and microstructural properties of alkali-activated mortars containing 100 % BOFS aggregates carbonated from different conditions were assessed. The results showed that the carbonation process of BOFS aggregates is mainly influenced by its moist conditions, followed by the CO2 pressure. In general, carbonated BOFS aggregates present after the pre-treatment a rougher surface characterized by a higher specific surface area, which improves the bonding between the matrix and aggregate, with consequent improvements in the mechanical properties of the alkali-activated mortars.