New insights into the effects of different CO2 mineralization conditions on steel slag as supplemental cementitious material

Facing the increasingly severe greenhouse effect, CO2 mineralization for minerals is recognized as one of the most promising carbon capture and storage technologies. The effects of mineralization on pozzolanic activity of steel slag under different CO2 condition were discussed in this research. Strength activity index method, acid-base dissolution method, and hydration heat evolution method were used to assess the pozzolanic activity of mineralized steel slag. This study suggests that following CO2 mineralization, the early-stage activity of steel slag decreases, while laterstage activity increases, which is due to the accelerated hydration of silica-rich phase and nucleation effect of calcite. The stability of the barrier layer on mineralized steel slag surface is the key factor determining the degree of activity enhancement. The strength activity index of atmospheric-pressure mineralized steel slag reaches 95.8 % on 28 d due to the dissolution of the barrier layer during hydration process, with pozzolanic activity being the most improved. However, the pozzolanic activity improvement of high-pressure mineralized steel slag is slightly lower due to the stronger barrier layer, which requires longer dissolving time.