Carbonation of steel slag and gypsum for building materials and associated reaction mechanisms

摘要

The carbonation of steel slag to produce building material is a useful way to increase the utilization of steel slag and absorb carbon dioxide. In this study, gypsum, steel slag, and water were mixed, compaction-shaped, and carbonation-cured as a means of improving the strength of the steel slag. It was observed that gypsum promoted an increase in both the compressive strength and the CO_2 uptake of steel slag. CO_2 uptake was positively correlated with strength. Microanalysis indicated that the main hydration product were C-S-H phases and ettringite, while the main carbonation products were calcite and monocarbonate (C_3A. CaCO_3.11H_2O). Gypsum is speculated to promote the rapid hydration of steel slag to form ettringite (C_3A.3CaSO_4.32H_2O), which then reacts with CO_2 to produce monocarbonate; thus, gypsum plays a catalytic role in this system. The results of this study therefore provide theoretical guidance for the preparation of steel slag-gypsum carbide building materials.