In-situ wet carbonation of steel slag powder paste made with carbonated water: Interaction mechanism between carbonation and hydration

Abstract

The utilization of steel slag powder is severely limited by its low activity. This study reveals that in-situ wet carbonation with carbonated water can significantly enhance its hydration activity. The influencing mechanism of carbonation on the hydration process and its kinetics during hydration are explored, and on this basis, the interaction between carbonation and hydration is discussed. It is found that both hydration and carbonation exhibit distinct characteristics before and after the acceleration stage. Before the acceleration stage, the hydration rate is affected by mineral dissolution rate, which is dependent on carbonation reaction, with carbonation rate determined by the CO2 concentration. After entering the acceleration stage, the hydration rate is promoted by the increased nucleation effect (e.g., nano-CaCO3 precipitation). The hydration in this period dominates carbonation by controlling mineral dissolution rate, with carbonation rate dependent on the mineral dissolution rate. As a result, mineral dissolution is shown to act as a bridge between hydration and carbonation interactions. Based on these results, the lack of further increase in hydration activity of steel slag powder with higher concentrations of carbonated water is also explained. This study provides a deep understanding for wet carbonation in steel slag powder paste.