Surface Reaction of Blast Furnace Slag under Hydrothermal Conditions

Hydrothermal treatment has various possibilities for adding value to blast furnace (BF) slag by forming hydroxide or hydrate crystals and introducing pores into the reaction product. To optimize the hydrothermal reaction process, understanding of the reaction behavior of BF slag during hydrothermal treatment is indispensable. In the present work, the mechanism of the hydrothermal reaction of BF slag was investigated by focusing on the reaction at the slag surface. The surface reaction behavior was reproduced using slag plate samples, which adjusted the effective amount of hot water participating in the reaction. The changes in the surface morphology of BF slag and synthesized CaO–SiO2–Al2O3(–MgO) slags during hydrothermal treatment at 250°C were examined. The reaction mechanism of BF slag as well as the effect of MgO on the reaction were discussed from the observed phenomena.