MgO Effect on Hydrothermal Solidification of Blast Furnace Slag

Abstract

Due to the large generation of blast furnace (BF) slag, new recycling processes that produce valuable materials are required. The authors have focused on a hydrothermal treatment of BF slag using waste heat exhausted from iron- and steelmaking processes. Although BF slag contains Al₂O₃, which is well known to have a deteriorating effect on hydrothermal reactions, especially CaO–SiO₂ hydration, it can be successfully solidified by hydrothermal treatment above 523 K. We focused on the contribution of MgO in BF slag to the hydrothermal reactivity in the slag system. The hydrothermal solidification of synthesized CaO–SiO₂–Al₂O₃ and CaO–SiO₂–Al₂O₃–MgO slags were investigated in the present work. The hydrothermal solidification behaviors of slags are discussed based on the degree and type of crystal formation during the hydrothermal process.