Hydration reactivity of calcium-aluminate-based ladle furnace slag powder according to various cooling conditions

Abstract Ladle furnace slag (LFS) is a reduction slag discharged from a secondary metallurgical process, and its cooling methods in the discharging process are classified into a rapid or slow method. While the former is only an hour consuming process by water quenching or air spraying which is needed heavy equipment, the latter is several days consuming process by self-cooling of slag containing intermittent water spraying without special equipment. The objective of this study is to investigate the binder characteristics of slowly cooled LFS, which is experimentally evaluated in the two viewpoints. The one is the material level evaluation focused on the mineralogical properties such as mineral composition and vitrification ratio, the other is the mixtures level evaluation focused on the hydration properties of LFS powder such as setting time and strength development. From this experiments, the calcium–aluminate-based LFS powder, though it is slowly cooled, shows a high content of reactive mineral of C12A7 and low vitrification of 19% in the material stage. Also, if it does not make contact with water during cooling, its mortar mixture shows a very short setting time of 8 min and high compressive strength of 15  MPa at 3 h age and over 30  MPa at 28 day age. Therefore, this study suggests that the calcium–aluminate-based LFS powder is a very good cementitious material, having comparatively high activity at early age.