Strength Activity Index of Air Quenched Basic Oxygen Furnace Steel Slag

Air quenched basic oxygen furnace steel slag (BOF-SS) is processed at very high cooling rate, which is expected to have different cementitious properties from conventional slowly cooled BOF-SS. For this purpose, the strength activity indexes of air quenched and slowly cooled BOF-SS are investigated. The results reveal that, under the specific surface area (S) of 490 m2/kg, the compressive strength activity index reaches 1. 24 after 28 days with replacement of 15% air quenched BOF-SS and reaches 1.05 after 28 days with replacement of 20% air quenched BOF-SS and 30% granulated blast furnace slag (GBFS). The cementitious activity of air quenched BOF-SS is obviously higher than that of slowly cooled BOF-SS, mainly because it contains more C3S and glassy phases.