Effects of Quicklime and Iron Tailings as Modifier on Composition and Properties of Steel Slag

Abstract

Steel slag had lower activity and much lower hydration rate than cement. Quicklime and iron tailings were designed as modification agent to adjust the composition and properties of high temperature steel slag. The results show that quicklime as modifier can greatly increase the content of cementitious minerals in modified steel slag and also promote the decomposition of RO phases and transformation of MgO in RO phase to f-MgO. After high temperature modification with compound modifier of quicklime and iron tailings, steel slag shows the main mineral phases of C3S, C2F and MgFe2O4. The activity index of modified steel slag at 28 days reaches 95.5% when the steel slag is modified by 15% of the compound modifier with the ratio of quicklime to iron tailings equal to 2:1 at 1350 °C. Moreover, the sample with the modified steel slag exhibits the dense structure of hydration paste and the main hydration products of C-S-H gels and Ca(OH)2 crystals.