Hydration activity and expansibility of different RO phase composition in steel slag

Steel slag (SS) accounts for 15%∼20% of steelmaking output, its application in cement concrete was limited since the poor stability. In this study, the divalent metal oxide solid solution (RO phase) in SS was analog synthesized to study its hydration activity and expansibility. The results showed that the hydration activity and expansibility of MgO in analog-RO phase is affected by the content of FeO, with the increase of molar ratio (x) of FeO to MgO in analog-RO phase the autoclave expansion rate and hydration activity of the cement paste decreased. When x≤0.5, the RO phase had high hydration activity and could cause the poor soundness of SS. When x=1, the RO phase had low hydration activity and could cause the slight expansion of SS. When x≥2, the RO phase had no hydration activity and could not cause the expansion of SS. The control of different analog-RO phase composition induced different hydration and expansibility, which provided a theoretical basis for the influence of RO phase on the soundness of steel slag and putting forward measures to reduce the expansion of SS, promoting the high-volume utilization of SS in cement and concrete.