Stabilization of converter steel slag through ferronickel-slag-Induced f-CaO mineralization: calcination temperature and added dosage optimization

Free calcium oxide (f-CaO) in steel slag causes poor volume stability, being one of the key bottlenecks limiting its large-scale application. To reduce f-CaO formation, this study employs ferronickel slag (FNS) to synergistically modify steel slag, systematically investigating the effects of FNS dosage and calcination temperature on phase evolution, microstructure, and f-CaO content. The results indicate that FNS modification significantly promotes the mineralization of f-CaO in steel slag. As the mass ratio increases, CaO in steel slag reacts with SiO₂ and MgO in FNS to form magnesium orthoclase (Ca₂MgSi₂O₇), a stable coordination mineral phase, resulting in a decrease in CaO content. The f-CaO content generally drops with increased calcination temperature. At a calcination temperature of 1200°C and a 1.5 mass ratio, the f-CaO content drops to 0.39%, effectively improving the volume stability of steel slag and promoting its resource utilization.