Revealing the tricalcium silicate formation behaviors in modified EAF slag at high temperatures for the production of electric recycled cement

Abstract

The formation behaviors of tricalcium silicate (C₃S) in modified EAF slag were investigated to assess the feasibility of using EAF slag for cement clinker production. For the formation conditions of C₃S, the C₃S content in slag exhibits a notable increase with elevating slag basicity and reaction time, while only a slight enhancement with temperature rising from 1400 °C to 1500 °C. The C₃S formation mechanism depends on the local conditions in the slag. In the lime-rich region it primarily takes place through the direct formation, i.e. 3CaO(s) + SiO₂(l) = 3CaO·SiO₂(s), controlled by the diffusion of SiO₄⁴⁻ in liquid phase. Conversely, in the dicalcium silicate (C₂S) rich region, C₃S formation primarily occurs via the indirect formation: 2CaO·SiO₂(s) + CaO(l) = 3CaO·SiO₂(s), with the reaction being controlled by the diffusion of Ca²⁺ in the liquid slag.