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

The formation behaviors of tricalcium silicate (C 3 S) in modified EAF slag were investigated to assess the feasibility of using EAF slag for cement clinker production. For the formation conditions of C 3 S, the C 3 S 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 C 3 S 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) + SiO 2 (l) = 3CaO·SiO 2 (s), controlled by the diffusion of SiO 4 4− in liquid phase. Conversely, in the dicalcium silicate (C 2 S) rich region, C 3 S formation primarily occurs via the indirect formation: 2CaO·SiO 2 (s) + CaO(l) = 3CaO·SiO 2 (s), with the reaction being controlled by the diffusion of Ca 2+ in the liquid slag. • Cement clinker production from modified EAF slags via Cambridge Electric Cement method • Tricalcium silicate (C 3 S) formation conditions and formation mechanisms • Increasing slag basicity and holding time are more conducive to the C 3 S formation than temperature. • Direct formation of C 3 S in lime rich region while indirectly formation in C 2 S rich region