Influence of mechanical and chemical activation on the hydraulic properties of gamma dicalcium silicate

The aim of this work is to clarify the effect of various activation methods on the hydraulic properties of γ-C2S, one of the main phases in stainless steel slags. Synthetic C2S, sintered at 1450 °C for 20 h, consisted of 88 wt.% γ-C2S and 12 wt.% β-C2S. Two activation paths were followed: mechanical activation, by means of high energy milling, and chemical activation, by means of NaOH and Na2CO3 addition. Results indicated that both mechanically and chemically activated γ-C2S hydrated at ambient temperature. XRD analysis showed that the amount of amorphous phase increased during hydration, whereas TGA/DTG data revealed weight loss in the decomposition region of C–S–H. Analyses by FTIR and SEM also support that C–S–H is one of the main hydration products. Mortars prepared with mechanically and chemically activated γ-C2S developed mechanical strength, reaching the values of 9.1 MPa and 10.3 MPa at 90 days, respectively.