Insights into the role of slag fineness on the hydration of slag-sulfoaluminate cement

Slag-sulphoaluminate cement (G center dot SAC), an effective alternative to Portland cement, has garnered significant attention for its low hydration heat, good mechanical properties and durability. However, the role of slag fineness on the hydration of G center dot SAC remains unclear. To address this, the study employed three levels of slag fineness to evaluate its effects on G center dot SAC in terms of hydration heat, hydrates, mechanical properties and pore structure. Results indicate that increasing slag fineness from 400 m(2)/kg to 800 m(2)/kg shortens the induction period by 2 hours but does not significantly alter the hydration heat similar to 110 J/g or 3-day strength (around 30 MPa). In contrast, slag with a specific surface area of 1300 m(2)/kg significantly enhances the hydration of G center dot SAC, evidenced by an increased hydration heat of 180 J/g and a higher degree of slag hydration from 24 % to 79 %. This leads to greater formation of hydrates and a higher polymerization degree of C-S-H, which in turn improves pore structure density and early strength, reaching 38.8 MPa at 3 days. To sum up, a slag fineness similar to 400 m(2)/kg is optimal for engineering applications, offering a balance between performance and economic considerations.