Effect of particle size distribution on the pre-hydration, hydration kinetics, and mechanical properties of calcium sulfoaluminate cement

The particle size distribution (PSD) has a significant influence on the fresh and final properties of cement and its derived products. In this paper, CSA cements with three different mean diameters (D50), ranging from 6.04 to 26.62 & mu;m were prepared by milling. The pre-hydration behavior was quantitatively analyzed, including the degree of pre-hydration, the dynamic change of mineral assemblage and the morphology of the prepared CSA cement exposed to 57%, 75% and 97% relative humidities (RHs) for up to 90 days. Hydration kinetics, porosity, and compressive strength of the cement paste made with fresh and pre-hydrated CSA cement with different PSD were also characterized. The results show that pre-hydration of CSA cement at RH higher than 75% has detrimental effects on the hydraulic activity and strength gain of CSA cement. However, coarser CSA cement (D50 = 26.62 & mu;m) does not only show better resistance to pre-hydration, but also higher compressive strength and lower porosity.