Early Hydration of Calcium Sulfoaluminate Cement at Elevated Temperatures

Temperature plays a significant role in determining the hydration behavior of calcium sulfoaluminate (CSA) cement, which is a sustainable alternative to Portland cement. This study investigates the effects of high temperatures (20–90 °C) on the early hydration of CSA cement within the first 6 h. Results indicate that high temperatures accelerate the hydration reaction and alter the hydration product composition by affecting the properties and solubility of hydration products. With identical ye'elimite hydration degree, AH3 quantity rises with temperature increases while AFt decreases. AFm's content slightly rises below 60 °C but significantly increases at 90 °C as it replaces AFt as the primary hydration product, regardless of the calcium sulfate content. These hydration product changes lead to variations in ion concentrations, with Ca2+ and SO42– following similar patterns and Al3+ levels aligning with pH changes. High temperatures significantly boost CSA cement's early strength, with compressive strength strongly correlating with total released heat across all temperatures. AFt has the most significant impact on the compressive strength of CSA cement, followed by that of AH3 and AFm.