Characteristics of Calcium Trisulphoaluminate Hydrates for Rapid Hardening of Cement Composites

摘要

The hydration reaction temperature and the hydrated product were studied using three types of calcium aluminate clinker minerals (CA, C_3A, CSA) and employing hydration temperatures of 20℃ and 5℃. The main hydration product of these rapid hardening clinkers is a highly sulphated form of calcium trisulphoaluminate hydrate (ettringite) whose characteristics are largely affected by the curing temperature. The microscopic structure of cement hydrate cured at 20℃ showed close-packed long needle-like ettringite crystlal. On the other hand, the ettringite crystal formed at 5℃ was relatively short compared with that cured at 20℃. The change of crystal form of ettingite at low temperature is presumably due to the decrease of Al~(3+) solubility and the increase of SO_4~(2-) solubility.