Hydration Mechanism of Portland and Calcium Sulphoaluminate Cementitious Material

This paper discusses the hydration process of Portland cement (PC) and Calcium Sulphoaluminate cement (CSA) composite material at the early age. The setting time and mortar strength were tested, the hydration process was analyzed by isothermal calorimetry tests, and the hydration products were characterized by XRD, SEM analysis. The results show that: CSA can significantly improve the hydration rate of ultra-early age (2 h and 6 h) and improve the mechanical properties. But there are still interactions between the hydration of PC and CSA, including that the gypsum in CSA will inhibit the hydration of C₃A in PC and the CH generated by PC will promote the rehydration of AH₃. The inhibiting or promoting effect of CSA on hydration process changes with its content. The design method of PC-CSA composite material was proposed, and the reasonable mixing amount of PC or CSA was also suggested.