Gypsum has been frequently used as a setting agent in Portland cement–calcium sulfoaluminate cement composite cement, and its main target is the aluminate minerals [tricalcium aluminate–ye’elimite (C3A–C4A3 \(\overline{\text{S}}\) )]. However, the impact of gypsum dissolution characteristics on hydration of aluminate minerals is not so clear. This paper systematically investigated effects of hemihydrate, dihydrate and anhydrite gypsum on the hydration process of C3A–C4A3 \(\overline{\text{S}}\) composite system. The results exhibited that addition of gypsum shortened hydration induction period for the system, with hemihydrate gypsum having the greatest effect on induction period, followed by dihydrate gypsum and anhydrite gypsum having the least. Gypsum dissolution characteristics also affect the formation of AFt. At 1 d, the system with hemihydrate gypsum produces the highest amount of AFt, about 62.14% of the total sample, followed by the system with dihydrate gypsum (60.40%), and the system with anhydrite gypsum yields the lowest (49.42%). The kinetic parameters for each stage of a hydration reaction were also calculated according to the Krstulovic-Dabic and Kondo models. For systems incorporating hemihydrate or dihydrate gypsum, hydration is driven by phase boundary-diffusion reaction, whereas for systems with anhydrite gypsum, hydration is governed by phase boundary-diffusion-autocatalytic-diffusion reaction. These differences are primarily attributed to the dissolution rates of the gypsum types and their influence on the nucleation and growth processes of AFt.
