Effects of crystallinity and silica content on the hydration kinetics of 12CaO · 7Al2O3

The effects of 12CaO7 · Al2O3 crystallinity on the kinetics of hydration reaction were studied by measuring the heat liberated using a conduction calorimeter. The crystallinity of the sample was modified by changing the cooling rate of the sample after synthesis reaction. In addition, the effects of silica addition to 12CaO7 · Al2O3 glass on kinetics were also investigated. The results indicated that the glass underwent a faster initial kinetic hydration reaction compared with that of crystalline calcium aluminate. The addition of silica, on the other hand, decreased the reaction rates. The results are discussed in terms of the solvation rate of the calcium aluminate phases and the precipitation of the hydrate phases.