Hydration kinetics of composite binder containing slag at different temperatures

Hydration heat evolution rate and cumulative hydration heat of cement-slag blends were measured at 298, 318 and 333 K by isothermal calorimeter. Based on hydration kinetics model, three hydration processes of composite binder, namely nucleation and crystal growth (NG), interactions at phase boundaries (I) and diffusion (D), were characterized, and the relationship between hydration rate and hydration degree of binder was discussed in individual periods. The kinetics exponent, n, rate constant, K, and apparent activation energy, Ea, of hydration were calculated and analyzed. Results indicated that the kinetics model could simulate the hydration process of composite binder containing no more than 70 % of slag, whose process sequence is NG -> I -> D at 298 and 318 K, but it becomes NG -> D at 333 K. Composite binder containing 90 % of slag cannot use this model due to the variation in mechanism. The simulation error has a certain increase as increasing temperature and slag content. E-a increases with an increase in slag content.