A simplified model of hydration kinetics for portland cement

Abstract:

To more clearly elaborate the influence of water-cement ratio (w／c) on hydrate process of Portland cement, the kinetic model (Tomosawa model, T model) of hydration was analyzed and simplified. In simplified T model, the hydration process was controlled by mass transfer, interfacial reaction and diffusion process at different stages, respectively. Based upon the degree of hydration measured by chemical bound water method, T model and simplified T model were applied to investigate the relationship between the degree of reaction and hydration rate for cement pastes with different water-cement ratios. The results show that the effects of w／c on the parameters in the T model are different. Along with the change in w／c, the coefficients of mass transfer are almost unaffected, the interfacial reaction coefficient is less affected, while the diffusion coefficient is significantly affected. The development trend of hydration rate with degree of reaction at different stages can be well simulated by simplified T model, which is not affected by w／c. However, the critical degree of hydration from interfacial reaction to diffusion process is increased with the increasing of w／c.