Hydration kinetics modeling of sodium silicate-activated slag: A comparative study

Abstract

A hydration kinetics model for sodium silicate-based alkali activated slag (AAS) is proposed. The hydration kinetics model for AAS is derived either using mass conservation during internal phase transformation, or by considering chemical affinity of hygro- (thermo-) chemical kinetics by adopting parameters obtained from various calculations and experiments. The obtained modelling result indicates that although the amount of water consumed by slag is lower than that by OPC at an identical mass ratio, the slag binder experiences larger chemical shrinkage, which leads to a dramatic reduction in the relative humidity during hydration. In addition, the modelling result suggests that the hydration rate after 1 day is higher when the pores are distributed in a wider range of diameters (i.e., capillary pores and gel pores are both present as in OPC), in comparison with the case when the pore distribution is in a narrower range (i.e., gel pores are dominant as in AAS).