Dissolution kinetics of densified and undensified silica fume in a KOH solution at pH 13 and 23 °C

The reaction kinetics of silica fume in Portland cement binders directly affect porosity and strength development during the early and intermediate stages of hydration. This study sheds light on silica fume’s dissolution rate and mechanism at 23 °C in a 0.1 mol L^-1 KOH solution as a function of its composition, specific surface area, and saturation state. Conductivity measurements are used to continuously track the reaction progress and correlate it to dissolved concentration. The dependence of the dissolution rate on silica fume surface area and saturation state is described, and a rate equation consistent with standard chemical kinetics is developed to model the rates as a function of the thermodynamic driving force. The inferred rate equation can be used to improve models of microstructure evolution in blended cement binders.