Effects of sulphate, calcium and aluminum ions upon the hydration of sulphoaluminate belite cement

Abstract

In the model sulphoaluminate belite cement, the process of hydration is governed by the diffusion and transport phenomena of the main ionic species. The sulphate components and combined sulphate and aluminium ions, exert an accelerating effect upon the kinetics of sulphoaluminate belite cement hydration. Aluminium and calcium ions delay the hydration by creating a retarding layer which can be considered a co-precipitate of aluminium and calcium hydroxides. This is revealed in the calorimetric curves by the duration of induction period and also by the intensities of the main peaks. The appearance of small additional peaks characterizes the formation of ‘primary ettringite’, due to the presence of sulphate ions in aqueous solution. The intensities of these peaks depend on the ion concentration too.