Portlandite, one of the main products of cement hydration and which normally comprises about 25% of the paste, is a principal buffer responsible for maintaining the high pH in response to interactions between the paste and its service environment. The kinetics of these environmentally - conditioned reactions are often important. However the present approach to kinetics is handicapped by lack of fundamental data. For example, we lack data on the kinetics of dissolution of portlandite. Portlandite is congruently soluble and its dissolution rate and mechanism are reported. Single crystals of portlandite have been grown and their effective surface area measured. Dissolution rates are reported into initially pure water as functions of calcium hydroxide concentration. The impacts of low concentration of other ions, e.g., chloride, on congruent dissolution kinetics are reported.

Resumen del trabajo presentado en el XIII International Congress on the Chemistry of Cement, celebrado en Madrid (España), del 3 al 8 de julio de 2011