Mechanism of C 3S dissolution and problem of the congruency in the very initial period and later on

Abstract

Our work is aimed at evidencing that the superficial hydroxylation process, by protonation, of anhydrous calcium silicates, such as C 3S or β-C 2S and the establishment of the congruent dissolution state of these solid compounds are related problems. The hypothesis from what we develop our arguments, allow to account for the peculiar shape of the Ca/Si variation curve as a function of hydration time, obtained by ESCA. From lixiviation tests carried out on C 3S, using a fast flow of solvent saturated with respect to C-S-H, it is shown that C 3S can dissolve almost entirely, the little apparent deviation from congruency being interpreted by the formation of a small amount of C-S-H, whose Ca/Si atomic ratio is close to 1.