Measurement and simulation of the dissolution rate at room temperature in conditions close to a cement paste: from gypsum to tricalcium silicate

The measurement of the dissolution rate was performed in conditions close to a cement paste; thanks to a specifically designed experimental device that was calibrated with gypsum. For tricalcium silicate (C3S) dissolved in several electrolytes at room temperature, it appeared that the average dissolution rate of C3S was modified with some relatively small concentrations of electrolytes. The strongest effects corresponded to the inhibiting effects of hydroxide and calcium ions that were taken into account to simulate the dissolution rate of C3S using Lasaga’s equation. Compared to dissolution experiments in saturated portlandite solution during which hardly any dissolution of C3S occurred for several hours, the reported simulations tend to be an indirect proof in favor of the existence of an additional mechanism that restricted further the dissolution of C3S. This mechanism is expected to be related to the very rapid formation of thin layer composed of intermediate phase around C3S grains.