MODELING OF THE EFFECT OF ELECTROLYTES ON THE RATE OF EARLY HYDRATION OF TRICALCIUM SILICATE

The hydration of the phases contained in hydraulic binders Such as tricalcium silicate (C3S) in Portland cement proceeds through a dissolution-precipitation process as explained a long time ago by H. Le Chatelier. The global kinetics of hydration Of C3S in water or in electrolytes has been extensively studied by numerous experimental techniques. However less attention has been devoted to study the dissolution Of C3S as periods, where only dissolution occurs, are difficult to study due to the very rapid precipitation of hydrates. Thus a specific device has been developed to measure the average dissolution rate of C3S paste in several electrolytes. From these experimental data, it was possible to define the parameter of Lasaga's equation and to model the dissolution rate of C3S in different electrolytes. The simulation was quite accurate at the exception of saturated linie solution. For this later case an additional mechanism is expected to restrict the dissolution rate.