Dissolution-precipitation kinetics during C3S hydration: A holographic interferometry study

Tricalcium silicate C3S has been widely employed in model systems to interpret the complex mechanisms of cement hydration. The present study aims at providing an accurate description of the dissolution rate of C3S by implementing a new approach based on holographic interferometry. We propose a protocol that allows the measurement of the pure dissolution rate constant of the C3S phase by experiments performed in supersaturated conditions with respect to C-S-H. In these experiments, a flat polycrystalline surface of C3S was monitored in a quiescent solution. The amount of calcium released within the holographic cell was measured and the aqueous solution composition was constrained to the C-S-H stoichiometry at the interface. An equilibrium approach was applied to assess interfacial pH, saturation indexes, and C-S-H precipitation at the experimental conditions. The rate law of the pure dissolution of C3S was assessed in conditions ranging from far to close-to-equilibrium.