Real time kinetics of hydration of calcium silicates with light and heavy water has been investigated at the mesoscopic length scale with the ultra small-angle neutron scattering technique. The scattering data could not be interpreted in terms of a linear theory of phase formation. The predictions of nonlinear theories on the dynamics of phase formation have been examined. The validity of the dynamical scaling hypothesis for phase formation has also been explored. For the real time hydration of silicates with light water, reasonable agreement has been observed with a dynamical scaling hypothesis with a different measure of the characteristic length. The temporal evolution of the characteristic length does not follow a power-law relation with time. It increases with time and reaches a plateau. The mesoscopic structure of the hydrating pastes could not be described in terms of a classical porous medium with a well-defined specific inner surface. In the case of hydration with light water, the hydrating mass exhibits a mass fractal nature throughout hydration, with the mass fractal dimension increasing with time and reaching a plateau. But, in the case of hydration with heavy water, no agreement has been observed with the scaling hypothesis. For hydration with heavy water, the microstructure of the hydrating mass undergoes a transition from mass fractal to surface fractal and subsequently to mass fractal. The qualitative and quantitative features of the kinetics of hydration, as measured in scattering experiments, are strikingly different for hydration with light and heavy water.

• Received 24 February 2005

DOI:https://doi.org/10.1103/PhysRevB.72.224208