Bishnoi – Nucleation and growth kinetics and the density of C-S-H
Shashank Bishnoi (Université Laval) and Karen L. Scrivener (Ecole Polytechnique Fédérale de Lausanne)
This study investigates various possible mechanisms of nucleation and growth applied to the hydration of alite using the microstructural modelling platform μic. It is first shown that the Avrami and Cahn equations are not suitable for application to alite-like systems. Comparison of the traditionally accepted nucleation and growth mechanism with experimental measurements reveals that while this mechanism can explain the acceleration in the hydration rate, the deceleration that follows cannot be explained. It was also found that the resistance to flow of ions offered by the layers of hydrates covering the alite particles cannot explain the deceleration. The deceleration could be reproduced when a loosely packed C-S-H was assumed to fill a large part of the microstructure, with its packing improving with time. It is proposed that during the early hours of hydration, a loosely packed C-S-H fills a large fraction of the microstructure and the further development of its microstructure occurs due to an increase in its packing.