Submicrometric Picture of Plaster Hydration: Dynamic and Space-Resolved Raman Spectroscopy versus Kinetic Monte Carlo Simulations
Résumé
To propose a picture of plaster hydration at a submicrometric scale, we have
developed a kinetic Monte Carlo simulation model of gypsum crystal growth. Raman spectroscopy
is used to check the model and to assign physical values to the parameters. Special focus is put on
the effects of increasing plaster-to-water ratio and using citric acid as an additive. The hypothesis
about the autocatalytic growth of gypsum needles during the first stage of the reaction is confirmed
by the correct simulation of the induction period preceding the fast growth regime. The aspect
ratio of gypsum needles, defined as the ratio of needle length and width, emerges as a relevant
parameter to control both dynamics and material structure. Addition of citric acid is known to
produce compact gypsum crystals instead of long needles. The choice of a small aspect ratio is
sufficient for the simulations to reproduce the effects of citric acid, including the slowing down of
the reaction without recourse to fitting parameters. The kinetic Monte Carlo simulation model
proved to be a predictive tool that could assist the rational development of novel additives and reagent treatments with the aim of
producing materials with predefined properties.