Plaster Hydration at Different Plaster-to-Water Ratios: Acoustic Emission and 3-Dimensional Submicrometric Simulations

To relate the dynamics of the reaction to the structure and properties of the resulting material, we develop a three-dimensional submicrometric simulation model for plaster hydration, valid in the entire range of plaster-to-water ratios. Stochastic rules govern the growth without overlap of gypsum needles. The precipitation process is assumed to drive the dissolution of plaster grains. The comparison of the simulation results with optical microscopy images at different times and acoustic emission monitoring during the reaction enable us to assign physical values to the length and time scales and to the main parameters of the model. In agreement with X-ray microtomography images of plaster available online (http://visiblecement.nist.gov/plaster.html), the simulation model predicts that hydration of plaster of Paris is incomplete for the usual values of plaster-to-water ratios used in industry.