Coupling thermodynamics and digital image models to simulate hydration and microstructure development of portland cement pastes

Equilibrium thermodynamic calculations, coupled to a kinetic model for the dissolution rates of clinker phases, have been used in recent years to predict time-dependent phase assemblages in hydrating cement pastes. We couple this approach to a 3D microstructure model to simulate microstructure development during the hydration of ordinary portland cement pastes. The combined simulation tool uses a collection of growth/dissolution rules to approximate a range of growth modes at material interfaces, including growth by weighted mean curvature and growth by random aggregation. The growth rules are formulated for each type of material interface to capture the kinds of cement paste microstructure changes that are typically observed. We make quantitative comparisons between simulated and observed microstructures for two ordinary portland cements, including bulk phase analyses and two-point correlation functions for various phases. The method is also shown to provide accurate predictions of the heats of hydration and 28 day mortar cube compressive strengths. The method is an attractive alternative to the cement hydration and microstructure model CEMHYD3D because it has a better thermodynamic and kinetic basis and because it is transferable to other cementitious material systems.