Mesoscale Mechanisms of Cement Hydration: BNG Model and Particle Simulations

Cement paste is the most widely used artificial material on Earth, causing massive CO2 emissions. To address the problem, new chemical formulations are being explored, but these come with uncertainties around the kinetics of strength development and degradation. This kinetics is largely controlled by the precipitation of mesoporous solid phases from ionic aqueous solution. Modeling the precipitation process is a key step to understand and control the properties of future, more sustainable, cements. This manuscript starts by considering the classical boundary nucleation and growth (BNG) model of cement minerals precipitation. The mechanisms of nucleation and growth and the corresponding parameters governing the model are discussed. The next step is to relate these mechanisms and parameters to the chemistry of the liquid and solid phases involved. This requires more fundamental models, and, to this end, nanoparticle simulations of cement mineral precipitation and morphology development are presented. These simulations are indeed shown to relate some input parameters of the BNG model to the chemistry of the paste. An outlook is finally provided, discussing some outstanding extensions of nanoparticle simulations that could deepen the current understanding of cement hydration.