Mesoscopic mechanisms of dicalcium silicate dissolution

Abstract

Dicalcium silicate dissolution is crucial in cement hydration and provides long-term durability. However, our understanding of its dissolution process is limited due to its multiscale nature. To resolve this limitation, we combine rare event molecular dynamics and kinetic Monte Carlo (KMC) techniques. At the nanoscale, we reveal the relationship between surface Ca^2＋ coordination chemistry and dissolution free energy barriers. Leveraging this knowledge, KMC simulations accurately predict the apparent dissolution activation energy and the sigmoidal relationship between dissolution rate and solution activity observed in experiments. Importantly, we find that dislocations have minimal impact on dissolution rates in grains and fast-dissolving cleavages. Instead, these rates are primarily determined by spontaneous pit opening and coalescence on surfaces, and the receding corners and edges within dissolving grains. This multiscale framework paves the path for fundamental studies and quantitative prediction of dissolution–precipitation processes widely encountered in cement chemistry, carbon sequestration, and enhanced geothermal systems.