MASKE: Particle-Based Chemo-Mechanical Simulations of Degradation Processes

The long-term performance of new cementitious materials is uncertain. To help predict durability and manage uncertainty, the models must capture the fundamental mechanisms driving degradation in new binders. Such mechanisms evolve slowly and are strongly chemo-mechanically coupled, all of which challenges the existing simulations. This article presents MASKE: a simulator of microstructural evolution based on interacting particles, which represent multi-phase solid domains in an implicit ionic solution. Chemical reactions, sampled through Kinetic Monte Carlo to reach long time scales, determine precipitation/dissolution processes whose rates depend on solution chemical potentials and on particle interaction energy. Published results from MASKE have already addressed aggregation-driven precipitation of C-S-H nanoparticles, stress-driven dissolution of C3S crystals at screw dislocations, and carbonation of calcium hydroxide in a C-S-H matrix. Here new results are presented, focussing on a nanocrystal of calcium hydroxide and discussing: (i) its chemical equilibrium and dissolution/growth kinetics in stress-free conditions, and (ii) the emergence of pressure-solution and crystallization pressure when the crystal is compressed between platens. Similar chemo-mechanical processes contribute to important degradation modes of concrete, such as creep, sulphate attack, and alkali-silica reaction.