Simulation of capillary shrinkage cracking in cement-like materials

In drying suspensions, water loss leads to a capillary pressure build-up in the liquid phase. This effect may also be observed in fresh cement-based materials subjected to evaporation at an open surface. If under decreasing water content the near-surface solid particles are no longer covered by a plane water film, menisci develop along with an associated build-up of negative capillary pressure, resulting in shrinkage and possibly in cracking. A 2D model for simulating the described physical process is presented. For arranging the particles in the 2D specimen a stochastic–heuristic algorithm is used. Subsequently, the course of the water front between the particles is calculated by assuming a constant curvature of the water surface. Particle mobility is taken into account by adopting interparticle forces and performing equilibrium iterations. The model allows one to study the influences of the particle size distribution as well as of the properties of the liquid phase on the capillary pressure build-up and on the cracking risk.