How shrinkable grains dry, crack, and heal: predicting these behaviors with three state variables

Granular materials often crack when they dry, affecting the performance of structural materials, coatings, and geological formations. In many cases, the individual grains are porous and shrink as they dry. Here, we describe how this shrinkability influences crack evolution. Using a combination of poroelasticity theory, discrete-element simulations, and experiments, we find that cracking behavior can be predicted from three state variables that arise from the interplay between fluid transport, grain shrinkage, capillary cohesion, and substrate adhesion. Our results provide a way to control crack evolution and ultimately could pave a way to better manage drying-induced cracks in engineering applications.