Elements of chemomechanics of calcium leaching of cement-based materials at different scales

Calcium leaching of cementitious materials has been identified as a severe long-term chemical degradation scenario of concrete structures. While the coupled diffusion–dissolution processes are well understood now, separating the effects of the incongruent dissolution of calcium (bound in different forms in the solid phases of the porous material) on the mechanical performance of cement-based materials remains a challenging task, requiring a break-down of the problem in its elementary components situated at different scales. This is the focus of this paper which reviews recent developments in chemomechanics of calcium leaching induced aging of cement-based materials: (1) a combined experimental–theoretical investigation of the strength domain of unleached and homogeneously leached cement-based materials, by means of a non-linear homogenization approach, which captures the frictional enhancement of a cement-based matrix reinforced by rigid inclusion; (2) a micro-to-macroscopic chemomechanics theory based on volume averaging of the local energy dissipation, which distinguishes the effect of the two governing leaching processes in cement-based materials: Portlandite dissolution and leaching of calcium from the calcium–silicate–hydrate structure. Combined with (3) an advanced predictive model of the two-phase dissolution process, prediction and anticipation of the mechanical integrity of concrete structures subjected to severe chemical degradation becomes possible.