Liesegang rings in differential deterioration patterns of lime mortars

Differential erosion is a deterioration pattern common in stone and mortars exposed to environmental agents. The differential morphology is usually determined by specific intrinsic characteristics. The case analysed here corresponds to a peculiar situation of rhythmic precipitation inside lime mortars following a physical process designated as Liesegang phenomenon. The rhythmic reaction occurs between calcium hydroxide and carbon dioxide in the early steps of the carbonation process, and when appropriate boundary conditions are met, a more or less “perfect” sequence of higher and lower concentration of the carbonated lime (calcite) is formed. This sequence is called a series of Liesegang rings. The rings have distinct hardness and, when exposed to erosion agents, a differential pattern may be formed. In certain regions, this differential erosion pattern was given the name of Flos tectorii.