Practical evidence and experimental demonstration of the Liesegang phenomenon in the carbonation process of lime mortars in exposed masonries

Abstract

Liesegang rings have been noticed in laboratory experiments with lime mortars but very few references mention their presence in mortars exposed outdoors. To date, authors have linked the occurrence of Liesegang patterns to mortars prepared with long matured limes, but here we show that very coarse and poor quality lime mortars may also develop similar patterns. SEM observations and EDS measurements on samples taken from exposed mortars show that calcium content varies along the banding sequence, and measurements made along naturally occurring banded patterns prove that the spacing law characteristic of the Liesegang phenomenon applies to them. One case showed that the carbonation banding follows a trendily revert pattern, while a second one fits in an equidistant-type pattern. The occurrence of such irregular patterns may be governed by the presence of a drying process superimposed on the normal diffusion process along the carbonation front.