Biochemical corrosion of ceramic roofing tiles by lichen actions

Abstract

The effect of lichens on the qualify of ceramic roofing tiles was investigated with respect to textural changes and low temperature dilatation values. For this purpose, two types of ceramic roofing tiles (extruded and pressed) aged 6 to 10 years were examined, as well as ceramic model systems formed with Cu-slag and Cu-oxide powder additions. The identified lichen family was Verrucariales. The fundamental interactions between lichens and the ceramic materials have been identified as the physico-chemical processes based on oxalic acid action which cause the aging and finally thedestruction of materials. Cu-oxide as the raw mixture additive changed the quality of the surface tile, having a positive effect on the response of the ceramic tiles to the oxalic acid action. The textural modifications and the formation of the identified destructive crystal phase, whewellite, were slowed. © 2008 DVS Verlag GmhH.