Influence of lichen biocorrosion on the quality of ceramic roofing tiles

The lichens actions on the quality of ceramic roofing tiles were investigated in view of textural and microstructure changes. The ceramic roofing tiles, aged 20–30 years, as well as the model systems formed with the additives: Cu-slag powder (10 wt.%) and glass material (5 wt.%), presented the subject of the investigation. The interactions between lichens and ceramic body have been identified as the physico-chemical processes based on the oxalic acid actions excreted by lichens. These caused the ceramic matrix deterioration and consequently their ageing. The thalli of the lichen (Verrucaria nigrescens) were examined by scanning electron microscopy and FTIR analyses. The Cu-slag changed the quality of the surface tiles having a positive effect on the tiles response to the oxalic acid action. The textural alternations and the formation of the destructive crystal phase, whewellite, have been slowed down in comparison with the referent ceramic system.