Algal colonization kinetics on roofing and façade tiles: Influence of physical parameters

Algal growth is responsible for aesthetic defects on roofing tiles. Accelerated water-streaming tests were done on different building materials. The results establish the ranges of porosity and roughness that can initiate the colonization under humid saturation. A smooth surface is then recommended to reduce the settlement. Experiments done on limestone and clay tiles demonstrate that coupling high porosity and rough surface should be banished to avoid any rapid algal colonization. However, the alkaline composition of concrete tiles can strongly affect the algal settlement, whatever their intrinsic porosity and roughness. Observations by Environmental Scanning Electron Microscopy show that calcite crystals could promote the settlement of algae on the surface.