Influence of freezing test methods, composition and microstructure on frost durability assessment of clay roofing tiles

Clay roofing tiles are sensitive to frost action and require testing by repeated freezing and thawing cycles. The research purpose is to predict frost durability, taking into account the effect of clay mineralogy, microstructure (studied by DRX, FRX and mercury porosimetry) and manufacturing parameters, drawing an empirical comparison between methods C and E suggested by the European Standard. Method E is more severe and selective than method C, showing earlier failure and smaller dispersion, which may be explained due to the different saturation process, cooling kinetic and the presence of cloth. The damage increased with the number of cycles, it is substantially affected by the fired clay porosity and calcium content, being consistent with the thermodynamics and kinetics of the mechanisms that lead to failure. The findings provide guidance to improve frost durability based on clay characterisation and industrial process control.