Durability of clay roofing tiles: the influence of microstructural and compositional variables

The frost behaviour of 13 industrially manufactured roofing tiles was assessed through a double approach: performing severe freeze/thaw testing (EN 539-2) and calculating durability indices, according to models present in the literature. The products microstructure was fully investigated in terms of physical, technological and compositional parameters, and the results correlated with the frost resistance of roofing tiles. No prediction model was able to reliably foresee the product performances; in particular, the correspondence with the excellent experimental behaviour of the most resistant samples is lacking. Coupling microstructural with compositional variables, new indications came out concerning the design and production of roofing tiles able to withstand adverse climatic conditions. If, once again, bulk density can be considered as the most influent parameter (highest values involve an improved durability), the production of roofing tiles with excellent frost resistance involves also the evaluation of an increased number of product (i.e. raw materials composition, microstructure and phase composition) and processing (i.e. firing temperature) variables.