Influence of firing temperature on frost resistance of roofing tiles

In cold districts, prevention against frost damage of roofing tiles caused by the expansion due to the freezing of water absorbed in the numerous pores in the tile material has becomes a serious problem. It is known that the frost damage is closely connected to the porosity and water absorbing capacity of the roofing tile. Both the porosity and water absorbing capacity of the material can be controlled by the firing temperature. In this work, in order to examine the effect of firing temperature on the frost resistance, tiles fired at different temperatures of 900–1200 °C were fractured by four point bending after applying freezing treatment at low temperatures of −10, −30 and −50 °C. At any firing temperature up to 1100 °C, both fracture stress and fracture toughness increased with the firing temperature, but they dropped above 1100 °C. Furthermore, an obvious decrease in fracture stress with decrease in freezing temperature was observed for the samples fired at 1200 °C. Thus, it was concluded that the roofing tile fired at temperatures of up to 1200 °C forming mullite with a glass phase from the reaction with quartz and feldspar could minimize the frost damage.