The effect of the firing temperature of clay roofing tiles on the mechanisms of frost action

Abstract

Frost resistance of roofing tiles is of both practical and scientific interest, especially since the frost action mechanisms are still not well understood. Textural characteristics and low temperature dilatometrical behavior (from -40 to +40 °C) of clay roofing tiles are correlated with the type of frost damage identified by the standard procedure, EN 539-2, method C, giving the insight into the dominant frost action mechanism (mechanism of closed container, hydraulic pressure, and the ice lens mechanism). The samples of clay roofing tiles from the same batch were fired in laboratory conditions at different temperatures (920, 970, 995, 1015, 1055 and 1085 °C) and in the industrial plant (1100 °C). Based on the mentioned correlations, the change of the dominant frost action mechanism is explained by porous structure differentiation with the temperature, from a closed container at lower to micro ice lens formation at higher temperatures, with the hydraulic pressure mechanism contributing considerably in all the temperatures. The obtained correlations are of specific importance in taking fast and right corrective measures in a defined production line in order to improve the frost resistance characteristics of the final product.