Effect of pores on flexural strength of roofing tiles at low temperature

Abstract To understand freezing in roofing tiles at low temperature with the aim of preventing frost damage, the effects of microstructure, pore size, porosity, and pore distribution on flexural strength at low temperature were studied. Strength was determined by four point bending tests at room temperature and low temperatures of -10, -30, and -50°C. Porosity and pore size distribution affected low temperature strength, and freezing time and temperature showed a close correlation with strength. A relationship between porosity P and flexural strength S at low temperature ( -10, -30°C) was found, given by S = S0 exp (-bP), where S0 = 49-58 MPa and b = 4·7-7·4. With a decreasing frozen temperature in the range -10 to -50°C, flexural strength increased, and tiles with lower porosity showed higher strength.