Thermal Properties and Thermal Fracture on Clay Bodies of Roofing Tiles during Firing

Abstract

Thermal properties and thermal fracture on the typical two kinds of clays of the roofing tile bodies i.e. chloritic "Awaji" roofing tile clay body and kaolinitic "Akashi" roofing tile clay body were studied at temperatures of 300•‹ to 700•Ž. Thermal properties observed were as follows: exoand endothermal phenomena on heating, heating weight loss, thermal expansion, bulk density, specific heat, thermal diffusivity, thermal conductivity, modulus of rupture and elasticity, and heat transfer coefficient. They were characteristic of dehydration of the clay minerals and quartz transformation. Assuming that a roofing tile body was a infinite slab of 1.6cm thickness, maximum safe heating or cooling rate "ƒÓmax" on the uniform heating or cooling and temperature difference causing fracture "ƒ¢Tf" were calculated from the following equations.