Thermal expansion of ceramic for a building materials

Control factors of thermal expansion of feldspathic porcelain body for building materials and their control methods are discussed. The additivity can be established between the thermal expansion of feldspathic body consisting of quartz, mullite and glass phase and its amount of constituent phase irrespective of firing time and temperature within an ordinary range of the particle size distribution. However, the actual thermal expansion becomes lower than the value calculated by the method of additivity because of generation of cracks on and vicinity of quartz when its diameter becomes bigger than a certain range of the size. A progress of internal cracks of the porcelain body and its consequent release of stress were clarified in view of changes of the d-spacing of quartz, a decrease of bending strength and an observation of polarizer microscope.