A measuring method for the determination of linear thermal expansion of porous materials at high temperatures

A method for measuring linear thermal expansion of porous materials in the high temperature range up to 1000 degrees C is introduced. The measuring device is based on the application of a comparative technique. A bar sample of the studied material is put into a cylindrical, vertically oriented electric furnace. As it is technically difficult to perform length measurements directly in the furnace, a thin ceramic rod which passes through the furnace cover is fixed on the top side of the measured sample. The length changes can be determined outside the furnace in this way provided the measurement is performed at the same time on the sample of a standard material. A practical application of the method is demonstrated with two types of common porous building materials, cement mortar and refractory concrete.