Thermos-Physical Properties of Insulating Refractory Materials You can witness the use of refractory materials in multiple fields like iron and steel, ceramics, petrochemical, electric power, etc. Refractory bricks are also a kind of refractory material. These are necessary as basic materials to ensure the functioning of several industries. Refractory materials are inorganic, nonmetallic materials that have a high refractory degree. They include products made by specific processes for specific purposes and natural ores. These materials come with various thermal insulating properties. The bulk density of refractory materials is an important physical property expressed using the units - kilograms per cubic meter or pounds per cubic foot.