Also known as high-aluminium heat insulating brick. Lightweight refractory material with alumina content above 48%, mainly composed of mullite and glass phase or corundum. The bulk density is 0.4 to 1.35 g/cm3. The porosity is 66%～73%, and the compressive strength is 1～8MPa. Good thermal shock resistance.

Usually high alumina bauxite clinker is added with a small amount of clay, after grinding, it is poured and formed in the form of mud by gas generation method or foam method, and fired at 1300～1500℃. Sometimes industrial alumina can also be used to replace part of the alumina clinker. It is used for the lining and heat insulation layer of masonry kiln, as well as the parts without strong erosion and erosion of high-temperature molten materials. When directly in contact with the flame, the surface contact temperature shall not be higher than 1350℃.