The mineral composition of high alumina refractory bricks can generally be divided into two categories: main crystal phase and matrix phase. Among them, the main crystal phase is the main body of the high-alumina brick structure. In addition to its high melting point, it must also be fully developed and intact. The matrix is the filler between the main crystal phases. Its quantity is not large, but its composition is complex and its effect is obvious. These two mineral compositions of high alumina bricks are indispensable.

On the premise that the chemical composition of the high alumina brick is fixed, due to the homogeneity of the composition distribution and the difference in the processing technology, the minerals composed of the high alumina brick products have different types, quantities, grain sizes, and bonding states. The difference in structure causes the performance difference of refractory bricks. For example, high alumina bricks and mullite high alumina bricks are basically the same in chemical composition, but their mineral composition is different, so the normal temperature and high temperature performance of their products are quite different. Therefore, the mineral composition of high alumina bricks and the microstructure of high alumina bricks are also important factors that determine the properties of high alumina bricks.

Generally speaking, the organizational structure of high alumina bricks is a heterogeneous body composed of solid substances and gaseous pores. Porosity is an important factor affecting the performance of products at room temperature and high temperature, especially under high temperature conditions, which greatly reduces the resistance of products to external erosion. The reason for the formation of pores is: the air in the material is not completely removed when the high alumina brick is formed; the space is left after the water in the material is removed; the raw material is not fully calcined, some salts that should be decomposed are not completely decomposed, and the ingredients that should be burned are not completely burned. Burning; uneven material composition, uneven shrinkage when fired at high temperature, etc.

However, in the production of some lightweight heat-insulating high-alumina bricks, people also specifically introduce some pores that are evenly distributed. The existence of pores directly affects the porosity, water absorption, bulk density, air permeability and other indicators of high alumina bricks.