The main crystal phase of magnesia brick is periclase, which has the typical characteristics of general alkaline refractory products. Magnesia-carbon bricks are cheap but have poor thermal shock resistance.

Magnesium bricks are divided into fired magnesium bricks and non-fired magnesium bricks. The fired magnesium bricks are divided into silicate bonded magnesium bricks, direct bonded magnesium bricks and re-bound magnesium bricks. Non-burning magnesia bricks are divided into chemically bonded magnesia bricks and asphalt bonded magnesia bricks.

The fire resistance of magnesium brick can reach above 2000 ℃, and its softening temperature under load varies greatly with the melting point of the cementitious phase and the amount of liquid phase produced at high temperature. Generally, the load softening start temperature of magnesium brick is between 1520 ~ 1600 ℃, while high purity magnesium brick can reach 1800 ℃. The load softening temperature of magnesium bricks does not differ much from the collapse temperature. The linear expansion rate of magnesium brick at 20 ~ 1000 ℃ is generally 1.2% ~ 1.4%, and it is approximately linear. When a liquid phase appears in a brick at high temperatures, it will suddenly shrink. Magnesium bricks have higher thermal conductivity, second only to carbon bricks and silicon carbide bricks in refractory products, and they decrease with increasing temperature. Magnesium bricks have poor thermal shock resistance. Increasing the purity of magnesium bricks can appropriately improve thermal shock resistance. Magnesium bricks have very poor resistance to acid slag. They cannot be directly contacted with silicon bricks during use. Generally, neutral bricks are used to separate them. The conductivity of magnesium bricks is very low at normal temperature, but it cannot be ignored at high temperatures (such as 1500 ° C). If it is used in the bottom of an electric furnace, attention should be paid.