Air-setting refractory castable means that the cement absorbs CO2 in the air during curing and gradually solidifies and hardens. The most commonly used refractory castables are water glass refractory concrete. In addition to its high temperature resistance, water glass refractory castable is also resistant to acids and abrasions; therefore, it is often used as linings for chemical equipment. The process of hardening the water glass refractory castable under natural conditions is very slow, and a coagulant (sodium fluorosilicate, high alumina cement, etc.) is added during construction.