According to the chemical composition, calcium aluminate cement can be divided into two types: ordinary calcium aluminate cement ( 53-72% Al2O3, 21-35% CaO ) and pure calcium aluminate cement (72-82% Al2O3, 19-23% CaO ). The ordinary calcium aluminate cement can be divided into low iron-type (Fe2O3<2%) and high iron-type (37~16% Fe2O ), and low iron calcium aluminate cement can be divided into alumina cement (53-56% Al2O3, 33-35% CaO), aluminum-60 cement (59-61% Al2O3, 27-31% CaO) and low calcium aluminate cement (65-70% Al2O3, 21-24% CaO). Pure calcium aluminate cement can be divided into two types: ordinary type (72-78% Al2O3) and ultra-high aluminum type ( 78-85% Al2O3). In addition, there is fast hardening early-strength calcium aluminate cement.
The sintering process is the main method to produce high alumina cement, and the pure limestone is the calcium oxide raw material to produce all kinds of calcium aluminate cement. Sintered alumina is used to produce high-grade calcium aluminate cement, while low iron and low alumina bauxite are used as alumina materials of middle and low alumina cement. Pure calcium aluminate cement or high alumina cement is the most important hydraulic cement used in the combination of refractory castables and gunning refractories. In the construction of refractory castable linings, the water temperature, water addition, mixing strength, mixing time, temperature and temperature rising rate must be strictly controlled, among which the temperature is the most important parameter because it significantly affects the generation of cement bonding phase and the discharge of water in the initial heating stage.
The setting and hardening speed of calcium aluminate cement are also related to caring temperature. With the increase of caring temperature, CA2 mineral coagulates and hardens faster, while CA mineral is abnormal, which is faster at about 20℃, slow at 30℃, and faster again when the temperature is higher than 30℃.
According to the phase transition when heating the calcium aluminate hydrate, it is very important to choose proper curing conditions because the hydration of calcium aluminate cement varies in different curing conditions.
