Applications of CA-70 Calcium Aluminate Cement

Aluminate cement is a hydraulic cementitious material made from bauxite and limestone through calcination, resulting in clinker with calcium aluminate as the main component and an alumina content of approximately 50%, which is then ground. Aluminate cement is typically yellow or brown, but can also be gray. The main minerals in aluminate cement are monocalcium aluminate (CaO·Al₂O₃, abbreviated CA) and other aluminates, as well as small amounts of dicalcium silicate (2CaO·SiO₂). Its color is mostly gray and white.

The density and bulk density of aluminate cement are similar to those of ordinary silicate cement. Its fineness is defined as a specific surface area ≥300 m²/kg or a residue ≤20% on a 45 μm sieve. Aluminate cement is classified into four types: CA-50, CA-60, CA-70, and CA-80. The setting time and strength at each age for each type of cement must not be lower than the standards specified.

calcium aluminate cement

Calcium Aluminate Cement

CA-70 cement is a high-purity refractory cement in the Ya brand aluminate cement series. Due to its high purity, it is also called calcium aluminate cement. It is typically packaged in 25kg bags. Calcium aluminate cement (CAC), also known as high-alumina cement (HAC), is a hydraulic cement whose main mineral component is calcium aluminate.

Composition and Classification of Calcium Aluminate Cement

Calcium aluminate cement can be classified into two categories according to its chemical composition: ordinary calcium aluminate cement (Al₂O₃ 53–72%, CaO 21–35%) and pure calcium aluminate cement (Al₂O₃ 72–82%, CaO 19–23%). Ordinary calcium aluminate cement can be further divided into low-iron type (Fe₂O₃ < 2%) and high-iron type (Fe₂O₃ 7–16%). Low-iron calcium aluminate cement can be further divided into bauxite cement (Al₂O₃ 53-56%, CaO 33-35%), Alumina-60 cement (Al₂O₃ 59%-61%, CaO 27-31%), and low-calcium aluminate cement (Al₂O₃ 65-70%, CaO 21-24%).

Pure calcium aluminate cement can be divided into two types: ordinary type (Al₂O₃ 72-78%) and ultra-high alumina type (Al₂O₃ 78-85%). In addition, there is rapid-hardening, early-strength calcium aluminate cement. The chemical composition and mineral composition of two types of pure calcium aluminate cement are described. The chemical composition and mineral composition of different types of calcium aluminate cement are also discussed.

Applications of Calcium Aluminate Cement

Calcium aluminate cement is mainly used as a binder for refractory castables and refractory sprayed materials. The requirements for ordinary calcium aluminate cement are mainly twofold:

• (1) Suitable setting time to ensure sufficient working time. Generally, initial setting should be greater than 1 hour, and final setting less than 8 hours; the shorter the time interval between initial and final setting, the better.

• (2) Sufficient early strength, i.e., reaching 60%~70% of the strength specified for the cement grade after one day of curing, and reaching over 90% after three days of curing.

For pure calcium aluminate cement, in addition to the above two points, it is also required to have a certain degree of refractoriness and good workability to meet construction requirements and high-temperature use requirements.

Medium and low-grade refractory castables, such as clay-based and high-alumina castables, use ordinary calcium aluminate cement as a binder. High-grade refractory castables, such as corundum, mullite, chromium-containing corundum, and corundum-spinel castables, use pure calcium aluminate cement as a binder. The amount of calcium aluminate cement added to ordinary refractory castables is 10%~20%, to low-cement refractory castables is 5%~7%, and to ultra-low-cement castables is less than 3%. Among monolithic refractories, castables using calcium aluminate cement as a binder are widely used.

• (1) Clay-based castables have a service temperature of 1300-1450 degrees Celsius and are generally used as linings for steel rolling furnaces, various heat treatment furnaces, boilers, vertical kilns, and rotary kiln preheating zones.

• (2) High-alumina castables have a service temperature of 1400-1550 degrees Celsius and can be used for linings and burners in various heat treatment furnaces, electric arc furnace tapping troughs, high-temperature sections of lime vertical kilns, rotary kiln heads, and power plant boiler linings.

• (3) Corundum castables have a service temperature of 1500-1650 degrees Celsius. Mainly used for linings of various high-temperature furnaces and components, including impregnation pipes in vacuum degassing devices for molten steel, linings for integral spray guns in injection metallurgy and argon blowing, linings for the triangular area of ​​electric arc furnace tops, LF furnace covers, and high-temperature wear-resistant linings for catalytic cracking reactors in the petrochemical industry.