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Aluminate cement is a special cement with weakly alkaline calcium aluminate as its main component. It is made from bauxite and limestone as raw materials, calcined to form clinker with calcium aluminate as the main component and about 50% alumina content, and then ground into a hydraulic cementitious material. It is also known by various names: refractory cement, 625 cement, aluminate cement, CA-50 cement, etc.
Aluminate cement has a high heat of hydration. It should not be used in large concrete projects and moist, high-temperature environments. It is most suitable for use in environments between 5-35 degrees. In refractory castable engineering, adding a certain proportion of high-temperature refractory cement to the castable can make the castable set quickly and have strong compactness during construction.
Aluminate cement has strong resistance to sulfate attack. The cement stone structure of aluminate cement is dense, mainly composed of low-calcium aluminate with very little calcium oxide content, making it suitable for projects requiring high resistance to sulfate attack.
Aluminate cement has good heat resistance. It will maintain a solid-phase state in high-temperature environments, and the strength of the cement will not change.
Aluminate cement has strict usage requirements. Its early strength grows quickly, making it suitable for emergency rescue projects or projects requiring high early strength. However, the later strength of aluminate cement declines, especially in hot and humid environments above 30°C, where the strength drops faster and more significantly. This can severely damage the structure of the castable. Therefore, the use of aluminate cement in structural engineering should be done with caution.
Aluminate cement has weak alkali resistance. It will be eroded when in contact with alkaline solutions. Even the presence of a small amount of alkaline compounds in concrete aggregates can cause erosion, so aluminate cement should not be used in projects that come into contact with alkaline solutions.
Check the production date of the cement. The aluminate cement bags will have batch numbers indicating the production date. Cement that has been stored for a long time is prone to moisture and clumping, so checking the production date is important.
Inspect the packaging appearance. Check if the packaging is intact and if there are any signs of damage. Typically, the sealing edges of the package should be circular and closed.
Weigh the packages. Aluminate cement can be packaged in full packages or smaller subdivided packages. A full package usually weighs 50 kg. Randomly select a few packages and weigh them; an error of less than 3 kg is within the normal range.
Check the color. Aluminate cement is usually yellow-brown, and sometimes gray. In contrast, ordinary construction cement is gray. When purchasing, it is best to choose yellow-brown cement. Note: Pay attention to cement that appears yellow or white. Yellow indicates that the clinker is under-fired, while white indicates excessive slag content, resulting in low strength.
Feel the texture. Squeeze the cement powder with your fingers; if it feels gritty and contains many coarse, hard particles, or shows signs of moisture and clumping, it should not be purchased.
