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High alumina cement also refers to cement with calcium aluminate as the main component. Any clinker with calcium aluminate as the main component and about 50% alumina content, and ground hydraulic cementing material, is called high-alumina cement.
1. It is strictly forbidden to mix high alumina cement with portland cement or lime and contact with unhardened portland cement concrete, otherwise it will produce instantaneous setting, making it impossible to construct and the strength is very low. The mixing equipment must be rinsed clean before use.
2. High alumina cement shall not be used in projects that are exposed to large alkaline solutions.
3. The heat of hydration of high alumina cement is concentrated in the early release, and it should be watered and cured immediately from hardening. Generally, it is not suitable to pour large volume concrete.
4. The strength of high alumina cement concrete will decrease greatly in the later period, so it should be designed according to the lowest stability. The lowest stable strength value of high alumina cement concrete is determined by putting the specimen in 50±2℃ water for curing after demoulding, and choosing the lower of the strength value of 7 days and 14 days. When using cement above 525, water-cement ratio less than 0.40 and cement dosage above 400 kg/m3, concrete with minimum stable strength above 200 kg/cm3 can be prepared.
5. When high alumina cement is used for reinforced concrete, the thickness of the protective layer of steel bars shall not be less than 3 cm.
6. Without testing, high alumina cement shall not be added with any additives.
7. High alumina cement should not be used in contact with unhardened portland cement concrete. It can be used in contact with portland cement concrete with demoulding strength, but the contact point should not be kept in a damp state for a long time.
8. The most suitable hardening temperature is about 15°C, and the ambient temperature during construction should not exceed 25°C, otherwise, crystal form conversion will occur and the strength will decrease. The concrete mixed with high alumina cement can't be steam cured.
