The main mineral components of aluminate cement are calcium aluminate and other aluminates, which are often yellow or brown, and some are gray. It includes three cements: calcium aluminate, barium aluminate, and barium zirconium aluminate. It is divided into four types: CA-50, CA-60, CA-70, CA-80. The setting time and strength of each type of cement shall not be lower than the standard.
1. Aluminate cement sets and hardens fast. The 1d strength can reach more than 80% of the highest strength. It is mainly used for emergency projects such as national defense, roads and special emergency repair projects.
2. The heat of hydration of aluminate cement is large, and the heat release is concentrated. The heat of hydration released within 1d is 70% to 80% of the total, which makes the internal temperature of the concrete rise higher. Even if it is constructed at -10°C, aluminate cement can quickly set and harden, and can be used for winter construction projects.
3. Under ordinary hardening conditions, aluminate cement does not contain tricalcium aluminate and calcium hydroxide, and its compactness is relatively large, so it has strong sulfate corrosion resistance.
4. Aluminate cement has high heat resistance. For example, refractory coarse and fine aggregates (such as chromite, etc.) can be made into heat-resistant concrete with a service temperature of 1300 to 1400°C.
5. The long-term strength and other properties of aluminate cement tend to decrease, and the long-term strength is reduced by about 40% to 50%. Therefore, aluminate cement is not suitable for long-term load-bearing structures and projects in high-temperature and high-humidity environments. Aluminate cement is only suitable for emergency military projects (roads, bridges), emergency repair projects (plugging, etc.), temporary projects, and the preparation of heat-resistant concrete.
6. The mixing of aluminate cement and portland cement or lime not only produces instantaneous setting, but also causes the concrete to crack or even destroy due to the formation of high alkaline hydrated calcium aluminate. Therefore, during construction, the aluminate cement shall not be mixed with lime or portland cement, nor shall it be used in contact with unhardened portland cement.
