ã€China Aluminum Network】 Aluminum aluminate cement is made of bauxite and limestone as raw materials, calcined with calcium aluminate as its main component, aluminum oxide content of about 50%, and then hydraulically made Cementitious materials. Aluminate cement is often yellow or brown, but also gray. The main minerals of aluminate cement are calcium aluminate (CaO·Al 2 O 3 , abbreviated to CA) and other aluminates, and a small amount of dicalcium silicate (2CaO·SiO 2 ).
According to the national standard (GB201-2000), the density and bulk density of aluminate cement are similar to that of ordinary portland cement. Its fineness is ≤20% for specific surface area ≥300m2/kg or 45μm sieve. Aluminate cement is divided into four types: CA-50, CA-60, CA-70 and CA-80. The setting time and strength of each type of cement must not be lower than the standard.
Aluminate cements include three types of cements: calcium aluminate, barium aluminate, and barium aluminate zirconate. Among them, bismuth aluminate cement has the characteristics of fast rigidity, high strength, and high refractoriness.
Aluminate Cement Features:
Aluminate cement hardens quickly. The intensity of 1d can reach more than 80% of the higher intensity, and is mainly used for urgent engineering projects such as national defense, roads and special emergency repair projects.
Aluminate cement has large hydration heat and concentrates heat. The amount of heat of hydration released in 1d is 70% to 80% of the total amount, so that the internal temperature of the concrete rises higher. Even if the construction is carried out at -10°C, the aluminate cement can quickly set and harden, and can be used for construction in winter. .
Alumina cement under ordinary hardening conditions, because the cement stone does not contain calcium trialuminate and calcium hydroxide, and a greater degree of compaction, so it has a strong role in the resistance to sulfate corrosion.
Aluminate cement has high heat resistance. If the use of refractory coarse aggregate (such as chromite, etc.) can be made using the temperature of 1300 ~ 1400 °C heat-resistant concrete.
However, the long-term strength and other properties of aluminate cement have a tendency 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 works in high-temperature and high-humidity environments. It is only applicable to emergency military projects (building roads, bridges), repair work (plugging, etc.), temporary works, and the preparation of heat-resistant concrete.
In addition, the mixing of aluminate cement with Portland cement or lime not only produces flash condensation, but also results in cracking and even destruction of the concrete due to the formation of highly alkaline calcium aluminate hydrate. Therefore, in addition to mixing with lime or Portland cement, it must not be used in contact with unhardened Portland cement.
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