Types of cement for specific requirements are called specialty cements. These cements can be used at very high or very low temperatures. Special cement is a kind of cement with special properties, which is used for certain projects. There are many varieties of special cement. Some special cements can also be used in acid. Special cements such as Portland cement have a very high setting rate. Barium and strontium cements are resistant to radioactive radiation. There are different types of special cements, namely high alumina cement, Sorel cement, Portland cement, waterproof cement, high strength cement, barium and strontium cement.
The properties and applications of special cements are as follows: Special cement refers to a variety of cement with specific properties suitable for specific purposes. After the use of special cement, the building will be endowed with specific functions and play its specific role. Compared with the cement of ordinary buildings, its uses are more extensive. Although the cement of ordinary buildings is solid, it is easily corroded by natural disasters such as insect disasters and rainwater. Special cement can avoid natural disasters, and the erosion of acid rain has little effect on it. Therefore, special cement is often used as the base of high-rise buildings. The cement board is also made of special cement. In addition, special cement can store oil and other substances without leakage.
High alumina cement refers to a fast-hardening, high-strength, heat-resistant and corrosion-resistant cementitious material. Its main characteristics are high early strength, high temperature and corrosion resistance. High alumina cement is mainly used for projects with urgent construction period, such as pressure prevention, road and special emergency repair projects, etc., and can also be used for winter construction projects. High alumina cement is obtained by smelting limestone, bauxite and a small amount of silica and titania in a rotary kiln at 1500°C to 1600°C, and then grinding the resulting product to fineness in the same way as Portland cement. The main components of high alumina cement: calcium oxide (CaO): 38 to 40% calcium oxide (CaO); 45 to 50% alumina (Al₂O₃); 10% alumina (Al₂O₃); 5 to 10% iron oxide (Fe₂O₃).
The important compounds of high alumina cement are monocalcium aluminate, tricalcium pentaaluminate, dicalcium silicate and tetracalcium ferric aluminate.