High alumina cement (previously called bauxite cement) is a hydraulic cementitious material with aluminate as the main mineral component, which is prepared by calcining and grinding with bauxite and lime as raw materials. , also known as aluminate cement. 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 concrete is one of the most important refractory materials, but its properties vary with temperature range. Between room temperature and about 500°C, concrete made with high alumina cement loses more strength than concrete made with portland cement, then at temperatures up to 800°C the two concretes are comparable, but at 1000°C Above, high alumina cement has excellent properties. Between 700°C and 1000°C, a solid reaction occurs between cement and fines. This reaction, called vitrified bond, increases the strength of high alumina cement concrete between 800°C and 1000°C. The reaction rate increases with increasing temperature.
Therefore, CSA concrete made with high alumina cement and crushed fired bricks as aggregates can withstand very high temperatures. Using special aggregates such as fused alumina or silicon carbide can withstand temperatures from 1350°C to over 1500°C. Concrete made of special white calcium aluminate cement and fused alumina aggregate can withstand temperatures up to 1800°C for long periods of time. This cement contains 70 to 80% alumina, 20 to 25% lime and about 1.0% iron and silica. Its composition reaches C3A5. However its price is very high.
Refractory concrete made with high alumina cement has good resistance to acid attack. Firing at 900°C to 1000°C improves chemical resistance. The concrete is ready for use as soon as it has hardened, i.e. it should not be pre-fired. Refractory bricks expand when heated, so expansion joints need to be provided, while high-alumina cement concrete can be cast in its entirety or only to joints of the desired size and shape. Therefore, refractory high alumina cement concrete can withstand considerable thermal shock. Refractory linings can be manufactured by jet manufacturing high alumina cement mortar. When the temperature rise is expected to be as high as 950°C, lightweight concrete made of high alumina cement and lightweight aggregate can be used for thermal insulation purposes. The density and thermal conductivity of this concrete are 500 to 1000kg/m3 and 0.21 to 0.29j/m2.
