High-alumina cement refers to a type of binding material that is fast-hardening, high-strength, heat-resistant, and corrosion-resistant. Its main characteristics include high early strength, resistance to high temperatures, and resistance to corrosion. High-alumina cement is mainly used in urgent construction projects with tight schedules, such as pressure grounding, roads, and special repair projects, and can also be used in construction projects during winter. High-alumina cement is a water-hardening binding material mainly composed of aluminum salt minerals, which is made by calcination and fine grinding of raw materials such as bauxite and lime in a certain proportion. A water-hardening binding material ground from clinker that mainly contains calcium aluminate and approximately 50% alumina is called high-alumina cement.
The early strength characteristics of high-alumina cement make it suitable for emergency repair projects, but its later strength will decrease, limiting its use in structural engineering. The high heat of hydration of high-alumina cement makes it suitable for concrete engineering that requires low-temperature curing. High-alumina cement has strong resistance to sulfate erosion, and its hydration process does not generate free calcium hydroxide but rather produces aluminum hydroxide gel, which forms a protective film on the surface of particles. However, the erosion resistance decreases during the later stage of crystal transformation. High-alumina cement can be used as a binding material for heat-resistant concrete, which can be configured as heat-resistant concrete.
The main function of high-alumina cement is to prepare temporary and fast-constructed, emergency repair, and supporting concrete, mix it into repair and supplementary materials for furnaces, and mix it with anti-sulfate mortar and other building materials. However, the cost of using this product alone is relatively high, and the effect is not good. Therefore, we usually recommend that customers mix high-alumina cement mortar with refractory sand for use. The formula for high-alumina cement mortar is high-alumina cement: refractory sand =1:3, and the water-to-binder ratio formed by this formula is 0.45, which is very suitable for construction and use.
The main uses of high-alumina cement are as follows:
Preparation of amorphous refractory materials.
Study of special cements such as gypsum-bauxite expansive cement and self-stressing cement.
Projects with special needs such as emergency construction, repair, anti-sulfate, and winter construction.
Care must be taken when using high-alumina cement as a binding material in structural engineering. However, since the hydration products of high-alumina cement do not contain free Ca(OH)2 and there is no C2S mineral in Portland cement, it will not appear as a cement binder. During the heating and cooling process, the volume of refractory concrete is unstable due to the repeated formation of CaO and Ca(OH)2, as well as the polycrystalline transformation of β-C2S. In addition, high-alumina cement has early strength and can shorten the rotary kiln maintenance period, which is called "one-day concrete." Therefore, high-alumina cement is widely used in the refractory material industry.
