Introduction to Aluminate Refractory Concrete

Aluminate cement heat-resistant concrete is fire-hardening refractory concrete, and the cementing material is aluminate cement. The cementing material of fire-hardening refractory concrete only produces a gelling effect from cement hydration products for some time after the concrete is poured and formed, forming the initial strength of the concrete and supporting the structure itself. When the temperature rises, a series of chemical reactions occur inside the concrete at a temperature of 300 to 1200°C. The cement stone is converted from a low-density hydration product into a high-density non-hydration product (roasted product). The solid phase volume shrinks, and the solid phase As the gaps between them increase, the strength of the concrete decreases. When the temperature continues to rise and the temperature exceeds 1200°C, the solid phase material is sintered to produce a ceramic structure, and the strength is significantly increased, becoming the refractory concrete required for work.

Requirements for aggregates and admixtures of aluminate cement refractory concrete

1. Aggregate. Since aluminate cement can be used to formulate refractory concrete with higher working temperatures, aggregates with higher refractoriness, such as bauxite clinker, crushed high alumina bricks, crushed magnesia bricks, and magnesia, need to be used. If the operating temperature exceeds 1500°C, it is best to use chromium-aluminum slag, fused corundum, etc.

2. Admixtures. To improve the high-temperature resistance of refractory concrete, a certain amount of powder with a chemical composition similar to cement is sometimes added when preparing concrete, such as silica powder, corundum powder, high alumina bauxite clinker powder, etc. The fineness of the powder should generally be less than 1μm.

Issues to note during construction of aluminate cement refractory concrete

1. Aluminate cement is generally not mixed with Portland cement, quicklime, and other cement that precipitate Ca(OH)₂ because mixing the two will cause flash solidification and produce highly alkaline calcium aluminate hydrate. , causing the concrete to crack or even damage.

2. When aluminate cement hardens, it releases a large amount of heat, and the heat is concentrated in the early stage. Therefore, water should be provided for curing immediately when the cement hardens. The suitable construction temperature is 15 to 25°C. When the temperature exceeds 25°C, cooling measures should be taken. The curing period No less than 3d.

3. The amount of concrete mixed each time should be controlled to be used up within 20 minutes. The mixing water should be drinking water, and stirring should be continued during this period. Hardened concrete should not be reused with water, otherwise the concrete may not harden.

4. Aluminate cement is generally not used for pouring large volumes of concrete, and the thickness should not exceed 300mm. When used for reinforced concrete, the reinforced concrete protective layer should not be less than 3mm.