Key Points of Construction Design of Refractory Concrete

1. If construction conditions permit, the water-cement ratio should be reduced as much as possible to reduce water consumption. This is because water in refractory concrete is easily lost at high temperatures, resulting in increased concrete pores and reduced strength.

2. To meet the workability and normal temperature strength, the amount of cementing materials and cement should be reduced as much as possible. This is because the fire resistance of aggregates is generally higher than cementing materials and high-temperature cementing materials soften and deform before aggregates.

3. Adding appropriate admixture materials can improve the fire resistance of concrete, improve workability, and reduce the amount of cement. Commonly used blending materials include clay clinker, clay refractory bricks, alumina clinker, magnesia, chromite, fly ash, finely ground powder of high alumina bricks, and silica powder and corundum powder with high refractory properties.

4. Appropriate gradation of aggregates should be selected to maximize density, and attention should be paid to matching with cementitious materials. The sand rate is controlled at 40% to 60%. The mix ratio design is generally based on the empirical mix ratio and is determined after adjustment through experiments. Refractory concrete is generally not equipped with steel bars because the thermal expansion coefficient of steel bars is very different from that of refractory concrete. High temperatures will cause the concrete to crack and peel, and the steel bars will oxidize, soften, and lose their reinforcing effect. When reinforcement is necessary, special measures should be taken, such as aluminizing the surface of the steel bars to resist oxidation, using shaped steel, or burying cooling water pipes.