Structure Of Refractory Castables

Refractory castables consist of three parts: binder, aggregate, and admixture, sometimes with the addition of accelerators.
Refractory aggregate is the main body of refractory concrete, and various refractory materials (such as clay, high alumina, silica, magnesia, etc.) can be used as refractory aggregates after calcination, or after various waste bricks are crushed to a certain extent. The particle size of aggregates has a significant impact on the quality of products, so in addition to certain limitations on the size of aggregate particles, there are also certain proportion requirements in terms of quantity. Refractory aggregates are equivalent to crushed stones and sand used in ordinary building concrete. In the batching of refractory concrete, aggregates generally account for 70% to 80%. Among them, coarse aggregate (5-20mm) accounts for 35% to 45% of the ingredients; Fine aggregate (0.15-5mm) accounts for 30% to 35%.
The bonding material plays a role in bonding and hardening, giving the product a certain strength. Common Portland cement, alumina cement (high sales cement), magnesium cement, sodium silicate, phosphoric acid, etc. can be used as binders. To ensure that the concrete has sufficient fire resistance (the more the amount of binder used as a flux at high temperatures, the lower the fire resistance of the concrete), and to reduce volume shrinkage during use, the amount of binder used should be as small as possible, generally 10% to 25%, and it is hoped that the binder and bone material cannot generate a large amount of low melting material.
Some refractory concrete (such as phosphate refractory concrete) must also add a small amount of coagulant in the mix to accelerate the hardening and solidification of the concrete.
In order to improve the performance of refractory concrete, such as increasing its strength during heating and reducing volume shrinkage, 10% to 25% of admixtures are often added. The raw material of the admixture is the same as the aggregate, which is finely ground refractory clinker powder, with 70% to 80% of the fineness below 0.088mm.