What is the role of micronization technology in refractory castables?

      The application of micronized powder technology fills the tiny pores and acts as a lubricant for the refractory castables.

      The addition of micronized powder can fill the void between the aggregate and powder, and it can reduce the amount of water added during the construction. While increasing the bulk density and reducing the porosity of the castable, it can also improve the intrinsic structural strength of the castable and optimize several properties of the castable.

      The micronized powder can form colloidal particles in water, and when dispersant exists, it can prevent the adsorption and coalescence between the particles; the dispersant adsorbed around the particles can increase the fluidity of the refractory castings. The micronized powders added in the refractory castings are: active SiO₂ powder and α-Al₂O₃ powder, SiC powder, high alumina powder, white corundum powder, brown corundum powder, zircon powder and spinel powder, etc.

      SiO₂ micronized powder is hollow spherical with activity, not agglomerated, and good filling property. After it is added to the refractory castable in a reasonable proportion, silanol group is formed on the surface, and it forms a siloxane mesh structure after drying and dehydration, and it is not easy to break when the temperature rises. Due to the existence of OH group on the particles of SiO₂ micropowder, it can coalesce again between SiO₂ after being stressed, and it can also increase the viscosity; SiO₂ micropowder has good thixotropy and cohesiveness.

      When SiO₂ micronized powder coexists with dispersant in refractory castables, Si micronized powder forms colloid in water. Due to the fine and active particles of Si micronized powder, solid phase sintering reaction can occur at medium and high temperature, and it can react with Al₂O₃ in high alumina castables to mullite, which can largely improve the post-fire strength of high alumina low cement refractory castable series.

       α-Al₂O₃ micronized powder is used in industrial alumina calcination. It is characterized by good dispersion, small particle size, easy sintering at high temperatures and small volume effect. α-Al₂O₃ added to refractory castables in reasonable proportions also has a significant effect on construction performance. The addition of α-Al₂O₃ micro-powder to the castable can improve the refractoriness of the castable on the one hand, and the reaction of ceramization and mullitization at high temperature on the other hand, and play a filling role of micro-powder to reduce the porosity of the castable, so that the structural defects in the castable can be reduced and the strength and resistance to slag erosion of the castable can be improved. At the same time, it can also improve the overall performance of the refractory castables.

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