Introduction and Application of Refractory Aggregate and Powder
In amorphous refractories, the amount of aggregate is generally 60% – 73%, which plays the role of skeleton and can significantly affect its performance;
The amount of refractory powder is 15% – 40%, which can fill the gap of aggregate and improve the workability of construction. Some refractory powders, such as clay and ultra-fine powder, are also good binders.
The ideal particle gradation is that the gap caused by coarse aggregate is just filled by fine aggregate, and the gap between them is filled by refractory powder without deficiency or surplus, so as to achieve the maximum bulk density, so as to obtain the best performance.
Refractory Aggregate
Refractory aggregate is divided into coarse aggregate and fine aggregate. Generally, the particle size greater than 5mm is called coarse aggregate; 5mm and below to 0.09mm is called fine aggregate.
The critical particle size of aggregate is determined according to the thickness of lining, generally 10mm or 15mm. 20mm or 25mm particles can be used for large structures such as blast furnace foundation pier and ladle castable.
In addition, the critical particle size of refractory aggregate is also different due to different construction and manufacturing methods. See Table 1-1 for details. At present, the critical particle size of refractory aggregate tends to increase.
It should be pointed out that when preparing amorphous refractory materials, the particle gradation of refractory aggregate shall meet the technical requirements in the table. Even if unified materials are used, they shall be screened and inspected to meet their requirements before they can be used.
Refractory Powder
Refractory powder is the matrix material of unshaped refractory materials. Its grade shall be higher than or equivalent to refractory aggregate. The fineness shall be less than 0.09mm or 0.088mm, and the content of powder shall be greater than 85%. For ultra-fine powder, the powder below 5 microns should account for more than 80%.
Refractory Aggregate and Powder
Among modern unshaped refractories, corundum, synthetic mullite, spinel, alumina and other high-grade materials are used to make refractory aggregate and powder. Some iron will be brought in during crushing. In order to ensure the product quality, iron removal treatment should be carried out. Raw materials for refractory aggregates and powders must be subject to quality inspection and can be processed into refractory aggregates and powders only after they are qualified.