Refractory castable is premixed combinations of refractory aggregates, matrix components or modifiers, bonding agents, and admixtures. It is classified in several ways. It is based on chemistries which separates the refractory castable based on alumina and alumino-silicate aggregates such as magnesite and dolomite.
Refractory aggregates constitute the basic skeleton of castable, and it is accounted for the largest amount of the formulation. Aggregates size can range from 10 mm to 300 mm. Aggregates are sized and proportioned for getting desired packing and particle distribution. Varieties of refractory aggregates is workable. Castable is formulated based on one or combined aggregates to realize the desired chemistry, mineralogy, and physical properties.
The bonding agents used for refractory castables are varieties, including alumino-silicate castable. Calcium aluminium cement is still the main bonding agent for castable.
Specialized castables have been developed for more than 20 years, by using non cement bonds such like hydratable alumina, clay, silica and alumina gels, and chemical bonds such like mono aluminum phosphate, phosphoric acid and alkali silicates. Basic castables rely on chemical or organic bonds, the most common types are alkali silicates, sodium phosphates, mineral or organic acids, and resins etc.