What are the effects of aggregates and cement on mullite castables
The Influence of Aggregates and Cement on Mullite Castable
1、 Advantages of Mullite Castable
Mullite castable is a refractory castable made from high-quality porous mullite aggregate, mixed with fine powder and additives. It can be used as a working lining in direct contact with flames, achieving high temperature and energy conservation; The unit weight is light, the structural weight is reduced by 40-60%, and the hidden danger of broken bricks hanging on the furnace top is eliminated; Low thermal conductivity, porous mullite aggregate ingredient, low thermal conductivity, and good insulation performance; It can quickly dry the furnace and shorten the drying period.
2、 The Influence of Aggregates and Cement on Mullite Castable
1. Cement
Because mullite castable is used in the high-temperature part of the heating furnace at a temperature of about 1350 degrees, pure calcium aluminate castable with excellent performance should be selected, and its alumina content should be greater than 70%. If the impurities in the cement are high, it is easy to produce low solubility substances with the castable at high temperatures, which will affect the high-temperature use of the castable. The addition amount should be controlled at 5% -10%. If the addition amount is too large, it will affect the medium temperature strength of the castable, and at high temperatures, it will have an adverse impact on the high-temperature strength and peeling resistance of the mullite castable.
2. Mullite aggregate
Mullite aggregates, as the main component of mullite castables, have a significant impact on the performance indicators of mullite castables, so the selection of aggregates is particularly crucial. Firstly, legitimate and reputable manufacturers should be selected for procurement. Secondly, due to differences in the inspection methods for the bulk density and compressive strength of mullite aggregates, it is not necessary to only test the indicators of the aggregates. Further testing should be conducted on the indicators of the mullite castables produced from this type of aggregate, which is very necessary for judging the quality of raw materials. Properly increasing the critical particle size of the aggregate is beneficial for enhancing the compressive strength of the castable, but if the critical particle size is too large, it will have adverse effects on the construction performance of the material.