The higher the alumina content, the higher the fire resistance; The content of calcium oxide increases with the decrease of aluminum oxide content. Adding aluminous cement as a binder in refractory castables can significantly shorten the demolding time within 24 hours. However, the addition of the aluminous cement can also affect the flowability of refractory castables and the process of construction and demolding, so improper use may have adverse effects on construction.
The process of it can be divided into three stages: dissolution, nucleation, and precipitation. For example, the CA-50  is commonly used in the production of medium and low-grade refractory castables. However, it should be noted that CA-50 cement has the lowest strength at 800 ℃. Therefore, when the furnace lining is used at a temperature of exactly 800 ℃, selecting refractory castables becomes particularly difficult because the low temperature actually limits the use of ordinary refractory castables. At this point, low cement castables become a suitable choice, with low calcium content, excellent strength performance at medium temperatures, and good strength for later use.
In contrast, the high aluminous cement of CA-70 and CA-80 has a higher aluminum content and a relatively smaller addition ratio. They are suitable for low cement refractory castables, which not only enhance the strength of refractory castables, but also further reduce the calcium content and improve the performance of medium temperature strength.
In summary, when adding the high aluminous cement to refractory castables, it is necessary to comprehensively consider the bonding situation and operating temperature. According to specific requirements, choose to add CA-50 or CA-70 and CA-80 to ensure the optimal performance of refractory castables.