The strength improvement of castable after baking is an important link in the application of refractories. The following are several ways to improve the strength of castable after baking:

I. Optimizing cement content

The research shows that the cement content has a significant influence on the strength of castable. Properly increasing cement content can improve the strength of castable, especially after calcination at medium temperature (such as 800℃). This is because the hydration products of cement can still give the castable a certain strength after dehydration and decomposition at high temperature. However, if the cement content is too high, it may lead to an increase in porosity and a decrease in strength, so it is necessary to control the amount of cement reasonably.

II. Adding α-ALO fine powder

Adding α-ALO fine powder into aluminate refractory castable can produce expansion effect in the middle temperature region (800-1000℃), and compensate the strength decrease caused by volume shrinkage of castable. This method can not only improve the medium temperature strength, but also improve the high temperature performance of castable.

III. Use of Sintering Agent

Adding sintering agent (such as soft clay) into castable can promote the sintering of castable at lower temperature, improve its microstructure and thus improve its medium temperature strength. The addition of sintering agent is generally controlled at 3%-6%.

IV: Add water reducing agent

Although the water reducing agent can't directly change the decline law of the medium-temperature strength, the internal structure of the castable can be improved by reducing the construction water consumption, thus indirectly improving the strength after baking.

V. Adjusting the composition of the matrix

Optimizing the chemical composition of castable matrix to make it close to that of mullite (3Al₂O₃·2SiO₂) can produce micro-expansion at high temperature, and improve the thermal shock resistance and high temperature strength.

VI. Adding expansion agent

Adding expansion agent (such as kyanite, Shi Ying, etc.) can produce volume micro-expansion at high temperature, which counteracts the shrinkage of the material, thus improving the thermal shock resistance and high temperature strength.

VII. Controlling the baking process

Reasonable baking process is very important to improve the strength of castable. During the baking process, the temperature should be avoided from changing too fast, especially in the range of 150℃-250℃, because the crystallization water in the castable will volatilize at this time, which will easily lead to excessive internal steam pressure and burst. Adding explosion-proof fiber (such as polypropylene fiber) can effectively solve this problem.

VIII. Use of new binders

Using a new binder (such as SEK Z) instead of traditional cement can improve the high temperature strength and erosion resistance of castable and realize rapid baking.

Through the above method, the strength of the castable after baking can be effectively improved, thus improving its service life and reliability in high temperature environment.