Low cement castables are a commonly used refractory material, and activated alumina powder has an important effect on its performance:
1. Improve strength: Activated alumina powder has fine particles and a large specific surface area, which can fill the pores in the castable and make its structure denser. During the coagulation and hardening process of the castable, the powder can also react with other components to generate new mineral phases, thereby improving the strength of the castable. For example, adding an appropriate amount of activated alumina powder to a corundum low-cement castable can increase its room temperature compressive strength by 20% - 30%.
2. Improve fluidity: An appropriate amount of activated alumina powder can play a role similar to a ball in the low cement castable, reducing the friction resistance between particles, thereby improving the fluidity of the castable. This makes it easier for the castable to fill complex molds and structures during construction, ensuring construction quality. However, if too much powder is added, the agglomeration between particles will be aggravated, which will reduce the fluidity of the castable.
3. Enhance thermal shock resistance: The addition of activated alumina powder can refine the grain structure of the castable and reduce the presence of large crystals. When the castable is subjected to temperature changes, the fine grains can better adapt to the changes in thermal stress, reduce the possibility of crack generation and expansion, and thus improve the thermal shock resistance of the castable. For example, after adding activated alumina powder to some low-cement castables used for heating furnace linings, their service life under rapid cooling and heating conditions is significantly extended.
4. Reduce porosity: Activated alumina powder can fill the pores between low cement castable particles, reduce the number and size of pores, and thus reduce the porosity of the castable. Lower porosity can improve the strength, corrosion resistance and wear resistance of the castable. For example, after adding activated alumina powder to magnesium low-cement castables, its porosity can be reduced by 5% - 10%.
The addition of activated alumina powder can significantly improve the performance of low-cement castables, especially in terms of high temperature resistance, strength, corrosion resistance, etc. When designing the formula, it is necessary to pay attention to the control of the amount of addition to ensure the optimization of performance, while avoiding construction difficulties or excessive material costs caused by excessive addition.
If there are specific application requirements or test conditions, further analysis can be conducted on how to adjust the formula to achieve optimal performance.
