- Time:Sep 15, 2023
Alkaline refractory castables typically contain calcium aluminate cement (CAC) as a binder, which undergoes hydration reactions when mixed with water. The hydration reaction of CAC in alkaline refractory castables can be described as follows:
1. Initial dissolution: When water is added to the castable mixture, it reacts with the CAC, causing the cement particles to dissolve. This initial dissolution releases calcium ions (Ca2+) and aluminum ions (Al3+) into the solution.
2. Nucleation and precipitation: As the dissolved calcium and aluminum ions come into contact with each other and with other components present in the castable mixture (such as refractory aggregates), nucleation occurs. Small solid particles begin to form through the precipitation of hydrates.
3. Hydration and gel formation: The formed solid particles continue to grow through the process of hydration. The calcium and aluminum ions react with water molecules, forming various hydrates, such as calcium aluminate hydrates (CAH) and aluminum hydroxides (Al(OH)3). These hydrates contribute to the development of a gel-like structure within the castable.
4. Setting and hardening: As the hydration progresses, the gel-like structure begins to set and harden, providing strength and integrity to the castable. This process involves the formation of interlocking crystals and the binding of refractory aggregates, resulting in a solid monolithic structure.
The hydration reaction of alkaline refractory castables is vital for the development of strength and integrity within the material. The rate and extent of hydration depend on factors such as the type and quantity of CAC used, water-to-cement ratio, curing conditions, and temperature. Proper control of these factors is crucial to ensure optimal hydration and desired properties in the final castable product.
