How many days must castable refractory be air-cured?

The correct answer is two days, as castable refractories require a specific period to cure effectively. During the air-curing phase, moisture within the refractory material needs to evaporate gradually to avoid creating internal stresses that could lead to cracking. Allowing it to cure for two days allows sufficient time for the moisture to escape while minimizing the risk of damage.

In practice, this two-day air-curing period helps ensure the integrity and performance of the refractory material once it is subjected to high temperatures in its intended application. This step is critical to achieving the desired properties of the refractory, such as strength and insulation capabilities, which are essential for optimal performance in various industrial applications.

Options suggesting shorter or longer curing times do not account for the necessary evaporation process required for effective curing, resulting in compromised material quality and performance. Proper adherence to the two-day air-curing requirement is essential for achieving the best results when working with castable refractories.