How long must air-setting phosphate bonded castable refractories be air cured?

Air-setting phosphate bonded castable refractories typically need to be air cured for a specific duration to ensure proper strength development and performance. The correct answer of 24 hours reflects the necessary time for the material to achieve sufficient initial set and strength, allowing for optimal bonding and stability before being subjected to any further processing or thermal cycling.

This time frame is critical as it permits the chemical reactions within the binder to progress adequately, which is essential for the refractory's performance in high-temperature applications. If the curing is not allowed to complete as specified, the effectiveness of the refractories could be compromised, potentially leading to issues such as cracking or insufficient mechanical strength during use.

In contrast, the other durations mentioned would either be too short or exceed the optimal curing timeframe that has been extensively studied and outlined in industry guidelines. Understanding these curing times is crucial for refractory personnel to ensure reliability and longevity of the refractory materials in service.