How long should castable be allowed to set before it is discarded if not used?

The correct duration for allowing castable material to set before it should be discarded is 30 minutes. This time frame is crucial because castable refractories have a specific working time during which they can be mixed, poured, and shaped before they begin to harden. After approximately 30 minutes, the material may no longer be workable, leading to potential issues such as poor adhesion or incomplete filling if attempts are made to use it beyond this time. Ensuring that castable material is utilized within this time limit helps maintain the quality and integrity of the installation, which is vital for performance in high-temperature applications. Discarding any unused material after this period avoids complications in the application process and ensures the effectiveness of the refractories being installed.