What should cracked boutet base bricks be repaired with before use?

Cracked boutet base bricks should be repaired with refractory paste before use because this material is specifically designed to withstand the high temperatures encountered in thermite welding and other thermal processes. Refractory paste can effectively fill in the cracks, providing a strong bond that maintains the integrity of the bricks under thermal stress. It is formulated to endure the extreme heat and abrasive conditions that are typical in welding applications, ensuring that the bricks remain functional and safe for use during the welding process.

Using other materials, such as adhesive, cement, or welding filler, would not be appropriate in this context. Adhesive might not have the necessary heat resistance, and cement can crack or break under high temperatures. Welding filler is designed for joining metals rather than repairing ceramic materials like boutet base bricks. Therefore, refractory paste is the most suitable option for ensuring that repaired bricks can safely and effectively operate in high-temperature environments.