Which material is prone to spalling under fire conditions?

Concrete is indeed prone to spalling under fire conditions due to its composition and properties. When exposed to high temperatures, the moisture trapped within the concrete can vaporize rapidly. This sudden expansion of steam creates immense internal pressure, leading to the breaking away of the concrete surface, known as spalling. The effects of fire can cause not only aesthetic damage but also compromise the structural integrity of concrete elements in buildings. This behavior is particularly problematic in firefighting scenarios, as it can lead to the failure of load-bearing components, creating additional hazards during fire suppression efforts.

In contrast, wood, while it can burn, does not exhibit spalling. Steel can lose its strength and structural integrity at high temperatures but does not typically spall. Brick, while it may crack or become weakened with extreme heat, also doesn't spall in the manner that concrete does. Hence, concrete is the material most specifically associated with spalling under fire conditions.