What occurs when moisture trapped in concrete is heated and expands, causing parts of the concrete to shatter?

When moisture trapped in concrete is heated, it can turn into steam and expand. This rapid expansion can create internal pressure within the concrete, leading to the outer layer of the concrete cracking and breaking away. This phenomenon is known as spalling. Spalling commonly occurs in heavy fire conditions when the heat causes the moisture to vaporize quickly, resulting in pieces of concrete chipping off.

This process is crucial to understand in fire scenarios, as it can compromise the structural integrity of buildings and other concrete structures, posing a significant risk to firefighters and anyone involved in the response or recovery efforts. Awareness of spalling helps in assessing the stability of affected structures after exposure to fire.

The other terms associated with the options refer to different processes. Scaling typically refers to the surface layer of concrete flaking away, often due to freeze-thaw cycles or corrosion of reinforcement, and granulation refers to the formation of small granules or particles, not specifically related to concrete behavior under heat. Cavitation involves the formation of vapor cavities in a liquid and is not applicable to this context.