What does the term spalling refer to in relation to concrete?

The term spalling in relation to concrete specifically refers to the phenomenon where parts of the concrete break away, typically due to the presence of trapped moisture. When moisture seeps into the concrete and freezes, it expands and can cause the surface of the concrete to flake or break off. This is especially common in climates with freeze-thaw cycles, where water enters the concrete, freezes, and then expands, ultimately causing pieces of the concrete to pop off.

Understanding spalling is crucial in assessing the durability and maintenance needs of concrete structures, as it can lead to further degradation if not addressed. This process is distinct from other issues like cracking from temperature changes or loss of structural integrity, which do not necessarily involve the removal of surface layers in the same way that spalling does.