What happens when moisture trapped in concrete is heated and expands, causing parts of the concrete to break away?

When moisture trapped in concrete is heated, it expands and creates internal pressure. This pressure can cause parts of the concrete surface to break away, a phenomenon known as spalling. Spalling specifically refers to the flaking or breaking off of the outer layer of concrete, which can occur due to factors such as thermal expansion from heating, freeze-thaw cycles, or chemical reactions within the concrete.

In contrast, cracking typically involves visible fractures in the concrete surface without the material actually breaking off. Erosion refers to the gradual wearing away of material due to mechanical action or other environmental factors, while warping involves a distortion or bending of the concrete rather than the physical breaking away of pieces. Thus, spalling most accurately describes the condition resulting from heated moisture expanding within the concrete matrix.