spalled

Spalled is the past participle and adjective related to spalling, a surface failure mechanism in which layers or fragments peel, flake, or detach from a material under stress. Spalling can result from a combination of tensile stresses, thermal shocks, impacts, or chemical attack, and it is observed across a range of materials and applications.

In civil engineering and construction, spalled concrete refers to surface fragments peeling away from a concrete element, sometimes exposing coarse aggregate. Common causes include fire damage and rapid heating or cooling, freeze–thaw cycles, corrosion of reinforcing steel, moisture-related deterioration, improper curing, and impact or blast loading. Spalling can reduce durability and increase permeability, so repair typically involves removing loose material, patching, and addressing underlying causes such as temperature control, moisture management, or protective coatings.

In geology and materials science, spalled rock, ice, or metal describes surface flakes peeled off by unloading, thermal stress, or explosive or dynamic loading. In metals, spalling can occur during severe thermal cycling or high‑strain shocks, producing flaky fragments along surface regions.

In physics and engineering contexts, spallation refers to a related process where high‑energy particles or shocks eject fragments or nucleons from a material, producing spalled products. The term is used in studies of blast effects, meteoritic or nuclear interactions, and accelerator-target experiments. Overall, spalled describes a common mode of surface damage driven by stress concentrations, environmental conditions, or energetic impacts.