Where does alligator cracking collide?

In pavement engineering, alligator cracking is a network of interconnected cracks that develops in the wheel path of a flexible pavement under repeated traffic loading, breaking the surface into many small angular pieces that resemble an alligator's hide. Howard and James's study of bottom-up fatigue cracking shows how repeated tensile strain at the underside of the asphalt layer initiates cracks that propagate to the surface as the layer fatigues. The referent is a structural load-fatigue failure of the bound layer, named for its pattern, and it is a different defect in a different material from the paint-film failure that shares the name.[1]

Unit

Cracked area as a share of the wheel-path area, with a severity rating

Recovery means

Signals structural fatigue; corrected by patching or full-depth repair and overlay, not by surface sealing alone

Measured by

Rated by surveying the extent (percent of wheel-path area) and severity (crack width, spalling, pumping) of the interconnected crack network

In coatings technology, alligatoring is a paint-film defect in which the dried coating splits into a pattern of broad island segments separated by fissures, exposing the layer beneath and recalling reptile skin. Weldon's Failure Analysis of Paints and Coatings attributes it to differential shrinkage and stress between a hard, brittle topcoat and a softer or still-moving layer below, often worsened by thick films, incompatible coats, or weathering. The referent is a cohesive failure of a thin organic film driven by internal stress, unrelated to the traffic-fatigue failure of a pavement layer beyond the shared visual name.[2]

Unit

Extent and coarseness of the island-and-fissure pattern over the film area

Recovery means

Not applicable

Measured by

Assessed visually and by microscopy against standard defect descriptions, relating pattern scale to film thickness and inter-coat stress