Alligation or Alligated: Interconnected cracks forming a series of small blocks resembling an alligator’s skin or chicken wire, and caused by excessive deflection of the surface over unstable subgrade or lower course of the pavement. Also known as spider-web cracks.

Compaction: The process by which the bulk density of an aggregate of matter, such as stone or sand, is increased by driving out air. For any soil, for a given amount of compactive effort, the density obtained depends on the moisture content. 

Crack: An approximately vertical random cleavage of the pavement caused by traffic loading, thermal stresses and/or aging of the binder.

Crack Filler: A material that is placed in a pavement crack or joint to fill but not necessarily seal the void created by the crack or joint.

Crack Sealant: A material that has adhesive and cohesive properties to seal cracks, joints or other narrow openings (less than 1 ½” wide) in pavements against the entrance or passage of water or other debris.

Hairline Cracking: Barely visible cracks in random pattern in an exposed concrete surface which do not extend to the full depth or thickness of the concrete, and which are due primarily to drying shrinkage.

Overlay: A hot-mix asphalt overlay constructed for the purpose of increasing the structural value and ride quality of the pavement system.  Also called resurfacing.

Pothole: Bowl-shaped openings in the pavement resulting from localized disintegration.

Raveling: The gradual roughening of the surface texture. As the fine particles “wash” away it leaves the pavement with course rock on the surface and a much rougher texture than when asphalt first laid.

Reflective Cracking: Cracks in asphalt overlays that reflect the crack pattern in the pavement structure below it. Also known as mirrored cracking.

Tack Coat: Asphalt oil, usually emulsion type, applied to existing pavement during repairs or overlay paving to create a bond between the old and new asphalt.