Asphalt & Paving Glossary

Aggregate

Crushed stone, gravel, and sand used in asphalt mix and base layers. The size and quality of aggregate affect the strength and durability of the finished pavement.

Alligator Cracking

A pattern of interconnected cracks resembling reptile skin. It is a sign that the base beneath the asphalt has failed and usually indicates the pavement needs replacement or reclamation rather than surface repair.

See also: Base Course, Full Depth Reclamation

Asphalt

A paving material made of aggregate bound together with asphalt binder, a petroleum product. It is durable, flexible, and widely used for driveways, parking lots, and roads.

Base Course

The compacted layer of aggregate beneath the asphalt that carries traffic loads and provides structural support. A properly built base is the single biggest factor in pavement lifespan.

See also: Subgrade, Compaction

Binder Course

A structural layer of asphalt placed below the surface course. It uses larger aggregate and adds strength, often used on driveways and parking lots that carry heavier loads.

Compaction

The process of rolling asphalt and base layers to remove air voids and reach a specified density. Proper compaction is essential for strength, smoothness, and longevity.

Crack Sealing

Filling working cracks with a flexible, often rubberized sealant to keep water out of the base. Timely crack sealing is one of the most cost-effective ways to extend pavement life.

Crown

A slight rise along the centerline of a driveway or road so water sheds to the edges rather than pooling on the surface.

Full Depth Reclamation

A rehabilitation method that pulverizes the existing asphalt and base together, then recompacts the blended material into a new base for fresh paving. It rebuilds a failed pavement structure by recycling materials in place.

See also: Base Course, Alligator Cracking

Grading

Shaping the ground or pavement to establish proper slope and elevation, ensuring water drains away from structures and off the surface.

Hot-Mix Asphalt (HMA)

Asphalt produced and placed at high temperature. It is the standard material for durable driveways, parking lots, and roads, and must be compacted while still hot.

Milling

Grinding off a controlled depth of existing asphalt, usually to prepare a surface for an overlay without raising the overall grade. The removed material can be recycled.

See also: Overlay, Reclaimed Asphalt Pavement (RAP)

Overlay

A new layer of asphalt placed over an existing pavement. An overlay restores the surface and works well when the underlying base is still structurally sound.

See also: Milling, Binder Course

Pothole

A bowl-shaped hole in pavement formed when water reaches the base, freezes and thaws, weakens support, and traffic breaks the surface apart.

Reclaimed Asphalt Pavement (RAP)

Asphalt removed by milling or excavation that can be recycled into new asphalt mix or reused as base material, making asphalt one of the most recycled construction materials.

Sealcoating

A protective coating applied to asphalt that shields it from water, sunlight, and automotive fluids. Sealcoating slows oxidation and cracking but does not repair existing damage.

Subgrade

The native soil beneath the base course. A stable subgrade is the foundation everything else is built on; soft or wet subgrade must be addressed before paving.

See also: Base Course

Tack Coat

A thin layer of asphalt emulsion sprayed between pavement layers to bond them together so they perform as a single unit.