Asphalt and Paving Glossary

47 terms used in asphalt specification, estimating and construction, from AASHTO to wearing course, including the French, Indian, Pakistani and British regional designations.

Jump to: A · B · C · D · E · F · G · H · L · M · N · O · P · R · S · T · W

A

AASHTO

American Association of State Highway and Transportation Officials. Publishes the material and design standards most US state DOTs adopt, including AASHTO M 323 for Superpave mix design.

Aggregate

The crushed stone, gravel and sand that makes up roughly 94–95% of an asphalt mix by weight. Aggregate gradation determines whether a mix is dense-graded, gap-graded or open-graded.

Air voids

The percentage of the compacted mix volume that is air. Target is typically 3–5% for a dense-graded surface course. Too low and the mix ruts; too high and it oxidises and ravels.

Asphalt cement

North American term for the bitumen binder itself, as distinct from the finished mix. Sold by grade, e.g. PG 64-22.

B

BBSG

Béton Bitumineux Semi-Grenu. The standard French dense-graded surface course, usually 0/10 gradation laid 5–7 cm thick, with a density near 2,370 kg/m³.

BBME

Béton Bitumineux à Module Élevé. A French high-modulus surface course using modified binder, used on heavily trafficked routes.

Binder course

The intermediate asphalt lift between the base and the wearing course. Coarser and cheaper than surface mix.

Bitumen

The heavy petroleum residue that binds the aggregate. Called asphalt cement in North America and bitumen almost everywhere else.

Blacktop

Colloquial North American term for asphalt pavement. No technical distinction from asphalt concrete.

C

CBR

California Bearing Ratio. A subgrade strength index. Pavement thickness design is driven directly by the CBR of the soil underneath.

Cold mix

Asphalt mixed with emulsified or cutback binder at ambient temperature. Used for patching and low-volume rural surfacing.

Compaction

Rolling the loose mat to reduce air voids and lock the aggregate skeleton. Loose asphalt loses roughly 15–25% of its volume during compaction.

Cutback asphalt

Bitumen thinned with a petroleum solvent so it can be applied cold. Largely replaced by emulsions for environmental reasons.

D

DBM

Dense Bituminous Macadam. The Indian binder / base course specified under MoRTH Clause 507, density around 2,370 kg/m³.

Dense-graded

A continuous aggregate gradation producing a low-voids, impermeable mix. The default for almost all paving.

E

EME 2

Enrobé à Module Élevé, class 2. A French high-modulus base course that allows a thinner structure for the same load capacity.

Emulsion

Bitumen dispersed in water with a surfactant, allowing cold application. Used for tack coats, prime coats and chip seals.

F

Full-depth

A pavement built entirely of asphalt layers placed directly on the prepared subgrade, with no unbound aggregate base.

G

Gmm

Theoretical maximum specific gravity — the density of the mix with zero air voids. Field density is reported as a percentage of Gmm.

Gmb

Bulk specific gravity of the compacted mix, measured on a core or gyratory specimen.

Grave bitume (GB)

The French asphalt-treated base course, graded GB2 through GB4 by performance class.

H

HMA

Hot Mix Asphalt. Produced at 275–350 °F (135–175 °C), the standard for permanent paving.

HRA

Hot Rolled Asphalt. A traditional UK gap-graded surface course, usually finished with pre-coated chippings rolled into the surface.

L

Lift

One pass of the paver — a single layer of asphalt placed and compacted before the next is laid. Maximum practical lift is about 3× the largest aggregate size.

M

Macadam

Historically, a graded crushed stone pavement. In UK usage, 'macadam' or 'tarmacadam' refers to bitumen-bound aggregate pavement generally.

Marshall

The older mix design method using a 4 in mould and a drop hammer, still used in India, Pakistan and many other markets.

Mill and fill

Removing the top 1.5–2 in of a worn pavement with a milling machine and replacing it with fresh mix. The most common rehabilitation method.

MoRTH

India's Ministry of Road Transport and Highways. Its Specifications for Road and Bridge Works define BC, DBM, BM and premix.

N

NAPA

National Asphalt Pavement Association, the US industry body that publishes the density and construction references most estimators rely on.

NHA

Pakistan's National Highway Authority, whose General Specifications govern bitumen grade and mix design on national routes.

O

OGFC

Open-Graded Friction Course. A thin porous surface layer, roughly 115 lb/ft³, laid to reduce spray and noise.

P

Penetration grade

The older binder classification (60/70, 80/100) still standard across South Asia, the Middle East and parts of Europe.

PG grade

Performance Grade binder classification, e.g. PG 64-22, giving the high and low pavement design temperatures in °C.

Premix

Indian term for a plant-mixed bituminous material, most often the open-graded premix carpet used as a thin surfacing.

Prime coat

A low-viscosity bitumen sprayed onto an unbound aggregate base to seal it and bond the first asphalt lift.

R

RAP

Reclaimed Asphalt Pavement. Milled-up old pavement, reused either as millings in its own right or blended back into new mix at 15–30%.

Ravelling

Progressive loss of aggregate from the surface, usually caused by binder oxidation or inadequate compaction.

Rut

A longitudinal depression in the wheel path caused by permanent deformation of the mix or the layers beneath it.

S

Sealcoat

A coal tar or asphalt emulsion coating applied over an existing surface to slow oxidation. Cosmetic and protective, not structural.

SMA

Stone Matrix Asphalt. A gap-graded, stone-on-stone mix with high binder content and fibre, used where rutting resistance matters.

Subgrade

The prepared native soil the whole pavement structure sits on.

Superpave

The US performance-based mix design system introduced by SHRP, using the gyratory compactor and PG binders.

T

Tack coat

A thin bitumen emulsion sprayed between asphalt lifts so they bond into a single structural slab.

Tarmac

British colloquial term for asphalt pavement, from tarmacadam. Also a registered company name in the UK.

Tonne vs ton

A metric tonne is 1,000 kg (2,204.6 lb). A US short ton is 2,000 lb (907.2 kg). A tonne is about 10% heavier.

W

WMA

Warm Mix Asphalt. Produced 30–100 °F cooler than HMA using additives or foaming, cutting fuel use and extending the paving season.

Wearing course

The top asphalt layer, in direct contact with traffic.

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Last reviewed: 28 August 2026 Next review: November 2026 Reviewed by: AsphaltCalculatorPrice Editorial Team