Asphalt & Paving Industry Glossary

Comprehensive Terminology Guide

This glossary defines key terms used in asphalt paving, materials, construction techniques, and project planning. Definitions are based on ASTM, AASHTO, and NAPA standards for accuracy.

A

Aggregate

Crushed stone, sand, gravel, or recycled material mixed with asphalt binder to create pavement. Types include:

• Coarse Aggregate: Particles larger than 4.75 mm (used for structural strength).
• Fine Aggregate: Particles smaller than 4.75 mm (fills voids).

Anti-Stripping Agent

Chemical additives (e.g., lime, amines) mixed into the asphalt binder to improve adhesion between binder and aggregate and reduce moisture-induced stripping.

Asphalt Binder

The sticky, petroleum-based glue that holds aggregates together. Grades include:

• PG (Performance Grade): Rated for temperature resistance (e.g., PG 64-22).
• Penetration Grade: Measures hardness (e.g., 60/70).

Asphalt Millings

Recycled asphalt pavement (RAP) from old roads, ground into gravel for reuse.

B

Base Course

The foundational layer beneath asphalt, typically made of crushed stone or stabilized soil.

Binder Course

Intermediate asphalt layer between the base and surface course for added strength.

Bleeding

Excess asphalt binder rising to the surface, creating a slick, shiny layer.

C

Cantabro Abrasion Test

A laboratory test that evaluates the resistance of open-graded mixes to raveling by measuring aggregate loss after tumbling.

Compaction

Process of compressing asphalt layers to 92–98% density for durability. Measured with:

• Nuclear Density Gauges
• Sand Cone Tests

Crown

The slight elevation (1–2%) along a pavement’s centerline for water drainage.

D

Density (Asphalt)

Weight per unit volume (typically 145 lb/ft³ for hot-mix asphalt).

Drainage Layer

Permeable material (e.g., geotextile fabric) beneath pavement to prevent water damage.

Dust-to-Asphalt Ratio (D/A)

The ratio of the fine aggregate (dust) to binder; too much dust leads to stiff mixes, too little causes flushing.

E

Edge Joint

The seam between new and existing pavement, often reinforced with tack coat.

Emulsion

A mixture of asphalt binder, water, and emulsifying agents for cold applications.

Equilibrium Temperature

The temperature at which asphalt mix reaches uniform temperature throughout before compaction (usually 290–330°F for HMA).

F

Fog Seal

A light spray of diluted asphalt emulsion to rejuvenate old pavement.

Friction Course

A rough surface layer (e.g., open-graded asphalt) to improve tire grip.

G

Grade (Slope)

Pavement’s angle for drainage, usually 1–2% (1/8″ per foot).

Geogrid

Plastic or fiberglass grid used to stabilize weak subgrades.

H

Hot-Mix Asphalt (HMA)

Asphalt produced at 300–350°F for high-durability paving.

HMA Types:

• Dense-Graded: Standard mix for roads.
• Stone Matrix (SMA): High-strength for heavy traffic.

Hydrated Lime

Finely ground lime is added to HMA further enhances moisture damage resistance and stiffness.

I

Impermeability

Asphalt’s resistance to water infiltration (measured in cm/sec).

IRI (International Roughness Index)

A scale (0–20) for pavement smoothness.

J-K

Joint Sealant

Flexible material (e.g., silicone) to prevent water seepage at pavement joints.

JMF (Job Mix Formula)

The exact proportions of aggregates, binder, and additives approved for a paving project.

Kerb (Curb)

The raised edge along pavements for drainage control.

L

Leveling Course

A thin asphalt layer (often <1″) placed to correct minor surface irregularities before the binder or surface course.

Lift

A single layer of asphalt during paving (typical thickness: 2–4″).

Longitudinal Joint

The seam between two paved lanes.

M

Mat

The uncompacted asphalt layer after laying by the paver.

Milling

Grinding off old asphalt surfaces for recycling or repaving.

N-O

NAPA (National Asphalt Pavement Association)

U.S. industry group setting asphalt standards.

Open-Graded Mix

Asphalt with high air voids (15–20%) for water drainage.

P

Pothole

A pavement failure caused by water infiltration and traffic loads.

Polished Aggregate

Smooth, worn aggregate particles that reduce skid resistance.

Q-R

Quality Control (QC) Testing

Lab tests for asphalt mix consistency (e.g., Marshall Stability Test).

Rutting

Permanent deformation in wheel paths from heavy loads.

S

Segregation

Uneven aggregate distribution in asphalt, weakening pavement.

Seal Coat

A surface treatment (e.g., chip seal, slurry seal) applied to extend pavement life by sealing small cracks and restoring friction.

Stabilization

The process of mixing soil or aggregate with cementitious or chemical additives to improve strength and reduce plasticity.

Subgrade

The natural soil or improved foundation below pavement layers.

T

Tack Coat

A thin asphalt emulsion layer between pavement lifts for bonding.

Tonnage Calculation

Formula:
Tons = (Area (sq ft) × Depth (ft) × Density (lb/ft³)) ÷ 2000

U-Z

VMA (Voids in Mineral Aggregate)

Air gaps between coated aggregates (ideal: 14–18%).

Wearing Course

The top asphalt layer designed for traffic and weather resistance.