Glossary of Terms

Absolute Pressure
Pressure measured against the degree of vacuum. Absolute pressure is zero in a complete vacuum and increases as pressure is increased.

Changes in the properties of asphalt binder which happen over time, due to environment or the construction process.

A particulate material – including sand, gravel, and stone – combined with asphalt to strengthen and reinforce asphalt concrete.

Asphalt Binder
A modified or unmodified asphalt used as the binding material in asphalt concrete.

Asphalt Cement
A cementitious material consisting primarily of bitumen. It may be found in natural asphalt deposits or produced by petroleum processing.

A viscous, sticky liquid or semi-solid found in crude petroleum.

Cold In-Place Recycling (CIR)
A process where areas of significantly cracked or deformed asphalt pavement are milled, mixed with an emulsion and additives, and placed over the existing surface.

Crumb Rubber
Bits of recycled rubber from used tires. Sometimes used as a modifier for asphalt binder or aggregate.

Cutback Asphalt
Liquid asphalt made by mixing asphalt cement with a petroleum solvent.

Emulsified Asphalt
A suspension of asphalt globules in water, with an emulsifying agent to prevent the globules from coalescing.

Fatigue Cracking
The cracking caused by pavement being stressed to its limit by repeated load application.

Hot In-Place Recycling
A method of rehabilitating pavement where the existing surface is softened with heat, removed or scarified, and mixed with soft asphalt, recycling agents, and additional aggregate. The new mixture is then placed and compacted on the roadway.

Mass Change
The change in mass that occurs during a Rolling Thin Film Oven (RTFO) test. This term replaces the less accurate “mass loss” which was previously used for this test.

Penetration Grade
In the penetration grading system, asphalt binders are categorized into classes (from softest to hardest) based on their penetration value at a specific temperature.

Performance Grade
A method of testing asphalt binder which tests properties of the binder in conditions that simulate the environment and conditions it will be used in.

Polymer Modified Asphalt Binder
Asphalt binder modified by polymers, which are substances made of small molecules chemically connected to form a long molecular chain.

Rolling Thin Film Oven (RTFO)
An apparatus that simulates the mixing and compaction of asphalt concrete. It is used to test asphalt binder for hardening and mass change.

A device that measures how a liquid or suspension flows against applied force.

Permanent pavement deformation caused by repeated traffic loads, which cause ruts in the wheel path.

Stone Mastic Asphalt (SMA)
A durable, deformation-resistant, gap-graded hot mix asphalt. It has high coarse aggregate content which forms a stone skeleton which is filled with binder, fibres, and filler to make it strong and durable.

Superpave (Superior Performing Asphalt Pavement) is a system of asphalt binder specifications, mix design, and analysis developed by the Strategic Highway Research Program. The system factors in asphalt performance characteristics and environmental conditions to design asphalt mixes for optimum performance.

Substance that possesses both viscous and elastic qualities.

The measure of resistance of a fluid deformed by stress. A highly viscous substance will appear thick and will not flow easily.