Aging or embrittlement occurs during the mixing and laydown process and during the service life of the asphalt pavement. The asphalt binder displays large increases in stiffness due to oxidation and weight loss in the binder.

Asphalt Binder

A dark brown to black cementitious material in which the predominating constituents are bitumens which occur in nature or are obtained in petroleum processing. In varying proportions, asphalt is a constituent of most crude petroleums.

Crumb Rubber Modifier

A general term for scrap tire rubber that is reduced in size and is used as modifier in asphalt paving materials.


This is the largest and most common class of materials used to modify asphalt. Included in this group are SBR & Natural Latex, Styrene/Butadiene block and di-block copolymers, polychloroprene, reactive ethylene terpolymers, and polybutadiene.

High Temperature Permanent Deformation (Rutting)

Rutting is caused by the accumulated plastic deformation (flow) in the asphalt mixture with repeated applications of loads at upper service pavement temperatures. Modifiers can stiffen the binder and provide a more elastic material.

Hot Mix Asphalt (HMA)

This is the final product produced at an HMA facility which is a mixture of asphalt cement and aggregates, up to the maximum proportions listed above.

Life Cycle Cost Analysis (LCCA)

The process by which the total cost of a pavement over its lifetime is used to define various pavement maintenance and rehabilitation techniques.

Load Associated Fatigue Cracking

Load-Associated fatigue cracking is caused by the continuous application of loads over a period of time.

Low Temperature Thermal Cracking

Thermal shrinkage cracking results from either a single thermal cycle where the temperature (Single Event Thermal Cracking) or from thermal cycling above the critical low temperature (Thermal Fatigue).

Modified Asphalt

A modified asphalt cement or binder has one or more additives that have been physically and/or chemically blended to improve overall durability and in-service pavement performance.


These materials are plastic in nature and include Polyethylene, Polypropylene, Ethylene Vinyl Acetate (EVA) and Attactic Polypropylene (APP & APAO)


A polymer is a large molecule which is made up of many small chemical units called “monomers”. Typically monomers used to make up polymers used in asphalt modification are styrene and butadiene

Reactive Additives

Elastomers and Plastomers can be chemically reacted with asphalt. Several systems involving sulfur and other chemical additives can be found in this category. These systems can often enhance polymer performance and economics.

SBR Latex

SBR (Styrene-Butadiene Rubber) is a random copolymer polymerized using an emulsion polymerization process. The final form of this product is a latex which consist of a polymer in water.


SBS (Styrene-Butadiene-Styrene) is block copolymer which a member of the thermoplastic elastomer family. This product is able to perform as an elastomer without the assistance of a crosslinker such as sulfur.


Stripping is the loss of bond between the aggregates and asphalt binder which typically begins at the bottom of the HMA layer and progresses upward.