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Recycling - Engineering in Recycling - Previous Page

SCRAP TIRES - Material Description
Asphalt Concrete (Wet Process)
Asphalt Concrete (Dry Process)

Asphalt-Rubber - Glossary of Terms

Asphalt-Rubber - Glossary of Terms Ambient Ground Rubber processing where scrap tire rubber is ground or processed at or above ordinary room temperature.

Asphalt-Rubber asphalt cement modified with a minimum of 15% crumb rubber modifier (CRM).

Asphalt-Rubber Blend a blend of crumb rubber modifier (CRM) (finely processed to a No. 16 to No. 30 mesh gradation) and asphalt cement, which is utilized as the binder in various types of pavement rehabilitation and construction procedures. The CRM percentage can range from 15 to 26 percent CRM by weight of the asphalt cement depending on the specified application. The CRM and asphalt cement are blended at elevated temperatures to promote the chemical and physical bonding of the two constituents. Various petroleum distillates or extender oils may be added to the blend to reduce viscosity, increase spray-ability and promote workability. The blend can be used as the binder in chip seals, cape seal applications, pond linings, or gap and open graded hot mix. When used as a binder in hot mix applications, the aggregate gradations and the quality of the aggregate need to conform to industry approved specifications.


Asphalt-Rubber Concrete implies the use of an asphalt-rubber binder with gap or open graded aggregate gradations in a hot mix application.

Automobile Tires tires with an outside diameter less than 66 cm (26 inches) used on automobiles, pickups, and light trucks.

Buffing Waste high quality scrap tire rubber which is a byproduct from the conditioning of tire carcasses (casings) in preparation for re-treading.

Crackermill machinery that tears apart scrap tire shreds by passing the material between rotating corrugated steel drums, reducing the size of the rubber to a crumb particle generally 4.75 mm to 425 microns (No. 4 to No. 40) mesh sieve.

Crumb Rubber Modifier (CRM) a general term for scrap tire rubber that is reduced in size and used as a modifier in asphalt paving materials.

Cryogenically Ground Rubber a process that freezes the scrap tire rubber and crushes the rubber to the particle size desired.

Devulcanized Rubber rubber that is a complex macro structure material ant through vulcanization the sulfur molecules form complex cross linkages between and within the rubber macromolecular structure.

Devulcanization is the process by which the sulfur molecules are de-linked from the rubber molecules and stabilized, thereby facilitating the formation of new cross-linking structures with reapplication of heat and pressure.

Dry Process any method that mixes the crumb rubber modifier (CRM) with the aggregate material before this mixture is charged with the asphalt cement. This method only applies to hot-mix asphalt production.

Extender Oil an aromatic oil used to supplement the reaction of the asphalt cement and the crumb rubber modifier (CRM).

Granulated Crumb Rubber Modifier (CRM) cubical, uniformly shaped, cut crumb rubber particles with a low surface area, which is generally produced by a granulator.

Granulator a process that shears apart the scrap tire rubber, cutting the rubber with revolving steel plates that pass at a close tolerance, reducing the rubber to particles generally 9.5 to 2.0 mm (3/8 inch to No. 10) sieve size.

Ground Crumb Rubber Modifier (CRM) irregularly shaped, torn crumb rubber particles with a large surface area, generally produced by a crackermill.

Reaction the interaction between asphalt cement and crumb rubber modifier (CRM) when blended together at a certain temperature for a certain period of time. The reaction, more appropriately defined as polymer swell, is not a chemical reaction. It is the absorption of aromatic oils from the asphalt cement into the polymer chains of the crumb rubber.

Recycled Tire Rubber rubber obtained by processing used automobile, truck or bus tires.
Rubber Aggregate crumb rubber modifier (CRM) added to the hot asphalt mixture using the dry process.

Rubber-Modified Asphalt Concrete a hot mix asphalt concrete mixture with dense graded aggregates a rubberized asphalt type of binder. (Note: The CRM percentage is generally low (5 to 10%) and is generally finer mesh (30 mesh or lower).

Rubber-Modified Hot-Mix Asphalt a hot-mix asphalt mixture that incorporates the crumb rubber modifier (CRM) primarily as rubber aggregate. Also known as the "dry process".

Rubberized Asphalt asphalt cement modified with crumb rubber modifier (CRM) at less that 15 percent by total weight of the asphalt cement.

SAM the abbreviation for a Stress Absorbing Membrane. A SAM is used primarily to mitigate reflective cracking of an existing distressed asphalt or rigid pavement. It is usually associated with an asphalt-rubber binder sprayed on an existing pavement surface at .60 gallons per square yard (05 gallons per square yard) and immediately followed by an application of a uniform pre-coated aggregate, which is then rolled and the aggregate is embedded into the binder layer. The nominal thickness normally ranges between 6 and 9 mm (1/4 and 3/8 inch).

SAMI the abbreviation for a Stress Absorbing Membrane Interlayer. A SAMI is the same as aSAM but is applied prior to an asphalt concrete overlay. This overlay may or may not contain crumb rubber modifier (CRM).

Shredding process that reduces scrap tires to small pieces 0.15 meter squared (6 inches squared) and smaller.

Stress Absorbing Membrane a surface treatment (membrane) using an asphalt-rubber spray application and cover aggregate. Same as a SAM.

Stress Absorbing Membrane Interlayer a surface treatment (membrane) generally associated with an asphalt-rubber spray application and cover aggregate, designed to resist the stress and strain of reflective cracking and delay the propagation of the cracks through a new overlay. Same as a SAMI.

Tread Rubber rubber that consists primarily of tread rubber with less than 5 percent sidewall material (approximately).

Truck Tires tires with an outside diameter greater that 66 cm (26 inches) and less that 152 cm (60 inches); used on commercial trucks and buses.

Vulcanized Rubber rubber that has gone through the vulcanization process. This is a process by which an agent, such as sulfur, is added to rubber in the manufacturing process to give the product certain required characteristics, such as strength, hardness and elasticity. Rubber is a complex macro molecular structured material and through vulcanization the sulfur molecules form complex cross linkages between and within the rubber macromolecular structure.

Wet Process a method that blends crumb rubber modifier (CRM) with the asphalt cement before incorporating the resulting binder for use in an asphalt paving or surfacing project. This terminology is generally associated with asphalt-rubber binder materials.

Whole Tire Rubber rubber that includes tread and sidewalls in portions that approximate the respective weights in an average tire.

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