Tire Shredding Glossary


Removal of scrap tires from stockpiles and other sites, which have accumulated whole or size-reduced scrap tires

Alternative Daily Cover (ADC)

A material used in place of dirt or soil in order to meet daily cover requirements at solid waste landfills. Material can be a material found in the waste stream such as properly treated petroleum contaminated soil, processed/ground sheet rock, or a material manufactured specifically for daily cover purposes such as reusable tarps, biodegradable plastic tarps, or spray on products such as foam. ADC must provide all the functions of the soil it replaces in a daily cover application such as vector control, dust and litter control, and fire resistance.

Ambient Ground Rubber

Scrap rubber processed at or above ordinary room temperature.


Ambient Ground Rubber processing where scrap tire rubber is ground or processed at or above ordinary room temperature to be mixed with asphalt.

Asphalt-Rubber Concrete

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


American Society of Testing Materials

Bagel Slice

Cutting a tire in half along its circumference.

Baling Tires

A method of volume reduction whereby tires are compressed into a bundle and banded together.

Barrel Stacking

Storage in which tires are stacked flat on top of each other in a vertical position.


That part of the tire that is shaped to fit the rim. Made of high tensile steel wires that are wrapped in woven fabric and held by the plies.

Batch Feeding

Dropping large amounts of material into a shredder, usually done with a grapple or loader.


British Thermal Unit. Tires contain an energy value when used as fuel. This value is measured in BTU.

Chipped Tire

A classified scrap tire particle that has a basic geometrical shape, which generally is 2 in. (5.08 cm) or smaller and has had the bead wire removed. Also referred to as a tire chip.


Any apparatus for separating mixtures of materials into their constituents according to size and density.

Collection of tires

The act of picking up and moving take-off tires from the location of their generation to sorting stations or recycling facilities.

Collection Fee

Fee charged to collect and/or haul and/or transport and/or sort take-off tires or shredded tire material.

Cracker Mill

A machine that crushes scrap tire rubber by passing the material between rotating corrugated steel drums, reducing the rubber to various sizes.

Crumb Rubber

Material derived by reducing scrap tire or other rubber into uniform granules with the inherent reinforcing materials such as steel and fiber removed along with any other type of inert contaminants such as dust, glass or rocks.

Cryogenically Ground Rubber

The process of freezing scrap tire or other rubber and crushing the rubber to the particle size desired.

Cutter Geometry

The shape, size and number of hooks on a cutter, The higher the hooks the more material can be grabbed.


A process in which crumb rubber is subjected to treatment by heat, pressure or the addition of softening agents to regenerate the rubber compound to its original plastic state.

Devulcanized Rubber

The process of treating vulcanized rubber so as to restore the materials that were present prior to vulcanization in the natural rubber state.

Dry Process

Any method that mixes crumb rubber modifier with aggregate before the mixture is charged with asphalt binder. This method applies only to hot-mix asphalt production.

Ductile Materials

Material that is not easily fractured but tends to tear.

Electric Drive

A shredder driven by electric motors.

End Market

An entity that receives processed or unprocessed tire recyclable material and uses it as a finished product or as raw material for a manufacturing process.

End user

The facility which utilizes the heat content or other forms of energy from the combustion of scrap tires (for energy recovery). The last entity that uses the tire, in whatever form, to make a product or provide a service with economic value (for other uses).


There are two forms of feeding recycling equipment. Batch feeding and Meter feeding.


Rubber material that passes through a standard size screen on which coarser fragments are retained.

Flow Control

A legal or economic means that directs the movement of materials to a specific destination.


The textile or reinforcing materials liberated from scrap tires or other rubber reinforced products during processing for crumb rubber.

Friable Materials

Materials that are easily fractured


Any chemical or heat process used to convert rubber to a gas.


The amount of material and how fast it is pulled into the blades for processing.

Granulated Crumb Rubber Modifier (CRM)

Cubical, uniformly shaped, cut crumb rubber particles with a low surface area, which is generally produced by a granulator.


A machine that shears apart scrap tire rubber, cutting the rubber with revolving steel plates that pass at close tolerance, reducing the rubber to smaller sizes.

Ground Crumb Rubber Modifier (CRM)

Irregularly shaped, torn crumb rubber particles with a large surface area, generally produced by a crackermill.

Ground Rubber

Material that results from processing scrap rubber through various mechanisms (e.g., crackermill, shredder, granulator).

Hydraulic Drive

A shredder driven by a hydraulic motor.


A term commonly used to describe or measure the size of crumb rubber. Crumb rubber is sized by the screen through which it passes in the production process. The finer the screen, the more openings it will have per linear inch, i.e., 30 mesh means there are 30 holes or openings per linear inch. The greater number of openings, the smaller the material must be to pass through the screen.

Meter Feeding

Delivering product to the shredder in a controlled stream ,typically accomplished with a conveyor.


A machine that further reduces crumb rubber to a very fine particle, at ambient temperatures, using rotating abrasive discs or other abrasives.

Nominal Size

The actual size of a part will be approximately the same as the nominal size, but need not be exactly the same.

Off the road tire (OTR)

Tire designed primarily for use on unpaved roads or where no roads exist, built for ruggedness and traction rather than for speed.

Post Consumer Scrap

Scrap materials, normally source-separated, that no longer have value for which they were originally intended, but can have potential reuse value as a raw material in new product applications.

Powdered Rubber

Rubber comprised of finely dispersed particles, less than 40 mesh (425 microns) in size, that are generally characterized as light, dry and having very high surface areas. ASTM D11 defines powdered rubber as being composed mainly of non-spherical particles that have a maximum particle dimension equal of below 40 mesh (425 microns).

Pulverized Rubber

Material that has been crushed, pounded or ground to smaller particles.


Pyrolysis is the thermal decomposition of rubber in the absence of oxygen to chemically break the tire into its original components of oil, gas and char.

Radial Tire

A tire construction in which the body ply cords are placed straight across the tire from bead to bead; the belt plies run nearly circumferentially around the tire, under the tread, and constrict the radial ply cords.

Recycled Rubber

Any rubber material derived from processing scrap tires or other rubber products.

Recycled Tire Rubber

Rubber obtained by breaking down used automobile, truck or bus tires.


The series of activities by which take-off tires are collected, sorted, processed and converted into raw materials and used in the production of new products

Rubber Aggregate

Crumb rubber modifier (CRM) added to the hot asphalt mixture using the dry process.

Rubber Modified Asphalt

A general term used to identify the incorporation of scrap tire rubber into asphalt paving materials.

Rubberized Asphalt

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

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 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”.


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 9mm (¼ and 3/8 inch).


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).


Styrene-butadiene Rubber

Scrap Tire

A tire which can no longer be used for its original purpose, due to wear or damage, but can be recovered whole or in part through reuse, recycling, conversion or transformation.

Scrap tire processing

Any method of size reducing whole scrap tires to facilitate recycling, energy recovery or disposal.


A large sieve of suitably mounted wire cloth, grate bars or perforated sheet iron used to separate materials by size.

Shear Shredder

A type of shredder which has two counter-rotating shafts fitted with cutting discs or knives with hooks and spacers that intermesh and overlap.

Shredded rubber

Pieces of scrap tires resulting from mechanical processing.

Shredded tire

A size reduced scrap tire. The reduction in size was accomplished by amechanical processing device, commonly referred to as a shredder.

SHRP (Strategic Highway Research Program)

In 1987, the SHRP began developing a new system for specifying asphalt materials. The final product of the SHRP asphalt research program is a new system referred to as Superpave, which stands for Superior Performing Asphalt Pavements.

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.

Single Shaft Shredder

One rotating shaft the grinds down the input material

Tipping Fee

A fee charged by the operator of a tire processing, recycling, energy recovery or disposal facility to accept scrap tires – either whole or shredded – delivered to these locations.

Tire Derived Fuel (TDF)

A fuel derived from scrap tires of all kinds. This may include whole tires or tires processed into uniform, pieces which satisfy the specifications of the end-user for fuel.

Tire Derived Material (TDM)

Any rubber, steel or fabric material derived from processing tires or rubber products. These materials are found in a variety of sizes, shapes and forms.

Tire Derived Aggregate (TDA)

A form of reusing scrap tires, either whole or shredded, in place of naturally occuring materials in construction. Some examples are- as an aggregate replacement in leachate collection systems, lightweight fill material, crash barriers and reef construction.

Tire Shred

A term used to define randomly ripped, torn or cut tire pieces which have no uniformity.

Tire Shredder

Equipment used to reduce tire materials into smaller pieces. The pieces are usually irregularly shaped.

Trommel Screen

A revolving cylindrical screen used for separating mixtures or materials into their constituents according to size and density. Also referred to as a trommel screen.

Vulcanized Rubber

Rubber that has gone through the process of vulcanization. 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.