Designing Building Designing Building Products Made With Products Made With

Recycled Tires Recycled Tires

Zero Waste—You Make It Happen!

Moving Towards Tire Moving Towards Tire RecyclingRecycling

Over the last 15 years, The Major Tire Industries and The Over the last 15 years, The Major Tire Industries and The Federal and State Governments have been diverting tires Federal and State Governments have been diverting tires from landfills to use in recycling projects.from landfills to use in recycling projects.

In 1989 The California Tire Recycling Act was enacted, In 1989 The California Tire Recycling Act was enacted, which mandated the recycling of used tired in projects to which mandated the recycling of used tired in projects to enhance the constructive utilization of this resource and enhance the constructive utilization of this resource and reduce the detrimental environmental impact associated reduce the detrimental environmental impact associated with improper tire disposal.with improper tire disposal.

California Integrated Waste California Integrated Waste Management Board (CIWMB)Management Board (CIWMB)

According to The California Integrated Waste Management According to The California Integrated Waste Management Board (CIWMB), in the year 2002, approximately 33.5 million Board (CIWMB), in the year 2002, approximately 33.5 million tires were disposed of in California alonetires were disposed of in California alone

About three-quarters of these tires, or 25.1 million tires, were About three-quarters of these tires, or 25.1 million tires, were diverted to constructive uses in 2002, but 8.4 million tires were diverted to constructive uses in 2002, but 8.4 million tires were not.not.

The 8.4 million tires that were not recycled were shredded and The 8.4 million tires that were not recycled were shredded and disposed of in either a solid waste landfill, stored at permitted disposed of in either a solid waste landfill, stored at permitted sites, or otherwise illegally disposed of around the statesites, or otherwise illegally disposed of around the state

Recycled TiresRecycled Tires

In 2002, California’s 25.1 million recycled tires, plus 1.5 In 2002, California’s 25.1 million recycled tires, plus 1.5 million imported into California from neighboring states by million imported into California from neighboring states by processors, were used in the following markets:processors, were used in the following markets:

Civil engineering, including landfill construction, and Civil engineering, including landfill construction, and daily cover (8.9 million, or 33 percent).daily cover (8.9 million, or 33 percent).

Tire-derived fuel (6.1 million, or 23 percent).Tire-derived fuel (6.1 million, or 23 percent).

Crumb rubber manufacturing (5.8 million, or 22 percent).Crumb rubber manufacturing (5.8 million, or 22 percent).

Rethreading and reuse (3.8 million, or 14 percent).Rethreading and reuse (3.8 million, or 14 percent).

Export (2 million, or 8 percent).Export (2 million, or 8 percent).

Civil engineering uses for Civil engineering uses for recycling disposed tiresrecycling disposed tires

Typically waste tires are shredded into smaller Typically waste tires are shredded into smaller chunks at processing facilities and stored at a chunks at processing facilities and stored at a stockpile site. stockpile site.

The shreds are used in numerous highway The shreds are used in numerous highway construction applications such as:construction applications such as:

Lightweight fill in highway embankments constructed over Lightweight fill in highway embankments constructed over unstable soilsunstable soils

Abutment backfill to decrease lateral pressure on Abutment backfill to decrease lateral pressure on containment wallscontainment walls

A vibration dampening layer under rail tracksA vibration dampening layer under rail tracks Thermal insulation under roadways to limit frost Thermal insulation under roadways to limit frost

penetration.penetration.

Other Applications for recycling Other Applications for recycling disposed tiresdisposed tires

Tire Shreds are also used in other Tire Shreds are also used in other projects such as:projects such as:

Leachate drainage layersLeachate drainage layers Gas transmission channelsGas transmission channels Daily cover in modern landfillsDaily cover in modern landfills Alternative septic system drain field Alternative septic system drain field

aggregateaggregate Basement foundation backfill providing Basement foundation backfill providing

enhanced drainage and thermal insulation.enhanced drainage and thermal insulation.

Tire-derived fuel (TDF)Tire-derived fuel (TDF)

Tire-derived fuel (TDF), as its name Tire-derived fuel (TDF), as its name suggests, refers to tires as a supplemental suggests, refers to tires as a supplemental energy resource.energy resource. Tire-derived fuel (TDF) is used in:Tire-derived fuel (TDF) is used in:

Cement kilns to combust whole tires as an Cement kilns to combust whole tires as an alternative to save fossil fuels such as coal, alternative to save fossil fuels such as coal, oil, or natural gas and in power plants as oil, or natural gas and in power plants as shredded tire chunk as a replacement fuel shredded tire chunk as a replacement fuel

Crumb rubber Crumb rubber manufacturingmanufacturing

Crumb rubber manufacturing involves extensive Crumb rubber manufacturing involves extensive processing to reduce shreds even further in size processing to reduce shreds even further in size and to remove reinforcing wire and fabric and to remove reinforcing wire and fabric contained in whole tires. contained in whole tires. Particles (1/4–3/8 inches) have been used as a Particles (1/4–3/8 inches) have been used as a

cushioning material in playgrounds and equestrian ringscushioning material in playgrounds and equestrian rings Slightly larger particles (3/8–1 inch) have been used as Slightly larger particles (3/8–1 inch) have been used as

mulch (sometimes painted for aesthetic appeal) in mulch (sometimes painted for aesthetic appeal) in flowerbeds. flowerbeds.

Finer particles (1/16–1/4 inch) are used as a top dressing Finer particles (1/16–1/4 inch) are used as a top dressing in natural turf to enhance grass durability and in modern in natural turf to enhance grass durability and in modern artificial sports fields to provide cushioning. artificial sports fields to provide cushioning.

Even smaller particles (1/80–1/4 inch) are used in Even smaller particles (1/80–1/4 inch) are used in molded rubber products, sealants, and rubber modified molded rubber products, sealants, and rubber modified asphalt pavements. asphalt pavements.

Re-treadingRe-treading

Re-treading is used to extend the life Re-treading is used to extend the life of the main tire carcassof the main tire carcass Truck tires are generally re-treaded 2–4 Truck tires are generally re-treaded 2–4

times before the carcass is discardedtimes before the carcass is discarded Passenger tires are generally not re-Passenger tires are generally not re-

treaded in the U.S. due to the treaded in the U.S. due to the comparatively low cost of replacement comparatively low cost of replacement tirestires

Tire ProcessingTire Processing

The combination of resilient rubber and metal alloy reinforcing The combination of resilient rubber and metal alloy reinforcing wire presents a difficult challenge in tire processing. wire presents a difficult challenge in tire processing.

A TDF processing facility represents a multi-million dollar A TDF processing facility represents a multi-million dollar investment, and crumb rubber facilities have reportedly cost investment, and crumb rubber facilities have reportedly cost $4–$40 million depending on design capacity, product size, $4–$40 million depending on design capacity, product size, and many other factors. and many other factors.

Every operation is maintenance-intensive because reinforcing Every operation is maintenance-intensive because reinforcing wire rapidly dulls cutting surfaces and erodes all contact wire rapidly dulls cutting surfaces and erodes all contact surfaces. surfaces.

High capital and operating costs are major components in High capital and operating costs are major components in product pricing.product pricing.

Shredded ProductsShredded Products

Shredded Tire Materials

Product Product Size Size Applications Applications Approx. Cost Approx. Cost Range Range

Coarse Coarse 5–10"5–10"

Civil Engineering Civil Engineering

(CE)(CE) $10–$44/ton$10–$44/ton

Nominal 2"Nominal 2" 2–3"2–3" Tire Derived Fuel Tire Derived Fuel

(TDF), CE(TDF), CE $15–$45/ton$15–$45/ton

Nominal 1"Nominal 1" <2"<2" TDF, CETDF, CE $20–$65/ton$20–$65/ton

Crumb RubberCrumb Rubber

Crumb Rubber Crumb Rubber MaterialsMaterials

Product Product Size Size Applications Applications Approx. Cost Approx. Cost Range Range

ParticlesParticles 3/8–1/4"3/8–1/4" Mulch, playground Mulch, playground $180–$300/ton $180–$300/ton

CoarseCoarse 1/5–1/10"1/5–1/10" Sports SurfacesSports Surfaces

$220–$360/ton$220–$360/ton

Medium Medium 1/10–1/30" 1/10–1/30" Rubber Modified Rubber Modified Asphalt, Molding Asphalt, Molding

$220–$400/ton$220–$400/ton

Fine Fine 1/40" 1/40" Rubber Modified Rubber Modified Asphalt, Molding Asphalt, Molding

$300–$1200/ton $300–$1200/ton

Raw Materials and BindersRaw Materials and Binders

Tires are a complex mixture of various types of rubber, carbon black, Tires are a complex mixture of various types of rubber, carbon black, inorganic materials, organic compounds, and reinforcing wire/fabric in inorganic materials, organic compounds, and reinforcing wire/fabric in multiple sections of a tire as shown in the diagram below multiple sections of a tire as shown in the diagram below

Technical Characteristics of Technical Characteristics of Whole or Processed TiresWhole or Processed Tires

Tires and tire products function as homogeneous mixtures, but Tires and tire products function as homogeneous mixtures, but processing can impact physical characteristics as size and shape are processing can impact physical characteristics as size and shape are altered and as reinforcing wire and fabric are removed.altered and as reinforcing wire and fabric are removed.

The following are important tire material characteristics: The following are important tire material characteristics:

Tire Acoustic Insulation Tire Acoustic Insulation Tire Temperature Tire Temperature

Tolerance Tolerance Tire Leaching Tire Leaching

Characteristics Characteristics Tire Energy Content Tire Energy Content Tire Impact Cushioning Tire Impact Cushioning Tire Flammability Tire Flammability

Tire Density Tire Density Tire Durability Tire Durability Tire Moisture Tire Moisture Absorption Absorption Tire Hydraulic Tire Hydraulic Conductivity Conductivity Tire Thermal Tire Thermal Insulation Insulation Tire Vibration Tire Vibration InsulationInsulation

Tire DurabilityTire Durability

Tire rubber contains carbon black, antioxidants, and Tire rubber contains carbon black, antioxidants, and UV stabilizers to enhance resistance to wear, chemical UV stabilizers to enhance resistance to wear, chemical decomposition, and sunlight, respectively. decomposition, and sunlight, respectively.

Strength of whole tires is further enhanced by Strength of whole tires is further enhanced by reinforcing wire and fabric (like nylon or polyester), reinforcing wire and fabric (like nylon or polyester), but this additional strength is lost as wire and fabric but this additional strength is lost as wire and fabric are removed from smaller particles. are removed from smaller particles.

Tires and shreds are not easily damaged by blunt Tires and shreds are not easily damaged by blunt trauma, but they can be cut or punctured by sharp trauma, but they can be cut or punctured by sharp objects.objects.

Tire Moisture AbsorptionTire Moisture Absorption

Tires and shreds can trap water on the surface Tires and shreds can trap water on the surface and in irregular contours, but they are relatively and in irregular contours, but they are relatively impervious to actual absorption. impervious to actual absorption.

Maximum moisture absorption is 2–4 percent.Maximum moisture absorption is 2–4 percent.

Tire Hydraulic ConductivityTire Hydraulic Conductivity

Water flows through whole and shredded tires Water flows through whole and shredded tires readily, even when they are compressed in bales readily, even when they are compressed in bales or under heavy overburden. or under heavy overburden.

Conductivity increases with larger particle size and Conductivity increases with larger particle size and decreases with increasing compaction. decreases with increasing compaction.

Conductivity ranges from 0.5 cm/sec (0.2 Conductivity ranges from 0.5 cm/sec (0.2 inches/sec) for compressed 10–38 mm (0.4–1.5 inches/sec) for compressed 10–38 mm (0.4–1.5 inches) shreds to more than 20 cm/sec (8 inches) shreds to more than 20 cm/sec (8 inches/sec) for 25–64 mm (1–2.5 inches) loose inches/sec) for 25–64 mm (1–2.5 inches) loose shreds.shreds.

Tire Thermal InsulationTire Thermal Insulation

Rubber is a poor thermal conductor, conversely providing a Rubber is a poor thermal conductor, conversely providing a better thermal insulator than soil or aggregate. better thermal insulator than soil or aggregate.

Thermal conductivity depends on particle size, reinforcing Thermal conductivity depends on particle size, reinforcing wire content, compaction, moisture content, ambient wire content, compaction, moisture content, ambient temperature, and other variables.temperature, and other variables.

Thermal conductivity varies from 0.0838 Cal/meter-hour-Thermal conductivity varies from 0.0838 Cal/meter-hour-degree C (5.6X10E-5 Btu/ft-hr-degree F) for 1mm particles degree C (5.6X10E-5 Btu/ft-hr-degree F) for 1mm particles in a thawed state with less than 1 percent moisture content in a thawed state with less than 1 percent moisture content to 0.147 Cal/meter-hour-degree C (9.8X10E-5 Btu/ft-hr-to 0.147 Cal/meter-hour-degree C (9.8X10E-5 Btu/ft-hr-degree F) for 25 mm frozen compacted shreds with a degree F) for 25 mm frozen compacted shreds with a moisture content of 5 percent. moisture content of 5 percent.

Tire Vibration InsulationTire Vibration Insulation

The compressibility of tire shreds allows them to The compressibility of tire shreds allows them to absorb vibrationsabsorb vibrations

Shreds are used for earthquake vibration control Shreds are used for earthquake vibration control around structuresaround structures

Tire Acoustic InsulationTire Acoustic Insulation

Tire rubber is a poor acoustic conductor and, Tire rubber is a poor acoustic conductor and, therefore, a good insulator when used in a therefore, a good insulator when used in a configuration with irregular surfaces to further configuration with irregular surfaces to further diffuse sound.diffuse sound.

One application is highway sound barriers that One application is highway sound barriers that are made from crumb rubber with various are made from crumb rubber with various

bonding agents.bonding agents.

Tire Temperature ToleranceTire Temperature Tolerance

Tire rubber is capable of withstanding a full range Tire rubber is capable of withstanding a full range of ambient temperature extremes without of ambient temperature extremes without undergoing permanent property change. undergoing permanent property change.

Some properties—like flexibility—change as a Some properties—like flexibility—change as a function of temperature, but this change is function of temperature, but this change is reversible and repeatable.reversible and repeatable.

Tire Leaching Tire Leaching CharacteristicsCharacteristics

Tire shred leaching characteristics vary under different ranges of Tire shred leaching characteristics vary under different ranges of pH conditions. pH conditions. Under neutral pH (pH = 7) normally encountered in surface flow-Under neutral pH (pH = 7) normally encountered in surface flow-

through applications, iron and manganese levels increase as these through applications, iron and manganese levels increase as these metals are extracted from any exposed tire reinforcing wire. metals are extracted from any exposed tire reinforcing wire.

However, both metals are generally present in soils, and the increases are However, both metals are generally present in soils, and the increases are generally not considered to be harmful to people or the environment. generally not considered to be harmful to people or the environment.

The rate of dissolution of wire increases under acidic conditions (pH < The rate of dissolution of wire increases under acidic conditions (pH < 7), and zinc present within surface rubber can also be leached, but 7), and zinc present within surface rubber can also be leached, but levels generally remain within acceptable parameters. levels generally remain within acceptable parameters.

Under basic conditions (pH>7), organic compounds can be leached in Under basic conditions (pH>7), organic compounds can be leached in trace quantities.trace quantities.

As a result of this data, tire chips are normally used in flow-As a result of this data, tire chips are normally used in flow-through applications above the water table to minimize long-term through applications above the water table to minimize long-term leaching exposure and in relatively neutral natural conditions. leaching exposure and in relatively neutral natural conditions.

Tire Energy ContentTire Energy Content

Tires are made from oil and gas. Tires are made from oil and gas.

Tires have an energy content greater than coal, Tires have an energy content greater than coal, making them thermally suitable for use as a making them thermally suitable for use as a supplemental energy resource in the manufacture supplemental energy resource in the manufacture of cement, paper, and power. of cement, paper, and power.

Tire Impact CushioningTire Impact Cushioning

Shredded tire products have resiliency and durability that Shredded tire products have resiliency and durability that lends itself to cushioning applications. lends itself to cushioning applications.

Loose-fill crumb rubber applied below playground equipment Loose-fill crumb rubber applied below playground equipment has cushioning characteristics clearly superior to wood chips, has cushioning characteristics clearly superior to wood chips, sand, and pea gravel commonly used for this purpose. sand, and pea gravel commonly used for this purpose.

In some cases, crumb rubber has been mixed with In some cases, crumb rubber has been mixed with polyurethane binders and poured on top of an asphalt base to polyurethane binders and poured on top of an asphalt base to create a fixed “pour-in-place” cushioning surface.create a fixed “pour-in-place” cushioning surface.

Crumb rubber has also been compression-molded with Crumb rubber has also been compression-molded with polyurethane binders into large (1–3 square feet) 2–3-inch polyurethane binders into large (1–3 square feet) 2–3-inch interlocking tiles that can be secured to an asphalt base as a interlocking tiles that can be secured to an asphalt base as a cushioning surface cushioning surface

Tire FlammabilityTire Flammability

Tire shreds have a reported flash point of 582º F, Tire shreds have a reported flash point of 582º F, higher than some other materials used for higher than some other materials used for architectural purposes such as wood, paper, architectural purposes such as wood, paper, foam, and fabric.foam, and fabric.

The flash point is the temperature at which a The flash point is the temperature at which a material will initially ignite, and the temperature material will initially ignite, and the temperature to support continuing combustion (fire point) is to support continuing combustion (fire point) is

even higher.even higher.

ASTM StandardsASTM Standards

A few American Standards for Testing Materials (ASTM) international A few American Standards for Testing Materials (ASTM) international standards exist for products made from waste tires:standards exist for products made from waste tires:

- - D6270-98 Standard Practice for Use of Scrap Tires in Civil Engineering D6270-98 Standard Practice for Use of Scrap Tires in Civil Engineering ApplicationsApplications

- D5603-01 Standard Classification for Rubber Compounding Materials—- D5603-01 Standard Classification for Rubber Compounding Materials—Recycled Vulcanized Particulate RubberRecycled Vulcanized Particulate Rubber

-- D5644-01 Standard Test Method for Rubber Compounding Materials— D5644-01 Standard Test Method for Rubber Compounding Materials—Determination of Particle Size Distribution of Vulcanized Particulate Determination of Particle Size Distribution of Vulcanized Particulate RubberRubber

- - D6814-02e1 Standard Test Method for Determination of Percent D6814-02e1 Standard Test Method for Determination of Percent Devulcanization of Crumb Rubber Based on Crosslink DensityDevulcanization of Crumb Rubber Based on Crosslink Density

- - F1292-99 Standard Specification for Impact Attenuation of Surface F1292-99 Standard Specification for Impact Attenuation of Surface Systems Under and Around Playground EquipmentSystems Under and Around Playground Equipment

Design ChallengesDesign Challenges

Since the 1980s, several states have funded projects to study Since the 1980s, several states have funded projects to study and create new uses and products made from tires and crumb and create new uses and products made from tires and crumb rubber. The following technical and economic challenges rubber. The following technical and economic challenges represent a variety of tire and crumb rubber applications as represent a variety of tire and crumb rubber applications as well as modifications to crumb rubber, namely surfaced well as modifications to crumb rubber, namely surfaced modified rubber:modified rubber:

Interior flooring (Indoor Air Quality Challenges)Interior flooring (Indoor Air Quality Challenges) Tire-Reinforced Concrete Blocks (Economic/Performance Tire-Reinforced Concrete Blocks (Economic/Performance

Challenges)Challenges) Rubber Railroad Crossings (Performance Challenges)Rubber Railroad Crossings (Performance Challenges) Devulcanized/Surface Modified Rubber (Process Challenges)Devulcanized/Surface Modified Rubber (Process Challenges) Highway Crash Barriers (Organizational Challenges)Highway Crash Barriers (Organizational Challenges) Houses (Seismic and Other Challenges)Houses (Seismic and Other Challenges)

Future Possibilities:Future Possibilities:

Recycled Tires as a raw material, whole and Recycled Tires as a raw material, whole and shredded, may be harnessed through creative shredded, may be harnessed through creative design, processing, and marketing to reenter the design, processing, and marketing to reenter the economy as a beneficial money-making product. economy as a beneficial money-making product.

Already, many existing products use old tires but Already, many existing products use old tires but this just scratches the surface of possibilities.this just scratches the surface of possibilities.

In the future, recycled tire materials may lead to In the future, recycled tire materials may lead to new and better opportunities, generating millions new and better opportunities, generating millions of dollars in revenue and opening whole new of dollars in revenue and opening whole new markets from a previously wasted commodity. markets from a previously wasted commodity.