RMRC • User Guidelines for Waste and Byproduct Materials in Pavement Construction •

Approximately 11 million tons of asphalt roofing shingle scrap is generated each year in the United States . ⁽³⁾ There are two types of roofing shingle scraps. They are referred to as tear-off roofing shingles, and roofing shingle tabs, also called prompt roofing shingle scrap. Tear-off roofing shingles are generated during the demolition or replacement of existing roofs. Roofing shingle tabs are generated when new asphalt shingles are trimmed during production to the required physical dimensions or from "out-of-spec" shingles. Roofing shingle tab materials that result from shingle manufacture are estimated to range between 5 to 10% of the total production. Current estimates indicate that the percentage of roofing scrap generated by activity is as follows; 87.5% manufacturing scrap and 12.5% is tear-off roofing scrap ⁽¹¹⁾ .

Asphalt shingle scrap created during the manufacturing process is generally uniform and homogenous. The content can be certified and free of debris ⁽³⁾ .The quality of tear-off roofing shingles can vary. Tear-off roofing shingles may contain debris such as nails, wood, paper, and plastic that is removed through processing. The aggregate in scrap shingles can be lost in the weathering process that occurs during the service period. As a result, tear-off scrap may contain more than 30% asphalt by weight. The aged binder in tear-off roofing scrap may also be hard or even brittle ⁽¹¹⁾ , but tear-off shingle is easier to shred than factory scrap.

Roofing shingles are produced by impregnating either organic felt produced from cellulose fibers, or glass felt produced from glass fibers, with a hot saturant asphalt, which is subsequently coated on both sides with more asphalt and finally surfaced with mineral granules. Most roofing shingles produced are of the organic felt type. The saturant and coating asphalt need not be the same. Both saturant and coating asphalts are produced by "blowing", a process in which air is bubbled through molten asphalt flux. The heat and oxygen act to change the characteristics of the asphalt. The process is monitored, and the "blowing" is stopped when the desired characteristics have been produced.

The largest component of roofing shingles (60 to 70 percent by mass) is the mineral material. There are several different types in each shingle. ⁽⁷⁾ They can include ceramic granules (comprising crushed rock particles, typically trap rock, coated with colored, ceramic oxides), lap granules (coal slag ground to roughly the same size as the ceramic granules), backsurfacer sand (washed, natural sand used in small quantities to keep packaged shingles from sticking together), and asphalt stabilizer (powdered limestone that is mixed into the asphalt).

Specifications for roofing shingles are set out in ASTM D255 ⁽¹⁾ and ASTM D3462. ⁽²⁾ The composition of scrap shingles may vary between different manufactures. Older shingles were likely to be made with more organic material, while new shingles are made with fiberglass mats ⁽¹¹⁾ .

Additional information on recycling of roofing shingle scrap can be obtained from the following organizations:

Construction Materials Recycling Association
P.O. Box 122
Eola , IL 60519
www.shinglerecycling.org

CURRENT MANAGEMENT OPTIONS

Asphalt shingle scrap is readily recyclable for a variety of reasons which include: 1. it is generated separately or can readily be segregated from other components of the solid waste stream; 2. the processing technology of asphalt shingles needed to meet the requirements for raw material has been successfully refined; and 3. the processed scrap is a valuable raw material in the production of hot mix asphalt (HMA). There are various opportunities to recycle shingles in road construction applications in addition to HMA applications. Some recycling opportunities have proven to be more viable than others. Benefits of recycling asphalt shingles include conservation of landfill space, potentially lower disposal costs for shingle scrap manufactures, reduced cost in the production of HMA and conservation of virgin material ⁽¹¹⁾. A best management practices manual for recycling asphalt shingles was completed in 2007 ⁽¹²⁾.

Below is an interactive map showing states with shingle recycling projects and information.

State	Projects/Information
California	California Integrated Waste Management Board (CIWMB) fact sheets about asphalt shingle recycling: Asphalt Roofing Shingles Recycling: Introduction ( CIWMB Pub. #431-97-031 ) Asphalt Roofing Shingles in Asphalt Pavement ( CIWMB Pub #431-97-033 ) Asphalt Roofing Shingles in Aggregate Base ( CIWMB Pub #431-97-032 ) Asphalt Roofing Shingles in Cold Patch ( CIWMB Pub #431-98-013 )
Georgia	In 1997, the Georgia General Assembly passed legislation encouraging the recycling of asphalt shingles. The legislation also required the Pollution Prevention Assistance Division to work with the Environmental Protection Division to develop a plan to encourage asphalt shingle scrap recycling A report has been prepared in response to this legislative requirement. Asphalt Roofing Shingle Report prepared for the Georgia General Assembly Watson , Donald E., et al., " Georgia's Experience with Recycled Roofing Shingles in Asphaltic Concrete. " Georgia Department of Transportation ( GDOT ), Forest Park , Georgia , 1998.
Iowa	Iowa Department of Transportation, "Determination and Evaluation for Alternative Methods for Managing and Controlling Highway-Related Dust, Phase II Demonstration Project" with Iowa State University , 2003. Iowa DOT . Iowa Department of Transportation, " Recycled Asphalt Shingles for Slurry Leveling and Crack Filling " with City of Spencer , Iowa , 2002. Iowa DOT . Lohnes , R. A.; Coree, B. J., "Determination and Evaluation of Alternate Methods for Managing and Controlling Highway-Related Dust" , Iowa Department of Transportation, June 30, 2002 . Marks , Vernon J., and Petermeier, Gerald, "Let Me Shingle Your Roadway." Research Project HR-2079, Iowa Department of Transportation, Ames , Iowa , 1997.
Massachusetts	Bauman , Amy, "Asphalt Shingle Recycling in Massachusetts," a study sponsored by The Home Depot Foundation, March 15, 2005 .
Minnesota	Janisch , D. and Turgeon, C., " Minnesota's Experience Using Shingle Scrap in Bituminous Pavements " Report No. MN/PR-96/34, Minnesota Department of Transportation, 1996. NTIS. Krivit , Dan, " An Environmental White Paper Report as Part of the RMRC Project Overcoming the Barriers to Asphalt Shingle Recycling ". Prepared for the Minnesota Department of Transportation and the Recycled Materials Resource Center . October 2002. Dan Krivit and Associates . Krivit , Dan, "Driving Change: Solid Waste Management Coordinating Board (SWMCB) Manufacturer Shingle Scrap Recycling Project: Final Report." August 27, 2004 . Dan Krivit and Associates . Newcomb , David, et al., "Influence of Roofing Shingles on Asphalt Concrete Mixture Properties." Report MN/RC-93/09, University of Minnesota , Minnesota , 1993. Turgeon , Curtis M., "Waste Tire &Shingle Scrap Bituminous Paving Test Sections On The Munger Recreational Trail Gateway Segment." Office of Materials and Research, Minnesota Department of Transportation, February, 1991. Shingle Recycling Fact Sheets Asphalt Paving Design Guide by Minnesota Asphalt Paving Association (MAPA): Minnesota Mix Specifications, Methods & Quality Control
New Jersey	Bishop , Gordon, "Jersey firm gets recycling award for use of shingles in road repair"; The Star-Ledger
North Carolina	Ross , Jr., Ben B., " An Evaluation of the Use of Hot Mix Asphalt Pavements Containing Roofing Shingle Material in North Carolina ." Prepared for the North Carolina Department of Environment, Health and Natural Resources, 1997. NCDOT Asphalt Shingle Slide Show
Pennsylvania	Boyle , Michael, " Materials-Related Forensic Analysis and Specialized Testing: Laboratory Evaluation of Hot-Mix Asphalt (HMA) Mixtures Containing Recycled or Waste Product Materials Using Performance Testing" , Valley Forge Laboratories Inc., Advanced Asphalt Technologies, LLC, Federal Highway Administration, Pennsylvania Department of Transportation, 2005. Hughes , John J.; Sypolt, Matthew, "Post-Consumer Shingles in HMA" , Pennsylvania Department of Transportation, Federal Highway Administration, Final Report, 2005. Reed , A., " Reclaimed Manufacturer Asphalt Roofing Shingles in Asphalt Mixtures. " Research Project N0. 91-77. Pennsylvania Department of Transportation, 40 pp. 1999.
South Carolina	Amirkhanian , S N; Vaughan , K M, "Field Evaluation of Use of Waste Shingles in Asphalt Mixtures" , Clemson University , South Carolina Department of Transportation, Federal Highway Administration, 2001.
Texas	TxDOT Experience with Shingles in HMA - Brochure Button , Joe W., et al., " Roofing Shingles and Toner in Asphalt Pavements . " Research Report 1344-2F, Texas Transportation Institute, College Station , Texas , 1995. (A short summary of the report can be found on the TxDOT site).
Vermont	Vermont Agency of Natural Resources, " Recycled Shingles in Road Applications ." September 1999. ( Vermont Agency of Natural Resources )

Most roofing shingle scrap is presently disposed of by landfilling. Approximately shingles represent one third of the waste stream from construction that is landfilled each year ⁽¹⁰⁾ . Estimates of the cost for disposing shingles in a landfill may be between $18-$60 per ton ⁽⁴⁾ .

MARKET SOURCES

Roofing shingle tabs (prompt shingle scrap) can be obtained directly from shingle manufacturers. Tear-off shingle scrap can be obtained directly from roofing contractors or disposal sites that accept the scrap. Information on tab or prompt scrap sources can be obtained from the roofing shingle suppliers or manufacturers.

The general composition of asphalt shingles can vary. The typical asphalt shingle components are listed in Table 1.

The American Society for Testing and Materials (ASTM) has specifications for roofing shingles. The specifications, ASTM D 255-86 (Asphalt Shingles [Organic Felt] Surfaced with Mineral Granules) and ASTM D3462-87 (Asphalt Shingles Made from Glass Felt and Surfaced with Mineral Granules) permit the use of a wide range of products.

Individual shingle manufactures will have more detailed specifications regarding their shingles. Information about the inclusion of asbestos in roofing shingles is inconsistent and therefore it is difficult to quantify its use in roofing shingles. California Integrated Waste Management Board reports that the total asbestos content in asphalt shingles manufactured in 1963 was .02% and in 1977 it had dropped to .00016%. The Georgia department of Transportation however reports that asbestos was used in roofing shingles as late as the 1980s. The Iowa Department of Transportation states that the use of asbestos in roofing shingles was discontinued after 1973. The Iowa Department of Transportation also conducted a study on the asbestos content of roofing shingles. From 368 shingle samples analyzed only 3 contained asbestos, .8 % ^{( 9)}.

HIGHWAY USES AND PROCESSING REQUIREMENTS

Testing has demonstrated that roofing shingle scrap can successfully be incorporated into asphalt mixes. The addition of shingles into hot mix asphalt (HMA) can yield HMA with properties comparable to conventional HMA mixes. Shingles can also be used to create stone matrix asphalt (SMA). Further research needs to be completed in order to reach the optimum SMA mix design. In HMA applications, the asphalt from asphalt shingles will produce in a much stiffer recycled asphalt binder. The use of recycled shingles in HMA will typically result in an improved rutting resistance in the mix. The mix however, may have lower fatigue resistance and a lower low temperature cracking resistance. With the use of a softer virgin binder the fatigue and low temperature performance challenges of the mix can be improved ⁽⁴⁾ .

Prompt roofing shingle scrap is mainly produced in tabs approximately 285 mm long by 9.5 mm wide by 3 mm thickness (11.5 in by 3/8 in by 1/8 in) which must then be processed to suitable size for introduction into the hot mix asphalt. The asphalt tabs are processed in two stages. The tabs are first shredded using a rotary shredder consisting of two slow-speed blades turning at approximately 50 revolutions per minute. This reduces the chips into smaller, but still quite coarse pieces. The smaller pieces are then reduced to a nominal size of about 9.5 mm (3/8 in) or finer using a high-speed hammermill operating at about 800 to 900 revolutions per minute. To keep the roofing shingle material from agglomerating during processing the material is kept cool by watering at the hammer mill and then stockpiled. The application of water is not very desirable since the processed material becomes quite wet and must be dried prior to introduction into hot mix asphalt ⁽⁸⁾ . As an alternative to water shreds are sometimes blended with 20% sand or screenings to keep the shingles cool and limit dust. The sand and screenings would otherwise have been added later in the production of HMA and cold mix asphalt patching material; however by adding them earlier in the process it limits the use of water. Recycled asphalt pavement has also been mixed with the shredded shingles in order to prevent stockpile clumping.

Tear-off roofing shingle is easier to shred than factory scrap. The tear-off roofing shingle is hardened with age and as a result it is unlikely it will agglomerate during processing. The debris that contaminates tear-off roofing shingle scrap can be effectively removed. Nails are removed with magnets, paper and other lightweight contaminants are removed with blowers or vacuums ⁽⁹⁾ .

Little research has been done in the way of asphalt shingles in cold-applied paving mixes ⁽⁹⁾. It may be necessary to heat the mix or add solvents such as diesel, kerosene or asphalt rejuvenating agents to activate the air-blown and possibly aged asphalt in the roofing shingles ⁽¹¹⁾ .The combination of the hard asphalt, uniform and angular aggregate and the entrained cellulose or glass fibers appear to make a quality product that is potentially comparable with other "high performance" cold patch mixes ⁽⁹⁾ . After the "cold patch" material is placed it is either tapped down with a shovel or driven over. One benefit of a "cold patch" product is that it allows for vehicle traffic to be allowed over the packed area almost immediately after it has been patched ⁽¹¹⁾ .

Roofing shingles incorporated into asphalt paving mixes not only modify the binder, but also, depending on the size of the shredded material, function like aggregate or mineral filler. Organic felt and glass felt particles in particular tend to function like a mineral filler substitute.

The usage of roofing shingles in road applications as an aggregate is becoming much more common, although there is still a need for scientific research. This technology has however been tested in field tests with successful results ⁽⁹⁾ . Solar heat and the weight from traffic helps to "melt" the shingles into a single mass. This surface could also be used for equipment yards and parking lots ⁽¹¹⁾ .

Asphalt roofing shingles can be added to a low-end asphalt paving mixture used as an aggregate as an alternative to stones and gravel. This base would support the pavement. Asphalt roofing shingles can be reduced to small pieces about 2.5" or smaller and then added to the mixture. This mixture has the potential to compete effectively with rock and gravel as an alternative ground cover ⁽¹¹⁾ .

Ground asphalt shingles may be used as a stabilizer in wet and muddy areas. The asphalt shingles are typically ground and mixed with significant quantities of crushed asphalt pavement for use as ground cover ⁽¹¹⁾ .

MATERIAL PROPERTIES

Roofing shingles are unlike other by-product or secondary materials in that they contain components of fine aggregate, mineral filler, and asphalt cement. There are also differences between the types of shingles (organic and glass felt) produced. As shown in Table 2, organic felt shingles can be expected to exhibit higher moisture content and lower specific gravity than glass felt shingles. Shredded organic felt shingle scrap also exhibits much higher absorption than shredded fiberglass shingle scrap.

Typical physical properties of recovered asphalt cement and the gradation of mineral granules in shingle scrap are listed in Table 3. Asphalt cement in old roofing shingles undergoes oxidative age hardening and stearic hardening (a hardening process in which solid compounds separate from volatile oils in the asphalt cement). Consequently, the asphalt cement in old tear-off roofing shingles is somewhat harder than new asphalt. Although the stearic hardening process has been demonstrated to be reversible by reheating and/or solubilizing, ⁽⁶⁾ oxidative age hardening is not reversible.

ENVIRONMENTAL CONSIDERATIONS

Asbestos content in tear-off roofing shingles continue to be a concern for regulators ⁽¹³⁾. A rigorous literature review and compilation of asbestos testing data was compiled in 2007 and found that asbestos was detected in just over 1% of the samples (out of 27,000). ⁽¹⁴⁾ Asphalt shingles contain asphalt a petroleum derived product that contains polycyclic aromatic hydrocarbons (PAHs). Questions have been raised as to whether ground up shingles pose a direct or leaching exposure risk, as well as potentially impacting hot mix asphalt plant emissions ⁽¹³⁾. There is no literature to indicate emissions at hot mix plants are any different using shingles. Further research on the leachability is currently being conducted in Florida.

[ Material Description ] [ Asphalt Concrete ]

ROOFING SHINGLE SCRAPMaterial Description

ORIGIN