Recycled Materials and Byproducts in Highway Applications—Manufacturing and Construction Byproducts, Volume 8 (2013)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

27 From the late 1800s to the 1970s roofing shingles were manu- factured by saturating a thick organic mat such as cotton, waste paper, and wood fibers with asphalt and topped with protective stone coating (Seattle Roof Broker 2010; Figure 9). Although the shingles came with 15- to 20-year warranties, they were typically left in place from 30 to 35 years. In the 1970s, the conversion was made from organic to fiberglass backing. However, the 1974 oil embargo, the economic recession in the 1980s, and durability concerns in hot moist climates forced roofing shingle manufacturers to adjust shingle composition. This led to a reduction in the fiberglass mat (expensive) and an increase in mineral filler content in the asphalt to extend the binder volume, save money, and improve durability. This resulted in declining asphalt content in the newer shingle pro ducts compared with the older recycled asphalt shingles (RAS) materials. There are several categories of roofing materials that are available for recycling. These include: • Roofing manufacturing byproducts • Tear-offs • Built up roofing (BUR). Additional information can be found at the following websites: • Shingle Recycling: http://www.shinglerecycling.org/ content/technical-reports • National Association of Home Builders: http://www. nahbrc.com/index.aspx. Types of possible byproducTs roofing shingles (Manufacturer) Roofing shingles are produced by saturating the backing felt material, which is either organic (cellulose or wood fiber) or fiberglass (VANR 1999). This is followed by coating the material on both sides with additional asphalt. The asphalt is treated with exposure to air (air blown or bubbled) to increase the viscosity and reduce the temperature susceptibility. Pow- dered limestone (70% passing the 0.075 mm sieve) or other fine granulated materials are also added to the asphalt as a stabilizer and viscosity enhancing material. When the desired thickness of asphalt has been applied, a granular material is used to finish the surface, usually crushed rock coated with ceramic metal oxides with some coal slag at the headlap of the shingle. The particles are reported as being hard and angular with a uniform size that is primarily between 2.36 and 3.0 mm. The back of the shingle is coated with fine sand (<0.425 mm) to prevent sticking together during packaging and transporting. There are 77 plants in the United States that produce approx- imately 12.5 billion square feet of shingles per year (Brock 2007). About 65% of the new shingles are used for reroofing projects and only 35% for new roofs. Manufacturing roof- ing shingle byproducts are comprised of factory scrap from the production process. Tear-offs Roofs are commonly replaced after 20 years, but this can be done by overlaying the old shingles with new ones (Califor- nia Integrated Waste Management Board 2009). Although most building codes limit maintenance to one reroof without tearing off the old materials, more than two layers of roofing materials can be encountered. This results in a range of shingle ages in the same reroof or demolition job in the construction industry waste stream and is commonly landfilled. Most of the older roofing materials are organic-backed materials. The asphalt in the tear-offs has aged over the years of environmen- tal exposure and the amount of granular material is also lower than in the manufacturing byproduct because of weathering. Tear-offs usually contain other contaminates such as nails, paper, wood, and other miscellaneous debris (RMRC 2008a; CIWMB 2009). built up roofs (bur) These roofing systems have been in use for more than a cen- tury (NRCA 2010) and consist of alternating layers of binder and reinforcing fabrics. Sometimes the first layer (base sheet) is mechanically fastened to the roof. If the first layer is directly applied to the roof deck or insulation it is considered to be fully adhered. The reinforcing fabric is also referred to as roof- ing felts or ply sheets, which are either organic or fiberglass mats. The binder in built up roofs (BUR) can be hot-applied asphalt binders, hot-applied coal tar, or cold-applied solvent- based asphalts. The surfacing for BUR roofs include aggre- gates such as gravel, slag or mineral granules, glass-fiber or mineral surfaced cap sheets, hot mopped-asphalt, aluminum, or chapter two roofing shingles

28 were shredded by large wood chippers with 500 hp, which produced about 50 to 75 tons of RAS per hour. To ensure that the RAS met the ½ inch minus particles size, the material needed to pass through the shredder a second time (Figure 10). Grinding was easier in the winter when the shingles were cold and more brittle, which helped minimize agglomeration. The oxidation of the roofing asphalt helped with reducing the agglomeration of the shredded material (VANR 1999). A Minnesota recycler found that grinding manufacturing byproduct was easier if the material had been weathered by being stored in a stockpile for a year before grinding. Manu- facturing byproducts were reportedly more difficult to process than the aged roofing material, which had hardened with age and was less likely to agglomerate during grinding (VANR 1999). Some shredding processes used water to cool the cut- ting heads and limit dust production. Schroer (2007) noted that an additional feature that was needed in the tear-off RAS grinding process was a removal system for nails and other ferrous materials. This was accom- plished by fitting the conveyor belts with magnets; a mini- mum of three or four was suggested. A final detection sys- tem of a metal detection device and manual sorting was also suggested as the final QC process. Wood could be removed either by hand or floated off in a water floatation unit. Air blowers to remove paper and lightweight debris were an alternative method for removal. Sand may or may not be needed to prevent clumping of the RAS. A trommel screen can be used to either divert over- sized particles back to the shredder or to the final stockpile. Schroer (2007) also noted that RAS can be pre-blended with reclaimed asphalt pavement (RAP) in a metered process to produce a composite blend that will resist re-agglomeration. Schroer (2007) noted that a dust control plan was needed for the grinding operation that should include the ability to provide optimum amounts of sprayed water at critical grinding stages, shrouds, negative air (i.e., suction), and standard employee health and safety protection equipment and procedures. For stockpiling, shingles needed to be either processed shortly before using, covered and kept dry, or post-processed to dry out, particularly if they were to be used in HMA appli- cations (Decker 2002; Schroer 2007). Stockpiled RAS also tended to re-agglomerate in stockpiles, especially during the warm summer season. Blending ground RAS with sand or RAP helped prevent agglomeration; however, some agen- cies, such as Minnesota DOT (MnDOT), did not allow pre- blending of stockpiles. Schroer (2007) and Gevrenov (2007) suggested siting was important to the feasibility of processing and using RAS. The location of the recycling operation may require state and local permits such as air, water, zoning, and possibly solid waste. Good location choices would consider the location of elastomeric coatings. Standards used to specify BUR materials include: • ASTM D226, Standard Specification for Asphalt Satu- rated Organic Felt Used in Roofing and Waterproofing • ASTM D312, Standard Specification for Asphalt Used in Roofing • ASTM D450, Standard Specification for Coal Tar Pitch Used in Roofing, Damp Proofing and Waterproofing • ASTM D2178, Standard Specification for Asphalt Glass Felt Used in Roofing and Waterproofing • ASTM D4990, Standard Specification for Coal Tar Glass Felt Used in Roofing and Waterproofing. recycled AsphAlT shingles processing Regardless of the source of shingle, RAS needs to be post- processed by shredding, sizing, and cleaning in order to be used in highway applications. The steps in processing RAS for use in highway applications are (Figure 10): • Grinding • Sizing • Grading • Contaminate removal (tear-offs) • Stockpiling. Brock (2007) described various methods of shredding shingle byproducts that have been tried over the years with variable success including crushers, hammer mills, and rotary shredders. Brock (2007) noted that currently most shingles Base (fiberglass or organic felt) Waterproofing asphalt Waterproofing asphalt Granular/aggregate Back surfacing FIGURE 9 Typical composition of roofing shingles (after Gevrenov 2007). Sand Hopper Conveyor Conveyor Trommel Screen Stockpile Shingle Shredder Shingle Feeder FIGURE 10 Typical grinding operation set-up (after Brock 2007).

29 agreed with previously reported data. Newly manufactured fiberglass RAS had a mat content (2%), while only newly manufactured organic and recycled organic tear-off RAS had a felt content (10% to 12%). The tear-off RAS had similar properties to the organic-backed RAS. This was a function of the predominance of organic-backed shingles used in the older roofing systems. Roofing shingle binder, like paving grade asphalt binders, aged with time and exposure to ultraviolet (UV) light and oxidation. The effect of aging of shingle properties was sum- marized by Bauman (2005; Table 38). Gevrenov (2007) provided a summary of the use of asbes- tos in the manufacturing process (Table 39). The asbestos content was one of the main environmental concerns when using tear-offs in highway applications. Tear-offs contained a range of roofing products in the mix. This variability was increased when the new roof was installed over the old material. In some cases, older backing materials used asbestos in the felt manufacture. Shingles manufactured between 1940 and 1973 contained asbestos fibers, which may be a concern when using tear-offs in highway applications (Marks and Petermeier 1997). As noted by the Vermont Agency for Natural Resources (VANR) (1999) there were inconsistencies in the literature on the pres- ence of asbestos in RAS. engineering properTies The preferred size of the shredded roofing material will vary by agency. The Texas DOT requires that 100% of the shin- gle shreds pass the 19 mm sieve and 95% pass the 12.5 mm sieve (VANR 1999). The Georgia DOT requires that 100% of the shingle shreds pass the 12.5 mm sieve; this agrees with the FHWA recommendation of less than 12.5 mm. Other competing landfills and transfer stations. A location near the HMA contractor’s plant was always a good choice. Usage location should be close to RAS location. Decker (2002) noted that urban distances for economical hauls were usually within 25 to 40 miles of the recycler. Decker (2002) noted that grinding will typically require two operators for safe operation. physicAl And cheMicAl properTies Physical and chemical properties of RAS depend on the manufacturer and the roofing application (VANR 1999). Examples of the variation in the reported material content of shingles are shown in Table 36. The asphalt content of the shingles is dependent on the type of backing; fiberglass back- ing requires less asphalt than organic backing. The amount of mineral granules varies from 20% to 50%. Brock (2007) reported on the composition of new RAS as the percent of material per 100 square feet of shingles (Table 37) compared with a sample of tear-offs. The organic shingle manufacturing process used significantly more asphalt and less mineral filler than fiberglass-backed shingles, which Component VANR (1999) Sengoz and Topal (2005) CIWMB (2009) Organic shingles Fiberglass shingles Fiberglass shingles Organic shingles Fiberglass shingles Asphalt 30%–35% 15%–20% 32.5% 30%–36% 19%–22% Backing 5%–15% 5%–15% 2.5% 2%–15% 2%–15% Mineral Filler 10%–20% 15%–20% 20% CaCO2 8% to 40% with 90% smaller than 0.15 mm and 70% smaller than 0.08 mm Typically limestone, silica, dolomite, etc. Mineral Granules 30%–50% 30%–50% 35% basalt 20% to 38% of sand sized particles Ceramic coated natural rock TABlE 36 TyPICAl REPORTED COMPOSITION OF SHINGlES After Brock (2007). Component Percent of Component in 100 ft2 of Shingles Organic Fiberglass Tear-offs Asphalt 30 19 31 Filler 26 40 25 Granules 33 38 32 Mat 0 2 0 Felt 10 0 12 TABlE 37 ROOFING SHINGlE COMPOSITION

30 engineering properties will depend on the amount, size, and application for the RAS. environMenTAlly relATed properTies There are several possible exposure pathways for RAS con- taminates to the environment that are grinding (e.g., inhala- tion) emissions into the air as the material moves through hot highway applications (e.g., HMA plant), and leaching into water supplies (Gevrenov 2007). Contaminates of concern are asbestos and polyaromatic hydrocarbons (PAHs). Asbestos The Georgia DOT reported the use of asbestos in shingles as late as the 1980s (VANR 1999). The California Integrated Waste Management Board (CIWMB) reported that the asbes- tos content of shingles manufactured in 1963 was 0.02%, which decreased to 0.00016% in 1997 (VANR 1999). Other roofing products such as sealants used around pipes and chimneys could also contain asbestos; however, if it is pres- ent, it was in very low concentrations of 0.8% (Marks and Petermeier 1997). Communications between the VANR and members of the roofing industry indicated that asbestos was confined to commercial built-up roofing, older roofing coat- ings, and roofing cement; asbestos content was considered rare. Because of the health concerns, the Iowa DOT tested shingles for asbestos content starting in 1994. A total of 368 samples were tested, with only 3 samples testing positive. In 1996, the EPA of Region VII in Kansas City responded to an inquiry by the Iowa DOT indicating that the National Emis- sion Standards for Hazardous Air Pollutants (NESHAP) regu- lation identified and controlled asbestos-containing materials (Marks and Petermeier 1997). The letter also indicated that tear-offs coming from four or fewer units would be exempt from the NESHAP standard; however, shingles coming from a recycling facility would require testing for asbestos con- tent. Any material containing more than 1% asbestos could not be used for roadways. In 1996, the Iowa Department of Natural Resources (DNR) provided guidelines for landfills on the acceptance of tear-off Shingle Type Misc. Attributes Weather Aging Organic Felt Backing (cellulose, wood fiber) Tear resistant Less brittle in cold weather Components break down, crack, and curl Fiberglas Felt Backing Lighter, cheaper ($45–$60/sq) More cohesive in heat Components break down, crack, and curl Laminated Shingles Thicker more expensive ($100/square) More durable than traditional shingles Slower break down Roll Roofing (organic) Similar to organic shingle Roll Roofing (fiberglass) Similar to fiberglass-backed shingle After Bauman (2005). Source: Reference USA Business Disc, Info USA Library Division, www.referenceusa.com. “Elements of Roof Repair,” Canadian Home Workshop, by Martin Zibauer. Asphalt Shingle and Coating Manufacturing: 2002 (issued Jan. 2005). TABlE 38 GENERAl WEATHERING AND AGING CHARACTERISTICS OF TEAR-OFFS After Gevrenov (2007). Years Manufactured Product 1891 through 1983 Asphalt–asbestos shingles, rag–felt shingles, fibrous roof coating, shingle tab cement, roof putty 1906 through 1984 Asphalt roof coating and other miscellan eous mater ials 1920 to 1968 Roof paint, roll roofings with asbestos-containing base sheets, caulking com pounds, plastic ce me nts, taping, and finishing com pounds 1930 through 1977 Paper and felt 1941 through 1981 Roofing and shingles Early 1930s through 1976 Adhesives, coatings, sealants, and mastics Dates not available Asphalt–asbestos roof felt Asphalt–asbestos shingles, asbestos finish felt, mas tic Roofing asphalt Asbestos surface coating for shingles Asbestos surface coatings for shingles TABlE 39 USE OF ASBESTOS IN ROOFING SHINGlE MANUFACTURING

31 shingles. The DNR stated that landfills “are prohibited from accepting any shingle wastes that will be crushed, broken, or ground on-site per federal NESHAP regulations. . . . unless the generator or hauler provides lab certification that the shin- gle waste does not contain asbestos-containing material.” Zickell (2003) reviewed a large number of tests to determine the extent of asbestos in tear-offs (Table 40). Of 1,771 samples tested, only 3 shingle, 1 felt, and 1 ground product samples showed asbestos content of 2% or greater. This was 0.2% of all samples tested. Schroer (2007) listed environmental concerns, other than asbestos, as air emissions impacts from tear-off RAS in HMA plants, PAH and other particulates, runoff from whole shin- gles and RAS stockpiles, and runoff from RAS used as ground cover or dust control. The CIWMB (2009) noted that asbestos was not present in current roofing products, but that the tear-off RAS may contain very small amounts in the waste stream up until about 2016. The CIWMB noted the following regulations for asbes- tos that might be considered when using tear-off byproducts in California: • U.S. EPA • California EPA • Air Resources Board • Department of Toxic Substances Control. Other regulations that need to be considered are those from the Occupational Safety & Health Administration (OSHA), which regulates friable and nonfriable asbestos over 0.1%; CalOSHA; and other city and county health department requirements. polyaromatic hydrocarbons Because asphalts naturally contain PAH compounds, it fol- lows that shingle byproducts will as well (Gevrenov 2007). Research has shown that PAHs were not readily leached from shingles, and studies of PAH in leachate from virgin roofing asphalt, RAP, and runoff from asphalt pavements originally showed PAH levels below laboratory detection limits. How- ever, some of the regulatory limits have decreased, which implies that additional data are needed to detect the new, lower concentration levels. cosTs Although the tabs from RAS have alternative uses, the fac- tory scrap is commonly landfilled at costs ranging from $18 per ton to as much as $100 per ton. Haul distances can be up to 300 miles (Brock 2007). Marks and Petermeier (1997) reported that the disposal fee in Iowa for landfills accept- ing roofing tear-offs was $40 per ton. The asbestos testing was estimated at $12 per ton and grinding at about $18 per ton, leaving a margin for profit (or reduced costs) of $10 per ton. Their conclusion was that it was cost-effective to use the tear-offs for dust control for rural aggregate roads. Bauman (2005) reported that in Massachusetts the dis- posal costs could be as much as $115 per ton but the recycling fees are from $75 to $85 per ton, making recycling financially advantageous (Table 41). Gjerde (2004) noted that Minnesota contractors were see- ing a savings in virgin asphalt and aggregate costs from $0.50 to $1 per ton of finished HMA. The shingle processing costs were from $12 to $15 per ton of whole shingle scrap feedstock at a production rate of 20 to 30 tons per hour and maintenance costs were a significant factor in the shingle processing. Another Minnesota recycled shingle provider charged $15 per ton to accept shingles (manufacturer byproduct), which they then processed for use in HMA applications (Krivit 2008). Other costs that needed to be considered in the overall recycler costs were the modifications to operations that need to a include dust shroud installation, and added repair and maintenance costs as shingles were abrasive and shortened the life of the grinder. Krivit (2008) noted that Minnesota tipping fees from 2007 ranged from $16.00 to $43.00 per ton, with the average being $32.20. Krivit noted previous research that showed a tipping fee of $50 per ton appears to be the price that stimulated the industry to take additional action for the byproduct reuse. Using 5% RAS (manufacturer) resulted in a cost savings of After Zickell (2003). Material Analyzed Number of Samples with Given Level of Asbestos Detected None Trace 2% 5% Total samples tested Shingles 1,625 8 3 0 1,636 Felt 109 0 0 1 110 Ground Products 23 1 0 1 25 Total 1,757 9 3 2 1,771 % of Total 99.2 0.5 0.17 0.11 100 TABlE 40 SUMMARy OF ANAlyTICAl RESUlTS After Bauman (2005). Shingle Type 2002 Sales Organic Felt Backing (cellulose, wood fiber) $280,053 Fiberglas Felt Backing $392,652 (225 lb) $540,167 (other) $932,819 (total) Laminated Shingles $1,382,881 Roll Roofing (organic) $387,561 Roll Roofing (fiberglass) $182,728 TABlE 41 ExAMPlE OF SHINGlE PRODUCTION COSTS IN MASSACHUSETTS

32 between $0.50 and $1.00 per ton of HMA (typical non-RAS HMA cost $30/ton in Minnesota), which translated into a savings of between 1.5% and 3.3% in cost. The National Asphalt Pavement Association (NAPA 2004) noted 5% of RAS typically reduced the demand for virgin asphalt by 0.5% of total weight of mix. At $197.5 per ton in October 2004 for asphalt (per Texas Bituminous Index) would result in a savings of $7.16 per ton of HMA. At the April 2010 cost of asphalt of $500.45 per ton, 5% RAS would save $18.14 per ton of HMA. Zickell (2003) noted that the grinding, sorting, testing, housing, regulatory, and administrative costs exceeded $39 per ton. When the tipping fee was in excess of $50 per ton, it was cost-effective for the facility to recycle the waste stream. The sales of fiberglass-backed shingles were about double that of the organic-backed. However, the newer laminated shingle byproduct was the current best-selling product. The author stated that an additional category of byproducts with a different range of properties will be needed in the coming years. Brock (2007) estimated the potential for cost savings to the HMA contractor when using various types of RAS (Table 42). Because of the different components in the various types of shingles, the total unit cost of the components varied. Also, because the optimum HMA binder content was different for each combination of aggregate, additives, and binder, the sav- ings to the contractor for using RAS also varied. This table shows that using either the organic-backed or tear-off RAS provided the most binder replacement savings to the contractor. However, this can be expected to gradually change with time as more fiberglass-backed RAS enters the tear-off waste stream. usAge And producTion A review of the literature in 1999 by VANR showed the annual production of manufacturing RAS ranged from 0.5 to 1.0 mil- lion tons per year. Tear-offs removed from buildings each year generated between 7 and 9 million tons per year. Bauman (2005) reported that Massachusetts estimated the annual market for post-consumer shingles as: • 82,653 tons, assuming 10% post-consumer shingles in road surface and base. • 27,334 tons, if shingles consumed in the state included 10% post-consumer content. • A combined diversion of 47.5% of the estimated volume of shingles generated in the state. • More than 210,000 tons of shingles discarded per year. Gjerde (2004) reported that roofing manufacturers in Minnesota generated between 40,000 and 50,000 tons of roofing shingle scrap annually. Between 20% and 40% of this scrap was recycled into highway applications in 2003. At the same time approximately 400,000 tons per year of tear- offs were 100% landfilled. Two of the three roofing manu- facturers had contracts to manage their shingle waste, which Gjerde reported as being well accepted in HMA applications by counties, cities, townships, and private customers. Krivit (2008) reported the production of RAS in Minnesota to be about 70,000 tons of manufacturing byproduct each year with the use in HMA at about 40,000 to 60,000 tons per year. There were 227,000 tons of tear-offs generated each year, with about 166,000 tons per year being landfilled. Krivit proposed that Minnesota strive to obtain a recovery rate of 50% of the tear-off material by 2012 as a goal for Minnesota’s recycled shingle byproduct program (see Table 43). Agency survey resulTs RAS was most commonly used in HMA applications. Two states were using the byproducts in asphalt cement or emulsion applications. Three states listed “other” uses, which were noted as being in geotechnical applications (see Figures 11a–c). Table 44 shows the states using each roofing byproduct in one or more applications. Maine and Virginia were the only Component Unit Cost Per Ton Organic Fiberglass Tear-offs Value of Components Asphalt $400 $120.00 $76.00 $124.00 Filler $10 $2.60 $2.80 $2.50 Granules $10 $3.33 $2.66 $3.20 Mat $10 $0.00 $0.14 $0.00 Felt $10 $1.00 $0.07 $1.20 Total $440 $126.93 $81.67 $130.90 Opt. HMA Binder Content Value of Asphalt in RAS to Contractor 4% $5.68 $3.86 $5.76 5% $7.10 $4.83 $7.19 6% $8.32 $5.80 $8.62 After Brock (2007). Value of binder to contractor based on using 5% RAS. TABlE 42 COMPONENT COSTS AND POTENTIAl SAVINGS IN ASPHAlT

33 Question: Manufacturing or Misc. Construction Byproducts: Is your state using, or has ever used, these byproducts in highway applications? Roofing shingles, fiberglass backed: byproduct from production of fiberglass-backed roofing material Roofing shingles, paper backed: byproduct from production of paper-backed roofing material Roofing shingles, tear-offs: construction debris from reroofing or demolition of existing structures Type of Roofing Shingle Byproduct Asphalt Cements or Emulsions Crack Sealants Drainage Materials Embankments Flowable Fill HMA Pavement Surface Treatments (non- structural) PCC Soil Stabilization Roofing Shingles, Fiberglass Backed 1 0 0 0 0 14 0 0 0 Roofing Shingles, Paper Backed 0 0 0 0 0 13 0 0 0 Roofing Shingles, Tear-offs 1 0 0 0 1 12 0 0 1 Roofing Shingles, Unknown Type 1 0 0 0 4 1 0 0 0 Roofing, Built Up Roofing 0 0 0 0 0 0 0 0 0 TABlE 43 USE OF ROOFING SHINGlE ByPRODUCTS IN HIGHWAy APPlICATIONS states using roofing byproducts in two applications. Each of the other states only used these byproducts in a single appli- cation. Fewer agencies were using tear-offs than either of the manufacturing byproducts. No states were considering or using BUR byproducts in any highway applications. Agency comments note that the performance of HMA with roofing byproducts is either satisfactory or slightly improved in the case of rut resistance (Table 45). A number of agencies are currently working on specifications and/or special provi- sions for allowing RAS in HMA. Some agencies that cur- rently allow RAS use report limited use by the contractors. Applications—bound Hot Mix Asphalt Decker (2002) provided a detailed evaluation of shingle byproduct processing and introduction of the shingle byprod- ucts into the HMA plant. He noted his experience with two types of shredding methods, which were a conventional mill- ing head and an anvil method. The shredding methods had a problem processing the granular material as neither is designed as an aggregate crusher. The anvil approach appeared to mini- mize the oversized material, which results in a lower amount of rejected material. Shredding production rates depended on the type of shredder, with typical rates ranging from 25 to 100 tons per hour. Care was needed so that other rock con- taminates were not included in the material to be shredded, because this will significantly decrease the life of the shred- ding equipment. Grapple hooks were found to be the best method of introducing the shingles into the shredder. This minimized contamination and provided better control of the material being fed into the shredder. Water could be used to cool the shredder head and for dust control. However, this could be a problem for HMA produc- tion since a 1% increase in moisture content will increase the production costs by about 10% because of the additional drying time needed. Stockpiled shredded RAS agglomerated over time and, once shredded, the shingle stockpile needed to be kept clean. Decker recommended not shredding any more than can be used in a two-week period to minimize additional moisture content that could slow production. Introduction of the shingles into the HMA production could be accomplished by blending with RAP or crusher fines and added through the RAP port in the HMA plant (Decker 2002). This location in the HMA plant would keep the RAS away from the flames used for drying. The RAS should be in the plant long enough for the roofing asphalt to get soft, which requires some experimentation with the plant operation to determine the optimum time. Mix temperatures might need to be raised by about 5°F to accomplish the soft- ening. The HMA plant also needed to be cleaned more fre- quently when using RAS in the mixes. In Turkey, Sengoz and Topal (2005) investigated the use of tear-offs in HMA. The percents of byproduct used in the study mix were 1%, 2%, 3%, 4%, and 5% and the

34 shingle, which was attributed to the RAS being easier to compact and the filler effect from the RAS. The optimum asphalt content was reduced by 0.5% asphalt at 1% of shingle content. This indicated that a cost savings as a function of the reduced amount of asphalt needed could be obtained. Rut testing was conducted using mixes with 1% of byproduct using the French laboratoire Central des Ponts et Chaussées (lCPC) loaded wheel rut tester. Table 46 shows an improve- ment in the rutting resistance of the mix, even at the low 1% of addition. Schroer (2007) listed the factors associated with using RAS in HMA that will ultimately influence the performance of the application as: • Aggregation of the RAS • Properties of the final blended binder • Type of binder in the RAS • Type of virgin binder • Where the RAS is introduced into the HMA drum mixer • Mix temperature • Moisture content of the RAS and other aggregates • Retention time in the HMA drum. low temperature cracking problems generated by stiffening the binder with the addition of RAS can be countered by using less RAS (i.e., 2% or 3% instead of 5%), using a softer grade of virgin asphalt, and setting a minimum amount of virgin binder to be used, regardless of the performance grade (PG) of the binder. Maupin (2008) noted that the incentive for using recycled materials in Virginia came from Virginia Senate Bill 469 in the mid-1990s, which directed the formation of a Recycled Materials in Highway Construction Advisory Committee to provide recommendations for the use of recycled materials in highway applications. This resulted in the development of a draft specification for RAS to be used in HMA, which focused on manufacturing waste because it would pro- vide more consistent material properties than tear-offs. The recent fast increase in the cost of asphalt encouraged a North Carolina contractor to request approval to use RAS in HMA in 2006. Test sections were constructed over 4.1 miles of rural two- lane road with a surface mix containing 5% manufacturing shingle byproducts. For comparison, additional test sections containing 10% RAP (no RAS) in the surface mix were placed. The mix was a 9.5 mm HMA with a PG 64-22 binder designed with a gyratory compactor using 65 gyrations by the contractor. A limited number of visual inspections were per- formed to determine that the size of the RAS met the 0.5 in. maximum requirement. The mix variables used in the study are shown in Table 47. The Superpave gyratory mix design volumetrics are shown in Table 48. HMA mixes were evaluated to determine a desirable level of roofing byproduct. Results showed that the Marshall stability decreased with an increasing percent of RAS. At a shingle content of 3% or higher, the stability values were lower than for the control mix, but the flow values did not noticeably change. Air voids were lower for mixes with FIGURE 11 State agencies using roofing shingle byproducts: (a) roofing shingles fiberglass backed; (b) roofing shingles, paper backed; (c) roofing shingles, tear-offs. 1 1 1 1 1 1 1 DC-1 1 1 1 1 1 1 1 1 1 1 1 1 1 CT-1 DC-1 1 1 1 1 1 1 (a) (b) (c) 1 1 1 2 1 CT-1 DC-1 DE-1 1 1 1 1 1 2

35 State Comment AL Roofing shingles (manufacturing waste) is routinely used in HMA. Tear-off shingles are allowed by specification, but are not currently being used by contractors. The perfor ma nce of HMA pave me nts containing roofing shingles has been satisfactory. FL Shingles have only been used a few tim es. Econom ics and performance have prevented widespread use. IA Just starting with tear-off shingles using 5% limit at this time. KY The availability of roofing shingles for incorporation into HMA has been sporadic in Kentucky. This inconsistent supply hinders the usage of roofing shingles by those few contractors that are equipped to use this material. Also, the incorporation of higher contents of roofing shingles (e.g., more than 5%) normally requires a softer virgin asphalt binder. So me softer virgin binder grades (e.g., PG 58-28) are difficult to obtain in this region. MO Most agencies have trouble with acceptance of processing tear-off shingles, while it was brought to MoDOT by a contractor and the Department of Natural Resources. NC No problem with shingles in HMA; however, there are environm ental concerns with using tear-off shingles. NH Currently working on a specification to allow the use of recycled asphalt shingles on our highway project. NJ Have allowed the use of roofing shingles (pre-consu me r) in HMA-base and interm ediate courses for mo re than 15 years; however, there is not wide use. SC The recycled materials (RAP and shingles) show additional rutting resistance in laboratory tests. QC requires very close m onitoring of stockpiled shingle mate rial, especially tear-off shingles, by the contractor. TX Special provision recently approved allowing use of post-manufactured and post-consumer recycled shingles. WA The shingle industry has not satisfactorily answered why this product cannot be reused into new shingles. TABlE 45 AGENCy COMMENTS ON USING RAS IN HIGHWAy APPlICATIONS Number of Applications States Fiberglass backed Paper backed Tear-offs Unknown type Built up roofing (BUR) 2 — — ME, VA — — 1 AK, AL, DC, FL, ID, IL, KY, LA, MO, NC, NV, NY, OH, OR, WV AK, AZ, CT, DC, FL, KY, LA, MO, MS, NC, NY, OH, OK, VA AK, AZ, CT, DC, DE, ID, KY, MO, NY, OH, OK AL, MO, SC, VT, WI — TABlE 44 AGENCIES USING ROOFING SHINGlE ByPRODUCTS IN HIGHWAy APPlICATIONS laboratory testing included determination of the core density (AASHTO T166) and ignition oven testing was used to determine the asphalt content of the mix. Results indicated similar volumetrics for both mixes. Field testing included the use of nuclear density testing using a thin lift gauge and a 60-s count to establish the required rolling pattern. This testing was in addition to the standard density testing requirements. VDOT required the density be at least 92.5% of the maximum theoretical specific gravity. Fatigue testing (AASHTO T321) at 400 and 800 micro- strain with failure defined as a loss of 50% of the initial stiff- ness as well as the endurance limit were also determined. The endurance limit is defined as the strain at which the specimen can endure an infinite number of cycles and is a value projected from the fatigue testing data (Table 49). The results showed no practical difference in the endurance limits between the mixes. Rut testing (VTM 110) was accom- plished using a loaded wheel rut tester, which limits the maximum rut depth to 0.25 in. The RAP mixes were border- line, whereas the shingle mixes were rated as satisfactory by VDOT. Permeability testing (VTM 120) limits the maximum allow- able permeability to 150 × 10-5. Permeability was an average of 83 × 10-5 and 98 × 10-5 cm/s for the RAP and shingle mixes, respectively. Two of 10 RAP cores exceeded this limit, while 4 of 10 shingle cores exceeded the limit. The cores with the highest permeability also had the highest air voids. The con- clusion was that the air voids need to be less than 9% in order to meet the maximum permeability limit. TABlE 46 RUT TESTING RESUlT FOR HMA WITH 1% TEAR-OFF RAS Number of Passes LCPC Rut Depths, in. 60/70 Pen AC with 1% RAS 60/70 Pen AC HMA Mix 300 0.07 0.17 1,000 0.11 0.28 3,000 0.13 0.41 10,000 0.16 0.64 30,000 0.29 — 50,000 0.41 — After Sengoz and Topal (2005). LCPC = Laboratoire Central des Ponts et Chaussées.

36 Mix Percentage Material Source RAP Mix 42 78M Vulcan Materials, Skippers, Va. 10 Fine RAP Rose Brothers, Murfreesboro, N.C. 19 Coarse sand Rose Brothers, Grit Pit, Rich Square, N.C. 29 Regular screenings Vulcan Materials, Skippers, Va. 5.5 PG 64-22 binder Koch Materials, Newport News, Va. 0.25 Adhere HP Armaz, Vanceboro, N.C. Shingle Mix 45 78M Vulcan Materials, Skippers, Va. 5 RAS Certain Teed Corporation, Oxford, N.C. 27 Coarse sand Rose Brothers, Grit Pit, Rich Square, N.C. 23 Regular screenings Vulcan Materials, Skippers, Va. 5.8 PG 64-22 binder Koch Materials, Newport News, Va. 0.25 Adhere HP Armaz, Vanceboro, N.C. After Maupin (2008). 78M = aggregate size designation; Adhere HP = anti-stripping additive. TABlE 47 VARIABlES IN FIElD SECTIONS Property Recycled Asphalt Pavement Mix Shingle Mix Mix Design, 65 Gyrations VTM, % 3.6 3.6 VMA, % 16.1 15.9 VFA, % 77.8 77.5 Roadway, Post-construction Air voids, % 7.9 8.0 After Maupin (2008). VTM = voids in total mix; VMA = voids in mineral aggregate; VFA = voids filled with asphalt. TABlE 48 VOlUMETRIC PROPERTIES: MIx SAMPlES AND PAVEMENT CORES After Maupin (2008). Mix Sampling Time Endurance Limit at 50 x 106 cycles, µ Rut Depth, in. RAP Morning 182 0.28 Afternoon 167 0.28 Shingle Morning 152 0.25 Afternoon 222 0.20 TABlE 49 FATIGUE AND RUT TEST RESUlTS Moisture sensitivity was evaluated by determining the tensile strength ratio. Both mixes contained about 70% of crushed granite known to be susceptible to stripping and 25% sand with no known stripping problems. A liquid antistrip (0.25%) additive was used in both mixes. Both mixes per- formed satisfactorily. Superpave binder testing on the Abson (AASHTO T170) recovered binder (Table 50) was performed. The virgin binder used was a PG 64-22 and the recovered binder was graded as a PG 70-22 with the shingle mix having greater warm temperature stiffness, but not enough to change the grading. This difference could account for the better rut resis- tance of the shingle mix. Comments on the construction of the pavement noted that both mixes were slightly tender during rolling. The finish roller needed to be delayed until the mixes had cooled suf- ficiently so that the material was not pushed during rolling. Performance observations after 18 months in service showed both sections were performing well, with negligible signs of distress cracking. A cost/benefit assessment indicated that an estimated 50,000 tons of HMA could be supplied to the Hampton Roads District per year, with a cost savings of as much as $2.69 per ton. Recommendations from the research were to develop a provisional specification to allow manu- facturing shingle byproducts in HMA and to assess the pos- sibility of using tear-offs in the future. Schultz (2010) evaluated mix design methods and needed Oregon DOT specification changes for mixes using RAP and RAS. Oregon DOT was allowing the use of up to 30% RAP without adjusting the PG grade of the asphalt, and above 30% the use of blending charts was needed to select the grade. In 2009, the Oregon legislature introduced a bill that would require the use of up to 5% RAS in HMA. The major concern of Oregon DOT engineers was that too much RAP and/or RAS would significantly reduce the performance of the pavements resulting in early failures and/or undesirable increases in maintenance, repair, or rehabilitation costs. This research was to be used to address this concern. The research program evaluated the impact RAP, RAS, and RAP/ RAS combinations would have on the Superpave PG binder specification grade. In the Superpave binder specification, the grades change in six degree Celsius increments and the

37 After Maupin (2008). Binder Properties Virgin Binders Mix with 10% RAP (recovered) Mix with 5% RAS (recovered)RAP mix Shingle mix No Lab Aging G*/sin δ , kPa > 1.0 1.282 at 64°C 1.333 at 64°C — — 0.630 at 70°C 0.663 at 70°C — — Rolling Thin-Film Oven G*/sin δ, kPa > 2.20 4.014 at 64°C 3.648 at 64°C 4.546 at 64°C 6.943 at 64°C 1.884 at 70°C 1.710 at 70°C 2.252 at 70°C 3.447 at 70°C — — 1.145 at 76°C 1.758 at 76°C Pressure Aging Vessel G*sin δ, kPa < 5,000 3026 at 22°C 3255 at 22°C 2413 at 25°C 2298 at 25°C 2113 at 25°C 2259 at 25°C 1682 at 28°C 1647 at 28°C Creep Stiffness, MPa < 300 128 at −12°C 129 at −12°C 126 at −12°C 113 at −12°C — — 257 at −18°C 243 at −18°C m-value, > 0.300 0.319 at −12°C 0.314 at −12°C 0.322 at −12°C 0.312 at −12°C — — 0.287 at −18°C 0.283 at −18°C TABlE 50 BINDER PROPERTIES FOR FIElD TEST SECTIONS WITH AND WITHOUT SHINGlE ByPRODUCT TABlE 51 CRITICAl HIGH AND lOW TEMPERATURES FOR VARIOUS PERCENTAGES OF RAS Virgin Binder Grade Percent of Reclaimed Material in Mix Percent Virgin Binder Replacement from RAS 0% (i.e., no RAS) 20% 40% 60% 80% Critical Temperature, oC High Low High Low High Low High Low High Low PG58-22 59 −28 73 −25 108 −17 105 −1 123 8 PG52-28 56 −31 64 −28 80 −19 99 14 126 Too stiff PG58-28 60 −30 73 −24 78 -14 107 2 123 43 No RAP; after Schultz (2010). PG grade changed one grade for every 6oC change in critical temperature. temperatures represent the environmental conditions under which the binder will need to perform. For example, a PG 58-22 needs to be stiff enough to resist rutting when the aver- age summer temperature is 58°C and resist thermal cracking at -22°C in the winter. The critical high temperature indi- cates that the test temperature above which the binder has a complex modulus divided by sind (i.e., G*/sind of less than 2.2 kPa). The critical low temperature indicates the lowest temperature the mix can withstand without significant ther- mal cracking occurring. The data from this research program showed that the binder for RAS mixes with various percentages of RAS will be very rut resistant (Table 51). However, they also showed significant early thermal cracking distresses at mild tempera- tures. For example, at 40% RAS the critical low temperature was -14°C and increased to 43°C or warmer at 80% RAS. The typical low temperature requirement for the Oregon cli- mate was approximately -28°C to -31°C. Therefore, at 40% RAS, the mix could be expected to exhibit significant ther- mal cracking. Schultz (2010) also compared the Oregon data with similar research conducted by both Ohio and Minnesota (Table 52). Since each grade change represents a shift in the temperature of 6°C, a change in the high temperature of two grades would represent a grading change from PG 58-xx to PG 70-xx. Conversely, a one grade change in the low temperature would mean a PG xx-22 would be changed to a PG xx-16. The findings showed that mixes with RAS should limit the amount of RAP to low levels or the grade of the virgin binder changed to a softer binder. Conclusions from the Schultz (2010) study were that the use of RAS increased both the high and low PG grade temperatures relative to the virgin binder. The use of both RAS and RAP in the same mix also increased both temperatures, up to about 30% RAP, when there was no further increase in the low temperature grading. The high temperature grade increased for the 30% to 40% RAP-only mixes and was similar to mixes with only 5% RAS (i.e., no RAP). The study identi- fied a need for: • Improved batching and mixing procedures for RAP/ RAS mixes; • Development of an improved binder extraction procedure; • A modified method for determining asphalt content using the ignition oven;

38 TABlE 52 CHANGE IN PG GRADE REPORTED IN OHIO AND MINNESOTA RESEARCH Mixture RAP, % RAS, % Change in High Temp Grade Change in Low Temp Grade Resulting PG Grade Ohio DOT Study 10 5 (tear-offs) 0 0 — 20 5 (tear-offs) 2 1 — MnDOT Study 15 5 (tear-offs) 2 0 — 15 5 (manufacturer) 2 1 — Oregon Study 0 0 –1 0 PG 64-28 0 5 3 1 PG 88-22 10 5 0 0 PG 70-28 20 5 2 1 PG 82-22 30 5 3 2 PG 88-16 40 5 3 2 PG 88-16 50 5 2 2 PG 82-16 McGraw et al. (2007); Schroer (2007); Schultz (2010). • QC/quality assurance (QA) procedures for RAP/RAS mixtures, procedure for selecting PG grade of virgin binder for RAP and/or RAS mixes; • Performance mix testing; • A pilot study for field evaluation. Cold-Applied Asphalt Re-pave, produced by a Florida company, is a shingle product marketed as a pothole patching material, tried by New Jersey, but not currently available in bulk quantities for New Jersey use. This product is marketed commercially for residential use in 3.5 gallon buckets and can be found at home centers and hardware stores for residential use. Applications—unbound Aggregate/Dust Control Marks and Petermeier (1997) reported on Iowa’s experience with RAS as a roadway surface to control dust problems on a rural Benton County roadway. Tear-off roofing was collected and tested during 1994 and 1995 for asbestos content, then ground up at a rate of 40 tons per hour using a 2-in. screen. Initial work with a 1-in. screen resulted in a slow production rate of only 15 tons per hour. The grinding unit was equipped with a water spray system for dust control. The discharge con- veyor was fitted with a magnetic roller to remove most of the nails in the shingles. A total of 500 tons of ground RAS was spread on the crushed stone surface and a motor grader was used to mix the crushed stone and RAS into a mixture with a uniform texture. The finished surface mix was about 2.5 in. thick with a friable surface. In December 1995, the surface looked “open” and a fog seal using a CSS1 emulsion diluted with 1,000 gal. of water was applied (0.3 gal./yd2). This treatment of the rural roadway remained mostly dust free for more than two years. Three other states (Minnesota, North Carolina, and Maine) were identified in the Vermont agency report (VANR 1999) as having tried ground RAS as a dust control for unpaved sur- faces. Minnesota results indicated less dust was generated and the need for reapplication of dust suppressants was reduced. The driving conditions were improved on the unsurfaced roads. A North Carolina contractor was reportedly marketing scrap shingles as low-cost driveway and parking area surface treatment. A contractor in Maine was using tear-off byprod- ucts in a combined mix of RAS, aggregates, and asphalt emul- sion to produce a base or subbase material. Benefits noted for using tear-offs for dust control included that processing the shingles was only 75% of the cost of land- filling, shingle binder bound the aggregate that resulted in less loss of granular surfacing into the ditches, improved lat- eral control of vehicles, and a smoother, quieter ride. Hooper and Allen (Ahmed et al. 2009) developed a com- posite of RAS, RAP, and gravel (10:30:60) as surface mix. This mix was placed and compacted on a series of municipal roads and sprayed with calcium chloride solution. Over two years the composite resisted rutting and erosion. Soil Improvement Hooper and Marr (2005) conducted a study to determine the effects of adding RAS to soils on engineering properties. The results showed dependence of improvement was linked to the soil type being modified. The unbound materials used in the study were crushed stone gravel, silty sand, clean sand, and clay. The results showed weak soils such as clay bene- fited from the addition of 25 mm minus RAS by an improve- ment in strength. Strong materials such as crushed gravel, showed a loss of strength when RAS was added. Shrestha et al. (2008) evaluated the use of tear-offs in road base and unpaved gravel roads. The materials in the

39 study included two sizes of ground RAS: maximum size of the 75 mm and 40% passing the 4.75 mm, 100% passing the 4.75 mm sieve. The five types of aggregates used were crushed limestone, crushed natural gravel with 72% crushed particles, and three recycled concrete aggregates (RCA). The results showed that the maximum dry density decreased with the addition of RAS, but the decrease was not accompa- nied by a significant change in the optimum moisture content. The effect on strength was dependent on the initial CBR value of the unmodified aggregate or RCA base. The smaller size RAS (ground) improved the CBR values more than the larger sized RAS. This led to the decision to use only the ground RAS in the remainder of the experimental design. Adding ground RAS to materials with low CBR values improved the strength with the optimum improvement occurring at 5% RAS, after which the strength decreased with increased shingle content. Adding RAS to materials with initially high CBR values (crushed limestone and one RCA) decreased the strength of the mixes. Permeability was relatively unchanged by the addi- tion of the RAS to the base materials with the exception of the crushed limestone. In this case the permeability was notice- ably decreased at 5% ground RAS. General observations were that the higher the fines con- tents of the base materials, the more influence the RAS had on material properties. Materials that depend strongly on inter- locking, angular particles to achieve their properties were adversely influenced by the addition of RAS. Ahmed et al. (2009) in Ontario, Canada, investigated combining CKD and RAS to improve the properties of fine grained soils. Materials used in the study were CKD, RAS, and soil that was poorly graded (SP). The CKD was used to improve the strength and the RAS was used to improve the tensile strength of the composite soil–CKD. One source of CKD was used with three different sizes of RAS that were a small (passing 2.36 mm sieve), a medium (passing 4.75, but retained on 2.36 mm), and a large (passing 9.5 mm but retained on 4.75 mm). Testing evaluated the compressive and tensile strength, permeability (ASTM D2434), and CBR (soaked, unsoaked). The capillary rise indicating an increase in the frost susceptibility as the capillary water level rise increases was also evaluated. Results indicated that the soil–CKD (10%)–shingle (medium) compared with soil–CKD mix (Table 53) slightly improved the compressive strength of the mix up to a maxi- mum of 10% RAS, after which the strengths decreased. Signif- icantly improved tensile strength was seen, with the optimum strength occurring at 10% RAS. Results for soil–CKD (10%)– RAS (different sizes) compared with soil–CKD (Table 54) showed that the unconfined compressive strength increased with decreasing size. The tensile strength increased with increasing size of shingle, which was opposite of the com- pressive strength. CBR testing of soil–CKD–RAS (small), both the soaked and unsoaked, increased in value up to 10% RAS. Unsoaked CBR values for the 10% shingle mix were about 45, compared with soil–CKD CBR value of 20. Soaked CBR values were about 40 compared with 16, respectively. Capillary rise was represented by the time it took for the water to reach a certain height within the sample where long times mean less frost susceptibility. Results showed an increase in time with increased shingle content. Up to 60 min, any size TABlE 53 INFlUENCE OF VARyING PERCENTAGES OF MEDIUM-SIZED RAS ON RAS–CKD–SOIl (SP) PROPERTIES Percent Shingles Unconfined Compressive Strength, N/mm3 Splitting Tensile Strength, N/mm3 % Tensile Strength Improvement Compared with CKD–Soil Only 2.5 1.2 0.13 — 5 1.9 0.25 50 10 2.2 0.30 70 15 1.9 0.30 65 20 1.8 0.30 40 After Ahmed et al. (2009). TABlE 54 INFlUENCE OF VARyING RAS SIZED (10%) ON RAS–CKD–SOIl (SP) PROPERTIES Shingle Size Unconfined Compressive Strength, N/mm3 Splitting Tensile Strength, N/mm3 % Tensile Strength Improvement Compared with CKD–Soil Only % Unconfined Compressive Strength Improvement Compared with CKD–Soil Only Small 2.2 0.24 75 48 Medium 2.1 0.28 67 105 Large 1.7 0.3 41 118 After Ahmed et al. (2009). Note: estimated values from graphs in report.

40 of shingle significantly increased the time needed for a given height of capillary rise. After 60 min, the larger the shingle size the slower the rise. Permeability showed no noticeable differences between the soil–CKD mix and soil–CKD (10%)– shingle (small) with various shingle contents or with the same content, but with differing sizes. The conclusion from the research was that a combination of CKD and RAS improves the properties of silty subgrade soils. Although the CKD increased the compressive strength with increasing percentages, it had little influence on the ten- sile strength. When RAS was added to the mix, the tensile strength of the soils was significantly improved. The opti- mum shingle content was 10%. At 10%, the addition of the RAS improved the CBR, tensile strength, and compressive strength compared with the soil–CKD mixes. larger shin- gle sizes had more of an influence on the tensile strengths, whereas the small size had the opposite effect. The addition of RAS reduced the frost heave potential while not signifi- cantly influencing the permeability, specificATions As of 1999, five states had standard specifications for using manufacturing RAS byproducts, generally up to 5% by weight of aggregate, in HMA; Minnesota, Maryland, Georgia, North Carolina, and Indiana. The NAHB Research Center (1999) identified the stakeholders in recycling roofing shingle byprod- ucts as roofers, manufacturers, haulers, recyclers, governments and paving contractors. Schroer (2005) reported on the Missouri DNR efforts to use tear-offs in HMA applications. The project was a com- bined effort between DNR, MoDOT, a local recycler, and a paving contractor. The MoDOT specification for RAS in HMA was used for the pilot project. This specification lim- ited the amount of debris to no more than 3% by weight in the byproduct material before introduction into the HMA plant. A separate limit of no more than 1.5% wood was proposed for the specification. Asphalt properties of a virgin asphalt PG64-22 were required for the final HMA. At 5% RAS, the maximum allowable RAS, the contractor was required to use a softer PG58-28. Other (lower) percentages of RAS would require the contractor to submit a proposed job mix formula to MoDOT for consideration. The CIWMB (2006) fact sheet for RAS contained infor- mation on state specifications and standards such as the AASHTO MP15 for asphalt shingle use in HMA. This stan- dard allowed for the use of either pre- or post-consumer shingle byproducts. The AASHTO PP53 was a companion recommended practice. Other specifications identified in this document are summarized in Table 55. Only two specifica- tions (those of Michigan and Brampton in Ontario, Canada) allowed either manufacturer or tear-offs. Other states did not specify the type (Missouri, Ohio). Schroer (2007) noted on the subject of regulatory compli- ance that the recycler and contractor needed to be pro-active and assertive in planning, anticipate agency requirements, use precedents from existing recycling programs as a format, and document adequate market demand to avoid comments about “speculative” stockpiling. Schultz (2010) recommended the following changes to the current Oregon DOT Standard Specification Section 00745- Hot Mixed Asphalt Concrete (HMAC SP745): 1. Either pre-consumer or tear-off RAS can be used. 2. No more than 5% RAS by total weight of mixture should be allowed. The maximum allowable percent- age of asphalt binder replacement (i.e., either RAS or RAP binder) shall be restricted to 20% for base courses and 15% for wearing courses in HMAC containing RAS but not RAP. 3. The maximum allowable percentage of binder replace- ment from a combination of RAS and RAP should be restricted to 30% for base courses and 25% for wearing courses. 4. Process RAS by grinding at ambient temperature so that 100% of the shredded pieces are less than 1/2 inch in any dimension and that 90% are less than 3/8 inch in any dimension. 5. A minimum of one sample per 100 tons of RAS shall be obtained and tested for asbestos. 6. limit deleterious materials such as nails, glass, rubber, soil, brick, tars, paper, plastic, wood chips, metal flash- ing, etc., to 3.0%, by weight, of the stockpiled RAS as determined on material retained on the 4.75 mm (No. 4) sieve. TABlE 55 SUMMARy OF SPECIFICATIONS After CIWMB (2006). State Shingle Byproduct Amount Georgia Manufacturing 5% Maryland Manufacturing 5% Michigan Either 50% recycling specification; does not specifically address RAS in specification Minnesota Manufacturing 5% Missouri Not specified 5% New Jersey Manufacturing 5% North Carolina Manufacturing 5% Ohio Not specified Certain percentage Indiana Manufacturing 5% City of Brampton, Ontario Either 3%

41 7. limit lighter material such as paper, plastic, and wood to a maximum of 1.5%, by weight, of the stockpiled RAS as determined on material retained on the 4.75 mm (No. 4) sieve. 8. Fine aggregate may be added to the RAS in a quantity not to exceed 4% by weight of RAS to keep the material workable and to prevent conglomeration of the shingle particles in the stockpile. 9. Take the necessary steps to ensure that excessive mois- ture is not retained in the RAS stockpiles; only allow a maximum of 5% moisture. 10. When RAS is used in conjunction with RAP, no more than 20% reclaimed materials by total weight of mix- ture should be used. 11. For high traffic facilities with little tolerance for con- struction disruption, no more than 15% of RAS should be allowed. Restrict the maximum RAS to 30% for base courses and 25% for wearing 12. For HMA mixtures containing only RAS, the amount of asphalt cement in the RAS needs to be established in the mix design. 13. For HMAC mixtures containing RAP and RAS, the RAS shall be added to the RAP and tested to estab- lish the asphalt content of the combined reclaimed materials. 14. Adjustments for RAS content need to be within 1% of the original job mix formula. New provisional AASHTO specification R2005A-TS-2c (AASHTO 2010) and recommended practice (M2005A- TS-2c) for RAS in HMA were under review (Gevrenov 2007). These provisional standards addressed the need for detailed QC/QA guidance including RAS types, definitions, sources, and sampling. They also included guidance for RAS grada- tions, addition rates of RAS into HMA, deleterious sub- stances, and methods of sampling and testing. The draft of R2005-TS-2c (AASHTO 2010) Recom- mended Practice for Design Considerations when using RASs in new HMA provided recommendations relative to four areas: 1. Design consideration when using RAS in HMA 2. Determining the shingle aggregate gradation 3. Determining the virgin PG and percent of the virgin asphalt binder in new HMA 4. Determine the shingle asphalt binder availability factor. The shingle asphalt binder availability factor is calculated from the following equation: F P P Pc vav sab = -( ) ( )( )varsP Where: Fc = shingle asphalt binder availability factor; Pvav = binder content of virgin mix without shingles, %; Pvar = design binder content of the new mix asphalt with recycled shingles, %; Ps = recycled shingle asphalt in the new HMA, %; and Psab = shingle asphalt binder present in RAS, %. This draft practice indicated that after 0.75% by weight of asphalt binder contributed by the RAS the virgin asphalt PG grade specified may need to be changed. Because the size of the RAS was expected to influence the amount of binder contributed to the mix by the RAS, the mix design needed to account for the size to be used in the mix. The point of intro- duction of the RAS into the HMA plant needed to be selected so that damage to the RAS from excess heat was minimized. This needed to be balanced with sufficient heating to soften the RAS binder. The RAS aggregate gradation should be determined after extraction by either AASHTO TP2 or ASTM D228 (section 13 or 14). The AASHTO method was for the extraction and recovery of the RAS binder. If the binder did not need to be recovered, the ASTM method was recommended, which was the standard for the design consideration when using RASs in new HMA. The required PG (i.e., critical temperature) for the virgin binder was determined: T T T T Pva sb sb fbb sb = - - -1 Where: Tva = critical temperature of the virgin asphalt binder; Tsb = critical temperature of the shingle asphalt binder; Tfbb = critical temperature of the final blended binder (i.e., desired PG temperature); and Psb = percentage of shingle asphalt binder present in the final blended binder. The value of Psb was calculated as: P F P P Psb s sab fbb = ( )( ) ( ) Where: Ps = percent of RAS; Psab = percent of shingle asphalt binder in shingles; Pfbb = percent of final blended binder present in the new HMA; and F = shingle asphalt binder availability factor determined using F P P P Pc vav s sab = - var

42 Where: Fc = initial estimate of percentage of asphalt in blended mix; Pvav = design binder content of virgin HMA without RAS; and Pvar = design binder content of HMA with RAS. The practice noted that this estimate will result in an over- estimate of the critical design temperature of the virgin asphalt. The Illinois Tollway Congestion Relief Plan memorandum (Kovacs 2010) construction bulletin no. 20-01 was issued in January 2010. This bulletin provided guidelines for the use of tear-off RAS asphalt shingle recycling facility operators. Tear- offs were defined as roofing waste removed from residential buildings with four or fewer housing units. Asbestos testing was required prior to shredding the tear-offs. The document contained training slides for both the recycled shingle supplier and for their sorting personnel. environMenTAl benefiTs Krivit (2008) reported that the EPA preliminary assessment of using shingle byproducts would result in an energy sav- ings. For 300,000 to 400,000 tons of shingles recycled each year, an energy savings of between 60 and 80 million KWH per year could be achieved. For the same amount of shingles, the savings in greenhouse gases would be 44 to 50 tons of CO2 (0.27 to 0.29 lb of CO2 equivalents per ton of shingles). bArriers The CIWMB (2006) fact sheet for RAS noted several barri- ers to the increased use of shingle byproducts in California. The most widely used specifications were either the Califor- nia DOT (Caltrans) or the Standard Specifications for Public Works Construction (called the Greenbook). Caltrans did not allow shingle byproducts and shingle byproducts were also not allowed in the Greenbook. Work required by Caltrans to use byproducts included laboratory testing, preparation of a draft of Special Provisions, field testing and monitoring of test sections, and finalizing a Special Standard Provision. Work required to alter the Greenbook included the necessary submission by the local government(s) of field and labora- tory test results to the Greenbook committee for evaluation. The most promising market at the current time was identi- fied as working through local government public works. In California, the local government public works typically use either Caltrans or the Greenbook, but were free to use any specification of their choosing or to develop their own for local projects using local funds. Bauman (2005) developed a short list of factors influenc- ing the increased use of shingle byproducts, the anticipated impact of each factor, and the likely outcome for each factor and impact (Table 56). The factors identified as significant to increased usage were byproduct purchasing practices, tear- off disposal practices, byproduct material variability, and application performance. Bauman (2005) lists the following key lessons learned from the survey on the use of tear-off RAS: • If recycling is cheaper than disposal, the contractors will do it. • Successful implementation experiences are needed. • Highlight the advantages to agencies and contractors. Identify other byproduct generators that can join the effort to promote recycling. Schroer (2007) identified key barriers to increased use of RAS as the lack of clear industry standards and specifica- tions, inconsistent state regulations, inadequate information and technology transfer, and a lack of national leadership by private industry and government. Schroer noted that separa- tion of the tear-off RAS could be done either at the roofer’s job site or at a central processing shingle recycling facility. The author suggested that there be a required certification to document the chain of custody, a pre-approved customer list developed of certified suppliers, and that a permanent file of all supply certificates be maintained. Krivit (2007) prepared a best practices guide for roofing contractors to facilitate their ability to recycle tear-offs. Best practices focus on three major categories: 1. Development of a supply QC/QA program. 2. Optimize operations to produce RAS that meets or exceeds specifications for end markets. 3. Development of a marketing plan based on multiple outlets. The suggested the best practice for the roofer was to layer the tear-off materials with the RAS on the bottom of the dump- ster, followed by the roofing felt, then wood materials. Krivit (2008) developed a white paper to provide a bridge between technical research and development efforts and larger policy options for improved use of shingle byproducts. Phase I of the study for the Solid Waste Management Coordinating Board and the Minnesota Pollution Control Agency identified asphalt shingles as a high priority commodity that could be potentially recovered from the construction, demolition, and industrial waste stream as it comprises up to 15.2% of total waste sorted. In 2008, the Solid Waste Management Coordi- nating Board consolidated its new and post-consumer shingle recycling efforts into a comprehensive project (Phase II of the study). A history of the development of a recycling market for byproducts for RAS was included (Table 57). Changing

43 the specification from “job-by-job approval” to “use unless explicitly prohibited” significantly increased the use of shingle byproducts. Once contractors started using RAS, the higher RAS binder percentage in the total binder resulted in prema- ture cracking of one project, hence the 2006 amendment. Phase 2 was an outreach project designed to address the information needs of the private contractors and local agen- cies. This phase developed a guide to the use of RAS in road construction in 2002, which was a joint effort by MnDOT and the Minnesota Office of Environmental Assistance (now an office in the Minnesota Pollution Control Agency). This phase traced the lack of locally available RAS to a limitation on the use of shingle byproducts and led to the next phase of research into using tear-off RAS, which was significantly more available. Phase 3 was a co-sponsored research project between MnDOT and Recycled Materials Resource Center (RMRC) to investigate the use of RAS in other applications such as a dust control material, unbound aggregate supplement to base, and in a 5% concentration in HMA. TABlE 56 FACTORS THAT ARE CONSIDERED AS INFlUENTIAl FOR INCREASED USE OF TEAR-OFF RAS After Bauman (2005). MRF = material recovery facilities. Factor Impact Outcome Purchasing Practices Making institutional (i.e., agency) buyers aware of post- consumer content products and its performance against competitors is a key factor in entering the market. Worth noting: Mass Highway has not seen post-industrial content being used in pavement, although the specification allows for it. The highway spec. does not currently allow for post- consumer content in base or surface courses. Highly significant. The next section focuses on the single largest buyer. How Material Is De- installed Unlike other types of renovation, this is largely a one material (or two material) job. Source separation is relatively easy. If a laborer can tarp area to minimize yard waste and prevent trash from going into the load, all other contaminants (ice and water shield, shingle wrapping) are removed by MRF. The rest is ground into dust. Significant. Source separation is easy, but this corner of the industry is very traditional, so change will come slowly. The Complexity of the Material Shingles are composed of asphalt, stone dust, an organic felt or fiberglass backing, and adhesive. Unfortunately, sorting shingles into product types so that they can be used as feedstock for new shingles is not cost-effective. Significant for manufacturers accepting the material. This is a longer-term consideration. Predictable Supply of Feedstock Established shingle recyclers have their own markets and are able to aggregate volume in order to supply companies with the needed volume. Many aggregate companies also produce pavement and have a contracting division, which allows them to leverage cost savings for state jobs. Longer term, shingle recycling becomes more the rule than the exception, and manufacturers will have the confidence to invest in post-consumer feedstock processing. Less significant (but highly significant for shingle manufacturers). As long as the manufacturing process can adjust for volumes of post-consumer material in its “recipe,” this does not have to be a show stopper. Performance of Post- consumer Material Shingles generally last 20 years or more. Weather exposure decreases stone content and increases brittleness. Studies showed that the binding attribute of shingles was not diminished with time, although elasticity is (and is important for pavement). Not significant in the usability of the resulting feedstock. “Recipe adjustments” have accommodated the effects of aging. TABlE 57 HISTORy OF SHINGlE SCRAP RECyClING SPECIFICATION DEVElOPMENT Approximate Date Activity 1990–1996 MnDOT conducts original Phase 1 research projects 1996 MnDOT adopts first manufacturer’s shingle scrap materials specification for use on a job-by-job approval by the project engineer required basis 1998 (circa) MnDOT develops draft guideline on file with Bituminous Engineer 2003 MnDOT amends specification to allow HMA producers the discretion to use manufacturer’s shingle scrap by changing approval process from job-by-job approval to allow the use unless explicitly prohibited by the project engineer 2006 MnDOT amends specification to require a minimum of 70% virgin asphalt as the percent of the total binder within higher volume highways 2007 MnDOT develops special provision, mix design specifications allowing tear-off RAS in HMA according to the project QC/QA specifications After Krivit (2008).

44 suMMAry of roofing shingle inforMATion list of candidate byproducts The list of the most commonly researched and used byprod- ucts included: • Roofing manufacturer, • Tear-off shingles, and • Built-up roofing. Test procedures The test methods found in the literature and survey responses are shown in Table 58. Material preparation and byproduct Quality control The following post-processing and QC points needed to be considered: • Grinding of RAS could be easier and minimize agglom- eration of particles in colder weather conditions. • Shingles could be ground when needed rather than stock- piled for long periods of time. • Sand (up to 4%) could be added during the grinding process to minimize agglomeration. • Water may be needed to cool the cutting heads: – Moisture content determinations of the RAS stock- piles were needed before use. • Metals needed to be removed as the material is stock- piled. • Individual stockpiles could be used for each type of RAS byproduct. • Asbestos content testing may be needed for tear-off RAS. This was not a concern for current manufacturing byproducts. Materials handling issues The following materials handling points needed to be considered: • Dust mitigation needed to be addressed during RAS grinding operations. • Recycling operations might require state and/or local permits. Transformation of Marginal Materials Recent research focused on the use of RAS as a means of improving the stability of poor soils and as a method of dust control. Soil Improvement The use of 5% finer ground RAS significantly improved the CBR values of soils with initially low values. Improvements were seen in CBR, compressive strengths, and especially ten- sile strengths of the modified soils. The most improvement was seen when the soil had high fines content. A combination of RAS and fly ash worked well with silty subgrade soils. RAS was not a good choice for use with base materials with initially higher CBR value (e.g., crushed limestone). Dust Control In one study, ground tear-offs were spread on a gravel base and mixed with a motor grader resulting in about 2.5 in. of surface mix, which was somewhat friable. An emulsion fog seal was used to preserve the surface. Another three states used similar applications to reduce dust and provide improved driving conditions. TABlE 58 ASTM AND AASHTO TEST METHODS USED TO EVAlUATE ROOFING SHINGlE ByPRODUCTS AND HIGHWAy APPlICATION PRODUCTS Test Method Title AASHTO TP2 Method for the quantitative extraction and recove ry of asphalt binder from hot mix asphalt (HMA) AASHTO T321 Standard test method for determining the re silient modulus of bituminous mixtures by indirect tension AASHTO T170 Standard method of test for recovery of asphalt binder from solution by Abson method ASTM D226 Standard specification for asphalt saturated organic felt used in roofing and waterproofing ASTM D312 Standard specification for asphalt used in roofing ASTM D450 Standard specification for coal tar pitch used in roofing, damp proofing, and waterproofing ASTM D2178 Standard specification for asphalt glass felt used in roofing and waterproofing ASTM D4990 Standard specification for coal tar glass felt used in roofing and waterproofing ASTM D2434 Standard test method for permeab ility of granular soils (constant head) ASTM D228 Standard test methods for sampling, testing, and analysis of asphalt roll roofing, cap sheets, and shingles used in roofing and waterproofing

45 design Adaptations The following points needed to be considered during the design processes: • Any sand added to the RAS during grinding needed to be considered in mix designs. • Moisture contents of RAS stockpiles needed to be accounted for when used to stabilize soils. • The use of RAS increased the combined binder PG grade, implying that a lower PG grade upper temperature and possibly a lower PG grade cold temperature could be required for the virgin binder: – RAS increased the viscosity and stiffness. – Changes in binder properties owing to the addition of 5% RAS were similar to changes seen when using 30% to 40% RAP only (Schultz 2010). construction issues The following points needed be considered in the construc- tion of projects using RAS byproducts: • Moisture content of RAS could require longer dwell times in HMA plants. • HMA with RAS showed some tendency to be tender during rolling: – Rolling occasionally needed to be delayed. failures, causes, and lessons learned No significant major experiences were reported in the litera- ture or in the agency surveys. barriers The following barriers were found in the literature and the survey responses: • lack of documented application performance • lack of material specifications • lack of agency experience, particularly with tear-offs • Potential for additional testing for asbestos when using tear-offs • Additional testing of RAS stockpiles, particularly for tear-offs • Increased testing for QC programs. costs The following information was found with regard to the costs associated with using RAS in highway applications: • Tipping fees varied widely across the country. Based on material values and operating costs in the early 2000s, the most commonly reported tipping fee was about $50/ton, with the cost of grinding, sorting, testing, housing, regula- tion, and administration about $40/ton. – The cost of processing RAS accounted for 75% to 80% of the average tipping fees. • Organic-backed manufacturer RAS and tear-offs pro- vided a cost savings of about 5% per ton of HMA at 4% RAS content (Brock 2007). Fiberglass-backed RAS produced a savings of about 3% per ton of asphalt. – Difference in cost savings was the result of the higher asphalt content used for the organic (paper)-backed shingles that are prevalent in the older shingle products. • Recycling equipment maintenance costs were a signifi- cant factor in the costs of operation. gaps The following gaps were found in the literature and survey responses: • Education and training for agencies were needed for agencies and contractors (technology transfer). – A comparison of agency responses to information on specifications suggested it was unclear if agencies dif- ferentiated between paper-backed and organic-backed manufactured byproducts. Because these byproducts have different materials properties, agencies and con- tractors might consider this when developing specifi- cations and QC/QA programs. • RAS specifications for individual byproducts and hybrid application materials were needed. • Improved laboratory standards were needed for sample preparation and HMA testing with RAS, RAP, and/or RAS/RAP mixes. – Adaptations for asphalt content by ignition oven, binder extraction methods, and QC/QA testing pro- cedures were needed when more than one recycled product was used.