Illinois Tollway Authority Jump Starts Asphalt Shingle Recycling in the State

The Illinois Tollway is a user-supported system of public roadways. The Tollway receives no state or federal funding for maintenance and operation of its system, relying primarily on tolls paid by travelers on the roadways.

With that fact, it is essential the Tollway maximize the performance of its roadways, while also looking at reducing the costs of achieving long-term performance.

One effort along those lines was the Tollway’s decision to allow for use of recycled asphalt shingles (RAS) in its asphalt mixtures. As numerous states have evaluated and begun using RAS in asphalt mixtures, the Tollway recognized an opportunity to incorporate that process into its construction contracts. The work to achieve this accomplishment was tackled on two fronts: one environmental, and one from the engineering aspects of RAS in asphalt mixtures.

Steve Gillen, Illinois Tollway materials manager, approached the U.S. Environmental Protection Agency (EPA) Region 5 to develop a partnership to support the use of recycled asphalt shingles in roadway projects, as well as to introduce a new opportunity for the recycled materials industry in Illinois. Region 5 agreed that combining both the environmental and transportation industry efforts would increase the likelihood of successfully implementing shingle recycling in Illinois. The partnership resulted in the EPA and the Tollway supporting new materials research, and also conducting public forums to share the news that shingle recycling was coming to Illinois.

The Tollway and the EPA selected Iowa State University and Associate Professor Chris Williams to lead the materials research effort for the project. Already working with the U.S. Federal Highway Administration (FHWA) on a pooled fund study for shingle recycling, Iowa State’s work with the Illinois Tollway would provide additional research data to combine with FHWA efforts.

Recyclable shingle materials come from two sources: waste from the manufacturing process and “tear-offs” from roof re-shingling projects. Environmentally, the primary difference between the two is asbestos. Manufacturers of new shingles cannot use asbestos, so the manufacturer’s shingle waste is asbestos-free. Older shingles may contain asbestos, so tear-off shingles typically are tested to ensure they are asbestos-free. Since the Illinois EPA had never been asked to develop a protocol to manage tear-off shingle recycling, one had to be developed.

The Illinois Tollway and Iowa State University have worked hand in hand with the Illinois EPA to develop “Guidelines of Best Management Practices for the Operation of Post-Consumer (Tear-Off) Asphalt Shingle Recycling Facilities.” Debra S. Haugen, LLC, as a consultant to Iowa State, produced the guidelines draft, and the IEPA’s Bureaus of Land, Air and Water each reviewed the “guidelines” document. Each IEPA bureau agreed the guidelines addressed their concerns regarding the recycling of tear-off shingles. The guidelines provide effective inspection and testing protocol to ensure the recycled tear-off shingles are asbestos-free, as well as proper practices for handling, testing and producing RAS that can be effectively used in asphalt mixtures. The Illinois EPA’s acceptance of the “guidelines” document allows for tear-off shingles to be included under a beneficial use determination (BUD) needed to recycle tear-off shingles. The “guidelines” document can be obtained from the Illinois Tollway’s Web site, www.illinoistollway.com.

On the engineering side of RAS and asphalt mixes, the Tollway had increased the allowable amounts of reclaimed asphalt pavement (RAP) in asphalt mixtures as part of an earlier research project. In 2007, the Tollway research involving fractionated RAP (FRAP) demonstrated the consistency and quality of the asphalt mix was not compromised when the FRAP levels in the asphalt mixes were increased. The process of Fractionating RAP separates the RAP into different sizes, just as with the processing of virgin aggregates. Among other benefits, fractionating the RAP into different sizes allowed the RAP to be metered into the mix more consistently, increasing the quality control capabilities. On the heels of that research, the Tollway wanted to include the RAS option of pavement recycling into its specifications, but was reluctant to step back from the gains achieved with the increases in allowable RAP.

One item that has changed with the use of RAS in asphalt mixes is how agencies regulate the amount of reclaimed and recycled materials being used in hot mix asphalt. Typically, RAP allowances are given in “percent RAP,” and that works for RAP because the asphalt content in the RAP is pretty much the same as the asphalt mix itself. So, the specifications are written allowing 15% RAP, 25% RAP, whatever the level may be.

With RAS, the amount of asphalt binder in the shingles is four to five times the asphalt content of the mix, so percent shingles can be equated with percent RAP. To put shingles on a level playing field with RAP, the concept of “percent binder replacement” has emerged as the method to regulate the amount of recycled asphalt materials allowed in the mix. Agencies aren’t particularly concerned with limiting the aggregate materials in the RAP or RAS, but the amount of stiffer asphalt binder can be a concern. So, when agencies are allowing either shingles or RAP in their mixes, the allowable limits are based on percent binder replacement—basically, how much virgin binder is being replaced with recycled binder—whether the recycled binder comes from recycled shingles or RAP.

To analyze using recycled shingles in asphalt mixes, the Tollway used the higher RAP mixes developed in the earlier research, and substituted 5% RAS as an ingredient in the mix. Four different hot-mix asphalt (HMA) base mixes, an HMA surface mix, and a stone matrix asphalt (SMA) surface mix have been placed in two test sections more than 4 miles in length, and are being evaluated to strength and long-term durability. Typical specifications for mixes using well-processed RAP limit the “percent binder replacement” to 20%-40% of the total mix asphalt. The Tollway’s evaluation of RAS in their mixes includes mixtures having upwards of 65% binder replacement.

Subsequent to the development of the “guidelines” document and the placement of the RAS test sections, the Illinois Tollway and the EPA recently hosted the “Asphalt Shingle Recycling Workshop” to summarize the work conducted and allow participants to discuss and interact on the possibilities of RAS usage. Nearly 200 people from the recycling, transportation, asphalt construction and engineering industries came together in suburban Chicago for a half-day session on how to effectively produce and use RAS.

The Tollway currently has three 2010 contracts that provide the asphalt construction contractors with the option to use RAS in their asphalt mixes. The benefits of using RAS in asphalt mixes are many, and the Tollway is hoping the industry jumps on board.

About the Author
Ross A. Bentsen, P.E., Bloom Companies, LLC, has provided materials engineering services
to the Illinois Tollway since the onset of the Tollway’s Congestion-Relief Program in
2005. He can be reached at the Illinois Tollway’s main office in Downers Grove, Ill., at 630-241-6800, ext. 3968. 

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