Missouri Takes Lead in Shingles Recycling

As long as local recyclers of asphalt shingles can meet a new material specification put forth by the Missouri Department of Transportation (MoDOT), asphalt shingles from roofs could be used as part of the ingredients for new and renovated roads.

This was the result of a two-day informational program funded by the Missouri Department of Natural Resources and co-sponsored by the St. Louis-Jefferson County Solid Waste Management District.

Billed as “St. Louis’ First-Ever Roofs to Roads Seminar,” the program was intended to showcase the benefits of recycling tear-off roofing shingles into hot mix asphalt (HMA) and aggregate base. A local C&D recycling company, Peerless Resource Recovery, Valley Park, Mo., was the lead coordinator of a professional seminar on shingle recycling held in St. Louis March 29-30.

Joe Schroer is the MoDOT materials engineer responsible for the development of their newly drafted specification for use of recycled asphalt shingles (RAS) into HMA. At the request of HMA producer and paving contractor Pace Construction Co., MoDOT released its revised spec that has been under development for years. One of the key provisions limits deleterious materials such as plastic, metal or wood to a maximum of 3 percent by weight (cumulative total of all debris) in the RAS product before introduction into the HMA plant.

At least two shingle recycling operations are in Missouri. The only one so far in the St. Louis metropolitan area is Construction Materials Recycling Association (CMRA) member Peerless Resource Recovery. Peerless has been conducting a variety of research and development efforts on tear-off shingles recycling for several years. Dale Behnen, co-owner of Peerless Resource Recovery and Peerless Landfill, was the principal organizer of the seminar. “The announcement by MoDOT about their new shingles spec puts Missouri in a lead role to further the development of shingles recycling throughout the country. Now the burden is on private shingles recyclers like us to meet this specification as cost effectively as possible. We believe we can meet the 3 percent maximum deleterious materials requirement and the related limit of 1.5 percent wood.  We know we will have to make improvements to our recycling system, but this new spec gives us a clear and fair standard for such design changes.”

Roger Brown, vice president of Pace Construction, says, “We are pleased that MoDOT is proposing to adopt this compromise on deleterious limits. We also believe, as the producer incorporating the RAS from Peerless into our HMA, that we can also meet the mix design requirements in the draft MoDOT spec.”

The MoDOT draft spec includes provisions for shingle-derived HMA to meet the equivalent of a virgin asphalt performance grade (PG) of 64-22. If a producer like Pace uses the allowed 5 percent maximum of RAS, then MoDOT would require an adjustment to the virgin asphalt binder in the mix to a softer PG 58-22 grade to compensate for the low temperature stiffness properties of shingles. If a HMA producer wants to use less RAS or make other adjustments to the mix design, then a proposed job mix formula can be submitted to MoDOT for consideration.

MoDOT considered other states’ recycled shingle specs and the draft spec proposed for the American Association of State and Territorial Highway Officials (AASHTO). Schroer said in his seminar presentation MoDOT accepted the industry argument that a deleterious materials limit of 3 percent (cumulative total of all debris) in the shingle product was reasonable given the relatively low percentage (5 percent maximum) of RAS allowed in the HMA. Also, the sample analysis by MoDOT indicated that the wood debris in the RAS appeared to be either burned off or permeated with asphalt after passing through the hot mix plant. Therefore, MoDOT is proposing a 1.5 percent maximum amount of wood debris in the RAS.

In addition, St. Louis County Department of Highway and Traffic is also in the process of adopting its own recycled shingles in HMA specification. Richard Holesinger, county materials engineer, informally presented his draft spec. Holesinger said the county accepted the same deleterious materials limits as proposed by MoDOT, but has not yet settled on a mix design approach for adjustment of the PG grade of virgin asphalt in the mix.

About 25 participants attended the Roofs to Roads seminar, including other HMA producers, other MoDOT staff, other county staff and one roofing company. A variety of national speakers presented the details of other shingles recycling programs from other parts of the country. Dan Krivit, Dan Krivit and Associates, St. Paul, Minn., presented a summary of national and Minnesota research on the subject. Carl Wight, Commercial Paving and Recycling, Scarborough, Maine, discussed how his company produces a variety of recycled gravel products that use 30 to 50 percent tear-off RAS. Steve Johnson, Roof to Road LLC, Williamsport, Ohio, presented information on how he has been able to make ends meet to recycle tear-offs into a salable RAS product for a local HMA producer in Ohio, despite the competition of relatively low landfill tipping fees.