In 1994, Georgia mixed damaged factory roofing shingles into Chatham Parkway asphalt; later checks found the recycled road performing as well as its control

Every so often, a storm, a leak, or a renovation puts a dumpster in a driveway and sends a roof’s worth of shingles to the curb. Most Americans never wonder where that pile ends up. In the mid-1990s, the engineers in Georgia asked a stranger question: what if it ended up under our tires? According to Watson, Johnson, and Sharma’s 1998 paper titled “Georgia’s Experience with Recycled Roofing Shingles in Asphaltic Concrete,” published in the Transportation Research Record: Journal of the Transportation Research Board, the Georgia Department of Transportation built two test sections of hot-mix asphalt using shingle waste. The waste for these two sections specifically came from a roofing manufacturer and was mostly discolored or damaged factory scrap, not material pulled off old roofs. One section was on Chatham Parkway in Chatham County; the other was on State Route 21 in Effingham County. Both were reported to be performing well compared with control sections of ordinary pavement.

The trash problem and why a roof and a road make sense together

Asphalt magazine notes that the EPA estimated around 11 million tons of asphalt shingles are thrown away in the U.S. every year. Roughly 1 million tons come from manufacturers and about 10 million from residential tear-offs, per the 2011 Asphalt magazine estimate; the current figure may differ. The scale is the point: roofs wear out everywhere, from Sun Belt suburbs to storm-battered coastlines.

The pitch is straightforward: recycling shingle waste eases landfill pressure. It also cuts the amount of virgin asphalt cement and fine aggregate a mix needs, which lowers cost. Shingles are typically added at about 3 to 5 percent by mass, per the University of Wisconsin-Madison’s Recycled Materials Resource Center, which also cites a Georgia-era estimate that a 5 percent share could trim hot-mix costs by roughly $1.70 per ton. That’s a modest discount on any single load, but paving contracts run to thousands of tons, so the savings compound quickly.

From test strip to the rulebook

The experiment did not stay as a one-off. Per the 1998 paper, Georgia DOT began allowing the use of manufacturing shingle waste in asphalt mixes as if it were reclaimed asphalt pavement. A companion specification covering post-consumer (tear-off) shingles was still being drafted at the time of the 1998 paper. That gap closed within a few years: by 2011, Asphalt magazine reported Georgia’s specifications allowed up to 5 percent of either factory scrap or tear-off shingles in a mix, and that ceiling has held. A City of Decatur, Georgia specification still in force today caps total reclaimed asphalt shingle (RAS) content at no more than 5 percent of the recycled mixture, consistent with state practice. A current Georgia specification limits the amount of RAS material used in the recycled mixture to no greater than 5 percent.

The fine print nobody puts on a billboard

“Performing well” is not the same as “flawless,” and the research said so. According to the Recycled Materials Resource Center, field trials in Georgia and New Jersey performed similarly to conventional mixes, but the Georgia mix hardened faster. That faster hardening comes from a stiffer, more aged binder in shingle-heavy mixes, which the Center cautions can mean lower fatigue and low-temperature cracking resistance in some cases. That risk isn’t universal, though: Minnesota’s trials, which paired shingle scrap with adjustments to the virgin binder, didn’t show added cracking. The split result tracks with a 2014 FHWA memo noting that an increasing number of state DOTs had reported premature cracking in relatively new asphalt pavements, which the agency linked in part to recycled asphalt shingle content, and recommending states adopt design limits on RAS binder levels to manage the risk. In other words, the cracking risk is real but manageable, and different states have handled it with different binder adjustments rather than it being a flat contradiction.

Pennsylvania offers a useful cross-check; a 1999 PennDOT report by Andrew Reed found that a 5 percent shingle test section near Allentown showed no measurable rutting after five years, while the control section had ruts of about a quarter to a half inch. Over that same five-year span, the report documented more centerline cracking in the shingle sections in the 1990s. Core tests also showed much higher binder viscosity, which the author said suggested the mix may age more quickly.

What about asbestos?

Older roofs raise a fair concern: re-roofing waste can contain asbestos in very small quantities. OSHA regulates workplace exposure and the EPA regulates handling and disposal. The Recycled Materials Resource Center cites a 2007 review that found asbestos in just over 1 percent of about 27,000 samples. It’s worth flagging that this is a post-consumer tear-off hazard, not a factor in the original Chatham Parkway and State Route 21 trials, which used clean factory scrap rather than material stripped off old roofs. It matters today because Georgia’s current specifications, unlike the 1994 pilot, now permit tear-off shingles too, so the asbestos screening question applies to the material stream the state actually uses now, even though it wasn’t a factor in the trial that started it.

Is this the future of roads? Probably not on its own. The Georgia trial should best be read as proof that a very ordinary waste stream can have a second life, with the caveat that the results depend on the shingle source, the mix design, and how much is added. It is a small, practical idea, not a miracle. But for a country that tears off millions of tons of roofing every year, a modest, well-specified use for the waste is still a meaningful one.