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Science and the Environment

MODOT Uses Recycled Shingles On Highways

Those old asphalt shingles the roofers tore off your roof could end up under your car tires. Michele Skalicky reports.

The Missouri Department of Transportation is using recycled tear-off shingles to resurface and rebuild highways.

Over the past two years MODOT has allowed contractors to add used shingles that have been removed from rooftops to their asphalt mix. But Joe Schroer, a field materials engineer with MODOT, says they're limited to 5%. That's because they're not yet sure how the quality of the mix is affected. The concern is how much the shingles have been affected by sunlight exposure and how that can impact roads in cold weather. But Schroer says, so far, so good.

"From what we've seen so far, we think that we can produce an asphalt mixture that will give us, at least, an equivalent, if maybe not a longer life, on the roadway while reducing the amount that goes into landfills."

Around 2000 tons of recycled shingles have been used on Missouri's highways so far this year, and Schroer says that helps the environment.

"The biggest impact it has for the environment is reducing the amount of fill going into a sanitary landfill. Usually, construction and sanitary landfills use the same space, so it just reduces that amount."

And, he says, there are other benefits.

"For each ton of asphalt that we don't have to put into the mixture because the asphalt shingles are provided, that's just a ton of asphalt that doesn't have to be produced at the refinery."

Contractors benefit as well since adding shingles to the mix can save them money. It's estimated that the use of recycled shingles saves $3 to $5 per ton of asphalt, giving the contractors a competitive edge against other contractors in the bidding process.

Using recycled shingles in asphalt mixtures to repair and rebuild highways isn't a common practice. Schroer says mostly states along the East Coast with limited landfill space do it, but he says the shingles are mainly used in commercial mixtures. He says very few states allow tear-off shingles in their asphalt mixture.

MODOT is working with other agencies and organizations nationally to refine the specifications for the use of asphalt shingles as a hot-mix asphalt material.