Monday, December 11, 2017

Winter is coming. What if roads and runways could de-ice themselves?

When Chris Tuan was a Department of Defense contractor in the early 1990s, the Air Force asked him to think of something that could de-ice its airfields around the world.

Heavy cargo aircraft were landing on icy runways and skidding off, he says, “so they wanted to find out some innovative way to de-ice the runway.”

The challenge? He couldn’t use any salt or de-icing chemicals because of the damage they can do to concrete.

Tuan had studied how to use steel fibers to reinforce concrete. He decided to embed them in the runways and run a low-voltage electric current through the steel to heat the concrete, so the snow and ice can just melt off the surface.

“Think of it as a heating blanket,” he says.

It worked. And now researchers at various universities are working on surfaces that can de-ice themselves, so salt or de-icing chemicals don’t have to be used on roads and other paved surfaces in the winter. The Federal Aviation Administration supports this work because keeping runways clear is a big problem for airports in cold places.

Tuan says the Air Force didn’t scale it up at the time because of budget cuts.

But Tuan, now a professor of civil engineering at the University of Nebraska-Lincoln, didn’t forget his idea.

Starting in 2002 and working with the Nebraska Department of Transportation, he ran a five-year test on a 150-foot-long bridge near Lincoln, Neb. He says a 208-volt current running through electrodes kept the bridge free of ice during 15 major snowstorms at the “amazingly low” operating cost of about $250 per storm.

The conductive concrete involves adding steel fiber and carbon to the concrete mix, he says. While regular concrete costs $120 per cubic yard, the conductive concrete costs $350-$400 per cubic yard. But in the long term, Tuan says the conductive concrete means fewer de-icing chemicals in the ecosystem, and concrete that lasts longer and costs less to maintain.

Tuan says he’s working on several projects overseas, and he just finished running FAA-funded tests on a 200-square-foot site in Nebraska this year. He points to this time-lapse video of the slab in action and says the results are excellent.

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