As much as 42 inches of snow covered the ground last week after a historic blizzard slammed the East Coast. Days later, cities are still working to clear roadways and sidewalks.
Chris Tuan, a civil engineer at the University of Nebraska, Lincoln, thinks there’s a better way to manage this huge task. With funding from the Federal Aviation Administration, he’s come up with a formula for making conductive concrete, which can carry enough electrical current to melt snow in even the worst storms.
The mixture contains basic concrete ingredients—including cement, sand, and water—but Tuan has replaced 20 percent of the components with steel shavings and a fine powder called “coke breeze,” both of which are industrial waste products. When the finished slabs are connected to a power source via steel rods inserted inside the concrete, they can generate heat that will spread to the concrete’s surface.
Tuan currently has a 200-square-foot test slab connected to a 120-volt AC power source outside his office that shows how the concrete works:
If testing is successful, the FAA will use the concrete on airport tarmacs to minimize delays during winter storms. But his research could also be used in cities.
In 2003, Tuan and his colleague, electrical engineer Lim Nguyen, tested a version of the conductive concrete by installing 52 slabs onto the 150-foot Roca spur bridge, just 15 miles south of Lincoln. “We know a lot of accidents can happen on bridge decks because they’re always icy since they’re exposed to the elements both on the top and bottom,” says Tuan. The results of the five-year-long experiment, published in the Journal of Cold Regions Engineering, were promising; the bridge successfully de-iced itself, and powering the concrete during a three-day storm cost about $250—far less that the cost of deploying snow plows and salt.
Since then, Tuan has been working to make the concrete more affordable and therefore, scalable. By replacing the recipe’s highly conductive synthetic carbon power with industrial waste, he cut down the cost from over $600 per cubic yard to just $300.
Still, it’s a hefty price compared to regular concrete, which costs roughly $120 per cubic yard. In fact, Tuan advises against constructing entire roadways out of conductive concrete. Rather, he says, they should be used on specific areas with higher rates of accidents during storms, like intersections, exit ramps, and uphill roads.
The key is to turn on the power a day before a huge snowstorm hits to “preheat” the concrete. “When the snow hits, it melts instantly so you don't have any accumulations,” he tells CityLab, adding that it would remain safe to the touch. Depending on the size of the area covered, it can take as little as 48 volts to power the concrete.
Over time, the benefits add up. Tuan says current experiments show that the operating cost is only two cents per square foot, and the maintenance cost is virtually zero since there are no harsh de-icing chemicals involved. Tuan expects to get approval from the FAA after testing ends later this year, and he says he’s confident: “After I did the Roca Spur bridge project, which ended in 2008, I was very confident the technology is mature enough.”
This post appears courtesy of CityLab.
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