Ecocentric

How Smart Paint Saves Bridges

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Joe Raedle / Getty Images

Workers examine the closed memorial bridge as water crosses it from the flooding Mississippi River June 18, 2008 in Quincy, Illinois.

There’s a lot to love about bridges: they’re practical, beautiful and connect communities that might otherwise be a lot less accessible (think Manhattan with only ferries). But bridges also have a nasty habit of falling apart—fast, by engineering standards. Stretch a span of gravity-defying metal across a wet, windy river and send thousands of thundering cars, trucks and subway trains across it every day and you’re going to have a little wear and tear.

Up to 73,000 American bridges are considered “structurally deficient,” and the consequences of that can be as terrible as they seem. The most recent large-scale bridge disaster in the U.S. occurred in 2007, when the Mississippi River Bridge in Minneapolis collapsed during rush hour, killing 13 people and injuring 145. Scarily, the bridge had earned its structurally deficient label 17 years prior, but that simply meant it would, in theory, be replaced by 2020, depending on the availability of funds.

Infrastructure money is still hard to come by, even as some states have begun crawling out from of the Great Recession, and bridge repair is not always a top priority. But now, there might at least be a cheap, easy way to detect which bridges are in greatest need of repair, and to spot small weak spots before they become large, deadly ones, thanks to an innovation a team of Scottish engineers are calling “smart paint.”

Developed by Mohamed Saafi, a civil engineering professor at the University of Strathclyde in Glasgow, and PhD candidate David McGahon, smart paint is a cement-like mixture of fly ash — a powdery residue of coal combustion —and carbon nanotubes. When applied to a structure, the fly ash gives the paint a weather-resistant durability, which is always nice, but the nanotubes do something far cooler. Nanotubes conduct electricity , and a flaw in a structure can cause them to align differently, which in turn changes the way the current flows in that spot.  Sensors attached to the bridge could then signal the problem to human engineers.

Bridges are by no means the only things that could get the smart paint treatment. Other high-stress structures—like the base of wind turbines—could benefit as well. Though smart paint couldn’t replace traditional visual inspections anywhere its used, its ability to detect minor structural faults as they occur could at least assist engineers in prioritizing maintenance in the face of limited funds, manpower and time.

“If you have 100 bridges, which one are you going to inspect?” Saafi said. “This system will help identify which one needs help.”

Largely because fly is ash is an accessible, recycled product, smart paint itself would be relatively inexpensive—and can provide one small green use for the massive amount of ash that’s created each year in coal-fired power plants. Saafi’s team has successfully operated their system on a small scale, and hopes to test it on a wind turbine, a bridge and an underground tunnel in Glasgow by summer 2013. Navigating the Brooklyn Bridge at rush hour may never get a whole lot faster or easier, but it could become just a little bit safer.

 

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