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This super strong concrete could repair aging bridges. Here’s what’s standing in the way

There's a dire need to repair aging infrastructure in the U.S., and an innovative building material could be a game changer. Embedded with steel fibers, ultra-high performance concrete is about five to 10 times stronger than standard concrete -- and unaffordable for most government-funded projects. Special correspondent Cat Wise reports from Iowa on how researchers are working to bring costs down.

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  • Judy Woodruff:

    Every day, millions of Americans cross one of the 47,000 bridges in the country in need of repair. Many are made of concrete, one of the most in-demand materials on Earth, second only to water.

    Special correspondent Cat Wise looks at a new type of concrete that some have called a game-changer when it comes to upkeep.

    Her report is part of our Breakthroughs series and the latest in our look at the Leading Edge of science, technology and health.

  • Cat Wise:

    This quiet stretch of farmland in Northeast Iowa doesn't get a lot of visitors, but several times a year, Buchanan County engineer Brian Keierleber drives down a gravel road here and pulls over above a small creek.

    From the top, the ridge he's come to inspect looks pretty typical, but, after a short trek down below, Keierleber pointed out what is very different about this bridge.

  • Brian Keierleber:

    That's completely out of the norm to be using a four-inch-thick deck. Most decks are seven to eight inches, even with beams underneath them, and if you're not with beams, 18, 20, 22 inch on your slabs.

  • Cat Wise:

    In other words, it's much thinner than normal.

    That's because it's made with a new type of concrete called ultra-high-performance concrete, also known as UHPC. It's embedded with steel fibers. And it's about five to 10 times stronger than standard concrete.

  • Brian Keierleber:

    It's very unique, to the point that we have had visitors come from around the world to look at it.

  • Cat Wise:

    There are now nine bridge projects with this material around Iowa, which was the first in the country to build a UHPC bridge in 2006.

    Keierleber says Iowa was an early adopter because there's a big need for infrastructure innovation. The state has the largest number of structurally deficient bridges in the country.

  • Brian Keierleber:

    The bridges are deteriorating a lot faster because, anymore, we put a lot of salt on the roads in the wintertime. And the chlorides will eat up the pavement, but it really eats up the bridges, too, and the concrete that way.

    So, we are, we're shortening the life, when we need to be lengthening it.

  • Cat Wise:

    UHPC, which was first developed several decades ago in Western Europe, is not just stronger than traditional concrete. It's also much more durable and less brittle, and the material is nearly impenetrable to water and chemicals like deicer.

    UHPC has now been used in bridge projects in 28 other states and the District of Columbia, but mostly on a small scale. One of the main reasons? Cost. Traditional concrete is roughly $100 per cubic yard. Commercially available UHPC costs about $2,000 to $3,000 a cubic yard.

    UHPC's current price tag makes it unaffordable for most government-funded infrastructure projects, but researchers around the country and here in Iowa are now working to bring those costs down.

  • Brent Phares:

    All right, so, give me an update as to where we are with the sands project.

  • Cat Wise:

    Brent Phares is an associate research professor at Iowa State University, which has been at the forefront of UHPC research.

  • Brent Phares:

    There's no doubt that ultra-high-performance concrete has properties that are far and above anything else that exists.

  • Cat Wise:

    Phares and his team, in collaboration with several other universities and the U.S. Department of Transportation, are developing nonproprietary blends they hope will be about half of the current cost of UHPC.

    Another goal is to determine how UHPC can be used strategically to extend the life of aging bridges.

  • Brent Phares:

    What we're doing here is taking these beams, damaging them to simulate some deterioration, and then using ultra-high-performance concrete to patch them.

  • Cat Wise:

    And what have you seen so far?

  • Brent Phares:

    Well, the research is sort of showing that targeted use of this relatively expensive material can be a way to be really effective at repairing our existing infrastructure.

  • Cat Wise:

    During our visit, engineering grad student Quin Rogers conducted a comparison compression test. Under an increasing amount of pressure, a cylinder of traditional concrete, seen on the left, burst after two minutes at 6,000 pounds per square inch, or PSI. The UHPC sample, on the right, took more than eight minutes to crack, at nearly 25,000 PSI.

  • Quin Rogers:

    As you can see, in the regular concrete, it just burst apart. But with the high-performance concrete, the steel fibers were holding that material in. And that's what gives it its strength.

  • Cat Wise:

    UHPC is now being studied and used in the U.S. and abroad for a variety of other applications, including building features.

    Another research team at Iowa State is studying its use in wind turbine towers. While scientists continue their work in the lab, others are looking forward to the day when bridges are safer and more reliable, like Randy Francois, a hog farmer in Buchanan County.

  • Randy Francois:

    Well, we really rely on our rural infrastructure here in Northeast Iowa on a daily basis.

  • Cat Wise:

    He says local bridge closures in recent years have impacted his farming operation's bottom line.

  • Randy Francois:

    I think, going into the future, we're going to need better technology in our bridges to counteract the demands that they're going to have from the farmers and the larger equipment and the more stress that we're going to be putting onto those bridges.

  • Cat Wise:

    Iowa is planning 14 new UHPC Bridge projects for the coming year, and Iowa State engineers hope to have their less expensive mix ready in the next year or two.

    For the "PBS NewsHour," I'm Cat Wise in Ames, Iowa.

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