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


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, Buchanan County Engineer:
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, Iowa State University: 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, Graduate Student: 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, Hog Farmer: 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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