Cincinnati -- The University of Cincinnati College of Engineering is helping the Ohio Department of Transportation plan a showcase bridge in east central Ohio to demonstrate the improved strength and durability of a unique high-performance concrete mix developed at UC. The bridge is one of eight in the country being built under a special Federal Highway Administration program to bring new technology into common use.
"It's an opportunity to take recent government research and put it into a practical application that we hope will improve bridges in the United States," said Richard Miller, associate professor of civil engineering at UC.
The high-performance concrete (HPC) allows the production of longer beams for the bridge. The original design used normal concrete and required three separate spans set on top of piers. With HPC, a single span can be constructed across the entire creek.
"With the material and the design we're using for this particular bridge, we're able to eliminate the piers which would have been sitting in the water, collecting debris," said Michael Baseheart, associate professor of civil engineering. "Piers have increased maintenance costs asociated with clearing away the debris."
Tests have demonstrated that the UC-designed concrete mix is significantly stronger than conventional concrete. "The strength of the concrete came out to be between 10-12 thousand pounds to square inch, which makes it approximately three times as strong as sidewalk concrete and twice as strong as normal bridge concrete," according to Miller.
The UC engineers also conducted a wide range of durability tests on the concrete used in a sample beam. "We've done some fatigue tests, subjecting the beam for one million cycles (simulated truck loads)," said associate professor Bahram Shahrooz.
"We pushed it to where the code said it would be fail, but it did not fail. It bounced back. We couldn't actually collapse it," noted Miller.
Based on their test results, Miller believes bridges made with the high performance concrete beams could last for up to 80 years without requiring major maintenance. That's because the denser material keeps road salt away from the reinforcing steel inside. The material is also more resistant to freeze-thaw cycles, a common road-killer in temperate climate zones.
"In Cincinnati for example, you might get 20 cycles of freeze- thaw each year. The concrete we've developed has been through 300 simulated freeze-thaw cycles without any problems."
In addition to the cost benefits of the single span design and reduced maintenance costs, there is also a benefit to the local community where bridges are built. "A lot of steel gets imported," noted Miller, "but all concrete is made locally. You can't import concrete, so it's definitely a local job-producing kind of thing."
The formal contract for the new bridge near Cambridge, Ohio will be let this summer, and a final round of tests will be run on another sample beam at Prestress Services in Melbourne, Kentucky this June. Information on creating the high-performance mixes and producing extra-long concrete beams will be shared with contractors and transportation officials nationwide.
The project is funded by the Ohio Department of Transportation and the Federal Highway Administration's Strategic Highway Research Program.