Researchers at the University of Connecticut are developing new techniques to repair bridges damaged by weather and corrosion from road chemicals.
Dr. Arash Zaghi, assistant professor of environmental and civil engineering at UConn, said that most bridges in the country suffered severe damage from salt used on roads, which corrodes the steel that makes up the structure. Traditionally, repair of this damage involves cutting away the damaged portions of the bridge and either replacing the damaged piece or sandwiching it between two pieces of new steel.
As bridges age, they become less structurally stable due to years of corrosion and structural damage. Many bridges in the United States are reaching the end of their service life and are considered functionally obsolete, requiring immediate attention, Zaghi said.
Repairing these damaged bridges is not an easy process. It would cost billions of dollars and innumerable work hours to complete, disrupting traffic along major routes. Zaghi also said it provides a significant environmental risk, as many old bridges were constructed with lead paint.
“We are creating an approach to a traditional problem that could be a game changer,” Zaghi said. “Our answer is not to inject more money to solve the problem, but to look at the problem with a different approach, and finding more creative ways of doing things.”
Zaghi and a team of researchers at UConn and the Connecticut Department of Transportation began a study two years ago with the Department of Homeland Security and the Lafarge Group on an innovative repair technique using an advanced form of concrete called ultra-high-performance concrete, which would eliminate many of the difficulties of repair.
Dr. Kay Wille, assistant professor of civil and environmental engineering at UConn, said that UHPC is about five times stronger than regular concrete and is highly resistant to erosion.
The UHPC is pumped into molds around the damaged sections of the bridge, forming a protective barrier around the corroded steel. This technique is much less expensive than traditional repair methods and results in less interruption to traffic. Repairs can be completed in a few days as opposed to a few months, Wille said.
Zaghi likens this process to treating damaged teeth. The problem used to be fixed by completely removing the damage, but the new method would be to fill in the damage and apply a protective coating.
In laboratory tests, steel repaired with UHPC is more resistant to buckling and is 24 percent stronger than undamaged steel.
“The potential is there to do the repair in a much simpler and more efficient way and much cheaper,” Wille said.
The expense of the repair is not only less in upfront cost, but UHPC requires less maintenance and lasts longer than old repair methods, resulting in less recurring costs.
“It’s very exciting that we have a repair like this that can save billions of dollars for the state. A huge chunk of the government budget goes to repairing bridges,” Zaghi said. He said use of this material would allow construction to look farther into the future, making structures that will last for hundreds of years as opposed to decades.
Despite its potential in structural and transportation engineering, there is some hesitation to using UHPC as a repair material, Wille said. While it represents a much lower cost than steel replacement, UHPC is still much more expensive than traditional concrete, and requires more quality control in the process. Wille believes that showcasing the applications of the product and the benefits of its use will create more belief in the material.
“The issue is there,” he said. “It’s a perfect fit with gigantic benefits.”