HAMPDEN — Instead of metal girders, the Maine Department of Transportation is using a new composite material for the Grist Mill Bridge replacement project.
“So this is the first time the CT girders are being used in any bridge in the country,” said Colby Kohn, AIT Bridges communications manager.
Advanced Infrastructure Technologies or AIT Bridges is a privately held company licensed by the University of Maine to produce the composite arch bridge system, commonly known as the “Bridge in a Backpack.” A project of UMaine’s Advanced Structures and Composites Center, AIT just started making the composite tub or CT girders.
“They’re twice as strong as steel, which is very impressive,” Kohn said. “They need no concrete in the tub, no concrete reinforcements. Full composite bridge piece.”
He added, “This is layers of carbon fiber and fiberglass in the top and bottom flanges and then there is a piece of foam core in the sidewalls to add, to keep the lightweight structural integrity.”
Working with the university allows the technology to be used by others, Kohn said, which is a benefit for other small businesses. AIT opened in Brewer about 18 months ago.
Maine Department of Transportation is working on an $8.9 million approximately two-mile rebuild on Route 1A in Hampden.
“We’re optimistic about the opportunity to use different composite materials,” said Paul Merrill, an MDOT spokesman.
The girders are scheduled to be put into place next Thursday.
“Hopefully, in one day we can get this done,” Kohn said, adding Friday will be used, if needed.
He added that special sensors have been added to the girders to allow engineers to monitor their strength and integrity for years to come.
After the girders are in, drivers will again be able to cross the bridge that spans the Souadabscook Stream.
“The plan right now is to pour the concrete deck of the bridge by November 20th and our plan, at this point, is to open the bridge to traffic in the first part of December,” Merrill said.
“We all know how long bridges can take in this state,” Kohn said. “Anything to speed them up and make the process quicker, we’re all about it.”