In May 2025, an interdisciplinary research team from the University of Massachusetts Amherst and MIT tested a new 3D printing process for repairing bridge structures in the field. In the so-called “cold spray” technique, metallic powder particles are accelerated to high speed by compressed gas and applied to damaged steel surfaces. The application was carried out on the “Red Bridge” in Great Barrington, Massachusetts, a structure built in 1949 that is to be dismantled in the coming years.
The process belongs to the class of additive manufacturing methods, but differs from conventional thermal processes in that it does not use melting zones. Instead, the particles adhere to the surface through plastic deformation and form a metallurgically stable layer through repeated application. The aim is the targeted restoration of material thickness and mechanical properties in corroded areas.
“Now that we’ve completed this proof-of-concept repair, we see a clear path to a solution that is much faster, less costly, easier, and less invasive,” said Simos Gerasimidis, associate professor of civil and environmental engineering at the University of Massachusetts Amherst, and one of the principal investigators on the project. “To our knowledge, this is a first. Of course, there is some R&D that needs to be developed, but this is a huge milestone to that,” he added.
“Any time you drive, you go under or over a corroded bridge,” Gerasimidis said. “They are everywhere. It’s impossible to avoid, and their condition often shows significant deterioration. We know the numbers.”
“Every time you do repairs on a bridge you have to block traffic, you have to make traffic controls for substantial amounts of time,” explained Gerasimidis. “This will allow us to [apply the technique] on this actual bridge while cars are going [across]. By combining scanning with precise material deposition, we can be very targeted and say, ‘we’re going to print here and here and here and we’re going to give this bridge another 10 years of life,’ which is huge,” he explains.
In combination with precise 3D LiDAR scanning, the process enables digital recording of the damage pattern and automated planning of the material application. This reduces the amount of material used and allows targeted reinforcements to be carried out without completely closing the bridge – a relevant advantage in view of increasing maintenance requirements. According to the American Society of Civil Engineers’ Infrastructure Report 2025, around 49 percent of US bridges are only in “satisfactory” condition, while 6.8 percent are considered “deficient”.
Once the field test is complete, the deployed bridge segment will be transferred to UMass laboratories to evaluate the adhesion, corrosion resistance and residual load-bearing capacity of the applied coating.
“We know this problem quite well,” he says. “We have seen thousands of inspection reports, we have gone to bridges. We have tested many beams in our lab, so we know how these things behave and exactly where we need to repair.”
“This is a tremendous collaboration where cutting-edge technology is brought to address a critical need for infrastructure in the commonwealth and across the United States,” said John Hart, Class of 1922 Professor in the Department of Mechanical Engineering at MIT. “I think we’re just at the beginning of a digital transformation of bridge inspection, repair and maintenance, among many other important use cases.”
“It’s a very Massachusetts success story,” Gerasimidis said. “It involves MassDOT being open-minded to new ideas. It involves UMass and MIT putting [together] the brains to do it. It involves MassTech to bring manufacturing back to Massachusetts. So, I think it’s a win-win for everyone involved here.”
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