Over 40,000 bridges in the U.S. are considered structurally unsafe, and more than 200,000 need repairs.
But help may be on the way, thanks to a new invention from engineers at Florida International University (FIU).
They’ve created a spray-on system using a special kind of concrete that could make bridges stronger and more durable—without needing to rebuild them.
The key to this new system is something called Ultra-High Performance Concrete (UHPC). It’s much stronger and more water-resistant than regular concrete.
Even a thin layer of UHPC can make a big difference, adding strength and protecting structures from water damage.
The problem until now? It’s been very expensive.
But FIU researchers have changed that. They developed a new, affordable version of UHPC and a spray system that makes it easy to apply.
“We’ve created a version of UHPC that costs much less and is easy to use,” said Professor Atorod Azizinamini, a civil engineering expert at FIU. “This could be a game-changer for fixing old bridges quickly and cheaply.”
FIU’s version of UHPC costs about $500 per cubic yard—far less than most commercial types. And because only a thin layer is needed, the total cost for repairs stays low.
The system works like a spray paint can, applying concrete in light, even layers using a special nozzle.
These layers can be stacked one on top of another, and they’re light enough that they don’t add much weight to the structure.
The first real-world test happened on a bridge in Virginia, where the concrete was sprayed onto a wall damaged by salt used for de-icing roads.
“We were impressed with how easily the UHPC was applied and how it helped protect the bridge,” said Sam Fallaha from the Virginia Department of Transportation.
FIU now plans to train engineers and builders across the country to use this system. Ph.D. student Morgan Dickinson compared the nozzle to a glue gun: “Just like with glue, if you don’t clean the nozzle properly, it can clog and harden. That’s why training is so important.”
Industry leaders are also excited. Kia Hajifathalian from Baker Construction, one of the largest concrete contractors in the U.S., said, “This isn’t just lab research. It’s something we can use across the country to fix buildings and bridges.”
With its low cost, easy use, and strong results, FIU’s spray-on concrete system could be the solution to America’s aging infrastructure.
