Researchers at Florida International University have developed a sprayable concrete system that could transform the way bridges are repaired across the U.S.

As reported by FIU News, engineers at the university have created a method for applying Ultra-High Performance Concrete (UHPC) directly onto infrastructure. This advanced material can be used to patch walls, repair pipes, and restore drainage culverts – often making them stronger than their original condition.

The U.S. Department of Transportation notes that UHPC is increasingly being used in transportation infrastructure projects. Traditionally, UHPC is poured into place, either as a self-consolidating mix that flows into molds under its own weight or as a thixotropic mix that requires vibration and leveling during placement.

Spray application could enhance current UHPC uses – such as repairing girder ends or reinforcing walls and columns – by allowing the material to be applied directly. It also opens the door for new applications, like bridge deck soffit repairs and culvert retrofits.

In many cases, spraying UHPC is more cost-effective than traditional pouring methods because it eliminates the need for formwork. It also offers greater versatility, enabling application from any angle and overcoming challenges posed by gravity-based pouring in obstructed areas like under bridge decks.

“UHPC has historically been very expensive to use, mainly because most of those available [mixes] on the market have been commercial versions,” said Atorod Azizinamini, a professor of civil engineering and director of a U.S. Department of Transportation-funded research center at FIU. “Even a very thin layer of UHPC can drastically improve the strength of a structure and protect it from water.”

“We have developed an affordable type of UHPC, and a system that can spray it,” Azizinamini continued. “This could become a major tool in repairing or upgrading structurally deficient bridges quickly and efficiently.”

FIU’s UHPC mix comes in at around $500 per cubic yard, which is considerably cheaper than many comparable commercial versions of the product. The school’s application system deposits thin layers of concrete onto surfaces through a nozzle, like how spray paint is applied. These layers can be added, one upon another, in coats. Their light weight doesn’t significantly alter the mass of a structure.

The FIU team used their system and UHPC mix on a bridge in Virginia last year.

“The reason that we invited the FIU team here to Virginia is that we had a bridge abutment wall that had corrosion issues due to the deicing salt that is used here,” said Sam Fallaha, an engineer with the Virginia Department of Transportation. “We liked it because it is easy to apply a thin layer to vertical surface creating a durable solution for problems like these that occur in cold climates.”

The Virginia job was the first-ever application of its kind in the U.S. The Risk and Resilience Tech Hub is investing roughly $1 million into the FIU researchers’ system to commercialize the technology and help the university train more engineers and builders to use it.

“Anyone who has used a glue gun for an arts and crafts project knows how difficult it can be to keep the nozzle from getting clogged,” said Morgan Dickinson, a Ph.D. student in Azizinamini’s lab. “The same goes with our UHPC system. If you don’t know how to clean it, the concrete hardens, and you might have to throw parts away. Fortunately, we are seeing widespread interest in people who want to learn about our system and use it properly.”

Kia Hajifathalian, Vice President and Market General Manager at Baker Construction, told FIU News that he sees the FIU system as a practical way of bringing the benefits of UHPC to more buildings and bridges around the nation.

“This is not just research in a lab that will only have a couple of specific uses,” Hajifathalian said. “I think that FIU has figured out how to utilize UHPC in a way that can be used to repair buildings and bridges at scale.”

“The biggest nightmare of a concrete contractor is pouring concrete, testing it later and finding out that it is not as strong as you thought it would be because something unexpected happened,” he added. “Having that concrete in a pre-bagged system like FIU is doing, where you have quality control, is so important.”

The State of America’s Bridges

There are more than 623,000 bridges across the United States, according to the American Society of Civil Engineers (ASCE) 2025 Report Card for America’s Infrastructure.

The ASCE gave America’s bridges a C in that report card, citing the fact that 49.1% of the country’s bridges are in “fair” condition, 44.1% are in “good” condition, and 6.8% are in “poor” condition.

“Unfortunately, the nation continues to see the number of fair bridges surpassing those in good condition,” the ASCE wrote. “As bridges in fair condition continue to age – presenting the possibility of being further downgraded – they also exemplify an opportunity because they can be preserved at a lower cost than bridges in poor condition.”

Bridges received a significant amount of funding through the Infrastructure Investment and Jobs Act (IIJA), which included $27.5 billion for the Bridge Formula Program and $12.5 billion for the Bridge Investment Program.

“Despite this infusion of federal funding, bridge-related system rehabilitation needs are estimated at $191 billion,” the ASCE wrote. “Therefore, strategic asset management planning and routine maintenance are essential to keeping bridge conditions from further declining and avoiding costly repair or rehabilitation work. While the effects of extreme weather events pose threats to bridges, innovative techniques are improving their security and resilience.”

As we wait to see if innovations like FIU’s spray-on concrete system, or Allium’s stainless-steel-clad rebar truly revolutionize bridge construction and maintenance, it’s important that you know exactly where all reinforcements are within bridge decks and other concrete slabs before you attempt to cut or core that concrete.

Striking rebar, post tension cables or other support systems within concrete can lead to catastrophic structural failure that endangers you and your workers, and anyone else in the vicinity of your job site.

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