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"When the cracks are completely caulked and no more water can enter, the fungi will again form spores," Jin said. "If cracks form again and environmental conditions become favorable, the spores could wake up and repeat the process."

To repair existing structures, the spores would be put into a liquid that is then sprayed into cracks.

The research is at an early stage. More studies are needed to determine how the T. reesei spores affect concrete's strength and permeability, as well as how long the spores can survive within concrete.

But especially given the cost of inspecting concrete structures on a regular basis, as well as the challenges associated with fixing bridges and other structures that are in continuous service, Jin said self-healing concrete could be a good solution to a vexing problem.

"We are confident that this will really work as a low-cost, pollution-free, and sustainable approach," she said.

What do other infrastructure experts make of the new research? Kristina Swallow, president of the American Society of Civil Engineers, sounded cautiously optimistic in an email to MACH.

"It's hard to quantify how impactful this could be," she said, adding that self-healing concrete was now a hot research topic. "However, one promising aspect of this new solution is that it can fill the smallest of cracks, therefore preventing it from growing — and with it, the cost to fix it."

Whether self-repairing concrete pans out as Jin and her collaborators at Binghamton and Rutgers University expect it to, there's little doubt that our nation's infrastructure is in a sorry state.

In the society's 2017 "Infrastructure Report Card," U.S. infrastructure earned an overall grade of D-plus. "Over the next 10 years," Swallow said, "the U.S. needs to increase our investment in infrastructure by $2 trillion across all levels of government and the private sector."

A paper describing the research was published in the March 10, 2018 issue of the journal Construction and Building Materials.

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