April showers bring May flowers, but lousy Smarch weather brings big honkin' potholes.
Yes, it’s that time of year again, when it looks like someone took a cheese grater to roads all over the coldest, wettest parts of the continent. You’ve got the wonder: We’ve launched a car into space, but still can’t keep a hole in the pavement filled for longer than a month.
Scientists around the world have been pondering the problem of potholes for decades—and as it turns out, we might be just a few years away from more long-lasting solutions than the current method, which involves throwing some stuff in a hole and running over it a few times with a truck.
Larry Zanko has been thinking about potholes for the better part of three decades. He’s a geological mining engineer and senior fellow at the University of Minnesota Duluth’s Natural Resources Research Institute.
He’s working on two different technologies, both of which use magnetite, an iron ore sourced from Minnesota’s iron mines. Tests of both pothole-patching solutions held up for more than a year, and several years in some cases.
The first method uses microwaves to heat potholes and surrounding pavement before filling them with a mix of magnetite and recycled asphalt; the final step is nuking the patch to create a seal. Pre-heating the ground and then microwaving the magnetite-infused patch makes for a stronger repair, Zanko told me over the phone: “The pavement surrounding the hole and the repair compound bond and become one.”
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But it only works on asphalt roads. The second solution—which Zanko calls Rapid Patch—works on both concrete and asphalt. It’s a water-activated magnetite-and-aggregate mix that simply gets poured into a pothole, no heating required. A patch can be driven over within 30 minutes of repair, Zanko said.
He’s been working with the state’s Department of Transportation and two companies to test the technologies and hopes to commercialize them within the next few years.
Of course, filling potholes is a band-aid solution in a country whose road infrastructure scored a D grade in the American Society of Civil Engineers’ 2017 Infrastructure Report Card. According to the report, 21 percent of US roads are in poor condition and the country has an $836-billion backlog of highway and bridge capital needs.
The ideal scenario would be to have roads that don’t fall apart in the first place.
That’s what Etienne Jeoffroy and colleagues are working on at the Swiss university ETH Zurich, in collaboration with the Laboratory for Road Engineering at the Swiss research institute EMPA.
His team discovered that adding magnetic nanoparticles such as as iron oxide to bitumen—which, when combined with mineral stones forms asphalt—and then using a magnetic field to “excite” the particles would cause the bitumen to warm up. This would make it melt, closing microcracks before they become a problem.
“The idea is to heat up the road once a year to close up any microcracks,” Jeoffroy told me in a WhatsApp exchange. “As long as the microcracks are closed early enough, no pothole.”
Somewhat similarly, a team at Binghamton University—State University Of New York is looking at adding fungus to concrete to enable self-healing. Researcher and assistant professor of mechanical engineering Congrui Jin told Science Daily earlier this year that the fungus could be preemptively mixed into concrete. When oxygen and water seep in, the fungus would produce spores to fill any microcracks.
It may take a while to see these technologies in action. Jeoffroy said testing on a few meters of public road is about to begin, but that it could take another decade to see commercialization and widespread adoption.
Still, it’s not like these scientists are going to miss the boat. According to the ASCE’s latest Infrastructure Report Card, the US highway network alone currently requires more than $420 billion worth of repairs. It’s going to take years, and maybe even generations, to do all that roadwork.
In that sense, a little structural self-healing would go a long way. Plus, it sure beats watching three workers take three hours to fix a single pothole.
Correction: An earlier version of this story mistakenly identified bitumen as asphalt. Motherboard regrets the error.
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