VICKSBURG, Miss. - Dodging damaging road and runway potholes challenges military and civilian pilots and drivers daily. This issue led researchers at the U.S. Army Engineer Research and Development Center’s (ERDC) Geotechnical and Structures Laboratory (GSL) to develop materials for quicker and longer-lasting repairs.
Funded by the Air Force Civil Engineer Center and patented in March 2021, the “Performance Grade Asphalt Repair Composition” — commonly known as the Army’s induction hot mix asphalt, or iHMA — resulted from research efforts utilizing ERDC’s extensive testing facilities to support fighter jet traffic.
“Personnel responsible for pavement maintenance will benefit from this pothole fill invented for year-round use,” said Dr. John Rushing, research civil engineer and product lead inventor with GSL’s Engineering Systems and Materials Division Research Group.
“iHMA is an asphalt repair material packaged in five-gallon containers that is heated on-demand at the repair site using an induction heating system,” he explained. “The mixture is heated to around 300 degrees in three to five minutes, offering a hot repair solution similar to plant-produced asphalt mixtures.”
The main advantage of the composition is the lack of limits on ambient temperatures, says Rushing.
“The invention offers a ‘do it right and do it once’ solution that has not been available,” he said. “This new formulation offers superior quality in a product that can be used any time of year, any place in the world, and it doesn’t have a limited shelf life.”
Co-inventors and creators of this unique asphalt formulation include Web Floyd and Dr. Ben Cox, both research civil engineers in GSL’s Airfields and Pavements Branch, and Dr. Craig Rutland, a pavements engineer for the U.S. Air Force Civil Engineer Center (AFCEC).
The team received the U.S. Army Corps of Engineer’s nationally-competitive Innovation of the Year Award at 2019’s Innovation Summit held at ERDC’s headquarters in Vicksburg, Mississippi. They will also be honored at a patent presentation ceremony later this year by ERDC’s Office of Research and Technology Transfer which processes patents for the center.
Their innovative research addresses both safety and cost concerns.
Pothole Damages in the Billions
A study from the non-profit American Automobile Association’s (AAA) Washington State Office revealed pothole damages from 2011-2016 cost U.S. drivers $15 billion in vehicle repairs, or approximately three billion annually.
“In those five years,16 million drivers across the country suffered pothole damage to their vehicles,” says John Nielsen, managing director of AAA’s Automotive Engineering and Repair. “The problems ranged from tire punctures and bent wheels, to more expensive suspension damage.”
Reporting that two-thirds of Americans surveyed expressed concerns about local roadway potholes, AAA cautioned drivers to remain alert to avoid pothole damage and urged state and local governments to fully fund and prioritize road maintenance, to reduce vehicle damage, costs and driver frustration.
Rushing says, iHMA can offer future solutions. “We have licensed the technology to NecoTech to commercialize the system; we hope to soon be able to offer this formulation to the broad market.”
Brainstorming Spurs Solutions
The lack of structurally-adequate commercially available repair materials for maintaining airfield pavements led to the iHMA invention.
“Multiple studies at ERDC showed that these commercially available repair methods survived fewer than 10 repetitions of a military aircraft load before they failed, as defined by rutting or inability to support the load,” Rushing explained. “All of the efforts for conductive heating failed to meet the time requirement for a rapid solution. It was in a brainstorming session that the idea of induction heating was discussed.”
“Commercial products are applied cold, so the team desired materials like those produced in a hot mix asphalt plant, but heating the material was the most significant challenge,” he continued. “The concept is similar to how a microwave works. This method is used in many industrial processes to rapidly generate very high temperatures with no physical contact of materials. High-energy electromagnetic radiation energizes certain particles from a distance.”
From Concept to Successful Prototype
Using ERDC’s world-class pavement materials laboratory and full-scale testing facilities, in-house proof exercises involved simulated traffic from a F-15 fighter jet. For advanced material refinements, the team explored many sources of materials, including steel, to investigate heating efficiency impacts by shape, size and volume. The target was heating the mixture in a five-gallon container to 300 degrees in fewer than five minutes.
“We designed a unique container that wouldn’t interfere with the induction frequencies, acquired our own laboratory testing capabilities and finalized the design,” said Rushing. “We also developed a field heating system that would be used in a real-world repair scenario to get the product hot.”
“Final validation came while immediately testing several repairs by applying the simulated aircraft traffic at the ERDC outdoor pavements test facility, using the mix meeting Federal guidelines,” he continued. “Our target goal of 100 repetitions of aircraft loads within two hours of this placement was exceeded. These pre-packaged, on-demand asphalt mixture canisters with nearly unlimited shelf life will allow cold weather road repairs previously unworkable in freezing conditions.”
“We tested the system in sub-freezing temperatures in winter in Northern Canada to prove this concept. Remote locations can now get hot asphalt materials without consideration of the distance from a local plant. In only a couple of minutes, a container of asphalt mixed with the steel particles achieved temperatures in the range desired,” Rushing said.
The team anticipates the product’s valuable support for military base maintenance across the world, but also foresees broad application for any agency’s road repair responsibilities.
Pavement possibilities using iHMA
“This innovation allows engineers to generate small patches that withstand the high tire pressures of today's fighter aircraft in a short amount of time in a wide variety of environments and in the most remote locations,” said Rutland, the pavements subject matter expert for the sponsoring AFCEC. "In addition, it points to the potential of this technology in a wide variety of applications and potentially doing so with renewable energy."
“With the commercialization strategy developed and licensing agreement signed in 2020, we hope to make this solution available to the public as well as the military in the near future,” added Rushing, advancing a welcomed, longer-lasting outlook for pothole repairs.