OAK RIDGE, Tenn., May 13, 1997 -- There's nothing like a pothole to slosh that cup of coffee onto your lap or help keep your favorite alignment shop in business, but a new method for fixing those nasty craters could make driving a little more enjoyable and less expensive.
The new technique, being developed by researchers at the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL), uses microwaves to heat the area to be fixed and the asphalt used to fill the hole. Repairs are seamless and expected to be much stronger than those done by merely compacting hot asphalt into a hole. More effective repairs could greatly extend the lifespan of roads.
"If the process is developed and applied on a national scale, perhaps billions of dollars in roadway maintenance costs could be saved," said Tim Bigelow, co-developer of the microwave repair technique and a member of the Fusion Energy Division.
Equally important, microwave technology can be used to detect cracks and flaws beneath asphalt and concrete, before they surface and cause problems.
"Not only can our system do a better job of repairing potholes, but it can prevent them from forming in the first place," Bigelow said. "It's a lot easier to fix cracks before the roadway deteriorates, so that could lead to dramatic savings."
The flaw detection system works by probing through road surfaces using "radar-like" techniques to send a signal into the surface and looking for reflected power.
"Using time delay or using swept frequency can provide depth profile data," Bigelow said. "By scanning the antenna along the asphalt surface, we can look for changes that indicate underlying problems that may not be visible on the surface."
Although potholes may seem like mere annoyances, some cities actually have "pothole repair hotlines." In Knoxville, a city of 165,000, the pothole hotline receives thousands of calls per year, according to Bob Whetsel, public service director.
"We generate a work order whenever we get a call from someone reporting a pothole," Whetsel said. Last year, the city spent $188,368 to repair nearly 23,000 potholes along Knoxville's 1,000 miles of roads. Northern cities, which are subjected to colder winters and more temperature extremes, typically have an even bigger problem with potholes.
ORNL's microwave repair technique could be used with a hand-operated applicator or scaled up to a high power truck-mounted system. The microwave technique could also be used to seal joints between old and new material, making for seamless repairs when utilities have to be installed or between highway lanes that are paved individually.
Another benefit of using microwaves is that the repairs can be made using cold material, thereby saving the expense and trouble of hauling heated asphalt to the potholes. And the repairs can be made throughout the year instead of primarily in warmer months.
Bigelow and co-developer Terry White are satisfied that their system is superior; next they hope to do field testing and gather life cycle costs to support their belief that microwave asphalt repair has economic advantages.
"Small-scale applications would provide the quickest payoff," Bigelow said. "We need support from paving manufacturers and highway maintenance organizations to gather information about larger scale use of this technology."
The research, which is a spinoff from a microwave decontamination process developed a few years ago by White, was funded by DOE's Office of Technology Development and from ORNL director's discretionary funding.
ORNL, one of DOE's multiprogram research facilities, is managed by Lockheed Martin Energy Research Corporation.