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. Last Updated: 07/27/2016

U.S. Asphalt Researchers Wage War On Potholes




PULLMAN, Washington (AP) -- Each day, Tom Papagiannakis and Eyad Masad wrestle with their own version of the classic question about the chicken crossing the road.


Only there's no chicken.


The question the Washington State University civil engineering professors ask is this: Why did the pothole form in the road?


Or, more precisely: Where did a mistake occur that led to the pothole's formation - in the selection and mixing of the asphalt's aggregate and binders, or in the placement of the materials on the road bed?


Early spring is the harshest season for northern roads. Road beds frozen solid in the winter become soggy and vulnerable when they thaw.


"We could prevent those potholes if people agreed to stay off the roads for two weeks at the end of March," Papagiannakis says. "But I don't think that's going to be done."


The professors are believers in Superpave, a road-building approach pioneered in the late 1980s and early '90s through a $50 million U.S. government research program at government and university labs nationwide.


Superpave is not a new type of pavement, but a new way of designing it. Using exact specifications, engineers can now tailor the asphalt mix to the climate and traffic conditions.


The Superpave approach helps equip experts like the WSU professors with the answers paving crews seek as they try to extend the life of highways carrying ever-larger trucks and more traffic.


How do you prevent "shoving" that occurs when the force of vehicles stopping at traffic lights leaves ruts in the asphalt? Make sure the rocks in the mix are angular rather than round, and be careful to tightly bind them with liquid asphalt.


How to keep pavement from cracking in freezing conditions? Choose an extremely strong binder, for starters.


Papagiannakis and Masad consider Superpave the biggest advance in the field since the late 1940s.


"It put us on the right track to look at the scientific reasons behind pavement failures," Masad says.


The university's role in promoting Superpave got a boost with the Feb. 1 opening of the Washington Center for Asphalt Technology, headed by Papagiannakis and Masad.


The center features $300,000 in equipment that allows the professors to design asphalt mixes to meet Superpave specifications. The gear also enables the center to test asphalt core samples from roads and highways that developed potholes and other problems for microscopic clues as to what went wrong.


In Washington, a fifth of the state's major roads projects use Superpave methods, with plans to completely switch over by 2005, Pierce says.


Costs for the state's first Superpave projects were higher than with traditional methods. But the difference is negligible now that highway officials and contractors are familiar with the new process, Pierce says.


"Contractors like it, and we like it," she says.