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Pitfalls of potholes

PULLMAN, Wash. (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?

It's a question the pavement sleuths frequently get from highway officials this time of year - "the evil season," as Papagiannakis calls it, when potholes can make a Sunday drive seem like a trip on the highway to hell.

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."

So Papagiannakis and Masad look for other ways to stretch the public's road funds as politicians talk of cutting gas taxes to ease the sting of rising fuel prices.

The professors are believers in Superpave, a road-building approach pioneered in the late 1980s and early '90s through a $50 million federal 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 who once took a largely one-size-fits-all approach to road building now can 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 to 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.

WSU'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, supported in part by donations from the road-construction industry and state Department of Transportation, features $300,000 in equipment that allows the professors to design asphalt mixes to meet Superpave specifications.

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