Experts peer into Pa. potholes

This winter has been a bad one for potholes. An engineeing professor at Villanova University took her research on some of the area's roads to find out more. Story, B8.
This winter has been a bad one for potholes. An engineeing professor at Villanova University took her research on some of the area's roads to find out more. Story, B8. (ED HILLE / Staff Photographer)
Posted: March 13, 2014

If you are sick of dodging the axle-busting, tire-flattening potholes that seem to be everywhere, get over it - the craters are likely here until late spring, experts say.

"We are fighting Mother Nature," said Leslie A. McCarthy, a Villanova University engineering professor whose research includes pavement design and construction.

This year, pothole season began early, on Jan. 6, when temperatures in the region went from freezing into the 60s and back into the teens, according to state Department of Transportation spokesman Gene Blaum.

The department's repair crews have used more than 4,500 tons of pothole-patching materials - about three times as much as in each of the last two years - and spent more than the $2.5 million budgeted for such repairs.

AAA estimates that pothole damage to cars is one reason its calls for general roadside assistance shot up 63 percent at the start of this year over the same two-month period from last year.

McCarthy said she used the pothole-scarred Blue Route as a research lab this January. With her husband at the wheel and their two children in car seats, McCarthy used her cellphone camera to document the developing potholes along the upper part of the road and how long it took them to open again after they had been fixed.

"We saw those potholes open up again," she said.

Potholes develop when water seeps into tiny cracks in the roadway, freezes, and then thaws, loosening the pavement. Add a weather pattern similar to this winter's - a polar vortex followed by warm, wet weather - and it creates the perfect conditions for road materials to fail, she said.

Think Rice Krispies treats, the professor said. Soak one of the gooey, marshmallow-laden bars in water, then freeze it.

The result is similar to what happens in pavement. When the pavement begins to break down, the weight of passing trucks will take care of the rest.

The damage from one three-axle tractor-trailer is equal to about 4,000 passes from passenger cars. That is why many potholes are in the wheel path of the trucks, she said.

"Cars don't create the damage," said McCarthy.

Once the freeze is over, snow melt and spring rains will begin to take their toll on the roads as the high water table penetrates into pavement cracks.

Damage won't be to highways or turnpikes, which are built to ensure water runs off, according to McCarthy. Rather, it will be concentrated on heavily traveled roads in flood-prone areas.

She cited ongoing projects aimed at coming up with the best way to patch or prevent potholes. For instance, she said, the Ohio Department of Transportation is looking into using a mobile tow-behind unit, which uses infrared technology to heat up potholes and add a hot patching mix.

The issue is likely to be on the minds of motorists and public officials for weeks to come. On Wednesday, Delaware County officials are scheduled to announce that they will share some of their Liquid Fuels Funds with the county's 49 municipalities to help with pothole repairs.



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