The material is made from asphalt that is milled and collected during road construction projects. The millings are crushed, ground and injected with oil and water before being applied and rolled. The road is sealed with tar and chips or a thin layer of asphalt.The approach has been used for almost 40 years, but resurges every time oil costs rise:
"It's softer than (traditional) asphalt, so you can't use it on busy roads," [Pennsylvania DOT executive Jeff] Karr said. "But it's perfect for back roads that have become deformed."
Karr said the district will use 45,000 to 60,000 tons of recycled asphalt this year to pave up to 27 miles of road. Using the recycled asphalt will cost $40,000 to $60,000 a mile, compared with $250,000 to $400,000 a mile for traditional asphalt, he said.
Although local PennDOT districts just recently started rebuilding roads with recycled asphalt, it's been done elsewhere since the 1970s, said Dave Newcomb, vice president for research and technology at the National Asphalt Pavement Association in Lanham, Md. About 100 million tons of asphalt are recycled each year, the association says.
The oil embargo drove its early use, Newcomb said. Asphalt is a by-product of oil refining. Interest was renewed in 2006 and 2007 when fuel prices soared, Newcomb said.
"It's a win-win for everyone," Newcomb said. "Departments of transportation are saving money, and it's definitely a good thing environmentally, in terms of there being less aggregate (used in asphalt) being taken out of quarries and the oil saved. The beauty is, you can continually recycle."