Highways may not be the only places where Valley residents will witness science's march forward in the technology of rubberized paving.
Rubberized asphalt will eventually cover more of U.S. 60, Loop 101 and Loop 202.
The material, made in large part with recycled tires, provides a surface that makes for smoother, quieter driving. It's also expected to be more durable than conventional road pavements.
Recycled rubber is also the key ingredient in a similar aggregate that one day could replace conventional concrete pavement for sidewalks, sports courts, driveways, parking lots and bike paths.
Research led by Arizona State University's Advanced Pavements Lab is raising hopes that rubberized concrete can prove a more efficient, sustainable and environmentally beneficial paving alternative.
“We are only in the early experimental stages. A lot of testing still needs to be done,” said Kamil Kaloush, a professor in ASU's Department of Civil and Environmental Engineering.
But several demonstration projects, including a sidewalk at Kaloush's Scottsdale home, are producing promising results.
Four years ago, Han Zhu, then an engineering researcher at ASU, designed a stretch of rubberized concrete sidewalk constructed on campus. Lighter and more skid-resistant than other types of concrete, the material also showed more resistance to cracking and other typical wear and tear. The finding has since been confirmed in using the material for loading docks at a trucking company, driveways, sidewalks, wheelchair ramps and patios.
The largest test site is a tennis court at architect Robert Fairburn's home below Camelback Mountain. About 2,500 tires and 30,000 pounds of rubber were used in the resurfacing mix.
Fairburn and his wife, Barbara, avid tennis players, give it a thumbs-up as a solid but comfortably playable court. More important, the architect said he sees potential structural uses for rubberized concrete — for roofs, floors, stairways and nonload-bearing walls.
Besides the benefit of a productive use for some of the hundreds of millions of old tires in dumps around the country, rubberized concrete can be economical since less of it is needed for paving purposes than conventional materials, Fairburn said.
There's another possible environmental benefit. Rubberized concrete radiates less heat than standard concrete. If the rubberized mix were widely used, it might help reduce the urban heat-island effect that adds a few degrees to the Valley's torrid temperatures, Karoush said.
He hopes to test it next on golf cart paths at Marriott's Camelback Golf Course in Paradise Valley. But bigger applications are necessary to get conclusive evidence of rubberized concrete's flexibility and durability, he said.
Although Ford Motor Co. donated old tires for the tennis court and other assistance has come from the Arizona Department of Transportation and a few cement and rubber industry groups, more support is critical.
“Everything's been done on a shoestring budget so far,’’ said ADOT pavement engineer George Way. “To make progress from this point on will take a lot more funding.’’