Riding on Wastes

Every year, 100 million worn rubber tires and 26 billion nonreturnable glass bottles are discarded in the U.S. Disposing of them is a formidable problem, usually resolved by burning evil-smelling mountains of tires and burying tons of splintered glass. But there soon may be a neater and more practical solution: using the unsightly, troublesome waste products as construction materials in the 20,000 miles of highways that are built annually in the U.S.

In testimony before the Senate Committee on Public Works last week, Richard L. Cheney, executive director of the Glass Container Manufacturers Institute, called attention to an experimental product called "glasphalt." Developed at the University of Missouri, it uses finely ground glass granules to replace the rock aggregates now used as a construction material for highways. One 58-foot-long test strip of glasphalt pavement, outside the Owens-Illinois Technical Center in Toledo, has held up well during the worst winter in years; engineers reported virtually no cracking, rippling or holes in the surface and gave it a top rating for skid resistance.

Liquid Latex Pavement. At Texas A. & M., Research Engineer Douglas Bynum, 35, is testing his theory that the rubber in discarded tires might give asphalt added flexibility and more resistance to cracking. Working in the university's Transportation Institute, Bynum prepared samples of asphalt combined with ground-up rubber obtained from old tires. Test results showed that the powdered rubber--used as a binding material--increases asphalt's overall cohesiveness so that it does not split when roadbeds shift slightly or sink. Bynum's findings seem to be a natural outgrowth of experiments by the rubber industry. Goodyear, for example, has discovered that liquid latex--not a waste product--improves the durability and traction of highway pavement.

Nonetheless, there are several remaining obstacles to waste-product highways. It may prove impractical to separate tires and bottles from other refuse. Processing plants to grind the materials to the right size and shape may be too costly. And highway builders must still be convinced that the new aggregates are effective. But Bynum is optimistic: "I think sheer economics favors the idea," he says. "We could save the money we spend to dispose of these materials and get better highways."

Best of all, Bynum says, there would be no foreseeable shortage of materials for the improved roads. Combined with asphalt, the old tires and bottles disposed of in 1970 could pave a freeway that would span the U.S. 23 times.

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