On the Road To Highway Repairs
KA-THUMP!
Never mind that Lou Papet is chief of the United States Federal Highway Administration's pavement division. When he drives to work (KA-THUMP), like every other Washington commuter, he has to endure potholes.
``New York Avenue is notorious for potholes,'' he says.
Still, Mr. Papet is upbeat, even after this year's severe winter. New technology is helping to win the battle against the pothole.
Take asphalt. For years, highway departments mixed the stuff to make it easy to work with. But they had little way of knowing which mixes were most durable for specific climates. That's changing now, thanks to a five-year federal initiative called the Strategic Highway Research Program (SHRP).
Among the 230 reports and 130 products that came out of its research, SHRP has developed Superpave. This system of asphalt tests and specifications gives contractors a much better idea of what to use and when to use it.
Researchers have also tested additives, such as polyurethane, that allow asphalt to better resist rutting in the summer and cracking in the winter. Damian Kulash, SHRP's executive director, expects these technologies will extend the life of new asphalt roads by at least 5 percent.
That would mean big savings. Since the United States already spends some $10 billion a year on asphalt pavements, Superpave could save some $500 million annually. More than 40 states have chipped in to buy the new testing equipment. Within a couple of years, Mr. Kulash expects most of them will be able to start taking a more scientific approach to asphalt paving.
``We have made a lot of progress,'' says Vincent Janoo of the Cold Regions Research and Engineering Laboratory in Hanover, N.H., part of the US Army Corps of Engineers. And not only in asphalt. Mr. Janoo thinks concrete has made at least as much progress.
Last month, the lab laid down 40 yards of ``antifreeze''-treated cement in Sault Ste. Marie, Mich. Despite temperatures as low as 10 degrees F., workmen were able to lay it without resorting to the heated structures usually required at such low temperatures. So far the concrete has performed at least as well as conventional concrete.
``We can make concrete think it's sitting in Florida instead of Alaska,'' says Charles Korhonen, research civil engineer at the Cold Regions lab. If the new ``antifreeze'' can lower by 18 degrees the acceptable temperatures for pouring cement, it would extend the construction season 2-1/2 months in a northern climate like New Hampshire, he adds. That should make concrete pavement more cost-competitive with asphalt, which can't be laid down in temperatures much under 40 degrees.
Researchers are also working on better pothole patches - even though they disagree on what works best. The Cold Regions lab advocates a ``go-slow, do-it-right'' approach. That means cutting the pavement around the pothole to make it square, drying the hole, cleaning it, then filling it up with asphalt and compacting it.
But preliminary results from SHRP's three-year, 1,250-pothole study suggest a ``dump-and-run'' alternative is effective. Typically, highway-repair crews are too rushed to use the ``go-slow'' approach. Unfortunately, they use cheap cold-mix asphalt. SHRP found that dump-and-run techniques can work if crews use high-quality patching materials. These patches often lasted two to three years, while some of the local mixes failed almost immediately and had to be replaced four and five times. Of course, the new materials are up to three times more expensive.
All these technologies should soon make the spring pothole season more bearable. Ultimately, though, even better-designed roads will break down without proper maintenance, Mr. Papet warns.
``There is no such thing as indestructible pavement,'' says the pothole veteran of New York Avenue.
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