PHOENIX-Rubberized asphalt may be controversial in Congress, but it's going strong in the state where it was invented. Congress has cut off funding for the promotion and enforcement of a provision in a 1991 highway law that requires states to begin using rubberized asphalt this year.
But whether or not there's a federal mandate, Arizona plans to continue its use of the paving material.
``We concluded a long time ago that crumb-rubber-modified (CRM) asphalt is a benefit to our state,'' said George Way, pavement section engineer with the Arizona Department of Transportation (ADOT).
``It's the only material we've found that really prevents reflective cracking. Though recycling is a worthy goal, it's not the prime reason we use rubberized asphalt.''
Arizona now has more than 800 miles of road-slightly over 10 percent of its highway system-paved with rubberized asphalt, Mr. Way said. Last year the state ordered about 13,000 tons of CRM binder-about 15 percent of its paving material procurement-and has no plans to cut back.
Reflective cracking-cracks which begin in the old pavement below and spread to new pavement overlaid above-has long been the bane of highway engineers.
In an effort to reduce such cracking, Charles MacDonald, a materials engineer for the City of Phoenix, began experimenting with rubber additives to asphalt in the early 1960s. Mr. MacDonald's mixture was first applied to Phoenix streets in the mid-1960s, with experimental use on Arizona highways soon thereafter.
Although other methods of mixing rubber with asphalt have been developed, Arizona still uses the McDonald method more often than any other, Mr. Way said. ``It's the one we're most familiar with, and we have the best track record of performance with it.''
At this time, there are two major contractors to ADOT for asphalt rubber. One, International Surfacings Inc. (ISI) of Tempe, Ariz., was founded in 1983 from the merger of two older firms and, in one incarnation or another, has supplied the state with rubberized asphalt since the technology began.
The other, FNF Construction of Chandler, Ariz., is a large highway construction firm that added rubberized asphalt to its product line when the patents on CRM technology started lapsing a few years ago.
Until the late 1980s, ISI supplied mostly ``chip seal'' or spray-applied rubberized asphalt, according to Technical Director Joe Cano. Since then, however, the product has been mostly hot mix.
``When you spray-apply, the flying chips are a nuisance, and a lot of people complain,'' Mr. Cano said. ``Hot mix is more expensive, but it adds structure to the pavement, improves ride and skid resistance, reduces traffic noise and is more acceptable to the public.''
In hot mix, the crumb rubber is dispersed into the hot asphalt binder, which is then mixed with stone aggregate. The resultant mixture is applied while still hot.
FNF first started using rubberized asphalt in 1989 because so many ADOT contracts required its use, according to company CEO Jed Billings.
The big advantage to rubber in asphalt is that you can put more binder in the mix, which creates a longer-lasting pavement, he said.
Since the patents lapsed on rubberized asphalt technology, the prices have dropped closer to those of conventional asphalt, according to FNF. In the late 1980s, the average low bid on a rubberized asphalt contract was $500 per ton. By 1992, that price had dropped to $325 per ton.
``As more contractors...enter the asphalt rubber field, the cost should continue to drop, making the greater durability of the material all the more apparent,'' FNF said.
Highway officials in many other states, however, have little understanding of or tolerance for rubberized asphalt. Together with makers of conventional asphalt, they have balked at Section 1038 of the Intermodal Surface Transportation Efficiency Act, which requires the states to use an increasing percentage of asphalt rubber in federally funded highway projects or risk losing federal highway money.
Last fall, Rep. Bob Carr, D-Mich., introduced an anti-1038 provision into the Transportation Department appropriations bill. The amendment, which forbids the Federal Highway Administration from using any of its funds to promote or enforce Section 1038 in fiscal 1994, passed along with the rest of the bill.
``Carr has publicly stated he will include the anti-funding provision in next year's DOT appropriations as well,'' said Sean Reed of the Rubber Pavements Association in Washington.
The funding moratorium has several negative effects, Mr. Reed said, but two in particular: It prevents state highway officials from learning about rubberized asphalt in a gradual, systematic way, and; it forbids using federal funds for technology transfers.
The uncertainty of Section 1038's fate and the accompanying bad publicity Mr. Carr and other legislators are giving asphalt rubber are a great concern for the industry, said ISI's Mr. Cano.
``We are selling a product we know has a long history of showing strong advantages,'' he said. ``But in the backlash we're getting, people are not looking at those advantages. This will be a problem for us, and it is not very healthy.''
Mr. Billings of FNF opposes Section 1038 because some state highway officials, miffed at the federal mandate, have little interest in proving that rubberized asphalt works.
``Like any product, you can have a failure with asphalt rubber,'' Mr. Billings said. ``If the design isn't adequate, it's not going to work, and we don't want to be part of (such a project).''
He cited a recent project in Michigan that failed because the state used the wrong process and laid the pavement in weather that was too cold and rainy.
``No state should use asphalt rubber if it doesn't want to,'' Mr. Billings said. ``But those states are the ones that will miss out. Progressive states (including Arizona, California, Florida and Kansas) will continue to get good results with the product.''
Mr. Way said ADOT is trying to maintain ``a certain degree of neutrality'' in the Section 1038 debate.
``We understand the other states' objections to 1038,'' he said. ``No state likes facing mandates of any kind, and Arizona is no exception. But we've had good results with the material, and we're willing to share our expertise with any state that asks for it.''