WASHINGTON—In 1991, a multi-year transportation funding bill mandated the use of crumb rubber asphalt in road projects funded by the federal government. After several successful efforts to postpone the mandate's implementation, it was killed in 1995 with the passage of a law creating a National Highway System. But funds for asphalt rubber research and technology transfer remained.
Today, with research budgets in the Federal Highway Administration slashed, even the agency's studies mandated by law have been halted.
Despite all the roadblocks, asphalt rubber technology survives and grows slowly but surely.
Arizona, California and Florida—enthusiastic converts to rubberized asphalt technology—continue to use the surface wherever the paving material's longer life justify its double cost over conventional asphalt.
Tennessee, Texas and New Mexico also are experimenting with asphalt rubber and reporting encouraging results.
At this point, the main question about rubberized asphalt is whether its use will spread significantly beyond the areas where it already has gained popularity.
Billy Higgins, director of government relations at the American Association of State Highway and Transportation Officials, doubts it. ``Sometimes the climate has a lot to do with it,'' he said. ``I don't see it moving much beyond the southern tier of states.''
Mr. Higgins cited an asphalt rubber demonstration project in Michigan that turned out poorly. But that took place 15 to 20 years ago, he said.
Others are bullish on asphalt rubber, including Robert H. Snyder, retired vice president of tire technology at the former Uniroyal Inc.
``I think it will gain acceptance, and it will move further north,'' Mr. Snyder said. ``It raises the cost of a paving operation, but it will pay.''
Section 1038 of the Intermodal Surface Transportation Efficiency Act of 1991 was the brainchild of Sen. John Chafee, R-R.I., who wanted to maximize the productive use of scrap tires.
Among other things, the provision placed strict quotas on state highway departments as a prerequisite for keeping federal highway funds.
At least 5 percent of all pavements funded by federal money had to include asphalt rubber. The percentage rose 5 percent per year, reaching 20 percent by fiscal year 1997.
The state highway and transportation officials and conventional asphalt manufacturers objected to Section 1038. Rep. Bob Carr, D-Mich., placed a rider on transportation department appropriations, forbidding the highway administration to use any of its funds to enforce the asphalt rubber quota.
State highway officials had no qualms about using asphalt rubber and still don't, Mr. Higgins insists.
The higher cost of asphalt rubber meant highway dollars couldn't be stretched as far as with standard paving materials.
The Carr amendment was added to three successive transportation department spending bills, until President Clinton signed the National Highway System bill, killing the quota on rubberized asphalt.
The highway system law kept in place Section 1038 requirements for continuing research and technology transfer. But the loss of the asphalt rubber mandate also meant a loss of impetus for federal research.
Four years ago, the highway administration contracted out a study to create guidelines for a new type of rubberized asphalt technology, according to Robert Davies, a Federal Highway Administration research highway engineer.
That mixed-design technology was intended to be a simple start-up asphalt rubber system for states with little experience with the surface material.
The highway system bill and other legislation squelched ``unfunded mandates,'' including asphalt rubber research, said Michael Heitzman, a pavement engineer with the Federal Highway Administration.
The study was funded partly by pooled funds from the states, and the states could have chosen to keep it alive, according to Messrs. Heitzman and Davies. But when the agency polled the states about the study, those who responded ``agreed they didn't see the need to spend more money,'' Mr. Davies said.
Eventually, the FHA decided to ``recapture'' the money not spent and determine how to proceed. The agency is looking at the potential for chemically modified crumb rubber asphalt, Mr. Davies said.
The Rubber Pavements Association, a Tempe, Ariz.-based industry organization, is funding its own studies. Gary Hicks, formerly in the FHA-funded study, serves as the lead researcher.
One of the RPA studies measures the performance and life-cycle costs of asphalt rubber pavements in California, Arizona and Florida against that of conventional asphalt and polymer-modified hot mix, said Mr. Hicks, a member of the RPA Advisory Committee and a professor emeritus at Oregon State University. The other measures the laboratory properties of rubber-modified asphalt binders.
The RPA is interested in seeing the highway administration study completed, and there may be a possibility that will happen, Mr. Hicks said.
But observers generally agree the controversy over the federal mandate not only hampered research, but also wider acceptance of asphalt rubber as an alternative to conventional paving.
``That regulation interfered with everything,'' Mr. Snyder said.
Those states using rubberized asphalt continue to be its champions, and their enthusiasm is spreading to neighboring states.
Arizona's most recent report on rubberized asphalt—performed by George Way, design engineer with the Arizona Department of Transportation Pavement Division—shows the state has paved 1,100 miles of road with asphalt rubber since 1988.
``In tons, that amounts to about 120,000 tons of asphalt rubber binder, all about 20-percent rubber by weight,'' said Mr. Way, a technical adviser to the RPA.
Because of the material's higher cost, Arizona will not use asphalt rubber in paving projects where it's not economical or practical, Mr. Way said. Even so, the state ends up using rubber-modified paving materials 70 to 80 percent of the time.
Asphalt rubber protects against reflective cracking, in which the top layer of pavement develops the same cracking patterns as the pavement beneath, Mr. Way said.
``It gives a more durable surface, has better aging properties, provides a good ride, requires less maintenance, offers good skid resistance and reduces noise,'' he said.
California and Florida wouldn't release figures on how much rubberized asphalt they've used. Both are long-term users of the material—California since 1978, and Florida since 1988.
The California Department of Transportation generally uses asphalt rubber in pavement rehabilitation projects, according to Bob Doty of the Pavement Branch of CalTrans Headquarters Laboratory in Sacramento, Calif.
In California, the decision to use asphalt rubber is made on a case-by-case basis, according to Mr. Doty.
While percentages vary from year to year, most recently CalTrans has used asphalt rubber in 10 to 15 percent of the pavement it has laid, Mr. Doty said.
Encouraged by the success rate in these states, neighboring states are taking steps to incorporate rubberized asphalt in their highway planning.
The Texas Department of Transportation, for example, recently completed laying asphalt rubber on an 18.6-mile stretch of U.S. 385 in its Odessa district. Four years earlier, the district sprayed a badly deteriorated, 17-mile length of Interstate 20 with asphalt rubber binder.
After four years, the asphalt rubber on Interstate 20 has performed much better than conventional asphalt would have during the same period, said Stephen Smith, the district's construction director.
In August 1998, the Tennessee Department of Transportation completed two asphalt rubber installations—one on seven miles of U.S. 70 in Dickson County, near Nashville, and one on four miles of Route 1 in Shelby County, near Memphis.
Tennessee began the projects after a year's consultation with the Arizona transportation department and RPA, according to Gary Head, assistant director of operations for the Tennessee Department of Transportation.
New Mexico also is experimenting with asphalt rubber, according to Jim Stokes of the Materials Testing Laboratory of the New Mexico Department of Transportation.
The state's counties and municipalities have considerable discretion in planning their own highway projects, so the main impetus toward asphalt rubber occurs on the local level. Recently there were two asphalt rubber projects in Las Cruces, and one each in Ruidoso and San Juan City.