| The Superpave juggernaut is gathering steam, even as technicians
and researchers under Federal Highway Administration contract go back to
the drawing board to revise Superpave mix design computer models.
This "midcourse correction" will delay promulgation of Superpave performance models by a number of years. But at a major application-oriented conference in April, hundreds of Superpave advocates and technicians reaffirmed their support for the Superpave system of performance specifications for asphalt pavements. Nearly 450 registrants participated in Superpave: Today and Tomorrow, a three-day conference held April 21-23 in the shadow of St. Louis' Gateway Arch. And some 25 table-top exhibitors distributed literature, shared technology and provided the newest Superpave testing equipment for technicians to examine. The Superpave system -- an acronym for SUperior PERforming Asphalt PAVEments) -- is one of the major products of the Strategic Highway Research Program (SHRP). Superpave is the new system of performance-related hot mix asphalt (HMA) mix design specifications now being adopted by state departments of transportation throughout the United States. Nearly three-fourths of state DOTs have adopted Superpave binder specs, and over 90 percent have placed trial sections on the way to adoption. The three elements comprising the Superpave system are:
Midcourse correction Even the much-discussed "midcourse correction" in the Superpave mix design computer modeling process didn't seem to faze all the Superpave proponents at the conference, although there was much talk about it. "This has been a major disappoint to me," Mickes said. "I think we are farther behind than where we ought to be." The reason for being of the performance-based specs was to be able to predict how long the pavement would last before going in to a job, he said. Now that day has been pushed to the future. "I think we are almost starting over again," he said. "We're going [have] to fly by the seat of our pants for a few years." The researchers realize they are behind, but don't feel that they are back at Square One. Instead, they are working in a continuous process. FHWA's Superpave models project is being conducted by the University of Maryland and a team of subcontractors. During Phase I of the modeling project, the Maryland researchers reviewed the Superpave pavement performance prediction models and in fall of 1996 found them lacking for their purpose. In the interim the UM researchers uncovered methological problems which will need major technical corrections and field recalibration before the methodology should be made available to users in the field. As a result, the ongoing Phase II of the modeling contract was changed to focus on materials and their characterization. The revised Phase II work, which moved ahead in November of last year, and is scheduled for delivery in December 2000, includes refinement of Superpave design software, development of a simple performance test, continuation of the Superpave Models newsletter, and completion of materials characterization protocols. Matt Witczak is the principal investigator and a professor in civil engineering at the University of Maryland-College Park. You may visit the Superpave models web site at http://www.ence.umd.edu/superpave. Separately, version 2.0 of the Windows-based Superpave volumetric mix
procedures software was to be submitted to FHWA this spring, reviewed by
administration, state DOT and industry experts, and then released to the
American Association of State Highway & Transportation Officials (AASHTO)
for distribution.
Ahead with Superpave Despite Superpave's peculiarities, support remains strong for national implementation of Superpave, the conference showed. "Experts from all segments of the highway community are working together to meet the challenge to produce a new technology that will mean better roads and reduced life cycle costs for all Americans," said Kenneth R. Wykle, Federal Highway Administrator. "Superpave can be successful through this partnership, cooperation and coordination among FHWA, the states and industry." Contractors who want to be successful in coming years must understand Superpave, said industry visionary Don Lucas, chief highway engineer for the Indiana DOT, a Superpave powerhouse. "The quality-conscious contractor who wrestles through the Superpave process is the one who will know how to deal with the contracting process in the year 2000," Lucas said. Superpave is for more than just high-type (interstate) pavements, said
Byron Lord, chief of FHWA's Highway Infrastructure Division. "I see it
being used for interstates, airport runways and local roads," he told the
assembly. "We must all embrace the willingness to promote quality. The
road to tomorrow is based on performances." And that performance will require
longer-lasting, smoother-riding, and better-performing pavements, he added.
Thorns among roses Not all is sanguine with Superpave, the conference revealed. In addition to the modeling revisions, refiners continue to question the practicality of keeping all those different performance grades of binder on hand. "There was some serious doubt at one time as to whether the refiners were going to sign on," Mickes said. But many of these doubts have been resolved by a user/producer group tackling Superpave, he said. Nonetheless, some refiners are balking at the need to store a number of grades of performance-graded asphalt on-site, on-demand, at the refinery, said Gene Chew, president of American International Refinery, Inc., in Houston, and 1998 chairman of The Asphalt Institute. Production of gasoline and of feedstock for plastics carries a much higher priority and profit for refiners, he said, and their accommodation has driven the engineering of refineries for years. In the meantime, low-mark-up asphalt has been of the lowest priority for refiners. "As refiners, we feel we face an increased liability when dealing with
Performance Grade asphalt due to the high variability of the reproducibility
of testing," Chew said. But he said Superpave will be good for the motoring
public and make asphalt more competitive against portland cement concrete.
He added that as marginal asphalt producers leave the market as Superpave
progresses, committed producers will remain, producing a premium asphalt
product.
"The limestone people have a serious problem," Mickes said candidly. "Here in Missouri not everybody who sold us limestone or asphalt in the past is going to be able to provide this type of material. I understand that they may very well not be able to supply it without significant changes in how they do business. But it's a matter of total quality, and where we're headed, and there are some hard business decisions will have to be made by [the stone industry] and the DOTs." With these peculiarities, the net result is a localized tendency to use only those elements of Superpave that seem easy to attain. To help quell this "a-la-carte" attitude, AASHTO, the Associated General Contractors and the American Road & Transportation Builders Association (ARTBA) recently issued a joint statement that said highway agencies and contractors will have to implement all the components of Superpave in order to reap its benefits. "While application of individual components will probably yield performance gains, only uniform application of the entire system will guarantee reliable performance," the associations said. "This revolutionary shift in the way most agencies and contractors construct asphalt pavements requires cooperation in the adoption and implementation of the Superpave system." And at the AASHTO annual meeting in Salt Lake City last November, the AASHTO Standing Committee on Highways weighed in with a resolution titled "Uniform Implementation of SHRP Superpave". The committee urged "all AASHTO members, when implementing SHRP Superpave technology, not to substantially modify applicable prescribed standards, requirements, or methodologies as adopted in the AASHTO [specs]." And those agencies utilizing Superpave elements, but not the entire
system, were warned "to avoid referring to asphalt pavements so constructed
as utilizing the SHRP Superpave technology."
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