U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
|Accelerating Infrastructure Innovations|
Publication Number: FHWA-SA-97-024
Date: June 1997
When governments in developing countries or in countries where the economy is in transition want to improve their transportation systems, they turn to the World Bank for financial and technical assistance. To better prepare its staff to respond to the growing number of inquiries about the Superpave system, the World Bank recently held an in-house seminar.
"There has been a lot of talk and discussion in our client countries about adopting the Superpave system," says Cesar Queiroz, a senior highway engineer at the World Bank, whose principal client is the Russian Federation. "I was involved in SHRP for years and so am familiar with the SHRP results, but some of my colleagues are not that familiar with the SHRP products. This was an opportunity for them to get acquainted with the Superpave system, so we can answer our clients' questions and help them with this new technology."
Seventeen World Bank transportation engineers and economists, representing countries around the world, attended the seminar. This was the third time in the past decade that the World Bank had arranged for a special staff seminar on SHRP products.
The seminar, organized by the Transportation Research Board (TRB), included a series of brief presentations, starting with an overview on the history and development of the Superpave system, presented by TRB's Neil Hawks.
Byron Lord, from the Federal Highway Administration, followed with highlights of the national program to implement the Superpave system. Haleem Tahir, from the American Association of State Highway and Transportation Officials, covered the standards and equipment used in the Superpave mix design procedures. Ed Harrigan, also from TRB, described a number of ongoing research projects to refine the Superpave system. Larry Michael, from the Maryland Department of Transportation, reported on his State's experience with designing and building Superpave pavements.
Paving contractors in Maryland are pleased with Superpave mixes, said Michael. "They like the Superpave gyratory compactor for mix design, as it does a better job of mimicking real-world conditions. And although large-stone mixes, such as Superpave, are somewhat harder to compact during construction, our contractors have learned how to deal with this-it's an issue of quality control."
In his presentation, Tahir pointed out that a highway agency wanting to use the Superpave system must have access to a well-equipped asphalt laboratory, including ovens, gradation systems, vacuum and air lines, temperature controls, and a dust-free environment.
"The provisional standards are also essential," said Tahir. "And you must have a trained engineer on board to get the program up and running."
A question-and-answer session followed the presentations. Many of the questions were familiar to the panel, as they echoed concerns raised by highway agencies in the United States. Other questions were not so familiar-for example, whether the low-temperature binder tests are applicable for tropical environments. Harrigan replied that the binder specification can be adapted for those climates, as was recently done for an airport paving project in Malaysia.
The issue of cost also came up. "According to asphalt refiners here in the United States, Superpave binders will not cost more to manufacture," said Lord. "But when we ask for better-performing asphalts, this might mean higher costs."
Some of the World Bank staff expressed concern that their client countries might not have sufficient information on traffic volumes and loads at a project site; this information is a key factor in the Superpave mix design process. In responding, Michael said that this is not an uncommon problem, but "regardless of the information available for input, the Superpave system is significantly better than any other mix design system."