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Publication Number: FHWA-SA-97-024
Date: June 1997
As the Superpave mix design system takes hold across the country, highway agencies, contractors, and others are asking questions about the system. Here are answers to some of the most frequently asked questions.
Q. Do Superpave mixes cost more than conventional mixes?
A. Not necessarily. But because the Superpave system takes environmental conditions into account, you might end up specifying a higher quality binder than what you typically use. And that higher quality binder might cost a bit more until suppliers routinely stock it. Some States have found, however, that switching to the Superpave system has resulted in lower mix prices, because the performance-based specifications broaden the market and increase competition.
Q. Are the Superpave volumetric mix design procedures intended for new construction only?
A. No. The procedures apply for rehabilitation projects and overlays, as well as for new pavements.
Q. My company is about to bid on our first Superpave job. Will we need any special paving equipment to construct a Superpave pavement?
A. No-Superpave pavements are built using the same pavers, rollers, and other equipment used for conventional hot-mix asphalt pavements.
Q. Is it true that Superpave mixes are difficult to compact?
A. Like some other mixes with a high proportion of coarse stone, Superpave mixes can be more difficult to compact than conventional mixes. However, contractors experienced in using Superpave mixes say it's easy to solve this problem-just start the compaction process earlier than normal and have the rollers follow close behind the paver.
Q. A recent request for proposals stated the mix "must conform to the Superpave specifications." Where can I get a copy of those specifications?
A. Contact the American Association of State Highway and Transportation Officials (AASHTO) at 202-624-5800 (fax: 202-624-5806) or toll-free at 800-231-3475 (fax: 800-525-5562). You'll need the 1996 AASHTO Provisional Standards (Publication Code PS-96), as well as the updated supplement (Publication Code PS-97).
Q. My boss needs a short, straightforward introduction to the Superpave system. Any suggestions?
A. A good starting point would be the brochure, The Superpave System: New Tools for Designing and Building More Durable Asphalt Pavements (Publication No. FHWA-SA-96-010). It's available from FHWA's Research and Technology Report Center (phone: 301-577-0906; fax: 301-577-1421), or call one of the five Superpave regional centers.
Do you have a question about the Superpave system? Drop us a line, and we'll track down the answer (fax: 202-347-6938 ).
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