U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
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Focus
| Accelerating Infrastructure Innovations |
Publication Number: FHWA-SA-96-017
Date: June/July 1996
Two new products from the long-term pavement performance (LTPP) studies contain proposed revisions for selecting Superpave binders. The products are intended for pavement designers and materials engineers, as well as asphalt producers and suppliers.
The first product is a report, LTPP Seasonal Asphalt Concrete Pavement Temperature Models, which discusses a proposed model for determining the low-temperature component of the Superpave performance-graded binders. The report includes a limited comparison between the revised model and existing models.
The second product is an easy-to-use database, which combines data from the LTPP studies' seasonal monitoring program with weather station data from the original Superpave binder specifications. The database will be a useful tool for further refining the low-temperature model.
Superpave binders are selected based on the lowest and highest pavement temperatures expected at the job site. The original Superpave specifications were developed with limited data for validating the low-temperature algorithm for pavement temperatures. The lowest air temperature was thus used for the lowest pavement temperature. In areas with extremely low temperatures, this conservative approach has led to the selection of more restrictive binder grades than may be necessary. These binder grades usually require that modifiers be added to the asphalt, which drives up the cost of the project.
For 2 years now, the seasonal monitoring program of the LTPP studies has been collecting pavement temperatures and air temperatures at 30 test sites throughout North America. This information formed the basis for the revised low-temperature algorithm.
To request a copy of the LTPP Seasonal Asphalt Concrete Pavement Temperature Models or the database (available as ASCII text or in Microsoft Excel format), contact FHWA's Pavement Performance Division (telephone: 703-285-2355; fax: 703-285-2767).
