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UW-Madison professor develops new superpave standards


Hussain U. Bahia

Hussain U. Bahia (large image)

Longstanding asphalt specifications may fall by the wayside in light of a new report by University of Wisconsin-Madison Civil and Environmental Engineering Professor Hussain Bahia. The report highlights several changes to national standards that will result in better-performing asphalt that is more inclusive of new and emerging materials.

The report's main finding is that current American Association of State Highway and Transportation Officials (AASHTO) specifications for performance graded asphalt binders underestimates the potential performance of modified asphalt binders. The resulting report proposes changes to national specifications, including six new standard testing protocols, two new machines (one is under patent application) and a new asphalt grading system to be used nationally.

"For the last five years our group has studied the best methods of evaluating asphalts modified with additives such as plastics, polymers and recycled tires," said Bahia, the project's principal investigator. "We have developed new methods to study storage stability, workability and resistance of asphalt to heavy traffic conditions. The proposed standards include criteria to account for traffic volume, traffic speed and pavement structure in selecting modified asphalts."

The report, which was released early this fall, is of particular interest to materials engineers in state highway agencies as well as to materials suppliers and paving contractors responsible for modifying asphalt binders for hot-mix asphalt pavement construction.

For this project, Bahia worked with the Asphalt Institute, a research center for the Association of Asphalt Producers and the National Center for Asphalt Technology, a research center for the National Asphalt Pavement Association located at Auburn University. The research study and subsequent report was funded by a $1 million grant from the National Cooperative Highway Research Program (NCHRP).

For more information about this report, please contact Bahia at 608/265-4481 or