Subject: Final Report, March 3, 2003. Work Order No. 98-32-11 relates to the use of Superpave 4.75mm Nominal Maximum Aggregate Size (NMAS) mixtures. The NMAS mixtures suitability for thin overlay applications such as those less than 40 mm (1 1/2-inch) in depth, workability, and positive appearance, through the minimization of segregation, are the desirable qualities of this HMA mix. Current AASHTO standards and specifications for Superpave do not include Superpave 4.75mm NMAS mixtures. In this study, the Department chooses and analyze three 4.75mm NMAS HMA mixtures that were developed using the Superpave volumetric mix design method and one PENNDOT ID-2 Wearing Course mixture developed using the Marshal mix design method. The three 4.75mm mixtures include a control (dens-graded) mixture; a mixture containing crumb-rubber additive; and a mixture containing crumb-rubber additive in combination with Vestnamer, a proprietary asphalt/crumb rubber modifier manufactured by DeGussa.
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