Abstract
As they adopt mechanistic-empirical (ME) methods for flexible pavement design, road agencies are starting to incorporate performance-related specifications (PRS) for hot mix asphalt materials to assure that the as-built materials meet the performance requirements assumed in the pavement structural design. PRS pose new challenges for materials producers and contractors who have never had to relate volumetric mix design parameters to performance requirements such as fatigue life and rutting resistance. The objective of this paper is to describe the development of guidance for materials producers and contractors to support their decision making with regard to changes to mix designs to meet PRS requirements. The guidance was first developed based on known experience. To validate the guidance and demonstrate its usage, a production mix meeting Superpave volumetric requirements for California state highways was selected as the starting point for a set of adjustments applied to the mix. The effects of each adjustment were evaluated by conducting laboratory tests to determine mechanistic performance parameters used in structural design. The mechanistic performance parameters evaluated in this study include stiffness, fatigue resistance, and rutting resistance. The initial experience-based mix design guidance was found to be generally consistent with the laboratory test results for the example mix, albeit with some minor exceptions. The mix design guidance was then revised based on findings from this study. It is recommended that the revised guidance be used as non-mandatory advisory information for projects with PRS and that it be further improved with more results.
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