This research was initiated from a need to evaluate marginal mixtures that do not meet the Superpave mix design criteria for the air voids content requirements for the construction of hot mix asphalt pavements. The developed criteria is comprised of the base criteria derived from test data of as-placed field cores normalized to 7.5% air voids content, which provides the minimum stiffness and strength requirements for a mixture as a function of the traffic level. The stiffness of pavement cores is measured using Simple Shear Tester to obtain shear stiffness |G*| of mix and strength is measured using indirect tensile strength testing. The asphalt mixture will meet the criteria if it meets both the stiffness and strength requirements. Additionally, the criteria include coefficients intended to adjust the base criteria for variable mix density. Given the need to assess the mix performance in the plant mixing stage, an adjustment factor is provided to account for the compaction procedure effects for the gyratory-compacted asphalt plant mixtures relative to pavement cores compacted by rollers. Another adjustment factor to account for the mixture aging effects is provided for the asphalt mixtures tested in the mix design stage. Forensic study of failed interstate pavement near Indianapolis, Indiana suggests that for a heavy traffic of more than 30 million design equivalent single axle load applications, the factor of safety that the developed criteria is providing against rutting is ranging from 2.2 to 2.8.

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stiffness, strength, performance criteria, specfication, SPR-2644

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Performing Organization

Joint Transportation Research Program

Publisher Place

West Lafayette, IN

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