Abstract
This paper summarizes a case study on developing specification limits and pay adjustments for the longitudinal joint density of asphalt pavements. The existing joint density specifications used by various agencies first were reviewed for the minimum joint density requirements and the corresponding pay adjustments. Laboratory tests were conducted to measure air voids of field cores taken from selected field projects with the saturated surface dry method (AASHTO T 166) and the automatic vacuum-sealing method (AASHTO T 331). Permeability measurements were conducted with a falling-head permeability device. The air voids at the joint were found to be 1.5% to 2% greater than the air voids at the mats adjacent to the joint. For conditions specific to New Jersey, individual testing of the theoretical maximum density of the cores taken at the joint is recommended because of the existence of joint adhesive. The upper limits for air voids at the longitudinal joint are recommended to be 9% for stone matrix asphalt and 10% for hot-mix asphalt, on the basis of the permeability criterion of 150 × 10−5 cm/s reported in previous studies. Furthermore, alternative pay equations for air voids at the longitudinal joint were proposed, with different triggers for retest and for rejectable quality level. A SpecRisk analysis was conducted to confirm that the effective acceptable quality level coincided with the stated acceptable quality level and that the acceptance procedures properly awarded 100% payment at the stated acceptable quality level. The study led to a draft quality assurance specification for longitudinal joint density that was proposed for future implementation.
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