Resetting dense graded airport asphalt production and construction tolerances

Abstract

All elements of pavement material supply and construction are variable in nature and some specifications recognize this variability via statistically based specification limits and pay rates that are related to the percentage of complying quality assurance test results. It was perceived that the traditional and prescriptive airport asphalt specification in Australia included some tolerances that were unreasonably tight and this was preliminarily addressed in conjunction with the development of a more performance-based specification in 2017. However, the reasonableness of the current tolerances required verification based on data generated by actual airport pavement resurfacing works. The quality testing results from three well-constructed and adequately performing recent runway resurfacing projects were statistically analyzed to review, verify and where necessary reset, the tolerances relating to raw material manufacture, asphalt production and surface layer construction. The majority of the current tolerances were appropriate. However, the tolerances associated with the Marshall Stability and Marshall Flow, as well as some compacted field air void limits were recommended to be tightened. It was also recommended that the tolerances for surface cross fall deviation from design be widened and that new tolerances be added for asphalt maximum density and Marshall bulk density. The recommended tolerances aim to allow an average compliance failure rate of approximately 5%, which is consistent with other statistical approaches to infrastructure material specification in Australia.