Field evaluations of nuclear and non-nuclear gauges as alternates to destructive coring for airport asphalt density testing

Abstract

The compaction of airport asphalt is critical for the good performance of airport pavement surfaces. Traditionally, airport asphalt compaction was assessed using destructive cores recovered from the surface during each work period, resulting in 200-500 cores being taken along the length of a typical runway, each creating a weak point in the surface. In recent times, non-destructive testing of asphalt density has come to the interest of practitioners and researchers alike, including nuclear and non-nuclear gauges for density testing. The benefits include faster testing, which otherwise allows more locations to be tested, and the avoidance of introduced weak points in the surface, which allow moisture ingress over the life of the surface. However, physical testing of recovered cores is the gold standard of asphalt density testing and some practitioners and researchers question the reliability of gauge-based estimates of air voids and relative density. To evaluate the efficacy of common non-destructive density gauges, field evaluations of both nuclear and non-nuclear devices have been performed, in parallel with destructive coring, during six airport resurfacing projects. This research compares the destructive core test results to the gauge-based results, both on the joints between paving runs and in between the paving joints. It was concluded that following a mixture-specific calibration, the gauges were just as effective at measuring asphalt density as destructive coring. It was also found that the nuclear gauge was prone to occasional low density estimates of the joints, and when coupled with the simpler logistical restrictions associated with non-nuclear gauges, the non-nuclear gauge was concluded to be preferred.