Comparison of Nuclear and Nonnuclear Pavement Density Testing Devices

Abstract

The density of a hot-mix asphalt (HMA) pavement is an important factor for assessing pavement quality. Sufficient density is an essential characteristic of a well-constructed pavement and will lower its potential for distress. Traditionally, pavement density is determined by laboratory measurements of core samples and in situ readings via nuclear density gauges. Recently, nonnuclear devices that measure the electromagnetic properties of pavements have been developed. Nonnuclear devices have an inherent advantage over nuclear density gauges in that stringent monitoring of the user and extra security precautions are not required. However, the literature is unclear whether the readings from these devices are equivalent to those from nuclear density gauges. In this study, in-place pavement density readings from nonnuclear and nuclear density gauges were compared with laboratory-measured density values from core samples taken from the same location. Density readings from both gauges were compared with density measurements from the core samples for percent difference, correlation analysis, and hypothesis testing. However, the effect of moisture in the HMA was found to have a significant impact on density readings from the nonnuclear gauge. For seven of eight projects when a regression-based correction incorporating the qualitative moisture index was applied to the nonnuclear gauge density readings, the densities were better correlated to core density measurements than were densities from a traditionally used nuclear density gauge. On the basis of this study, the nonnuclear density gauge is more suitable than the nuclear density gauge for measuring pavement density on dense-graded HMA, provided that the readings are corrected using the qualitative moisture index.