EVALUATION OF NON-NUCLEAR DENSITY GAUGES

Abstract

The objective of this study was to compare a non-nuclear density gauge with a nuclear density gage for quality control on hot mix asphalt paving projects. The nuclear density gauge was a Troxler, Model 4640-D, thin-layer nuclear density gauge (TMTL). The other gauge was the PQI Model 300 non-nuclear density gauge manufactured by Transtech Systems, Inc. Two non-nuclear density gauges, one operated by the contractor (HHR PQI) and the other operated by the research team (KTC PQI), were tested. Findings were as follows: (1) The standard deviations of the density readings of all the gauges were greater than the standard deviation of the overall density of the cores, indicating more scatter in the data from the gauges than in the core data. (2) There was no significant difference between the mean density of the HHR PQI and the mean density of the cores. However, there was a statistically significant difference between the mean density of the TMTL and KTC PQI and the cores. (3) The density distribution of the HHR PQI gauge most closely matched the distribution of the cores with an 88% overlap in the distributions. The overlap for the TMTL was 83% and for the KTC PQI was 78%. (4) If pay factors were determined from gauge densities, then using the densities provided by the TMTL gauge would have resulted in a 5% reduction in overall pay for lane densities. Using the two non-nuclear density gauges would have resulted in 100% overall pay.