United States Department of Transportation
i
Field correlation of PQI gauge with nuclear density gauge: phase 1.
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2006-12-01
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[PDF-1.93 MB]
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Abstract:Traditionally, the Oklahoma Department of Transportation (ODOT) uses a nuclear density gauge as a quality control (QC) and quality assurance (QA) tool for in-place density. The nuclear-based devices, however, tend to have problems associated with licensing, equipment handling, and storage. The Pavement Quality Indicator (PQI), manufactured by TransTech Systems, Inc., is a non-nuclear device that determines the density of an asphalt pavement layer based on the principle of electrical impedance and the dielectric constants of associated materials. To this end, field data was generated from six field projects for calibration of a PQI 301 gauge. The performance of the PQI gauge was compared with a nuclear density gauge in four field projects and was validated against laboratory densities (AASHTO T 166) measured from selected cores extracted from the pavements. It was observed that 5-point data instead of 13-point data can be used for PQI density with 95% certainty in all the cases. It is recommended from this study that PQI 301 be used before the pneumatic roller than after the finish roller. A PQI gauge calibrated with 5 cores exhibits similar performances as the PQI gauge calibrated with 10 cores. Further study is required for validation of this conclusion. It was noticeable that PQI 301 produced better coefficient of determination than the nuclear gauge if the PQI gauge is used before the pneumatic roller. Finally, mean squared error as well as R-squared value should be used for calibration purposes.
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