Characterization and Modeling of Photon Absorption for Improved Accuracy and Consistency of Density Measurement Using Nuclear Gauge with Hydrogen Effects

Abstract

The nuclear gauge test method, as a non-destructive method, has been used for highway construction and compaction control since the 1950s. This method is based on the attenuation of photons passing through materials to be tested. Because the hydrogen atom has a different ratio of electron/atom mass from other atoms, the content of hydrogen atoms in the bulk material may produce significant effects on nuclear density measurement results. Therefore, to accurately predict material density from the photon count number, the relative composition related to hydrogen needs to be corrected or decoupled. Moreover, the accuracy of nuclear testing significantly depends on the calibration equation which correlates the material density with the nuclear gauge count reading. The choice of a calibration equation not only changes with engineering conditions and requirements, but also depends on the physical principles of measurements. In this study, the photon absorptions of mixed composites with different densities and moisture contents were investigated using photon and neutron nuclear sources. The count readings changing with material density and moisture content were analyzed. Using the photon count number versus actual density at different hydrogen contents, the effects of hydrogen atoms and actual density on the photon count number were decoupled. The decoupled model provides a satisfactory assessment for all the test samples with different moistures and foam particle volume fractions.