An experimental study that evaluated the feasibility of applying s twin-probe gamma-ray gauge for density measurements of cylindrical bituminous specimens is described. Major considerations related to the operational features of the gauge and the characteristics of the composite structure of bituminous mixtures are highlighted. Three bituminous mix types - namely, sand asphalt, dense-graded mix, and open-graded mix - were included. The measurement precision and accuracy characteristics of the gauge with respect to the different mix types were examined. It was found that the precision and accuracy of gauge-determined densities varied with the types of mix tested. Better precision and accuracy were achieved with specimens that had more uniform density distribution within the mass and with specimens that were less porous. Recommendations concerning the use of gamma-ray probes for laboratory density measurements of bituminous paving mixtures are made. An illustration showing the ability of the twin-probe gauge to determine the density profile of a tall specimen is presented. (Author/publisher)
Abstract