This research examined correlations among the responses of five portable aggregate and soil testing devices, including the nuclear density gauge (NDG), dynamic cone penetrometer (DCP), heavy Clegg impact soil tester (CIST), soil stiffness gauge (SSG), and portable falling-weight deflectometer (PFWD). Readings were analyzed from 41 project sites on treated and untreated base, subbase, and subgrade layers representing 15 different material types in Iowa, Louisiana, Utah, and Wyoming. Analyses of the data revealed statistically significant correlations for all six of the possible two-way comparisons involving the DCP, CIST, SSG, and PFWD, and a nomograph was developed for correlating responses among these different devices. No statistically significant correlations between data from the NDG and that of any other instrument were identified, however. The correlations developed in this research will be useful to pavement engineers needing to compare different types of strength and/or stiffness measurements for quality control/quality assurance purposes. Additionally, repeatability with respect to operator effects was additionally investigated for the CIST and SSG at 27 sites on treated and untreated base layers in Utah. Analyses of these data indicated that the CIST data exhibited a significant operator effect at 7.4 percent of the test sites, whereas no operator effects were detected at any test site for the SSG data. Thus, the SSG data appear to be less susceptible to operator effects than the CIST data.



College and Department

Ira A. Fulton College of Engineering and Technology; Civil and Environmental Engineering



Date Submitted


Document Type





NDG, DCP, CIST, SSG, PFWD, repeatability