Comparisons of Data from a Complex-Impedance Measuring Instrument and Conventional Compaction Control Tests

This paper describes the results from a comprehensive evaluation of a relatively new non-nuclear method for compaction control. The device utilized in this study is a complex-impedance measuring instrument (CIMI), more commonly known by its manufacturer’s trade name: the “Electrical Density Gauge” (EDG). In its current form, the CIMI device uses a series of electrical measurements in conjunction with calibrated soil models to infer in situ soil unit weight and moisture content. Two approaches currently exist for building soil models with a CIMI: the first is the ASTM-approved method of calibration with in situ measurements of unit weight and moisture content provided by the nuclear density gauge (NDG), sand cone, or other similar type of in situ test, and the second is calibration with large “Proctor-type” mold tests in a controlled laboratory environment. In this study, the two calibration methods were evaluated using NDG tests that were conducted in a large rigid box in the field (to simulate field compaction conditions), and large “Proctor-type” mold tests that were conducted in a lab-controlled environment. In order to evaluate the accuracy of both calibration methods, drive cylinder tests and sand cone tests were conducted at the same locations as the CIMI and NDG tests for comparison purposes. The findings from this study are useful for engineers that may be considering the use of CIMI technology for compaction control.