AASHTO TP 112-19 (2020)

AASHTO TP 112-19 (2020) describes the procedures for determining the density and moisture content of soil and soil-aggregate using a Complex Impedance Measuring Instrument (CIMI). This practice describes three different electrode configurations to determine the density and moisture content. One tool utilizes soil penetrating probes and two additional tools are nonpenetrating surface electrodes. The CIMI measures the electrical properties of the soil being tested and correlates the electrical properties to the physical properties during a soil calibration procedure. The soil electrical properties are typically unique for the soil material. During the soil calibration procedure a set of algorithms relates the electrical and physical properties of the soil using linear regressions. The subsequent electrical testing of the soil utilizes the established relationship of the electrical and physical characteristics to calculate the soil density and moisture content.