An Alternative Method of Obtaining the Particle Size Distribution of Soils by Electrical Conductivity

This study proposes a new method to determine the particle size distribution (PSD) of soils by considering the electrical conductivity (EC) technique. A new EC probe was designed with a transparent thermoplastic, commonly known as acrylic, and brass electrodes. At first, the EC of a soil-water homogeneous suspension was calculated at different densities to obtain a calibration curve of each tested soil sample. During the PSD analysis, as the particles started to settle down in the basement due to gravity, the EC was measured at different time intervals, and the corresponding EC values were then matched with the calibrated EC values at different densities. The proposed method considered the conventional Stokes' law to determine the diameter of soil particles and the general percentage of passing mathematical expression to obtain the final PSD curve of each soil. The PSD analysis by the EC approach was later validated with that of hydrometer and laser diffraction methods, and in general, good agreements were obtained for identical soil samples at different classifications of soil particles such as clay, silt, and sand. Finally, reproducibility tests were also conducted and the new EC probe overperformed the hydrometer method in terms of both accuracy and precision. The finding from this study aimed to propose an alternative to determine the PSD of soils by using the EC technique with a high level of accuracy and efficiency.