Moisture migration and electric distribution of unsaturated clay under electro-osmosis with carbon fiber tape as electrode

Electro-osmosis is a promising technique for controlling the moisture content of a subgrade. The moisture content increases when subjected to groundwater, rainfall, winter freeze, and spring thaw, decreasing the modulus and pavement life. In this study, laboratory experiments were conducted to investigate the effect of electro-osmosis on moisture control of compacted subgrade. A special apparatus was constructed to perform one-dimensional electro-osmosis experiments based on two types of electrode materials, three levels of supply voltages, and three types of dry densities. The feasibility of electro-osmosis on moisture control of subgrade and other influential factors was investigated. The experimental results show that electro-osmosis reduced the moisture content of compacted subgrade clay by 9.7–15.6%, ensuring that the saturation degree of subgrade was close to the optimum value. The moisture migration rate in unsaturated soil decreased significantly during electro-osmosis, and the relationship between electro-osmotic permeability and moisture content could be described by an exponential function. The two types of electrodes used are copper and carbon fiber tape (CFT). It was observed that the CFT electrode has a better contact performance with soil compared to the copper electrode, exhibits electrochemical corrosion resistance, and provides a voltage loss of 9.3–34.2%. However, an increase in supply voltage doesn't necessarily improve the performance of electro-osmosis because of serious voltage loss at the anode electrode-soil interface; hence, proper voltage is more effective and energy-saving. For future research, the electrode-soil contact can be improved to reduce the wastage of energy.