Impact of wetting–drying cycles on the volume change behaviour of electrokinetically treated soils

This study examines the volume-change behaviour of electrokinetically (EK) treated expansive soils subjected to repeated wetting–drying cycles (WDCs), providing insights into their cyclic response under repeated laboratory wetting–drying conditions. The soils were treated with three ionic-solution combinations: CaCl2–DW (DW: distilled water), DW–Na2CO3, and CaCl2–Na2CO3  for 28 days, followed by five WDCs over 20 days. Axial deformation, cyclic swelling reduction (CSwR), cyclic shrinkage reduction (CShR), and swelling pressure were measured after each cycle. Results show that CaCl2–Na2CO3  is the most effective in suppressing volume change, followed by CaCl2–DW and DW–Na2CO3, particularly at anode-to-cathode distances (DA↔C) of 0–6 and 24–30 cm. Volume change was reduced by up to 75% by the fourth cycle, accompanied by decreasing pH and ionic strength, with the response approaching an apparent equilibrium within the five-cycle laboratory programme. Statistical analysis provided significant interactions between ionic-solution types, anode-to-cathode distances (DA↔C), and WDCs. Volume-change suppression was associated with physicochemical changes, including ionic interactions and possible microstructural rearrangement. The findings suggest that EK treatment can reduce swell–shrink behaviour in expansive soils under the tested conditions, with potential for improving their geotechnical performance.