Experimental study on synergistic effects of electroosmosis and CaCl2 on inhibiting the expansion behaviors of sodium sulfate saline soil

The fundamental cause of frost heave and salt expansion of saline soil is the water condensation and salt crystallization during the freezing process. Therefore, controlling the water and salt content is crucial to inhibit the expansion behaviors of saline soil. Recently, electroosmosis has been demonstrated to accelerate soil dewatering by driving hydrated cations. However, its efficiency in mitigating the salt-induced freezing damages of saline soil requires further improvement. In this study, a series of comparative experiments were conducted to investigate the synergistic effects of electroosmosis and calcium chloride (CaCl 2 ) on inhibiting the deformation of sodium sulfate saline soil. The results demonstrated that electroosmosis combined with CaCl 2 dramatically increased the cumulative drainage volume by improving soil conductivity. Under the external electric field, excess Na + and SO 4 2- ions migrated towards the cathode and anode, respectively, with a portion being removed from the soil via electroosmotic flow. These processes collectively contributed to a significant reduction in the crystallization-induced deformation of saline soil. Additionally, abundant Ca 2+ ions migrated to cathode under the electric force and reacted with OH - ions or soluble silicate to form cementing substances, significantly improving the mechanical strength and freeze-thaw resistance of the soil. Among all electrochemical treatment groups, the soil sample treated with 10% CaCl 2 exhibited optimal performance, with a 71% increase in drainage volume, a 180%~443% enhancement in shear strength, and a 65.1% reduction in freezing deformation. However, excessive addition of CaCl 2 resulted in the degradation of soil strength, microstructure, and freeze-thaw resistance.