Bridge Expansion Joint for Bridges with Expansion Joints in Deck Slabs on Electro-Osmosis

Electro-osmosis is a ground improvement technique that accelerates the consolidation of soft, fine-grained soils by applying an electric current to the soil. The electric current causes water to flow from the anode to the cathode, dewatering the soil and increasing its strength. Electro-osmosis near existing expansion joints requires careful planning to minimize the effects on the joints. Electro-osmosis process involves installing electrodes (anodes and cathodes) in the soft soil and applying a direct current (DC) voltage between them. The electric current causes water to flow from the anode to the cathode through the soil pores. The water is collected at the cathode and pumped away, dewatering the soil and causing it to consolidate. Ground settlement from electro-osmosis occurs as the soil dewatering causes consolidation. The settlement depends on the initial water content of the soil and the degree of dewatering achieved. Settlement monitoring is recommended during electro-osmosis near existing joints. Electrochemical reactions at the electrodes can cause corrosion of the anode and changes in the soil chemistry near the electrodes. The soil near the anode becomes acidic, while the soil near the cathode becomes alkaline. These chemical changes can affect the properties of the soil and the performance of adjacent expansion joints. Post-treatment inspection of existing expansion joints must verify that the electro-osmosis has not caused any damage. The inspection should check the joint gap width, the concrete edge beam condition, and the anchor bolt torque. Any damage must be repaired before the bridge is returned to service. Electro-osmosis effectiveness is verified by comparing the soil properties before and after treatment. Vane shear tests and water content measurements are performed before and after treatment to measure the improvement in soil strength and the reduction in water content. The test results are compared with the design requirements to verify that the treatment has achieved the required improvement.