Distribution of chloride and alkaline ions in concrete under external electric field

Abstract

Electrochemical chloride extraction (ECE) treatment was applied to cylindrical concrete specimens containing 3 wt% NaCl of cement with saturated Ca(OH) 2 solution as the electrolyte solution, and distribution of chloride, potassium and sodium ions in concrete specimens were studied after 28 days' ECE treatment with three different current densities (1.0, 2.0 and 3.0 A/m2). The results show that less residual chloride ions remain in concrete when the distance to reinforced steel is shorter in the ECE treated specimen and the applied current density is higher. On the other hand, a great quantity of potassium and sodium ions migrate and accumulate into the steel surrounding area. The amount of sodium ions in the inner layer concrete reaches 4.8 to 17.3 times of those in the external layer concrete and the amount of potassium ions in the inner layer concrete becomes 3.8 to 17.5 times of those in the external layer concrete after the ECE treatment. The risk of alkali-aggregate reaction attack is consequently increased in the inner concrete, and a small quantity of cement hydration products become decomposed.