The Effects of Electro-Chemical Chloride Extraction on the Migration of Ions and the Corrosion State of Embedded Steel in Reinforced Concrete

Abstract

The effects of electrochemical chloride extraction were evaluated using different electrolytes and binders on cylindrical concrete specimens with a water/binder ratio of 0.4. Two-percent NaCl by weight of binder was added to the water as a chloride source during concrete casting. After the specimens were immersed in water for three months, direct current 0.5 A/m2 was applied to release approximately 30% initial chloride. The use of intermittent mode during extraction process was more efficient in releasing chloride than a continuous mode. After treatment, although the average remaining-chloride content was higher than threshold value, its content at the interface was only approximately 0.4%. The accumulation of alkaline ions around the embedded steel was noticeable but the distribution of calcium ions showed as different tendency. The migration of ions from the electrolyte was insignificant. This demonstrated the important role of internal ions in transferring the charge during extraction; simultaneously, the decomposition or transformation of hydrated products is inevitable. After the treatment was stopped for four weeks, the half-cell potential of the steel reached to low-corrosion state.