Chloride migration and porosity change due to electrochemical chloride extraction in reinforced concrete

Electrochemical Chloride Extraction (ECE) is a method implemented on chloride-contaminated reinforced concrete. In this paper, the influence of some factors, such as current density, electrolytes and water to cement ratio, on the efficiency of chloride extraction, chloride migration and porosity change in concrete was studied. The results show that after ECE process the Cl- distributes in concrete with a concentration gradient, gradually becoming larger towards the outer part of concrete, but Cl- concentration at all the tested points is less than 0.07% by mass of concrete. Through the method of Mercury Intrusion Porosimetry (MIP) it was observed that after ECE process the porosity of cement mortar adjacent to steel bar was increased, while average pore size was reduced. The change in porosity of outer layer of concrete was varied with the type of electrolytes used. When distilled water is used as electrolyte an increase in porosity occurs, and when saturated aqueous Ca(OH)(2) solution or saturated Ca(OH)(2) + 0.001mol/L Li2B4O7 solution is used an decrement in porosity takes place.