Electrochemical Realkalisation of Carbonated Concrete: an Alternative Approach to Prevention of Reinforcing Steel Corrosion

Abstract

This paper studies electrochemical realkalisation (ER) as a method of preventing steel reinforcement corrosion induced by carbonation. Prismatic specimens of reinforced concrete were made with two types of cement, Portland Compound Cement (CPC) and Portland Pozzolanic Cement (CPP). The specimens were exposed to an atmosphere with 10% CO2 at 30°C and 65% RH until a partially carbonated concrete was obtained. Then ER was administered for 20 days using 1 A/m2 of steel and 1M of Na2CO3 or K2CO3 solutions as anolytes. During the ER, the pH of the anolyte was measured regularly. In the concrete, besides the application of phenolphthalein, pH was determined at the steel interface and the specimen surface by potentiometric titration in powders. After the treatment, the pH obtained in the specimens made with CPC was higher than that in the CPP, both at the steel interface and at the surface. The type of cement was a variable that affected the pH level reached but the type of anolyte used was not. In the area near the concrete surface, the largest increase in alkalinity was obtained after 5 days of realkalisation, although it should be mentioned that the initial pH considered for a non-carbonated concrete was not reached.