Efficiency of electrochemical realkalisation treatment on reinforced blended concrete using FTIR and TGA

Abstract

The present study evaluates the efficiency of the application of electrochemical realkalisation (ER) as a prevent technique for partially carbonated blended reinforced concrete using two pozzolanic additions, metakaolin (MK) and silica fume (SF), replacing 10% cement. In this study, the concrete was exposed to controlled climate conditions (1% CO2, 65% RH, 25 °C) until 65% carbonation was reached (without initial pre-corrosion). Subsequently, ER was applied for a period of 7, 15 and 21 days for the concrete specimens without additions (OPC, reference material); in the case of blended concretes, a single period of 15 days was carried out. In all cases, sodium carbonate (Na2CO3) as an electrolyte and a current density of 1 A/m2 were used. The influence of the additions on the efficiency of ER was studied by the pH evaluation method, using an alcoholic solution of phenolphthalein at 1% as an indicator, and the test was performed before and after the ER process. As a complementary test, FTIR and TGA were used. Linear polarization resistance (LPR) and half-cell potential (Ecorr) were used to monitor the progress of the corrosive process. The results verified that this method increased the pH of the cement matrix; however, ER was more effective for OPC concretes compared to blended concretes. After the ER treatment, the corrosion levels tended to decrease over time; however, the values did not reach the initial pre-corrosion state before the application of ER.