Influence of cementitious binder on chloride removal under electrochemical treatment in concrete

Abstract

The present study concerns electrochemical treatment to extract chloride ions and to repassivate the corroded steel in chloride-contaminated concrete. As binder, ordinary Portland cement (OPC), ground granulated blast furnace slag (GGBS) and pulverised fuel ash (PFA) were used to produce different concrete mixes: OPC, GGBS and ternary mix containing the three binders, respectively. After 56days of curing, a DC was supplied to the concrete specimens, ranging 250, 500 and 750mA/m2 for 4weeks. Then, the corrosion rate was measured by the anodic polarisation. In fact, an increase in the current density applied to the specimens resulted in a decrease in the corrosion rate, imposing a reduction of the corrosiveness of steel in concrete. For a change in the chloride profile, a removal of chlorides at the depth of the steel was more significant in GGBS and ternary mixes, presumably due to a release of adsorbed chlorides on the hydration surface into free, which was further removed under electric charge. However, all chlorides could not be removed by the immobility of chlorides chemically bound into chloroaluminate and chloroferrite hydrates; a mostly half of chlorides in cast were, in fact, present even after the treatment.