Applicability of electrochemical chloride extraction to concrete made with different binders

Abstract

The present study concerns the application of electrochemical chloride extraction to concrete designed with partial replacements from different binders, namely ground granulated blast furnace (GGBS), pulverized fly ash (PFA) and Silica Fume (SF), aiming to attend the need of corrosion repair for structures made in the more recent years. Concrete specimens were used to assess characteristics such as compressive strength and resistance to chloride penetration on different binders. Meanwhile, mortar samples were used for ECE treatment and chloride profiling. Additionally, microscopic examination was performed to quantitatively confirm the formation of C–S–H gel in the cement matrix, which is subsequently indicative of which type of chloride binding is more expected. ECE was applied to the specimens at a current density of 2A/m2 for 4 weeks. In fact, the chloride binding mechanisms were found to have important implications on the different performance perceived for all binders. For a change in the chloride profile, the removal of bound chlorides at the depth of the steel was more significant in GGBS, due to a possible release of adsorbed chlorides from the silicate hydrates, at bigger intensities for that material. However, even though GGBS had greater rates of bound chloride removal it had still the same percentage as OPC for total efficiency due to the fact that in OPC the removal of free chlorides is then more expressive.