CHLORIDE CONTENTS AT THE CONCRETE-STEEL INTERFACE

The composition and microstructure of the concrete-steel interface influences the critical chloride content (Ccr) for initiation of pitting corrosion and can differ from the conditions in the bulk concrete. This paper describes the development of a methodology for chloride profiling along the interface by means of LA-ICP-MS. SEM-EDS and XRD techniques were used for semi-quantitative analysis of Ccr, microstructure characterization of the pitting positions and distribution and composition of the corrosion products. A range of chloride levels along the interface was measured by means of LA-ICP-MS showing good agreement with the results from EDS analysis. A number of interface defects were found to influence pitting corrosion. Several Fe(III) oxy-hydroxides, including akaganeite, were identified. XRD analysis suggested the existence of FeCl2. These corrosion products tended to accumulate at the aggregate-paste interface and in air voids at the cement paste