Chloride profiles along the concrete-steel interface

Artikel i vetenskaplig tidskrift, 2013

The composition and microstructure of the concrete-steel interface influences the critical chloride content for initiation of pitting corrosion and these characteristics may differ from those of the bulk concrete. This paper describes the development of a methodology for chloride profiling along the interface by means of LA-ICP-MS. For semi-quantitative analysis, microstructure characterisation of the pitting positions and distribution and composition of the corrosion products, SEM-EDS and XRD techniques were employed. The results indicate that along the interface a range of chloride levels can be expected. These varied between 0.15–1.5 wt% of concrete with higher levels around the active corrosion sites. Good agreement has been found between the results from LA-ICP-MS and EDS techniques. Interface defects strongly influenced the pitting corrosion. Several Fe(III) oxy-hydroxides accumulated at the aggregate-paste interface and in air voids at the cement paste. XRD analysis suggested the presence of akaganeite and FeCl2 (rokuhnite).