Title: Chloride profiles along the concrete-steel interface

Authors: Nelson Silva; Luping Tang; Jan Erik Lindqvist; Dimitrios Boubitsas

Addresses: Department of Civil and Environmental Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden. ' Department of Civil and Environmental Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden. ' CBI Swedish Cement and Concrete Research Institute, Box 857, SE-501 15 Borås, Sweden. ' CBI Swedish Cement and Concrete Research Institute, Box 857, SE-501 15 Borås, Sweden

Abstract: 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).

Keywords: concrete-steel interface; LA-ICP-MS; SEM-EDS; chloride threshold values; pitting corrosion; microstructure; steel; chloride profiling; aggregate-paste interface; air voids; cement paste; akaganeite; rokuhnite; concrete structures; critical chloride content.

DOI: 10.1504/IJSTRUCTE.2013.050767

International Journal of Structural Engineering, 2013 Vol.4 No.1/2, pp.100 - 112

Published online: 28 Jun 2014 *

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