Towards correlating natural and accelerated chloride-induced corrosion in cracked RC - Preliminary results

This paper presents preliminary results of an on-going study on chloride-induced corrosion in reinforced concrete. A total of 210 beam specimens (120 × 130 × 375 mm) were made using two w/b ratios (0.40 and 0.55), three binders (PC, PC/FA and PC/GGBS) and two concrete covers c (20 and 40 mm). Other experimental variables included crack width w _cr (0, 0.4 and 0.7 mm) and exposure environments (field and laboratory). Accelerated corrosion by cyclic wetting and drying with 5% NaCl solution was used for the laboratory-based specimens while the field-based specimens were exposed to a natural tidal/splash marine zone. Corrosion rate (i _corr), half-cell potential and concrete resistivity were measured every two weeks over a period of 30 weeks. Results obtained so far underscore the influence of w _cr, c, resistivity and concrete quality on i _corr, with the general trend showing i _corr increasing with increasing w _cr and decreasing c, resistivity and concrete quality. The results show that for a given set of experimental variables, both natural and accelerated cumulative mass loss follow a linear trend but with the latter having a higher slope. However, long-term results are required to confirm this linear trend with time. The ratios between the natural and accelerated i _corr show high variability. This variability should be taken into account when correlating the two.