Corrosion rate of rebars from linear polarization resistance and destructive analysis in blended cement concrete after chloride loading
conference paper
Concrete specimens with various binders including Portland cement, fly ash, blast furnace
slag and composite cement and three water-to-cement ratios were subjected to cyclic wetting
with salt solution and drying. Specimens contained six mild steel bars at two cover depths and
two activated titanium reference electrodes. After salt loading for half a year, they were
exposed for two years in various climates (20°C 80%RH, outside, fog room). Steel potentials,
corrosion rates (using LPR) and concrete resistivities were measured. At the end of the
exposure period the actual corrosion loss was assessed from visual examination after taking
out steel bars and the chloride distribution was measured.
The results show a large influence of the cement type on resistivity and on corrosion rates.
Concrete resistivities showed an increase with time in all mixes, with significant differences
between Portland and blended cements and for different climates. Steel potentials do not
discriminate well between negligible and significant corrosion. Corrosion loss from linear
polarisation resistance and destructive analysis showed good agreement. Redistribution of
chloride inside specimens is affected strongly by the wetness of the environment. The critical
chloride content for Portland cement could be resolved from corrosion rate data at 0.5% of
chloride ion by mass of cement
slag and composite cement and three water-to-cement ratios were subjected to cyclic wetting
with salt solution and drying. Specimens contained six mild steel bars at two cover depths and
two activated titanium reference electrodes. After salt loading for half a year, they were
exposed for two years in various climates (20°C 80%RH, outside, fog room). Steel potentials,
corrosion rates (using LPR) and concrete resistivities were measured. At the end of the
exposure period the actual corrosion loss was assessed from visual examination after taking
out steel bars and the chloride distribution was measured.
The results show a large influence of the cement type on resistivity and on corrosion rates.
Concrete resistivities showed an increase with time in all mixes, with significant differences
between Portland and blended cements and for different climates. Steel potentials do not
discriminate well between negligible and significant corrosion. Corrosion loss from linear
polarisation resistance and destructive analysis showed good agreement. Redistribution of
chloride inside specimens is affected strongly by the wetness of the environment. The critical
chloride content for Portland cement could be resolved from corrosion rate data at 0.5% of
chloride ion by mass of cement
TNO Identifier
330430
Source title
15th International Corrosion Congress (ICC), Granada, Spain 2-27 September
Pages
1-8
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