Abstract
Most research on chloride-induced corrosion of reinforcing steel is conducted either in simulated pore solution or concrete. The former has the disadvantage that the experiments cannot replicate the environmental variations on the surface of the steel induced by the presence of the cementitious cover. The difficulty with the latter is that it is impossible to clearly assess the impact of many different parameters that influence the corrosion in commercial concrete. Consequently, the present study involves steel plates embedded in cement paste to minimize the number of active corrosion sites relative to steel in pore solution, thus simplifying an investigation into the location and accumulation of corrosion products in the cement paste and the influence of cracks on the corrosion process.
Corrosion monitoring techniques (i.e., open circuit potential mapping, linear polarization resistance) were correlated with chemical and microstructural analyses, including Raman spectroscopy of the corrosion products, to study the specimens. The results indicate the following: a range of corrosion products forms, primarily within shrinkage cracks; their specific volumes are typically in the range of 2 to 3; cracks had a greater impact on the corrosion rate of steel in white cement than in Type 10 cement; and that the surface sealing of the cracks using epoxy did not prevent corrosion initiation from occurring under the epoxy.
Résumé
La plupart des travaux de recherche sur la corrosion provoquée par les chlorures, attaquant l’armature d’acier sont menés soit en solution interstitielle synthétique ou dans le béton. Le problème de l’utilisation de la solution interstitielle vient du fait que les expériences ne peuvent pas reproduire les inhomogénéités présentes à la surface de l’acier, causées par le couvert de béton. Pour le béton, il est impossible d’obtenir une évaluation claire de l’impact des differents paramètres qui influencent la corrosion du béton commercial. C’est pourquoi notre étude utilise des plaques d’acier intégrées dans une pâte de ciment afin de minimiser le nombre de sites actifs de corrosion, liés à l’acier en solution interstitielle. Par conséquent, le travail de recherche des points de formation des produits de la corrosion dans la pâte de ciment est simplifié, ainsi que pour l’étude de l’influence des fissures sur le procédé de la corrosion.
Les techniques de contrôle de la corrosion (i.e. la mesure du potentiel en circuit ouvert et la résistance de la polarisation linéaire) sont corrélées avec des analyses chimiques et de microstructure : parmi elles, la spectroscopie Raman, afin d’étudier les spécimens. Les résultats suivants sont obtenus : diverses produits de corrosion se forment, surtout à l’intérieur des fissures de rétrécissement, les volumes spécifiques sont dans un intervalle typique de 2 à 3, les fissures ont un impact plus important sur le taux de corrosion de l’acier dans un ciment blanc que dans un ciment de type 10 et le joint à la surface des fissures utilisant de l’époxy n’empêche pas la formation de la corrosion sous l’époxy.
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Marcotte, T., Hansson, C. Corrosion products that form on steel within cement paste. Mater Struct 40, 325–340 (2007). https://doi.org/10.1617/s11527-006-9170-4
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DOI: https://doi.org/10.1617/s11527-006-9170-4