Abstract
The calculation of non steady state chloride diffusion coefficients by migration tests is a quite controversial subject due on one hand, to the complexity found in describing the penetration of chlorides and on the other hand, to the fact that the different researchers calculate them by different procedures. Therefore, in present work, experimental trials have been carried out performing migration tests following ASTM C1202-91 procedure, and modified by applying 12 Volts. Results from migration methods have been compared with natural diffusion results from tests that were performed in two different experimental conditions. From these tests, calculations of non-steady-state diffusion coefficients, Dns, have been carried out, resulting that migration tests give results in the same order of magnitude than those obtained from natural diffusion tests. However, as it is not known how far the diffusion tests reproduce the real conditions, it has been concluded that, in the lack of a reference method reproducing realistic conditions, either diffusion or migration tests cannot be used more than for comparative purposes. Further research is needed on development of tests able to reproduce real performance.
Résumé
Le calcul du coefficient de diffusion des chlorures en régime non-stationnaire par des essais de migration est un sujet assez controversé en raison, d'une part, de la complexité que présente la description de la pénétration des chlorures et, d'autre part, du fait que les différents chercheurs utilisent des procédés de calcul différents. C'est pourquoi dans ce travail, les essais expérimentaux e performance ont été menés selon la méthode ASTM C1202-91, et modifiés par l'application d'un potentiel de 12 volts. Les résultats obtenus par méthodes de migration ont été comparés aux résultats obtenus avec des essais de diffusion naturelle effectués sous deux conditions expérimentales différentes. À partir de ces essais, le calcul des coefficients de diffusion en régime non-stationnaire, Dns, a été effectué. Il en résulte que les essais de migration donnent des résultats du même ordre de grandeur que ceux obtenus avec les essais de diffusion naturelle. Cependant, puisque l'on ne sait pas dans quelle mesure les essais de diffusion sont représentatifs des conditions réelles, l'étude arrive à la conclusion que, faute d'une méthode de référence reproduisant les conditions réelles, ni les essais de migration, ni ceux de diffusion ne peuvent être utilisés au-delà d'une simple comparaison. D'autres travaux sont nécessaires pour développer des essais capables de reproduire les performances réelles.
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Dr. Carmen Andrade is Vice-President of RILEM and a RILEM Fellow. She is the Chairlady of RILEM TC 154-EMC: ‘Electrochemical techniques for measuring metallic corrosion’ and of RILEM TC 178-TMC: ‘Testing and modelling chloride penetration in concrete’. She is also Director of CSIC, a Titular Member. Dr. Castellote is a member of RILEM TC 178-TMC. Dr Alonso is a RILEM Senior Member and participates to the work of RILEM TC 154-EMC.
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Andrade, C., Castellote, M., Alonso, C. et al. Non-steady-state chloride diffusion coefficients obtained from migration and natural diffusion tests. Part I: Comparison between several methods of calculation. Mat. Struct. 33, 21–28 (2000). https://doi.org/10.1007/BF02481692
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DOI: https://doi.org/10.1007/BF02481692