Abstract
This paper reports a laboratory-based study carried out to compare the performance of various proprietary concrete protection systems, designed to reduce chloride ingress and reinforcement corrosion. These include: controlled permeability formwork (CPF), a silane/siloxane hydrophobic surface treatment (S/S), an integral liquid waterproofing admixture (WP) and a corrosion-inhibiting chemical admixture (CI). Tests were carried out on a Portland cement (PC) concrete (40 N/mm2 design strength) for chloride diffusion index (using a two-cell compartment accelerated test) and, under cyclic wetting and drying conditions, total chloride content at cover depth (25 mm) and corrosion of carbon steel in reinforced concrete specimens (using half-cell potential and corrosion current density (polarisation resistance) measurements). The results indicate that for all protection systems, resistance to chloride ingress was improved, with the greatest benefits noted for the S/S and CPF concretes. Corrosion levels occurring for these generally followed the ranking of chloride ingress rates. The CI was found to reduce the rate of chloride ingress and to give lowest corrosion current densities in relation to chloride contents. This system appeared to provide best overall performance. The practical implications of the results are considered in terms of equivalence of the systems to an increase in design strength or cover depth,i.e. parameters used for specifying concrete durability in standards, and the wider issues relating to their selection and use are reviewed.
Résumé
Ce papier présente une étude réalisée en laboratoire afin de comparer les performances de divers systèmes de propriétés de protection du béton, conçus pour réduire l'entrée des chlorures et la corrosion des armatures. Ceux-ci incluent le cadre contrôlé de perméabilité (CPF), un traitement de surface hydrophobe à base de silane/siloxane (S/S), un liquide intégral imperméabilisant le mélange (WP) et un mélange chimique empêchant la corrosion (CI). Les essais ont été effectués sur du béton de ciment Portland (résistance de 40 N/mm2) pour l'indice de diffusion des chlorures (en utilisant un essai accéléré avec compartiment à deux cellules) et, sous conditions cycliques sèches et humides, le contenu total des chlorures à la profondeur de couverture (25 mm) et la corrosion de l'acier de carbone dans les échantillons de béton armé (à l'aide des mesures du potentiel à mi-cellule et de la densité de courant de la corrosion (résistance de polarisation)). Les résultats indiquent que pour tous systèmes de protection, la résistance à l'entrée des chlorures a été améliorée, avec les plus grands profits notés pour les bétons de S/S et CPF. Les niveaux de corrosion observés pour ceux-ci, ont suivi généralement le classement des taux d'entrée des chlorures. Le CI s'est avéré pouvoir réduire le taux d'entrée des chlorures et donner les densités de courant de la corrosion les plus basses par rapport aux contenus de chlorures. Ce système est apparu comme offrant les meilleures performances générales. Les implications pratiques de ces résultats sont considérées en termes d'équivalence des systèmes à une augmentation de la résistance de base ou de la profondeur de couverture, à savoir les paramètres utilisés pour spécifier la durabilité du béton dans les normes, et les questions plus larges relatives à leur sélection et à leur usage sont réexaminées.
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McCarthy, M.J., Giannakou, A. & Jones, M.R. Comparative performance of chloride attenuating and corrosion inhibiting systems for reinforced concrete. Mat. Struct. 37, 671–679 (2004). https://doi.org/10.1007/BF02480512
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DOI: https://doi.org/10.1007/BF02480512