Multi-level modelling of chloride ingress into saturated concrete

Author(s): T.Q. Nguyen, V. Baroghel-Bouny, P. Dangla, P. Belin
Paper category: Workshop
Book title: International RILEM Workshop on Performance Based Evaluation and Indicators for Concrete Durability
Editor(s): V. Baroghel-Bouny, C. Andrade, R. Torrent, K. Scrivener
ISBN: 978-2-912143-95-2
Pages: 145 - 155
Total Pages: 11
Language: English

Abstract: 
Within the framework of the prediction of reinforced concrete structure service-life, a multi-level approach to model chloride ingress into concrete is investigated. In such an approach, durability indicators are introduced as input data. First, a simple model which includes only the species (Clˉ) is proposed for engineering purposes or when the chemical composition is not known in details. A second model has been developed according to a multi-species approach: it takes into account the ions Clˉ, OHˉ, H₃O⁺, Na⁺, and K⁺, along with their influence on chloride transport. The ion-ion electrical interactions are taken into account. Chloride binding is described in these models by Freundlich's or Langmuir's isotherm. In order to distinguish chemical and physical processes, a third model addresses separately physical adsorption of chlorides onto C-S-H layers, as a result of exchange between Clˉ of the pore solution and OHˉ of the C-S-H, and chemical reactions (formation of Friedel's salt, as a result of dissolution of Ca(OH)₂ and C₃Aeq). Seven ionic species (OH⁻, H₃O⁺, Na⁺, K⁺, Ca²⁺, Al(OH)₄⁻ and Cl⁻) and four solid compounds (Ca(OH)₂, C-S-H, C₃Aeq, and Friedel's salt) are taken into account in this model, in order to describe the dissolution-precipitation phenomena. The validation of the various models has been performed on the basis of a comparison between predicted kinetics of chloride penetration or total chloride concentration profiles and experimental ones obtained on various types of materials and environmental conditions (diffusion tests under steady or non-steady-state conditions and marine site data).

Online publication: 2007
Publication Type: full_text
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