Transport Modeling of Chlorides with Binding in Concrete
| Autor: | Mohammed A. Shazali, M.K. Rahman, Ali H. Al-Gadhib, Mohammed H. Baluch |
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| Rok vydání: | 2012 |
| Předmět: | |
| Zdroj: | Arabian Journal for Science and Engineering. 37:469-479 |
| ISSN: | 2191-4281 1319-8025 |
| DOI: | 10.1007/s13369-012-0182-9 |
| Popis: | Chloride-induced corrosion is one of the most revealing cause of deterioration leading to premature durability loss by structural concrete. Among mechanisms governing penetration of chloride ions into the concrete, ingress by simple diffusion is the most decisive one for concentration-driven transport. The use of Fick’s law of diffusion of the second type does in general permit a modest preliminary analysis of the diffusive transport subject to certain constraints, primarily associated with stationary chloride diffusion coefficient hypothesis. A realistic critique to such analysis based on constant chloride diffusivity is however its total disregard of intrinsic chloride-binding capacity evidently exhibited by cement-based materials constituent to the concrete. Given that the chlorides are also partly free and partly bound in concrete, the significance of chloride binding for a more accurate service life analysis of the concrete is of practical concern. Moreover, the challenge raised by chloride binding against the invariant diffusivity assumption cannot also be ignored, because only free chlorides diffuse into and through the bulk concrete to thereafter directly pose corrosion risk. Since chloride transport in cementitious material such as concrete based on one or another chloride-binding mechanism may also be quite different, careful choice of chloride-binding model, consistent with the underlying phenomenological behavior, is critical for its implication to service life predictions. The aim of this study is therefore to examine the effect of chloride binding in terms of their isotherm formulations on time to corrosion activation resulting from transport of chloride ions in saturated concrete. Numerical analysis employing nonlinear finite element modeling techniques is used to account for null, linear and nonlinear chloride-binding formulations, including Langmuir and Freundlich representations for the nonlinear types, on the chloride transport problem. Results of the analysis, in view of experimental chloride-binding and penetration profile data mined from the literature, are presented to quantifiably underscore the effects that various binding parameters significantly have on onset of chloride-induced corrosion in relation to specific durability requirements. |
| Databáze: | OpenAIRE |
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