Item – Theses Canada

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OCLC number
1006660657
Link(s) to full text
LAC copy
LAC copy
Author
Martin-Perez, Beatriz,1967-
Title
Service life modelling of R.C. highway structures exposed to chlorides.
Degree
Ph. D. -- University of Toronto, 1999
Publisher
Ottawa : National Library of Canada = Bibliothèque nationale du Canada, [2000]
Description
2 microfiches
Notes
Includes bibliographical references.
Abstract
The detrimental effect of chloride-induced corrosion on the service life of reinforced concrete highway structures highlights the need for the development of mathematical models that describe the mechanisms of corrosion and damage build-up in reinforced concrete. The objective of this study was to develop a generalized computer model for the prediction of service life of reinforced concrete highway structures exposed to de-icing salts. The mathematical formulation idealized the corrosion sequence as a two-stage process: an initiation stage, during which chloride ions penetrate to the reinforcing steel layer and depassivate it, and a propagation stage, in which active corrosion takes place until cracking of the concrete cover has occurred. In modelling chloride transport to the reinforcing steel (initiation stage), a modified version of Fick's 2'nd' law was used, in which the processes of diffusion, chloride binding, and convection due to water movement were taken into account. The migration of chloride ions through concrete was coupled with moisture diffusion and heat transfer within concrete. Corrosion was assumed to initiate when the chloride concentration at the steel layer reaches a specified threshold value. To model the stage corresponding to active corrosion (propagation stage), the rate of corrosion was linked to oxygen availability at the cathodic areas. The governing partial differential equations that idealize the problem were solved numerically in space as a boundary-value problem and in time as an initial-value problem by means of a two-dimensional finite element formulation, in which appropriate boundary conditions were enforced to simulate the seasonal variations in exposure conditions. A time-step integration procedure was applied to determine the variation in time of the various species concentrations at the level of the reinforcement. To assess the mechanical damage resulting from the expansion of the corrosion products, an equivalent uniform internal pressure was applied around the steel/concrete interface, and the resulting state of stress in the surrounding concrete was evaluated by means of an elastic analysis. The numerical performance of the model was examined in few example cases to assess the relative importance of the different mechanisms considered on the service life of reinforced concrete structures exposed to chloride environments.
ISBN
061241230X
9780612412309