An improved numerical approach to model corrosion potential in reinforced concrete

Title: An improved numerical approach to model corrosion potential in reinforced concrete
Author(s): Ge Ji, O. Burkan Isgor
Paper category : conference
Book title: 2nd International RILEM Symposium on Advances in Concrete through Science and Engineering
Editor(s): J. Marchand, B. Bissonnette, R. Gagné, M. Jolin and F. Paradis
Print-ISBN: 2-35158-003-6
e-ISBN: 2351580028
Publisher: RILEM Publications SARL
Publication year: 2006
Nb references: 16
Language: English

Abstract: A comprehensive finite element model for predicting the rate of steel corrosion in concrete structures has been previously developed. The model consists of the solution of Laplace’s equation for electric potentials with nonlinear boundary conditions imposed by the polarization of the steel surface in concrete and the determination of the current densities along the steel reinforcement from the calculated potentials. The boundary conditions imposed on the steel surface due to activation and concentration polarization are functions of current density; hence the problem is nonlinear. The level of nonlinearity depends on the type and degree of polarization on the steel surface.
For cases in which activation polarization is the main mode of polarization, nonlinear solution algorithms that are based on the direct iteration method are feasible, albeit not guaranteed. However, for cases, in which the concentration polarization at the cathodes is significantly high, the convergence of the solution becomes rather slow, if at all possible.
Authors of this paper have been working on innovative methods to improve convergence of the nonlinear solution of Laplace’s equation for cases in which the direct iteration method fails. In this paper, one of these approaches, a modified version of the direct iteration method that uses an under-relaxation factor and adjustment for the limiting current density, is presented. With this method, the convergence rate of the solution is significantly improved, and the number of unstable cases are reduced.

Keywords: corrosion, polarization, nonlinearity, Laplace’s equation, convergence

Online publication: 2006-08-02
Classification: 3.1 Theme 1: Numerical Models: from Microstructure to Transport Properties and Durability
Publication type : full_text
Public price (Euros): 0.00
doi: 10.1617/2351580028.027