Simulation of Chloride Ingress through Surface-Coated Concrete during Migration Test Using Finite-Difference and Finite-Element Method

Seyoon Yoon

doi:10.1155/2017/8703736

Abstract

Polymer surface coatings are commonly used to enhance the corrosion resistance of concrete structures in saline environments to ionic diffusivity; this diffusivity can be determined by migration tests. This paper presents the simulation of the effects of the surface coatings on migration tests by solving the Nernst-Planck/Poisson model using both finite-difference method and finite-element method. These two numerical methods were compared in terms of their accuracy and computational speed. The simulation results indicate that the shapes of ionic profiles after migration tests depend on the effectiveness of surface coatings. This is because highly effective surface coatings can cause a high ionic concentration at the interface between coating and concrete. The simulation results were also compared to homogenized cases where a homogenized diffusion coefficient is employed. The result shows that the homogenized diffusion coefficient cannot represent the diffusivity of the surface-coated concrete.

Highlights

The corrosion of the reinforcing steel bars by chloride ingress is a significant problem for the marine concrete structures exposed to seawater
To delay this chloride ingress, the polymer surface coating has been applied to the reinforced concrete
Previous literature clearly shows that this surface coating improves the durability of reinforced concrete (RC) structures [1,2,3]

Summary

Introduction

The corrosion of the reinforcing steel bars by chloride ingress is a significant problem for the marine concrete structures exposed to seawater. Glasser et al [7,8,9] used the Nernst-Planck/Poisson (NPP) model to analyze data of the migration tests [5] This approach improves upon the classical model by including multi-ionic interaction, distribution of electric potentials, and evolution of the electric field. Even though most cases of ionic ingress in reinforced concrete structures dominantly occur by diffusion, in aggressive environments the ingress of multiple ions, such as chloride ingress, calcium leaching, and sulfate attack, can occur in concrete simultaneously For this reason, the NPP model including the migration term can describe the interaction between different ionic species and accurately predict the distribution of multiple ions in reinforced concrete structures

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Discussion

Conclusion