Date of Award

Spring 1-1-2010

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Yunping Xi

Second Advisor

Victor Saouma

Third Advisor

George Hearn

Fourth Advisor

Sivaselvan Mettupalayam

Fifth Advisor

Kevin Rens

Abstract

Chloride is one of the aggressive chemicals that can threat to reinforced concrete structures. This threat is aggravated by damage due to corrosion of reinforcing steel. Over the years, there have been several models related to chloride diffusion in concrete for predicting the service life of reinforced concrete structures subjected to chloride attack. These can be mathematically characterized by diffusion equation based on Fick's law and by sophisticated transport theory, the Nernst-Planck equation. In this thesis, statistical, theoretical, and experimental studies were conducted on the penetration of deicing salts into concrete structures mainly focused on chloride-induced corrosion of reinforcement.

A statistical study presented an analytic method based on a simple solution of one-dimensional diffusion equation, Fick's law, for predicting the probabilistic features of corrosion initiation time of reinforcement in concrete structures subjected to chloride environments. A theoretical modeling was conducted to investigate ion transport in concrete described based on the physical model, the Nernst-Planck equation, which included diffusion mechanism due to ionic concentration gradient and migration process due to electrostatic potential gradient. The model considered the transport of not only chloride ion but also other chemical species involved in the concrete pore solution such as hydroxyl, sodium, potassium, and calcium ions. Then, the model was extended to study the effect of moisture and temperature on the transport of these ions. The two coupled effects of moisture diffusion and chloride penetration; and heat flow and chloride penetration were incorporated in the mathematical model. Several numerical examples were simulated and solved by the proposed models and the obtained results agreed very well with the available test data. The results also showed the basic trends of ion transport in concrete with various initial and boundary conditions. An experimental study on multi-species aggressive chemicals diffusion in concrete was performed based on chloride ponding test. The penetration rate of different chloride-based solutions related to deicers used for ice and snow control was selected as a focus of this task. The experimental results obtained from this study showed that chloride ingress into concrete is dependent on the cations associated in solutions.

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