Research On Electrochemical Rehabilitation Methods For Reinforced Concrete Structures

Electrochemical rehabilitation methods are considered as the research objectives in this paper. The electrochemical chloride extraction (ECE) and the electrochemical realkalization (ERA) are studied systematically to promote the application of electrochemical rehabilitation methods.Firstly, the chloride's corrosion effect on the concrete is studied. Based on the summary of the development of test methods of chloride diffusion, various test methods are compared, and strengths and weaknesses of varied test methods are listed. Then, theories of chloride diffusion are summarized. A list of theoretical equations of chloride diffusion are introduced, and it is demonstrated that the chloride diffusion theory is improved gradually by taking into account varieties of factors, which can affect the chloride diffusion. Based on all these research on the chloride diffusion, the mechanism, operation process, strengths and side- effect of ECE are analyzed.Secondly, the realkalization technique is introduced from diverse research fields. â‘  Different ideas on the mechanism of the realkalization technique are formed around the world. By comparing all these ideas, the mechanism of the realkalization is analyzed completely and profoundly, and questions about it are answered. â‘¡ Experimental methods for realkalization research are summarized and classified into three types. And differences among these methods are analyzed. Considering that many test techniques are rarely used, some reliable test techniques are discovered and introduced for researchers to use. â‘¢ The research route of the control theory is anatomized, the development of research on it is analyzed, defects in the research are disclosed, and a comparatively accurate control theory is recommended. â‘£ The effectiveness, safety and other problems of the realkalization are analyzed.Finally, the durability of the realkalization is studied, and after the analysis of this problem, it is found that the outward diffusion of sodium carbonate, one of the common used electrolytes, can serve to affect the durability significantly. Therefore, the outward diffusion of sodium carbonate is studied in the thesis. By analyzing andsimplifying the diffusion reasonably, the theoretical model regarding the density development of sodium carbonate in realkalized concrete is established based on Fick's second law of diffusion. According to this equation, the evolution of sodium carbonate can be computed directly and conveniently, and the theory of the durability longevity of the realkalization and some other relevant theories are deduced based on further theoretical and experimental research. These theories can be used to estimate the durability longevity, and to calculate the realkalization thickness and the density of the electrolyte of the sodium carbonate, which solves some vital problems in the realkalization research. Additionally, some examples are employed to illuminate the application of these theories. -Furthermore, an experiment is designed and the experimental procedure is presented. Experimental results can be used to be compared with calculated results by theories established formerly to improve these theories.