Corrosion of steel reinforcement in concrete is the predominant reason for the shortened lifespan of reinforced concrete structures. It poses significant challenges in terms of public safety, economics, and environmental impact, making its monitoring and prevention an essential endeavour of modern society. The utilization of characterization methods for the purpose of monitoring the condition of steel reinforcement is therefore a subject of many scientific investigations.
As part of this master's thesis, the technique of electrochemical impedance spectroscopy (EIS) was employed to monitor 12 reinforced concrete samples over the course of a year. Each sample consists of a pair of carbon steel bars embedded in concrete, with one of the bars artificially embedded with a crevice at the interfacial boundary, simulating a natural installation flaw. Prior to the beginning of the experiment, a subset of the samples was subjected to accelerated carbonation of concrete. During the experiment, all the samples were immersed weekly into an electrolyte solution, with half of the samples using tap water and the other half using a NaCl solution. After the conclusion of the measurement period, the magnitude of corrosion damage was assessed through X-ray imaging of the steel reinforcement.
The objective of this thesis is to evaluate the applicability of the EIS technique for monitoring the corrosion processes of concrete reinforcement, along with assessing the influence of various parameters on the corrosion rate. The results of the experiment demonstrate a great effectiveness of the method in monitoring corrosion, as well as a large impact of the measured parameters on the corrosion progression. Unlike many other techniques, EIS provides insights into the mechanistic processes of corrosion and enables the determination of different contributions to the overall corrosion rate. The experiment also revealed several limitations of the method. The measurement process is relatively time-consuming, and the analysis and interpretation of results are highly demanding. Furthermore, the concrete samples exhibit a high degree of non-ideal behaviour and, in certain cases, low temporal stability, further complicating the process.
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