| Summary: | Corrosion of steel reinforcement in concrete initiated by the ingress of chloride is one of the main factors causing deterioration and damage of concrete structures all over the world. The aim of this study was to investigate the corrosion rate of steel reinforcement in concrete specimens under controlled exposure conditions by using electrochemical techniques. The determination of the level of chloride concentration is used to differentiate the gray zone between the initiation and propagation period of steel corrosion. Three different parameters were used in this study. The first parameter was the types of concrete mixes, namely, Ordinary Portland Concrete (OPC) and High Performance Concrete (HPC). The second parameter was the four different concentrations of sodium chloride solution 0%, 1 %, 3% and 5%, in which the test specimens were immersed in. The third parameter was the four types of environmental exposure conditions, namely, in-door laboratory, outdoor, oven drying and immersing in sodium chloride solution all the time. Tafel plot, linear polarization resistance and impedance spectroscopy techniques were used to access corrosion and to determine corrosion rate for each of the test specimens. For electrochemical impedance spectroscopy, equivalent circuit was used for modeling the Nyquist plot of real and imaginary impedance. The electrochemical parameters calculated were used to explain the behaviour of specimens under corrosion. High performance concrete achieved better results compared with ordinary Portland cement concrete in terms of the corrosion rate, chloride concentration at different depths of the specimens and time necessary to initiate corrosion. The effectiveness and adaptability of the use of the electrochemical techniques to evaluate corrosion of reinforcement in concrete are established in the following order; the Tafel Plot, Linear Polarization Resistance and the Electrochemical Impedance Spectroscopy.
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