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The corrosion rate of rebar in concrete traditionally has been determined using polarization methods such as the potentiodynamic technique, galvanostatic pulse technique, potentiostatic pulse technique, and, in some cases, the electrochemical impedance spectroscopy technique in laboratory applications. These techniques are very slow, and all require having an electrical connection to the rebar, which makes them impractical in the field. In this paper, the recently developed technique of Connectionless Electrical Pulse Response Analysis (CEPRA) will be introduced. The CEPRA method, which eliminates the need to have a rebar connection, is based on the concept that the voltage response of the corroding rebar is different from that of the noncorroding rebar once subjected to variable frequencies of an AC current applied on the concrete surface using the four-probe Wenner array configuration. However, direct measurement of the low-frequency impedance of rebar in concrete is very time-consuming and vulnerable to noise interruption; hence, in the CEPRA method, a narrow current pulse is applied for a short period of time (for a couple of seconds). Using the recorded voltage and the applied current, the low-frequency impedance response of rebar in concrete can be extracted, which can be used to determine the state of corrosion in reinforced concrete structures. The details of the CEPRA technique and equivalent electrical circuit models will be discussed in this paper. Laboratory and finite element modeling results will be presented to compare the traditional corrosion rate measurement techniques with the CEPRA method.

This paper presents an investigation of five corrosion‐monitoring techniques for reinforced concrete. The techniques studied are the potentiodynamic, galvanostatic, and coulostatic direct‐current techniques as well as electrochemical impedance spectroscopy (EIS), and the connectionless electrical pulse response analysis (CEPRA) technique. The study included monitoring corrosion rates on reinforced concrete specimens with a range of admixed chloride percentages, cover depths, and rebar diameters for 8 months. After this period, the rebars were extracted for mass loss measurements to determine the average corrosion rates. EIS was found to provide accurate measurements of active and passive corrosion rates with a simplified spectrum‐analysis procedure. Galvanostatic and potentiodynamic techniques were able to measure the corrosion rates for actively corroding reinforcements accurately, while the coulostatic technique overestimated it. For passive reinforcements, the coulostatic technique provided reliable corrosion rate estimates, while the potentiodynamic technique provided a minor overestimation, due to the fast scan rate used, and the galvanostatic technique failed in detecting passivity, due to the short measurement duration and confinement failure. Finally, the CEPRA technique provided accurate corrosion rate predictions except for passive rebars with small diameters embedded in saturated concrete.

This paper presents results of a study conducted to determine the corrosion‐resistance of chromium‐steel (ASTM A1035 steel) and several stainless steel grades (316LN, 304, 2205, and XM‐28), as concrete reinforcements. The study included laboratory experiments investigating the reinforcements’ performance in a concrete pore solution containing chlorides, with and without wetting and drying cycles, as well as in cases of cracked and uncracked concretes exposed to chlorides. The study also included field‐exposure experiments, where reinforced mortar bars and bare bars were exposed to a marine tidal environment. Results indicated that the service‐life enhancement provided by these reinforcements was highly dependent on their alloy composition. ASTM A1035 steel was found to be less corrosion‐resistant than all stainless steel grades, due to the lower alloy contents. XM‐28 was also found to have a substantially lower corrosion resistance compared to other stainless steels, due to the incorporation of manganese, coupled with the lower nickel content. Finally, 304, 316LN, and 2205 reinforcements showed no signs of corrosion onset in all experiments, even in cases of cracked concrete.

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