Assessment of Early Corrosion in Prestressed Concrete Based on Open-Circuit Potential and Polarization Resistance

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Title: Assessment of Early Corrosion in Prestressed Concrete Based on Open-Circuit Potential and Polarization Resistance

Author(s): William Vélez and Fabio Matta

Publication: Special Publication

Volume: 304

Issue:

Appears on pages(s): 113-122

Keywords: corrosion, polarization resistance, prestressed concrete

Date: 10/27/2015

Abstract:

When prestressed concrete (PC) bridge members such as girders and piles are exposed to chloride-laden environments, bonded prestressing strands can corrode prematurely. If corrosion is not detected timely, the strands may be damaged due to the effects of concurrent corrosion and tensile (prestressing) stresses, thus reducing the nominal strength of the member and increasing the risk of collapse. Accurate methods for detecting early corrosion in PC are needed to inform efficient decision-making for maintenance. Polarization resistance (Rp) is directly related to the charge transfer rate on the metal surface, making it a physically meaningful parameter to assess corrosion. Related measurements can be used to estimate corrosion rates in reinforced concrete, but their applicability to PC has not been studied. This paper discusses the feasibility of using Rp-based criteria for early corrosion detection in PC. Five PC pile specimens were exposed for over two years to salt water wet/dry cycles. Open-circuit potential and Rp measurements were routinely performed. After detecting sustained drops of open-circuit potential and Rp and keeping the specimens under exposure for different periods, the strands were removed and inspected to assess corrosion vis-à-vis electrochemical measurements. The results were used for the preliminary definition of open-circuit potential and Rp thresholds associated with different corrosion patterns on prestressing strands in PC structures.