Abstract
The most common methods for detecting chloride-induced corrosion in concrete bridges are half-cell potential (HCP) mapping, electrical resistivity (ER) measurements, and chloride concentration testing, combined with visual inspection and cover measurements. However, studies on corrosion detection in pretensioned structures are rare. To investigate the applicability and accuracy of the above methods for corrosion detection in pretensioned bridge girders, we measured pretensioned I-shaped girders exposed to the Norwegian coastal climate for 33 years. We found that, even combined, the above methods can only reliably identify general areas with various probabilities of corrosion. Despite severe concrete cracking and high chloride content, only small corrosion spots were found in strands. Because HCP cannot distinguish corrosion probability in the closely spaced strands from other electrically connected bars, the actual condition of individual strands can be found only when concrete cover is locally removed. Wet concrete with high chloride content and accordingly low HCP and low ER was found only in or near the girder support zones, which can therefore be considered the areas most susceptible to chloride-induced corrosion. We conclude by proposing a procedure for the inspection and assessment of pretensioned girders in a marine environment.
Highlights
Chloride-induced corrosion in aging pretensioned concrete bridge girders due to exposure to an aggressive coastal environment, or inadequate durability design, is recognized as an increasing deterioration problem in coastal bridges in Norway and globally [1,2,3]
A study of 227 pretensioned girder bridges exposed to the Norwegian coastal climate revealed that about 37% have reinforcement corrosion in pretensioned girders because they have less concrete cover than the minimum that was required by Norwegian regulations when they were built [2]
The main objective of this research was to determine a reliable procedure for detecting corrosion in pretensioned concrete bridge girders, which combined half-cell potential (HCP) mapping, electrical resistivity (ER) measurements, chloride content testing, and concrete cover measurements, with visual inspection
Summary
Chloride-induced corrosion in aging pretensioned concrete bridge girders due to exposure to an aggressive coastal environment, or inadequate durability design, is recognized as an increasing deterioration problem in coastal bridges in Norway and globally [1,2,3]. Pitting corrosion can result in the fracture of highly stressed strands and ordinary reinforcement, which may considerably reduce the load-bearing capacity of the girders. The main objective of this research was to determine a reliable procedure for detecting corrosion in pretensioned concrete bridge girders, which combined HCP mapping, ER measurements, chloride content testing, and concrete cover measurements, with visual inspection. It aimed to describe the distribution of corrosion probability along pretensioned concrete girders and analyze the factors influencing their corrosion in a marine environment. To investigate the applicability and accuracy of the above measurement methods for corrosion detection in pretensioned bridge girders, we carried out a study based on experimental data collected during field investigations of Dalselv Bridge, a 33-year-old girder bridge exposed to the Norwegian coastal climate
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