Recent catastrophic failures of non-composite precast prestressed concrete beam girders due to corrosion of the prestressing steel have highlighted the need to improve the inspection and maintenance of this type of bridge structure in the United States. Nondestructive evaluation (NDE) techniques and physical testing have a potential for detection of corrosion and other causes induced damage to strands and tendons. However, the performance of those was not validated and no protocols exist for their application in condition assessment of prestressed concrete girders. The Federal Highway Administration's (FHWA's) Long Term Performance (LTBP) Program initiated a project with the ultimate goal to develop protocols for the implementation of NDE technologies and physical testing in the monitoring of in-service prestressed concrete girder bridges. The primary NDE technology of interest in detection of deterioration and breakage of strands and tendons was magnetic flux leakage (MFL). In addition, a number of other NDE technologies, primarily used in the condition assessment of reinforced concrete structures were deployed. Three technologies in the corrosion assessment included: electrical resistivity (ER), half-cell potential (HCP) measurement and linear polarization resistivity (LPR). The primary technology in the assessment of possible delamination was impact echo (IE), while concrete quality was assessed using ultrasonic surface waves (USW) method. The NDE technologies were complemented with physical sampling. It included measurement of the carbonation depth using a phenolphthalein solution, and acidsoluble chloride analysis to determine the spatial distribution of chloride ions in concrete and final chloride diffusion coefficients. There were two test beds: full-size prestressed bridge girders and validation slabs with engineered defects on prestressing strands. The primary test bed of this project is a pair of full-size prestressed bridge girders that were removed from an active bridge. Three validation slabs were constructed with prestressing strands laid lengthwise throughout with known amounts of strand damage artificially created at known locations. Findings regarding the performance of mentioned NDE technologies in the assessment of prestressed girders are presented.
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