Development of Hand-Held Thermographic Inspection Technologies

011404602009FINAL REPORTPDFTech ReportOR10-007RI06-038OverpassesConcrete bridgesDeteriorationCrackingInfrared detectorsNondestructive testsField testsRemote sensingThermographsInfraredthermographyimagingconcretedelaminationscorrosioncondition assessmentbridge inspectionenvironmental conditionsResearch HubMissouriUnited StatesUniversity of Missouri--Columbia. Dept. of Civil and Environmental EngineeringWasher, GlennFenwick, RichardBolleni, NaveenUniversity of Missouri--Columbia. Dept. of Civil and Environmental EngineeringMissouri. Department of TransportationUnited States. Federal Highway AdministrationNew York (State). Dept. of TransportationTexas. Dept. of TransportationUS Transportation CollectionThis study explored the application of hand-held thermographic cameras for the detection of subsurface delaminations in concrete bridges. The goal of the research was to provide maintenance and inspection personnel with an effective tool for detecting and monitoring concrete deterioration without disrupting traffic flow. The objectives of the research included developing guidelines for the use and application of the technology by characterizing the environmental conditions necessary for thermography to be effective. This included evaluating the effects of solar loading, diurnal temperature variations, wind speed and relative humidity. The applicability of the technology to areas of a bridge with and without radiant heating from the sun was studied. A second objective of the research was to investigate the operational constraints to implementation by providing the technology to states to be used in the condition assessment of bridges. The deterioration of concrete as a result of corrosion of embedded reinforcing steel is a widespread problem for State Departments of Transportation. Corrosion typically initiates at the level of the embedded reinforcing steel, resulting in delaminations in the concrete that are not apparent through visual assessments of the surface of the concrete. As the deterioration progresses, delaminations develop into spalling of the concrete that further exposes the reinforcing steel to the ambient environment, resulting in increased deterioration rates. Additionally, spalling of the concrete reduces the service life of bridge decks and can create hazardous driving conditions. Concrete that spalls from the soffit of overpass bridges can fall into traffic and present a hazard to motorists