Determination Of Bridge Deck Subsurface Anomalies Using Infrared Thermography And Ground Penetrating Radar

794714PDFResearch PaperFHWA-KS-96-2Bridge decksTest proceduresGround penetrating radarOverlays (Pavements)Asphalt concrete pavementsDebondingKansasAlt, David G.Meggers, David A.Kansas. Dept. of TransportationUnited States. Federal Transit AdministrationNTL-HIGHWAY/ROAD TRANSPORTATION-Bridges and StructuresNTL-HIGHWAY/ROAD TRANSPORTATION-Construction and MaintenanceNTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and PerformanceUS Transportation CollectionThe purpose of this study was to evaluate the use of infrared (IR) thermography and ground penetrating radar (GPR) to find subsurface anomalies, delaminations and de-bonding, on asphalt concrete overlaid concrete bridge decks. The traditional "chaining" method is a less effective option for finding subsurface defects after an overlay is in place. An IR thermographic and GPR (IR/GPR) evaluation was conducted on the I-70 Polk-Quincy viaduct in 1993. The results were compared to other studies conducted to check for subsurface anomalies. These included a 1989 Geology bridge deck evaluation, completed before the membrane and overlay were in place, a 1992 membrane-pavement system electrical resistivity study, and a 1996 Research evaluation to check for de-bonding. The last two studies were completed after the asphalt concrete overlay was in place. There were differences between the results of the IR/GPR study and those conducted using the more traditional methods. The IR/GPR survey did not find many of the de-bonded and delaminated areas found using the conventional methods. This is not to say that IR thermography and GPR are of little value and inaccurate. The fact that the Polk-Quincy viaduct has been overlaid with both concrete and asphalt, and it is in a general state of deterioration may have made it difficult to obtain good results. Another IR/GPR study will be conducted in 1998 and results will be compared to the 1993 study