Wiss, Janney, Elstner Associates, Inc. performed an in-depth field investigation into the performance of epoxy-coated reinforcing bars in four bridge decks for the Minnesota Department of Transportation. The objective of the study was to evaluate the performance of four of the oldest bridge decks containing epoxy-coated reinforcing steel that are subjected to deicing chemicals. The study included two decks built on steel girders and two built on precast concrete girders. Two decks had been overlaid with a 2-inch portland cement-based concrete low slump overlay as part of the original construction.
The bridges were all built between 1973 and 1978 and are now approximately 17 to 22 years old. A visual, crack, and delamination survey was performed on each structure. Deck cracking allows direct and immediate access of deicing chemicals to the reinforcing bars. Deterioration of the epoxy coating due to underfilm corrosion was most evident in areas having cracking or delaminations. Transverse deck cracks were commonly aligned directly over reinforcing bars. The steel girder bridges had more deck cracks than the concrete girder bridges. The decks without cracks were in better condition than those containing cracks.
