Bond of Coated Reinforcing Bars in Concrete

The bond strengths were determined for 23 epoxy-coated (10 different epoxy coatings), six polyvinyl chloride-coated (three different coating materials), and five uncoated reinforcing bars. The length of embedment of the reinforcing bar in the concrete was 12 in. (305 mm). The loads or bond stresses corresponding to a loaded-end slip of 0.01 in. (0.25 mm) or a free-end slip of 0.002 in. (0.051 mm) were considered as critical values in determining the bond strength, depending on which of these values of slip developed first. For coating film thicknesses ranging from 0.001 in. to 0.011 in., the epoxy-coated bars developed bond strengths essentially equal to the bond strengths for uncoated bars. Experimental values were higher than minimum acceptable values in building code and highway bridge requirements. Bond strengths of the polyvinyl chloride-coated bars and bars with thick epoxy coatings were unacceptable.