Bond Strength of Epoxy-Coated Reinforcing Bars

In this study, 21 beam specimens were tested to determine the bond strength of epoxy-coated and uncoated reinforcing bars in tension. Specimens were constructed with either #6 or #11 bars spliced in the center of the beam. Bars were uncoated with normal mill scale or epoxy-coated with a nominal coating thickness of 5 or 12 mils. The concrete strength ranged from 4000 psi to 12,600 psi. Seventeen specimens were top cast (more than 12 in. of concrete below) and four were bottom cast.

Performance was evaluated using measured bond strength, crack width and spacing, and stiffness of the beams. Results indicated that epoxy-coated bars developed approximately 65% of the bond of uncoated bars were failure was governed by splitting of the concrete cover. The bond reduction was independent of concrete strength, bar size, and coating thickness. The average width of cracks in coated bar specimens was 50% greater than in uncoated bar specimens; however, comparison of load-deflection diagrams showed no loss of stiffness when using epoxy-coated bars.