Exploratory Study on Bond Behavior of Textured Epoxy-Coated Reinforcing Bars

Abstract

Research and experience have both shown that epoxy-coated reinforcement, the use of which is mandated by most state departments of transportation for bridge decks, increases cracking. Although the epoxy coating protects the steel from corrosion, bond strength is compromised and the increased cracking exacerbates durability issues in concrete. As a means to improve bonds and reduce the formation of cracks, the Illinois Department of Transportation (IDOT) proposed texturizing the surface of epoxy-coated bars. IDOT developed a prototype textured epoxy coating, and this paper details a preliminary study on the bond strength of reinforcing bars with the new coating. Direct pull-out and beam specimens are tested to compare the bond characteristics of uncoated, standard epoxy-coated, and textured epoxy-coated (TEC) No. 5 (15.9-mm diameter) and No. 8 (25.4-mm diameter) reinforcing bars. Bars with the textured epoxy coating showed good force-slip behavior comparable with black steel initially, but a rapid degradation in slip resistance was observed. In flexure, the TEC reinforcement demonstrated significantly higher slip resistance and resistance to crack widening compared with the conventional epoxy-coated bar. Overall, the added frictional resistance of the textured epoxy-coating showed promise. However, further research is needed to optimize the coating and characterize its behavior.