Bond of Epoxy-Coated Reinforcement: Splices

Abstract

The effects of epoxy coating and transverse reinforcement on the splice strength of reinforcing bars in concrete are described. A total of 65 beam and slab splice specimens containing No. 6 and No. 8 bars were tested. The average coating thickness ranged from 6 to 11 mils (0.15 to 0.28 mm). Three deformation patterns were used. All but one group of specimens contained Class B ACI/Class C AASHTO splices. The results of the current study are analyzed, along with the results of 48 specimens from earlier studies, and used to develop improved development length modification factors for use with epoxy-coated bars. Epoxy coatings are found to reduce splice strength significantly; however, the extent of the reduction is less than that used to select the development length modification factors in the 1989 ACI Building Code and 1989 AASHTO Bridge Specifications. The percentage decrease in splice strength caused by epoxy coating is independent of the degree of confining reinforcement, which provides approximately the same percentage increase in the strength of splices for both coated and uncoated bars. A maximum development length modification factor of 1.35 is applicable for design with epoxy-coated reinforcement. An alternate factor of 1.20 is applicable for epoxy-coated bars with a defined minimum amount of transverse reinforcement if the positive effects of that transverse reinforcement are not already taken into account in the design provisions. Thus, the 1.20 factor is not applicable to the ACI Building Code, but is applicable to the AASHTO Bridge Specifications. This is the second in a series of papers describing research at the University of Kansas on epoxy-coated reinforcement. The research is aimed at gaining a better understanding of the bond of epoxy-coated reinforcement to concrete and developing design procedures that accurately reflect the changes in bond strength caused by epoxy coating.