Bond of Epoxy-Coated Reinforcement to Concrete: Splices

Abstract

The effects of epoxy coating and transverse reinforcement on the splice strength of reinforcing bars in concrete are described. Tests included 65 beam and slab splice specimens for members containing No. 6 and No. 8 bars. The average coating thickness ranged from 6 to 11 mis. Three deformation patterns were used in the study. 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 significantly reduce splice strength. However, the extent of the reduction is less than used to select the development length modification factors in the 1989 AASHTO Bridge Specifications and 1989 ACI Building Code. 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 of both coated and uncoated reinforcement. A 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 minimum amount of transverse reinforcement, if the positive effects of that transverse reinforcement are not already taken into account in the design provisions. The 1.20 factor is, thus, not applicable to the ACI Building Code but is applicable to the AASHTO Bridge Specifications. This report is the third in a continuing series describing research at the University of Kansas to gain a better understanding and develop accurate design procedures that reflect the changes in bond strength caused by the use of epoxy coating on reinforcing bars.