Interfacial bond behavior between ribbed CFRP bars and UHPFRC: Effects of anchorage length and cover thickness

Abstract

Carbon fiber-reinforced polymer (CFRP) bars and ultra-high-performance fiber-reinforced concrete (UHPFRC) feature high strength, high elastic modulus, and excellent durability, which can be combined and applied to the high-load or corrosive environments. To comprehend the bond behavior between the ribbed CFRP bar and UHPFRC, 30 cubic specimens for axial pull-out tests and 12 cubic specimens for eccentric pull-out tests were tested in this study. The effects of CFRP bar diameter, anchorage length, and cover thickness on the bond behavior were investigated. The results indicated that three different failure modes, which were pull-out failure, splitting failure and splitting-pull-out failure, were detected. The delamination of fibers and resin in the specimens with pull-out failure caused interfacial bond failure between the ribbed CFRP bar and UHPFRC. The bond strength increased from 18.41 MPa to 36.41 MPa when the diameter increased from 10 mm to 12 mm, owing to the increase in the geometric ratios (concrete lug ratio and relative rib area) of the CFRP bar surface. Additionally, the increase of cover thickness was beneficial for improving the interfacial bond strength, and the critical cover thickness was about three times the bar diameter (3d). The residual stage of pull-out specimens still exhibited a high-stress level in the case of splitting failure owing to the fiber bridging effect of UHPFRC. Finally, a bond strength prediction model related to anchorage length, cover thickness, and the geometric ratio of CFRP bar surface was proposed.