Bond characteristics of glass-fibre-reinforced polymer bars in high-strength concrete

Fibre-reinforced polymer bars are rapidly becoming an approved alternative to conventional reinforcing steel bars, especially for severely exposed structures such as bridges. This paper reports on an experimental study on the bond characteristics of both sand-coated and ribbed-surface glass-fibre-reinforced polymer bars embedded in high-strength concrete (HSC). A total of 145 pull-out tests were conducted to examine the effect of varying parameters on the bond characteristics, namely embedment length, bar diameter, surface treatment and concrete cover. In addition, 45 pull-out tests were conducted to investigate the effect of providing headed-end anchorage for the sand-coated bars. The experimental results showed that the sand-coated bars exhibited better bond strength than the ribbed-surface bars, which entailed lower development lengths. Thus, based on the experimental results, expressions for the development length of both sand-coated and ribbed-surface bars embedded in HSC were developed and compared against the results of formulae in available design standards. The comparison revealed that ACI 440-1R-06 produced lower conservative results than CAN/CSA S806-12.