Benefits of using glass fiber-reinforced polymer bars in ultra-high-performance fiber-reinforced concrete

To investigate a feasibility of using glass fiber-reinforced polymer (GFRP) bars to structural elements made of ultra-high-performance fiber-reinforced concrete (UHPFRC), numbers of experiments, including restrained shrinkage tests, bond tests, and flexural tests, were carried out for UHPFRC reinforced with GFRP and deformed steel bars. Test results indicated that the use of GFRP bars exhibited much better performance with regard to the restrained shrinkage behaviors, i.e., lower residual tensile stress, degree of restraint, and cracking potential, as compared with that of steel bars. The bond strength of GFRP bars embedded in UHPFRC was approximately 60% lower than that of deformed steel bars, but similar to that of GFRP bars in previous high-strength concretes. Due to its strain-hardening characteristics, the structural UHPFRC beams reinforced with GFRP bars (ρ = 0.53%) satisfied the service crack width criteria of ACI and CSA codes and exhibited higher deformability factors than the lower limit of CSA code. Therefore, the combined use of GFRP bars with UHPFRC can be an effective way to overcome the major drawbacks of conventional concrete structures reinforced with GFRP bars and to reduce the high early-age cracking potential of UHPFRC by restraint of shrinkage