Glass Fiber-Reinforced Polymer Bars under Sustained Load and Alkaline Conditions

This paper presents the results of creep rupture tests conducted on two different sizes of glass fiber-reinforced polymer (GFRP) bars from two different manufacturers under high alkaline conditions at room temperature (approximately 23 and 60 degrees C [73.4 and 140 degrees F]). Regular tensile tests were also conducted on the bars at the two temperatures to provide insight into the effects of high temperature on their long-term performance. The results show that the larger bar performed slightly better at room temperature but significantly better at the elevated temperature. The larger-sized bars also lost less tensile strength at the elevated temperature. It was observed that temperature had a greater effect on the long-term performance of GFRP bars than alkalinity. The current design code limits on the allowable stresses were evaluated against the test results and found to be overly conservative.