Creep Rupture Strength of GFRP Bars in Alkaline Concrete Environment Under Elevated Temperature

Abstract

Glass fiber-reinforced polymer (GFRP) bars have emerged as an attractive economic reinforcement due to their corrosion performance in aggressive environmental conditions. The current study aims to investigate the creep rupture strength of GFRP bars exposed to high alkaline water-saturated concrete (pH > 13.0) at an elevated temperature of 60 ℃ under high sustained loads. The test involves a new generation of GFRP bars, including three different products produced by two different manufacturers, while two products were fabricated with different types of resin chemicals. Three sustained load levels were implemented in the study, corresponding to 83%, 80%, and 75% of the guaranteed tensile strength (GTS). Five GFRP bars were tested at each load level. Creep rupture testing in the current study was achieved using an innovative loading frame, which maintained the required sustained load values on the bars. The strain evaluation of each bar was recorded using a data acquisition system, which enabled recording the accurate time to failure of the tested bars. The 100-year creep rupture endurance time was then calculated using the obtained results. The results show that the recommended stress limit under sustained load by the ACI 440.11 and AASHTO is conservative. Additionally, the stress limit stipulated by the current Eurocode 2 draft to account for the long-term tensile strength, the influence of temperature, service life, and environmental attack is significantly over-conservative and leads to uneconomical design.