Mechanical characterization of basalt FRP rebars and long-term strength predictive model

The use of basalt fiber–reinforced polymers (BFRP) in construction applications is relatively new and, although its mechanical performance is expected to be similar to that of glass fiber–reinforced polymer, not many studies have addressed its performance in concrete and mortar environments. This paper examines the degradation of BFRP bars at their product development stage after exposure to accelerated environmental conditions and proposes a methodology to predict their long-term design strength. A total of 132 BFRP specimens comprising two types and seven different diameters were tested in tension after conditioning in pH9 and pH13 solutions at 20, 40, and 60°C for 100; 200; 1,000; and 5,000 h. Based on the results obtained and adopting the durability approach of industry standards for FRP reinforcement in concrete structures, a comprehensive long-term strength predictive model for fiber-reinforced polymer (FRP) bars in multiple environments is proposed and exemplified. The BFRP bars tested as part of the experimental program presented here exhibited a guaranteed strength of around 1,300 MPa, an elastic modulus of 40 GPa, and they are estimated to retain about 72 and 80% of their strength after 100 years exposure to concrete and mortar environment, respectively. The outcome of this study is expected to provide engineers with more confidence in using FRP, and in particular BFRP, for safe and economic RC structures in aggressive environments.