Static and dynamic tensile behaviors of BFRP bars embedded in seawater sea sand concrete under marine environment

Basalt fiber reinforced polymer (BFRP) bars can be used as an appropriate substitute for steel rebars in marine concrete structures due to their corrosion-free nature and high tensile performance. However, the long-term dynamic properties of BFRP bars in the marine environment are not well known, which is critical for structural safety when subjected to external dynamic loads (e.g., tsunamis and earthquakes). Therefore, this study investigates the static and dynamic tensile behaviors of BFRP bars after exposure to the seawater sea sand concrete (SWSSC) under marine environment. Accelerated corrosion tests were conducted under various exposure periods (60, 90, and 120 days) and temperatures (25, 40, and 55 °C). Both optical stereo microscope (OSM) and scanning electron microscope (SEM) were used to examine the failure patterns of BFRP bars, whereas the degradation mechanisms were investigated by X-ray micro-computed tomography (micro-CT), SEM, and Fourier transform infrared spectroscopy (FTIR). Results show that the tensile properties of BFRP bars are sensitive to strain rate. Both the tensile strength and the elastic modulus of BFRP bars increase with increasing strain rate, but the failure strain drops. The tensile strength and failure strain reduce with increasing exposure temperature and duration, whereas the elastic modulus does not change significantly. Microstructure analysis clearly reveals that failures of BFRP bars occur due to fiber breakage, matrix cracking, and interface debonding. The basalt fibers always exhibit brittle fracture, but the fracture surfaces change from relatively flat to rough when the strain rate increases. Moreover, the deterioration of BFRP bars is caused by resin hydrolysis, fiber-resin interfaces debonding and fiber damage after corrosion. These results can provide some insights to promote the application of BFRP composites in coastal and marine structures.