Effect of basalt fibers on the flexural behavior of concrete beams reinforced with BFRP bars

This research investigates experimentally the effects of adding different types of fibers to the concrete mixes on the flexural behavior of concrete beams reinforced longitudinally with BFRP bars. The main aim is to study the feasibility of using newly developed basalt microfibers to improve the concrete response. Twelve beams were prepared and cast using plain, basalt fibers, and synthetic fibers-reinforced concrete (FRC) with a 40 MPa target compressive strength. Basalt fibers of two different lengths of 24 mm and 12 mm were considered. Flexural tests were conducted on each of the BFRP-FRC beams using a four-point test setup. The test matrix also included FRC beams reinforced with GFRP bars as well as conventional steel rebar for comparisons. Results showed that introducing basalt fibers to the concrete increased curvature ductility of these beams. A noticeable improvement in the flexural capacities was also recorded due to the delay in concrete failure strain (beyond 0.003) at the compression zone, which helped the BFRP bars attained a higher ultimate strength. The opening of cracks and their deep propagation was effectively restrained by the bridging effect of the basalt fibers, which kept the crack widths lower than the allowable limit of 0.7 mm at service.