Effect of Basalt Fibers on The Flexural Behavior of Beams Reinforced With BFRP Bars

Abstract

Over the last few decades, construction materials have gone through many developments aimed at improving their structural and operational properties. The implementation of fiber-reinforced polymer (FRP) bars as a replacement for conventional teel reinforcement in reinforced concrete structures has gained significant acceptance in the construction field. Basalt Fiber-Reinforced Polymer (BFRP) bars are a new type of FRP reinforcement material that was recently introduced to the construction industry. The main shortcoming associated with the use of the BFRP bars in concrete beams is related to the brittle behavior of these beams. This research investigates, experimentally and analytically, the effects of using different types of fibers within the concrete mix on the flexural behavior of BFRP-reinforced concrete beams. The experimental program consisted of material evaluation and flexural testing. A total of 12 beams were prepared and cast using plain, basalt fiber, and synthetic fiber-reinforced concrete with a 400MPa target compressive strength. Flexural testing was conducted on each of the BFRP-FRC beams using a four-point loading test. Results showed a noticeable improvement in the flexural capacities of these beams due to the delay in concrete failure strain (beyond 0.003) at the compression zone, which helped the BFRP bars to attain a higher ultimate strength. Results also indicated that introducing fibers to the concrete increased curvature ductility. Furthermore, the flexural capacity of the section increased by 12% for the basalt fibers RC beams compared to 19% for specimen with synthetic fibers. The opening of cracks and their deep propagation was effectively restrained by the bridging effect of the fibers, which keeps the crack widths lower than the allowable limit of 0.7 mm at the service stage. In addition, the applicability of ACI 440-1R-06 recommendations was assessed using the results of plain concrete specimen and extended to cover fiber-reinforced concrete beams. The experimental results showed good agreement with the analytical ones obtained using ACI equations in terms of flexural capacity, crack spacing, crack widths and mid-span deflection.