Effect of Basalt Microfiber on the Shear Response of RC Short Beams

Abstract

Basalt composites are known for their high strength, lightweight and corrosion-resistance features. Basalt microfibers in fiber reinforced concrete mixes (FRC) can enhance the tensile strength, toughness and ductility as well as the post-cracking behavior of concrete members. This research investigates experimentally and analytically the effects of using basalt microfibers on the shear response of (FRC) short beams reinforced with basalt fiber reinforced polymers bars (BFRP), and compares the results with the strut-and-tie modeling (STM) according to ACI-318-14. The experimental program consists of performing four-point bending tests on eight BFRPFRC short beams that are 2000 mm long with 150 mm x 260 mm cross-section each. The test parameters include shear span-to-depth ratio, reinforcement ratio, concrete compressive strength and the type of microfibers used in the concrete mix. Experimental results showed that the presence of basalt microfibers has a significant influence in enhancing the overall beam stiffness and ultimate shear strength of tested beams. The maximum load carrying capacity increased by 42.1% and 38.2% with addition of basalt and synthetic microfibers, respectively. The capability of basalt microfibers in improving the shear responses of tested beams is attributed to their ability in bridging the micro-cracks by the efficient transfer of the stresses from tips of those cracks to the surrounding concrete. Hence, the propagation of more cracks is eliminated and the failure in the beam is delayed, which results in a greater load-carrying capacity. The constructed STM model as per ACI 318-14 resulted in a conservative prediction of the ultimate shear strength of tested beams compared to the experimental results.