Effect of basalt microfibers on the shear response of short concrete beams reinforced with BFRP bars

This paper experientially investigates the effect of adding basalt microfibers to the concrete mix on the shear response of short beams reinforced longitudinally with Basalt Fiber Reinforced Polymer (BFRP) bars. The main objective is to study the feasibility of enhancing the shear capacity and cracking response of BFRP-RC deep beams due to the presence of microfibers. A total of eight beams with a length of 2000 mm and a crosssection of 150 mm x 260 mm each were cast for this purpose. Six beams were cast using basalt microfibers, one beam was cast using synthetic fibers and one was cast using plain concrete. The test parameters included shear span-to-depth ratio, longitudinal reinforcement ratio, concrete compressive strength, and the type of microfibers used in the concrete mix. Experimental results showed that the presence of basalt microfibers and synthetic fibers have a significant influence in enhancing the overall stiffness, toughness, and ultimate shear strength of the tested beams. The presence of basalt microfibers resulted in an increase in the maximum load carrying capacity by 42%. The experimental results are then compared with the strut-and-tie model (STM) predictions according to ACI-318-14. The constructed STM model resulted in a conservative prediction of the ultimate shear strength of tested beams.