Concrete Reinforced by Hybrid Mix of Short Fibers under Bending

In the present study, the mechanical behavior of Fiber-Reinforced Concrete (FRC) beams was studied under bending until rupture. Each beam was reinforced with a hybrid mix of short fibers randomly distributed in its volume. Concrete beams with three different fiber combinations were investigated, namely, beams reinforced with (1) a homogeneously distributed mix of short polypropylene fibers (PP) and steel fibers, (2) PP fibers and Alkali Resistant Glass (ARG) fibers, and (3) PP and composite fibers (CF). The amount of short PP fibers was the same in all FRCs. The investigation focused on the fracture mechanisms and the load-bearing capacity of FRC beams with the developing macro cracks. In total, 12 FRC composite prismatic specimens were casted and tested in four-point bending experiments (4PBT). The current load value versus the Crack Mouth Opening Displacement (CMOD) for all FRCs was analyzed. The crack opening relationship and the influence of fibers on the fracture energy and flexural tensile strength were determined. Rupture surfaces of all samples were investigated using an optical microscope.