Flexural behavior of HSFRC with low reinforcement ratios

Two-point loading tests were conducted in order to examine the flexural behavior of high strength steel-fiber reinforced concrete (HSFRC) elements with a minimum amount of reinforcement. Eleven beam specimens were cast and tested. They included high strength concrete (HSC) beams with and without steel fibers, which were given at a constant volumetric ratio of 0.75%, as well as control normal strength concrete (NSC) beams (without fibers). It was found that the addition of fibers to flexural members with a minimum longitudinal reinforcement caused a more brittle behavior compared to the same specimens that did not include fibers. This result suggests that the minimum longitudinal reinforcement ratio in flexural HSFRC members should be higher than in conventionally reinforced members (i.e., without fibers) in order to achieve sufficient ductility. The moment capacities of the beams that were tested were compared to several available theoretical models. For the HSFRC specimens, the predictions according to Lim et al.’s model and to the ACI544 model, which was originally developed for NSC and was adapted here for HSC, were closest to the current experimental results.