Static and dynamic responses of hybrid fiber reinforced concrete

Recent studies on Hybrid Fiber Reinforced Concrete (HyFRC) have pointed out that it is possible to optimize physical and mechanical properties for specific applications by combining various kinds of fibers (made of different materials and/or geometries) in the same mix. In this study, two different types of hybrid composites with steel and polypropylene macro-fibers as well as polypropylene and carbon micro-fibers were developed. The first one is a composite with macro steel-fibers and micro-polypropylene fibers with a high toughness and low permeability, while the second one is with steel macro-fiber, polypropylene macro-fiber and carbon micro-fiber with a high impact resistance. In the case of the former, flexural tests and pull-out tests on a single fiber were carried out to better understand the micro-mechanical behavior, and an analytical model was employed to correlate and calibrate these tests. For the latter, a comparison between static and dynamic responses permitted to investigate the effect of loading rate on the hybridization and the relative roles of brittle and ductile fibers. Results indicate that HyFRC can truly be engineered with suitable mix designs for various applications.