Tailor-made steel fiber reinforced ultra high performance concrete - single fiber pull-out, bending capacity and fracture toughness

Micro steel fibers used in UHPC account for a significant portion of the overall cost and the environmental footprint of the material. It is therefore aimed to replace these fibers by bond optimized macro steel fibers with diameters between 0.3 to 0.5 mm. Single fiber pull-out and beam tests were performed to characterize fiber bonding and fiber i.e. crack bridging efficiency and model the resulting composite behavior. Different fiber diameters, surface roughness, fiber inclinations and concrete compositions were considered. This contribution presents the results of one concrete composition in detail and summarizes the main findings of the overall study. Furthermore, the derivation of input parameters for modelling bending beam behavior is demonstrated.