Influence of steel fiber size, shape, and strength on the quasi-static properties of ultra-high performance concrete: Experimental investigation and numerical modeling

This investigation focused on identifying the impact of various types of steel fibers on the quasi-static mechanical behavior of ultra-high performance concrete (UHPC) through different laboratory experiments as well as their numerical modeling. UHPC specimens were fabricated with four steel fiber types: ZP305, Nycon type V, OL 10mm, and OL 6mm. Fiber shape and size had little impact on quasi-static properties of UHPC in compression, while they showed significant impact on flexural and tensile properties. The main benefits offered by the smaller fibers occurred prior to reaching the ultimate load carrying capacity. Once the ultimate strength was reached, larger fibers were more effective in bridging larger cracks. Numerical modeling of the presented experiments were performed using the Lattice Discrete Particle Model (LDPM) enriched with fibers effect. LDPM is a meso-scale model simulating concrete at the scale of coarse aggregate pieces, and it has been extensively used for the simulation of concrete mechanical behavior under various loading and environmental conditions. The extension of this model, the so-called LDPM-F, developed for the simulation of fiber-reinforced concrete, is employed in this research to verify and better understand the experimental observations.