Mechanical and fracture properties of ultra high strength concrete reinforced with high volume micro steel fibers

An investigational work was implemented to reveal the effects of high-volume micro-steel fibers (MSF) on the mechanical properties and ductility of Ultra High Performance Fiber Reinforced Concretes (UHPFRCs). The aspect ratio and tensile strength of the MSF used were 37.5 and 2250 MPa, respectively. At water - binder ratios (w/b) of 0.12 and 0.14, two groups of UHPFRCs containing 1%, 1.5%, 2%, 2.5%, 3%, 3.5 and 4% of micro steel fiber by volume and tested for the compressive strength, splitting tensile strength, modulus of elasticity, flexural strength, load-displacement behavior, fracture energy, and characteristic length. The experimental results showed that all mixtures with 4% of MSF demonstrated a compressive strength of greater than 160 MPa, splitting tensile strength higher than 12 MPa, and modulus of elasticity of greater than 43 GPa. On the other hand, the mixes with 4% of MSF exhibited a strain hardening. were achieved with the same range of fiber content and 0.12 w/b,. load- displacement behavior with enhanced ductility and all other fracture parameters well improved significantly.