Optimizing flexural cracking process of ultra-high performance concrete via incorporating microscale steel wires

Optimizing flexural cracking process is the premise to develop ultra-high performance concrete (UHPC) with high flexural strength and toughness as well as multiple cracking characteristics, and it was achieved by improving cracking resistance of matrix and forming complete multiscale fiber reinforcing network simultaneously in this study. Owing to their micro diameter and excellent elastic modulus as well as good thermal conductivity, microscale stainless steel wires at 0.2 vol% can already improve structure compactness of UHPC with straight mesoscale steel fibers by filling effect and reduce the microcracks caused by shrinkage and initial flexural load, thus enhancing the flexural-tensile modulus and initial macro cracking stress of composites. Meanwhile, the wires are conducive to increase fibers' distribution and orientation with their high flexibility and form widely distributed network together with fibers to hinder cracks propagation, resulting in the occurrence of multiple cracking flexural failure and improved flexural properties of UHPC with less than 2.0 vol% fibers. Therefore, the enhancement of interfacial bond strength and first cracking energy via incorporating wires provide an approach for fabricating high ductile UHPC by maximizing the synergistic effectiveness of both wires and fibers.