Synergistic effects of steel fibers and steel wires on uniaxial tensile mechanical and self-sensing properties of UHPC

Doping steel fibers (SFs) can greatly improve the tensile mechanical properties of concrete as the SFs form reinforcement networks inside concrete. Meanwhile, steel wires (SWs), due to their high aspect ratio, can form stable conductive networks in concrete at a low content, endowing concrete with excellent electrical and selfsensing properties. The simultaneous use of SFs and SWs is expected to achieve complementary advantages to form synergic double spatial network within the concrete, leading to the development of ultra-high-performance concrete (UHPC) with high tensile mechanical properties as well as excellent electrical and self-sensing properties at a low fiber content. Hence, this study investigated the uniaxial tensile mechanical, electrical resistivity, strain sensitivity/stress sensitivity and self-sensing properties, and self-sensing properties of UHPC with SFs and/ or SWs, as well as proposed empirical correlation to describe the relationship between stress/strain/crack width and electrical signals. The results demonstrated that the hybrid incorporation of SFs and SWs shows a positive synergistic effect. UHPC with hybrid SFs and SWs possesses modified tensile mechanical properties (e.g., strength and deformation capacity) and self-sensing properties compared with single-doped SFs or SWs. The tensile strength and the strain sensitivity/stress sensitivity of UHPC with hybrid SFs and SWs can reach 9.19 MPa and 319.77/7.50%/MPa, respectively. The proposed empirical correlation can accurately describe the relationship between stress/strain/crack width and electrical signals. The findings in this study provide a new pathway to develop UHPC with both excellent mechanical and self-sensing properties for intelligent/smart infrastructure structures.