Multistage tensile behavior and toughening mechanism of entangled metallic wire-reinforced ultra-high-performance concrete

Conventional short-steel-fiber-reinforced ultra-high-performance concrete (SSF-UHPC) is limited by premature crack localization, insufficient post-cracking stability, and low tensile ductility, restricting its application in structures requiring high toughness. To overcome these limitations, a novel entangled metallic wire-reinforced ultra-high-performance concrete (EMW-UHPC) was developed in this study by introducing entangled metallic wire material (EMWM) as a continuous reinforcing skeleton. Monotonic and cyclic tensile tests were conducted on EMW-UHPC and SSF-UHPC with different reinforcement volume fractions to investigate their tensile behavior and toughening mechanisms. The results show that EMW-UHPC exhibits a distinctive multistage tensile response characterized by stable strain hardening and sustained post-peak tensile resistance, even at a reinforcement volume fraction of 1.0%. Compared with SSF-UHPC, EMW-UHPC demonstrates significantly improved tensile strength, ductility, and toughness. EMW-UHPC also exhibits a pseudo-ductile failure mode characterized by extensive matrix fragmentation and wire rupture. The superior tensile performance originates from the continuous interpenetrating architecture formed by the EMWM skeleton and UHPC matrix, together with the deformable helical geometry of the metallic wires, which collectively enable sustained stress transfer, distributed cracking, and multiple energy dissipation pathways. This study demonstrates that EMWM provides an effective reinforcement strategy for developing UHPC with high ductility, toughness, and energy absorption capacity.