This experimental study examines the contribution of steel fibers from cut tie wires, envisioned as an economical reinforcement for self-compacting concrete (SCC), by simultaneously analyzing their behavior in the fresh and hardened states. The study focuses on fiber length, comparing three lengths (2, 3, and 4 cm) at a constant dosage of 0.5% by volume. Methodologically, the evaluation focuses, on the one hand, on the rheological properties of SCC, and, on the other hand, on the mechanical performance after hardening. Scanning electron microscopy (SEM) analysis was also performed to characterize the microstructure and the interfacial transition zone between the steel fibers and the cementitious matrix. The results indicate that the introduction of fibers preserves the flowability of SCC while significantly improving its mechanical performance, particularly in flexure, with a shift in failure mode from brittle behavior to a more ductile, better-controlled post-cracking response. The best-performing mix, SCC reinforced with 4 cm-long fibers, illustrates this improvement, with toughness increasing from 125 N·mm (reference concrete) to 38,281 N·mm and the ultimate flexural load increasing by 57.1% at 28 days. Thus, this reinforcement enhances the SCC’s robustness and adaptability, paving the way for sustainable, economically optimized construction applications, including in demanding structural contexts.
