An Experimental Study on the Impact Performance of Ultra-High Performance Concrete (UHPC) Slabs with and without Steel Fibers under Projectile Loading

This study investigates the impact performance of Ultra-High Performance Concrete (UHPC) slabs with and without steel fibers under high-velocity projectile loading. Thirteen concrete slabs, varying in thickness (30 mm, 50 mm, and 70 mm) and fiber content (0%, 1%, 2%, and 3%), were fabricated and tested using live ammunition fired from an AK-47 rifle. The experimental program evaluated the influence of fiber reinforcement and slab thickness on the penetration depth, crater dimensions, and failure modes. The results demonstrated that the UHPC slabs without fibers exhibited brittle failure similar to Normal Concrete (NC), particularly at lower thicknesses. The inclusion of steel fibers significantly improved the impact resistance, with an optimal performance observed at 2% and 3% fiber content. The increased slab thickness also enhanced performance, especially when combined with fiber reinforcement. The findings underscore the synergistic effect of steel fiber content and thickness in mitigating damage and preventing perforation under projectile impact, offering valuable insights for the design of protective concrete infrastructure.