Comparative performance of normal and ultra-high-performance fibre reinforced concrete slabs to ballistic impact of steel-inset ammunition

Ultra-High-Performance Concrete (UHPC) is a widely researched material with varied Civil and Military applications for resilient infrastructure. Design and assessment of UHPC members against ballistic impact of in-service ammunitions is critical to their application to protective structures. Experimental tests are necessary for performance verification and the numerical tools are required to assist with the design. This paper presents experimental and numerical studies on small-scale UHPC panels reinforced with steel fibres (UHPFRC) subjected to steel-inset projectiles. Benchmark concrete slabs with the same geometric parameters made from normal-strength concrete (NSC) were tested to compare the performance of UHPFRC against NSC. The perforation limit thickness of UHPFRC and NSC slabs against steel-inset bullets were determined. The enhanced impact resistance of UHPFRC compared to NSC in terms of depth of penetration (DOP) as well as crater area is most effectively utilized against repeated impacts which is crucial for protective structures. Finite element (FE) models of the slabs were developed and validated against experimental results. An empirical equation to predict DOP was developed with a dimensional analysis of the data collected through experiments and numerical results. The equation can reliably predict the DOP of a UHPFRC panel subjected to impact from deformable steel-inset ammunition of 7.62 mm calibre.