UHPFRC Resistance to Projectile Impact in Dependence on Fibre Content

Ultra-high-performance fibre-reinforced concrete (UHPFRC) was subjected to projectile impact using in-service bullets. UHPFRC is an advanced cementitious composite with enhanced mechanical properties where high tensile strength and ductility benefit mainly from the disperse fibre reinforcement. Steel micro-fibres used in this study were straight and smooth with a tensile strength of 2800 MPa. The fibre content in the UHPFRC was set as the main test variable in the framework of this study. It was found that an increase in the fibre volume fraction resulted in an increase in both the tensile strength and the energy dissipation capacity. Cylinder compressive strength of the UHPFRC was determined to be 150 MPa. The UHPFRC slabs used as targets against full metal jacket soft lead core (FMJ-SLC) and full metal jacket mild steel core (FMJ-MSC) projectiles were 50 mm and 45 mm thin, respectively. Both projectiles were fired from the semi-automatic rifle. The weight of the projectiles was 8.04 g and muzzle velocity was determined to be 710 m/s. Damage parameters such as depth of penetration, crater diameter, residual velocity, residual penetration potential and debris fragment loss were determined. Based on the experimental observations it was found that the optimal fibre content in the UHPFRC mixture with respect to damage parameters induced by the high-speed projectile impact is about 2% by volume.