Ballistic performance of plain, reinforced and pre-stressed concrete slabs under normal impact by an ogival-nosed projectile

The ballistic performance of plain, reinforced and prestressed concrete targets of unconfined compressive strength 48 MPa was studied experimentally against long rod steel projectiles. The square targets (450 mm × 450 mm) of thicknesses 60, 80 and 100 mm were subjected to normal impact by 1 kg ogive nosed hardened steel projectiles of diameter 19 mm and length 450 mm. The reinforcement in the reinforced and prestressed concrete targets was provided with respect to φ8 mm @80 mm c/c both ways. An initial prestress of approximately 4-5 MPa (10% of unconfined compressive strength) was also induced in the prestressed concrete targets with the help of 4 mm diameter steel wires of ultimate tensile strength 1646 MPa. The experiments were carried out at varying incidence velocities, 65 - 220 m/s, and the results thus obtained with respect to extent and vicinity of damage, volume of spalling and scabbing as well as ballistic resistance for three distinct concretes have been compared and discussed. The reinforcement in the concrete has been found to be effective in minimizing the scabbing and spalling of material. The initial prestressing in the concrete, stimulated the globalization effect in the deformation process and thus improved the ballistic performance. The ballistic limit of reinforced concrete target was 11, 16 and 26% higher than plain concrete target for 60, 80 and 100 mm thicknesses respectively. On the other hand, the ballistic limit of prestressed concrete targets was found to be 19, 25 and 35% higher than reinforced concrete, and 32, 45 and 70% higher than plain concrete target for 60, 80 and 100 mm thicknesses respectively.