Experimental investigation of polyisocyanate-oxazodone coated square reinforced concrete slab under contact explosions

Reinforced concrete structure can respond in a brittle manner with highly localised damage like concrete spalling, cratering and reinforcement rupturing under contact explosions. High speed fragmentation resulting from concrete spall may cause severe casualties and injuries. It is therefore important to restrained concrete fragments and improve collapse resistance of the slab. The present work is intended to evaluate the effectiveness of coated polyisocyanate-oxazodone (POZD) on the explosive resistant performance of concrete slabs. Contact explosion tests with different TNT charge mass were carried out. Eleven slabs including a control specimens (NRC) and ten coated with different thickness of POZD slabs are tested. By observing the damage level of the slabs, the failure mode and anti-collapse mechanism of the POZD coating were studied and analyzed. It is found that the main local failure modes of POZD-coated reinforced concrete slabs can be divided into: cratering, spalling and coating bulging, slab perforation and the coating large area bulging, punching and coating perforation. The bulging of the POZD coating is mainly due to the detachment of the POZD coating from the base slab and the occurrence of large plastic deformation under the action of the explosion shock wave. Under the strong blast load, the POZD coating can still maintain large deformation and high plasticity. With the increase of the thickness of the POZD coating, the stronger the anti-explosion ability of the slab under the contact explosion, the more the critical damage charge mass of the slab. Based on the test results, empirical equations for the failure and deformation parameters of reinforced concrete slabs are presented, and an empirical formula for the spalling damage coefficient is also given.