Protective polyurea coatings for enhanced blast survivability of concrete

Abstract

Polyurea is a synthetic high-strength elastomeric coating that can be sprayed over existing structures for protection against weathering effects. In view of the fast kinetics associated with the isocyanate-amine reaction, practical processing of polyurea is performed using spray coating technique. In this paper, we report the effect of varying the type and amount of chain extender on the mechanical properties of spray coated polyurea. An optimal ratio of aromatic: aliphatic chain extender was found to result in optimal H-bonding, which in turn reflected in terms of improved mechanical properties of the coating. In this paper, the efficacy of polyurea towards improving the performance of the substrate towards shock and ballistic loading is demonstrated. Polyurea coated concrete tiles were subjected to controlled blast loadings, and an attempt was made to understand the mechanism responsible for the improved blast survivability. Unreinforced concrete tiles underwent extensive fragmentation at peak pressures <50 psi, while polyurea coated tiles could withstand much higher peak pressures. The extent of mitigation increased with the coating thickness and composites with 6 mm polyurea could withstand substantially higher pressures. Upon further loading, polyurea-concrete debonding was evidenced, however the membrane arrested the fragments formed. Dynamic mechanical studies revealed that polyurea remains as an elastomer under the frequency range associated with the shock tube testing and behaves as a catcher system for the fragments formed due to blast loading.