Study On Mechanical Properties Of Polyurea Coated Concrete Under Impact Load

Concrete structures not only face relatively stable static loads,but also are vulnerable to the threat of accidental impact and explosion loads,such as piers,ports,etc.In addition,the static and dynamic mechanical properties of concrete differ greatly,especially when subjected to dynamic load,the concrete interior rapidly destroys along the interface of mortar aggregate,and forms debris splash,resulting in secondary damage.In order to improve the impact resistance of concrete structure and reduce the degree of damage,it is necessary to protect the key parts.As an excellent protective coating,polyurea elastomer material has the advantages of good physical and chemical properties,convenient construction and fast curing speed.And because of its good adhesion and wrapping ability with concrete and metal substrate,the deformation ability of the structure can be improved to a certain extent.Polyurea can effectively encapsulate structural debris and provide time for safe evacuation of personnel.In this paper,concrete and polyurea coated concrete composite parts are studied,and the dynamic mechanical properties are tested by Hopkinson pressure bar device.Specifically,this paper mainly carries out research from the following aspects:（1）Semi-prepolymer method was used to synthesize elastomer coating materials with different amine chain extender ratios,and the isocyanate index,NCO content and volume ratio of A and B components which affected the coating performance in the synthesis were designed.When the content of NCO was 15.5%and the ratio of amine chain extender（E100/W6200）was 1.6:1,the properties of polyurea coating material were the best.（2）The tensile mechanical properties of three kinds of polyurea coating materials under different strain rates were obtained through quasi-static tensile and dynamic tensile tests.The tests showed that the stress-strain curve of polyurea material had obvious nonlinear and strain rate effect,which provided a basic basis for the analysis of dynamic mechanical properties of the composite.（3）The quasi-static mechanical properties of polyurea coated concrete composites under strain rate of 10^-3s^-1 were tested by microcomputer controlled pressure testing machine,and the influence law of polyurea coated position on the quasi-static compressive strength and failure mode of the composites was analyzed.（4）Using SHPB test device,uniaxial dynamic compression tests at different strain rates were carried out on concrete and polyurea coated concrete composite parts,and the stress-strain relationship of the samples was obtained.The effect of polyurea coating position on dynamic compressive strength,peak strain and energy dissipation was also studied.The characteristics of crack propagation of concrete and composite parts under dynamic compression were observed by high-speed camera,and the effect of polyurea coating position on crack propagation was analyzed.