Study On Coating Protection Of Concrete Structures In Marine Environment

Concrete structures are widely used in coastal engineerings,the durability of concrete has become an important concern in marine environment.In this paper,viscoelastic polyurea(hereinafter referred to as polyurea)called T401 and T501-II,two kinds of protective materials as the research object,the conventional properties and aging properties of polyurea T401 and T501-II were studied.And the coating and coating mortar were placed under two conditions: Simulated tide and salt spray.The mechanical properties of the coatings and the changes of the gloss and resistance to chloride ion permeation were studied.The influence of load on the coating mortar is discussed in the Simulated tide and salt spray conditions,the main conclusions are as follows.(1)The basic properties of two kinds of materials were studied,including solid content,curing time,hardness,tensile strength and elongation at break,water absorption.The solid content of polyurea called T401 and T501-II were 95.11% and 94.25%,The gel time was 23.7s and 172 s,surface drying time was 151.7s and 33.3min.Low temperature bending meets specification requirements.The hardness,tensile strength and elongation at break of two kinds of materials were analyzed.The results show that the properties of polyurea T401 is close to elastic and the properties of polyurea T501-II is close to stickiness.The water absorption rate after 72 h was 0.22% and 0.86% respectively,the water absorption rate is much lower than that of uncoated mortar.the coating has excellent properties and lays a good foundation for protection.(2)The performance of the coating after the xenon arc lamp and the tensile load were studied.Study showed that the polyurea called T401 and T501-II,the tensile strength,breaking elongation and gloss decrease,tearing strength,hardness gradually increased and stabilized in the xenon arc lamp aging 1000 h.FTIR spectrum analysis showed that the FTIR trend and peak position of each feature are consistent,but the intensity of individual characteristic peaks decreased,this indicates that a certain degree of chemical bond fracture occurred after the xenon arc lamp had aged,this is consistent with the change of macroscopic mechanical properties.Taking the polyurea called T401 as an example,the effects of tensile load,tensile strength increased after the tensile force,but the elongation of fracture elongation decreases with the increase of elongation and more and more obvious,the elongation increases with the elongation of the elongation.(3)The protective performance of coatings under simulated tidal action was studied,the mechanical properties and hardness changes of two kinds of materials were analyzed,the gloss of the coating and chloride resisting properties under the conditions of dry-wet cycle load-drying and watering cycle were investigated.The results show that the mechanical properties decrease with the increase of corrosion time under the single wetting and drying cycles,the rate of gloss degradation of polyurea T401 is lower than that of polyurea T501-II,the content of chloride ion from high to low is "no coating mortar > polyurea T501-II coating mortar > polyurea T401 coating mortar".ComPared with the single factor,the decrease rate of gloss decreased under the conditions of load-drying and watering cycle,the content of chloride ion and diffusion coefficient increased,and the permeability of chloride ion increased under the action of stress.(4)The protective performance of coating under salt fog was studied,the mechanical properties and hardness changes of two kinds of materials were analyzed,the gloss of the coating,the ability to resist chloride ion penetration and corrosion rebar under the conditions of salt spray and load-salt spray were investigated.Compared with the single factor of wet and dry cycle,in the single factor of salt spray,the mechanical properties of the coating and the rate of decline in gloss increase,the content of chloride ion in the salt spray environment is lower than that under the dry and wet cycle,and the content of chloride ion is from the highest to the lowest,the uncoated morta,the polyurea T501-II coating mortar,the polyurea T401 coating mortar.Under the two factors of salt spray and load,the decrease rate of coating gloss increased and the chloride ion content and diffusion coefficient increased with the single factor of salt spray.Through the stress-salt fog acceleration experiment,with the increase of stress,the chloride ion penetration rate increases,increasing the degree of corrosion of steel bars.