Time Dependent Degradation Of Carbonation Resistance Of Concrete With Organic Film Coating

Surface organic film coatings on concrete are a simple and effective method to improve the anti-carbonation ability of concrete,and have wide application prospect.This paper choses five typical organic film coatings available in the market,epoxy zinc-rich primer,epoxy cloud iron intermediate paint,polyurethane topcoat?PU?,epoxy resin topcoat?EP?and chlorinated rubber topcoat?CR?to covering on the surface of concrete as the research object,and use UV accelerated aging method and outdoor natural exposure aging method to aging treatment the surface coating of concrete.The influence of organic-film-coating and its aging on carbonation resistance of concrete were systematically studied by accelerated carbonation test.Due to the easy aging properties of the organic film coating,this paper uses nano-SiO₂ to modify it.The carbonation protection and UV aging properties of the modified coating were studied by accelerated carbonation and UV aging test.The protective properties of the modified coating was verified by the coating performance test,and the protective mechanism of the modified coating was analyzed by microcosmic test.Reserching on the carbonation of coated concrete,it has the following findings: In the same coating system thickness,the coating system carbonation protection capacity sort: polyurethane coating system> epoxy resin coating system> chlorinated rubber coating system;The carbonation resistance of coated concrete is not only related to the coating,but also to the water-cement ratio of the primary concrete.The lower the water-cement ratio of concrete,the smaller the contribution of the coating system to the carbonation protection of concrete;The carbonation depth of concrete is decreasing follows the exponential function relationship with the thickness of coating system increase.Reserach on carbonation of coating concrete with coating aging,it has the following findings: In the same coating system thickness,Coating system anti-aging ability sorting: polyurethane system> epoxy resin system> chlorinated rubber system;In the UV aging,with the increase of the amount of ultraviolet radiation,the carbonation capacity of the coating system was S-type curve degradation;In the natural aging,with the increase of natural aging time,the carbonation capacity of the coating system was parabolic degradation;The life prediction method of the coating system under the condition of UV aging was established,and the service life of the coating system under natural conditions was deduced.Microscopic tests show that the aging of the coating is mainly due to the degradation of the coating film,resulting in particulate matter,fine pores and cracks.Reserach on nano-modified coatings,it has the following findings: Nano-SiO₂ can effectively improve the anti-carbonation performance of coated concrete,and the effect of nano-SiO₂ on chlorinated rubber coating is better than epoxy resin and polyurethane.The optimum nano-SiO₂ content of each coating is between 0.4% and 1.2%.When the nanoSiO₂ content exceeds the optimum dosage,the carbonation protection effect of the modified coating is gradually reduced.Nano-SiO₂ can effectively improve the coating Anti-UV aging performance,the best dosage of nano-SiO₂ is between 0.4% and 1.2%.The corrosion resistance and hydrophobicity of the modified coating were significantly improved.The coating film was effectively filled with nano-SiO₂,the pores of the coating were obviously reduced,and after modification by nano-SiO₂,the destruction of the coating film was obviously reduced under ultraviolet light.Reserach on carbonation model of coating concrete,it has the following findings: This paper deduces a general form of the differential equation of concrete carbonation with an organic film coating system.The calculation formula of the equivalent concrete thickness and diffusion coefficient of the coating system is established,and the empirical formula of the equivalent concrete thickness is obtained.Numerical solution of concrete carbonation differential equation by MATLAB programming.The depth of concrete carbonation was predicted by continuous coating.