| The service environment of cement-based materials is often complex and changeable.Under the comprehensive action of the accumulation effect of load and the corrosive environment,the durability of the materials will gradually decrease,which is easy to cause various durability problems,which brings great challenges to the reliability of the project.In order to ensure the safety of the engineering structure,fibrous materials or nanomaterials can be mixed with traditional cement-based materials to compound the material structure and make it have higher strength,toughness and durability.In addition,surface protection treatment can also be used to improve the safety and reliability of the structure.Existing research results show that surface coating protection can significantly improve the durability of the structure.However,there is a lack of systematic research on the effect of organic coating protection on the durability of nano-Si O2 and PVA fiber reinforced cementitious composites.In view of this,based on the different water-binder ratio of nano-Si O2 and PVA fiber reinforced cement matrix composites for protection object,and uses the filmforming chlorinated rubber coatings and polyurethane coatings and infiltration of silane impregnation agent for organic coating protective material,has carried on the relevant durability test,to explore the organic coating for nano particles and the influence of the durability of fiber reinforced cement matrix composites.The main research contents and conclusions are as follows:(1)Through the contact angle test and the capillary water absorption test,the surface water contact angle of different coatings and the capillary water absorption rate of the coating-mixed cementitious composites were measured.The results show that the organic coating protection treatment makes the surface of the cementitious composites hydrophilic.It becomes hydrophobic,and the capillary water absorption rate is reduced.The water contact angle of the surface of the test piece after the silane impregnant treatment reaches 107.17°,the hydrophobicity is the strongest,and the capillary water absorption rate is the lowest.(2)The accelerated carbonization test was carried out on the cementitious composites material specimens with different surface protection treatments,and the carbonization depth of the cementitious composites material was obtained.The influence of the type of organic coating and the number of coatings on the anticarbonization performance of the cementitious composites was analyzed,and passed SEM observes the surface of the organic coating and explores the protective mechanism of the organic coating.The results show that the film-forming organic coating can form a dense film on the surface of the cementitious composites to block the passage of carbon dioxide.It can greatly improve the carbonization resistance of cementitious composites.(3)The quick freeze-thaw cycle test was carried out on the specimens of cementitious composites after different surface protection treatment.The influence of organic coating on the frost resistance of cementitious composites was studied based on the index of mass loss and relative dynamic modulus of elasticity.The results showed that the surface organic coating protection treatment on the cementitious composites could improve the frost resistance and reduce the quality of the cementitious composites.The damage form can be improved by increasing the relative dynamic modulus of elasticity and the damage form.The silane impregnator has better protection effect on freeze-thaw failure.(4)The impermeability test of cementitious composites with different surface protection treatment was carried out,and the water permeability height of cementitious composites under different protection conditions was obtained.The data were analyzed.The results show that the surface organic coating protection treatment can improve the impermeability of the materials,and the order of impermeability protection effect from strong to weak is polyurethane coating,chlorinated rubber coating,silane coating The anti permeability protection effect of film-forming coating is stronger than that of permeable silane.(5)RCM tests were carried out on cementitious composites specimens with different surface protection treatments.By comparing the unsteady chloride ion migration coefficients of cementitious composites specimens with different organic coatings,the effects of different types of organic coatings and coating times on the chloride ion penetration resistance of cementitious composites were studied When the water binder ratio is high,the chloride penetration resistance of silane impregnant is better than that of film-forming coating. |
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