Study On The Mechanism And Performance Of Silane Coating On Concrete Surface

As one of the most widely used building materials in the engineering field,concrete plays an important role in the modernization of our country.However,the problem of water penetration has seriously affected the durability of concrete structure.Water penetration will bring external harmful ions into reinforced concrete structure,sulfate erosion and chloride ion erosion,which will lead to further cracking and deterioration of concrete structure.The freezing and thawing effect in severe cold environment will make the concrete gradually expand,crack and peel off.Therefore,it is of great significance for improving the durability of concrete structures to select appropriate interventions to reduce or block the water transmission in concrete.At present,there are many methods to reduce the transmission of water in cement-based materials.Among them,silane waterproof coating is widely used to coat the surface of cement-based materials,so as to improve the waterproof performance.However,most of the researches focus on the durability of silane coating to play its waterproof performance.There is little research on the quantitative relationship between the evaluation of coating mass and waterproof effect,and the research on the mechanism of silane coating to play its waterproof effect at the micro level is not enough.Therefore,in this paper,through the use of instrument test and capillary absorption experiment,the mechanism and effect of water-proof performance of silane coating are studied from the micro and macro levels respectively.The main research and results are as follows:（1）The contact angle of cement-based materials increased from below 90°to above90°after silane waterproof coating was applied,which made them hydrophobic.After the coating is combined with cement-based materials,the surface film is formed,the silicon content of the sample surface is increased,the Si-O bond is increased,and the hydrophobic group can be introduced into the cement-based materials to increase its hydrophobicity.The coating is hydrated with Ca（OH）₂ in the cement,forming hydrated calcium silicate,which changes the mineral composition of the cement paste sample,reduces the peak value of Ca（OH）₂ and C₃S,and increases the peak value of SiO₂ and CaCO₃.These changes explain the mechanism of silane coating improving the waterproof performance of cement-based materials from the micro level.（2）The permeability of isobutyl triethoxysilane monomer in cement-based materials conforms to Lucas Washburn equation.Through dyeing,the penetration height of silane monomer in the sample can be obtained,and the linear relationship between penetration height and coating mass is y=105.31653x.Therefore,the penetration height of the coating in cement-based materials can be predicted according to the coating mass value of silane monomer coating.（3）When the coating mass of silane monomer is in a certain range,its waterproof effect will be better with the increase of the coating mass.When the coating mass exceeds a certain value,it has no effect on the improvement of waterproof performance of cement-based materials.Therefore,the coating mass of silane monomer coating for cement-based materials to achieve the best waterproof effect can be obtained.（4）Through the combination of the water content distribution information of uncoated samples obtained by XCT and the reduced water content by coating,it can be equivalent to the thickness of the increased protective layer corresponding to the coating,so as to establish an evaluation system of equivalent thickness of the increased protective layer of concrete by coating different mass silane coating.（5）According to the results of capillary water absorption experiments,the coating of isobutyl triethoxysilane monomer has the best waterproof effect on cement-based materials.