| The deterioration of concrete due to the infiltration of corrosive substances in the environment,and water is the main carrier of many harmful ions,so preventing water penetration into the concrete can greatly improve its durability.To delay the penetration of chloride and sulfate bring by water,coating is commonly employed.Although Organic coating has good waterproof permeability,it’s high cost and weak adhesion,and inorganic coating has good adhesion,but poor water repellency.Organic/inorganic composition coatings can combine the advantages of both.In this study,tetraethoxysilane（TEOS）as inorganic precursor and methyl propyl trimethoxy silane（KH570）are adopted in preparing organic-inorganic composite coating via sol-gel method.Firstly,the process parameters of KH570-TEOS composite sol and its coating performance is discussed.Then the KH570-TEOS composite sol is modified by polydimethylsiloxane（PDMS）,and the properties of KH570-TEOS-PDMS composite sol and its coating are investigated.In addition,the effect of nanofillers on the properties of KH570-TEOS-PDMS composite coating is discussed.The results are as follows:（1）The optimal process parameters of KH570-TEOS composite sol is obtained by discussing the type and dosage of catalyst and KH570/TEOS ratio.The optimal catalyst is HCl,p H is 3.5,KH570/TEOS ratio is 2.0,the composite sol has appropriate viscosity,gel time and film forming property,KH570-TEOS composite coating has a low water absorption rate on the surface of cement mortar specimen,which can significantly improve the impermeability of the specimen.However,hydrophobicity,acid and alkali resistance of coatings are bad.（2）KH570-TEOS composite coating is modified by vinyl terminated polydimethylsiloxane（VT-PDMS）and hydroxy terminated polydimethylsiloxane（PDMS-OH）.VT-PDMS as modifier.Although the viscosity of the composition sol is reduced,the gel time is greatly increased and the film-forming property is bad,the hydrophobicity of the composite coating surface is greatly improved.The contact Angle reaches 139.89° s dosage is 30%.As for PDMS-OH,when the content is 30%,the composite sol has the appropriate viscosity,good stability and film-forming,and its composite coating has good acid corrosion resistance,and changed hydrophilic surface into hydrophobic surface,contact angle is 00.36°,but the water-proof permeability is not significantly improved.（3）KH570-TEOS-PDMS composite coating is doped with nano-SiO2 and octageyl-modified montmorillonite clay（I30P）respectively,to study the protective effect of composite coating with different nanofillers and content on cement mortar specimens under different corrosive environments（seawater corrosion,salt spray corrosion,chloride solution erosion）.The results show that the anti-permeability of the composite coating is improved,but the hydrophobicity of the coating surface is not significantly affected.As nano-SiO2 particles content is 0.5 wt%,the water absorption rate of the composite coating is only 0.37%for 30 d in seawater corrosion environment,and the surface of the composite coating has no change in 600 h neutral salt spray condition.After soaking in 5%NaCl solution for 30 days,the mass growth rate of the specimen is only 0.29%. |
