Self-Cleaning Material Test On Surface Of Steel Structural Bridge

Steel bridge has the advantages of long-span ability,light weight,high stiffness,good seismic performance and short construction period.Thus it has been widely used in highway and railway bridge constructions.However,with the deterioration of environmental pollution,various pollutants such as solid and liquid dust and particles in the atmosphere accumulate gradually on the surface of steel bridges,which has a nonnegligible effect on the aesthetics of bridges.Besides,these pollutants often adsorb corrosive media in the environment,aggravating the corrosion situation and affecting the safety of the bridges in operation period.In this paper,based on the basic superhydrophobicity theories and the principles of practicability and economy,a series of preparation of hydrophobic self-cleaning surface on Q345 steel for bridge are proposed.The surface morphology,wettability,transmittance,self-cleaning performance,mechanical property and weather resistance of the coatings were mainly investigated.The durability of the coatings under the practical condition was verified using a long-term outdoor exposure test.The main work and conclusions of this paper are as follows:?1?The preparation methods,durabilities and applications of superhydrophobic self-cleaning surface in bridges were comprehensively reviewed.The development trend of superhydrophobic self-cleaning surface was summarized.The theoretical basis of superhydrophobic self-cleaning surface and its self-cleaning principle were elaborated.On this basis,the test method of hydrophobic self-cleaning materials on Q345 steel substrate for bridge was designed.?2?Three kinds of self-cleaning surface preparation and performance tests were implemented:?1?Superhydrophobic self-cleaning surface with low water adhesion was prepared on Q345 steel substrate by spraying the uniform dispersions formed by mechanical blending of R972?hydrophobic SiO₂ nanoparticles?and neutral silicone structural sealant.The molecular structure and composition of superhydrophobic coatings were analyzed by FTIR and EDS.The effects of raw material dosage on the surface microstructure,hydrophobicity,roughness,transmittance and adhesion of the superhydrophobic coatings were investigated by SEM,contact angle measurement,AFM,UV-VIS and adhesion tester,based on which the optimum raw material ratio of the superhydrophobic coatings was determined,and the durability of the superhydrophobic coatings under this ratio was investigated.The results showed that the superhydrophobic coatings had a good weather resistance of acid,water,salt,high temperature and UV radiation,but had a poor resistance to strong alkali and abrasion.?2?Modified polysiloxane hydrophobic self-cleaning surface was prepared on Q345 steel substrate using spraying method.The surface microstructure,hydrophobicity and transmittance of the coating were characterized by SEM,contact angle measurement and UV-VIS.The mechanical properties of the coatings were studied.The elastic modulus,hardness and adhesion strength of the coatings were measured by nanoindentation and micro-scratch testers,respectively.Weather resistance test of the coatings was carried out.The results showed that the coatings had good thermal stability,water resistance and salt resistance,but it was easy to fail in strong acid and alkali environment,and exhibited yellowing under long-term UV radiation.?3?R972/polysiloxane composite superhydrophobic self-cleaning surface was prepared on Q345 steel substrate using dipping and spraying methods.The effect of R972 content on the performance of the coatings was analyzed by the characterization and test method similar to scheme?1?and the wear resistance of the coatings was mainly investigated.The coatings had excellent superhydrophobicity,transparency,adhesion,wear resistance and weather resistance when a moderate amount of R972 was added.?3?In order to investigate the practical level of R972/silicone sealant composite coatings?sample 1?,modified polysiloxane coatings?sample 2?,and R972/polysiloxane?sample 3?composite coatings,outdoor tests of these three kinds of samples were carried out.The variation of wettability with exposure time of the samples was tested and analyzed.The effects of exposure time on the fouling resistance and surface contamination level of the samples were counted and analyzed.The self-cleaning effect of the samples placed outdoors for 90 days was tested.The results showed that the outdoor performance of these samples was sample 3>1>2.