Preparation Of Superhydrophobic Surface Based On SiO₂ Electrokinetic Nanoparticle And Research On Anti-corrosion Of Reinforced Concrete

The reinforced concrete structure plays a crucial role in the field of engineering construction.However,due to the porosity of the structure itself,chloride ions can enter the interior and cause corrosion of the steel,which threatens its durability.It is expected to improve the corrosion resistance of ferroconcrete to chloride ion in two ways:one is to cut off the transmission path of chloride ion by modifying the porous structure of concrete,and the other one is to avoid the contact between chloride ion and rebar by coating the surface of newly-cast reinforced concrete with a stable corrosion-resistant film.In this thesis,based on preparation of positively charged SiO₂-based electrokinetic nanoparticles,a superhydrophobic coating was constructed on the surface of the steel bar.At the same time,the electrokinetic nanoparticles entered into the pore structure of concrete under the electric field and the effect on the corrosion resistance of reinforced concrete structures was studied.Specifically,it includes the following three aspects:?1?Using silica sol,polyaluminum chloride and?-glycidyloxypropyltrimethoxysilane?KH560?as raw materials,with the method of stirring,centrifugation and multiple ultrafiltration,the positively charged,stable SiO₂ composite electrokinetic nanosoles with small and uniform particle size were prepared.When the mass ratio of Al₂O₃/SiO₂ is 1:3,the pH range is 3-4,and the conductivity range is 2-4?S/cm,the prepared composite sol exhibits a positive zeta potential and has the best stability.The particle size of the colloidal particles is small and uniform,thus the controllable preparation of the SiO₂-based composite electro-nanosol is realized.?2?Using Al₂O₃@KH560@SiO₂ with a mass ratio of Al₂O₃/SiO₂ of 1:3,a rough micro-nano structure is constructed on the metal surface by electrochemically assisted deposition technique,and stearic acid with no fluorine,economical and low surface energy is used in the modification to prepare a superhydrophobic coating.The effects of deposition time on the morphology and wettability of the coating were investigated.At the same time,the corrosion resistance of the superhydrophobic coating sample in 3.5 wt.%NaCl solution was studied.The results showed that the sample electrodeposited for 3 min showed the best superhydrophobicity of 153.8°and has good corrosion resistance.The polarization resistance of the superhydrophobic sample increased by more than 11 times.The corrosion current density I_corrorr of the untreated sample was about 3 times that of the superhydrophobic sample,and as the corrosion continued,the ratio of I_corr changes to 5,it means the superhydrophobic film has a long-term protection of the metal matrix.After 120 days of corrosion,contact angle of superhydrophobic coating decreased to 126°indicating the superhydrophobicity lost but hydrophobicity remained.?3?The reinforced concrete structure was optimized by electro-migrating Al₂O₃@KH560@SiO₂ driven by DC electric field,and its influence on the corrosion resistance of reinforced concrete structures was studied.After 14 days of electrokinetic nanoparticle treatment,spherical nanoparticles were visible at a depth of 5-10 mm inside the concrete.The porosity of the concrete structure decreased from 26.2%to 9.9%,and the value of the most probable radius decreased from 96.3 nm to 40.3 nm.After a 9-month dry-wet cycle,the electrochemical results showed that the electrokinetic nanoparticles samples exhibited more positive corrosion potentials,lower corrosion current densities and greater polarization resistance.After corrosion,the surface of the untreated sample steel showed obvious yellow-brown corrosion products,the quality loss was significant,and the corrosion rate was high.The surface of the EN-treated sample was smooth.Only a small amount of pitting yellow spots appeared on the surface of sample of electrokinetic nanoparticles treated for 7days,indicating that the steel bars were basically not corroded.That is,electro-migration Al₂O₃@KH560@SiO₂slowed down the transmission rate of Cl^-,and the content of Cl^-in concrete was greatly reduced,which successfully inhibited the reinforcement in concrete.The electric field-driven Al₂O₃@KH560@SiO₂ electrokinetic nanoparticles can not only suppressed the corrosion of rebar due to chloride ions by coating the surface of rebar with a super-hydrophobic film,but also block the transmission of chloride ions by filling the nano pores of concrete.This lengthened the service life of rienforced concrete which is of great application value to the long-term safe service of civil engineering.