Study On Corrosion Protection Of Fiber/Nano Particle Composite Reinforced Concrete

Reinforced concrete is a commonly used building structure in modern engineering.The durability of concrete cannot be ignored when meeting the requirements of structural bearing capacity.Corrosion of concrete reinforcement is the main factor affecting the durability of concrete.The corrosion of steel bars causes the performance degradation of structural members and affects the bearing capacity of members,which poses a threat to the long-term applicability of the whole structure.The durability of reinforced concrete under chloride environment is a prominent problem in reinforced concrete structures.Chloride ion erosion of concrete will lead to corrosion of steel bars.The volume expansion of steel corrosion will lead to cracking of concrete protective layer and aggravate the failure process of concrete.Therefore,it is necessary to conduct in-depth research on the corrosion protection of reinforced concrete.In this paper,the chloride threshold for the passivation film of steel bar is explored by simulating the pore fluid environment,and the corrosion mechanism of steel bar in concrete structure is revealed.Through nano-reinforcement and fiber reinforcement,the compactness of concrete matrix is improved and its corrosion resistance is enhanced.The main innovative work and achievements are as follows:1)The depassivation behavior of steel bar surface passive film in concrete pore solution with different p H values was studied.The electrochemical characteristics of steel bar working electrode depassivation were tested by open circuit potential,Tafel curve,EIS and M-S curve.The results show that the p H value and Cl^-concentration of the concrete pore solution are important factors affecting the pitting corrosion of the passive film on the surface of the steel bar.The p H value affects the chloride threshold of the passive film,and the higher the p H,the higher the chloride threshold.2)The performance,microstructure and resistance to chloride ion penetration of nano-reinforced concrete matrix were studied,and the development law of performance and microstructure under different factors was discussed.The results show that nano-Si O₂accelerates the hydration of cementitious materials,improves the mechanical properties of concrete matrix,and reduces the porosity of concrete matrix.However,there is an optimal dosage range of 1%～1.5%,and the porosity is low.Because nano-Si O₂ with different particle size gradation can fill the pores of concrete,the concrete structure is more compact;in addition,the volcanic ash effect of silica fume is more conducive to the improvement of concrete performance,thereby improving the resistance to chloride ion penetration of concrete.3)The zinc phosphate modified steel fiber was prepared,and its durability in different corrosive environments was explored.The results showed that the corrosion resistance of zinc phosphate modified steel fiber was improved compared with that before modification.The zinc phosphate in Ca（OH）₂ solution reacted with Ca²⁺to form Ca Zn₂（PO4）₂·2H₂O,and its electrochemical parameters were improved,indicating that the corrosion resistance of the zinc phosphate coating increased in alkaline solution.Cl^-and SO₄^2-accelerate the dissolution of the film.4)The interfacial bonding properties of steel bar-concrete matrix reinforced by different fibers（steel fiber,polypropylene fiber and zinc phosphate modified steel fiber）were studied,and the corrosion failure mechanism of reinforced concrete was analyzed.The results show that the addition of fibers improves the mechanical properties of concrete matrix,and no penetrating cracks appear in the pull-out failure mode.The bonding strength of the steel-matrix interface is significantly improved,and the corrosion resistance is improved.Due to the formation of hydroxyapatite（Ca₅（PO₄）₃（OH））and calcium phosphate（Ca HPO₄·2H₂O）,the corrosion resistance of zinc phosphate modified steel fiber reinforced reinforced concrete is significantly improved.