Study On Anticorrosion Application Of Sherardized Rebar In Marine Concrete Structures

With the constant expansion of marine exploitation,a large number of offshore transportation infrastructures were constructed,such as ports,bridge,highway,tunnel and coastal offshore artificial island etc..These infrastructures were mainly composed of concrete,the corrosion of steel bars is the main reason for the durability reduction of marine concrete structures.As an effective means to improve the corrosion resistance of steel bars,galvanized steel bars are widely used in developed countries such as Europe and America.In this paper,based on the properties of nano powder zinc penetration process is better than hot dip galvanizing process in many respects.We explored the corrosion resistance of sherardized rebar used in concrete structure in marine environment.We studied composition,mechanical properties,corrosion resistance and construction performance of sherardized rebar by means of laboratory test and engineering application.Research shows that the zinc layer is mainly composed of 69.01%Zn and13.77%Fe in mass fraction,the main phase structure is FeZn8.87 phase;sherardizing steel and concrete bond strength is 0.0126 MPa,and it is higher than that of ordinary steel;zinc layer and substrate is metallurgical bonding,and have a good adhesion;Vivtorinox hardness of zinc layer permeability surface and cross-section values were higher than the hardness of steel substrate.When the steel is directly exposed to seawater or marine atmosphere,the corrosion resistance of several reinforced were stainless steel>epoxy coated steel bars（coating without damage）>sherardized rebar>epoxy coated steel bars（coating damage）>ordinary steel bar.In the simulated concrete solution,sherardized rebar not only has excellent corrosion resistance in alkaline medium but also provides cathodic protection for ordinary steel bar.when zinc reinforced mortar layer protection service in the intact,sherardizing layer can provide good protection for steel substrate.In the concrete simulated solution of saturated Ca（OH）₂,the critical chloride concentration of both the ordinary steel bar and sherardized rebar was about 0.12mol/L.The critical pH of ordinary steel bar is less than 9.6,and the value of sherardized rebar is in the range of 10.6¹1.6.The engineering test results of sherardized rebar shows that compared with other corrosion resistant rebars,sherardized rebar has the advantages of good welding performance,zinc layer and substrate has a good adhesion,and high surface hardness.In the construction,sherardized rebar require no special protection during bending,binding and storage process.Moreover,sherardized rebar can be welded by flash butt welding,but it needs to be repaired with zinc rich paint.For evaluation of corrosion state of sherardized rebar in concrete structure,when the half cell potential is-265 mV（vs CSE,the same below）,can be judged in a passive state;when the half cell potential negative to-840 mV,can be judged that the sherardizing layer is activated or in the state of cathode protection for the reinforced bar.