| The application of epoxy-coated reinforcement is an important means to improve the durability of concrete structures under harsh environments,which directly affects the safety and service life of the structures.The traditional fused epoxy coated reinforcing steel generally suffers from brittleness and poor weathering resistance,etc.In this regard,our group has developed a water-based epoxy coated reinforcing steel toughened with polyurethane,which has the advantages of low cost,high ductility and environmental protection.In this paper,we conducted accelerated corrosion tests to address the durability of waterborne epoxy-coated reinforced concrete under harsh environments and established a life prediction model based on corrosion current density of reinforcement using a one-dimensional Wiener stochastic process.The main research contents and results are as follows:（1）For the marine environment,artificial seawater was selected to conduct long-term immersion and wet and dry cycle accelerated corrosion tests on coated reinforced concrete specimens,and electrochemical methods were applied to determine the corrosion current density values(Icorr)and impedance spectrum（EIS）changes of coated reinforcing steel under different concrete strengths and protective layer thicknesses to analyze the corrosion resistance of water-based epoxy-coated reinforced concrete in chloride and salt environments.The test results showed that the corrosion current density of bare reinforcement exceeded 0.1μA·cm-2 after 28 d of maintenance,i.e.,the reinforcement was in a non-passivated state.After long-term immersion for 270 d,When the concrete strength is C30,regardless of whether the protective layer thickness is 25 mm or 40 mm,the bare steel bar Icorrhas exceeded 0.5μA·cm-2 reached a moderate corrosion state,while the Icorr of coated steel bars in C30 concrete remained at 0.02μA·cm-2.At the concrete strength of C60,the Icorr of bare reinforcement exceeded 0.2μA·cm-2,while the Icorr of coated reinforcement remained between 10-3μA·cm-2～10-4μA·cm-2.After 40 cycles of wet and dry cycles,in C30concrete with a protective layer thickness of 25 mm,the bare reinforcement Icorr was 2.14μA·cm-2,and the reinforcement was severely corroded,while the water-based epoxy-coated reinforcement Icorr was 0.0622μA·cm-2,and the reinforcement was still in a passivated state;in C60 concrete,EIS impedance mapping showed that the impedance value of waterborne epoxy-coated rebar at|Z|0.01m Hz was three orders of magnitude higher than that of bare rebar at 107Ω·cm2.The results show that the water-based epoxy coating has excellent protection effect on reinforcement in chloride salt attack environment.（2）For saline soil environment,2%Na2SO4+3.5%Na Cl corrosion solution was used to accelerate the corrosion test by baking and dipping cycle.40 cycles later,in C30 concrete with 25 mm protective layer thickness,the Icorr of bare reinforcement exceeded 1μA·cm-2and reached heavy corrosion status,while the Icorr of water-based epoxy coated reinforcement was 0.019μA·cm-2 and that of commercially available In C60 concrete,the Icorr of coated reinforcement was much lower than that of bare reinforcement,indicating that the coating can effectively avoid the corrosion of reinforcement for a long time and enhance the life of reinforced concrete.（3）The corrosion current density of reinforcing steel was selected as the durability degradation quantity,and the degradation process of corrosion current density of reinforcing steel was modeled by using Wiener stochastic process,and the parameter estimation was performed by using the great likelihood method,and the life prediction model based on corrosion current density of reinforced concrete was established.A visual life prediction program was prepared using MATLAB software,which can calculate the service life of coated reinforced concrete under different reliability levels.Taking coated reinforced concrete under artificial seawater long-term immersion environment as an example,the predicted results of Icorr reaching the threshold value of 0.2μA·cm-2 for self-made water-based epoxy-coated reinforced concrete and electrostatic powder epoxy-coated reinforced concrete were 1585 d and 1602 d,respectively,under the condition of C30 concrete and protective layer thickness of 25 mm calculated by the program,while the corrosion current density of bare reinforcement under the same condition up to 60 d was more than 0.2μA·cm-2.The results indicate that the water-based epoxy-coated reinforcement can effectively improve the service life of engineering structures,and the corrosion performance is comparable to that of commercially available electrostatic powder epoxy-coated reinforcement. |
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