Study On Protective Performance Of Reinforcement Coating In Coral Concrete

Coral concrete is one of the important building materials for the infrastructure construction of offshore islands and reefs.The external harsh marine environment and the mixing seawater used are easy to cause serious reinforcement corrosion,which is related to the service safety of concrete structures.At present,the mainstream methods of reinforcement corrosion prevention in marine concrete include:selection of corrosion-resistant materials,addition of rebar corrosion inhibitors,surface coating,cathodic protection,electrochemical dechlorination and other reasonable anti-corrosion measures.Among them,coating is widely used because of its easy operation,good protection effect,economy and environmental protection.It is an important research direction in the field of reinforcement corrosion prevention.In this thesis,the corrosion resistance effect of epoxy coated reinforcement in simulated concrete pore solution with different chloride concentration,the protection process and mechanism of reinforcement coating in coral concrete under power on acceleration conditions and dry wet cycle system are studied,and the protection model of coral concrete coated reinforcement is established based on COMSOL.The main research contents are as follows:Firstly,the polarization curves and electrochemical impedance spectrum of epoxy coated reinforcement in simulated concrete pore solution with different chloride ion concentration(0～0.3mol/L)were tested,the failure process of epoxy coated reinforcement coating in simulated concrete pore solution with different chloride ion concentration and the corrosion process of coated reinforcement are qualitatively analyzed.The results show that the corrosion potential and polarization impedance of coated and bare steel bars decrease with the increase of chloride ion concentration,and the corrosion current increases with the increase of chloride ion concentration;However,under the same chloride concentration,the corrosion potential of coated reinforcement in the failure process is higher,the corrosion current density is small,and the polarization impedance decreases slightly in the chloride concentration range of 0～0.15mol/L,which has a good anti-corrosion effect.Secondly,the semi immersion current accelerated corrosion test of C30 strength coral concrete is carried out,and the protective performance and mechanism of epoxy coating in coral concrete are studied by electrochemical impedance spectroscopy,polarization curve and SEM.The results show that the semi immersion current accelerated corrosion method can better simulate the corrosion of coated reinforcement in marine environment;The actual corrosion rate of coated reinforcement is far lower than the set value;The polarization impedance of coated reinforcement decreases first,then increases,and then continues to decrease with time;The existence of pore defects in epoxy coating at the later stage of corrosion provides convenient channels for chloride ion transmission.Finally,the failure process of epoxy coated reinforcement under dry wet cycle system is studied,and the protection model of coral concrete coated reinforcement is established based on COMSOL to simulate the corrosion process of epoxy resin coating.The results show that the chloride ions diffusion law in coral concrete under dry wet cycle conforms to Fick’s second diffusion law.The free chloride ion concentration C_fincreases with the extension of test time,decreases gradually with the increase of the diffusion depth,and both of them tend to be stable eventually;The reaction in the cathode area of the component is the most active,and the potential and potential difference between the cathode area and anode area increase first and then decrease with time.