Study On Durability Of Seawater Sea-sand Concrete Structure Based On Steel Corrosion

With the determination of the marine strategy in China,the massive development and construction of the island is imperative.This paper mainly studies the corrosion mechanism and corrosion rate of steel bars in concrete poured with seawater and marine aggregates under different marine environments.And the corrosion of steel bars is compared with which in ordinary concrete.This paper mainly studies the macroscopic corrosion of steel bars,electrochemical corrosion and observation and analysis of microscopic corrosion products in seawater and sea-sand concrete specimens and ordinary concrete specimens under different erosion modes.The main contents and conclusions of this study are as follows:(1)The weight loss rate and the corrosion rate of the steel bars in different periods are measured according to the method specified in the standard.It is found that the steel bars in the seawater and sea-sand concrete began to rust within 8 weeks.The weight loss rate of the steel bars increased equal-probability with the rust rate in different environments.The size and number of the pitting on the surface of steel bars follow a fixed distribution model,and there is a certain evolution law in the growth of the number of pits of different sizes.(2)Using electrochemical workstation to measure the polarization curves of steel bars in different periods,and obtain information such as metal corrosion current density and selfcorrosion potential.It is concluded that the trend of self-corrosion potential of steel bars in seawater sea-sand concrete under two erosion modes is almost the same.The unsatisfactory of cathode reduction reaction is the main reason for the slowdown of steel corrosion rate in the later period.(3)The electrochemical impedance behavior of steel and concrete can be obtained by means of the impedance spectrum of steel in different periods.By analyzing and inferring the formation and damage of the passivation film on the surface of steel,it is concluded that chlorides carried by aggregates and water for mixing cause high concentrations of chloride ion solution in the seawater and sea-sand concrete pore solution.Therefore,the passivation film's formation and subsequent development was impacted severely.(4)The surface of rust layer was photographed by the scanning electron microscope(SEM).The rust layer's type,generation time,structural morphology and the influence to the steel can be more accurately determined according to the secondary electronic signal imaging information of the rust product and XRD information.(5)X-ray diffraction method is used to obtain the diffraction pattern of corrosion products of different rust layers of steel bars,and the composition of the product,the structure and shape of the internal molecules of the material are obtained.Combined with the environment of the test piece,it is found that the main intermediate product of steel corrosion is Fe(OH),and it will transform to different oxidation products continually under different conditions.Various rust products will also transform to each other mutually and dynamically as the moisture in the concrete is replenished and lost.