Study On Corrosion Mechanism And Micro Morphology Of Corrosion Products Of Reinforcement In Coral Aggregate Seawater Concrete

In order to meet the requirements of China's national strategy towards dark blue,in the process of the development of marine resources,the island infrastructure construction is a topic that can not be bypassed.In this paper,the chloride transport in the Coral seawater aggregate concrete?CASC?and the corrosion mechanism of the reinforcement are studied.The main research contents include:?1?Taking the chloride ion erosion of C30CASC as the research object,the CASC chloride ion content at different time nodes was measured in two erosion environments:immersion?SJ?and dry-wet cycle?SG?.It is found that the diffusion law of chloride is in accordance with Fick's second diffusion law,that is,the free chloride concentration?C_f?of SJ and SG increases with the extension of test time,decreases with the increase of diffusion depth,and finally tends to be stable.?2?According to the modified Fick diffusion law,the apparent chloride concentration?C_s?and chloride diffusion coefficient?D?of CASC at different test time are studied.With the increase of test time,C_sand D are in good accordance with the power function relationship.Based on the time-varying model of apparent chloride ion related to CASC and the time-varying model of diffusion coefficient,the transmission of chloride ion simulated by COMSOL finite element software shows that the model can be better applied to CASC.?3?From a macro perspective,according to standard test methods,measure the corrosion rate and weight loss rate of steel bars in CASC at different test times.The test results show that at 30 days,the steel bars in the CASC are corroded.In various environments,the growth rate of the corrosion rate and the weight loss rate of the steel bars are equal.At the same time,the amount of corrosion pits on the steel bar surface,the size and the fixed distribution development model are consistent.From the microcosmic point of view,the diffraction pattern of rust products inside and outside the steel bar was obtained by X-ray diffraction?XRD?,and the proportion of each component was calculated.At the same time,the surface structure of the rust layer was observed and analyzed by scanning electron microscope?SEM?.Combined with the corresponding test environment,the differences of corrosion products in different test environment and different positions are deduced.It is found that there are a lot of?-Fe O?OH?on the surface of steel bar in SJ inner rust layer,which can effectively reduce the dissolution rate of anode iron.The content of C_fin CASC is more in the dry and wet cycle environment,which results in the inner and outer rust layers of SG containing more loose structure of?-Fe O?OH?andFe₂O ₃,which aggravates the corrosion of steel bars.