Non-destructive Tracking And Quantitative Analysis Of Corrosion Process Of Reinforced Concrete

Corrosion of steel is one of the most important factors affecting the durability of concrete.It can cause premature cracking and spalling of concrete,ultimately reducing the effective service life of the building.It is well known that natural corrosion is a long and complicated electrochemical process,and its process is not easy to control.In order to find a way to control well and operate simply,researchers have been exploring for many years.At present,various methods have been developed to simulate the corrosion degradation process of steel in concrete.Among them,the method of applying direct current to steel has been widely concerned and applied for many years.In this study,this method is used to accelerate the corrosion degradation process of steel in concrete,and the advanced X-ray tomography technology is used to track the whole process.Then,by analyzing the changes of corrosion morphology,current efficiency and electrode potential,the effects of different current densities on the accelerated corrosion process are studied.Research results indicate:(1).Based on the help of XCT technology,the corrosion morphology of steel in concrete can be characterized,the corrosion parameters can be calculated and the corrosion periods can be divided.The feasibility and accuracy of the technique applied to the non-destructive quantitative tracking of steel corrosion process have been verified by SEM/EDS and gravimetric method.(2).The corrosion morphology of steel under different current density conditions is quite different.When the current density is higher,the surface of the steel bar occur a relatively uniform corrosion morphology;However,when the current density is lower,the surface of the steel occur the distinct banding-pitting appearance,which is quite similar to the corrosion morphology under natural conditions.(3).During the process of accelerating process,the current efficiency is notconstant,and it is different for different corrosion stages.Regardless of the current density,the change follows the trend of rising first and then decreasing.(4)During the process of accelerating process,the potentials of the anode and cathode are also not constant.Regardless of the current density,the potential change of the anode and cathode follow a trend of decreasing first and then stabilizing.The only difference is that the anode potential changes to a greater extent,while the cathode potential changes less.(5)At high current density,the reaction of oxidizing hydroxide ions into oxygen and water at the anode consumes a large amount of electrons in initial corrosion,resulting in the low current efficiency;In the late stage of rusting(cracking stage),the steel not only undergoes the accelerated corrosion reaction,but also the natural corrosion reaction,resulting in the high current efficiency.At low current density,the natural corrosion reaction begins at the rust expansion stage,which leads to the phenomenon that current efficiency is greater than 100%.And the lower the current density,the more serious the level of natural corrosion occurs.