Recycling Method And Experimental Study Of Chloride-attack Concrete Based On Electrochemical

It is difficult to control the quality of materials used in island building structures,and the service environment is bad.There are serious durability and safety problems.The chloride ion concentration in the dismantled waste concrete is too high to be directly used as raw material for recycled aggregate.Therefore,it is necessary to design a method for removing chlorine and rust during the curing period of recycled concrete by electric migration.This technology is to add a quantitative rust inhibitor and electrochemical treatment according to certain electrochemical parameters when pouring recycled concrete.Using this method,chloride ions originally existing in recycled aggregate are electromigrated to the outside of concrete.At the same time,the rust inhibitor migrates to the vicinity of steel bar to meet the requirement of ensuring the durability of concrete.Conventional electric chlorine removal technology is used to repair the durability of existing structures.If the object of application is recycled concrete during maintenance period,the applicability test of the device should be carried out.The effect of electromigration was evaluated from chloride content distribution and retention rate after electrochemical treatment,and the electrochemical control device was optimized and improved.Distribution of chloride ions in some concrete in the core area of steel bar far from the concrete protective layer will also change.Additional electrodes were installed in this area to replace the steel skeleton as cathode,and electrochemical repair tests were carried out.The results show that the larger the size of the built-in electrode,the better the chlorine removal effect of electromigration.The electrochemical treatment of the built-in electrodes will lead to the retention of chloride ions in the inner side of the reinforcing bar.This effect is worse than that of electrochemical treatment of steel bar as cathode,but the chloride ion proportion in concrete at this position is less than 0.033%.The electrochemical treatment conditions of recycled concrete during curing period are different from the existing structures of conventional treatment methods.The new method requires electrochemical treatment of recycled concrete specimens with built-in electrodes under different combinations of electrochemical parameters.Through this method,the chloride ion content and distribution,the cleanliness of concrete surface and other numerical values are obtained.The optimum electrochemical parameters for the treatment of recycled concrete during curing period were determined as the current density of 0.3A/m~2 intervened on the 7th day of curing period and lasted for 15 days.Under this parameter,the cubic compressive strength of recycled concrete was tested to study the effect of electrochemical treatment on the strength of concrete during curing period.The results show that the compressive strength of concrete with rust inhibitor decreases by 4.02%on average in 28 days.Different recycled aggregates have little effect on chloride ion migration during electrochemical treatment,and the effect is less than 8%.In addition,after electrochemical treatment during curing period,rust inhibitors aggregated around the electrodes in the specimens.The applicability of electric migration and rust resistance treatment for recycled concrete composite slabs during curing period was studied.Comparing the chloride ion content,spatial distribution and the corrosion inhibitor content around steel bars in the composite slabs treated by electric migration rust resistance,the durability protection effect was evaluated.The results of ultimate bearing capacity,crack development law,strain development of steel bar in midspan and deflection change are compared.The results show that the addition of rust inhibitor and the electrochemical treatment during curing period have certain influence on the bond stress of steel bar and concrete of composite slabs.But this kind of influence has little influence on the overall bearing capacity of components.After treatment,chloride ion 0.0500%migrates outward to38.20mm and 37.54mm away from steel bars.The addition of corrosion inhibitor has little effect on the outward migration of chloride ion,and the molar concentration ratio of corrosion inhibitor to chloride ion around steel bar is more than 10.The effect of electrochemical treatment on the durability of recycled concrete during curing period is obvious.