Electrochemical Chloride Extraction Based On Conductive Cement Anode In Marine Concrete

Electrochemical Chloride Extraction(ECE)technology is a simple,economical and effective measure for repairing chloride-eroded reinforced concrete structures.It is to apply an external electric field between the reinforcing bar cathode and the external anode to drive chloride ions in concrete to migrate outside.Present,there are a lot of laboratory experiments on ECE technology.However,there is still a big gap between the actual construction applications.The main reason is that the selection of external anodes and construction technologies still face many technical difficulties.To illustration,the use of titanium mesh anodes,stainless steel anodes when the electrolytic cell is laid,the use of hot-sprayed zinc anode anodic corrosion leads to poor electrical performance.Therefore,for the ECE treatment of reinforced concrete corrosion contaminated by chloride salt,the development of new external anode materials and the application of technical research have important scientific guiding significance for promoting the promotion and application of this technology.Under the auspices of the National Natural Science Foundation of China(51378269 and 51420105015)and the Ministry of Railways Research Project(2014G004-F),this paper proposes the topic of ECE based on high-performance carbon fiber conductive cement-based anode materials.The development of carbon fiber conductive cement-based anode materials,the electrochemical efficiency of conductive cement-based materials as anode materials and the two-way electromigration based on conductive cement-based anodes.The main research conclusions are as follows:(1)To prepare the conductive cement-based material using a binder-free carbon fiber with a volume of 0.8%as a conductive phase,and add different amounts of SAP,defoamer and dispersant to measure the electrical resistivity and water content of the conductive cement-based test block.The relationship is that the conductive cement-based material has the best electrical conductivity when the content of the high-performance water-absorbing resin is 2 kg/m~3,and the electrical resistivity can be as low as 70?·cm.(2)Electrochemical dechlorination with a new conductive cement-based material as the anode can reduce the chloride ion content in the concrete.After the end of the energization time,the chloride ions in the concrete will be relocated.However,the amount of relocation is relatively small.The chloride ion content is still much lower than the initial chloride ion content,and the chloride ion will be enriched at the transition zone between the conductive cement-based material and the concrete matrix interface.(3)The electrochemical removal of chlorine by double cathode is better than that of single cathode,and the enrichment effect of interface region is significantly slowed down.The concrete surface and the second cathode with different spacings were set,and the dechlorination effect was observed.It was found that the smaller the spacing,the less obvious the enrichment of the interface region,and the better the chlorine removal effect.When the current density is 2A/m~2,the current is 30d,and the chloride ion concentration near the steel bar can be as low as 0.1%.(4)The two-way ECE treatment can remove the chlorine ion in the concrete,and can also transfer the external cationic agent of the rust inhibitor to the surface of the steel.When triethylenetetramine(TETA)and imidazolinium ammonium salts are used as electromigration rust inhibitors,the repair effect of triethylenetetramine is better.The higher the current density,the faster the chloride ion migration rate and the higher the concentration of the rust inhibitor.Other conditions remain unchanged,and the thinner the thickness of the concrete protective layer,the higher the electrochemical desalination rate.(5)Mineral admixtures have a great influence on theefficiency of ECE treatment in chloride-eroded reinforced concrete structures.The addition of fly ash and mineral powder not only improves the compactness of concrete,but also improves the binding capacity of chloride ions.,reducing the amount of free chloride ions in the ECE process.The type of steel bar has little effect on ECE efficiency.