Effect Of Electrochemical Chlorine Extraction On The Frost Resistance Of Reinforced Concrete

The concrete structures along the coast in the cold region and in the deicing salt environment suffer from the double effects of freezing-thawing cycle and chloride ion erosion,which affect the long service life of concrete structures.Electrochemical chloride extraction can make chloride ions migrate outward under the action of electric current without damaging the concrete structure,so as to effectively reduce the content of chloride ions in the structure and restore the passivation of steel reinforcement,which has a good application prospect and economic value.This article from the perspective of macro and micro,for reinforced concrete specimens after electrochemical chlorine and the effect of electrochemical chloride extraction of concrete antifreeze performance of the research,and based on the damage evolution law of thickness of concrete detailed expounds its performance degradation mechanism,established the corresponding freeze-thaw damage life prediction model,provide a reference for practical engineering application..The electrochemical chloride extraction test and freeze-thaw cycle test of reinforced concrete specimens were carried out to study the effects of extraction time,fly ash content,water reducer and air entrainer on electrochemical chloride extraction efficiency and residual chlorine ion distribution,and the frost resistance of reinforced concrete samples after chloride extraction was simply evaluated.The results showed that the residual free chlorine ions in the concrete after chloride extraction were mostly distributed in the middle part,and the reinforcement and surface layer were less.The longer the electrification time,the higher the efficiency of chlorine extraction,but the rising rate decreased.The addition of fly ash slightly reduces the chlorination efficiency of concrete,but seriously degrades its frost resistance.The addition of water reducing agent reduced the efficiency of chlorine extraction and improved the antifreeze performance after chlorine removal to a certain extent.The effect of adding air entrainer on chlorination efficiency and frost resistance was significant.Was carried out by electrochemical chloride extraction of concrete after freeze-thaw action microscopic test,using X-ray diffraction（XRD）,scanning electron microscope（SEM）,two methods for different freezing and thawing cycles under electrochemical corrosion products of the chloride after reinforced concrete qualitative analysis,the results show that the corrosion products mainly Friedel’s salt and Ettringite,electrochemical chloride extraction of lining concrete influence is bigger,the overall density of surface concrete has the certain promotion;The interface structure of concrete mixed with fly ash has serious deterioration and the proportion of ettringite in hydration products is relatively large.The deterioration of concrete interface structure mixed with water reducer developed more slowly than ordinary group,and the content of Ca（OH）₂in hydration product was less.After 300 freezing-thawing cycles,the interface structure is still intact.The test of freezing-thawing damage evolution law of electrochemical chloride extraction reinforced concrete specimens was carried out,and the development trend of concrete surface damage layer thickness after different freezing-thawing cycles was analyzed.The results showed that the damage layer thickness gradually increased with the number of freezing-thawing cycles.When the damage layer is thicker and the sound velocity is lower,the damage degree is higher.Chlorine salt increases the saturation of concrete pore fluid,reduces the freezing point of solution,and delays the development of early freezing-thawing damage,but the final failure of concrete depends on the time of dechination,the distribution and residual content of chlorine ions,and the combined action of different additives and admixtures.Based on the theory of damage mechanics,the freeze-thaw damage model of reinforced concrete under different factors is established,and the simulation results are in good agreement with the measured results,which can provide reference for the life prediction of reinforced concrete structures under special circumstances.