Research Of Electrochemistry Prevention And Cure Of Concrete Structures Eroded By Chloride

Reinforcing bar corrosion is the main cause of concrete structural durability reduction and its work failure,so it is important to know the chloridion distribution of concrete well which will provide significant scientific basis for correct evaluation,forecasting concrete durability,rapid repair and maintenance.Dechloridation by electrochemistry can discharge chlorine salt by invading concrete protection layer without destroying the protection layer to realize rapid rehabilitate of reinforced concrete structure polluted by chlorine salt without destroy and with low cost.Electromigration rusty retarding technology can transfer the rusty retardant agent to the surface of reinforcing bar and at the same time discharge inner chloridion,which acts as double protection for reinforcing bar.Firstly,the essay will explore the relations between the potential value of chloridion transducer and concentration of free chloridion in the concrete through testing potential variation of chloridion transducer in the concrete and its corresponding concentration of free chloridion in the concrete during the same age of hardening.Secondly,chloridion monitoring scheme will be made in the essay according to the chloridion transducer test results.Adopting the electrochemistry dechloridation device,the essay will explore the effect law of residual ion distribution and the electrochemistry dechloridation efficiency under the different factors,such as different electric field effect,different electrolyte solution,different mineral mixture.Moreover,further research on the variations of reinforcing natural potential,corrosion current and concrete electric resistance during the period of electrochemistry dechloridation will be done,through the methods of half element potential,current step input and linear polarization.Due to the rusty retarding effects of rusty retardant agent in the simulate concrete pore solution,two kinds of rusty retardant agents are chosen to research the variation law of reinforcing bars'self-corrosion potential,polarization resistance and alternating current impedance spectrum in the concrete and also to research different water cement ratio and mixtures' effect on the rusty retarding and discharge salt volume during the electromigration rusty retarding test.An artificial neural network model is built based on test data that can predict self-corrosion potential by the kinds of rusty retardant agents,rusty retardant agent concentration,water cement ratio of concrete,the amount of salt and minerals,time factors etc.Finally,observation on the appearance of cement hydration product before and after dechloridation will be held by scanning electric mirror and the test of concrete pore structure will be held by mercury porosimetry to illustrate the electrochemistry dechloridation' s effect on the concrete micromechanism.The research results show:(1)After all concrete samples' reinforcing bar potential are negatively shifted to around-1V during the process of electrochemistry dechloridation,the natural potential remains unchanged.Over times,the reinforcing corrosion current of all samples is increasing continuously,and 14 days later,it becomes stable.The higher is water cement ratio,the faster increases the corrosion current.Mixing fly ash makes the increasing rate of corrosion current faster.Mixing silica fume and slag makes the increasing rate of corrosion current slower and close to the standard concrete.Resistivity of concrete with 28 days age of hardening varies from different degrees of electrochemistry dechloridation.The lower is water cement ratio,the faster increases the concrete resistance.The final resistance of concrete by mixing silica fume and slag is significantly more than standard concrete,and the resistance of concrete by mixing fly ash is close to the standard concrete.(2)The method of electrochemistry dechloridation makes the sodium ions and potassium ions accumulate nearby the steel bar,result in softening the hydration products of hydration product,increase water content,enhance lubricating ability eventually lead to the electrochemical removal of bond strength between steel and concrete after chlorine the reduction of up to 70/%?76%;at the same time,the longer is electrochemical dechlorination time,the higher is electrolyte capacity,and thus the more is coherence loss rate between steel after dechlorination.(3)The water cement ratio and admixtures are important internal factors influencing the electromigration rust effect.Under the experimental conditions,the greater the water cement ratio is,the better electromigration resistance rust treatment effect is;in different salt content of mineral admixtures in concrete,electromigration resistance rust effect varies from high to low.single fly ash>slag>fly ash,slag and silica fume.The electromigration degree is related to tight internal structure rust effect and concrete.Through the comparison of corrosion inhibition migration,electromigration rust retarding effect is prior to natural infiltration.(4)Electrochemical dechlorination makes the morphology and pore structu of cement hydration products at different depth in concrete change.After electrochemical dechlorination,porosity of concrete in reinforced concrete near the area of chlorine treatment and a large hole in loose structure increase,discontinuous connection between hydrate particles and part of hydration products of decomposition;the outer layer of concrete hydration the product is the network-shaped compact structure and pore size becomes smaller;at the same time,the formation of some needle like and granular crystals in the hole,to a certain extent,improve the concrete resistance and durability of external medium permeability...