Research On The Action Of Transmission Performance And The Critical Concentration Of Chlorine Ion In Concrete Under The Dry-wet Circulation Environment

Splash zone and tide zone are the most two serious reinforced concrete corrosionzones in marine corrosion environment. These durability and failure problems ofreinforced concrete structure have resulted in many potential safety issues and hugeeconomic loss to the society as a whole. Therefore, how to understand its corrosionprocess has become one of the most important studies of all researchers within this area.In this paper, according to the erosion mechanism of marine splash zone and tidezone to reinforced concrete structure, different dry-wet circulation systems were used tostudy the chloride ion transmission performance, discussing the method of monitoringand estimating the critical point of rebar corrosion in the concrete, analyzing the criticalchloride ion concentration of rebar corrosion in concrete, finally a model projectionsexample for durability life of reinforced concrete structure was taken. Through allresearch above, the main objective is to provide more theoretical foundation fordiagnosing the corrosion of rebar in concrete and predicting the durability life ofreinforced concrete structure in the future.Specific contents are as follows:Using titration and chloride ion selective electrode method to test standardconcentration of the NaCl solution, the contrast test results show that the accuracy ofchloride ion selective electrode method is higher than the titration method. By means ofelectrochemical workstation, comprehensive method which include ac impedancespectrum method, linear polarization method and Tafel polarization method etc. was utilized to monitor and estimate the critical point of rebar corrosion in the concrete, thetest results and analysis of data show that it is an effective method to monitor the criticalpoint in time of rebar corrosion in reinforced concrete.According to the results of transmission properties of chlorine ion under differenttime ratio of dry-wet circulation, the depths of convection zone are all around2mmunder different time ratio of dry-wet circulation; chloride ion density Cs,Δxof convectionzone and drying time have certain linear relationship, it is reduced along with theincrease of the drying time, but the reduction is small. Under the action of different timeratio of dry-wet circulation, there is an obvious linear relationship between chloride iondiffusion coefficient and the dry-wet time, which demonstrates that the chloride iondiffusion coefficient will increase when time ratio increases.By studying critical chloride concentration under different time ratio of dry-wetcirculation, dry-wet circulation period and different amount of fly ash, we can concludethat critical chloride concentration under different time ratio of dry-wet circulation andsaturation of specimen at the end of the drying process have obvious linear relationship,it decreases with the increase of specimen saturation at the end of the drying process;critical chloride concentration basically shows a trend of rising with increasing period ofdry-wet cycles; with increasing amount of fly ash, critical chloride concentration firstgoes up and then decreases, which means that although fly ash improves the density ofconcrete, it can also reduce the pH value of concrete pore solution, thus its resistingcapacity for chloride ion penetration increases firstly and declines afterwards with theincrease of dosage of fly ash to the drops.According to the results of model projections for durability life of reinforcedconcrete structure under the action of dry-wet circulation, it is found that the service lifeof concrete structures in the area is generally10~20years, it is extremely difficult tomeet the design requirements, so the necessary durability design and protectivemeasures should be taken.