Study On Impermeability Of Concrete Based On Resistivity Method

The permeability of concrete is considered to be the most important index to measure the durability of concrete.The erosive substance in the external environment first penetrates into the interior of concrete components and interacts with the components of concrete,resulting in the deterioration of concrete itself or the corrosion of steel bars.As a new testing method,resistivity method is suitable for testing the impermeability of concrete because of its advantages of fast,nondestructive,high precision and low cost.Therefore,this paper verifies the reliability of resistivity method by studying the correlation between concrete resistivity,permeability coefficient,electric flux and chloride ion migration coefficient,and further explores the influence of mineral admixtures on impermeability index of concrete based on this method.The main contents of this paper are as follows:First of all,based on the purpose of this study,the concrete resistivity test based on the four-electrode method was designed,and the water permeability test methods(permeability coefficient method,steady-state water permeability test method),electric flux method and electric migration method were designed as the control test groups.Based on the design of test control group in this paper,the resistivity,permeability coefficient,electric flux and chloride ion migration coefficient of concrete specimens with single fly ash,single slag powder and double fly ash were measured at 28,56 and 196 days under saturated calcium hydroxide solution curing.Secondly,based on the Nernst-Einstein equation,the correlation analysis was conducted between the test results of concrete resistivity method and the test results of the control group at different curing ages.By calculating the correlation coefficient between the measurement results,the measurement results of resistivity method,water permeability resistance test method(permeability coefficient method,steady state water permeability test method),electric flux method and electric migration method were studied.The influence of different mineral admixtures on resistivity,permeability coefficient,electric flux and chloride ion migration coefficient of concrete specimens was further studied.Finally,the porosity and water absorption of concrete specimens in the control test group were tested by immersion saturation test,and the pore fluids of concrete members with different mineral admixtures were obtained through pore hydraulic extraction test,and the p H value and electrical conductivity of concrete pore fluids were measured.Based on the results of saturation test and p H value test,the impermeability of concrete was studied from the mechanism level.The results of saturation test were compared with p H value and conductivity of pore fluid.Research results show that based on wenner concrete resistivity test results with the results of existing test method in current standard were greater than 0.8,the correlation between the resistivity test results and the static water penetration test method for measuring the coefficient of permeability of concrete results correlation is best,and the migration method of chlorine ion migration coefficient of correlation is the worst.The research results of concrete with different mineral admixtures show that,with the growth of curing age,the resistivity of all test groups increases to varying degrees,and the water permeability coefficient,electric flux and chloride ion migration coefficient also show a general trend of decline.The results of micropore analysis on the impermeability of concrete specimens show that there is no correlation between resistivity and water absorption.The porosity and resistivity of concrete with the same cementing material have a good correlation.Mineral admixtures can reduce the pH value and conductivity of pore solutions.