Reinforcement concrete structures serving in coastal chloride environment will be corroded by chloride ions intruding into the interior of concrete,which will lead to the decrease of bearing capacity of concrete structures.Chloride ion erosion is the main cause of durability damage of concrete structures.Designing and preparing chloride-resistant high performance concrete with low chloride ion diffusion coefficient is an important measure to improve the durability of concrete structures,and accurately testing chloride ion diffusion coefficient of concrete is the key to this technology.At present,RCM is mainly used to test the chloride diffusion coefficient of concrete at home and abroad,and the experimental results are applied to durability design,evaluation and analysis of concrete structures.In this paper,RCM experiments of cement mortar,ordinary concrete,30%fly ash concrete,30%fly ash concrete and 15%fly ash+15%fly ash concrete are carried out.RCM experiments of cement mortar and concrete under different experimental voltage and different electrification time are carried out.RCM experiments under different experimental voltage and different electrification time are analyzed.The standard chloride diffusion coefficient of RCM experiment was defined according to the objective criterion of chloride ion color development depth.A simplified calculation model of chloride dififusion coefficient was established for three factors:experimental voltage,electrification time and color development depth.The modified coefficient of experimental conditions was defined for the intermediate quantity based on the simplified model of chloride diffusion coefficient.The experimental condition correction coefficient standardized the chloride diffusion coefficient measured in RCM experiment,and obtained the standardized chloride diffusion coefficient calculation value.The main contents and conclusions of this paper are as follows:1、Five series of cement-based material specimens,including cement mortar,ordinary concrete,30%fly ash concrete,30%fly ash concrete and 15%fly ash+15%fly ash concrete,were prepared.RCM experiments under different experimental voltage and different electrification time were carried out.The effects of experimental voltage and time on temperature of anode solution,current value,color depth of chloride ion and diffusion coefficient of chloride ion in RCM experiment were analyzed.The experimental results show that the temperature of the anode solution increases with the increase of the electrification time,and the trend of the temperature rise is more obvious with the increase of the experimental voltage.The current value increases with the increase of the electrification time,and the magnitude of the current value increases with the increase of the experimental voltage,and the current value increases sharply when the experimental voltage is 90V.There is a linear relationship between the colour depth and the experimental voltage,and the larger the experimental voltage is,the larger the colour depth of chloride ion is;the linear relationship between the colour depth of chloride ion and the electrical time is linear;the larger the experimental voltage is,the greater the slope of the linear relationship between the colour depth and the electrical time is,and vice versa,the smaller the change of the experimental voltage does not affect the linear relationship between the colour depth and the electrical time.2、The chloride diffusion coefficient is linearly related to the experimental voltage.The larger the experimental voltage is,the larger the chloride difusion coefficient is.Within the range of 10V-90V,the error of the calculated chloride diffusion coefficient is less than 30%.The relationship between chloride diffusion coefficient and the electrical time can be expressed by power function,and the diffusion coefficient at the early stage of electrification varies with the electrification time.The relationship between chloride diffusion coefficient and color depth can be expressed by power function.When the color depth is small,the diffusion coefficient decreases significantly with the increase of color depth,and when the color depth reaches 25 mm or more,the diffusion coefficient reaches a basic stability.3、The experimental voltage has little influence on the calculation results of chloride diffusion coefficient,and the color depth and the time of conduction have significant influence on the calculation results of chloride diffusion coefficient.Through variance analysis,the influence of experimental voltage,color depth and time on the calculation results of chloride diffusion coefficient is as follows:power-on time>color depth>experimental voltage.It is more reasonable to adopt the test method of changing the experimental voltage by controlling the switching-on time than by controlling the switching-on time of the experimental voltage.The optimum results for the experimental parameters of RCM experiment are as follows:the experimental voltage is 10V-90V,and the switching-on time is 20h-50h.4、Based on the objective physical quantity of chloride ion color development depth,the chloride ion diffusion coefficient of 25 mm color development depth in RCM experiment is defined as the standard chloride ion diffusion coefficient,which is proved by probability analysis.Based on the experimental data of cement mortar and ordinary concrete,the chloride ion diffusion coefficient is established by least square method with respect to experimental voltage,electrification time and color development.The three-factor simplified calculation model of depth is simplified and verified based on the experimental data of mineral admixture concrete;the three-factor simplified model of diffusion coefficient is proved to have high fitting accuracy and good prediction effect by significance test and feasibility coefficient analysis;the modified coefficient of experimental conditions is defined by the simplified model of diffusion coefficient as the intermediate quantity,and the actual results show that the three-factor simplified model of diffusion coefficient has high fitting accuracy and good prediction effect.The experimental condition correction coefficient standardized the measured chloride diffusion coefficient of RCM experiment,and obtained the standardized chloride diffusion coefficient calculation value. |