The Chloride Transport Model And Numerical Simulation Of Concrete With Flag Ash And Slag Under The Effect Of Carbonation

Reinforced concrete act as the main structural material of subway engineering project,Steel corrosion is the most important factor which lead to premature destruction of the structure and structural failure.In order to better match the subway engineering service condi-tions,it is very necessary for us to research the coupling of carbonation-chloride synchronous and accurately build the framework of subway tunnel concrete service performance evolution analysis theory.This will provide the basic theory for the subway structure perfor-mance assessment and remediation service analysis.This article summarize the theoretical derivation of chloride ion transport processes at home and abroad, described the governing equations in numerical model of chloride ion by using Fick’s second law.And through the analysis of concrete carbonization mechanism obt ained the main influence of carbonation reaction of chloride ion erosion processes. And the main research contents are as follows:(1)Through the research of chloride ion transport mechanism, combing the classic transport model and its discontents. Also, analysis of chloride ion erosion model for process, proposed under the coupling effect of chloride ion transport model of considering the chloride binding capacity, time-dependent, many influencing factors, such as humidity and temperature.The effect of factors affecting on diffusion coefficient value expressions and suggestions is gived, taking into account the practical fixed parameters. Test data to verify the reliability of the model.(2)The carbonization coupled salt spray test was conducted to test the concentration distribution rules of free chloride ion and total chloride ion in different erosion-age,then to analysis variation of chloride ion binding. Test results showed that both free chlorine and total chloride ion content in creased with the increasing ages of erosion, but combined with the obvious changes in the proportion of chloride ions.And measure the liquid alkalinity trends in concrete, analyzes the mechanism of coupling effect.(3)Through the study of carbonization mechanism,establish CO2 distribution model(4)changing with the temporal and spatial, obtain in the standard conditions of temporal and spatial distribution of CO2.Through analyzing the process of carbonation reaction, determine two major roles of the carbonation process to chloride ions:chemical and physical effects. Carbonation reaction reduces the pH of the concrete value to release Friedel salt forms of combined chlorine ions.Therefore, the carbonation increases the free chloride ion concentrati on.Inthe carbonation reaction process, CO2 react with C-S-H gels and Ca(OH)2to CaCO3, Which will cause a decrease in voids in the concrete,resulting in physical terms,hinders the proliferation of chloride ion into concrete.(5)Use finite difference method for solving diffusion-reaction equations presented in this paper, and use MATLAB to write procedures.On a proposed carbon chloride coupled model for numerical analysis, study on carbonation reaction of chloride ion concentrations over time as variation.