Life Prediction And Sensitivity Analysis Of Concrete Structures Under Chlorine Erosion

Chlorine ion erosion is one of the major factors that shortens the service life-span of concrete structure under marine environment. Predictions on the life-span of concrete structure exposing to chloride have always been a major focus both at home and abroad. The invasion of chloride into concrete leads to the corrosion of steel bar, which would reduce its bearing capacity and shorten its service life-span. Since reform and opening up, many ports and piers have been exposed to marine environment for as long as 20 years. This research would be of great importance to the proper evaluation of the current conditions of ports under marine environment.Based on the properties of chloride penetration into concrete structure under marine environment, this thesis makes research and analysis from the following aspects:(1) The thickness of three beams reinforced layer is determined in actual engineering .Analysis of the inner corrosion of a concrete beam is made through evaluating the inner electric potential of steel bar corrosion of a certain beam in a real project, the diagram of electric potential shows that corrosion of steel bar is much more serious in the side of the ocean and less serious in the side of the bank.(2) Core sample of concrete is collected from certain parts of a beam or from inside a pipe drain, then this sample will be tested on its chloride concentration and carbonation depth in a laboratory. The experiment shows that the distribution of chloride concentration varies greatly in different parts of the beam. The chloride concentration in a pipe drain is lower. Besides, the carbonation of concrete component in this project is quite limited. The degree of carbonation on the beam is much more serious, while that inside the pipe drain is much less. According to the analysis on the causes of these differences, environmental factor plays an important role in the variation of chloride concentration distribution and carbonation depth inside the concrete.(3) In indoor laboratory, the two groups of concrete were made by two different proportion that were soaked in the block of sodium chloride solution, by time for four months, 8 months. The distribution of chloride ion and chloride diffusion coefficient of the two groups for is analyzed.(4) Based on Fick's second law of life-span prediction, discussion is made on characteristics of probability distribution of correlation parameter. By doing Monte Carlo simulation, type of the probability distribution of initial corrosion time is obtained. Under this distribution type, discussion and analysis is made on the sensitivity of steel bar's initial corrosion time under each parameter. The sensitivity of each parameter from high to low is coefficient of diffusion, the critical, chloride diffusion coefficient,chloride ion concentration of surface,the initial concentration of chloride ion.