Research On Experiments Of Chloride Diffusion In Concrete Considering The Effects Of Coarse Aggregate

Reinforced concrete structures have been widely used in port,coastal and offshore engineering.However,after several years,the durability of these structures under marine environment has become a very serious problem that we must face when design and maintain coastal engineering structures.Although researchers at home and abroad have conducted a lot of researches on this problem through many years,the research are not comprehensive due to the complexity of the problem.At present,most of the researches do not take the influence of coarse aggregate into consideration when it comes to the problem of chloride ion erosion.The impact of the coarse aggregate volume fraction and maximum size is lack of system research.In the view of concrete mesoscopic structure,there are many differences among the research achievements of the chloride ion diffusion coefficient in the interfacial transition zone.The effect analysis of coarse aggregate volume fraction on the diffusion coefficient in the ITZ is few.This article focuses on the chloride ion erosion process in the first stage of concrete durability.The previous study results of this problem are summarized and research on the chloride ion diffusion coefficient in the concrete and ITZ via experiment means.The finite element model is established to provide basis for the study on chloride ion diffusion process under the concrete mesoscopic structure.The main contents of this article are as follows:1.The steel corrosion mechanism and research achievements of chloride ion transport mechanism are summarized and the assumption of classical chloride ion diffusion model is sorted out.These chloride ion models based on these assumptions are combed,compared and analyzed.To meet the needs of this research,the chloride ion diffusion model of this article is put forward.2.The experiments aimed at the effect of coarse aggregate on chloride ion diffusion are carried out to examine the content of chloride ion in different deep.The chloride ion diffusion coefficient with different coarse aggregate volume fractions and maximum particle size is fitted using Fick's second law.A model that can represent the rules among the diffusion coefficient,coarse aggregate volume fractions and maximum particle size is established.3.From mesoscopic point of view,the different effects of coarse aggregate on chloride ion diffusion are analized by the results of experiments.It contains two effects which are lowering and lifting the diffusion coefficient.It can be concluded that the lifting effect of ITZ on chloride ion diffusion coefficient is obvious.The model that reflects the chloride ion diffusion coefficients of ITZ in different coarse aggregate volume fractions is established by analyzing the experiments data.4.Using Matlab software program to generate two-dimensional random distribution model of coarse aggregate in concrete.This model is put into the thin material transmission module of the finite element software COMSOL to simulate the chloride ion diffusion process in the concrete mesoscopic model.This method is as accurate and can provide convenient for subsequent research on the chloride ion diffusion process in the mesoscopic structure of concrete.