Prediction Of Multi-points Service Life On Concrete Durability In Chloride Environment

Currently, there are a substantial amount of research on durable life prediction of concrete structure in chlorine corrosion environment at home and abroad, the core problem is how to determine the actual chloride ion diffusion coefficient. The existing methods to determine the diffusion coefficient are long-term natural diffusion test and the electric field to accelerate diffusion test. Method of natural diffusion test is simple, easy to accept, and the apparent diffusion coefficient is closer to the actual situation, and also with high credibility,it can be used to predict the actual life of the concrete after being amended. However, because of a long test cycle and a cumbersome testing process, it is not conducive to practical engineering applications. Electromigration test which is simple, reproducible and take short test time and can get similar results to the natural permeability test,so it has been widely used in practice. However,currently, there are lack of researches on the relationship between result of electric field to accelerate the diffusion test method and method of natural diffusion test. Studies on the relationship between the two, and combine of the results of electric field to accelerate the proliferation and method of natural diffusion test,in this way, its application in engineering has universal and meaningful for projects related to the durability of the design, construction.In response to these problems, the study of this thesis focus on the following five aspects to expand and obtain the relevant research achievement:1. Study the law of the diffusion of chloride ion in concrete through laboratory test.Study the law of the diffusion of chloride ion in concrete in the case of external electric field by the electric field to accelerate the proliferation test and made the in-depth analysis of the affecting factors; Study the law of the diffusion of chloride ion in concrete in the case of natural diffusion by the method of natural diffusion test and made the in-depth analysis of the factors affecting.2. Establish the theoretical relationship between current and chloride ion diffusion coefficient and explore the calculation methods of diffusion coefficient.In order to get the chloride ion diffusion coefficient of different concrete curing period quickly,using the methods of external electric field to accelerate the chloride ion diffusion in concrete. Establish the theoretical relationship between current and chloride ion diffusion coefficient, according to results of test to calculated concrete chloride ion diffusion coefficient using different methods , and discuss on different methods of calculation at the same time.3. Amend the effective diffusion coefficient in the case of natural spread diffusion based on the "step by step method".Chloride ion diffusion coefficient is the key parameters wich affects the durable life of concrete structures. Thesis study the law of the diffusion of chloride ion in concrete in the case of natural diffusion through the method of natural diffusion test and determine effective diffusion coefficient.of different ages by "step by step method".4. Establish the attenuation model of chloride diffusion coefficient phasesOn the basis of nowadays the law of the chloride ion diffusion coefficient of attenuation, the chloride ion diffusion coefficient of attenuation is divided into two stages, namely the conservation of natural attenuation phase and attenuation stages of proliferation, establish the corresponding attenuation model. With combination of results of electric field to accelerate the proliferation of tests and the method of natural diffusion test, determine the relevant parameters through the non-linear fitting method , so as to determine the law of diffusion coefficient attenuation with the changes in the conservation and natural spread of age.5. Propose the improved chloride ion diffusion modelUsing the attenuation model of the chloride ion diffusion coefficient in Fick's second law, to propose the improved chlorine ion diffusion model which is used for life prediction of durability of concrete structures. In the actual project, get the small-age chloride ion diffusion coefficient through the electric field to accelerate the testing, then we can use the improved proliferation models to predict the durability life of concrete structures inactual project.