| The transport behavior of chloride ions in concrete is not only related to the physical properties of concrete,but also to the mechanical effects and environmental erosion modes.However,the existing related research has not yet considered this point systematically,especially the theoretical support of the permeation quantitative model.This paper will take the marine chlorine environment as the background,the service state of the concrete structure as the object,from macro and meso point of view study on chloride transport behavior and reveal the permeation mechanism of concrete considering the heterogeneity in order to establish the model of concrete under chloride ion and sustained load,which lay a foundation for the life prediction model of the marine environment concrete structure.1.A simplified model of coarse aggregate distribution is derived through the theory and the experiment.Based on the simplified model of aggregate distribution,the transport model of chloride ions in the concrete considering skins without stress is deduced.The results show that the thickness of the boundary effect layer is related to the minimum particle size of the coarse aggregate,not the maximum coarse aggregate particle size.2.The series-parallel coupling model is proposed to calculate the composite materials(such as concrete from the points of view of mesoscopic)diffusion coefficient and compared with the currently accepted N-phase sphere model,the error is less than 5%,which verify the rationality of the series-parallel coupling model and provide a new method to calculate the composite materials diffusion coefficient.3.Based on the theory of elasticity,an analytical model was developed,and the quantitative relationship between the current porosity of concrete and the diffusion coefficient of the chloride ion,as well as the external equivalent stress,were evaluated.Meanwhile,the influence of various factors on the diffusion coefficient of chloride ion is discussed.The results show that: the chloride diffusion coefficient of concrete at low deformation levels decreases with the increase in compressive stress and increases with the increase in tensile stress.4.Based on the transport model of chloride ions in the concrete considering skins without stress,the transport model of chloride ion in stress concrete considering the influence of surface layer is derived.At the same time,the results show that the stress of the inner layer of concrete is greater than that of the surface layer.5.A model was proposed to predict the chloride penetration profiles of concrete under sustained axial pressure,taking both the time-dependent and the stress-dependent characteristics into account.Meanwhile,the results show that both the apparent chloride diffusion coefficient and the surface chloride concentration values were time and stress dependent with a sudden change threshold value(beyond which,both the surface chloride ion concentration and the apparent chloride diffusion coefficient noticeably change)of approximately 0.3.6.By using the theory of fluid mechanics,considering the influence mechanism of water convection on the chloride ion transport and the transmission of chloride ion in saturated concrete,the model of chloride ion in the concrete under dry-wet cycle and the action of force is derived.The results show that as the initial saturation of concrete decreases,the protruding of the concentration curve of the chloride ion in the surface concrete area is gradually obvious.7.Based on the finite element method and the COMSOL Multiphysics simulation software platform and the previous research findings in this study,the APP of chloride ion transmission in the concrete medium is developed.The APP will transform the scientific programming problem of chloride ion in concrete into a clear and intuitive user interface,and users can directly get relevant results only by input relevant parameters,so as to lay the foundation for life prediction of concrete. |
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