Quantitative Analysis And Design For Durability Of Concrete Structures Under Chloride Environment

In chloride environment, concrete structures are often destroyed by chloride attack.The main reason is that takes durability of concrete structure into account deficiently in the design stage. Hence there is great scientific and application value in the study of quantitative design of concrete materials and structures. This thesis focuses on chloride ingression and diffusion in concrete structures with different geometrical shapes under marine environment, and proposed the methodology of quantitative durability design for concrete structures in marine environment. Based on the results of quantitative design of structural durability, a methodology is developed for quantitative durability design for mix proportion of concrete in chloride environment. And the design method of concrete structure durability quantitatively under the environment of chloride erosion is established.The major conclusions derived from this paper are given as follows:(1)An analytical solution of the governing equation is presented by the method of separation of variables, it can be used to solve the diffusion and distribution of chloride in circular section members exposed to chloride environment.The analytical solutions are derivation by the method of separation of variables for 3D diffusion of circular section members and pipe sections exposed to chloride environment. Then, a analytical solution is derivation by the method of separation of variables for 3D diffusion of non orthogonal diffusion region exposed to chloride environment. The study shows that the proposed analytical method are effective and accurate. It can also be concluded that the anti-chloride permeability and durability of concrete structures can be improved by replacing the components with rectangular cross section by using those with circular or Obtuse angle one. It’s reduce the difficulty and improve the economy in concrete structure mix design and construction period.(2)The control equation of chloride ion diffusion in concrete exposed to chloride environment was modified. And the approximate calculation method and the simplified calculation method of different geometric shapes are presents. Based on the integral method, the analytic solution of one dimensional diffusion of the modified model is derived, and the multi factor analytic solutions of the 2D and 3D diffusion of non orthogonal, circular and non orthogonal are presents by the method of analogy method. Through of ANSYS and interpolation established non orthogonal 2D and 3D chloride ion diffusion simplified approximate solution method, which makes the calculation process more convenient.(3)The strength grade, diffusion coefficient and diffusion decay index were employed in mix design of concrete as the strength and durability indices respectively, a methodology is developed for quantitative durability design for mix proportion of concrete in chloride environment. The concrete prepared by the proposed design method of mix proportion in this paper can meet the requirement of both strength and durability indices, and overcome the limitation of traditional methods.(4) The durability quantitative design of concrete structures exposed to chloride environment should be taken into consideration and the durability of the structure.The concrete structure durability of quantitative design theory based on materials and structural durability is presented for the first time, and the examples are given to demonstrate the accuracy and efficiency of the durability of quantitative design theory. The results show that the geometry of the structure design should pay attention to and the design values of the basic parameters determined by the current design codes do not meet the requirement of service life of concrete structures under marine environment, since the diffusiondecay index is not chosen as design parameter and cannot be determined in current design codes.(5)The method and theory for determining the durability control region of marine concrete structures are established. The integral method is used to derive the diffusion depth formula of chlorine ion in the concrete. Further, the significance of diffusion depth is analyzed, and presents the durability control regional theory and the determine method of control regional. Through a numerical example illustrates the effectiveness of the proposed method, it can improve structure durability design efficiency.(6)The effect of the water/binder ratio, the replacements of fly ash, slag and silica fume on the charge passed and diffusion coefficient are investigated by analyzing the experiment data and those collected from literatures, so that the multi-factor model of charge passed and diffusion coefficient are developed. The statistical analysis of data from literature and experiment demonstrates the satisfying accuracy and applicability of the model. The relationship model between the diffusion coefficient and charge passed is establish by literatures data.