Study On The Chloride Diffusion Coefficient Of Concrete In Cold Ocean Environment In North

This paper uses the chloride diffusion coefficients of concrete, concrete deterioration due to freeze-thaw cycles and concrete structure durability design and bases on the background of 'The construction of Liao river super major bridge'. Effect of different freeze-thaw cycles on the chloride diffusion coefficient of concrete in northern cold regions and preliminary design method of concrete cover thickness are discussed in this paper.Firstly, the mixture ratios of concrete in six strength grades used in the construction of Liao river super major bridge were designed, and the mechanics properties and durability of the concrete were tested. The experimental results show that in order to improve the ability of marine corrosion resistance of concrete, the chloride permeability resistance of concrete must be improved. Two kinds or three kinds of mineral admixture used in concrete, the water-gelled material ratio lower than 0.38 and the total amount of gelled material no less than 470kg/m3 can reduce the coefficient of chloride diffusion effectively, and improve the ability of marine corrosion resistance of concrete. Two kinds or three kinds of mineral admixture and efficient concrete water-reducer used in concrete to reduce water-binder ratio are the main methods of increasing resistance of concrete on chloride ion and other harmful ions.Secondly, the chloride diffusion coefficient of concrete subjected to different freeze-thaw cycles at different ages were measured by electro-migration (RCM) tests. The results indicate that concrete deterioration due to freeze-thaw cycles and reparation of damage with age have double influence on chloride permeability. The chloride diffusion coefficient and different freeze-thaw cycles showed a linear relationship. The chloride diffusion coefficient declines with the growth of curing age are subjected to exponential relationship.Finally, considering the effect of curing age and freeze-thaw cycles, made calculation model of concrete cover thickness. The comparison shows that the thickness of concrete protective layer calculated using the chloride diffusion coefficient after 28 days standard curing exhibits a higher value than this paper's based on Fick's law. The conclusion is consistent with results of survey in our coastal areas in the last two decades.