The Research Of The Effect Of One-way Load,Freezing-Thawing Cyclcs And Curing Age On Chloride Permeability Of Concrete

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'. The research of concrete deterioration due to one-way load and freeze-thaw cycles and reparation of damage with age 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 test 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 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 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 one-way load and freeze-thaw cycles at different ages were measured by electro-migration (RCM) tests. The results indicate that concrete deterioration due to one-way load,freeze-thaw cycles and reparation of damage with age all have influence on chloride permeability. The chloridediffusion coefficient with different one-way load shows a quadratic polynomial function relation,the chloride diffusion coefficient with different freeze-thaw cycles shows a linear function relation, the chloride diffusion coefficient declines with the growth of curing age are subjected to power law function relation.Finally, considering the effect of one-way load,freeze-thaw cycles and standard curing age, made calculation model of concrete cover thickness. Analysing the diffenence between the chloride diffusion coefficients of concrete at every test factor and that after 28 days standard curing age, and the different influence from every factor. Establishing the functional relationship between the chloride diffusion coefficient of concrete and every factor.