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A model is established to predict the chloride ion transportation in cement concrete under dry-wet cycles. A formula for calculating the effective diffusion of chloride, which is used to characterize the effect of temperature, the age of concrete, humanity and wind speed on the chloride ion transportation in cement concrete, is proposed. The Fick's law is used to describe the diffusion of chloride. A solution of the diffusion equation is proposed to determine the chloride distribution within an alternate wetting-drying environment area as a function of time and space. The chloride distribution responses are obtained by the finite difference method. Compared with a variety of available test data, there is a reasonable agreement between the model simulations with the experimental data. [ABSTRACT FROM AUTHOR]

In this paper, the sulphate ion migration process of concrete under the coupling action of alternating loading and sulphate corrosion is investigated. Chemical analysis method is used to investigate the sulphate ion migration process of interior concrete. The results show that compared with the static loading and the no loading, the alternating loading can accelerate the sulphate ion migration in the cement concrete which is subjected to sulphate attack. The sulphate ion concentration on the surface of concrete under alternating loading is higher than static loading. With the increase of depth, the difference between the alternating loading and the static loading becomes smaller gradually. When the stress level is greater than 40%, the sulphate ion diffusion is improved obviously. It is also found that on the condition of that water-cement ratio met requirements of the concrete workability, low water-cement ratio will improve the durability of concrete under the coupling action of alternating loading and sulphate corrosion. [ABSTRACT FROM AUTHOR]