Stable process of concrete chloride diffusivity and corresponding influencing factors analysis

Abstract

Based on the relationship between apparent and instantaneous chloride diffusion coefficients of concrete, a time dependent model of instantaneous chloride diffusion coefficient is established. By solving the derivative of the time dependent apparent and instantaneous chloride diffusion coefficients, the stable time of apparent and instantaneous chloride diffusion coefficient is obtained, respectively. Besides, field exposure tests in two marine tidal environments with eight concrete mixtures were adopted to verify the calculated stable time of chloride diffusion coefficients, and the effects of water to binder (w/b) ratio, admixture and ambient environment on the time dependency and stable time of two diffusion coefficients have been analyzed. Results indicated that the proposed method for calculating the stable time of chloride diffusion coefficient is simple and applicable. Moreover, after analyzing the corresponding influencing factors on the stable time of diffusion coefficients, it can be concluded that for the same concrete mixture, a higher chloride concentration in the ambient environment will lead to a larger age reduction factor and a longer stable time of chloride diffusion coefficient. Moreover, in the same environment, the stable times of apparent and instantaneous diffusion coefficient both show a linear increase with w/b ratio of ordinary concrete. Admixtures have significant influences on the stable time of chloride diffusion coefficient. For the case concretes with the same w/b ratio, adding basalt fiber (BF) into concrete has the most obvious lengthening effect on the stable time of chloride diffusion coefficient, followed by fly ash (FA) and silica fume (SF).