Time dependency and similarity of decay process of chloride diffusion in concrete under simulated marine tidal environment

Abstract

According to the main climatic factors of natural tidal environment, nine concrete mixtures as same as that in site were designed and exposed in the simulated environment for up to 400 d. The effects of water-cement ratio, admixture and exposure time on chloride concentration and time-varying apparent and instantaneous chloride diffusion coefficient were investigated. Furthermore, the similarity between the time-varying chloride diffusion coefficient of concrete under simulated and natural tidal environments is compared. Results show that in the simulated environment, the free chloride concentration at the same exposure time was significantly higher than that in the natural environment, concrete diffusivity tends to be stable at the first 200 d exposure time, which is advisable to predict the instantaneous diffusion coefficient. However, a general relative error occurs to predict the apparent diffusion coefficient to be predicted by the short-term exposure test. Besides, the age reduction factors of apparent (mapp) and instantaneous (mins) chloride diffusion coefficients have good linear relationships with water-cement ratio under the natural and simulated environments. mapp is less than mins, whether admixtures are adding. A power function can describe the relationship of mapp and mins between the natural and simulated environments.