Abstract: This study conducts an 840 d exposure experiment of fly ash concrete in natural tidal environment, and measures its water and air permeability coefficients and chloride diffusion coefficients using fly ash contents of 0, 20%, 30%, 40% and 50%. Then, we calculate the age reduction coefficients of the three coefficients and examine their dependency using a gray relative analysis method. Results indicated that all these coefficients decrease with the increasing exposure time or fly ash content and their dependency increases with fly ash content. Besides, a power function can be used to describe the time dependent water or air permeability, and the age reduction coefficient increases with fly ash content.

Key words: natural tidal environment, fly ash concrete, permeability, age reduction coefficient, dependency