Time-dependent similarity and micro-mechanism of chloride diffusivity of fly ash concrete in different environments

Based on the exposure test of fly ash (FA) concrete in different environments, chloride diffusion coefficients and main microstructural parameters measured by mercury intrusion porosimetry and their time-dependent properties were analysed. Then, the effect of FA content on time-dependent chloride diffusivity and microstructural parameters was investigated. Finally, according to similarity theory and Jaccard coefficient, the similarities of instantaneous chloride diffusion coefficient and main microstructural parameters between two environments were discussed. Results show the proportion of pores with size ≥100 nm has the best correlation with chloride diffusivity of concrete. Besides, chloride diffusion coefficients and main microstructural parameters decrease with exposure time. The decreasing rate increases with the increase of FA content. Moreover, in the laboratory environment with high temperature and high salinity, an acceleration effect on chloride diffusion can be observed. Results of similarity analysis indicate that chloride diffusivity and the main microstructural parameters at an exposure time of 320 days in the laboratory environment are the most similar to those on site at an exposure time of 840 days. For concrete with FA content not more than 40%, the Jaccard coefficients of similar criterion parameters related to chloride diffusivity and microstructural parameters are all greater than 0.87.