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Time dependent correlation of permeability of fly ash concrete under natural tidal environment

Abstract Based on the long-term exposure test of fly ash concrete under natural tidal environment, the gas permeability coefficient, water permeability coefficient, chloride concentration and microstructure parameters of fly ash concrete were tracked and tested. Relationships between permeability and exposure time as well as fly ash content were analysed. Time dependent models for permeability of concrete were established, and time dependent relationships among water/gas permeability, and chloride diffusivity were discussed. Based on the results of mercury intrusion porosimetry (MIP), the influence of fly ash content on time dependent porosity and pore size distribution (PSD) of concrete were analysed. Results show that fly ash can significantly reduce the porosity, instantaneous chloride diffusion coefficients, water and intrinsic gas permeability coefficients after the same exposure time. A time dependent chloride diffusivity model is established based on the time dependent intrinsic gas permeability coefficients. With the increasing exposure time and fly ash content, the proportions and contributive porosity (100 nm < d < 1000 nm) decrease gradually. Water and intrinsic gas permeability as well as chloride diffusivity of concrete are more closely related to the contributive porosity of large capillary pores (100-1000 nm).