Abstract: Based on 1160-day exposure tests to ocean tidal environment, three permeability coefficients (water, intrinsic gas and chloride) of ordinary concrete were measured and calculated for different water-cement ratios and different exposure time periods. A unified method for calculating the corresponding stable time of these coefficients was developed, and the influence of water-cement ratio on the stable time was analyzed. Then, we adopted the nuclear magnetic resonance to track the relaxation time and microstructure parameters of concrete, and examined the influence of the ratio on the time dependence of both permeability coefficients and microstructure parameters. Finally, the relationship between the stable times of both was studied. The results show the three permeabilities of ordinary concrete and their stable times increase with the increasing ratio. The decreasing trend of total porosity with exposure time is similar to that of time-dependent permeability coefficients, showing a correlation between the both stable times; the stable time of water permeability has the highest correlation with that of total porosity. And the evolution of contribution porosity (100-1000 nm) is similar to that of total porosity, but the stable time of permeability is more related to it. The instantaneous chloride diffusion coefficient is stable first, followed by water permeability and gas permeability.

Key words: tidal environment, permeability, stable time, microstructure parameters, nuclear magnetic resonance