Influence of pore structure characteristics on the gas permeability of concrete

The permeability of concrete is a key factor in determining its durability. Permeability of porous materials in general is determined by pore characteristics (e.g., porosity, pore size distribution, tortuosity, etc.). In this investigation, we attempted to observe the relationship between the pore characteristics and the permeability of concrete. Nuclear magnetic resonance (NMR), mercury intrusion porosimetry (MIP), nitrogen adsorption, and X-ray computed tomography (X-CT) were used to examine the microstructures of three concrete materials labeled C30, C45, and C50. The results show that the combined aperture size distribution curve generated by N2GA and MIP can more accurately depict the distribution of micro to macro pores in the sample than any single method alone. The three-dimensional visualization model reconstructed by X-CT can provide a more intuitive reflection of the distribution of large pores in concrete. The pore ratios measured by NMR and MIP both have satisfactory correlations with gas permeability, but the pore ratio measured by NMR has a stronger correlation with gas permeability. There is a good correlation between gas permeability and the pore ratios contributed by different segments measured by NMR. In addition, the inherent gas permeability coefficient has a slightly stronger correlation with the median pore size than with the critical pore size.