Computational investigation of pore permeability and connectivity from transmission X-ray microscope images of a cement paste specimen

This study applied the Transmission X-ray Microscope (TXM) characterization techniques and permeability-solver computational program to investigate the transport properties of a microscale cement paste specimen. The TXM techniques allow fast-image acquisition of pore microstructure at a resolution of 30 nm. The microscale cement paste specimen with 0.45 water/cement ratio was specially prepared with a capillary tube. The pore microstructure of the microscale paste specimen was characterized by using the Advanced Photon Source at the Argonne National Lab. The image processing technique was conducted to identify the pore distribution in the captured images. The digital samples with different porosities were generated to compute the transport properties. The burning algorithm was employed to estimate the pore connectivity. The finite difference method with artificial compressibility relaxation algorithm was applied to simulate water transport in capillary pores with Stokes equation. The pore permeability was computed with the calculated average flow velocity using Darcy's Law. The computed permeability results of digital samples were also compared with the predicted values from the Katz-Thompson equation to demonstrate the computational accuracy.