Practical Methods for Measuring the Tortuosity of Porous Materials from Binary or Gray-Tone Tomographic Reconstructions

Two practical methods are proposed to measure the tortuosity of a porous or permeable
material from its tomographic reconstruction. The first method is based on the
direct measurement of the shortest distance between two points in the pores, and the
second is based on the geodesic reconstruction of the pore or permeation space.
Unlike the first method, the second can be directly applied to gray-tone tomograms,
without the need of a segmentation step. The methods are illustrated with an electron
tomogram of clay/plastic nanocomposite, an X-ray microtomogram of sandstone, and a
series of model morphologies consisting of penetrable random spheres. For the latter
series, the measured tortuosities compare very well with those derived independently
from the theoretical effective diffusion coefficients