Evaluation of Porosity and Its Variation in Porous Materials Using Microfocus X-ray Computed Tomography Considering the Partial Volume Effect

Abstract

The physical properties of two-phase materials depend on their internal structure. Therefore, segmentation of the structure of such materials is important in material sciences. In this study, we used a maximum likelihood thresholding method that considered the partial volume effect —i.e., the effect of mixels (mixed pixels)— to calculate the porosities of packed glass beads and the Berea sandstone using microfocus X-ray computed tomography (CT) images. We also examined the effects of scanning conditions on the segmentation results and assessed the porosity of possible packing structures of the glass beads to be segmented to be 33–37% based on histogram data. Moreover, we evaluated the porosity of the Berea sandstone to be 18%.Then, we examined variation in the porosity of biogrouted packing of glass beads using a microfocus X-ray CT scanner and histogram-based image analysis with the same thresholding method. Our results indicated that the ratio of grouted to ungrouted geomaterial porosities was 0.98, whereas the value estimated by measuring changes in the concentration of calcium ions was 0.98–0.99. Thus, we have confirmed that the proposed method can evaluate small changes in porosity with high accuracy.