Evaluation of synchrotron X-ray computerized microtomography for the visualization of transport processes in low-porosity materials

Synchrotron-source X-ray computerized microtomography (CMT) is evaluated as a method to visualize transport processes. We conclude that CMT is adequate for visualization of transport experiments if the right conditions exist. Namely, 1) not much more than one-order-of-magnitude range in concentration data is needed for the study, 2) the pore space in the samples are greater than approximately 2--50 mum, depending on the sample size and system setup; 3) the sample is fine-grained enough so that a representative elemental volume (REV) can be contained by a 2--10 mm diameter sample, and 4) the transport process is slow enough that significant changes do not occur within the 25--50 min (and possibly less in the future) needed to collect data for one three-dimensional image. Absorption edge difference imaging (AEDI) in association with CMT is introduced as a method to enhance pore-space visualization. We successfully imaged the pore space in a low-porosity granodiorite, diorite and fine-grained granite cores and a higher-porosity soil aggregate sample. We found that the pore space important to transport in the core samples was smaller than what we were able to visualize with CMT. We also made rudimentary associations of minerals with pore-space location.