Three industrial anode butts, with and without recycled butt material, were investigated in this study. Non-destructive x-ray tomography (x-ray CT) was used to enumerate the spatial distribution of density and porosity in the sample. Apparent and absolute densities, and air/CO2 reactivities were measured as a function of the distance from the airburn side. The results from the x-ray CT and the physical properties measurement, when compared, showed a decrease in apparent density and an increase in absolute density and porosity from the center of the core to the surfaces. This work indicated that the main factors that derived the change in air and CO2 reactivities of the anodes along the electrolytic surface to the airburn surface were the concentration of the inorganic contents and the porosity of the carbon material.