Fabric Investigation of Natural Sensitive Clay from 3D Nano- and Microtomography Data

Abstract

The three-dimensional (3D) fabric in natural sensitive clay is quantified from a combination of high resolution nano and microtomographies, scanning electron microscopy, and dynamic light scattering. Although the speckle arising from clay particles and the pores they enclose is discerned in the nanotomography data and compare well with scanning electron microscopy (SEM) images on the same clay, the individual platelet-shaped clay particles cannot be segmented for subsequent quantitative analysis. Regardless, a very wide range of particle sizes—0.1–300 μm—was detected using the current state-of-the-art in imaging and postprocessing. The measured aspect ratios range was 2.5±1; hence, the particles identified were not clay platelets but, rather, mechanically weathered particles embedded in the clay matrix. Furthermore, the smaller particle sizes <80 μm presented a consistent 22–23° deviation in orientation from the horizontal plane, whereas the larger fractions had a horizontal orientation. The latter finding agrees well with prior findings on the inclination of the clay minerals using small angle X-ray scattering. Finally, the measured mean particle size of 450 nm determined from the nano data is corroborated by an independent determination of particle sizes using dynamic light scattering.