3D particle aggregation in consolidated clay systems: Insights from phase-contrast nano-holo-tomography

Journal article, 2026

The microstructural arrangement of clay platelets governs their macroscopic properties, yet 3D observations at the particle scale remain limited. This study employs radiation-based X-ray phase-contrast nano-holo-tomography (nano-CT) to achieve an unprecedented three-dimensional (3D) characterisation of clay particle fabric in saturated kaolin clay samples subjected to one-dimensional (1D) compression. Two samples were prepared with acidic (pH = 4.1) and alkaline (pH = 9.1) pore fluids to examine the influence of electrochemical conditions on the association of clay particle. Phase-contrast nano-CT resolves individual kaolin platelets and their spatial arrangement, enabling quantitative analysis of fabric. Autocorrelation function analyses are used to study the alignment of a macroscopically isotropic, yet locally anisotropic structure for the acidic sample, where the edge-to-face (EF) associations of stacks of particles (i.e., aggregates) dominate. In contrast, the alkaline sample exhibits a highly anisotropic, face-to-face (FF) aligned aggregate configuration. These findings contribute to a deeper understanding of clay fabric characterisation and highlight the potential of non-destructive synchrotron X-ray 3D nano-imaging techniques for advancing clayey materials characterisation.