School of Civil and Environmental Engineering
Ph.D. Thesis Defense Announcement
Clay-Rich Geomaterials: Implications for Infrastructure Stability, Critical Mineral Recovery, and Nuclear Waste Isolation
By: Jose Maria Ferdinand Victoria Calaunan
SEB 122
https://gatech.zoom.us/j/95498188644
2026-11-11 1:00 PM EST
Dr. Susan Burns, Dr. Sheng Dai, Dr. Angel Palomino, Dr. Anne-Catherine Dieudonné
Clay minerals are phyllosilicates formed through rock weathering and precipitation. Parent-rock chemistry and drainage conditions influence their layered structures, giving rise to different minerals, including 1:1 kaolinite and 2:1 montmorillonite, illite, and chlorite. Their mineral structure and interactions with water and ions result in multiphysics behavior that spans scales from mineral surfaces to sedimentary layers. Clay platelets develop preferential alignment and form tactoids during burial, yet the tactoid scale remains poorly explored. How do tactoid organization and hydration influence mechanical behavior? Thin bentonite films serve as analogues of organized tactoid assemblies. Microscopy, suction measurements, nuclear magnetic resonance, and mechanical testing of thin films reveal preferentially oriented fabric and hydration-dependent stiffness and tensile capacity. These measurements provide tactoid-scale properties for numerical upscaling simulations. The connection between particle arrangement and mechanics extends to large-strain friction, where platelets and tactoids align within shear zones. A curated database compiled from published studies shows that the residual friction angle generally decreases as liquid limit increases, in agreement with previous studies. However, mineralogy, fines fraction, displacement rate, and extent of shear displacement also affect the large-strain shear response. The broader relationship is conceptualized as an n-dimensional response manifold. Charged clay surfaces retain counterions such as those released from neighboring rock weathering. How are rare earth elements retained in clays? Can they be desorbed and recovered? Experiments reproduce the adsorption history to form dysprosium-bearing kaolin, as confirmed by multiphysics analytical measurements. Subsequently, clay pastes subjected to a voltage gradient show the potential of electrokinetics in mobilizing and replacing previously adsorbed rare earth elements. The external fluid chemistry affects mobilization and may lead to counter-gradient migration. While calcination causes localized booklet opening and destructuring of the octahedral layers, it locks in the high-valence ions and hinders the recovery of rare earth elements. Overall, clay pretreatment and electrolyte chemistry jointly control rare earth element accessibility, mobilization, and collection. Clay surface chemistry, particle-fluid coupling, and particle-particle interaction can be altered under extreme conditions, affecting the properties and performance of the clay mass. In particular, can intense radiation compromise bentonite buffers used in nuclear waste disposal? A comprehensive study examined bentonite specimens exposed to beta and gamma radiation doses ranging from 100 to 2000 kGy. Results show that bentonite largely preserves its surface chemistry, hydration, particle associations, and swelling potential. These findings indicate that bentonite exhibits high radiation resistance under the investigated storage conditions. Together, these studies connect the multiscale organization and multiphysics behavior of clays and provide renewed insights relevant to mechanical stability in engineering design, critical mineral recovery, and nuclear waste isolation.