Micro-mesoscale swelling correlations in compacted bentonite upon hydration

Compacted bentonite, a crucial component of engineered barrier systems, displays complicated swelling deformability owing to its unique multiscale structure. This study disentangles the multiscale structure of GMZ bentonite at both micro and meso scales and comprehensively investigates their volumetric responses during hydration processes. An innovative ex-situ X-ray diffraction protocol and a rigorous computational method for cross-scale swelling are developed to capture the volumetric deformation of those decoupled structural units under controlled relative humidity conditions. Moreover, the evolution of fabric structure and water retention during swelling process is meticulously characterized. Upon these findings, a conceptual framework is proposed to integrate the volumetric deformation across scales: larger-scale structure affects smaller-scale behavior via water exchange, while smaller-scale behavior influences larger-scale structure through deformation compatibility. Furthermore, this framework is applied to address the boundary issues in crystalline swelling model by introducing a novel energy balance relationship. These insights shed significant light on the intricate relationship between microscopic and mesoscopic swelling behaviors in bentonite systems.