Brine Drying and Salt Precipitation Dynamics in Porous Media and Its Impact on Hydro-Thermal-Mechanical Properties

Brine drying and salt precipitation significantly influence the hydro-thermal-mechanical (H-T-M) properties of porous media, with critical implications for applications such as geological carbon storage, soil salinization management, and the preservation of heritage structures. These coupled processes are governed by complex interactions among fluid transport, evaporation, salt crystallization, and microstructural evolution. This thesis investigates these interactions by examining brine evaporation and salt precipitation dynamics and evaluating their impacts experimentally. A series of experimental investigations were conducted to explore the dynamics of salt precipitation and its impacts. Microfluidic experiments with controlled pore structures and wettability conditions provided real-time visualization of brine drying and salt crystallization under gas injection and evaporation. Thermal conductivity measurements combined with X-ray computed tomography (CT) examined salt precipitation patterns in sandy soils and their effects on heat transfer. In-situ X-ray CT with digital image correlation (DIC) tracked salt distribution and damage evolution in sandstone under uniaxial compression. The microfluidic tests in radial flow conditions demonstrate that pore structure and wettability govern the spatial distribution of residual brine after gas injection and salt crystal morphology. Heterogeneous porous media trap more brine near injection points, and capillary backflow under hydrophilic conditions sustains evaporation and promotes salt accumulation, significantly reducing permeability. Salt tends to precipitate as bulk crystals within brine clusters or aggregated crystals at air-brine interfaces, with distinct hydraulic impacts. The microfluidic tests focusing on fractured porous systems show that wettability variations influence capillary flow and salt accumulation, transitioning between fracture-dominated and matrix-dominated precipitation regimes. In highly hydrophilic systems, persistent corner films support fracture-dominated precipitation and clogging, while less hydrophilic conditions favor matrix-dominated precipitation. An analytical model links contact angle to film persistence, supersaturation distribution, and salt morphology. Thermal conductivity measurements in sandy soils quantify how salt precipitation alters thermal properties of porous media. Experiments across varying brine contents and salt concentrations show that thermal enhancement more pronounced at lower initial concentrations. X-ray CT imaging confirms that salt cementation enhances particle contact networks and thermal conductivity, whereas pore-filling salt has a limited impact. Finally, we investigate the mechanical consequences of salt crystallization in sandstone under confinement. Using in-situ X-ray CT and a custom loading apparatus, the study observes damage progression in sandstone samples during brine evaporation. Salt-induced stresses cause surface scaling, internal disintegration, swelling, and stress-amplified cracking. Digital volume correlation reveals localized strain fields tied to evolving salt distributions. Together, these findings advance the mechanistic understanding of salt precipitation in geological and geotechnical porous media and its coupled effects on H-T-M properties. The results enhance predictive modeling and inform mitigation strategies for subsurface engineering, environmental management, and geomaterial conservation.