Sol-gel transition in porous media Interplay of drying and wetting

Silicate gels, obtained via the sol-gel process, are widely used for consolidating decaying stone artworks and monuments. This consolidation involves the formation of a gel phase from a colloidal suspension during the drying process in a porous medium. A fundamental understanding of this process is essential not only to ensure the effectiveness of the consolidation treatment but also for other applications involving the flow and evaporation of complex fluids in porous media.
In this thesis, we present a multiscale study of the dynamics of the sol-gel transition during flow in porous media, employing both experimental and numerical approaches. We investigate the drying of Newtonian and non-Newtonian fluids in model pores and quasi-2D model porous media. Specifically, we study the influence of porous media properties, such as pore size distribution, on gel formation. On the numerical side, we examine how gel formation impacts liquid flow and subsequent evaporation in porous media. These insights are then compared with experiments conducted on real stones, revealing that a heterogeneous distribution of gel develops during drying, which is not suitable for consolidation purposes.
Finally, the last part of the thesis explores the long-term stability of such gels. We demonstrate that stones treated with this type of consolidant, when exposed to water, can develop strong osmotic pressures within the gel, which can lead to swelling, potentially causing damage or destruction to the stone. This work highlights the complexity of drying processes involving non-Newtonian fluids in porous media and underscores the importance of further research into these ubiquitous natural processes.