InterPore2026

Pore-scale mechanisms of granular material consolidation using foam

20 May 2026, 15:35

1h 30m

Poster Presentation (MS05) Physics of multiphase flow in diverse porous media Poster

Speaker

Zahraa Hammoud

Description

Foams are materials composed of gas bubbles separated by thin liquid films, resulting in extremely low density and distinctive mechanical properties. When confined within porous and granular media, their metastable structure is profoundly altered by geometrical constraints imposed by the pore space. Aging mechanisms no longer proceed as in bulk foams, but are instead governed by pore-scale confinement and solid–fluid interactions. In particular, confinement modifies the gas diffusion process which leads to the increase of the mean bubble size.
In the context of granular waste recycling, confined foams provide a low-carbon alternative to conventional binders, with the foamed binder drastically reducing material consumption while maintaining intergranular cohesion. Previous work [1,2] in our group has shown that foams injected into granular packings spontaneously form liquid bridges at grain contacts, as a direct consequence of pore-scale confinement and capillary forces within the granular network. This reveals a unique mechanism by which the binder is deposited selectively at mechanically relevant locations of the porous structure. The size of these liquid bridges—which subsequently become solid bridges upon binder solidification—is governed by the foam microstructure, in particular the bubble size and the liquid volume fraction. Accurately describing how the binder is distributed throughout the pore space, and how this distribution emerges from the interplay between foam properties and confinement, is therefore essential to predict and optimize the resulting mechanical reinforcement.
Here, we show how the timescale of binder gelation, occurring in the continuous phase of the foam, interplays with foam aging through coarsening to control the final spatial distribution of the solidified binder within the pore space. Gelation is achieved via salt-induced aggregation of silica nanoparticles, and rheological measurements are used to quantify the gelation time, providing a direct link between foam dynamics and binder solidification kinetics under confinement.
Bubble coarsening is characterized using time-resolved measurements of bubble size, obtained from optical imaging at the sample walls. Moreover, X-ray microtomography is employed to resolve the solidified foam–grain architecture at the pore scale. 3D reconstructions are segmented and quantified using AI-based machine-learning tools, enabling statistical characterization of the pore size distribution of the solidified foam relative to the pore size of the granular packing, as well as the morphology of liquid bridges.
The poster presents recent results on the aging dynamics and pore-scale organization of binder foams under confinement in granular packings. Perspectives toward cement-based foams and other foamed binders are also discussed.