Liquid distribution and cohesion in wet granular assemblies beyond the capillary bridge regime

Mario Scheel, Ralf Seemann, Martin Brinkmann, Marco Di Michiel, A. Sheppard, Stephan Herminghaus

Research output: Contribution to journalArticlepeer-review

69 Citations (Scopus)

Abstract

Dry sand turns into a stiff and moldable material as soon as it is mixed with some liquid. This is a direct consequence of the internal liquid–air interfaces spanning between the grains which causes capillary cohesion by virtue of the surface tension of the liquid. As a model for wet granulates we investigated random packings of submillimeter spherical beads mixed with water. Measurements of the tensile strength and the fluidization threshold demonstrate that the mechanical stiffness is rather insensitive to the liquid content over a wide range. Only for a high liquid content, when more than half of the available pore space is filled with liquid, does the capillary cohesion weaken. In order to understand the interplay between the mechanical properties and the liquid content, we investigated the liquid distribution in random packings of glass spheres by means of x-ray microtomography. The three-dimensional images reveal that the liquid forms a network of capillary bridges fused at local triangular bead configurations. The spontaneous organization of the liquid into these ramified structures, which exhibit a large liquid–air interface, is responsible for the constancy of the cohesive forces in a wide range of liquid contents beyond the onset of capillary bridge coalescence.
Original languageEnglish
Article number494236
JournalJournal of Physics Condensed Matter
Volume20
Issue number49
Early online date12 Nov 2008
DOIs
Publication statusPublished - 10 Dec 2008
Externally publishedYes

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