Consolidation of strong colloidal gels under arbitrary compressive loadings

Predicting the mechanical response of the soft gel materials under external deformation is of paramount importance in many areas, such as foods, pharmaceuticals, solid-liquid separations, cosmetics, aerogels and drug delivery.Most ofthe understanding of the elasticity of gel materials is based on the concept of fractal scaling with very little microscopicinsights.Previous experimental observations strongly suggest that the gel material loses the fractal correlations upondeformation and the range of packing fraction up to which the fractal scaling can be applied is very limited.So far, there is no clear understanding of the gel elasticity at high packing fraction and the correct length scale that governsits mechanical response. In this work, we undertake extensive numerical simulations to elucidate the different aspectsof stress transmission in the gel materials. We observe the existence of two percolating networks of compressive andtensile normal forces close to the gel point. We also find that the probability distribution for the compressive andtensile part normalized by their respective mean shows universal behavior irrespective of varied interaction potential,thermal energy and particle size distribution. We alsoidentify the critical internal state parameters such as mean normal force, force anisotropies and the average coordinationnumber and propose simple constitutive relations that relate the different components of the stress to the internal stateparameters.Our resultsstrongly demonstrate that the mechanical response of the gel system is governed mainly by the particle length scalephenomena with a complex interplay between compressive and tensile forces at the particle contact.

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Micro-mechanical insights into the stress transmission in strongly aggregating colloidal gel

Man

Dagur

Roy

2023

The Journal of Chemical Physics

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Superposed shear and compression of strong colloidal gels

Islam

Lester

2021

Journal of Rheology

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Although the rheology of strong colloidal gels is predominantly concerned with either pure shear or pure compressive deformation, the vast majority of practical applications involves an arbitrary combination of shear and compressive stresses and strains. This situation demands a tensorial rheology of colloidal suspensions, where the multidimensional response of these complex materials to arbitrary superposed stress states needs to be characterized and constitutive models developed. In this study, we use 2D discrete element modelling simulations in the absence of hydrodynamic interactions to probe the behavior of a model strong colloidal gel under combined shear and compressive deformation. We consider the deformation and failure of these gels under strain-controlled conditions that range from pure compression to shear-dominated consolidation. Particle-scale observations uncover how shear stresses act to stimulate nonaffine buckling and rupture of force chains during consolidation, leading to augmented failure and collapse of the particle network. At the macroscopic level, we find that the energy required to consolidate a colloidal suspension from the gel point to close packing passes through a minimum that corresponds to weak shear strain, indicating that small amounts of shear play a critical role in destabilizing the colloidal network. These results represent an important step toward a complete understanding of the tensorial rheology of strong colloidal gels.

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Consolidation of strong colloidal gels under arbitrary compressive loadings

Abstract: Visualization of the particulate network (left) and force chains (right) at various solids concentrations during biaxial consolidation.

Cited by 2 publications

References 47 publications

Micro-mechanical insights into the stress transmission in strongly aggregating colloidal gel

Micro-mechanical insights into the stress transmission in strongly aggregating colloidal gel

Superposed shear and compression of strong colloidal gels

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