Phys Rev E Stat Nonlin Soft Matter Phys. 2015 Jul;92(1):010202. doi: 10.1103/PhysRevE.92.010202. Epub 2015 Jul 23.

Bernal random loose packing through freeze-thaw cycling.

Physical review. E, Statistical, nonlinear, and soft matter physics

F Ludewig, N Vandewalle, S Dorbolo, M Pakpour, G Lumay

PMID: 26274104 DOI: 10.1103/PhysRevE.92.010202

Abstract

We study the effect of freeze-thaw cycling on the packing fraction of equal spheres immersed in water. The water located between the grains experiences a dilatation during freezing and a contraction during melting. After several cycles, the packing fraction converges to a particular value η(∞)=0.595 independently of its initial value η(0). This behavior is well reproduced by numerical simulations. Moreover, the numerical results allow one to analyze the packing structural configuration. With a Voronoï partition analysis, we show that the piles are fully random during the whole process and are characterized by two parameters: the average Voronoï volume μ(v) (related to the packing fraction η) and the standard deviation σ(v) of Voronoï volumes. The freeze-thaw driving modify the volume standard deviation σ(v) to converge to a particular disordered state with a packing fraction corresponding to the random loose packing fraction η(BRLP) obtained by Bernal during his pioneering experimental work. Therefore, freeze-thaw cycling is found to be a soft and spatially homogeneous driving method for disordered granular materials.

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• Journal Article