From liquid to solid bonding in cohesive granular media

TL;DR

This paper investigates the transition from liquid to solid bonding in drying granular media, identifying three regimes of cohesion development and proposing a model linking microscopic bond crystallization to macroscopic strength.

Contribution

It introduces a new experimental framework and a cohesion model that captures the phase transition from liquid to solid bonds in drying granular packings.

Findings

Three distinct regimes of cohesion during drying.

Cementation front propagates nonlinearly from surface to center.

Model accurately predicts the phase transition and cohesion evolution.

Abstract

We study the transition of a granular packing from liquid to solid bonding in the course of drying. The particles are initially wetted by a liquid brine and the cohesion of the packing is ensured by capillary forces, but the crystallization of the solute transforms the liquid bonds into partially cemented bonds. This transition is evidenced experimentally by measuring the compressive strength of the samples at regular intervals of times. Our experimental data reveal three regimes: 1) Up to a critical degree of saturation, no solid bonds are formed and the cohesion remains practically constant; 2) The onset of cementation occurs at the surface and a front spreads towards the center of the sample with a nonlinear increase of the cohesion; 3) All bonds are partially cemented when the cementation front reaches the center of the sample, but the cohesion increases rapidly due to the consolidation of cemented bonds. We introduce a model based on a parametric cohesion law at the bonds and a bond crystallization parameter. This model predicts correctly the phase transition and the relation between microscopic and macroscopic cohesion.