Hydrotextural Description of an Unsaturated Humid Granular Media: Application for Kneading, Packing and Drying Operations

Abstract

The kneading of a powder generates a product made of three phases (solid/liquid/gas) that interact through many interfaces. The respective proportions of each phase can vary according to the process parameters and the applied stress. After the initial operation of kneading, the medium can also be subjected to other stresses such as packing and thermal stresses or mechanical drying which will induce deep modifications in the relative proportions of the three phases. According to the twin influence of process strain and the nature of the three phases, the rheological behavior of the granular material can vary from that of a rigid solid to that of a more or less deformable plastic paste. The objective of this work is to depict, on a phase diagram, the potential states of each fraction constituting an unsaturated wet granular medium and their potential connectivity. From an experimental point of view, sorption isotherms and capillary retention curves allow determination of the two fluid phases state (liquid and gas). The hydrotextural diagram can be considered as a tool for the analysis and understanding of the mechanisms occurring during the processing (kneading and packing) or drying of wet granular media.

Keywords

• state diagram
• humid granular media
• kneading
• packing
• drying
• transformation path