Identification of granular compactness during the kneading of a humidified cohesive powder

The aim of this study is to identify the granular arrangements obtained during the kneading of a powder with various proportions of water, throughout the transition field between the dry state and the saturated pasty state. Regarding texture, several phenomena are highlighted making it possible to divide the hydrated state of the wet granular medium into three distinct zones. The follow-up of the hydro-textural and dimensional variables of the granular medium on the observation scales of the agglomerates and of the bulk medium makes it possible to lay down the basis of an interpretation of the texturing phenomenon. It reveals two successive modes, which are the agglomerate mode and the pasty mode. During the transition between these two modes, a percolation phenomenon of the agglomerates is highlighted.

During wetting, the volumic solid fraction of a granular medium follows a texturing curve divided into three stages: (i) the expansion stage, (ii) the densification stage which starts gently, becoming sharp for water content close to the plastic limit of the product and (iii) the dilatation stage. During this evolution, the medium undergoes morphological modifications: from a powder to a continuous paste.Figure optionsDownload as PowerPoint slide