Normal stress differences in the consolidation of strong colloidal gels
- PDF / 1,654,037 Bytes
- 18 Pages / 595.276 x 790.866 pts Page_size
- 19 Downloads / 194 Views
ORIGINAL CONTRIBUTION
Normal stress differences in the consolidation of strong colloidal gels Mohammad M. Islam 1
&
Daniel R. Lester 1
Received: 24 July 2020 / Revised: 5 November 2020 / Accepted: 6 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Macroscopic models for the uniaxial consolidation of strong colloidal gels typically characterise the compressive strength of the particulate network in terms of the compressive yield stress Py(ϕ) or uniaxial elastic modulus K ′ (ϕ). Almost all industrial applications involve multi-dimensional (MD) configurations with arbitrary tensorial stress states, and it is unclear how to generalise these 1D constitutive models to MD consolidation. Several studies have attempted to extend these 1D constitutive models to MD by assuming either isotropic consolidation or zero Poisson’s ratio, but the validity of these assumptions is currently unknown. Lacking is a validated tensorial rheology for the consolidation of strong colloidal gels that is capable of predicting the consolidation of these materials. One step toward the development of such tensorial rheology is the consideration of normal stress differences (NSDs) during uniaxial consolidation. Thus, a tensorial constitutive model for the consolidation of colloidal gels cannot be developed without accounting for these NSDs. We address this problem by performing discrete element model (DEM) simulations of the uniaxial consolidation of a two-dimensional (2D) strong colloidal gel and investigate evolution of the tensorial stress state during consolidation. We show that during consolidation, the Poisson ratio increases from zero near the gel point to almost unity near close-packing and uncover the particle-scale mechanisms that underpin these observations. These results provide the first steps toward a complete tensorial rheology of colloidal gels that is capable of resolving the evolution of these complex materials under superposed differential compression and shear. Keywords Colloidal gel . Consolidation . Compressive rheology . Suspension
Introduction The consolidation of colloidal suspensions and gels is a problem of significant theoretical and practical importance. It is essential to many industrial processes such as the formation and performance of paints and coatings (Brown et al. 2002), solid-liquid separation processes (Landman et al. 1991; Landman and White 1994) and ceramic processing (Lewis 2000). Over 35 years ago, Buscall and White (1987) proposed a one-dimensional (1D) theory for the consolidation of strong colloidal gels based on the inverse permeability R(ϕ) and compressive yield strength Py(ϕ) of these materials. These material functions respectively control the rate and extent of consolidation and are both strongly varying functions of the solids concentration ϕ. This theory, along with many other equivalent models (Dixon 1977; Fitch 1983; Landman et al. * Daniel R. Lester [email protected] 1
School of Engineering, RMIT University, Melbourne 3000, Australia
1991; Lan
Data Loading...
