Interplay of coarsening, aging, and stress hardening impacting the creep behavior of a colloidal gel

• Published in: Journal of rheology (New York : 1978) 2017-07, Vol.61 (4), p.817-831
• Main Authors: Calzolari, D. C. E., Bischofberger, I., Nazzani, F., Trappe, V.
• Format: Article
• Language: English
• ISSN: 0148-6055; 1520-8516
• DOI: 10.1122/1.4986465

We explore the dynamical and mechanical characteristics of an evolving gel in diffusing wave spectroscopy (DWS) and rheometry, aiming to assess how the gel evolution impacts the creep response of the system. Our gel is formed by inducing the aggregation of thermosensitive colloids by a variation in temperature. We find experimental evidence that the long time evolution of this gel is due to two distinct processes: A coarsening process that involves the incorporation of mobile particles into the network structure and an aging process that triggers intermittent rearrangement events. While coarsening is the main process governing the evolution of the elastic properties of the gel, aging is the process determining structural relaxation. The combination of both processes in addition to stress hardening governs the creep behavior of the gel, a creep behavior that is determined by three distinct contributions: an instantaneous elastic, a delayed elastic, and a loss contribution. The systematic investigation of these contributions in recovery experiments provides evidence that losses and delayed elastic storage have a common origin, both being due to intermittent local structural relaxation events.