Rheo-thickening suspensions - Principles and applications

Certain particle suspensions have the property of changing from liquid behavior, when at rest or flowing under the effect of a low stress, to solid behavior when stressed beyond a critical stress. This rheo-thickening property has long fascinated scientists and attracted the attention of many manufacturers. Most of them are trying to avoid the damage that such a transition can cause to certain installations (damage to mixers, clogged pipes). Others, on the other hand, are using this property to develop innovative materials such as flexible armor, self-placing concrete and medical protection.

The origin of rheo-thickening of suspensions has long remained obscure. However, recent theoretical predictions finally provide a coherent scenario to explain this transition. The aim of this article is to present this frictional transition model, as well as the various numerical and experimental studies that validate it.

Understanding rheo-thickening should help rationalize certain industrial practices that have remained empirical until now. In particular, we illustrate in paragraph 4 how the frictional transition model can be used to interpret an innovation that has revolutionized the concrete industry. This scenario also offers promising prospects for the development of "intelligent" fluids whose rheology can be adjusted on demand.

At the end of the article, readers will find a glossary and a table of symbols used.