Fluid gels’ dual behaviour as granular matter and colloidal glass

Fluid gels are jammed suspensions made of deformable particles obtained by applying shear during the sol-gel transition of a hydrocolloid. Their rheological properties have been shown to be subject to large uncertainty and to change over time undergoing an ageing process. In the present fluid gel literature, it is not known whether such ageing is due to physical ageing, formation of new ion bridges, gravitational effects, or a type of ripening. Methodologies were developed to understand and quantify the fluctuations in the rheological properties of the systems investigated, which were shown to be intrinsic to their jammed particulated microstructure and reminiscent of granular matter. In addition, the time dependent evolution of the rheological properties of fluid gels have been investigated in detail. For the first time, our work determined that the time evolution of the relaxation time is not due to the ripening of the particles, to new ion bridges, and not caused by gravity-induced effects. Our results instead suggest that is caused by physical ageing which is a behaviour reminiscent of colloidal glasses. In this regard, the present study aims not only to support future systematic rheological analysis, considering the intrinsic fluctuations and the time dependency of the rheological properties, but also serves as an aid to successfully design and scale-up industrial applications.