Rheopexy in Bentonite

Thixotropic and anti-thixotropic behaviors of fine-grained soils in various flocculated systems

“…For example, a thixotropic system begins to flow under stirring and thickens again when standing (Neaman and Singer, 2000). This behavior is quite different from and should not be confused with the term 'rheopexy' (Barnes, 1989;Freundlich and Juliusburger, 1935;Hauser and Reed, 1936), that is used to denote an effect by which a material recovers some of its pre-sheared viscosity at a faster rate when it is gently sheared compared with when it is allowed to stand (Hackley, 2001). At any given solid content, lowactivity clays exhibit pronounced thixotropic behavior, when a time factor (t b ) of 15 s (shearing time at a constant rate of rotation of 512 rpm) is applied.…”

Recent Advances in Knowledge of the Colloidal Properties of Clay Suspensions and Gels

“…Recent ultramicroscopic observations 6 where under some circumstances two distinct types of structure were noticed are additional evidence in favor of the two-mechanism formation of gel structure.…”

“…This increased viscosity must be due to the interference of the suspended particles of clay with normal flow of the suspending liquid. 6. Under proper, but widely variable, conditions of concentration of clay and electrolyte present it is possible to obtain a clay gel that possesses a yield point necessitating a finite distorting force to make it flow as contrasted to a suspension which, like a true liquid, will flow under a differential distorting force.…”

“…This increase in gelation rate induced by mechanical action is called rheopexy. 6 In the face of such complications it is not surprising that almost no progress has been made toward the quantitative characterization of flow properties of clay suspensions. Clearly, when it is constantly necessary to study the effect of different variables upon the sol-gel transformation where the only detectible differences are mechanical differences, it is important to develop methods of measurement which will distinguish between sol and gel in a precise, quantitative manner.…”

Thixotropy and rheopexy of propyliodone suspensions in arachis oil: Effect of median particle size

“…It is rare to find both phenomena of thixotropy and rheopexy exhibited by one material. Other materials in which rheopexy has been reported are: gypsum, kaolin and Solnhoten slate (Burger & Sollner, 1936); mixtures of glycerol, water and wheat starch (Bon, 1936); bentonite gels (Hauser & Reed, 1936); clay suspensions (Gurvich, 1956); some polyesters and their concentrated solutions in toluene and ethyl benzene (Steg & Katz, 1965); concentrated suspension of the explosive hexahydro-l,3,5-trinitro-striazine (RDX ; cyclonite) in molten trinitrotoluene (Williamson, 1959).…”