INFLUENCE OF ULTRASONIC TREATMENT ON THE VISCOSITY OF AQUEOUS-CLAY SUSPENSIONS FOR SAND-CLAY MIXTURES
The article considers the influence of frequency and time of the ultrasonic treatment on viscosity of bentonite suspensions. The object of the study is the bentonite clay of Zyryanka deposit which was used as the base for water-clay suspensions. Suspensions were examined for conditional viscosity, which was determined by the viscometer VZ-2 and for the dynamic viscosity which was determined by the rotary viscometer Brookfield Rheo V 2.8. In ultrasonic processing the dispersion system is divided into four zones, such as the zone of active dispersion of the solid phase, the transitional zone, the zone of wave and hydrodynamic coagulation and the zone of sustainable structural and rheological equilibrium state of the solid solution phase. It has been shown that the ultrasonic treatment of clay suspensions causes both dispersant and aggregated action depending on the processing time and power. It is established that water-bentonite clay suspensions are thixotropic non-Newtonian fluids with a pseudoplastic flow. Ultrasonic treatment during 15 minutes leads to the decrease of the relative viscosity of suspensions due to the formation of periodic colloidal structures, followed by the process of autocoagulation. Ultrasonic treatment by the field of 20 kHz during 1.5 minutes leads to the decrease of the dynamic viscosity of suspensions due to the particles dispersion. Ultrasonic treatment by the field of 50, 60 kHz during 1.5 minutes leads to the increase of the dynamic viscosity of suspensions due to particles coagulation. It is established that the stability of activated coagulation systems to mechanical stresses is much less than in original bentonite clays, which enables to realize more uniform distribution of clay minerals along the surface of the quartz sand and to provide the increase of a number of cohesive and adhesive contacts and the improvement of physical and mechanical properties of mixtures in the forming process.