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The influence of complex additives on the critical structure-forming concentration of kaolin suspensions is studied. A complex consisting of the oxyphenofurfural oligomer SB-FF and sodium tripolyphosphate, which can be used as a fluidizing additive for kaolin suspensions, is most effective at low concentrations.Slips with minimum moisture content and adequate mobility are obtained by introducing fluidizing additives. Complex additives containing conventional electrolytes are promising: water glass and soda as well as sodium tripolyphosphate (TPP), oxyphenolfurfural oligomers SB-5 and SB-FF, and the superplasticizer S-3 [1, 2].The present work continues investigations in this direction. The concentrations and optimal ratios of SB-FF (product of the simultaneous condensation of phloroglucine and furfural) and TPP for suspensions of kaolin from the Glukhovetskoe deposit were found. For comparison, the following complexes were used: S-3 + TPP, SB-5 + TPP, and reotan + TPP. The initial suspensions were prepared with water-solid ratio 0.6, i.e., close to the critical concentration of structure formation or optimal moisture content. The effect of the concentration of complex additives on the rheological parameters of a kaolin suspension were investigated with a Rheotest-2 flowmeter. The rheological curves were used to determine the maximum dynamical shearing stress t 0 and the plastic viscosity h pl of a kaolin suspension. The dependence of the values of t 0 on the concentration of complex additives is presented in Fig. 1.When complex additives are introduced, the maximum dynamical shear stress, characterizing the strength of coagulation structures, decreases substantially. The most effective complexes at low concentrations are SB-FF and TPP. Thus, the introduction of 0.2% (SB-FF + TPP) decreases t 0 from 224 to 47 Pa, and complexes containing the oligomers SB-5, S-3, and reotan decrease t 0 to 61, 87, and 150 Pa, respectively.Previous investigations have shown that for a certain ratio of a dispersed phase and a dispersion medium in suspensions a sharp change is observed in the physical and chemical parameters of the system, characterizing a transition of the system from freely dispersed to structured [3,4]. Attraction forces between particles in the system start to predominate over the repulsion forces, and coagulation spatial structures where particles of the dispersed phase are coupled via thin residual interlayers of fluid are formed. The concentration of the dispersed phase at which such a transition is observed is called the critical structure formation concentration (CSC). An identical concept is used in ceramics technology -the optimal moisture content.The influence of complex additives on the critical structure formation concentration of kaolin suspensions was investigated in this work. The value of t 0 was used as an example characterizing the concept of structure formation. Kaolin

The influence of the complex additions SB-FF + STPP, S-3 + STPP, reotan + STPP on ceramic slip mobility is examined. The action of these complexes on the physical -chemical properties of ceramic samples after kilning is studied. It is found that the complex addition SB-FF + STPP makes it possible to increase ceramic slip mobility and mass build-up rate as compared with the additions based on S-3 and reotan as well as to improve the operating properties of finished articles.

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