Rheological properties and critical structure-forming concentration of kaolin suspensions with complex additives

Abstract

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

Effects of sodium tripolyphosphate on the rheology and hydration rate of Portland cement pastes

“…Sodium tripolyphosphate (STPP, also called sodium triphosphate), Na 5 P 3 O 10 , is commonly used in the making of refractory castables (Babkina et al, 2000;Goberis and Stonis, 2004;Goberis et al, 2005) and in advanced ceramic processing (Papo et al, 2002;Slyusar et al, 2008). Typically, STPP is a white powder added to a dry mix or dispersed into mixing water.…”

“…It is a salt of linear polyphosphoric acids, whose basic building unit is the orthophosphate ion (PO 4 3À ) (Rashchi and Finch, 2000). STPP plays the role of a dispersing agent of fine solid particles, improving the rheological properties of concentrated mineral systems (corundum mortars (Babkina et al, 2000), dry castable mixes (Goberis et al, 2005), kaolin suspensions (Papo et al, 2002;Slyusar et al, 2008), plastering mortars (Raupp-Pereira et al, 2007) and cemented paste backfill (Huynh et al, 2006)) for a relatively low cost of production.…”

Effect of nanodisperse particles of silicon and aluminum oxide hydrosols on structure formation of clay minerals in aqueous medium

“…Using different fluidizing additives whose effect is based on ion-exchange processes on the surface of the mineral particles in the slip is an effective method of regulating these properties. The system changes from freely disperse to structured at a certain ratio of disperse phase and dispersion medium in the suspensions [3,4].We know [3] that the laminar structures of clay minerals, primarily kaolinite and montmorillonite, are composed of parallel layers of silicon-oxygen tetrahedrons with aluminum, magnesium, and iron atoms basically positioned in the center. The differences in the structure of these minerals are due to the density of the crystal lattice and the distance between regularly repeating groups of ions (planes), equal to 0.72 nm for kaolinite and on average 1.5 (0.95 -1.9 nm) for montmorillonite [5].…”

“…Using different fluidizing additives whose effect is based on ion-exchange processes on the surface of the mineral particles in the slip is an effective method of regulating these properties. The system changes from freely disperse to structured at a certain ratio of disperse phase and dispersion medium in the suspensions [3,4].…”

Complex thinning additions for ceramic slips

“…It has been shown [1,2] that the mobility of suspensions is observed to increase substantially when fluoroglucin furfurol oligomers (SB-FF) are introduced into clayey suspensions in a complex with conventional thinners. The addition of SB-FF in a complex with sodium tripolyphosphate (STPP) is especially effective.…”