Scaling behavior of the rheological properties of montmorillonite suspensions: Correlation between interparticle interaction and degree of flocculation

In this work we investigate some aspects of the theological behavior of sod ium montmorillonite (NaMt) suspensions in the pH range 3 to 9, of NaCl conc entrations between 10(-3) and 10(-1) M, and of solid concentrations between 5 and 11% w/v, Three kinds of experiments were performed: steady-state vis cometry, oscillatory test, and creep recovery. The physical quantities of i nterest were the yield stress cr, of the suspensions, the elastic rigidity modulus G', and the instantaneous elastic compliance. Furthermore, G' was o btained from oscillatory tests in three different experiments: determinatio n of the viscoelastic linear region, oscillograms, and the gelation process . All quantities were found to scale with the concentration of solids, C, a ccording to a power law of the form Y = k(y)C(n). The exponents were found to change from similar to3 to similar to6 when the pH was increased from 3 to 9 (at constant ionic strength 10(-2) M), although values as high as 10 w ere estimated when the NaCl concentration was reduced to 1 mM. Such values of n correlate well with the characteristics of the edge-to-face (E-F), edg e-to-edge (E-E), and face-to-face (F-F) interparticle interactions. The min imum values of n correspond to maximum E-F attractions, whereas the largest n are associated with strong F-F repulsions. (C) 2001 Academic Press.