The Effect of the Proportion and Clay Mineralogical Composition on the Rheological Properties of the Raw Clay and the Sodium Carbonate Treated Clay Suspensions

The X-ray diffraction, infrared spectroscopy, chemical analysis, and cation exchange capacities are the most common techniques used for the physico-chemical study and characterization of clays. All of these used in the present study showed that the Tunisian clay samples collected from Zaghouan area (Zg₁, Zg₂, and Zg₃) and Hawaria area (Ha1, Ha₂, and Ha₃) consisted of illite, kaolinite, and smectite associated with quartz, K-feldespar, calcite, and dolomite. The chemical analysis revealed that Al₂O₃ is relatively high in the Ha₂ sample. The CaO rate was high (5.08 and 7.16 wt %) for Ha₃ and Zg₃ samples. To demonstrate the impact of clay mineralogical composition on the rheological properties, six samples were used to prepare the mixed clay aqueous suspension. Its effect depends on the proportion of the 2:1 phyllosilicate, especially smectite, as well as on the rheological properties of the blank clay suspensions and of Na₂CO₃ treated ones. Calcite forms large agglomerations with clays minerals, which prevents flocculation. The negative charges in the tetrahedral layers were generated by the substitution of Si⁴⁺ with Al³⁺, and they were compensated by the interlayer exchangeable cations. Therefore, the interlayer hydration leads to an increase of the dispersion of clay particles and rheological properties.