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 (Zg(1), Zg(2), and Zg(3)) and Hawaria area (Ha1, Ha(2), and Ha(3)) 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 Ha(2) sample. The CaO rate was high (5.08 and 7.16 wt %) for Ha(3) and Zg(3) 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.