Abstract
This study investigates (1) the applicability of parallel plate rheology for assessing quick clay stabilisation by inorganic salts and (2) the short-term stabilising effects of selected cation–anion combinations. Quick clay from the Tiller-Flotten geotechnical test site was treated with salt solutions containing Na+, K+, Ca2+ and Mg2+ paired with Cl , OH , SO42 and CO32 at concentrations between 0.037 and 0.6 M. A dedicated rheometer protocol enabled extraction of dynamic and static yield shear strengths and structural build-up, revealing non-Newtonian shear-thinning behaviour. Dynamic yield strength from the upwards flow curve was used as the primary parameter and showed good correlation with falling-cone shear strength, with rheology offering higher precision, reproducibility, and reduced sample size.
Increasing salt concentration consistently enhanced shear strength, with clear ion-specific trends. Divalent chlorides (CaCl2, MgCl2) were most effective at low concentrations but reached a plateau near 0.2 M, while monovalent chlorides continued to increase the strength, with KCl outperforming NaCl at higher concentrations due to the smaller hydration shell and stronger adsorption of K+. Anion effects were strongly governed by pH: Cl and SO42 (neutral pH) promoted flocculation at low concentrations, whereas OH and CO3 2 (high pH) required higher cation concentrations to counteract initial deflocculation. Ca(OH)2 produced the highest shear strength overall. The geotechnical stability criterion of 0.33 kPa was reached for all K-salts and for Ca(OH)2.
Overall, the results show that short-term stabilisation of quick clay is controlled by cation valence, hydration radius, and anion-dependent pH, providing a mechanistic basis for designing more efficient binders for rapid ground improvement.