Desiccation cracks in clay composites unveil intricate physicochemical dynamics, yet their control is pivotal for geotechnical and environmental engineering. This study investigates the influence of cation valency and ionic size on desiccation crack patterns in bentonite–chloride salt slurries. Controlled drying experiments were performed using monovalent (NaCl, KCl), divalent (MgCl \(_2\) , CaCl \(_2\) ) and trivalent (FeCl \(_3\) ) cations. Crack development was monitored by high-resolution imaging and quantitatively analysed using Python-based image processing. Complementary aggregate size distribution, zeta potential, X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) measurements were used to elucidate the physicochemical mechanisms controlling crack morphology. Results show that both cation valency and ionic radius substantially affect water retention and aggregation in the slurry and consequently determine crack network characteristics (node and ped counts, growth rates and temporal regimes). Notably, the influence of inner orbital electron screening in Fe \(^{3+}\) —manifest as reduced effective ionic radius and altered swelling — was experimentally evident via crack statistics. Observed trends are interpreted using an integrated framework that couples DLVO interactions, capillary-driven hydro–mechanical stresses and fracture mechanics. The findings provide mechanistic insight into salt–clay interactions with implications for designing crack-resistant bentonite-based barriers.
