Thermally induced viscoelastic reinforcement and relaxation dynamics in bentonite particulate suspensions

The temperature-dependent rheology of concentrated Na-bentonite particulate suspensions (6 wt%) was investigated between 25 and 65 °C using steady and oscillatory rheometry. Heating induced a pronounced viscoelastic reinforcement, with the storage modulus G′ and yield stress increasing by factors of 17.6 and 5.3, respectively. Flow curves exhibited strong shear-thinning behavior and were accurately described by the Herschel–Bulkley model. Frequency spectra and structural recovery kinetics were analyzed using generalized Maxwell and Kohlrausch–Williams–Watts (KWW) models. The results reveal a coupled reinforcement–acceleration behavior in which the colloidal network becomes simultaneously stronger and dynamically faster with increasing temperature. The dominant relaxation time decreased by approximately 65%, while the stretching exponent β increased from 0.75 to 0.95, indicating a narrower relaxation-time distribution and more homogeneous restructuring dynamics. A strong linear correlation (R2 = 0.997) between G′ and the inverse slow relaxation time (1/λ1) further supports the coupling between viscoelastic reinforcement and relaxation kinetics. These findings provide a thermo-rheological framework linking interparticle interactions, network reinforcement, and relaxation dynamics in bentonite particulate suspensions.