Rheological inversion of the universal aging dynamics of hectorite clay suspensions

• Frequency-dependent dynamic moduli were monitored during aging.
• Time—aging time—temperature superposition observed.
• Non-equilibrium relaxation time spectra of aging clay suspension.
• Rheological inverse from gel to glass as clay concentration increases.

Aging of salt-free suspensions of hectorite clay was investigated with rheology of multi-wave small amplitude oscillatory shear. The frequency-dependent storage and loss moduli at different waiting times and temperatures were scaled into a master curve, conforming the time-temperature-aging time superposition. In other words, thermorheological simplicity was maintained during aging. While the relaxation time of the system grew monotonically with increasing waiting time, and showed non-monotonic dependence on temperature, consistent with our previous results. The relaxation spectra converted from the master curves of different clay concentrations were described by a power-law distribution with a stretched exponential cutoff. The dynamics were slower for high clay concentration. A rheological inverse from gel-like to glass-like distribution was observed with the increase in clay concentration.

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