  Colloidal suspensions that are out of thermodynamic equilibrium undergo
physical aging wherein their structure evolves to lower the free energy. In
aqueous suspension of Laponite, physical aging accompanies increases of elastic
and viscous moduli as a function of time. In this work we study temporal
evolution of elastic and viscous moduli at different frequencies and observe
that freshly prepared aqueous suspension of Laponite demonstrates identical
rheological behavior reported for the crosslinking polymeric materials
undergoing chemical gelation. Consequently at a certain time tan{\delta} is
observed to be independent of frequency. However, for samples preserved under
rest condition for longer duration before applying the shear melting, the
liquid to solid transition subsequent to shear melting shows greater deviation
from classical gelation. We also obtain continuous relaxation time spectra from
the frequency dependence of viscous modulus. We observe that, with increase in
the rest time, continuous relaxation time spectrum shows gradual variation from
negative slope, describing dominance of fast relaxation modes to positive slope
representing dominance of slow relaxation modes. We propose that the deviation
from gelation behavior for the shear melted suspensions originates from
inability of shear melting to completely break the percolated structure thereby
creating unbroken aggregates. The volume fraction of such unbroken aggregates
increases with the rest time. For small rest times presence of fewer number of
unbroken aggregates cause deviation from the classical gelation. On the other
hand, at high rest times presence of greater fraction of unbroken aggregates
subsequent to shear melting demonstrate dynamic arrest leading to inversion of
relaxation time spectra.
