  The aging dynamics after shear rejuvenation in a glassy, charged clay
suspension have been investigated through dynamic light scattering (DLS). Two
different aging regimes are observed: one is attained if the sample is
rejuvenated before its gelation and one after the rejuvenation of the gelled
sample. In the first regime, the application of shear fully rejuvenates the
sample, as the system dynamics soon after shear cessation follow the same aging
evolution characteristic of normal aging. In the second regime, aging proceeds
very fast after shear rejuvenation, and classical DLS cannot be used. An
original protocol to measure an ensemble averaged intensity correlation
function is proposed and its consistency with classical DLS is verified. The
fast aging dynamics of rejuvenated gelled samples exhibit a power law
dependence of the slow relaxation time on the waiting time.
