Dynamics of internal stresses and scaling of strain recovery in an aging colloidal gel.

We monitor the relaxation of internal stresses in a fractal colloidal gel on cessation of flow and find a weak power-law decay, sigmai approximately t(-alpha) over five decades of time where alpha approximately 0.07. The system exhibits physical aging of the elastic modulus, G' approximately tbeta, with beta approximately alpha . Imposition of zero stress after waiting time tw results in strain recovery as the system relaxes without constraint. Remarkably, recoveries at different tw can be shifted to construct a master curve where data are scaled vertically by 1/sigmai(tw) and plotted horizontally as (t-tw)/twmu, where mu is approximately 1.25, indicative of a superaging response.