The hydrodynamic behaviour of suspended colloid aggregates is studied in three centrifugal separators. The experiments outline the effects of the residence-time duration and of the bowl geometry on the aggregate shear thinning. The flee destruction is stated either From the decrease of their average size d(t) with time, or from the production of microflocs, the statistical diameter of which, d(MF), may be compiled from the flee size distribution. They both extend towards equilibrium values : d(min), the final average size of the aggregates that depends on the shear rate, and d(MF), the indestructible microfloc average diameter that may be considered as a physicochemical character. The equilibrium average sizes of the flocs as well as of the microflocs are reproducible at different geometric scales. Lastly, the kinetics of floc shear thinning might be approximated as a function of d(min) and d(MF) as was checked in the centrifugation tests of MnO2 colloidal suspensions : d(d(t))/dt = k(2) . d(MF).(1-d(t)/d(min)). Three different colloidal suspensions : MnO2, Ru-Mo and dissolution juices of irradiated fuel are flocculated through hydrosoluble polymer addition. The comparisons of d(min) and d(MF) values measured for each initial suspension, then for the flocculated suspensions conclude that flocculant adjunction enables the improvement of the floc toughness to the shear rate, but also modifies their ordering into bigger and indestructible microflocs. Lastly, the obvious effect of the flocculant ionicity, observed on basic suspensions as well as on acid suspensions, claims that the nature of the acting interparticle forces entirely defines the aggregate structure and therefore their cohesion.