Rotations in shear bands and polydisperse packings

High resistance concrete or hard ceramics needs extremely dense granular packings which can only be realised when the size distribution of grains follows a powerlaw. We discuss the perfectly dense limit, namely Apollonian packings in three dimensions and show in particular the existence of space filling bearings rotating without slip and without torsion. When a dense packing like tectonic gouge is deformed, it glides internally on shear bands. The existence of rotations in shearbands is evidenced by molecular dynamics simulations of disks.