RnD for another CG studio.
You are looking at nasty dirt/sand trouble makers in your household :)
Krakatoa PRT volumes cached as single frame with inherited sand shader from un-animated source meshes. Then KrakatoaSkinWrapped to the animated and fractured version of the same mesh. Animated noise map and 2 KCMs for the "acid burn/eating away" and another KCM for shader animation.
Animations are from the BIPs that ship with Max. Cached with Supermesher, dublicated and time curve animated for variation.
Pre-fracturing was done in Rayfire. Crumble animation triggered with PFlow Box#2. Un-animated Fragments were simply Lock/Bonded to the whole animated mesh and triggered over time and gray scale with Box#3 where and when i needed them.
Set up and rendered on the side on my notebook (core2duo, 4GB). Setup is super fast :)