"NIST's findings do not support the "pancake theory" of collapse, which is premised on a progressive failure of the floor systems in the WTC towers (the composite floor system—that connected the core columns and the perimeter columns—consisted of a grid of steel "trusses" integrated with a concrete slab; see diagram below). Instead, the NIST investigation showed conclusively that the failure of the inwardly bowed perimeter columns initiated collapse and that the occurrence of this inward bowing required the sagging floors to remain connected to the columns and pull the columns inwards. Thus, the floors did not fail progressively to cause a pancaking phenomenon."

NIST itself disagrees with the pancake theory. So once again, what caused the pulverization of the cement floors? (Did your dog ever get a bone he just wouldn't leave alone--I said bone, no bone on--because to me a serious answer to the question of the cement dust is central to understanding the collapse cause.