"C4 pulverized the floors"

If indeed there WERE any explosives used, I would suspect it would have been a mixture of cyclotrimethylene-trinitramine and pentaerythritol-tetranitrate which are the explosive ingredients of a substance sold commercially under the name Semtex.

Primacord (pentaerythritol tetranitrate) detonates at about 8,000 feet per second. In other words, it blows up real fast--a mile and a half per second is fast. (I have not kept up my reading on explosives and it's possible that the blast rate of Primacord is somewhat slower than the figure I've given. But I do know that there is a type of Primacord out now that DOES fire at the rate of 8,000'/second.)

Semtex usually has ethylene glycol dinitrate added as a detection taggant, but the material can be made without the tag added to it. However, I would suspect that even today, if materials from the Towers were made available to a lab, and the lab was instructed to LOOK for the presence of a Semtex residue, it could be determined whether it was present in the Towers as far back as September 11, 2001. But I don't think that's gonna happen anytime soon.

Something turned the cement floors to dust. Without suggesting that the NIST report missed it on purpose (if you ain't looking for explosives, y'ain't gonna FIND explosives, and the investigators at the time would have had no reason to suspect the Towers to have fallen because of explosives), and without suggesting that there was any malfeasance on their part, why would it be so difficult for NIST to check today? But I don't think that's gonna happen anytime soon either.

"Three pounds of Semtex plastique packs enough punch to raze a two-story building."

Food for thought.

And before anyone gets all nutso, let me ask this: Why NOT test for the assortment of explosive available for use these days? It would sure shut down this type of speculation--OR open a door that officialdom would love to keep closed.