Concrete dust & fire

Try an experiment build a fire and throw concrete dust on it, it goes out because it gets smothered.

It's interesting that we have all this concrete dust that should have smothered any fire, not to mention, everthing is gone that was burning. Yet weeks later underground fires continue to burn and way hotter than normal fires would burn. This strongly points to something that dust could not put out or smother, and what's with the intense heat weeks later? Only molton steel could cause this, but the fire wasn't hot enough to create molton steel either during the main fire or afterwards. Another thing the dust should have put out the fires on those cars too, yet we see burnt up cars, what fell on them to cause that?