Of course there is no description of what it is if not concrete. That would look too stupid for the perps to let you attempt that.
agent gamit, and many others try to assert that gypsum could stand, attached to core columns AFTER 100's of 1,000's of tons of structural steel had fallen past it. Of course, to leave a solid rounded shape like that, with no holes, no structural protrusions of mangled steel structure, just ain't f'nnnn possible.
That one picture takes out any possibility of steel core columns because IF they were there, gypsum would be between them AND massive diagonal/horizontal bracing, such is very obvious in silhouette.
Unfortunately I we learn from you is that you have no problem attempting to fight an impossible battle with no evidence, only collusive, abusive co agents and inept manipulations.
Consider how badly you are doing in opposition to independently verified evidence of the crimes scene. The concrete core, is consistent with even the misrepresented construction data and visible in 9-11 images while numerous statement identify it as well from authorities in a position to know from the private sector not related in anyway.
The cause of death of 9-11 is invalidated.