Let's not stray too much from Tony's point that the aggregate helps to strengthen 'structural' concrete, which is to say, not the floor systems used in steel structures where the lightweight concrete is more frosting than anything else, and the steel trusses are distributing most of the loads to the columns (with the help of the steel pan/lightweight concrete diaphram). Without the aggregate, the concrete used in flooring systems would be more prone to pulverization IMO. Certainly, not much concrete remained in chunk form at ground zero- this was, of course, quite unexpected.

My initial reason for posting was to show someone why it was plausible for a controlled demolition to have caused the pulverization we witnessed.

I am thinking this through as we post on here so don't think I am being hardnosed about it.

I believe the lightweight concrete had something to do with the concrete being pulverized more easily but that doesn't have to be true to show there was enough energy in the continuous controlled demolitions which took down the towers. So the lightweight concrete is a side issue.

We have learned some things here though and that is there was only rebar in the concrete at the mechanical floors and the parking garages. That makes sense and validates for the most part what I was saying about the lack of need for rebar. The lack of rebar would allow the concrete to come apart easier.

Concrete is composed of portland cement, sand, and coarse aggregate. Aggregate is used for taking up space in the concrete and the portland cement is the binder or glue. It is the type of aggregate which is part of the lightweight concrete. However, there is another trick it seems and that is the use of a foaming agent which would reduce the density of the concrete..

The energy can be shown to be there if one understands the continuous demolition from the top down. The lack of rebar would also contribute to it. And finally if the density of the concrete was lower there would be less surface area binding everything together in the concrete, which would have been fine for the office floors in the towers, which over 90% of the floors were.

Special thanks to BMAC for questioning. I agree with your point that an assertion needs to stand up to scrutiny, as long as it is honest, which I believe your questions were. I think we did finally resolve things to some extent. Do you agree?

is in the vacinity of 10-12 seconds from the height of the twin towers, factoring in terminal velocity due to air resistence, depending on the mass to surface area ratio of the object, any object. From initation of the destruction, to its end, the north tower "collapse" time, is somewhere between 12 and 14 seconds, and so, within that one or two second difference, exists the ONLY remaining alotted timeframe within which every single weld and joint would have to fail, and so it can be said, in effect, that they all failed in near simultaneity, without any resistence encountered, at all, a violation of Newton's first and third laws of inertia.
We'll let the experts render this in scientific terms, but it's not neccessary, as the truth here is totally self evident. It''s strange to me, that you'll see even truthers trying to make it more complicated than it is.

I like the way Greame explains it in that Part One Youtube clip. I thought I'd just add the observation, that the building "fountained" at near total free fall speed in air, ejecting the vast majority of debris in an outwardly ejecting debris plume (though symetrically) throughout the progression of descent, which lost no momentum, while encountering NO RESISTENCE of any kind throughout!

Thus any RESISTENCE calcs, would be most helpful, from the ground, all the way up to the impact area. It doesn't make sense to me either the way the OT claims this cumulative "dynamic" loading, only having to deal with the resistence of one floor at a time, since the remaining strength of the building, upheld everything above it and more, throughout the lifetime of the building, and since the debris plume would have to plow down through the verticle axis and therefore through the path of maximum resistence, leaving about nothing at all, in its wake. "Foot of God"...?
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