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Originally posted by Shadowflux
I'm no scientist so the talk of eutectic liquids is really lost on me.
Originally posted by bsbray11
This isn't from thermite, either, or else then you'd only have this where a cut was made, and not all over the entirety of a piece of steel.
Originally posted by bsbray11
Even if that's where it came from, how was it exposed to 1000 + C long enough to show it? Hydrocarbon fires just don't get that hot.
Originally posted by bsbray11
I've seen the beam before but I swear photos must be next to non-existent using Google images now, but it's on the order of magnitude of feet in length and width and the whole outer surface, just about everything I remember being visible of it in the photo, was sulfidated.
Here are images of smaller samples I found:
Originally posted by Griff
Does anyone know if there was a barrier between the steel and aluminum?
Originally posted by bsbray11
On the perimeter columns of the towers, I think some space was left between most of the panels and the steel, like this old illustration shows:
I don't think WTC7 even used aluminum panels on its exterior, but I could be wrong.
Originally posted by Griff
Good points OutoftheSky. Galvanic corrosion may have been present. Although, I don't think it would account for very much strength reducing in the steel. Steel and aluminum aren't that far apart on the galvanic scale. The further apart the metals are on the scale, the more reaction occurs. Plus, the only thing aluminum would be touching would be the outer surface of the perimeter columns. But, I say this without ever seeing the corrosion myself, which could have been significant. Does anyone know if there was a barrier between the steel and aluminum?
The exterior Aluminum panels were designed to meet an unusual set of technical specifications. Those criteria were published in various trade-periodicals at that time. This information has not been released by NIST, or otherwise been widely discussed of late. We know that this material was custom manufactured to exacting specifications.
Typical examples from that era had similar alloy compositions, though none were exactly the same as we use today. By varying the percentages of Silica and Alumina, and lesser quantities of Nickel, Tin and Zinc, this material appeared to meet their needs. (I felt it with my hand, and I have handled dozens of unique samples at dad's request.) Uniquely, I thought it had a very coarse-substrate,(6-8g) as though it were cast, but otherwise it appears to have been an extruded profile with a smooth outer finish, having a good-quality brushed sheen. It literally appeared to be brand-new, and far more durable that any of your contemporary aluminum-laminates, such as "Aluccabond I, and II."
This was formally stated as the key to creating an "elastic membrane," that much I remembered as my project began. Materials experts will attest that the entire composition qualities are important to the integrity of this compound.The 'clear,' electro-metallic plating, (then unproven,) may have contained Sulfur, and was pronounced to have; "effectively prevented oxidization and withstanding the elements, performing better than anyone had expected, over time." -(Architectural Record.)
Special 'elasticity' requirements were weighed against the shear-resistance as required to support the vertical, and lateral loads. Experts did not know what alloy mix would ultimately provide the best solution at the time the project was put out to bids. They had certainly evaluated the known "inter-granular corrosion," statistical guidelines, yet this material had never been subjected to this extreme application for civilian use. I had followed some of this in the trade-journals at the time. Choosing the right mixture was sort of a work in progress right up to the final days before the delivery due date. Certainly today's composites exhibit increased qualities in every regard. However, I will cite this photo example from NIST, because it may well be idemnical to the cause, and it certainly serves as an effective visual aid.
There were a total of about 15 floors which had received new bolts, each bolt-hold requiring a noisy core-drilling which had caused the project to cease. The procedure caused a 'ringing' that transferred the noise, vertically throughout dozens of floors. This infuriated the tenants, beyond belief, and thus it became an unacceptable and impractical approach.
Originally posted by Shadowflux
Please forgive my ignorance but could some one explain Eutectic liquids in layman's terms?
What was NIST's explanation for the total oxidization of the beams?
Originally posted by CaptainObvious
I will refrain from the squib talk, since it is clearly compressed air and debris that was forced out several different areas including stairwells and the lobby's.