Picture of a core sample of the 20th floor - WTC

[DoYouEverWonder]

http://911digitalarchive.org/images/files/2804.500px.pjpeg

This is a piece of the 20th floor of WTC2. I worked at the WTC from 1975 to 1979 and acquired this core of the 20th floor in the summer of 1975. All utilities were in metal raceways embedded in the concrete floors. To gain access to electric and phone lines, a hole was bored in the floor. Since we were the first tenants of the 19th and 20th floors, this action was repeated many times to add work stations. I saved one of these cores - all were routinely discarded.

Cite as: James Rogers, Image #2804, The September 11 Digital Archive, 6 September 2005

http://911digitalarchive.org/images/details/2804


Interesting sample the materials used in the floor construction. That stuff looks pretty dense.

[dailykoff]

1. Hey thanks.

Among other things, this shows why preplacing the explosives at any time other than the days immediately preceding the demolitions would be a big mistake.

[Mind_your_head]

2. This sample looks identical to the sample that *I* (and many others) have

from the Aon building (formerly the Amoco building) in Chicago.

Just saying....

---------------

AON Center (Amoco Building)

200 E. Randolph
Chicago, IL 60601

Type: Building
Sub: Landmark


The AON Center (previously known as the Amoco Building) was designed by Perkins & Will and Edward Stone. It was completed in 1974 to become the second tallest building in Chicago. It is 1,136 feet high with 80 stories and 2.3 million square feet of floor space. It offers spectacular views of Chicago and Lake Michigan from all floors.
The tallest building in U.S.A. to ever change its name. Aon Center was known for a long time as the Amoco Building and before that as the Standard Oil Building (or affectionately as "Big Stan").

This is the tallest building in the world without any major antennae, spires, or finials at the top.

[dailykoff]

3. Just saying what?

Whatever you're suggesting isn't clear. Also your link goes to a photo of the building, not a core sample.

[Mind_your_head]

4. Sorry, I wasn't 'suggesting' anything....I really was just 'saying' it

When I saw the OP pic of that core, it was like *gasp* (flashback to something I hadn't thought of/seen in years)....I worked in the Amoco building at one time. I, and probably thousands of us who worked in the building, had these core samples sitting on our desks ~ they made great paperweights! (They're pretty heavy for their small size).

Anyway, the look of the stones embedded in the concrete just looks identical to the core sample I have from the Amoco building. My sample, as did most of them, even has the pencil mark cross-mark on the top. The top of the OP's sample looks more 'orange' though than mine - mine looks gray. I could find the sample and take a picture, but it's probably irrelevant, since it's a different building. I really was just musing about something I looked at every day on my desk for years, which I hadn't thought of in a long time.

Peace

[DoYouEverWonder]

5. Yes, the stones are interesting

This shows that the floors weren't made of just concrete and maybe rebarb. It looks like about half the mixture was small stones. Where did all the stones goes? You would think the debris pile would have been bigger? That they wouldn't get pulverize the way the concrete did?

[Taxloss]

6. Well, those heavy floors made progressive collapse an inevitability.

Heavy floors and insufficient connection to outer frame.

[LARED]

7. I find this very suspicious

All utilities were in metal raceways embedded in the concrete floors.

Typically utilities are run under the floors, so you have easy access to them via the ceilings. Also if this is truly a concrete core from a floor the concrete must have been 9 to 12 inches thick as this guy claims the core in the picture was removed to access a raceway embedded in the floor. The core in the picture is at least 4 to 6 inches thick and the raceway had to have some thickness.

Also there is nothing is any literature saying the concrete floors used 3/4 aggregate as seen in the image, everything I've ever indicates lightweight concrete was used and office areas were up to 4" thick and the core areas were up to 5". In fairness I do not remember reading anything about the type of concrete used in the core area floors.

http://911da.org/about/faq.html#q11

indicates it's position on the authenticity of material submitted

How do I know that the content of the September 11 Digital Archive is factual?

Every submission to the September 11 Digital Archive -- even those that are erroneous, misleading, or dubious -- contributes in some way to the historical record. A misleading individual account, for example, could reveal certain personal and emotional aspects of the event that would otherwise be lost in a strict authentication and appraisal process. That said, most people who take the time to submit something to the September 11 Digital Archive share the goal of its organizers -- that is, to create a reliable and permanent record of responses to the 9/11 attacks -- and therefore most contributions are authentic. Nevertheless, as with any historical sources (including, for example, newspaper accounts), there are always questions about reliability, and all researchers need to evaluate their sources critically. It is for this reason that the Archive harvests metadata from every contributor -- including name, email address, location, zip code, gender, age, occupation, date received -- and suggests that these metadata be examined in relation to one another, in relation to the content of the submission, and in relation to other authenticated records. Sound research technique is the basis of sound scholarship. Researchers with particular concerns should contact [e-mail] for more information.

[DoYouEverWonder]

8. I think they had to drill through the concrete

to get to the open space between the thrushes in order to get to the electric lines. That makes some sense. If you pour a solid concrete floor you wouldn't want to preset the openings because you don't know where you will need them.

Anyway, this is all I can find so far about the construction materials used in the floor. I'll continue looking for something more definitive.




The 10 cm thick concrete slabs were apparently a lightweight form of concrete typically used in high-rises. Its density and exact composition remain unknown, but such lightweight concrete is typically 60% as dense as concrete used in roads and sidewalks. The floors were the only major part of these mostly steel buildings that contained concrete.

http://911research.wtc7.net/wtc/arch/floors.html