WTC Dust Cloud Analysis

[LARED]

There was some debate at http://www.democraticunderground.com/discuss/duboard.php?az=show_topic&forum=125&topic_id=431#679 regarding what a link abstract implied about the WTC dust cloud. So, I purchased the paper that this abstract was based on in order to get the full scoop.

See abstract here;
http://ehpnet1.niehs.nih.gov/docs/2002/110p703-714lioy/abstract.html

I put up a the results of the part of the analysis for everyone to see.

Dust Analysis

[SoFlaJets]

1. When I went there to see My City of Ruins

when the facade was still up there was a security guard telling everybody to get out this stuff'll kill ya-the smell was like burnt wet concrete-a smell I know from working all those years cutting thru mortar wit a saw...

[jfkennedy]

2. I live not far from Ground Zero

I live around 20 blocks from Ground Zero and I usually cleaned out my air filter twice a month or more before 9/11. After 9/11 I had to clean it, I think it was silver dust every day, because it was at its peak of being polluted, and now they are saying the dust was toxic, but Bush ordered the media and the EPA not to print it.I think I had to clean it every day for around 2 or 3 months after 9/11.

I'm glad I had my filter working.

[LARED]

3. I'm shocked

just shocked I tell you.

I went to the expense and time to post some very interesting data regarding the dust cloud and not one of the '9/11 investigators :tinfoilhat: ' have posted a comment. :evilgrin:

Where are the accolades and pats on the back for a job well done?

Shocking

[DeadBroke]

4. Thanks

I appreciate your effort LARED. I’ve always wondered why or how those 3 sample areas; Cortlandt, Cherry, and Market were chosen. Were they randomly selected, or were they chosen solely for the weather protection? Cortlandt Street, a short east-west street that was always in the evening shadows of the South Tower, is just a short walk, 2-3 blocks at most from the front of City Hall. Cherry, way over on the eastside, runs north-south from the Smith Houses near the Brooklyn Bridge, intersects Market Street by Coleman Park, goes under the Manhattan Bridge, runs into the Vladeck Houses, but continues on the other side up to Corlears Hook. Do you know where along these streets the samples were collected?

[LARED]

6. This is what the paper says

I hope this is helpful

Samples of the total settled dust and
smoke were collected at three different locations.
The first sample was collected from
protected external ledges around the entrance
of a building on Cortlandt Street, which is
one block east of the WTC building complex.
The initial direction of the plume was
from west to east (Figure 1); thus, the other
two samples were collected at locations to the
east of Cortlandt Street. These two samples
were collected from 10–15 cm-thick deposits
that were on the top of two automobiles
about 0.7 km from the WTC site. The automobiles
were in locations protected from rain
that occurred on Friday, 15 September 2001.
One automobile was located on Cherry Street,
and the other was on Market Street, one and
two city blocks, respectively, west of the East
River between the Manhattan and Brooklyn
Bridges. These cars appeared to have been in
their respective locations since 11 September,
but it is possible that each could have been
moved from an adjacent thoroughfare on the
east side of NYC (FDR Drive).

One of the reasons for collecting samples
from these locations was to determine
whether chemical composition and physical
morphology of the particles changed with
distance from the WTC site. The samples
were collected using the protocols established
for surface soil collection in our studies of the
dispersal of chromium-laden hazardous waste
in Jersey City, New Jersey (2), and the
National Human Exposure Assessment
Survey (3). After collection, all samples were
stored in a 4°C room prior to sending the
subfractions to individual laboratories for
analysis. We maintained chain of custody
throughout sample transferal and analyses.

[DeadBroke]

20. High-n-low

I've been searching high-n-low for info on dust analysis; newspapers, universities, court records and any other avenue available.

I've been able to find a little bit on dust that was used in the trials for some of the 1970s FALN bombings in NYC. There's dust info on the 75 bombing at LaGuardia, the 81 bombing at Kennedy, and a lot of dust info on the 93 bombing at the Trade Center. There's also dust analysis of the radical bomb factory explosions in Sunset Park and Bed-Stuy in Brooklyn and one in Newark.

Bomb residue was also found in 87 under the FDR Drive. Quite a story in fact; no explosion on or under the highway, but trace evidence of a bomb explosive was found. A sink hole opened in the roadway near the UN just before Thanksgiving. Repair crews found that portion of roadway was one of the sections built upon the rubble of London. Seems that ships that brought supplies to England during WW2 used the rubble from the London bombings as ballast for the return trip and that rubble was used for the roadway. The crews thought that oil, possibly from the Astoria powerplant across the East River or from a down river depot, might have contaminated the soil so they took samples of the roadbed. The samples didn't contain any oil at all, just bomb residue - and 40 year old residue at that.

I'm looking, but I can't seem to find any study, report, or info of any kind that shows explosives or bomb residue was found in the Trade Center dust. Where is it?

[Abe Linkman]

17. About the dust from WTC 7

WTC 7 came down in a fashion that makes it almost certain it was imploded.

What is the Choir leader's opinion of why WTC 7 was imploded? Does s/he believe it had anything to do with the large number of sensitive tenants in the building and the information they had in their possession?

[demodewd]

18. Just curious

...do you know what floor the fuel tanks were located on?

[LARED]

19. My opinion

WTC 7 is the unusual failure without a doubt. I believe it failed in the way it did due to the unusual design of the structure (large open spans in the lower levels) and the large quantity of diesel fuel stored in the building. I know it's a mundane answer with no deep dark conspiracies to kindle political passions, but that's how I see it.

BTW, you are far to kind to say I am the leader of the choir. I'm more of a technician.

[Abe Linkman]

21. It "failed"? That's a good one.

Have you used that one anywhere else or is it an exclusive developed just for WTC 7?

[gandalf]

5. Conclusions?

Thanks for your effort, LARED.
What are the conclusions you draw from this report?

[Abe Linkman]

7. Too early for conclusions

You can divert attention away from what actually happened on 9/11 (for a very long time, apparently), by having endless debates about chemistry etc.

What's next? A cooked-up "debate" about weather conditions on 9/11 and how they could have affected/distorted the images of the WTC as seen on TV?

[plaguepuppy]

9. Never too early for the professional spam-slingers

When you're not encumbered by an interest in the truth it's easy to jump to conclusions.

It's no use trying to talk sense to this lot - they just keep repeating the same lines over and over, larded with thick layers or contempt and sercasm. Goose it up with slick logos and lots of pathetic little emoticons and poof - you too can be a debunker.

How many times have we heard the enormously self-important lard-boy assert as proven fact that "only a little" of the concrete in the towers was pulverized, with no evidence to back it up? It's our old friend the Big Lie - just repeat it over and over with great self-assurance, ridicule and insult those who don't agree with you, and a lot of people will assume you know what you're talking about. It works for Bush and the Rethugs, and it works for their apologists and protectors like lar-baby. Don't for a minute think he doesn't know what he's doing.

[LARED]

8. Conclusions

The myth that the energy required to create the dust cloud could not have been provided by the available gravitational energy available is just that, a myth.

The data indicates that the non-fiber materials makes up on average about 45% of the mass. Of that 45%, some percentage is from the concrete and the rest comes from other non-fiber sources. Sticking my thumb in the air and estimating what other non-fiber sources were available I'm going to guess the concrete makes up somewhere between 25% to 50% of the 45% percent. So that means that of the total materials in the samples concrete made up 15 to 25% of the total.

The percentages also indicates that not all the concrete was pulverized. 40% of the mass is glass fiber, mainly from insulation materials I assume. How could concrete that makes up a lower percentage in the sample than the glass fibers, and is much harder to pulverize, and is far heavier than glass fibers, be completely pulverized and make up a far smaller percentage of the mass. It can't. What percentage of the concrete was pulverized? What percentage was small, larger, and big chucks? Who knows. Photographic evidence indicates to me that there were plenty of small sized concrete piece strewn all over the area. Keep in mind the volume of the concrete above grade only makes up something like 3% of the towers volume. So not seeing piles of concrete is not entirely unexpected.

[plaguepuppy]

10. Using "conclusions" very loosely

How exactly does this prove that most of the concrete wasn't pulverized? This kind of mumbo-jumbo is enough to give sophistry a bad name.

"How could concrete that makes up a lower percentage in the sample than the glass fibers, and is much harder to pulverize, and is far heavier than glass fibers, be completely pulverized and make up a far smaller percentage of the mass."

Based on a grand total of three samples of dust you can magically conclude that? Based on estimates made by "sticking your thumb in the air"? Your hostility and arrogance can only get you so far, and I believe you've reached that point.

[LARED]

11. Those are the

conclusions I get out of the report. It's called interpreting hard data, real evidence. Something the conspiracy believers do not have to back up their theories.

So rather than engage is hand waving and name calling, why not state what you think the analysis tells us.

Your analytical mind is practically worshiped by your co-believers. I think you should sure up your status as the DU resident scientist by showing how this data helps your viewpoint along.

[gandalf]

13. Your statement concerning energy was no conclusion, just a statement

I think a conclusion is, indeed, that not all of the concrete was pulverized. That is what you call “interpreting hard data”, along with one assumption (the share of concrete within the non-fiber mass).

However, nothing about the energy is said that is necessary to pulverize the concrete.
So, your opening statement “The myth that the energy required to create the dust cloud could not have been provided by the available gravitational energy available is just that, a myth” is not supported by your interpretation of the data.
Could you please provide an interpretation of the data, some calculations or so, to support your myth-statement?

[DeadBroke]

12. Estimate headache

The problems I am having with theories focusing on the dust cloud; it’s contents, and what it may or may not reveal in regards to the cause of the collapses, are the estimates being used for the volume of concrete and fireproofing.

As previously stated, I had several occasions to work at the Trade Center, and from my experiences I am unable to accept the 4 or 5 and etc inch estimates for the thickness of the concrete floor. I installed doors, office module partitions, and miles of fixed and movable files and shelves. I must have drilled hundreds of holes into that concrete and pounded just as many dyna-bolts and other expanding fasteners into those floors, and I can attest to the unusual “thinness” of the floor. I seriously doubt the floor was 4 inches thick, and I also doubt that it contained the typical amount of rebar. One always hits rebar or wire mesh whenever drilling into concrete, but rebar hits were few.

The estimates for the thickness of the fireproofing are also too high. Whenever a renovation project is underway ALL the trades involved use a common benchmark; usually determined by an engineer, and usually 4 feet above the finished floor height.
The benchmarks are placed on columns, etched into the steel or scribed into brightly colored paint marks. The fireproofing, in small patches, is removed for placement of the marks. Everyone works off the same marks, it’s the only way everything will match. Sometimes you will need a benchmark where one has not been provided, so you look for an old one by scraping the fireproofing, just a small patch, away from the column. The fireproofing on the columns wasn’t as thick as is being estimated. The fireproofing wasn’t thick anywhere; and it comes off easy, with a pocketknife or small tool.

[DeadBroke]

14. And ...

... when I look back at the 2-26-93 bombing in the parking garage beneath the Vista Hotel I see that the 1,000 pound nitrourea bomb created craters or holes measuring; a) 400 square feet in the Vista's ballroom, b) 5,000 square feet on B-1 level over the position of the Ryder van, and c) a 130 X 150 foot L-shaped hole on B-2.

According to newspaper interviews a few of the first responders from the fire and police departments initially thought the missing and blown away sections of concrete floor were (in their own vernacular) pulverized, but after pumping water from the lower levels (B-3,4 etc) they found that most of the concrete from those aforementioned craters had fallen into those lower levels in pieces large enough to break water supply lines, cut electrical supply lines, and damage generators and air handling units. Whatever dust that was recovered from the upper levels had measurable traces of the bomb residue.

Now, I really want to understand everything being said in these threads. I'm reading everything and will admit that I at times have had trouble with many science terms. I really need replies that explain - please help.

Question: If a 1,000 pound nitrourea bomb created the above square footage of damage to the concrete floors of the parking garage what size and type of explosive device - and how many would be needed to create the collapse and pulverization cited in the theories being used in these threads.

[LARED]

15. Question

Is it possible that the 4" specification from the floor is the depth from the sheet metal pan to TOC would allow areas where the ridge in the floor pan would make the slab very thin for a short section. See, in looking a the available images of the floor pans they do look like the ridge area is quite wide. Could that explain you experiences?

Also, do you have any knowledge as to the type and strength of concrete used? Based on what you say, it seems like it had a filler in it to make it lighter.

BTW, thanks for the first hand infomation.

[DeadBroke]

16. My best answer

In my conversations with ironworkers who were employed at the Trade Center the majority of the floor sections, for speed mostly, were precast off site. The corrugated decking was welded to the top chords of the trusses, laced with rebar, covered with concrete, sent to the site by barge and on oversized load trailers, and then raised into position. Fast, yes but it also gave the Trade Center unusually level floors.

I always got different answers whenever I asked anyone about the ‘official’ thickness and about the consistency of the floors. Looking at corrugated decking one sees that it’s just a piece of thin flat steel given strength by the shape stamped into it; a series of troughs and rises. The concrete poured into it follows that shape, so the thickness of the concrete varies from thin above a rise to it’s thickest in the trough. Concrete has no strength. Rebar gives the floor its strength. It must be centered in the concrete slab to perform properly so pre bent steel bars are used to support the rebar and keep it centered. “Low boys’ hold rebar up off the bottom over the rises and “high chairs” are used in the troughs.

It is in this area that confusion exists. Which thickness; that over the rise, or that in the trough is the actual thickness of the floor? Commonly, and in the most general terms the trough dimension is used, but some architectural sketches and details also show and make provisions for the thinner dimension over the rise. Either way a 50 foot wide floor, for example, that is 6” thick is actually only 6” inches thick for half that 50 foot width.

When drilling into the floors of the Trade Center we were most often required to use 2 inch long dyna-bolts, strong fasteners ¼ inch in diameter that have an expanding sleeve on one end and a threaded shaft on the other. A washer and nut fits on the threaded shaft and when tightened it draws the bolt though the sleeve and sets it fast in the hole. I’m certain that the architects and engineers chose the 2” length so that the end of the bolt would be fastened into the center of the slab.

Drilling must be done carefully. It’s easy, real easy, to drill too deep and break through the bottom of the decking. One or two holes like that may be overlooked, but too many will compromise the fire rating. Drilling also must be done carefully because the bit will hit that rebar buried in the concrete and get stuck. The bit stops turning and the drill machine starts spinning. A person using the drill machine can experience wrist or hand injuries from the bit jamming and the drill machine spinning. When rebar is hit another hole must be drilled. Sometimes that’s impossible. A “smart” foreman knows that 2” will not work everywhere so he keeps a small cache of smaller bolts, perhaps 1 ½ or 1 long to “cheat” so to speak. I cheated a lot.

That’s one reason why I am certain that the estimates for the thickness of the concrete floors being used are off. I drilled too many holes and cannot accept the 4, 5, and 6 inch numbers. Another reason was the Port Authority’s Contract Library. It was two floors and had a staircase connecting them. A steel rolling fire door manufactured by Overhead Door of Pennsylvania and maintained by the MacKenzie Group on nearby Reade Street protected the stairwell. An opening in the floor had to be cut to install the stairwell and it’s thickness, rebar and other components were visible during that process. Another reason is noise. Drilling’s noisy; and building tenants always complain, but the sound traveled much easier and was louder at the Trade Center, so unlike other places it could only be done off hour. Powder actuated fasterners; pins shot into concrete with a firearms type cartridge, a fast easy and solid way to fasten into thick concrete, could not be used at the Trade Center. Finally, some building components such as transformers or heavy power or mobile aisle shelving units need 3/8” diameter or larger floor fasteners longer than 2” and whenever than was required a secondary slab had to be poured.

[plaguepuppy]

22. Welcome back & thanks for the 1st hand info

Based on what you saw doing the door for the contract library what range of thicknesses did the floor actually show? Was it at least 2" above the tops of the ridges? And offhand do you know what kind of aggregate they used? I get the impression that cinders are commonly used as a lightweight aggregate, but have never found anything specific about the WTC. And just for jollies, I don't suppose you came across any record of testing for explosive residue on anything at the WTC site?

As to the original question of what can be concluded from the samples of dust in article Lared posted, I'd have to say that the three samples don't offer a meaningful basis for concluding anything about the overall composition of the dust cloud for a number of reasons. The location closest to the site was obtained from "protected external ledges," meaning that they were covered from above at some height. This will immediately bias the sample against denser particles that will tend to fall more nearly straight down, and in favor of lighter particles that will drift in from the sides. Without knowing the size and height of the "protecting" surface above the ledge it is difficult to judge the degree of bias, but the potential effect is quite large.

The same concern applies to the other two sites, since the cars are described as being in locations "protected from rain." The fact that these sites are further away from the WTC (~.7km) will also introduce a bias against denser particles, which will tend to settle out more quickly. This is similar to the graded beds that are created in turbulent flows of gravel carried by water - the bigger pieces settle fastest, winding up at the bottom of the bed or closest to the source of the flow, with progressively finer stuff (sandstones, mudstones) above it.

Even if these were more representitive samples it would be very dubious to try to infer anything about the total amount of concrete that was pulverized or even to estimate what percentage of the dust cloud it represented. And since we know nothing about the absolute volume of dust created that percentage still wouldn't tell us much.

Remarkable feat of the month: Note that Lared's first snarky reply to himself bemoaning the lack of response to his posting is actually dated *earlier* than the original post!

Wed Aug-20-03 12:27 AM
Original message

Wed Aug-20-03 11:53 AM
Response to Original message

I think we have a new record!!

[DeadBroke]

23. Unusually thin, but

Even though it struck me as being unusually thin I never actually measured the thickness of the exposed floor. At the time it didn’t matter, but thinking back, I’ll say that 2” over a ridge is generous. I am pretty sure that the rebar was #5. Rebar is assigned a number based on the 1/8s it has in its diameter – a #5 has 5 eighths and is 5/8 in diameter. It also wasn’t the corrosion resistive epoxy or plastic coated rebar used today; it was just plain steel.

The concrete didn’t appear to have any large pieces of aggregate in it. Usually, when concrete from that era of construction is cut with a wet saw, as it was in this case, the saw also cuts right through the large 25 cent quarter sized gray-black crushed stone or the white-yellow gravel that’s used for aggregate and it’s all very visible. There were no pieces that large.

I will admit that I don’t know a whole lot about concrete, but I believe I have been around heavy construction long enough and have seen enough to know a little about concrete, it’s aggregate and the practices of the trades involved. As I stated before, a few months ago, it’s general practice for contractors to hire inspection firms to monitor the building process. I believe I explained the welding and fireproofing inspections. For concrete they’ll do the slump tests on each load of concrete that’s delivered, take samples, record temperature and do other quality checks before accepting or rejecting the load. They will also take core samples, and actually drill cores out of random sections of floor that have dried and begun curing. Those samples are sent to labs and checked for strength and composition. The first thing that’s checked on a core sample, while it’s still on site and even before it’s tagged and sent to the lab, is the position of the aggregate. If it’s all at the bottom the masons over-vibrated the pour. Concrete has to be vibrated so that it fully encapsulates the rebar and fills every nook and cranny. Too much vibrating causes the aggregate to sink to the bottom.

Now-a-days thin white nylon fibers have replaced stone, gravel and cinder on ‘lightweight’ concrete. These fibers are hair like, very thin, but nearly invisible, so small amounts of special colored fibers, usually a different color every concrete load, is added to the mixing truck for the core test to be conducted properly.

I don’t know a whole lot about concrete, and I’m no expert, but I do know I didn’t see any large pieces of aggregate or any substantial thickness.

I also had occasion to visit a motor room floor. In my opinion, the concrete on the motor room floors must have been very thick, 8 – 10 inches thick at least, to allow for the long and heavy ½ inch and larger fasteners that held the air handling units, fans, transformers and heat exchangers. If the Trade Center had motor room floors like other tall buildings the floor also had more and larger sized rebar. That’s really just a guess, but a safe guess.

In response to your question about my still ongoing dust analysis search I have not found anything confirming bomb or explosive residue from the 9-11 event. There is a lot of speculation, mountains of it in fact, but nothing that confirms it like the other events I have mentioned in this thread. I'm still looking.

In my numerous discussions with ironworkers employed at the Trade Center during the original construction period I have learned that one of the links offered in these threads:

http://misternet.org/nerdcities/WTC/WTC_ch5.htm

has an inaccuracy that may be causing some confusion.

In Section 5.2.2. Structural Framing there is a click here link just above figure 5-4 that brings readers to the truss controversy. The writers are correct that there are beams, not trusses, in the photos shown; but those beams are not typical of the floor framing that was used, and those beams were only used in the ‘belly bands’ of the building, not from bottom to top.

‘Belly bands’ is structural slang for sections of a structural steel building, and should not be confused with the ornamental and architectural belly band term for the wood molding nailed horizontally to wood frame houses. In structural steel frame construction certain floors are selected for extra reinforcement, more steel (in this case beams instead of trusses) and thicker concrete. Those ‘belly bands’ will usually divide the building into sections helping the structure dampen wind load and also allow for the creation of motor rooms. From talking with ironworkers that worked there those are ‘belly band’ beams in the pictures and were not typical of the floor system; the Trade Center had a half dozen or so belly bands in each tower.

Yes, those are beams and not trusses; but it's a mistake, and probably an honest one, to see them and think they were typical through the structure.