[port rhombus]

Perhaps some of you fine people are able to help me.

I'm trying to investigate something and Google ended up not being much help specifically, although it did lead me here.  I make no bones about the fact that my Chemistry knowledge is not great and that some of my questions might actually be incredibly stupid.  I apologise for this and hope you don't hold this against me.  I am merely trying to understand something.

Basically, i'm trying to find out about cement and crystallization.

It starts with this sentence;

"The huge dust cloud which blew out ....was cement and other materials which had been crystallized."

Now from my limited understanding it seems that the person that wrote this has mi-used the word 'crystallization', instead meaning to refer to the pulverisation to dust of something.

I assume that it is possible to pulverise something to dust so...., under what circumstances could this be induced?  Specifically on a large structure that consisted of thousands of tonnes of cement, concrete and steel.  Could a building collapsing by itself provide enough energy to pulverise the cement/concrete that it consisted of?

I have a few other questions, but that is dependant on the answers to these questions.

Thanking you in advance for helping, i hope this does not come across as a ridiculous post.  This is not homework or anything, it is connected to something i am 'looking into' shall we say.

Thanks again.

Richard

[Borek]

Could a building collapsing by itself provide enough energy to pulverise the cement/concrete that it consisted of?

Not all, but enough of the concrete gets pulverized to create a large cloud of dust. See any film of controlled demolition. Note that WTC case was slightly different - dust cloud was in large part made of gypsum from partition walls, while in the controlled demolition everything that can be removed is removed from inside of the bulding before explosion.

[port rhombus]

Not all, but enough of the concrete gets pulverized to create a large cloud of dust. See any film of controlled demolition. Note that WTC case was slightly different - dust cloud was in large part made of gypsum from partition walls, while in the controlled demolition everything that can be removed is removed from inside of the bulding before explosion.

Hah.  I thought i had hidden what i was talking about.  Obviously not very well  

So basically, the cloud produced was due to the building itself and not because of any other 'interfering' sources?  Also, you mention gypsum, i don't suppose you have any sources for this that corroborate both these things?  It's not that i don't believe, but it's good to have a reference point.

Thanks for your help.

[Borek]

Well, thats only guess, call it educated if you want.

Partition walls are made of gypsum wall boards (no idea if it is a correct name in English) . When the WTC was collapsing floors/ceilings were falling one by one pressing and crushing everything between. GWB in such circumstances become fine dust immediately and the dust is blown out by the pressure produced by falling floors/ceilings. It is as simple as that. At the same time concrete was also crushed and blowed out, but my feeling is that the dust cloud contained more gypsum then cement, as gypsum is much easier to pulverize. I can be wrong on this one.

We have discussed dust cloud size several months ago here, althought there were more emphasis on the explosives used in the demolition - try here. Note that the thread was looooong and only partially devoted to dust

[port rhombus]

Thank you.  Your educated guess does make a lot of sense and the link you provided was an interesting read.

Thanks for your help.