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Author Topic: Does Concrete Melt ?  (Read 51942 times)

Offline CliffordK

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Does Concrete Melt ?
« Reply #25 on: 21/08/2011 21:02:31 »
You can buy rock wool insulation. 

In St. Louis, the building inspectors are requiring people to buy the Rock Wool and stuff it into cracks in penetrations between levels in the house because it is not flammable.  However, fiberglass wouldn't be flammable either unless something like resin or tar is added to it.  I tried burning firestop spray-foam once, and it burned quite nicely.
 

Offline Geezer

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Does Concrete Melt ?
« Reply #26 on: 22/08/2011 08:06:17 »
I'm sure the rare mineral that my garden is made of is of remarkable purity and consistency, and is therefore incredibly valuable. If only I knew people with geological and chemical credentials who could attest to this.
 

Offline daveshorts

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Does Concrete Melt ?
« Reply #27 on: 22/08/2011 10:13:12 »
Certainly at atmospheric pressure concrete would decompose - it contains calcium hydroxides which would decompose to calcium oxide, essentially it would go back to dry cement. It is possible what is then left may melt eventually as there are quite a lot of silicates in there so would form something like a very basic lava.

Glass fibre won't burn certainly, though fibreglass often refers to GRP (glass reinforce plastic) and the plastic will definitely burn.
 

Offline Mazurka

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Does Concrete Melt ?
« Reply #28 on: 05/09/2011 11:18:08 »
Speculating somewhat - but in relation to the decomposition back to calcium oxide:  The hotest fires tend to be those where oxygen is restricted.  In suchg a aituation would calcium hydroxide decompose?  What effect would the age of the concrete have - older concrete has a greater amounts of Calcium Carbonate, where CO2 has replaced the OH?

OK dolomitic limestone has a lower melting point than either (purer) calcium carbonate or silica - so could the aggregate type have an effect too?
 

Offline Bored chemist

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Does Concrete Melt ?
« Reply #29 on: 05/09/2011 19:32:01 »
"The hotest fires tend to be those where oxygen is restricted. "
What?
 

Offline Geezer

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Does Concrete Melt ?
« Reply #30 on: 06/09/2011 09:05:31 »
"The hotest fires tend to be those where oxygen is restricted. "
What?

Perhaps Mazurka is suggesting that excess oxygen in relation to available fuel will remove heat and lower the temperature.
 

Offline Mazurka

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Does Concrete Melt ?
« Reply #31 on: 06/09/2011 11:32:15 »
Sorry, I was not clear - the Geezer is right - in flare stacks on landfill sites (my main experience of high temperature fires) it is critical to get the ammount of air flow through to get the an adequate retention time at sufficient temperature to oxidise/ burn "pollutants".

The sorts of scenario I was envisaging are tunnel fires, where extraordinary temperatures are reached as burning fuel etc consumes the oxygen, thus depriving the calcium hydroxides and carbonates decomposing back to calcium oxide.

it was not my best articualted thought ot post i have made onthei forum [:0] 
 

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Does Concrete Melt ?
« Reply #31 on: 06/09/2011 11:32:15 »

 

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