Does concrete melt?

Status
Not open for further replies.

qed

Senior Member
[:sigh:] How did I know that was coming?

melt: to change or to cause (something) to change from a solid to a liquid usually because of heat
Content from External Source
http://www.merriam-webster.com/dictionary/melt
  • Concrete melts and forms "lava" (molten rock). At 1500C it will melt entirely.
  • When it hardens, an igneous "rock" results.
To argue that concrete does not melt because in molten form it is not concrete, is to argue that a cell-phone won't melt, because the resulting liquid is not a cell phone, since when it hardens it won't be a cell phone no more, Jim. Chewing gum melts, but try chew it when it hardens, it won't be chewing gum.
 

Mick West

Administrator
Staff member
I should have been more specific; does iron ore melt?

Yes it does. Simply melting iron ore (hematite, for example) does not turn it into iron and oxygen, any more than melting salt turns it into sodium and chloride.

Things have different reactions to heat.
 

Mick West

Administrator
Staff member
[:sigh:] How did I know that was coming?

melt: to change or to cause (something) to change from a solid to a liquid usually because of heat
Content from External Source
http://www.merriam-webster.com/dictionary/melt
  • Concrete melts and forms "lava" (molten rock). At 1500C it will melt entirely.
  • When it hardens, an igneous "rock" results.
To argue that concrete does not melt because in molten form it is not concrete, is to argue that a cell-phone won't melt, because the resulting liquid is not a cell phone, since when it hardens it won't be a cell phone no more, Jim. Chewing gum melts, but try chew it when it hardens, it won't be chewing gum.

I explained it many posts ago, in answering your question "will concrete melt?"

Not really. Some of the components of concrete (like rocks, basically) will melt at a high enough temperature. But at that point it's no longer concrete.

Really high temperatures destroy concrete, and what's left over can melt. But there's really no such thing as molten concrete.

You are arguing semantics. So use different words to make your point.

What is your point?
 

qed

Senior Member
What term should we use for the phenomenon "concrete turns to "lava" under heat"?
 

Mick West

Administrator
Staff member
I have explained in great depth what happens to concrete when it is heated. Y'all want to reduce this to a semantic/rhetorical argument over the word "melts".

Please try to make a genuine point, not just "score" points.
 

qed

Senior Member
Will members be disputed in future when they talk about concrete melting?

Will it be understood that we mean turn to "lava"?
 

gerrycan

Banned
Banned
I have explained in great depth what happens to concrete when it is heated. Y'all want to reduce this to a semantic/rhetorical argument over the word "melts".

Please try to make a genuine point, not just "score" points.
The NFPA states 'molten concrete'. They don't play semantics or try to score points. They are experts in this field.
 

Mick West

Administrator
Staff member
Will members be disputed in future when they talk about concrete melting?

Clarifications may be offered, with reference to this handy thread.

"Melt" and "molten" are tricky words for the average joe, it's best to say exactly what you mean.
 

gerrycan

Banned
Banned
I just made some toast. I put cheese on top of the toast once i had toasted one side. I dare say that in the process of the cheese melting, it may have lost some moisture and who knows what else. It's still cheese though. You could say the same thing about most materials and melting I would think, they lose something to the atmosphere as they melt, whether it's cheese, plastic, concrete or whatever else.
 

qed

Senior Member
I think all the essential points of all side have been well-argued and it is time to close this thread.
 

gerrycan

Banned
Banned
But what's the underlying point? Or are you just arguing semantics?
I guess given that these threads are all about 911, then the kind of damage that was observed in the building elements afterwards would have warranted that the investigation remit was such that exotic accelerants should have been tested for in the residue as per the NFPA guidelines. If this had been a house fire, they would have tested.
 

Mick West

Administrator
Staff member
I guess given that these threads are all about 911, then the kind of damage that was observed in the building elements afterwards would have warranted that the investigation remit was such that exotic accelerants should have been tested for in the residue as per the NFPA guidelines. If this had been a house fire, they would have tested.

Was there rapid fire growth? Was there molten decomposed concrete?

It's really not that common. NFPA hardly ever looks for it, and they have never found it.

22.2.4.1 Exotic accelerants have been hypothesized as having
been used to start or accelerate some rapidly growing fires and
were referred to in these particular instances as high temperature
accelerants (HTA). Indicators of exotic accelerants include
an exceedingly rapid rate of fire growth, brilliant flares (particularly
at the start of the fire), and melted steel or concrete.
A study of 25 fires suspected of being associated with HTAs
during the 1981–1991 period revealed that there was no conclusive
scientific proof of the use of such HTA.
Content from External Source
Anyway. Concrete, it kind of melts, depending on your definition, but it's more complicated than that.
 

Mick West

Administrator
Staff member
That can't be molten concrete, as the steel rebar did not melt. And it does not look in the least bit glassy. Just just compacted debris.
 

Oxymoron

Banned
Banned
That can't be molten concrete, as the steel rebar did not melt. And it does not look in the least bit glassy. Just just compacted debris.
The 'rebar' is whats left of column 79... it got embedded in the molten concrete as it was cooling a month later. :)
 

gerrycan

Banned
Banned
That can't be molten concrete, as the steel rebar did not melt. And it does not look in the least bit glassy. Just just compacted debris.
Just to be clear Mick, you think that this fusing is caused by pressure and not heat?
Sorry I couldn't find a better video of it.
 

Trigger Hippie

Senior Member.
I love these forums because they often force me to examine things I take for granted. For instance, what is "melting"?

Joyce Cheng, in an article called "Can You Melt a Wooden Log?" defines melting as the process a substance undergoes during the phase transition from solid to liquid while its chemical makeup remains unchanged. By that definition ice, iron and cheese melt... wood, cell phones and cement do not.

But what about butter? Butter is said to melt. However, when it re-solidifies it never really looks quite the same as the original. So then can we truly say that butter melts? And if it doesn't melt, should we be using butter instead of cement to build our skyscrapers?

Hmmm... butter.
 

gerrycan

Banned
Banned
Likely a combination.
The thing is, considering the amount of concrete we are talking about per tower (80-90k tons), there weren't that many large chunks of concrete in the rubble pile to exert the kind of pressures this would take if indeed pressure could do this. Is it not more likely that the cause of the molten concrete were the intense underground fires that raged for weeks on end at ground zero?
 

Mick West

Administrator
Staff member
The thing is, considering the amount of concrete we are talking about per tower (80-90k tons), there weren't that many large chunks of concrete in the rubble pile to exert the kind of pressures this would take if indeed pressure could do this. Is it not more likely that the cause of the molten concrete were the intense underground fires that raged for weeks on end at ground zero?

A) Why do you need large chunks of concrete to exert pressure?
B) What molten concrete?
C) More likely than what?
 

gerrycan

Banned
Banned
A) Why do you need large chunks of concrete to exert pressure?
B) What molten concrete?
C) More likely than what?
A) you don't, so what else could have exerted the pressure?
B) The molten concrete in the big picture and video.
C) More likely than the building elements.
 

Mick West

Administrator
Staff member
A) you don't, so what else could have exerted the pressure?
B) The molten concrete in the big picture and video.
C) More likely than the building elements.

A) Rubble, girders, columns, and suchlike.
B) It's not molten.
C) Nobody said "building elements" caused molten concrete.
 

gerrycan

Banned
Banned
A) Rubble, girders, columns, and suchlike.
Would they only cause it at the lower end of the collapse then?
B) It's not molten.
Previously molten. Have you seen the pictures of the melted guns that the city of NY put on display?
C) Nobody said "building elements" caused molten concrete.
That's good, because they don't, unless the building in question is made of some very exotic and unusual elements.
 
Status
Not open for further replies.
Top