prole - 2-10-2006 at 09:38
Not sure where to put this one. I work with a guy, whose word I trust, who told me the following: He's got some concrete patching to do because a
year ago, he had a new driveway poured (concrete). He came out of the house one day and saw smoke coming out of a hole in the then one month old
driveway. He looked closer, and dug out a nut, which had been embedded in the fresh concrete. There were actually two of these smokin' nuts in his
driveway. I'm thinking an acid/base rxn was at play here, generating some heat. He said it was smoke, and not water vapour, or 'steam'. He couln't
identify the 'nuts' that were smoking. I'm thinking acorns or hickory nuts, they're everywhere here. The driveway had been poured one month earlier,
so it may have still been curing. He's an old navy guy, not a science guy, so I had more questions than he could answer. WTF? Any body got some
insight?
12AX7 - 2-10-2006 at 13:31
WTF?
Nah, the cement is fully set in a month. AFAIK, only concentrated sulfuric can cause "smokin'" organics. Well, strong oxidizers, but besides that...
Tim
Elawr - 2-10-2006 at 19:01
I can come up with no mechanism to explain appearance of hole with smoke and presumedly, heat associated with nuts (as in threaded metallic fasteners,
I'm also presuming) imbedded within new concrete. Iron or it's lower oxides can be pyrophoric when finely divided, and when combined in sulfur and
H20 in sufficient mass could generate smoking heat. Maybe your neighbor has been tooting on the bong - this might be the more likely source for the
smoke! 
jimmyboy - 3-10-2006 at 00:00
smokin nuts huh?? this smells of troll so badly.. lol 
unionised - 3-10-2006 at 09:37
"He couln't identify the 'nuts' that were smoking. I'm thinking acorns or hickory nuts"
"I can come up with no mechanism to explain appearance of hole with smoke and presumedly, heat associated with nuts (as in threaded metallic
fasteners, I'm also presuming)"
An odd presumption.
I can imagine alkaline degradation of tanin like materials followed by oxidation as plausible but very unlikely.
prole - 3-10-2006 at 12:01
Yeah, I know this sounds freakin' stupid, but the guy was all animated when he told me about what he saw. Probably no bong in his house, but he's
been smokin' butts for more than 50 years, so there may be a lack of oxygen in his brain. Anyhow, I thought I'd post his story here to see if anyone
could explain this. So far, I've gotten the responses I expected.
evil_lurker - 3-10-2006 at 13:04
Organic material can spontaneously combust if given the right conditions.
Being a farmer I have seen bales of hay that were baled too green (or had a green spot in them) and subsequently caught on fire.
What happens is you get a slow oxidation going on... the material gets just enough O2 to heat up, but it can't get enough to fully catch on fire.
Its possible that the nuts could have had enough moisture in them for the reaction to start after a rain, but then again I don't see how they could
have gotten that hot because generally with spontaneous comustion materials you gotta have a "critical mass" i.e. enough material that it can't
dissipate self dissipate the heat for them to get going.
I say he's just crazy.
vulture - 3-10-2006 at 13:24
Meteor Shower?
indigofuzzy - 7-10-2006 at 02:32
On the spontaneous combustion theory, maybe the shell of concrete around the nuts was able to trap some of the heat?
Mr. Wizard - 7-10-2006 at 04:30
Was the space around the nut the same size as the nut, or was there a volume larger than the nut, perhaps caused by a ball of unslaked lime that
didn't get broken down in the concrete mixer?
prole - 7-10-2006 at 17:09
Mr. Wizard,
My friend said that there was a cavity about the size of a walnut shell, but the contents of the hole were badly burned, so the actual identity of the
'nut' will never be known, and he's already patched the holes. I told him about the responses I was getting from the good people here, and he
shrugged his shoulders. He doesn't care what anyone thinks, he knows what he saw. I wish he was as curious as I am about it. He did say that there
was an exit hole on the surface on the concrete where the smoke was escaping, so maybe some pressure forced the opening. I don't know. I feel my
credibility, what little I have here, is dwindling because of this, so I wouldn't mind if no one else responded to this thread. It was worth a shot.
thanks all.