Article is five years old. Subject matter greatly expanded since. Nothing subjective about it any more, it is quite definitive. CO2 reacts with Fe in steel reinforcement causing expansion and cracking.
Oh, no! We're all going to die!
Wait a moment, perhaps we aren't:
Carbonation of concrete is associated with the corrosion of steel reinforcement and with shrinkage. However, it also increases both the compressive and tensile strength of concrete, so not all of its effects on concrete are bad...
I feel immortal already!
John
Some businesses are capitalizing on CO2 curing of concrete. Drawback is there needs to be a big CO2 emitter nearby.
You missed the point. Carbonation has to be carefully dosed to improve the structural properties. Uncontrolled carbonation leads to cracking and failure. The structure is nothing without the rebar reinforcement.
The real question you are asking then is, does the increase of CO2 in the atmosphere adversely affect concrete?
Are there any double-blind studies? Or is this all just supposition?
As I see it the more likely risk/problem is more along the lines that you are at greater risk from bridges that are made from contractors who cheat about the mix, rebar quality, etc, and engineering mistakes then you ever are from environmental issues having a serious negative impact.
Modern bridges tend to last less than 100 years. Yet the Romans made concrete that has lasted over 2,000 years - I'm just not going to worry.
John :-#)#
hing subjective about it any more, it is quite definitive. CO2 reacts with Fe in steel reinforcement causing expansion and cracking.
te-corrosion/
sthe structural properties. Uncontrolled carbonation leads to cracking and f ailure. The structure is nothing without the rebar reinforcement.
Roman concrete wasn't reinforced with steel bars. The idea of adding reinfo rcement to deal with tension loads only goes back the the Renaissence, init ially wooden beams clamped together with iron fittings, then iron chains, a nd the first reinforced concrete structure wasn't built until 1853.
We could use non-corroding reinforcing bars, but modern structures get revi sed frequently enough that it probably isn't cost-effective.
-- Bill Sloman, Sydney
The implications of even a 4 degree rise in average temperatures are pretty devastating for human-civilization-as-we-know-it, yeah.
Right, that is indeed correct. The theory the OP was making was that the rebar is deteriorating more quickly leading to potential failures.
I've seen too many stories of contractors cheating on the quality of materials to worry much about a theory that increased CO2 is leading to shorter useful life. As you say many rebar cement structures are taken down long before they reach end-of-life.
Heck salt kills more bridges than just about anything else.
John :-#)#
Well, yes, that would not be good, however that is not looking very probably these days, is it? All the wolf cries of the 80s and 90s has not come true, so they have scaled things down a lot.
They aren't calling it Global Warming any more - or hadn't you noticed? Climate change allows for anything to happen and then you can blame it on humans.
John ;-#)#
The IPCC predictions from that period look to have been slightly on the conservative side.
You seem to be recycling the "global warming stopped in 1998" mantra.
A particularly intense El Nino pushed up the global average temperature in 1998, and it took seven years of global warming to get the temperature that high again.
John Robertson seems to be another sucker for denialist propaganda.
-- Bill Sloman, Sydney
Oh my! The latest climate scare of the week! Next week it will be that the peat bogs in Scotland are drying up, threatening the world's supply of Scotch!!
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conservative side.
p-1998
in 1998, and it took seven years of global warming to get the temperature that high again.
d?
te peat bogs in Scotland are drying up, threatening the world's supply of Sc otch!!
Anthropogenic global warming is already having a wide range of effects, and as we get more of it, even more consequences become visible.
Journalists do like to present them as the scare of the week - their busine ss is essentially getting the reader's attention - but it is actually a ser ious issue, somewhat complicated by the fact that some very rich people are going to become less rich when we start taking it seriously.
We should be able to slow it down without making the population as a whole less well-off, but the people who will become less well-off have a vested i nterested in not slowing it down.
-- Bill Sloman, Sydney
err... no, this isn't scare 'of the week', it's at leastt thirty years old. Will go on for the rest of the century, and if you don't want timely updates, just get some of those dark peril-sensitive glasses (like in the Infocom kit with their Hitchhikers' Guide game).
Not a Scotch fan myself, but when the Jim Beam warehouse made the sky light up, I made sure to top up my stock ahead of the expected drought.
You can't soften the blow if you don't see it coming.
It's been called Climate Change since at least the 80s - or hadn't you noticed? Evidence of that is in the name of the Intergovernmental Panel on Climate Change (IPCC). That body was established, with that name, in
1988.-- remove sharp objects to get a valid email address
hing subjective about it any more, it is quite definitive. CO2 reacts with Fe in steel reinforcement causing expansion and cracking.
te-corrosion/
sthe structural properties. Uncontrolled carbonation leads to cracking and f ailure. The structure is nothing without the rebar reinforcement.
LOL- there is no supposition to it. This has been known for a while now. Th e industry moved from bare steel to epoxy coated rebar. The coated rebar is problematic in that it needs to be handled with kid gloves to prevent dama ging the coating, and then it needs to re-coated when its sheared to fit or damaged by jobsite bending. Steel has pretty much given way to FRP rebar, which is fiber reinforced polymer material. It is actually cheaper than ste el, however the job typically requires 30% more of this type than steel, an d that translates into additional labor.
That reasoning is a false dichotomy. Generally component risks are not disc ounted to prioritize another risk that is slightly more disastrous and less probable.
That was from an era when using hundreds or thousands times more material t han necessary was no big deal. It would be nearly 1700 years before scienti fic study of strength of materials was undertaken.
You're confusing the infotainment presentation of the media for the masses with the serious drudgery being undertaken by the huge numbers of scientific personnel working on the issue.
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othing subjective about it any more, it is quite definitive. CO2 reacts wit h Fe in steel reinforcement causing expansion and cracking.
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e the structural properties. Uncontrolled carbonation leads to cracking and failure. The structure is nothing without the rebar reinforcement.
. .
forcement to deal with tension loads only goes back the the Renaissence, in itially wooden beams clamped together with iron fittings, then iron chains, and the first reinforced concrete structure wasn't built until 1853.
vised frequently enough that it probably isn't cost-effective.
And the profession moved away from the arch, a structure pretty good at kee ping everything in compression,
All popular "climate scares" like the "global cooling" one were pretty much entirely circular viral beat-off sessions of the game "Telephone" where the media referenced scientific papers that didn't say what they said they did, the media perception was then referenced in scientific papers, other media referenced the second set of papers to "prove" their original false claims, and so forth.
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