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First, TFA is about cement, not concrete.
Second, common ingredients used in production of portland cement include limestone, shells, chalk, clay, etc. (though I'm guessing shells are not that common)
Third, the process of turning shells into portland cement includes using heat to disassociate and drive off water and carbon dioxide, so still not very green from an AGW point of view. (Though some carbon dioxide will be re-absorbed as the cement ages.)

Since the concrete production is centralized, it can be sequestered on site, and concrete naturally re-absorbs that carbon over the decades.

The same can be said for fossil fuel powered generators.

since concrete production is a mere 1% or so of total CO2 output by the US

Where does this number come from? All the articles I have seen put that number at 5% of world CO2 emissions.

concrete naturally re-absorbs that carbon over the decades.

How much does it absorb and what consequences?

So, how much calcium dioxide is absorbed in concrete and how long does it take? The answer is that we do not know.

Here is a quote from the article you referenced;

The exact amount of emissions depends greatly on site-specific characteristics. However, current estimates suggest that life-cycle emissions can be over 0.5 pounds of carbon dioxide equivalent per kilowatt-hour [5,6].

To put this into context, estimates of life-cycle global warming emissions for natural gas generated electricity are between 0.6 and 2 pounds of carbon dioxide equivalent per kilowatt-hour and estimates for coal-generated electricity are 1.4 and 3.6 pounds of carbon dioxide equivalent per kilowatt-hour [7].

The 0.5 pounds of carbon dioxide equivalent per kilowatt-hour for hydro is not one tenth that of the 0.6-2 pounds of carbon dioxide equivalent per kilowatt-hour of natural gas.

http://www.cement.org/homes/brief09.asp
According to the cement site, materials cost seem to not be that much more. Labor cost is almost double for normal concrete construction, but the pre-fab modular homes are not that much more. It seems quite feasable to shell out a bit more just so the home doesn't blow away each year. Why won't they do it in the hurricane and tornado prone areas?

When you add in insulation costs, it seems closer in price: http://www.cement.org/homes/ch_sb_solidinvest.asp
Since it's a cement site that did their own study, I doubt that it's that cheap. Even if it was 25% more, it's still a reasonable investment in hurricane & tornado zones. Something seems amiss in the mainland US mindset. It's probably why there's so many low quality Made in China junk in Walmart. I'd rather get something higher, quality and not have it break frequently.

Sure wood is definitely cheaper short term, but look at it long term. How often do you have to replace them each year. If the insurance companies were smart, they'd analyze the cost of concrete for those areas and the amount they'd pay long term. They already know the short term costs of constantly replacing homes during a hurricane. Maybe they have analyzed it and just make so much more short term money with the wooden structures and allowing the devastation and loss of life, that they wish to continue.

On the island of Guam, they get both 8.0+ earthquakes and up to Category 5 Typhoons(Hurricanes for non-US mainland pacific). After SuperTyphoon Pamela hit in 1976, homes were replaced with concrete. By the early 1980s they were pretty much all concrete. New homes there are all concrete and each new generation of new construction has better and easier to operate earthquake shutters. The buildings survive typhoons and earthquakes with minor, mostly cosmetic damage these days. No evacuations are required anymore. Everyone just rides out the typhoon in their homes. Granted, both wood and concrete have to be shipped to the island, but the heavier cement & gravel for concrete would still be a quite a bit more expensive to ship.

To make a concrete house look new, you just need to paint it and fix up the landscaping. I really don't see people tear down their house just to make it look new. For the internal walls, you can still use wood and reconfigure them quite easily. Only the exterior and load bearing interior structure has to be concrete. It's probably better, since some DIYer goof won't accidentally remove a load bearing wall and bring his own house down. The excuse for building with wood is just that, an excuse. There's lots of solidly built buildings that don't look old.

http://www.cement.org/homes/brief09.asp
According to the cement site, materials cost seem to not be that much more. Labor cost is almost double for normal concrete construction, but the pre-fab modular homes are not that much more. It seems quite feasable to shell out a bit more just so the home doesn't blow away each year. Why won't they do it in the hurricane and tornado prone areas?

When you add in insulation costs, it seems closer in price: http://www.cement.org/homes/ch_sb_solidinvest.asp
Since it's a cement site that did their own study, I doubt that it's that cheap. Even if it was 25% more, it's still a reasonable investment in hurricane & tornado zones. Something seems amiss in the mainland US mindset. It's probably why there's so many low quality Made in China junk in Walmart. I'd rather get something higher, quality and not have it break frequently.

Sure wood is definitely cheaper short term, but look at it long term. How often do you have to replace them each year. If the insurance companies were smart, they'd analyze the cost of concrete for those areas and the amount they'd pay long term. They already know the short term costs of constantly replacing homes during a hurricane. Maybe they have analyzed it and just make so much more short term money with the wooden structures and allowing the devastation and loss of life, that they wish to continue.

On the island of Guam, they get both 8.0+ earthquakes and up to Category 5 Typhoons(Hurricanes for non-US mainland pacific). After SuperTyphoon Pamela hit in 1976, homes were replaced with concrete. By the early 1980s they were pretty much all concrete. New homes there are all concrete and each new generation of new construction has better and easier to operate earthquake shutters. The buildings survive typhoons and earthquakes with minor, mostly cosmetic damage these days. No evacuations are required anymore. Everyone just rides out the typhoon in their homes. Granted, both wood and concrete have to be shipped to the island, but the heavier cement & gravel for concrete would still be a quite a bit more expensive to ship.

To make a concrete house look new, you just need to paint it and fix up the landscaping. I really don't see people tear down their house just to make it look new. For the internal walls, you can still use wood and reconfigure them quite easily. Only the exterior and load bearing interior structure has to be concrete. It's probably better, since some DIYer goof won't accidentally remove a load bearing wall and bring his own house down. The excuse for building with wood is just that, an excuse. There's lots of solidly built buildings that don't look old.

Their web site just screams "vaporware". In fact, the useful-scale project has been cancelled, and only a small "demonstration plant" will be built.

The real questions about this are 1) do they really get out more energy than they put in, and 2) how much processing of the exhaust gases is required? Westinghoue Plasma Corporation (which, sadly, has little to do with Westinghouse) claims that 1000 tonnes (metric?) of solid waste produces the energy equivalent of 1 (one) barrel of oil. So this isn't a big energy producer. Ordinary waste-to-energy plants do better than that, but don't burn as clean as a plasma arc.

The other problem is what comes out. Organic compounds are literally blasted apart into atoms at those temperatures, so it deals with biowaste just fine. CO2 comes out, of course. NOx, maybe. Everything heavier (metals, etc.) is supposed to come out as a "molten slag" suitable for cement aggregate. Not sure what the cement industry thinks of this. They're usually quite picky about what's allowed in cement aggregate. Some contaminants interfere with the chemistry of concrete curing and make bad concrete. It might be good for filling in swamps and such.

Bugger.. Didn't get that link bracketed correctly.

-jcr

After a summer of exhibition to the public, the team will deconstruct the house for transport down to Washington and will begin its final construction Sept. 29, entering the final phase of a two-year long journey.

he testing and characterization process is ongoing and the initial results were released on September 14, 2004. Contractor will be performing the cleaning and deconstruction of the building. ...
  In early 2004, an accord between Deutsche Bank and its insurers was reached to bring down the Deutsche Bank building. The deconstruction will remove the shrouded Deutsche Bank building that had been a constant grim reminder of the events of September 11, 2001.

Under the terms of the accord, LMDC was able to purchase the land and will pay for the deconstruction of the building.

Officials at PNC Financial Services, for example, plan to recycle more than 70 percent of the downtown Pittsburgh building they recently began deconstructing, a trend being seen at more demolition sites nationwide.

Fort Lauderdale Airport Interchange - This interchange project involved many challenges including context sensitive aesthetics, uninterrupted access over railroad tracks to the international airport, complex bridge arrangement, tight radii of curvature, and deconstruction of existing segmental bridges. Balanced cantilever precast concrete segmental bridges were selected because of their pleasing aesthetics and functionality suitable for the urban setting.

large amounts of concrete also recycle well into the sand and gravel used to make new concrete. Concrete recycling is generally only done on the scale of contruction/demolitions. How can you tell that recycling these materials saves energy? Recycling centers will PAY to take them.

Uhm, I haven't heard about this. Years ago for a few years I worked for a concrete/masonery contractor and what was said then was that using recycled concrete could be hazardous. Things may of changed since though.

I think it's generally just the sand and gravel that's reused, and new cement has to be added. And it may be limited in its uses. Hmm... come to think of it contractors usually have to pay to drop off their old concrete. Just that the fence company I worked for had a deal with the local company cause we put up their fence for a good deal. But it's probably cheaper than having the large bulk taken to a landfill.

After a little research it appears that the aggregate is mainly used for lining roads and the like before the final surface (concrete or asphalt) is poured. There is apparantly research that is making recycled aggregate useful in making up some of the bulk in general concrete usage, but a good portion of virgin material must be used as well. Materials testing prior to construction is strongly recommended before actual application as there are some changes in characteristics. Some pretty good information here and a thorough writeup can be found here. It also appears that one of the greatest benefits is in reconstruction, where old concrete can be processed on site for new uses eliminating the need to truck the debris out and then ship new materials in, leading to significant cost savings and greatly reduced effects on traffic patterns.

There is also the issue of wind. I'm sure concrete structures don't blow away as easily, and many disaster areas are going to have lots of wind and water. Plus, concrete doesn't need to dry to set. Apparently it sets up quite nicely underwater.

My father has been building unique houses for about thirty years. One was an earth-covered house ("underground" is a bit misleading, but that's what I would normally call it) and he's been looking into a very modular building material called 3-D Panel which is basically styrofoam between wire meshes. After you assemble the building, using rebar or something to connect wire meshes together, you spray it with shotcrete, and you're done. I mean, if we're allowed to have a spraying apparatus, why not? The specs for this panel system are impressive. They say the insulating value is R-18 to R-33--better than the new homes they throw up these days in my neighborhood.