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Green Cement Absorbs Carbon
Peace Corps Online writes "Concrete accounts for more than 5 percent of human-caused carbon dioxide emissions annually, mostly because cement, the active ingredient in concrete, is made by baking limestone and clay powders under intense heat that is generally produced by the burning of fossil fuels. Now Scientific American reports that British start-up company Novacem has developed a 'carbon-negative' cement that absorbs more carbon dioxide than it emits over its life cycle. The trick is to make cement from magnesium silicates rather than calcium carbonate, or limestone, since this material does not emit CO2 in manufacture and absorbs the greenhouse gas as it ages. 'The building and construction industry knows it has got to do radical things to reduce its carbon footprint and cement companies understand there is not a lot they can do without a technology breakthrough,' says Novacem Chairman Stuart Evans. Novacem estimates that for every ton of Portland cement replaced by its product, around three-quarters of a ton of CO2 is saved, turning the cement industry from a big emitter to a big absorber of carbon. Major cement makers have been working hard to reduce CO2 emissions by investing in modern kilns and using as little carbon-heavy fuel as possible, but reductions to date have been limited. Novacem has raised $1.7M to start a pilot plant that should be up and running in northern England in 2011."
the composition of asbestos?
This sounds like a concrete nightmare:
If a material absorbs so much CO2 over it's lifespan, it significantly alters the chemical composition and therefore strength.
I doubt any builder will use this material unless it's been proven that the new material is sufficiently stable.
Example: as a geology student, I ran into an area in central spain with lots of Gypsum sediments (Ca|MG.SO4). Putting limestone and concrete buildings on this sediment wasn't done until the 20th century, but all the buildings built in that area are long gone, even though in nearby towns they still stand tall. Reason? The Gypsym in the soil chemically eats the mortar and limestone (CaCO3) out of the structure on top of it, making it crumble within a few decades. The Gypsum areas are largely a wasteland where only very few buildings remain.
Now, Mg.Ca-CO3 (dolomite limestone) is largely as stable or more stable than pure limestone, and certainly harder, but any new formula for the glue in concrete will have to pass the test of time before it will be widely adopted, especially in e.g. bridges and skyscrapers...
Perhaps we can start with the interstates, nobody would notice if they started to crumble early ;)
What is the life span?
How much if a cost increase would it take to reduce our carbon dioxide emissions by using this product?
Does it have the same strength? Is it completely interchangeable with today's concrete?
Is it possible to retrofit current concrete plants? Do we have to build all new concrete plants?
Fly ash, which is the ash waste from burning coal is also being used in concrete to lessen the amount of C02 concrete creates as well as improve strength. My question is since this fly ash has a high amount of toxins(heavy metals) in it, would the toxins be locked in the concrete or would they seep out if exposed to water or other stresses over time.
I am curious to know this because apparently fly ash can make concrete easier to work with in insulated concrete form construction and because other types of materials that compete with concrete seem to be using it. Gigacrete.com ( supposedly 10,000 psi strength) though not for structural use is an example. I can't tell if they are using weasel words though because they claim there binder is nontoxic, I can't tell if they are purposely talking about the binder being non toxic and not the fly ash.
I hope someday to build a house out of ICF's (insulated concrete forms), I guess I must have taken to heart that story of the three little pigs when I was young.
Sure, hundreds of years, if not more. Do you mean that this is the first time someone has changed the recipe?
The summary doesn't explain things very well. Just to set things straight, most of the CO2 emissions from portland cement production is not from the fuel burned in the kilns but from the gas released by the limestone itself during the calcination process. The only real incentive for the use of energy efficient kilns is to reduce fuel costs and not to reduce emissions. The upside is that cement will reabsorb much of the released CO2 as it cures over the course of time.
I am becoming gerund, destroyer of verbs.
"...mostly because cement, the active ingredient in concrete, is made by baking limestone and clay powders under intense heat that is generally produced by the burning of fossil fuels."
This sentence got me to wondering. . . one of the big problems of thermal electric power plants (coal, natural gas, nuclear), is that we throw away 50-60% of the heat as waste heat into the environment (nearby body of water or the air). Could the waste heat from a coal or nuclear power plant be used to 'bake' the cement? In the case of coal, sure, you're still burning fossil fuels, but those were being burned *anyhow* to generate electricity, so why not put the waste heat to use? You are, *at least*, not burning any *additional* fossil fuels just for the cement, right? In the case of Nuclear, you are using a very low-carbon heat source, and again, doing something useful with the waste heat?
It's not just you, I've heard it said that the next bubble of the 21st century, after the tech bubble and the housing bubble, will be the carbon credit bubble. There is a new government-created "commodity" in carbon credits, which are government-mandated to decrease in number over time, and are therefore government-mandated to increase in value over time. Sounds like something that's right up Goldman Sachs' alley. I might even guess that the collapse of such a bubble would occur when rampant speculation on carbon credits drives the prices of said credits up high enough that corporations who are able to do so start shifting their industry to nations where the carbon credit regulations are unenforced or unenforceable, nations which would gain enormous financial benefit by being "carbon credit havens." The value of carbon credits could only be propped up for as long as investors felt secure that everyone was playing by the same rules, and we know how often that happens.
The house I live in is a mere 150 years old, but most of the street it is in was built between 1690 and 1695. In fact, our foundations go back to then. The composition and structure of Bath stone has been extensively studied, and I would imagine the results are just a small part of the data the technologists will take into account.
And your point was, again?
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
Please link to legitimately peer-reviewed scientific articles that back up these claims, because what you're saying contradicts all the evidence I've ever seen.