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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."
Even if it is negligible, "going green" is the trendy thing to do nowadays, so as long as it seems like they're making an effort, that's far more important than if it actually helps.
Game! - Where the stick is mightier than the sword!
You're right in that we want strong and durable concrete. As another poster pointed out we are constantly changing the concrete mix proportions and admixtures. Admixes themselves are relatively new (~50 years) in the grand scheme of making concrete. It gets introduced slowly...and the universities then test it beyond belief for different properties. Maybe you'd like to be a grad student in civil engineering and make hundreds, or perhaps thousands of ever so slightly different mixes to determine the properties of your variable. I'm all for making concrete more "green" and I figure the universities and companies will test it before they use it in important projects.