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New "Nano" Cement Paste02-22-07 | News

New "Nano" Cement Paste

The strength of the cement paste, and thus the strength of the concrete, does not result from a specific mineral, but in the way the nanoparticles are packed.

For several years now, the construction industry has become increasingly aware of its environmental responsibilities and has overcome many problems. But there is still one fact that makes the industry an easy target: the amount of carbon dioxide released into the atmosphere during the manufacture of cement and steel.

Using a wide range of cement pastes from around the world, researchers at MIT believe it is possible to find ??" or nanoengineer ??" a different mineral to use in cement paste, rather than continuing to use limestone and clay calcined in a kiln. Everything depends on the way the nanoparticles are organized, and not on the cement itself, so it might be possible to replace the cement with something else and still preserve concrete's other characteristics ??" like strength, durability, ready availability and low cost. They poked and prodded hardened samples with a nano-sized needle to assess the strength of each. They were surprised to find that the behavior of the calcium-silicate-hydrate molecules in all the pastes had the same unique "signature." That told them the strength of the cement paste, and thus the strength of the concrete, does not result from a specific mineral, but in the way the nanoparticles are packed.

The worldwide production of cement ??" 2.35 billion tons of it each year ??" accounts for between five and 10 per cent of total carbon dioxide emissions. If those emissions can be reduced by as little as 10 per cent, the world would be one-fifth of the way toward meeting the goal of the Kyoto Protocol.