March 5, 2007

Environmental friendly cement

Think about oranges.

You’re given some to package in the most compact way. Since round things are awkward to fit together, you’ll likely toss your oranges into a basket or box. Or, you could achieve a higher packing density by building them into a pyramid shape the way your local greengrocer sometimes displays them. And that is precisely the way concrete nanoparticles are organized: into thousands — millions — of tiny pyramids. Now researchers at the Massachusetts Institute of Technology have discovered that the source of concrete’s strength and durability lies in that pyramidal organization.

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Korky Koroluk

You’ve read about nanotechnology. I’ve written about it several times. It’s the application of science and engineering at the atomic scale. Indeed, it takes its name from the nanometre, a billionth of a metre. It’s about the atom-by-atom design and fabrication of microscopic structures which have new properties that make them powerful tools in medicine, biotechnology, energy and environmental industries and, yes, in construction.

Franz-Joseph Ulm leads the team of MIT researchers working on nanotechnology in cement and concrete, and when the team’s findings were published last month, he said that if everything depends on the way the nanoparticles are organized, and not on the cement itself, 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.

Ulm believes 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. He and his team have already begun that phase of their work, which, Ulm says, might take another five years.

The end result could mean an important reduction in carbon dioxide emissions during manufacture. See where this is going? Now that almost everyone has agreed, albeit grudgingly, that the actions of the human race are indeed causing global climate change, it would be nice if our “leaders” could call a halt to the ceaseless finger-pointing and partisan bellowing, forget about scoring political points and work on solutions instead.

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 for environmentalists: the amount of carbon dioxide released into the atmosphere during the manufacture of the cement and steel we use. That brings us back to Ulm and his team.

Using a wide range of cement pastes from around the world, they poked and prodded hardened samples with a nano-sized needle to assess the strength of each. They were surprised to find that the behaviour 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 tonnes of it each year — accounts for between five and 10 per cent of total carbon dioxide emissions. If, Ulm says, 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. The Lafarge Group provided part of the funding for the MIT research, and is to be commended for that. Research is an easy target for governments looking for ways to reduce expenditures. But unless the research is done, there won’t be a coherent response to the global warming problem. The Lafarge Group, like an increasing number of big businesses, has joined the battle, and for that I suggest we a lift a glass to them.

Korky Koroluk is an Ottawa-based freelance writer. Send comments to editor@dailycommercialnews.com

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