Science Interviews


Mon, 28th Apr 2014

Building with bamboo

Michael Ramage, University of Cambridge

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Itís not just the way we build houses that might change in the future, Bamboo trees in Kyoto, Japan.but the materials we use as well. In order to make housing across the world more environmentally friendly Michael Ramage from the University of Cambridge is trying to develop the use of bamboo to replace traditional building materials.

Chris - So, why bamboo?

Michael - Weíre very interested in bamboo because it is very fast growing. Itís widely distributed around the world, particularly in areas where populations are growing and populations are moving to cities, but also, where trees don't grow. And itís extremely strong.

Chris - What about the environmental equation, whereby, in the same way that people in America were growing a lot of crops to make biofuels, but actually, they were taking land that could be grown for food out of production. There was an environmental cost there focused at, to buy the food in from elsewhere or turn other land into food producing land to make up for the fact that weíre growing fuel crops. Can we make the same sort of arguments for bamboo?

Michael - Well, if anyone has grown bamboo in a garden, they know that it grows rapidly and it tends to grow anywhere. The countries that grow a lot of bamboo like China or Columbia, we find it grows very well on hillsides, extremely steep hillsides where you can't plant crops.

Chris - So, why are people not doing this already?

Michael - There's a long history of using bamboo in its natural form for houses in vernacular cultures. So basically, people building without architects and itís only in the last 20 or 30 years that people have processed bamboo into the type of materials we use in conventional construction.

Chris - Well, tell us more. How do you process it because when I've seen bamboo use in China, you see scaffolding or buildings to extremely great heights made of bamboo? You think, ďGosh! That doesnít look very strongĒ but actually, it clearly is. How is it used differently then?

Michael - So, the processing of the bamboo is, it grows around. Itís a stalk. Itís a blade of grass that happens to be 17 centimetres in diameter. It gets split up into slivers which are then cut down into rectangles and then the rectangles are glued together to make big sheets of what we might refer to as plywood. Itís a different material, but itís like a sheet of plywood.

Chris - What's its mechanical characteristics that mean itís better or at least equivalent to what we could otherwise use?

Michael - So, itís about 5 times stronger than timber in either tension or compression, so when you pull on it or push on it. Compared to its strength, itís extremely flexible. So, its flexibility is about the same as timber.

Chris - Gosh! These are good statistics. I can't understand why weíre not all doing this already.

Michael - Well, the material is Ė although bamboo grows all over the world and there's a lot of the material and it grows extremely fast, there isnít a lot of bamboo that's processed. Itís mostly processed for flooring as you probably have seen in buildings around Cambridge. Itís quite popular.

Chris - It doesnít sound like itís rocket science to make those processed bamboo materials. You chop it up and glue it together which is what weíre already doing for chipboard and things anyway, arenít we?

Michael - Yes, indeed, but one of the problems is that there is at the moment, very little market because engineers and architects don't necessarily have codes they can refer to for designing bamboo buildings. Without bamboo buildings being designed, companies are reluctant to make a lot of material that doesnít have a market.

Chris - So, how does it stack up in terms of where it could be deployed? What sorts of building applications could it have and will it save people money because all of this is going to come down to the bottom line? Is this going to end up costing them a load more? If so, they're not going to do it because they're going to pass it on to the customer and become uneconomically viable?

Michael - Well, we think in the research that weíre doing at Cambridge University is, looking at how we can use this structural bamboo in large scale buildings. So, 6, 7, 8, 10-story buildings. At the moment, a building like that made of structural bamboo would be much more expensive than an equivalent in steel or concrete. But we think in the long term that it will become competitive especially if we change the way we price carbon.

Chris - Will this be mainly the cladding that the bamboo is used for or would you see it being used for all of the building so you could replace the steel frame or the timber frame, or whatever sort of building you're doing with some kind of bamboo composite?

Michael - The work weíre doing at the moment is looking at ways to replace the structural frame with bamboo. There is already quite a bit of material that can be used for cladding, particularly the interior surfaces.

Chris - What about lifeing of the material? We know if you build a house from an oak frame, itíll be there in 500 years if you look after it. Do we know what the lifeing of these bamboo materials is?

Michael - The same is true for bamboo. If you keep it dry and keep it out of the sun and in other words, if the architects and the engineers detail the buildings correctly and they stay dry then it will last for a very long time, just like wood will.

Chris - Why is bamboo structurally sort of ultrastructural level so good in this regard? Why does it have these characteristics?

Michael - Well, we have partners at MIT who are working on that at the moment, but in simple terms, itís made up of very, very strong fibres that go in one direction up the stalk of bamboo. Those fibres themselves are extremely strong.

Chris - And so, if you cross them so they're at 90 degrees to each other when you stick the chips together then you're going to get this very, very powerful composite in two different directions just like plywood.

Michael - Yes and there are many ways you can put them together, either crossed or all oriented in the same way to get different sorts of properties, depending what you're trying to build.

Chris - Well, I might have to build my next house out of bamboo so the pig that built his house from straw was sort of halfway there. Heís still using a sort of grass, wasnít he? Michael Ramage from the University of Cambridge, thank you very much.


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