Steel-reinforced concrete is the most common building material in the world, and developing countries use close to 90 percent of the cement and 80 percent of the steel consumed by the global construction sector. However, very few developing countries have the ability or resources to produce their own steel or cement, forcing them into an exploitative import-relationship with the developed world. Out of 54 African nations, for instance, only two are producing steel. The other 52 countries all compete in the global marketplace for this ever-more-expensive, seemingly irreplaceable material.
But steel is not irreplaceable. There’s a material alternative that grows in the tropical zone of our planet, an area that coincides closely with the developing world: bamboo. Bamboo belongs to the botanical family of grasses and is extremely resistant to tensile stress and is therefore one of nature’s most versatile products. This has to do with the way the grass evolved, adapting to natural forces like wind. In contrast to wood, the bamboo culm or haulm, which are botanical terms for the stem of a grass, is thin and hollow. This allows it to move with the wind, unlike a tree, which tries to simply withstand any natural forces it is exposed to. This adaptation for flexible movement required nature to come up with a very light but tension-resistant fiber in the bamboo culm which is able to bend in extreme ways without breaking. In its ability to withstand tensile forces, bamboo is superior to timber and even to reinforcement steel.
Bamboo is also a highly renewable and eco-friendly material. It grows much faster than wood, is usually available in great quantities, and is easy to obtain. It is also known for its unrivalled capacity to capture carbon and could therefore play an important role in reducing carbon emissions worldwide – another advantage for developing nations in light of the trade in carbon emission certificates. Simply from an economic perspective, most developing nations should be interested in the material. It could strengthen local value chains, bring jobs and trade to those countries, and lower their dependency on international markets.
The great social, economic, and material benefits of bamboo and its widespread availability are not reflected in the demand for the material, however. Despite its strengths, bamboo has a number of weaknesses as a construction material. Water absorption, swelling and shrinking behavior, limited durability, and vulnerability to fungal attacks have limited most applications of bamboo so far. Today, bamboo is generally limited to traditional applications of the culm as a structural component in vernacular architecture; early attempts to use it as an untreated, non-composite reinforcement material in concrete were not successful. The technology to improve the material hasn’t been developed yet, probably because most countries with major bamboo resources are in the world’s developing regions and have little, if any, industrial capacity.
At ETH Singapore’s Future Cities Laboratory (FCL) , a team of young researchers is working to tap bamboo’s potential by exploring new types of composite bamboo material. The material’s tensile strength aroused our interest as architects and engineers and inspired us to investigate the possibility of extracting the fiber from the natural bamboo, transforming it into a manageable industrial product, and introducing it as a viable building material, an alternative to steel and timber. Bamboo composite material can be produced in any of the familiar shapes and forms in which steel and timber are produced. Like them, the material can be used to build wall structures for houses or any other buildings. More interestingly, it can be used for specific applications that best take advantage of the material’s tensile strength, such as reinforcement systems in concrete or beams for ceilings and roof structures.
REHAU Germany, Dr. Dragan Griebel
EMPA Dübendorf, Switzerland, Tanja Zimmermann