Bamboo to replace steel and fungi to replace concrete: a research group at the Karlsruhe Institute of Technology (KIT) is working on ways of using renewable raw materials in the construction industry. Biological building materials such as bamboo and fungal mycelium could one day replace conventional materials such as steel and concrete.
Population growth and urbanisation are creating huge worldwide demand for building materials. However, steel and concrete production is expensive, energy-intensive and uses finite natural resources such as sand and iron ore. A diverse team of architects, construction and bioengineers from the Karlsruhe Institute of Technology is working on finding sustainable alternatives.
Architect Prof. Dirk E. Hebel has headed up the "Sustainable Construction" unit at the Karlsruhe Institute of Technology (KIT) since April 2017. Prior to that, Hebel and his colleagues Karsten Schlesier and Felix Heisel from the KIT were carrying out research at the ETH Zurich and the Future Cities Laboratory in Singapore. However, the foundation stone of their collaboration was laid in Addis Ababa, as Felix Heisel reports: "When we were in Ethiopia we experienced first-hand what resource consistency in architecture actually means. And this has motivated us to work towards improving the use of local resources." Bamboo is a promising candidate. The giant grass is available in most tropical and subtropical regions, is extremely fast-growing, and its woody fibres and trunks are characterised by high tensile strength. This puts it on a par with steel, which, along with concrete, is today's key building material. However, steel is not only energy-intensive to manufacture, but also an expensive commodity for many poorer countries. In Africa, for example, just two of the fifty-four African countries have a significant steel production industry.
In the meantime, the researchers from Karlsruhe have successfully developed a bamboo composite which can be used to reinforce concrete parts.1 The bamboo is heat-treated, split into individual strips, resins are added and the whole pressed into a solid composite material. These bamboo composite poles can be used to reinforce conventional concrete from the inside. The bamboo composite reinforcements withstood a laboratory test and displayed a tensile strength similar to that of structural steel. Bamboo thus represents a real alternative to steel. Now, the move from laboratory to practical use has to be made, and this will involve integrating the bamboo-reinforced concrete into a multi-storey prototype that will have to withstand a long-term test.
In their search for a renewable support material for buildings that can be used in the industry, the researchers are testing fungal mycelium, a tissue made of thread-like fungal cells. A 3-metre-tall tree construction called “MycoTree” whose trunk and branches are made of dozens of fungal building blocks was developed for the "Biennale of Architecture and Urbanism" in Seoul, South Korea. The MycoTree has a very sophisticated design that exploits the strengths of both materials: first, the fungal building blocks are able to withstand pressure and stabilise each other, and second, the weight and tensile strength of the bamboo lattice holds together the branches of the MycoTree.
The fungal building blocks were produced by an Indonesian company called Mycotech with sacks that were filled with sawdust and fungal spores. After a few days, the fungal hyphae penetrate the substrate, giving it a spongy consistency that is freely mouldable. This mass filled into prefabricated moulds of desired size and shape, and left to dry after another growth phase. Dessication causes the fungus to die. The mass becomes solid and the fungal mycelium stabilises the building blocks.
"The fungal building blocks look like pressboards, consisting of sawdust and fungal mycelium. The only difference from normal pressboards is that fungal mycelium is used as an adhesive," says Heisel. "As far as we know, MycoTree is the first mycelium structure that supports itself as well as a load. "MycoTree benefited from the know-how of Philippe Block from the Block Research Group (BRG) at ETH Zurich. Block has developed sophisticated graphical methods that enable statics to be calculated three-dimensionally. This makes it possible to build a stable construction from a rather brittle material like mycelium building blocks. "We wanted to show what's possible when the design is right," says Heisel.
In the next few years, Felix Heisel and his colleagues will continue working with the mycelium building blocks: "From the Petri dish to architectural application," as Heisel says. "We have a relatively light material that can withstand a certain pressure and is freely mouldable, at least up to a certain volume." Another advantage is that the know-how for large-scale fungi production is already available from the food industry. However, only the fungal fruit bodies are of interest to the food industry and mycelium is just a waste product, whereas in the construction industry, mycelium can be put to good use.
One day, people may well be living in houses "grown" from bamboo and fungi. The additional advantage is that the materials can easily be separated and reused. This would be in keeping with the needs of circular economies and help solve the basic question that the Karlsruhe researchers are focusing on: "How do houses need to be built in the future so that we can reuse the materials and return them to their respective cycles?"
1 Javadian, A et al. (2016) Bond-behavior study of newly developed bamboo-composite reinforcement in concrete, Construction and Building Materials Vol122, p110-117, https://doi.org/10.1016/j.conbuildmat.2016.06.084
Team:- Sustainable Construction, Karlsruhe Institute of Technology, KIT Karlsruhe: Karsten Schlesier, Felix Heisel, Dirk Hebel- Block Research Group, ETH Zürich: Juney Lee, Matthias Rippmann, Tomás Méndez Echenagucia, Andrew Liew, Noelle Paulson, Tom Van Mele, Philippe Block- Alternative Construction Materials, Future Cities Laboratory, Singapore-ETH Centre: Nazanin Saeidi, Alireza Javadian, Adi Reza Nugroho, Robbi Zidna Ilman, Erlambang Adjidarma, Ronaldiaz Hartantyo, Hokie Christian, Orion Tan, Sheng Yu, Kelly Cooper
Production partners:Mycotech, PT Miko Bahtera Nusantara, Indonesia
Sponsors:- ETH Global- ETH Zürich, Department of Architecture- Karlsruhe Institute of Technology (KIT)- Future Cities Laboratory (FCL), Singapore-ETH Centre