For International Mud Day, we show you some institutions that are getting their hands dirty to build sustainably with mud.

The most common construction materials are bricks and concrete. However, both these material come with an energy intensive production process, typically over 1,000 degrees Celsius. Cement production accounts for 5-10 per cent of global CO2 emissions.

To keep global warming below an average of 2 degrees Celsius, it’s important to switch to more sustainable building materials. One option is a material that has been used for centuries: mud.

Boring bricks
The Boring Company, founded by Elon Musk, has as goal to one day construct a large urban network of tunnels. A by-product of tunnelling is of course dirt. Rather than disposing of the leftover dirt, Musk announced in March that it will be turned into interlocking, Lego-like bricks that can be used to build houses and other buildings. According to Musk the bricks will be rated for “California seismic loads”, so they will be strong, but also lightweight.

“[B]uildings have been constructed from Earth for thousands of years including, according to recent evidence, the Pyramids,” The Boring Company’s website states. They continue, “These bricks can potentially be used as a portion of the tunnel lining itself, which is typically built from concrete. […] [E]arth bricks would reduce both environmental impact and tunnelling costs.” In addition to the tunnel, the bricks will also be used for affordable housing, according to Musk. The exact costs, or when they will be available, are unclear.

Super mud
One drawback of mud bricks is that they eventually erode and collapse, because the bricks lack any kind of stabilising agent. Researchers from the University of Bath and the Indian Institute of Science are working with a type of ‘super mud’, called geopolymer-stabilised soil materials (GSSM).

A geopolymer is a hard and durable substance similar to cement, made out of chains of aluminium, silicon, alkali metal and oxygen atoms. Geopolymer-stabilised soil materials are made by mixing soil with an alkaline activating solution, containing chemicals similar to household cleaning products. The resulting mix can be shaped in moulds and is heated at 80-100 degrees Celsius, considerably lower than clay bricks.

According to the researchers, “GSSM would not be used in high-strength applications like high-rise buildings, but it has the potential to be a very good replacement for concrete in low and mid-rise housing, which is how much of the new housing in developing countries is being built.”

For a 3D printed building made from mud, click here.

Photos: Lirinya / Hannah Pethen / Whiteghost.ink