Researchers have developed a way to take soil from the ground and turn it into ink for a 3D printer, which can then be used to build homes and large structures.
By extracting clay from soil and mixing it with sodium silicate, researchers from Texas and San Fransisco were able to produce a material that could flow easily through the 3D printer, but harden quickly to form a strong, load-bearing structure.
The composition of a soil sample can vary greatly, containing any mixture of clay, rock and organic material. So, the researchers aimed to develop a tool that would turn any type of soil into a useable ‘ink’ for 3D printing.
They say that after a quick analysis of the soil, their toolkit could figure out how much sodium silicate needed to be added to the sample to turn it into a printable building material.
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The ability to 3D-print buildings has been available for a few years, with large robots using concrete to create frameworks for houses. However, many are concerned with the environmental impact of relying on concrete – it’s estimated that 7 per cent of global carbon dioxide emissions come from the cement industry, and it’s not currently possible to recycle the building material.
“The environmental impact of the construction industry is an issue of growing concern,” said Sarbajit Banerjee, principal investigator on the the clay-based 3D printing project.
A shape 3D printed using soil © Aayushi Bajpayee
Banerjee added: “Some researchers have turned to additive manufacturing, or building structures layer by layer, which is often done with a 3D printer. That advance has begun to transform this sector in terms of reducing waste, but the materials used in the process need to be sustainable as well.”
The team behind the project say that using a local soil source can cut transport emissions while helping the surrounding community.
Also of appeal is the opportunity for those in extreme or hostile environments to robotically print large-scale structures, write the researchers in their paper, such as building clinics in times of war or in disease-ridden jungles, or even in extra-terrestrial planetary environments.
Reader Q&A: Why aren’t large Lego bricks used to build full-size buildings?
Asked by: Edward Seymour, Hove
The plastic used in Lego – a type of polymer called ‘acrylonitrile butadiene styrene’ (ABS) – is surprisingly strong. In fact, it’s able to withstand compression better than concrete. Researchers at the Open University in 2012 found that an ordinary-sized Lego brick can support the weight of 375,000 other bricks before it fails. Theoretically, that would allow you to build a tower almost 3.5km high! But Lego is far too expensive to be used as a large-scale building material.
There are, however, Lego-style construction techniques that use other materials. ‘Insulated concrete formwork’ (ICF) uses hollow polystyrene blocks that are assembled into walls and then pumped full of concrete. The polystyrene acts as a mould and provides insulation. And in developing countries, interlocking blocks of compressed earth mixed with a small amount of cement are used as a cheap alternative to bricks and mortar.