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3-D printing 'greener' buildings using local soil:
The construction industry is currently facing two major challenges: the demand for sustainable infrastructure and the need to repair deteriorating buildings, bridges and roads. While concrete is the material of choice for many construction projects, it has a large carbon footprint, resulting in high waste and energy expenditure. Today, researchers report progress toward a sustainable building material made from local soil, using a 3-D printer to create a load-bearing structure.
[...] The researchers began by collecting soil samples from a colleague's backyard and tailoring the material with a new environmentally friendly additive so that it would bind together and be easily extruded through the 3-D printer. Because soils vary greatly by location, their aim was to have a chemistry "toolkit" that could transform any type of soil into printable building material. From there Bajpayee built small-scale test structures, cubes measuring two inches on each side, to see how the material performed when extruded into stacked layers.
The next step was to ensure that the mixture is load bearing, meaning that it will stand up to the weight of the layers but also other materials used in construction such as rebar and insulation. To help with this, the researchers strengthened the clay mixture by "zippering" the microscopic layers on its surface to prevent it from absorbing water and expanding, which would compromise the printed structure. With this method, the researchers showed that the material could hold twice as much weight as the unmodified clay mixture.
Journal Reference:
Aayushi Bajpayee, Mehdi Farahbakhsh, Umme Zakira, et al. In situ Resource Utilization and Reconfiguration of Soils Into Construction Materials for the Additive Manufacturing of Buildings, frontiers in materials (2020) 7:52. DOI: 10.3389/fmats.2020.00052
The approach is thought to both lower the environmental footprint of construction on Earth and model how construction can be effected on the Moon or Mars.
(Score: 2) by c0lo on Saturday August 22 2020, @12:56AM
Heck, no. The reason you need to use subsoil and not the fertile soil on top is because the later becomes friable when it dries - the soil particles don't stick well together.
Otherwise, cobb [wikipedia.org] has quite a lot of organic matter in the form of the straws - it helps keeping the clay together and preventing cracks (the straws, husks or any natural fiber that was added wicks the moisture inside the brick and ensure a more even drying).
Sand and stone, no.
Clay expands/contracts quite a lot with the variation of water content. Even very homogeneous pottery clay will crack when it dries if it's thick - like a mud brick.
Or if you stick one to the other pieces with different water content [handbuildersmonthly.com]
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford