3D printing 'greener' buildings using local soil

Date:
August 20, 2020
Source:
American Chemical Society
Summary:
Scientists report progress toward a sustainable building material
made from local soil, using a 3D printer.



FULL STORY ==========================================================================
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 3D
printer to create a load- bearing structure.


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The researchers will present their results today at the American Chemical Society (ACS) Fall 2020 Virtual Meeting & Expo. ACS is holding the
meeting through Thursday. It features more than 6,000 presentations on
a wide range of science topics.

"The environmental impact of the construction industry is an issue of
growing concern," says Sarbajit Banerjee, Ph.D., the project's principal investigator.

"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."
For example, construction projects using extruded layers of concrete
have highlighted the potential of additive manufacturing for building structures quickly and cheaply. However, concrete manufacturing is
responsible for approximately 7% of carbon dioxide emissions according
to the International Energy Agency, and cannot be recycled.

"Historically, humans used to build with locally sourced materials,
such as adobe, but the move to concrete has raised many environmental
issues," says Aayushi Bajpayee, a graduate student in Banerjee's lab at
Texas A&M University.

She is presenting the work at the meeting. "Our thought was to turn the
clock back and find a way to adapt materials from our own backyards as a potential replacement for concrete." An advantage to using local soil in construction is that the materials would not need to be manufactured and transported to the building site, reducing both costs and environmental
damage. Banerjee and Bajpayee also say that additive manufacturing with
soil could one day be used beyond Earth, to create settlements on the
moon or even Mars.

Soil is typically classified by the layers of materials it comprises,
beginning with the top organic layer where plants grow and ending at
the hard bedrock of the earth's crust. Beneath the initial organic
layer is clay, which gives soil its plastic, moldable character that
the researchers capitalized on in their project.

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 3D 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.

Next, the team plans to improve the soil's load-bearing capabilities
in order to scale up their test structures and get as close to a
replacement for concrete as possible. In addition, they are gathering
data to see whether these 3D printed structures are as environmentally
friendly as they envision, especially in terms of carbon footprint and recycling potential. Once they have a better picture of the chemistry, functionality and feasibility of building with local soils, they plan
to further explore how this technology can be used beyond our own planet.

The researchers acknowledge support and funding from the X-Grants Program
at Texas A&M University.


========================================================================== Story Source: Materials provided by American_Chemical_Society. Note:
Content may be edited for style and length.


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Link to news story: https://www.sciencedaily.com/releases/2020/08/200820102452.htm

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