Large-scale additive manufacturing, or 3-D printing, has drawn attention for its potential to create affordable, quickly constructed structures—like in Austin, Texas, where the technology was recently used to build homes for people experiencing homelessness. But the materials for these projects are typically based on concrete, which has environmental costs: producing concrete generates large amounts of carbon dioxide, and it’s tough to dispose of. Researchers at Texas A&M University led by Sarbajit Banerjee want to replace concrete by developing a chemistry tool kit that can convert local soils into a 3-D printable material (Front. Mater. 2020, DOI: 10.3389/fmats.2020.00052). As a case study, the team developed a material based on a common local clay that it optimized for extrusion from a 3-D printer. The researchers made the material by creating a cross-linked siloxane framework that could bind clay particles together. The benefit of such a material, the team says, is that it could reduce the carbon footprint of transporting construction materials long distances.
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The following is the script for the video. We have edited the interviews within for length and clarity.
Kerri Jansen (voice-over): 3-D printing isn’t only used to make small parts. It can also be used to build large structures quickly and cheaply. In Austin, Texas, for example, people have used 3-D printing—also known as additive manufacturing—to make concrete shelters for people experiencing homelessness. But concrete has some environmental downsides. Some studies estimate that making concrete generates as much as 8% of human-produced global CO2 emissions, and the material is difficult to recycle when it’s no longer needed.
So at Texas A&M University, researchers are developing alternative materials to reduce the industry’s reliance on concrete. They propose adapting locally harvested soils for 3-D printing. To demonstrate the idea, they created this material, which is made with clay from a colleague’s backyard.
Aayushi Bajpayee: It’s from a professor’s backyard. So our approach was to take the most complex form that is available in nature, because if we prove that we can do the complex mixture, then doing noncomplex mixtures and store-bought mixtures are much easier.
Kerri: To make a 3-D printable material from clay, Aayushi mixed backyard samples with sodium silicate and an alkaline catalyst. The silicate precursors react to form a cross-linked siloxane framework that binds the clay particles together as the printed material cures. Aayushi tailored the formula so it would flow easily through a 3-D printer and cure quickly to support the next layer of material.
Then she used it to build a test structure.
Group leader Sarbajit Banerjee says the chemistry makes it possible to use a variety of local soils and avoids the need to transport materials long distances.
Sarbajit Banerjee: If you could do a quick analysis of the local soils, we’d like to have a fairly versatile chemistry tool kit that you could just adjust a little bit and then sort of get to printing.
Kerri: For now, Sarbajit says, the material is best suited for nonstructural elements like a building’s facade. But the team is working to optimize their chemistry tool kit to produce stronger materials that can flow through giant 3-D printers while keeping the technology’s carbon footprint in check.
Sarbajit Banerjee: If additive manufacturing takes off and it happens only with concrete, it would increase the carbon footprint of the construction industry. I think we’re poised on the brink of a huge paradigm change in construction, and chemistry is going to be a big part of that.