(CN) — Scientists have devised a way of transmuting ordinary soil into a next generation construction material in a process which would bring pride to the alchemists of yore.
By mixing soil with a gelling agent and feeding the slurry through a 3D printer, researchers have been able to construct watertight building blocks that can be used to assemble entire structures cheaper and more environmentally friendly than with traditional concrete.
The novel process was presented Thursday by Aayushi Bajpayee, a graduate student in the department of chemistry at Texas A&M University, at a meeting of the American Chemical Society.
In situ resource utilization, as it’s known, remains one of the holy grails of exploration. Using local resources to build shelter will be critical in any mission to colonize another planet such as Mars and could become equally important to further exploring remote areas of our own planet such as Antarctica.
It would also greatly improve our ability to build homes and other structures in developing regions where concrete is prohibitively expensive and could even help drive down housing costs in places like California and New York.
“We have demonstrated that we can 3D-print locally sourced soil into complex geometries, illustrating a powerful concept for in situ resource utilization wherein native soils can be harvested to build structures,” said Dr. Sarbajit Banerjee, the Davidson Chair in science at Texas A&M University, in an email interview.
“Such an approach would go a long way towards mitigating the catastrophic environmental impact of concrete while enabling construction in extreme environments (sub-Arctic, moon, Mars) where transportation of building materials is difficult. “
The building sector is responsible for over 40% of global carbon emissions. The concrete industry alone accounts for nearly 7% of those emissions, according to a report from the World Business Council for Sustainable Development.
Concrete production consumes four gigajoules of electricity annually and releases around one ton of carbon dioxide per ton of concrete produced. Even with modernization efforts, new construction methods that remain dependent on concrete production could prove unsustainable.
"The environmental impact of the construction industry is an issue of growing concern," said Banerjee. "Some researchers have turned to additive manufacturing, or building structures layer by layer, which is often done with a 3-D 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."
Indigenous cultures have been building shelters solely using materials found on-site for millennia. The Aztecs built their vast cities from adobe, a method which numerous Native American cultures went on to replicate. The researchers hope to scale up these traditional building materials using additive manufacturing and employ automation to allow similar structures to be built anywhere en masse.
Building materials would no longer need to be produced hundreds of miles away and transported by rail and boat. They could instead be harvested from the very grounds being built on, and once a building has reached the end of its life, it can be demolished and rebuilt using those same materials without detriment to the local environment.
Because different regions have a diversity of soil types, some sandy, some heavy with clay, the researchers say they are adapting their process so it can be used anywhere.
“We are seeking to expand the palette of available soils — from muskeg soil in the sub-Arctic (if you’ve ever seen “Ice Road Truckers,” you’ll know the challenge of building all-weather roads) to regolith on Mars,” said Banerjee. “We are considering ways to enhance the load-bearing capability of the soil composite which is integral for building structural elements with a view towards enhancing the strength and load-bearing capacity of the structures. One approach will be through the incorporation of rebar within the printed structures.”
If you’ve ever seen a half-demolished building, you’ve seen rebar. They’re the long tubular metal bars running the length of concrete slabs that provide reinforcement. Rebar makes buildings taller than just a few stories possible, and is vital for any load-bearing structure. Banerjee and his team are still working to incorporate 3D-printable rebar into their process, which would be a monumental advance toward making this technology commonplace.
“As far as complexity goes, 3-D printing has greatly revolutionized the building forms that we can create,” added Banerjee. “Moving forward, we are aiming to print building elements through increased strength and via weaving in reinforcing elements. In other words, we are able to create bespoke building elements with specific function but have not thus far created a means to replace reinforced concrete for load-bearing structural elements.”
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