As 3D construction printing continues to innovate, so does its means of production. Currently, liquid concrete (or cementitious ink) is the most common material used to print houses—but it’s hardly the most environmentally friendly option.
This begs the question: What else could we print houses out of, and what have we tried already?
3D construction printing (3DCP) experts came together to discuss that and more at the first ever 3D Printed Housing Conference. From university professors to 3D printing builders, experts focused on the future of housing, and pondered these possible material innovations.
ENVIRONMENTALLY FRIENDLY 3D CONSTRUCTION PRINTING MATERIALS
Jose Duarte, professor of architecture at Penn State University, believes in 3DCP’s ability to build optimized designs that suit the needs of families and communities. In his research on 3D construction printing, Duarte has found a few materials that could be an effective, sustainable alternative to liquid concrete.
Cork
Cork has a big advantage because it’s a natural material, according to Duarte.
“The exploitation of cork has very little ecological impact because it comes from the bark of trees,” he says. In seven years the bark will grow back—allowing for continued harvesting.
Incorporating cork granules in 3DCP makes for an interesting printing material. From Duarte’s research at Penn State, they’ve found that these structures perform very well in terms of fire protection and compressive strength. Additionally, cork has very good acoustic and thermal insulation properties. All of this means that structures built with cork granules can be lighter and better insulated than concrete mixed with alternative additives.
In fact, Duarte has already put cork to the test. The Penn State team has developed software to customize the design of building parts, and also software to control the machine.
“In that case we basically have two machines: One uses concrete with sand aggregates, and the other has concrete with cork aggregates,” he says.
Check out this short clip from Jose Duarte's presentation at the 3D Printed Housing Conference:
Expanded clay
In an effort to decrease the overall weight of a 3DCP structure while improving its insulative properties, they’ve also experimented with expanded clay granules.
Specifically, Duarte’s colleague Shadi Nazarian has been working on a printing solution that transitions from concrete to glass. Accomplishing this would allow for having windows with no frames or joints, resulting in no energy leaks, and increasing air/water tightness.
This concept was explored in NASA’s 3D-Printed Habitat Challenge of 2017, where Nazarian co-led an interdisciplinary Penn State team to earn second place and a $150,000 prize. NASA’s centennial challenge competition was established to develop the technology necessary to create shelters to support the human exploration of Mars. To have an impermeable glass-concrete printing solution would enable the design of seamless shelters, protecting individuals and the climate inside the habitat.
“For environments like the Moon or Mars, where you have to build a completely sealed structure, that’s a very important advantage,” says Duarte.
For now, Duarte says they’ve only been able to accomplish this with molding, but are trying to do it with 3D printing as well. According to him, that will still take a few more years to develop.
Hempcrete
“We [at Penn State] are looking into different types of concrete because we have specialists in that area. The use of hempcrete is great, but there are also many possibilities,” says Duarte.
Check out this short clip from Jose Duarte's presentation at the 3D Printed Housing Conference:
Hempcrete is a healthy, natural, and sometimes cheaper alternative to concrete. It comes from plants, is bound by the Earth, and can absorb carbon dioxide. Some companies like MIRRECO are even looking into developing carbon-absorbing products using hemp.
The key issue with using Hempcrete, according to Duarte, is actually being able to develop a mixture that can be printable. There’s a small window of time for the mixture to work—it needs to flow well and then harden as fast as possible to keep its shape.
Another possibility to think about is Aircrete. Aircrete?! Yes, it’s Portland cement with added air bubbles. This “green cement” offers increased insulation, a good compressive strength, and better thermal performance, according to Rise. Now let’s just figure out how to print with it.
Gel polymers
Gel-based printing aids have been studied as well, using hydrogel-forming polymers as printing aids for cement-based pastes. Duarte and the Penn State team behind the NASA competition used gel-based polymers in the initial stages of the project, but found it difficult to work with.
For now, it seems like this one still needs to be researched further.
Rice fibers
Italian start-up WASP printed Gaia, the first 3D printed “mud house” made from natural materials. Included in their printing mixture was soil, rice fibers, and lime, resulting in a structure with minimal environmental impact.
According to WASP, the structure does not need heating or an air conditioning system, as it maintains a mild and comfortable temperature inside both in winter and in summer.
WHEN COULD WE SEE HOUSES PRINTED WITH SUSTAINABLE MATERIALS?
Duarte sees 3DCP becoming an industry standard in the next 10-15 years, especially for residential construction.
“It will probably dominate the market in certain areas where having access to printable mixtures or materials needed to print are accessible,” he says.
Check out this short clip from Jose Duarte's presentation at the 3D Printed Housing Conference:
However, it takes time to adopt new technologies. Duarte believes 3DCP’s impact on the industry will take a few more years because of this. In the meantime, there is still an increased number of applications and research on the topic that is progressively increasing.
The best bet for the growing use of sustainable additives in cementitious ink? More projects—lots of them—and at larger scales. Companies like Alquist 3D that have announced its 200 printed homes project, or Mighty Buildings with its first net zero energy community of 3D printed homes, are already making headlines for planning to print homes at-scale.
To get access to the full clips from the 3D Printed Housing Conference, click here to watch them for free.