There is an urgent need for sustainable solutions for a rapidly growing population, especially as the global housing crisis deepens.
3D printed polymer-based concrete structures. Image: Advanced Composites and Hybrid Materials.
In recent years, additive manufacturing, or 3D printing, has emerged as a sustainable method to solve construction challenges.
Now, researchers at Oregon State University (OSU) in the US have developed a green, clay-based construction material that could make instant 3D-printed homes a plausible future reality.
The rapid construction capability is especially useful for quickly building shelters and structures following natural disasters.
3D printed polymer-based concrete structures. Image: Advanced Composites and Hybrid Materials.
Chemical reaction for instant strength
Cement is the key binder in concrete, but it poses significant environmental problems. It is responsible for roughly 8% of the planet’s carbon dioxide emissions.
The huge industrial kilns required to produce it heat materials to more than 1,400 degrees Celsius, consuming vast amounts of fossil fuel energy.
Furthermore, the slow curing process of concrete – which can take up to 28 days to reach full structural strength – severely limits the speed of construction projects.
The OSU team, led by assistant professor Devin Roach and doctoral student Nicolas Gonsalves, tackled this twofold challenge of pollution and time.
The development involves a clay-based ink – mixed with common materials – that uses the chemical process known as frontal polymerisation.
Interestingly, the material cures instantly as it is extruded from the printer due to an acrylamide-based binding agent. This rapid curing allows it to be printed even across unsupported openings, like the tops of door or window frames.
“The printed material has a buildable strength of three megapascals immediately after printing, enabling the construction of multilayer walls and free-standing overhangs like roofs,” said Roach, assistant professor of mechanical engineering in the OSU College of Engineering.
“It surpasses 17 megapascals, the strength required of residential structural concrete, in a mere three days, compared to as long as 28 days for traditional cement-based concrete,” added Roach.
This faster timeline beats the weeks or even months required for standard cement to reach the same stability.
Apart from its speed, the material has a much smaller environmental footprint. It is primarily composed of easily available soil, hemp fibres, sand, and biochar.
Biochar, a carbon-rich substance produced by heating organic waste such as wood chips under low-oxygen conditions, effectively sequesters carbon.
This bio-concrete replaces a large portion of the energy-intensive cement with materials that are essentially earth-based and less carbon-intensive to produce.
Notably, this material can make a difference in various ways, proving particularly valuable for quickly providing shelter in disaster-hit areas.
“Especially with the frequency of destructive natural disasters, we need to be able to get shelter and other structures built quickly – and we can do that with a material that’s readily available and is associated with comparatively little emissions,” said Roach.
The research has charted a clear path forward. While the immediate cost remains higher than standard concrete, the team is focused on bringing the price down.
Moreover, the next steps involve adhering to American Society for Testing and Materials (ASTM) standards to ensure safety and obtain regulatory approval.
Clay-based material could lead to a future where houses are printed not only fast, but also with significantly less damage to the planet.
The study was published in the journal Advanced Composites and Hybrid Materials.