Mark Megahan
Dr. Rajeev Roychand, a Postdoctoral Research Fellow at RMIT University in Australia, found an interesting way to make stronger concrete, just add a little coffee. That will come in really handy, now that we have the technology to 3-D print affordable housing. Architects can get a lot more elaborate in their designs, save landfill space, and manage a finite resource, all at the same time.
A little coffee in your concrete
Simply tossing coffee grounds in the trash or running them down the sink annoyed him, so Dr. Roychand found a way to make stronger concrete. As that old Folger’s jingle goes, the best part of waking up is Folger’s in your cup. Nobody ever talks about those soggy droppings left behind by Mr. Coffee.
The good doctor likes to do his part for the planet, even though they are biodegradable, throwing them away still felt “wrong” to him. As a household item, used and soggy coffee grounds are everywhere.
It turns out that right now, there’s around 60 million tons of used coffee grounds being generated around the planet every year. When thrown away in the trash, “it contributes to the production of methane gas when it ends up in landfills.”
He decided to put his team on the job of giving coffee “a ‘double shot‘ at life.” They focused on the fact it’s a fine particle then settled on trying it as an additive for concrete.
They then decided on comparing the raw dried grounds with ones turned into “biochar” by heating them in the absence of air. They made two varieties of that, one at 350°C (662°F) and the other at 500°C (932°F).
After preparing the grounds, they added each variety to Portland cement, in the sand, at various mixes by volume. To test it, the team molded and cured the concrete. First at room temp for 24 hours then in water tanks. That was in preparation for compressive strength testing.
The Golidlocks mix
After all the concrete was properly hardened and tested, the data showed a clear winner. The raw grounds were effectively useless as an additive, so were the grounds pyrolyzed at the higher temperature. The 350°C biochar was a different story. It was just right and by mixing it with sand to 15% by overall volume, the team achieved “around 29.3 percent improvement in compressive strength.”
For architects, that means less materials to do the same job, along with a wider range of possibilities for free-form designs.
Humans have been building with concrete since the Romans mastered the art. Modern improvements like “shotcrete” and 3-D printing mean affordable housing for the masses. While buildings made of the medium can be square, dull and fortress like, they certainly don’t have to be.
Along with sweeping free-form designs and domes, pigments can be added to the material itself or paint in any color added later. You can even cover the entire structure in earth and grow things on it.
He still has some work to do convincing the construction trades to adopt his new concrete additive but Dr. Roychand calls it a “wake up call for the construction industry.”
Co-author of the study making the research public, Dr. Shannon Kilmartin-Lynch, notes “inspiration for my research, from an Indigenous perspective, involves Caring for Country, ensuring there’s a sustainable life cycle for all materials and avoiding things going into landfill to minimize the impact on the environment.“
