3D printing concrete beams. Minimass
I have called 3D-printed buildings a solution looking for a problem. In a recent post about 3D-printed homes, building tech expert Belinda Carr countered that "this is such a new industry and there is so much research and innovation going on, it is an extremely exciting industry to be in."
In very short order, she was proven correct, as I learned from Australian professor Philip Oldfield about Minimass—a 3D-printed concrete beam that is indeed a solution to a problem. It's designed by Andy Coward of Net Zero Projects Limited; he holds a 1st class degree in Civil and Structural Engineering from the University of Cambridge and has over 15 years of experience in design and construction. Prior to inventing Minimass, he held senior positions at Bjarke Ingels Group in Copenhagen as director of engineering and at Foster + Partners in London as associate partner.
He tells Treehugger, "My work was born out of the frustration of seeing the potential of 3D-printing being wasted. So I challenged myself to come up with a smart way of using the techniques."
A conventional beam versus a Minimass beam. Minimass
Reinforced concrete has a large carbon footprint due to the chemistry and the heat required to make cement, which is mixed with sand and aggregate to make concrete. Concrete is great in compression, which is what is happening to the top of the beam; the steel reinforcement at the bottom of the beam is in tension.
Most of the concrete in the middle is doing little more than providing the required distance between the top of the beam and the bottom. This is why every year, on Swedish Waffle Day, I get so excited about waffle slabs, which get rid of as much concrete as possible and have long spans. Alas, they have fallen out of favor because they are so labor-intensive.
A 3D-printed beam. Minimass
What Coward has done that is so remarkable is he designed a beam you would never try to build conventionally because of the complexity of the formwork required, but can be easily squirted out of a 3D printer. He has a chunk of concrete at the top for compression, triangles of concrete to act as the web and separate the top in compression from the bottom, and used a post-tensioned cable instead of conventional reinforcing in tension as the bottom.
Steel reinforcing. Minimass
Not only is the amount of concrete required reduced by 78%, but there is a 70% reduction in steel reinforcement. And of course, with 3D printing, there is no formwork—a significant saving. Coward also claims that "the new technique of 3D printing unlocks the potential of this design by allowing the fabrication of these beams at a fraction of the cost of traditional means."
The Pont du Truc de la Fare, a bridge in Bourgs-sur-Colagne, France. MOSSOT / Wikimedia Commons / CC BY-SA 4.0
Coward notes it is the same principle you see in bridges, such as Michel Virlogeux's Pont du Truc de la Fare in France, also a mix of concrete and steel.
The marvel of this is the dramatic reduction in the need for concrete, responsible for more than 7% of global carbon dioxide (CO2) emissions, and steel, which is responsible for as much as 9% of CO2 emissions. But where would one use such a beam? Coward tells Treehugger:
"At the moment, I am seeing interest in the warehouse/industrial/logistics markets. For example, long-span factory roof beams—normally made from steel but minimass would be cheaper and lower carbon. However, my background is projects with more architectural influence, so I also see great possibilities for other typologies such as office/commercial, cultural or large infrastructure e.g airports. Not residential or health, due to their general preference for flat soffits. Imagine a hybrid structure with CLT floor panels and long span minimass beams—releasing the timber building industry from the constraint of 6m [20-foot] grids."
Big beams in the Apex Plaza in Virginia. Prakash Patel Photography
This is a very interesting point. Cross-laminated timber (CLT) slabs are two-way, meaning they can be supported on columns without beams, but are limited to roughly 6 meters or 20 feet. To solve this problem, many designers use wood beams made of glue-laminated timber, as we recently showed in William McDonough + Partners' Apex Plaza in Charlottesville, Virginia. These were big honking beams with a lot of wood in them. While wood has a very low carbon footprint compared to conventional concrete construction, it still has an impact.
6 Orsman Road by Waugh Thistleton Architects. Ed Reeve
That's one reason that even the masters of mass timber, Waugh Thistleton, used a hybrid of steel beams on their 6 Orsman Road project. They got longer spans and they could punch the beams full of holes and run services through them instead of below them.
Beam with services from patent application. GB patent 2104096
This sketch from the patent application shows Coward is thinking about this too. Unlike a solid concrete beam, you can run services right through this, which can reduce building height and save money. Some have expressed concern about fireproofing, but Coward shows on the website how the cables can be treated with intumescent paint, can run in grouted ducts, or can have insulation applied in situ.
Some have also complained we shouldn't be using concrete at all when making it emits carbon dioxide and using mass timber stores it. But the science isn't settled about how much carbon is stored in mass timber, and how much is emitted from the roots and slash rotting and from kiln drying. I like to quote Paula Melton of BuildingGreen, who says: "Wood can be beneficial for its reduced footprint, but don’t use wood as a get-out-of-carbon-jail-free card. Consider which materials and systems make the most sense for the project, and optimize how you use them, preferably with whole-building life-cycle assessment as a guide."
One would have to do that life cycle assessment to figure out which has a lower carbon footprint and also take into account the time value of the carbon emissions. But as someone who preaches sufficiency—about using the least amount of anything that you can get away with—it sure looks like there is a whole lot less stuff in Coward's design. It really appears to live up to its name: Minimass.
Also check out the Minimass website, which I believe is a model of minimalist and elegant design.
