Here’s the science behind 3D printing in construction

A mock-up of 3D printers building a bridge in Amsterdam. Image: MX3D.

It’s often claimed that 3D printing – known in the trade as “additive manufacturing” – will change the way we live. Most recently, a team from Eindhoven University of Technology announced plans to build the “world’s first” habitable 3D printed houses. But it’s one thing to build small, prototype homes in a park – it’s quite another to successfully use additive manufacturing for large scale projects in the construction sector.

Additive manufacturing uses a combination of materials science, architecture and design, computation and robotics. Yet in some ways, it’s not as futuristic as it sounds. The simple approach of layer-wise construction – where building materials are layered on top of each other to create a facade – has already been practised for a long time in the construction sector, for example in conventional brick layering techniques.

The true novelty of additive manufacturing lies in its ability to combine new, highly efficient and sustainable materials with architectural design software and robotic technology, to automate and improve processes that have already been proven manually. In this sense, additive manufacturing holds many potentially groundbreaking benefits for the construction sector.

3D printing can produce up to 30 per cent less material waste, use less energy and fewer resources, enable in-situ production (which in turn cuts transport costs), grant greater architectural freedom and generate fewer CO₂ emissions over the entire lifecycle of the product.

Printable feedstocks

But there is still some way to go before additive manufacturing technology can deliver on its potential. There are several different components of additive manufacturing, each of which must be developed and refined before the process can be successfully used in large-scale construction.


One component is printable feedstocks – the materials which are actually “printed” to create the final product. There are many types of printable feedstock, but the most relevant one for large scale construction is concrete. Printable feedstocks are typically made from a combination of bulk materials – such as soil, sand, crushed stone, clay and recycled materials – mixed with a binder such as Portland cement, fly ash or polymers, as well as other additives and chemical agents to allow the concrete to set faster and maintain its shape, so that the layers can be deposited rapidly.

In a project I am currently working on at Brunel University, we are focusing on producing a printable cement feedstock. To create materials for 3D printed constructions, scientists must carefully control the setting time of the paste, the stability of first few layers and the bonding between the layers. The behaviour of the materials must be thoroughly investigated under a range of conditions, to achieve a robust structure which can take load.

The combination of cement, sand and other additives must be just right, so that the feedstocks don’t set while still in the printer, and don’t stay wet for too long once they have been deposited to form a structure. Different grades of feedstock need to be formulated and developed, so that this technology can be used to build a range of different structural elements, such as load-bearing and large-scale building blocks.

Building blocks

Another component is the printer, which must have a powerful pump to suit the scale of manufacturing in the construction industry. The pressure and flow rate of the printer must be trialled with different types of feedstocks. The speed and the size of the printer is key to achieving a good print quality: smooth surface, square edges and a consistent width and height for each layer.

How quickly the feedstock materials are deposited – typically measured in centimetres per hour – can speed up or slow down construction. Decreasing the setting time of the feedstock means that the printer can work faster – but it also puts the feedstock at risk of hardening inside the printer system. The printing system should be optimised to continuously deliver the feedstock materials at a constant rate, so that the layers can fuse together evenly.

The geometry of the structures produced is the final piece of the puzzle, when it comes to using 3D printing in construction. When the printer and the feedstock have been properly set up, they will be able to produce full-size building blocks with a smart geometry which can take load without reinforcements. The shape stability of the truss-like filaments in these blocks is an essential part of printing, which provides strength and stiffness to the printed objects.

The ConversationThis three-pronged approach to adapting additive manufacturing for construction could revolutionise the industry within the next ten to 15 years. But before that can happen, scientists need to fine tune the mix ratios for the feedstocks, and refine a printing system which can cope with the rapid manufacturing of building blocks. Only then can the potential of 3D printing be harnessed to build faster, and more sustainably, than ever before.

Seyed Ghaffar, Assistant Professor in Civil Engineering and Environmental Materials, Brunel University London.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

17 things the proposed “Tulip” skyscraper that London mayor Sadiq Khan just scrapped definitely resembled

Artist's impression. See if you can guess which one The Tulip is. Image: Foster + Partners.

Sadiq Khan has scrapped plans to build a massive glass thing in the City of London, on the grounds it would knacker London’s skyline. The “Tulip” would have been a narrow, 300m skyscraper, designed by Norman Foster’s Foster & Partners, with a viewing platform at the top. Following the mayor’s intervention, it now won’t be anything of the sort.

This may be no bad thing. For one thing, a lot of very important and clever people have been noisily unconvinced by the design. Take this statement from Duncan Wilson, the chief executive of Historic England, from earlier this year: “This building, a lift shaft with a bulge on top, would damage the very thing its developers claim they will deliver – tourism and views of London’s extraordinary heritage.”

More to the point, the design was just bloody silly. Here are some other things that, if it had been built, the Tulip would definitely have looked like.

1. A matchstick.

2. A drumstick.

3. A cotton ear bud.

4. A mystical staff, of the sort that might be wielded by Gandalf the Grey.

5. A giant spring onion.

6. A can of deodorant, from one of the brands whose cans are seemingly deliberately designed in such a way so as to remind male shoppers of the fact that they have a penis.

7. A device for unblocking a drain.

8. One of those lights that’s meant to resemble a candle.

9. A swab stick, of the sort sometimes used at sexual health clinics, in close proximity to somebody’s penis.

10.  A nearly finished lollipop.

11. Something a child would make from a pipe cleaner in art class, which you then have to pretend to be impressed by and keep on show for the next six months.

12. An arcology, of the sort seen in classic video game SimCity 2000.

13. Something you would order online and then pray will arrive in unmarked packaging.

14. The part of the male anatomy that the thing you are ordering online is meant to be a more impressive replica of.

15. A building that appears on the London skyline in the Star Trek franchise, in an attempt to communicate that we are looking at the FUTURE.


14a. Sorry, the one before last was a bit vague. What I actually meant was: a penis.

16. A long thin tube with a confusing bulbous bit on the end.

17. A stamen. Which, for avoidance of doubt, is a plant’s penis.

One thing it definitely does not resemble:

A sodding tulip.

Anyway, it’s bad, and it’s good the mayor has blocked it.

That’s it, that’s the take.

(Thanks to Anoosh Chakelian, Jasper Jackson, Patrick Maguire for helping me get to 17.)

Jonn Elledge is editor of CityMetric and the assistant editor of the New Statesman. He is on Twitter as @jonnelledge and on Facebook as JonnElledgeWrites.

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