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.

 
 
 
 

On boarded-up storefronts, muralists offer words of hope

The murals on closed storefronts aim "to end ugly wall syndrome." (Courtesy of Beautify)

In Los Angeles, Melrose Avenue has a new mural that reads: “Cancel plans, not humanity.”

It’s an artwork by Corie Mattie, a street artist who kindly reminds us of our togetherness under quarantine. She and many other artists are putting murals up across the US as part of the Back to the Streets campaign, which aims to add some color to the streets – specifically on boarded up storefronts and abandoned streets that feel deserted during the coronavirus pandemic.

The goal is to bring some beauty to the streets while everything is boarded up – “to end ugly wall syndrome,” says project founder Evan Meyer. “It’s to get people to care about their communities, be part of the process.” 


Many of the murals are painted on plywood panels that cover the entryways to independent businesses that have shut down during the pandemic. The project aims to prevent a sense of decay, especially as some businesses start to open back up while their neighbours remain closed.

“We need to protect our streets from becoming sad places quickly, when places are abandoned and don’t feel like they have love or life,” says Meyer, who is also the CEO of Beautify, a company that connects artists with places to make murals. Among the murals made during the pandemic, one at a department store says “Togetherness,” while another says: “You can’t quarantine love.”

“We’re seeing messages like hope, positivity and community,” Meyer says. “More than ever, it’s a time for community.”


(Courtesy of Beautify)

With artist-led projects in L.A., Seattle, San Francisco, Santa Monica, Pasadena, and others, the goal is to get 1,000 murals up across America. Murals are also being painted in small towns in Iowa, like Council Bluffs and Dubuque, and an earlier mural in New York City’s Rockaway Beach was created in 2014 with the same goal of bringing some life to neglected buildings that needed renovation after Hurricane Sandy

“We need to protect our streets from becoming sad places with broken windows, tagging and crime,” says Meyer. “A lot can happen if a place feels like it’s unwatched.” 

Los Angeles councilmember David Ryu endorsed the initiative in a recent blog post, saying it has helped boost morale on the streets of L.A. “When we brighten blighted walls, we improve neighborhoods,” he wrote. “It’s critical to have more business owners enlist their walls here to bring some much needed love and recognition to their establishment and their neighborhood.” 

The effort stems from a sister project called Beautify Earth, which has helped address a litter problem in Santa Monica’s commercial district. In addition to a cleanup force, the project has painted more than 100 murals on walls, dumpsters, utility boxes and garbage cans across the city.

On the Beautify website, artists can find business improvement districts, real estate developers, landlords and business owners who want to see something on their empty walls. Each artist who gets a commissioned wall through the Beautify website is paid 78% of the stipend, and Beautify takes a 22% administration fee. 

Meyer says he often explains to business owners that art can help their business.

“A lot of people have white empty wall space on their liquor stores, condos, park walls, even residential spaces,” says Meyer, adding that many are afraid to put something on their walls. “It’s not a liability, it’s an asset. Art protects walls, it is a graffiti abatement strategy.”


(Courtesy of Beautify)

Beautify isn’t alone in its field. Among the other cities that have similar mural projects, ArtPlace America has supported over 200 art murals across the US. Wynwood Walls, a public art project in Miami spearheaded by local developer Tony Goldman, has helped create a popular public art hotspot with murals by artists Shepard Fairey and Ron English. 

Chicago’s city government, too, has publicly funded over 500 murals through its Percent-for-Art program, which pays artists to paint walls on municipal buildings. A grassroots street art project in the state of Zacatecas, Mexico, has artists painting murals in violent and marginalised neighbourhoods. Similar crime prevention ventures have been initiated in Topeka, Kansas, in St. Louis, Missouri, and in Toronto, Canada, which has placed over 140 murals across the city over the past decade. 


Artist Ruben Rojas has painted murals saying "You Can't Quarantine Love" in several spots across Santa Monica, California. (Courtesy of Beautify)

One artist working with Beautify’s project is Ruben Rojas, who is overwhelmed by the response to his mural, “You Can’t Quarantine Love,” which has been painted in several spots across Santa Monica and beyond.

“Every day, I see the shares, photos of my murals, amazing captions and direct messages from folks that are truly heartwarming,” Rojas says. “I’ve seen this particular mural go around the world with ‘thank you’ messages from Johannesburg, Germany, and Italy. It really is humbling.”

Meyer says that kind of social media engagement shows how a mural can turn a plain old wall into a landmark. 

“Murals get seen,” he says. “People take photos and share them on social media. Nobody takes photos of your ugly white wall. Murals are the story of the local community.”

Nadja Sayej is an arts and culture journalist based in New York City.