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.

 
 
 
 

Community-powered policies should be at the top of Westminster’s to do list

A generic election picture. Image: Getty.

Over the past five decades, political and economic power has become increasingly concentrated in the UK’s capital. Communities feel ignored or alienated by a politics that feels distant and unrepresentative of their daily experiences.

Since the EU referendum result it has become something of a cliché to talk about how to respond to the sense of powerlessness felt by too many people. The foundations of our economy have been shifted by Brexit, technology and deindustrialisation – and these have shone a light on a growing divergence in views and values across geographies and generations. They are both a symptom and cause of the breakdown of the ties that traditionally brought people together.

As the country goes through seismic changes in its outlook, politics and economy, it is clear that a new way of doing politics is needed. Empowering people to take control over the things that affect their daily lives cannot be done from the top down.

Last week, the Co-operative Party launched our policy platform for the General Election – the ideas and priorities we hope to see at the top of the next Parliament’s to do list. We have been the voice for co-operative values and principles in the places where decisions are made and laws are made. As co-operators, we believe that the principles that lie behind successful co‑operatives – democratic control by customers and workers, and a fair share of the wealth we create together – ought to extend to the wider economy and our society. As Labour’s sister party, we campaign for a government that puts these shared values into practice.

Our policy platform has community power at its heart, because the co-operative movement, founded on shop floors and factory production lines, knows that power should flow from the bottom up. Today, this principle holds strong – decisions are best made by the people impacted the most by them, and services work best when the service users have a voice. Our policy platform is clear: this means shifting power from Whitehall to local government, but it also means looking beyond the town hall. Co-operative approaches are about placing power directly in the hands of people and communities.


There are many great examples of Co-operative councillors and local communities taking the lead on this. Co-operative councils like Oldham and Plymouth have pioneered new working relationships with residents, underpinned by a genuine commitment to working with communities rather than merely doing things to them.

Building a fairer future is, by definition, a bottom-up endeavour. Oldham, Plymouth and examples like the Elephant Project in Greater Manchester, where people with experience of disadvantage are involved in decision-making, or buses in Witney run by Co-operative councillors and the local community – are the building blocks of creating a better politics and a fairer economy.

This thread runs through our work over the last few years on community wealth building too – keeping wealth circulating in local economies through growing the local co-operative sector. Worker-owned businesses thriving at the expense of global corporate giants and private outsourcers. Assets owned by communities – from pubs to post offices to rooftop solar panels.

And it runs through our work in Westminster too – with Co-operative MPs and peers calling for parents, not private business, to own and run nurseries; for the stewards of our countryside to be farmers rather than big landowners; and for workers to have a stake in their workplaces and a share of the profit.

Far from being ignored, as suggested in last week’s article on community power, our work has never been more relevant and our co-operative voice is louder than ever.

Anna Birley is policy offer at the Co-operative party.