Fixes for the Future | Printing buildings

Out in the modern world it’s pretty hard to avoid concrete; after water, it’s the most widely used substance on the planet. Yet, the concrete construction industry has seen little increase in productivity for decades. According to research by the McKinsey Global Institute, while sectors such as agriculture and manufacturing have increased productivity more than tenfold in recent decades, the construction sector remains stuck at the level of the mid-1900s. 

Marchant van den Heever, Centre for Development of Sustainable Infrastructure

That’s largely because of the manual nature of the industry: human hands still lay brick onto brick or pour liquid concrete into formwork of wood and steel. The digital revolution has, with few exceptions, yet to transform the world of construction.

That, however, is beginning to change, as advances are made in the world of three-dimensional concrete printing. It may seem like the realm of science fiction but a team of engineers at Stellenbosch University is breaking new ground in unlocking the potential for this brave new world of building.

“The whole world is moving to digital manufacturing processes and I think the construction industry has been a bit slow to jump on the bandwagon,” says Marchant van den Heever, a PhD candidate in the Department of Civil Engineering. “But within the next five to 10 years, we’ll see a lot of buildings, or parts of buildings, being created using 3D concrete printing technology.” 

Working under the guidance of Professor Gideon van Zijl and alongside fellow PhD and master’s students in the Centre for Development of Sustainable Infrastructure, Marchant is part of the team leading local innovation in large-scale three-dimensional concrete printing. “We’re looking at everything from materials to the mechanics of the building. How strong is a 3D printed wall? Where are the issues with durability? Where are the potential savings?” he explains.

Fine-tuning the printing process is, perhaps surprisingly, just a small part of the overall project. For starters, the team has had to build their gantry-style printer from the ground up. After success with the initial prototype, they are currently constructing a larger three-square-metre printer. But that was only part of the challenge; the next step was developing the material to print with.

“It’s quite a complex process,” says Marchant. “We’ve looked at fibre-reinforced composites within the concrete, we’ve developed a foam concrete that reduces weight and has additional properties such as insulation. The main driver of what we’re trying to do is to move away from having a mould that you cast the concrete into and rather deposit material precisely where you need it.”

Three-dimensional concrete printing could bring a raft of benefits in terms of cost, environmental impact and sustainability. Along with its increased flexibility in design, it does away with the need for wasteful and expensive formwork moulds, while reducing the volume of concrete reduces time, cost, weight and environmental impact. Globally, concrete production is one of the worst culprits when it comes to climate change, being responsible for about 8% of all carbon dioxide emissions.

In South Africa, however, where labour-intensive construction is a key employer, will 3D concrete printing – the final step in the digital-based design and management of the construction process – spell the end of the traditional building industry? It’s unlikely, says Marchant, since 3D concrete printing is merely one tool in the construction toolbox. “I think we’ll see the industry using the new technology where it can add value, but staying with existing practices where they are still necessary and useful.” 

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