Foundations for the future

Project AME – a collaboration between US researchers, businesses and organisations – had an ambition to design and fabricate the world’s first fully functioning and to scale 3D-printed excavator – a feat in which it was successful.

The excavator was unveiled at the CONEXPO-CON/AGG in Las Vegas in March 2017, and showcased the manufacturing possibilities available within the construction industry thanks to 3D printer technology.

The advent of 3D printer technology has opened up larger scale opportunities for the infrastructure sector, including building fabrication. The Eremo project in Italy successfully printed a house in 2017 with an environmental impact near zero as it used local materials from the area, including dirt, straw, lime and sand.

The progress being made in 3D building construction is evident in a number of unique examples around the world, including Australia.

Researchers from Swinburne University of Technology’s Centre for Sustainable Infrastructure successfully used Portland cement and geopolymer – a cement produced from industrial waste – separately as binders in 3D printing machines.

“3D printing is a hot topic at the moment and Swinburne University is very interested in its use in the mechanical, robotics and manufacturing facilities of the future. Within civil construction, we wanted to look at concrete and the possibilities of changing how we make it,” says Professor Jay Sanjayan, the Centre’s Director.

The breakthrough for the Swinburne team, led by Prof. Sanjayan, comes from adapting an existing 3D printing machine to use cement materials, including traditional Portland cement and geopolymer.

“We’ve been working on geopolymer for the past 20 years. It’s starting to be used as a cement alternative in infrastructure construction projects, including a large-scale application on an airport in Toowoomba,” Prof. Sanjayan says.

Because geopolymer cement mainly relies on industrial byproducts such as fly-ash or slag and minimally processed virgin resources in its makeup, it has a reduced carbon footprint and different durability benefits compared with Portland cement.

“Geopolymer is a lot more suitable for 3D printing because of its setting characteristics. Portland cement requires the application of a particular standard, which is difficult to change in design,” Prof. Sanjayan says. “Geopolymer is something we’ve created ourselves and can change the characteristics of to suit our needs.

“Geopolymer is more likely to be used in special applications where the Portland cement struggles to meet expectations,” he explains, adding that it can achieve up to 72 megapascals in strength without impeding structural capacity.

He says a Russian firm has also explored the concept of 3D printed geopolymer, but Swinburne is the only body exploring it in Australia.

“At the moment we’re trying to target construction, where concrete construction could be done in a more a cost-effective way,” Prof. Sanjayan says.

He says the 3D printed geopolymer application is best suited for unique componentry, unusually shaped concrete parts, intricate detailing and even ornamental structures. However, he adds, the possibility to use it for larger-scale and load-bearing structures is being explored.

A structure can be built through a layer-by-layer application of material through a 3D printing method, which allows a freeform type of construction that removes the need for formwork. It opens up different possibilities for the kind of concrete structure that can be produced, as well as improving cost and productivity savings.

“About 60 per cent of the costs in concrete construction is the formwork. That formwork consists of materials such as timber, which can only be used once or twice. Eighty per cent of the waste worldwide is coming from the construction industry, and formwork is likely a large part of that. If you can use 3D printing technology, we don’t need to use formwork,” Prof. Sanjayan explains.

3D printing also has the potential to improve quality control through construction automating, with Prof. Sanjayan asserting that machines are better at performing repetitive tasks with high accuracy.

While the advancements made by the Swinburne research team have been significant, Prof. Sanjayan says there are still many technological issues to overcome.

He says the rise in 3D printing capabilities for the construction sector is drawn from the aerospace and manufacturing industries where the technology has already found a solid footing. “In the past 20 to 30 years, these sectors really been driving it a lot more compared to the construction industry, which is still largely manual.”

Prof. Sanjayan says for the construction sector to adopt the 3D printing methods so well employed in the aerospace and manufacturing industries, there needs to be an effective technology transfer.

“We can access and bring the 3D printing technology over to the construction industry effectively because the hard work has already been done.

“The main issues we need to deal with is the size – we lift in tonnes, not kilos,” he says.

Because the aerospace industry deals in smaller applications, for instance, 3D printing needs to be to micrometre accuracy, whereas the construction and infrastructure sector requires closer to centimetre or millimetre accuracy.

“We can give up accuracy and make it up in cost because it’s the construction industry and it’ll need to be cost competitive,” Prof. Sanjayan points out.

While the Swinburne team has opened up opportunities in smaller construction applications for the 3D printed geopolymer, Prof. Sanjayan says they are beginning to explore how they can utilise the process for structural components.

“Another aspect we’re investigating is how to incorporate steel reinforcement into the technology, and we’re starting to work on polypropylene fibres as a steel alternative,” he says.

“Because it’s a new material, most of the applications for now need to be low risk, such as pavers and non-structural elements. Slowly, we need to consider using it to make load-bearing structures.”

Swinburne, in collaboration with the University of New South Wales, is also delivering a handbook guide for geopolymer concrete design and construction in general, which will be published by Standards Australia.

“We’re looking to specify geopolymer in construction and help encourage concrete companies to start supplying it,” Prof Sanjayan says.

“At the moment, there are no suppliers for geopolymer concrete in many states in Australia, which is limiting its implementation.”

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