Researchers at RMIT University are studying the spiral patterns in lobster shells to strengthen 3D printed concrete that can support more complex architectural structures. 

With digital manufacturing technologies such as 3D concrete printing (3DCP) entering the construction industry, there is immense potential for project stakeholders to save time, effort and material, leading to significant cost reduction. Additionally, these technologies promise to push the boundaries of architectural innovation by allowing more creative designs in construction.

For the experimental study published in a special issue of 3D Printing and Additive Manufacturing, the researchers looked to the natural strength of lobster shells to design special 3D printing patterns. The team combined the twisting patterns with a specialised concrete mix enhanced with steel fibres to create a material stronger than traditional concrete. The biomimicking of spiral patterns improved the overall durability of the 3D printed concrete while also enabling the strength to be precisely directed for structural support where needed. 

Observing that 3D printing and additive manufacturing opened up opportunities in construction for boosting both efficiency and creativity, lead researcher Dr Jonathan Tran said, “3D concrete printing technology has real potential to revolutionise the construction industry, and our aim is to bring that transformation closer.”

Tran, a senior lecturer in structured materials and design at RMIT, explained that their study explored how different printing patterns affected the structural integrity of 3D printed concrete, revealing for the first time, the benefits of a bio-inspired approach in 3DCP.  

“We know that natural materials like lobster exoskeletons have evolved into high-performance structures over millions of years, so by mimicking their key advantages we can follow where nature has already innovated.” 

3D printing in construction 

Construction is the next frontier in the Industry 4.0 revolution, with the automation of concrete construction set to transform how we build. Technologies such as 3D concrete printing can complete a house in just 24 hours at about half the cost.

This emerging industry is already supporting architectural and engineering innovation such as a 3D printed office building in Dubai, a nature-mimicking concrete bridge in Madrid and the sail-shaped ‘Europe Building’ in The Netherlands. Construction on the world's first 3D printed community also began in Mexico in 2019. 

Focussed on 3D printing concrete, the research team in RMIT’s School of Engineering is exploring ways to enhance the finished product through different combinations of printing pattern design, material choices, modelling, design optimisation and reinforcement options. 

Patterns for printing 

Conventionally, patterns used in 3D printing are unidirectional with layers laid in parallel lines. The RMIT team studied the effect of different printing patterns on the strength of steel fibre-enhanced concrete. Key findings from a previous research by the team revealed that the inclusion of 1-2% steel fibres in the concrete mix reduces defects and porosity, increasing strength. The fibres also help the concrete harden early without deformation, enabling higher structures to be built. 

The team tested the impact of printing the concrete in helicoidal patterns (inspired by the internal structure of lobster shells), cross-ply and quasi-isotropic patterns (similar to those used for laminated composite structures and layer-by-layer deposited composites) and standard unidirectional patterns.  

Compared with unidirectional patterns, the results showed strength improvement with spiral patterns holding the most promise for supporting complex 3D printed concrete structures.  

“As lobster shells are naturally strong and naturally curved, we know this could help us deliver stronger concrete shapes like arches and flowing or twisted structures,” Tran said. However, further research is needed to test how this concrete performs on a wider range of parameters, he noted.  

The researchers will be using a new large-scale mobile concrete 3D printer recently acquired by RMIT –the first research institution in the southern hemisphere to commission a machine of this kind. The 5×5m robotic printer will be used by the team to research the 3D printing of houses, buildings and large structural components. The machine will also be used to explore the potential for 3D printing with concrete made using recycled waste materials. 

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