Lobster shells strengthen 3D-printed concrete

Researchers are using patterns inspired by the internal structure of lobster shells to make 3D-printed concrete stronger.

A new experimental study by researchers at the Royal Melbourne
Institute of Technology (RMIT) in Australia has been “bio-mimicking” lobster
shells’ spiral pattern to increase the overall durability of 3D-printed
concrete.

The RMIT team has also combined
the twisting patterns with a specialised concrete
mix enhanced with steel fibres. It claimed that the resulting material
was stronger than traditionally made concrete. 

Currently, the conventional pattern used in 3D
printing is unidirectional, where layers are laid down on top of each
other in parallel lines.  

But the RMIT study found that including 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. 

Meanwhile, 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.  

The results showed strength improvement from each
of the patterns, compared with unidirectional
printing, but the helicoidal patterns showed the most promise
for supporting complex 3D printed concrete structures.  

Lead researcher Dr Jonathan Tran said 3D
printing and additive manufacturing opened up opportunities in
construction for boosting both efficiency and creativity.  

He said: “3D concrete printing technology has real potential
to revolutionise the construction industry, and our aim is to bring that transformation
closer.

“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.

“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.

“This work is in early stages so we need further
research to test how the concrete performs on a wider range of parameters, but
our initial experimental results show we are on the right track.”  

Further studies will be supported through a
new large-scale mobile concrete 3D printer recently acquired by RMIT
– making it 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 team will also use the machine to explore the potential
for 3D printing with concrete made with recycled waste materials such
as soft plastic aggregate. 

The work is connected to a new project with industry partners
Replas and SR Engineering, focusing on sound-dampening walls made from
post-consumer recycled soft plastics and concrete, which was recently supported
with an Australian Government Innovations Connections grant.