Bio-Inspired Patterns can Help Make Stronger 3D-Printed Concrete

According to a new study, bio-inspired patterns such as lobster shells, can render 3D-printed concrete more robust and thus support more creative and complex architectural structures.

In fact, 3D concrete printing (3DCP) is one of the digital manufacturing technologies and has excellent potential to save material, time, and effort involved in construction. These technologies also have immense potential to push the boundaries of architectural advancements, but due to the prevailing technical challenges, 3D printed concrete is not sufficiently strong to use in more free-form structures.

Now, in a recent experimental analysis, RMIT University researchers have turned their focus on the natural strength of lobster shells to develop unique 3D printing patterns.

The bio-mimicking spiral patterns designed by the researchers not only enhance the overall strength of the 3D-printed concrete but also allowed the team to accurately direct the strength for structural support where required.

When the researchers integrated the twisting patterns with a dedicated concrete mix improved with steel fibers, the material that was obtained was more robust when compared to conventionally-made concrete.

According to lead researcher Dr Jonathan Tran, additive manufacturing and 3D printing have made inroads in the construction field for increasing both creativity and efficiency.

3D concrete printing technology has real potential to revolutionise the construction industry, and our aim is to bring that transformation closer. Our study explores how different printing patterns affect the structural integrity of 3D printed concrete, and for the first time reveals the benefits of a bio-inspired approach in 3DCP.

Dr Jonathan Tran, Lead Researcher and Senior Lecturer, Structured Materials and Design, RMIT University

“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,” added Dr Tran.

3D Printing for Construction

Thanks to the automation of concrete construction, the way people build structures will be completely transformed, and added to this, construction has become the next frontier in the data-driven and automation revolution, called industry 4.0.

A 3D concrete printer makes structural components or builds homes by depositing the material in a layer-by-layer fashion, which is completely different from the conventional method of casting concrete in a mold.

Thanks to the new technology, a home can now be 3D printed in just a single day for around 50% of the cost, while construction on the first-ever 3D printed community was started in Mexico in 2019.

The emerging sector is already supporting engineering and architectural innovation, like a nature-mimicking concrete bridge in Madrid, a 3D printed office building in Dubai, and a sail-shaped “Europe Building” in The Netherlands.

The researchers from the School of Engineering at RMIT University focus on 3D printing concrete, investigating ways to improve the completed product using different combinations of material choices, printing pattern design, design optimization, modeling, and reinforcement choices.

Patterns for Printing

Unidirectional is the most traditional pattern employed in 3D printing. In this pattern, layers are arranged on top of one another in parallel lines.

Published in a special issue of the 3D Printing and Additive Manufacturing journal, the new study assessed the impact of different patterns of printing on the strength of steel fiber-enhanced concrete.

Prior studies performed by the researchers from RMIT University discovered that when the concrete mix is combined with 1% to 2% steel fibers, porosity and defects are reduced, and strength is increased. Besides this, the fibers allow the concrete to become strong much earlier and without any sign of deformation, thus allowing the construction of higher structures.

The researchers tested the effect of printing the concrete in helicoidal patterns (taking a cue from the inner structure of lobster shells), regular unidirectional patterns, and cross-ply and quasi-isotropic patterns (analogous to those utilized for layer-by-layer deposited composites and laminated composite structures).

Supporting Complex Structures

The outcomes demonstrated strength enhancement in all of the patterns, in comparison to unidirectional printing; however, according to Dr Tran, the spiral patterns have the most potential for supporting intricate 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. 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.

Dr Jonathan Tran, Lead Researcher and Senior Lecturer, Structured Materials and Design, RMIT University

Additional research works will be supported via a novel large-scale mobile concrete 3D printer that was recently procured by RMIT University—rendering it the first research institution in the southern hemisphere to commission this kind of a machine.

The team will use the robotic printer, measuring 5 × 5 m, to study the 3D printing of buildings, houses, and large structural components.

The researchers will also utilize the robotic printer to investigate the possibility of 3D printing with concrete developed with recycled waste materials, like soft plastic aggregate.

The study is related to new research work with industry associates Replas and SR Engineering, and focuses on sound-dampening walls created from post-consumer recycled and concrete, which was supported with an Australian Government Innovations Connections grant.

Study collaborators were Luong Pham, first author and Ph.D. researcher from RMIT University and Professor Guoxing Lu from Swinburne University.

Video Credit: RMIT University

Journal Reference:

Pham, L., et al. (2020) Influences of printing pattern on mechanical performance of 3D printed fibre-reinforced concrete. 3D Printing and Additive Manufacturing. doi.org/10.1089/3dp.2020.0172.