Researchers at RMIT University (Melbourne, Australia) conducted a new experimental study to design special 3D-printing patterns based on the natural strength of lobster shells. These bio-mimicking spiral patterns not only improved the overall durability of 3D-printed concrete, but also provided structural support where needed.
By combining the spiral patterns with a special concrete mix enhanced with steel fibers, the research team from RMIT’s School of Engineering found that the resulting material was stronger than traditional concrete. The team investigated the effects of different printing patterns on the strength of steel fiber-enhanced concrete and published the results of their study in 3D Printing and Additive Manufacturing.
According to lead researcher Jonathan Tran, 3D printing and additive manufacturing have opened up opportunities for efficiency and creativity within the construction industry.
“3D concrete printing technology has real potential to revolutionize the construction industry, and our aim is to bring that transformation closer,” says Tran, a senior lecturer in structured materials and design at RMIT. “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 [3D concrete printing]. 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.”
Previous research from the RMIT team revealed that including 1-2% steel fibers in the concrete mix reduced defects and porosity, thereby increasing strength. These fibers also help harden the concrete early without deformation, enabling higher structures to be built.
The team tested the impact of printing concrete in helicoidal patterns, inspired by the internal structure of lobster shells, as well as cross-ply, quasi-isotropic, and standard unidirectional patterns. The results showed strength improvement from each of the patterns when compared with unidirectional printing, but the spiral patterns held the most promise, Tran notes.
“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,” he says. “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 research into 3D-printing concrete will be supported through a new, large-scale, mobile concrete 3D printer recently acquired by RMIT, thereby making it the first research institution in the southern hemisphere to commission a machine of this kind. The 5x5m robotic printer will be used by the RMIT team to research 3D printing of houses, buildings, and large structural components, as well as to explore the potential for 3D-printed concrete made with recycled waste materials such as soft plastic aggregate.
Source: RMIT University, www.rmit.edu.au.