A research team at the University of New Mexico has developed a patented material that could shape the future of construction with 3D printing. The work of the team, led by Maryam Hojati, assistant professor of civil and environmental engineering, aims to overcome the limitations of traditional concrete materials. The result: a self-reinforcing, ultra-ductile cementitious material that can be both bent and printed.
Concrete is essential in the construction industry, but shows weaknesses when subjected to tensile loads, such as those caused by natural disasters or weathering. These brittle properties usually require reinforcements such as steel, but these are difficult to combine with the automation of 3D printing. “Concrete by itself does not show any tensile properties, meaning if you have a piece of concrete and start pulling it apart, it can easily break. It’s a very brittle material,” Hojati said. This is where the team comes in to develop a solution that is both strong and printable without resorting to conventional reinforcement.
The patented material consists of a precise blend of fibers such as polyvinyl alcohol, ultra-high molecular weight polyethylene fibers, silica fume and fly ash. These components ensure high flexural and tensile strength, while the viscosity is adjusted so that the material can flow easily through pressure nozzles. The material development required numerous tests, including tensile tests and bending tests on various prototypes.
“If we talk about 3D printing or additive manufacturing in the field of metals and plastics, it’s at a very advanced stage, but concrete printing is still developing,” Zafar Bakhshi, who worked on the project as a research assistant and master’s degree student early in its development, said. “If we can successfully design ultrahigh ductile material without using conventional steel bars, which will solve the problem of the incompatibility of reinforcement with the 3D printing process.”
“Because of the incorporation of large quantities of short polymeric fibers in this material, it could hold all of the concrete together when subjected to any bending or tension load,” Hojati said. “If we use this material at a larger scale, we can minimize the requirement of external reinforcement to the printed concrete structure.”
The potential applications are many and varied. In addition to potential use in construction on Earth, such materials could also play a role in space research. As transporting heavy construction materials into space is not practical, organizations such as NASA are working on robotic 3D printing. Materials like those used by Hojati’s team could be crucial here.
The research was funded by the Tran-SET program, which focuses on sustainable construction innovations. In addition to the development of bendable concrete, the team is also dedicated to researching environmentally friendly materials and their potential applications in 3D printing.
“This was very successful research. This material has 3D printing property and very high structural viability that could be used in the construction industry,” Hojati said.
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