A bioinspired cement paste element being produced by 3D printing. Photo: Purdue University Concrete 3D Printing Team/Mohamadreza Moini.
A bioinspired cement paste element being produced by 3D printing. Photo: Purdue University Concrete 3D Printing Team/Mohamadreza Moini.

Researchers at Purdue University have 3D-printed a cement paste, a key ingredient of the concrete and mortar used to build various elements of infrastructure, that gets tougher under pressure, just like the shells of arthropods such as lobsters and beetles. The technique could eventually contribute to the creation of structures that are more resilient during natural disasters.

"Nature has to deal with weaknesses to survive, so we are using the 'built-in' weaknesses of cement-based materials to increase their toughness," explained Jan Olek, a professor in Purdue's Lyles School of Civil Engineering.

The idea is to use designs inspired by arthropod shells to control how damage spreads between the printed layers of a material, like trying to break a bunch of uncooked spaghetti noodles as opposed to a single noodle. "The exoskeletons of arthropods have crack propagation and toughening mechanisms that we can reproduce in 3D-printed cement paste," said Pablo Zavattieri, a professor of civil engineering at Purdue.

Printing cement-based materials like cement paste, mortar and concrete would give engineers more control over design and performance, but technicalities have stood in the way of doing it at large scales. The Purdue engineers are the first to use 3D printing to create bioinspired structures using cement paste, as reported in a paper in Advanced Materials.

"3D printing has removed the need for creating a mold for each type of design, so that we can achieve these unique properties of cement-based materials that were not possible before," said Jeffrey Youngblood, a professor of materials engineering at Purdue.

The team is also using micro-CT scans to better understand the behavior of hardened, 3D-printed, cement-based materials and to take advantage of their weak characteristics, such as pore regions found at the ‘interfaces’ between the printed layers, which promote cracking.

"3D printing cement-based materials provides control over their structure, which can lead to the creation of more damage and flaw-tolerant structural elements like beams or columns," said Mohamadreza ‘Reza’ Moini, a PhD candidate in civil engineering at Purdue.

The team was initially inspired by the mantis shrimp, which conquers its prey with a ‘dactyl club’ appendage that grows tougher on impact through twisting cracks that dissipate energy and prevent the club from falling apart. Some of the bioinspired cement paste elements designed and fabricated by the team using 3D printing techniques include the ‘honeycomb’, ‘compliant’ and ‘Bouligand’ designs, which they term ‘architectures’.

Each of these architectures allowed for new behaviors in a 3D-printed element once hardened. The Bouligand architecture, for example, takes advantage of weak interfaces to make a material more crack-resistant, whereas the compliant architecture makes cement-based elements act like a spring, even though they are made of brittle material. The team now plans to explore other ways that cement-based elements could be designed for building more resilient structures.

This story is adapted from material from Purdue University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.