Researchers have created a 3D-printed cement paste that gets stronger when it cracks, paving the way for buildings that are more resilient to earthquakes, a study has found.
The cement paste, a key ingredient of the concrete and mortar used to build various elements of infrastructure, that gets tougher under pressure like the shells of arthropods such as lobsters and beetles.
"Nature has to deal with weaknesses to survive, so we are using the 'built-in' weaknesses of cement-based materials to increase their toughness," said Jan Olek, a professor at Purdue University in the US.
The idea would be 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 at Purdue University.
3D-printed cement-based materials -- such as cement paste, mortar and concrete -- would give engineers more control over design and performance, but technicalities have stood in the way of scaling them up.
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"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 at Purdue.
The team is also using micro-CT scans to better understand the behaviour of hardened 3D-printed cement-based materials and 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 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.