3D-printed cement that gets stronger when it cracks
Credit: Purdue University Concrete 3D Printing Team/Mohamadreza Moini
By Idha Valeur
Researchers from Purdue University, USA, have 3D-printed a cement paste, which gets stronger and tougher when it cracks under pressure, much like the shells of lobsters and beetles.
In the future, this technique could contribute to the creation of more resilient buildings during natural disasters. Being able to 3D print has eliminated the previously needed process of creating moulds for every type of design which made it impossible to create these specialised properties of cement-based materials, according to Jeffrey Youngblood, professor of materials engineering at Purdue.
Jan Olek, Professor in Purdue’s Lyles School of Civil Engineering, said in a press release, ‘Nature has to deal with weaknesses to survive, so we are using the 'built-in' weaknesses of cement-based materials to increase their toughness.’
By creating and using designs based on arthropod shells, like the shells of lobsters and beetles, the team aims to control how damage spreads between the printed layers of a material.
Civil Engineering professor, Pablo Zavattieri, explained that the exoskeletons of the arthropods have crack propagation and toughening mechanisms, which the team can reproduce in a 3D-printed cement paste.
By also using micro-CT scans, the Purdue-team are able to better understand how the hardened 3D-printed cement-based materials behaves, and can then take advantage of weak characteristics, like pore regions found at the ‘interfaces’ between the layers, that promote cracking.
Being able to 3D print materials based on cement, such as cement paste, concrete and mortar will provide engineers with more control over performance as well as design. The team found that different paste elements provided new behaviours once hardened. The ‘Bouligand’ architecture will take advantage of weak interfaces to make a more crack-resistant material. The ‘compliant’ architecture, however, will make cement-based elements act like a spring despite that the material they are made of is brittle.
‘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 of civil engineering at Purdue University.