Nature has been a great source of inspiration for many of the things we use in our everyday lives. For example, velcro, new adhesives, and the Japanese bullet train have all been inspired by nature. Now, researchers have used the structure of nacre shells to develop a much more resistant cement than the one we use currently.
Nacre shells. Nacre shells aren’t just beautiful, they also have a unique construction. According to Princeton University researchers Shashank Gupta and Reza Moini, at the microscopic level, nacre consists of hexagonal tablets of the hard mineral aragonite glued together by a soft biopolymer.
Aragonite is a crystalline form of calcium carbonate (CaCO3) found in the shells of almost all mollusks and coral skeletons. The hexagonal tablet arrangement contributes to the strength of the nacre, while the biopolymer provides flexibility and crack resistance.
Reza Moini, on the left; Shashank Gupta, on the right. | Image: Princeton University
How does it work? According to Princeton, “the toughening mechanism involves the aragonite tablets sliding under stress, which, along with other mechanisms, allows the nacre to dissipate energy.” When combined with crack deflection and biopolymer deformation, nacre becomes capable of withstanding enormous mechanical stresses without losing its integrity.
What if you could replicate this? Using nacre as a base, Moini and Gupta developed a composite using conventional building materials: Portland cement paste and polyvinylsiloxane, which is used in dentistry to make molds for dental prostheses. They alternated layers of cement with thin layers of the polymer to form three types of beams with different structures.
This is what the concrete beam developed with this new material looks like. | Image: Princeton University
The result. One of the beams had separate hexagonal lozenges connected by the polymer layer, similar to the way aragonite is deposited on the biopolymer layer in nacre. Compared to a solid cement paste beam, the beam made with this new material proved to be 19 times more ductile and 17 times more resistant to cracking without losing strength.
The future. The Princeton researchers acknowledge that the findings are based on laboratory conditions and that more work is needed. They also want to explore if this technique could be applied to other materials, such as ceramics.
Image | Princeton University
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