Healthy Food Delivery : Scientists Use Mollusk Shell Secrets to Create Super-Strength Concrete

Cement is the most commonly used construction material in the world, used to create everything from skyscrapers to sidewalks. To meet the demands of global industries, over 4 billion tons of cement are produced annually. That’s good for cement manufacturers, but not so great for the environment. It’s estimated that anywhere from 4 to 8 percent of all CO2 emissions around the globe come from concrete production.

But what if cement were less brittle and more malleable? Would we still need as much of it? Those are the questions being asked by researchers at Princeton, who claim to have crafted a new formula for cement that’s 17 times tougher and 19 times more ductile than typical cast cement.

The secret to the strength? Believe it or not… It’s mollusks. Here’s a look at how this new cement was developed, how it was tested, and how it could be applied to future construction projects.

Mollusks?

Yes, mollusks. Mollusks have a special composite material lining their inner shell, known as “nacre.” Nacre, also known as “mother of pearl,” has traditionally been used in jewelry shops. But it also has some intriguing properties on a molecular level — properties that caught the eye of our Princeton researchers.

If you look at nacre under a microscope, you’ll see what looks like hexagonal sheets or tablets of slate. Those hexagons are made of argonite, and they’re connected by a soft biopolymer. That microscopic interaction between those hard argonite hexagons and the biopolymer binding them is exactly what Princeton researchers think could change the way the world produces cement.

“This synergy between the hard and soft components is crucial to nacre’s remarkable mechanical properties,” Shashank Gupta, a co-author of the study and graduate student at Princeton, said in a press statement. “If we can engineer concrete to resist crack propagation, we can make it tougher, safer and more durable.”

How Was the New Formula Tested?

To test their idea, the Princeton lab conducted a relatively straightforward test. They created three beams made from alternating sheets of cement and thin polymer layers. For the first beam, the cement and polymer were just layered on top of each other. For the other two, hexagonal grooves were cut into the cement at various depths, allowing the beams to fully mimic the molecular structure of nacre.

Those three beams were then tested and compared to a regular cement beam with no polymer layers or hexagonal grooves. The results were conclusive: all three beams with the polymer were more ductile and tougher than the standard beam. The beam featuring deep cut hexagonal lates and the polymer saw the largest increase in toughness and ductility. Just as importantly, it did not lose any strength compared to the standard concrete.

“Our bio-inspired approach is not to simply mimic nature’s microstructure but to learn from the underlying principles and use that to inform the engineering of human-made materials. One of the key mechanisms that makes a nacreous shell tough is the sliding of the tablet at the nanometer level,” Reza Moini, a coauthor of the study, said in a press statement. “In other words, we intentionally engineer defects in the brittle materials as a way to make them stronger by design.”

What Happens Next?

Concrete that’s inherently tougher and more ductile would have numerous practical applications worldwide. The Princeton researchers noted that their results are based on lab conditions, and further testing and research are needed before this technique is applied in the field.

“We are only scratching the surface; there will be numerous design possibilities to explore and engineer the constitutive hard and soft material properties, the interfaces, and the geometric aspects that play into the fundamental size effects in construction materials,” Moini said.