New crack-resistant cement material inspired by nature

A research team led by Reza Moini, assistant professor of civil and environmental engineering at Princeton University, has developed a new cement-based composite material that is remarkably more resistant to cracking and more flexible than standard cement.

The results, published June 10 in the journal Advanced functional materialscould revolutionize the construction industry and improve the safety and durability of a wide range of fragile ceramic materials.

Nature’s plan provides a secret recipe

The inspiration for this innovative cement composite came from an unlikely source: the material that makes up oyster and abalone shells, known as nacre or nacre.

Shashank Gupta, a graduate student in Moini’s lab at Princeton University, explained that at the microscopic level, nacre is made of hexagonal tablets of a hard mineral called aragonite, held together by a soft biopolymer.

“This synergy between hard and soft components is crucial for nacre’s remarkable mechanical properties,” Gupta said.

The aragonite tablets contribute significantly to the strength of the nacre, while the biopolymer adds flexibility and crack resistance.

When subjected to stress, the aragonite tablets slide, allowing the nacre to dissipate its energy and maintain its structural integrity, making it both strong and resilient.

Engineering a stronger cementitious material

Inspired by the unique properties of nacre, the Princeton team decided to create a cement composite that mimics its structure using conventional building materials like Portland cement paste and a limited amount of polymer.

The researchers created small, multi-layer beams by alternating sheets of cement paste with thin layers of a highly stretchable polymer called polyvinylsiloxane.

They then subjected these beams to a three-point bending test to assess their resistance to cracking and their fracture toughness.

The team produced three types of beams:

one with alternating layers of cement paste sheets and thin polymer
another with hexagonal grooves etched into sheets of cement paste using a laser
a third with completely separate hexagonal tablets connected by the polymer layer, in the same way that aragonite sits on top of the biopolymer layer in nacre

The experiments revealed that bundles with completely separated hexagonal tablets, which closely resemble the structure of nacre, showed the most significant improvements.

These beams demonstrated 19 times greater ductility and 17 times greater fracture strength while maintaining almost the same strength as the solid cement paste beam.

“Our bio-inspired approach is not simply about mimicking the microstructure of nature, but about learning underlying principles and using them to inform the engineering of human-made materials,” Moini said. “We intentionally design defects into fragile materials to make them stronger by design.”

New era in cement building materials

Although the results are based on laboratory conditions and further research is needed to develop the techniques for use in the field, the potential implications for the construction industry are vast.

“If we can design concrete to resist crack propagation, we can make it stronger, safer and more durable,” Gupta said.

Researchers are trying to determine whether the fracture toughness and ductility of structures apply to other ceramic materials other than cement paste, such as concrete.

“We are only scratching the surface; There will be many design opportunities to explore and design the constituent properties of hard and soft materials, interfaces and geometric aspects that play into fundamental size effects in building materials,” said Moini.

Crack-resistant cement inspired by nature

In short, the research conducted by Princeton engineers opens a world of possibilities for creating stronger, safer and more durable building materials.

Taking inspiration from the intricate design of nacre found in oyster and abalone shells, the team developed a cement composite that significantly improves crack resistance and flexibility.

As researchers continue to explore the potential applications of this bio-inspired approach, the construction industry stands to benefit from a new era of resilient and sustainable materials.

The future of building is in the hands of innovative minds who dare to look to nature for solutions, and the Princeton team has taken a significant step forward in cracking the code of engineering resilience.

The full study was published in the journal Advanced functional materials.

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