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06-17-2024

New crack-resistant cement material inspired by nature

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

The findings, published on June 10 in the journal Advanced Functional Materials, could revolutionize the construction industry and improve the safety and durability of a wide range of brittle ceramic materials.

Nature’s blueprint provides 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 mother of pearl.

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

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

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

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

Engineering a tougher cement material

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

The researchers created multi-layered small beams by alternating cement paste sheets with thin layers of a highly stretchable polymer called polyvinyl siloxane.

They then subjected these beams to a notched three-point bending test to evaluate their crack resistance and fracture toughness.

The team produced three types of beams:

  1. one with alternating layers of cement paste sheets and thin polymer
  2. another with hexagonal grooves engraved into the cement paste sheets using a laser
  3. a third with completely separated hexagonal tablets connected by the polymer layer, similar to how aragonite lies on the biopolymer layer in nacre

Remarkable results: 17-times more crack-resistant

The experiments revealed that the beams with completely separated hexagonal tablets, which closely resemble nacre’s structure, exhibited the most significant improvements.

These beams demonstrated 19 times the ductility and 17 times the fracture toughness while retaining nearly the same strength as the solid cement paste beam.

“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,” Moini said. “We intentionally engineer defects in the brittle materials as a way to make them stronger by design.”

New era in cement construction materials

While the findings are based on lab conditions and additional research is needed to develop the techniques for use in the field, the potential implications for the construction industry are vast.

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

The researchers are working to determine whether the structures’ fracture toughness and ductility apply to other ceramic materials beyond cement paste, such as concrete.

“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.

Crack-resistant cement inspired by nature

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

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

As the 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 lies 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 engineered resilience.

The full study was published in the journal Advanced Functional Materials.

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