Cement-based material inspired by the human bone

Inspired by the architecture of the human bone’s outer layer, this innovative material resists cracking and avoids sudden failure, a common issue in brittle construction materials.

In a 10th September article in Advanced Materials, the research team, led by Reza Moini, Assistant Professor of Civil and Environmental Engineering, and Shashank Gupta, a third-year PhD candidate, demonstrated that incorporating a tube-like structure within cement paste significantly increases its resistance to cracking. This design allows the material to deform more effectively under stress without catastrophic failure.

Gupta explained the challenges with conventional materials: “One of the challenges in engineering brittle construction materials is that they fail in an abrupt, catastrophic fashion.” He noted that while strength helps these materials bear loads, toughness is key to preventing cracks and controlling damage spread. The new technique addresses these challenges by making the material tougher without compromising its strength.

Moini highlighted that the material's enhanced performance comes from its carefully engineered internal structure: “We use theoretical principles of fracture mechanics and statistical mechanics to improve materials’ fundamental properties ‘by design’.”

The team drew inspiration from human cortical bone, the tough outer shell of the femur. This bone features elliptical tubular structures called osteons, which deflect cracks and prevent sudden failure. This natural design guided the creation of cylindrical and elliptical tubes within the cement paste, which interact with propagating cracks to enhance durability.

“Typically, one might expect that adding hollow tubes to a material would weaken it,” said Moini. “But we discovered that by carefully designing the tube’s geometry, size, and orientation, we can promote crack-tube interaction, strengthening one property without diminishing another.”

The researchers found that the interaction between cracks and the tubes initiates a unique stepwise toughening process. As the crack encounters a tube, it is delayed and redirected, which dissipates energy at each interaction. This controlled crack extension prevents sudden failure, allowing the material to withstand progressive damage and become significantly tougher.

“What’s remarkable about this stepwise mechanism is that it controls crack growth, preventing sudden failure,” Gupta explained. “The material breaks gradually, absorbing more damage and making it tougher.”

Unlike traditional methods that improve cement-based materials by adding fibres or plastics, the Princeton approach focuses on geometric design. By modifying the internal structure of the material, the researchers enhanced its toughness without the need for additional materials.

In addition to improving toughness, the team introduced a new method for quantifying the degree of disorder in the material’s architecture. Using statistical mechanics, they developed parameters to measure the degree of disorder, creating a numerical framework that moves beyond simple classifications of ordered or random structures.

Moini noted: “This framework provides a more accurate way to describe and design materials with a tailored degree of disorder. With advanced fabrication techniques such as additive manufacturing, we can scale up these tubular designs for civil infrastructure applications.”

The researchers have also recently developed techniques using robotics and additive manufacturing to create precise architectural designs in cement-based materials. By applying these techniques to different material combinations, they hope to explore further possibilities in construction applications.

“We’re just beginning to explore what’s possible,” said Gupta. “There are many variables to investigate, such as how the size, shape, and orientation of the tubes affect the material’s performance. These principles could be applied to other brittle materials to create more damage-resistant structures.”