Human-bone-inspired cement is 5 times tougher, damage-resistant than concrete

Researchers at the University of Princeton have developed a cement paste that is 5.6 times stronger than cement, mortar, and other conventional cement-based construction materials.

The paste features a tubular architecture inspired by the structure of human cortical bone, which forms the outer layer of the femur (thigh bone).

“Cement paste deployed with a tube-like architecture can significantly increase resistance to crack propagation and improve the ability to deform without sudden failure,” according to the researchers.

This bio-inspired cement paste also has the potential to replace plastic and fiber-reinforced cement-based materials .

The need for tougher building materials

Cement-based brittle materials used for constructing buildings must have high levels of strength and toughness. The former is associated with the ability of a structure to bear loads, and the latter decides whether it can effectively deal with cracks and damages.

A building made with material with poor toughness can collapse suddenly, causing severe damage to property and human lives.

“One of the challenges in engineering brittle construction materials is that they fail in an abrupt, catastrophic fashion, Shashank Gupta, lead researcher and a PhD candidate at Princeton, said.

This is why, it is crucial to develop construction materials that exhibit high resistance to cracking. In the event of damage, such materials should also be able to safely distribute the impact throughout the structure, rather than leading to a sudden collapse.

The science behind crack-resistant cement paste

To decode the science behind crack-resistant cement , the researchers looked for materials that naturally possessed high strength and toughness.

Soon they come across the human cortical bone, which resists fractures and provides the femur with the strength needed to support the body’s load.

“Cortical bone consists of elliptical tubular components known as osteons, embedded weakly in an organic matrix. This unique architecture deflects cracks around osteons. This prevents abrupt failure and increases overall resistance to crack propagation,” Gupta explained.

Inspired by the tubular structure of cortical bone, the researchers developed a cement paste featuring cylindrical and elliptical tubes. These tubular structures improved the crack-resistant properties of the cement, similar to how osteons strengthen the femur.

For instance, whenever a crack appears in a structure made with cement paste, it is trapped by the tubes, delaying its spread to other sections. The process of limiting the crack absorbs energy.

This is the same energy that would have otherwise made the crack grow faster. The dissipation of the energy gives the cement more time to resist damage, preventing the sudden collapse of the structure.

“What makes this stepwise mechanism unique is that each crack extension is controlled, preventing sudden, catastrophic failure. Instead of breaking all at once, the material withstands progressive damage, making it much tougher,” Gupta said.

Reinforcing cement with geometry

Generally, cement is reinforced with plastic, fiber, and other materials to increase its toughness. However, instead of adding something extra to cement, the current approach focuses on harnessing the power of tubes and geometry.

“One expects the material to become less resistant to cracking when hollow tubes are incorporated,” Reza Moini, senior researcher and a professor of civil and environmental engineering at Princeton said.

“We learned that by taking advantage of the tube geometry, size, shape, and orientation, we can promote crack-tube interaction to enhance one property without sacrificing another,” he added.

Moreover, Moini and Gupta have developed a framework to determine the degree of disorder in the cement paste. The degree of disorder refers to how irregular or unpredictable the structure or arrangement of a material is.

The framework could be useful in making the cement paste a practical and scalable solution to traditional cement-based materials.

“We’ve only begun to explore the possibilities. These principles could be applied to other brittle materials to engineer more damage-resistant structures,” Gupta said.

The study is published in the journal Advanced Materials .