Drexel Engineers Develop Nature-Inspired Concrete Reinforcement

Drexel University researchers have developed a new approach to reinforce concrete that takes inspiration from nature, specifically the hollow structures found in plant stems. The research, recently published in the Journal of Building Engineering, demonstrates significant improvements in concrete's strength, toughness and ductility compared to traditional reinforcement methods.

Traditional concrete reinforcement relies on solid steel bars (rebar) placed within the concrete to provide tensile strength. The team, led by Amir Farnam, PhD, associate professor of civil, architectural and environmental engineering, and post-doctoral researcher Parsa Namakiaraghi, PhD, instead used 3D-printed hollow polymer tubes arranged in patterns that mirror natural structures.

"Over millions of years of evolution, living organisms have developed specific architectural elements with unique geometries, such as hollow structures in plants, to enhance the mechanical properties of their structures,” explains Namakiaraghi. "Plant stems need to be both strong and flexible to survive the bending forces induced by natural elements such as wind, and they achieve this through hollow, tubular structures which also act as vessels for transporting water and nutrients. We've shown that we can apply similar principles to improve construction materials."

The team developed what they call Engineered Polymeric Reinforced Cementitious composite (EPRC), using sophisticated computer modeling to predict performance before validating their designs through mechanical testing. They created the reinforcement structures using 3D printing technology, which allowed them to precisely control the geometry and arrangement of the hollow tubes.

The hollow design proved superior to solid reinforcement in multiple ways. Beyond the structural advantages of the tubular shape, the increased surface area of the hollow tubes created stronger bonding with the surrounding concrete. This enhanced the interface properties, combined with the tubes' ability to better distribute forces, helped prevent the formation of cracks and improved overall durability. Their results showed remarkable improvements: concrete reinforced with hollow tubes demonstrated a 34% increase in ductility, 93% increase in toughness, and 55% increase in strength compared to identical samples reinforced with solid bars of the same material.

"We were particularly impressed by the improvement in toughness - the ability to absorb energy without rupture," says Farnam. "Traditional reinforced concrete can be quite brittle, but our bio-inspired design allows for more controlled deformation under stress, which is crucial for structural safety."

The work was supported by the PA Manufacturing Innovation Program, highlighting Pennsylvania's commitment to advancing construction technology through additive manufacturing. The use of 3D printing not only enabled the research but also points to potential future applications in construction.

Looking ahead, the team plans to explore scaling up the technology for practical construction applications. They're also investigating different materials and geometries that could further improve performance. The research has implications beyond buildings - the principles could be applied to infrastructure like bridges and roads, where improved durability and crack resistance are especially valuable.

"This research demonstrates how we can create better performing materials by learning from nature's time-tested solutions," adds Farnam. "As we continue to develop this technology, we're excited about its potential to make our built environment stronger, safer, and more sustainable."