What do the Hoover Dam, the Sydney Opera House, the Great Wall of China and the Pantheon have in common? They’re all examples of incredible, ambitious concrete construction.
But our most widely used building material also has an incredible carbon footprint, with its energy intensive production accounting for 8% of global emissions. This has led engineering minds to turn instead to other building materials such as flax and different blends for greener composite concretes.
Now, engineers from the University of Pittsburgh (Pitt) aim to take it to a futuristic level with their lightweight, multifunctional, highly adaptable smart infrastructure product that can be tailored to different builds and even generates its own electrical charge.
“Modern society has been using concrete in construction for hundreds of years, following its original creation by the ancient Romans,” said the study’s corresponding author Amir Alavi, assistant professor of civil and environmental engineering at Pitt. “Massive use of concrete in our infrastructure projects implies the need for developing a new generation of concrete materials that are more economical and environmentally sustainable yet offer advanced functionalities. We believe that we can achieve all of these goals by introducing a metamaterial paradigm into the development of construction materials.”
The metamaterial is made up of reinforced auxetic polymer lattices within a conductive cement matrix. The conductive cement, enhanced with graphite powder, forms the electrode, and a mechanical trigger can generate contact-electrification between the layers. It can't produce enough power to send to the grid, but it can potentially be used to monitor damage inside the concrete structures – for example, in case of an earthquake.
Physically, the metamaterial itself can be fine-tuned to fit the needs of the build, switching up its flexibility, shape and brittleness, and in tests could compress up to 15% while maintaining its structural integrity.
“This project presents the first composite metamaterial concrete with super compressibility and energy-harvesting capability,” said Alavi. “Such lightweight and mechanically tunable concrete systems can open a door to the use of concrete in various applications such as shock absorbing engineered materials at airports to help slow runaway planes or seismic base isolation systems.”
The team, which included engineers from Johns Hopkins University, New Mexico State University, the Georgia Institute of Technology, Beijing Institute of Nanoenergy and Nanosystems, and Pitt’s Swanson School of Engineering, believes the multifunctional concrete material can become a widely used component in infrastructure, as it’s “scalable, cost-effective, and can self-sustain its operations through green harvesting energy."
And down the road (quite literally), this smart engineering product could even power chips embedded within highways to assist self-driving cars.
However, in the immediate future the study reports the need for large-scale testing and further research into how to insulate the energy-harvesting nanogenerator-integrated material from environmental stressors such as humidity, wet weather and temperature variations.
The research was published in the journal Advanced Materials.
Source: University of Pittsburgh
