When you get a cut, your skin heals itself. A concrete bridge or building that suffers surface damage can’t do the same. But a new Defense Advanced Research Projects Agency (DARPA) effort to give concrete “self-healing capabilities” aims to change this.

The initiative, Bio-inspired Restoration of Aged Concrete Edifices (BRACE), will create “vascular structures” within concrete and inject liquid “healing substances” that will flow through the structures to make any cracked and crumbling concrete whole. Coupled with this, the project will develop new systems for maintaining these new systems and predicting how long they will last.

It’s a lot like how our bodies repair tissue damage: Blood vessels pump blood to a wound, and within the blood are cells containing oxygen, protein, and other materials that support the growth of new tissue. DARPA acknowledged the similarity in a press release in which it called BRACE a “bio-inspired” approach for restoring old and deteriorating infrastructure.

“Inspired by the vascular systems that support continuous repair in multicellular organisms and ecosystems, BRACE will develop approaches to integrate a healing ‘vasculature’ for prolonged damage repair and prevention,” reads the release.

BRACE will run for 4.5 years and will seek partners this year, with a virtual Proposers Day for potential proposers taking place on April 13.

New Approach to a Historic Problem

The U.S. military has a lot of concrete in need of healing. The buildings and infrastructure of the Army, Air Force, Navy, and Marines have endemic maintenance issues and face tens of billions of dollars’ worth of repair backlogs. Living conditions in base housing has been deteriorating for years, while structural damage to shipyards, aircraft hangars, and runways is so extensive that it’s causing Air Force and Navy missions to run behind.

Funding cuts to military construction and housing over the last decade may be part of the problem. Age is another, as many of these facilities date back to World War II or earlier. Time and the elements are taking their toll.

To tear down all these old structures and build new ones would be a colossal–and colossally expensive–undertaking. BRACE’s engineers hope that they can save time and money by making the existing structures last longer.

“Today’s DoD has inherited, and relies upon, a significant amount of concrete infrastructure from the 1940s and 1950s that cannot be easily replaced,” said Dr. Matthew J. Pava, BRACE program manager, in the DARPA press release. “The BRACE program, if successful, will prevent new damage, shorten repair time, and reduce maintenance costs, allowing for extended infrastructure service life.”

Biology-based Solutions

It may surprise some readers that biology might be the inspiration for a new way to fix concrete, but it shouldn’t. Human engineers and designers have been solving problems by emulating systems and forms found in the natural world for years.

The practice is called “biomimicry.” And it’s how Velcro came to be: Inventor George de Mestral got his idea for the world-famous adhesive after removing burrs from his dog’s fur one night and examining them up close to see why they were so sticky.

Biomimicry has also solved problems in clean energy and sustainability. In 2004, British and U.S. researchers noticed that whale fins have small bumps that reduce drag and increase the big mammals’ swim speed. The researchers copied this design onto wind turbine blades and greatly boosted wind power production.

And in 2012, a Zimbabwean architect designed a building, the Eastgate Centre, which uses 90% less energy for heating and cooling than similarly sized buildings. How did he do it? Studying the cooling tunnels of termite mounds.

Biomimicry has fans in DARPA. The agency has applied it to a few defense applications besides self-healing concrete:

  • In 2019, DARPA opened research into studying insects’ brains for clues to developing better artificial-intelligence software frameworks.
  • Plants sense and respond to stimuli in the environment. DARPA’s Advanced Plant Technologies is exploring engineering plants’ genomes so that they’ll detect and react to radiation, chemical warfare agents, and pathogens.
  • Swarms of small drones could be more effective than one or two big ones. To assess how they’d all fly together, DARPA’s OFFensive Swarm-Enabled Tactics (OFFSET) program is studying the swarm patterns of birds and insects.

Restoring the U.S. military’s sprawling infrastructure is, in some ways, an efficiency problem: how to do more with the structures we already have. And there may be no better teacher on efficiency than the natural world. Pushing systems to act efficiently–i.e., evolution–is what nature has been doing for billions of years.

Granted, concrete is not a natural substance. But DARPA is clearly banking that what nature is able to do with living bodies, we may be able to do with buildings.


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Rick Docksai is a Department of Defense writer-editor who covers defense, public policy, and science and technology news. He earned a Master's Degree in Journalism from the University of Maryland in 2007.