Concrete is, by far, one of the most essential building materials ever invented. However, it is liable to crack and splinter over time, which is aesthetically unpleasing and compromises its otherwise great strength.
But recent developments in material science could lead to concrete that can heal itself. Such a material would be instrumental in the construction sector, but it has also found another interesting potential client: the US armed forces. One primary area in which such a material would be beneficial is runways.
Surfaces can continue to be used for aircraft
These structures suffer from wear and tear over time but are also susceptible to damage from air raids. If the runways can be made from this material, they can repair themselves to ensure the surfaces can continue to be used for aircraft.
To this end, the Pentagon's research office, the Defense Advanced Research Projects Agency (DARPA), aims to develop a specific type of concrete for military installations. Called BRACE, or bio-inspired restoration of old concrete edifices, the programme seeks to combine the principles of biology and concrete to restore ageing concrete structures.
BRACE utilises biological organisms to construct a vascular system within the concrete that can repair cracks internally, preventing them from reaching the surface of a structure. This allows concrete to undergo a healing process similar to living organisms. Concrete deterioration can be diagnosed using this method as well.
“The central hypothesis of BRACE is that concrete can be infused with self-repair capabilities typically found in living organisms, drawing inspiration from vascular systems found in humans and vast networks of filamentous fungi that can span acres of land similar in scale to concrete buildings,” DARPA said in a recent press release.
“Such systems could provide a network of transportation for healing within the depths of the material to repair cracks before they reach the surface and cause failure.”
BRACE will last 4.5 years as it is developed by several contractors, including the University of Colorado Boulder, Lawrence Livermore National Laboratory, and Battelle Memorial Institute.
Biological organisms and processes
The DARPA announcement stressed that "safety is paramount, and all research will be subject to regular review by both an independent laboratory and regulatory agencies to ensure BRACE technologies do not pose a threat to human or structural health", perhaps because BRACE uses biological organisms and processes.
When testing BRACE outside of the lab, researchers will have to adhere to EPA regulations and consult with experts on the "ethical, legal, and societal implications" of the technology.
'Bioconcrete', or self-healing concrete, is not new, but a military application may have significant advantages. Old and worn buildings, from barracks to supply depots, have become a severe issue at US military locations.
Self-repairing structures would reduce costs. A self-repairing runway would reduce maintenance costs during the conflict, but it would also make it harder for an attacker to plan their attack because they wouldn't know when the airfield would resume operations.