Imagine a situation where a concrete runway, worn out or bombed by an enemy, possesses the astonishing ability to automatically repair itself, filling cracks and potholes, thereby allowing planes to take off without delays. This could become a reality sooner than you think.
The United States Defense Advanced Research Projects Agency (DARPA) has initiated the development of a unique type of concrete for military purposes, possessing the ability of self-healing through the "Biologically-Inspired Repair of Cementitious Structures" (BRACE) program. The goal of this program is to combine biological processes and concrete to create a "self-healing" material. The development concept involves repairing cracks within aged concrete from the inside before they reach the surface, thus extending the service life of crucial military structures such as runways and airfield pavements.
BRACE will explore various biological approaches based on the activities of fungi and bacteria, as well as bioengineering approaches utilizing enzymes and ceramic-like materials. The focus is specifically on developing technology capable of repairing and strengthening aged concrete within existing concrete structures, reducing the need for costly repairs and minimizing carbon emissions associated with the reconstruction and repair of concrete structures. While the use of self-healing concrete in combat zones to fortify military infrastructure is still in the research stage, the program will concentrate on both permanent structures like missile silos and naval docks, as well as rapid solutions for temporary airfields used by expeditionary forces.
By implementing a "vascular system" similar to that found in humans and other living organisms, particularly extensive networks of filamentous fungi, into the cracks and voids of aged concrete, the structure will have the ability to initiate a healing process similar to wound-healing in living organisms and continue to exist within the material, continuously repairing additional cracks that occur over time. Currently, developments based on the activities of microorganisms are among the most likely potential solutions, as they can adapt to various environments, including alkaline environments similar to concrete. Additionally, their small size can provide access to small openings in aged concrete. Logistics for infrastructure repairs, especially in extreme conditions, are also an important consideration in the program's development.
Photo: Delft University
The development of self-healing concrete technology will be carried out by several contractors over a period of 4.5 years, including Lawrence Livermore National Laboratory, the University of Colorado, and the Battelle Memorial Institute. Safety in development is a priority, and the research will be regularly reviewed by independent laboratories and regulatory bodies to ensure it does not pose threats to human health or the structural integrity of buildings. DARPA also emphasises the importance of collaboration with experts in ethical, legal, and social issues, as well as compliance with EPA requirements and standards during field testing of BRACE outside the laboratory.