Concrete, like other key parts of infrastructure, are being reimagined through new technologies. The same thing was done thousands of years ago, for example when Roman architects put lime into their concrete to help the material adjust as it set into place. 

In today's globalized economy the production and delivery of concrete surpasses $56b a year in revenue in the United States alone. 

It is in this context that the Pentagon's Defense Advanced Research Projects Agency (DARPA) has initiated a project to develop self-healing construction materials. 

The Bio-inspired Restoration of Aged Concrete Edifices (BRACE) program aims to imbue construction materials such as concrete with the self-repair capabilities of living organisms, thereby extending the serviceability of defense structures such as airfields and missile silos.

The Pentagon has chosen the Lawrence Livermore National Laboratory, the University of Colorado at Boulder, and the Battelle Memorial Institute to participate in the program.

The most commonly used material in the built environment worldwide is concrete. It can easily be produced from materials found in most places and is sturdy and long-lasting. It can be molded into any desired shape due to its composition. 

Much of the deteriorating concrete infrastructure in the United States is crumbling from the inside out. Steel-reinforced concrete has additional strength but deteriorates internally first due to the rebar rust. Determining whether intervention is necessary is difficult because the problem exists inside a concrete structure and cannot be seen externally. 

By the time one can see surface cracks, a significant amount of damage has already been done, and the structural integrity may be at risk. 

Adding a self-repair capability to existing concrete, the BRACE program research aims to increase the serviceability of buildings and airport pavements. 

Concrete is challenging to repair despite its wide usage and advantageous characteristics. Its replacement is often impractical or impossible because of its durability, which makes penetrating any healing agents difficult. 

To fix these cracks early and prevent their propagation, Battelle is concentrating on developing technologies that harness biology to provide concrete long-lasting, self-healing capabilities. 

Researchers will utilize an approach that imitates the vascular network that biology generates in nature to build fibers with engineered bacteria that, in turn, produce solid structural materials like spider silk or cellulose within the concrete construction. The minuscule bacteria will branch into the cracks and repair the mineral structure that binds concrete together, preventing further cracking. Additionally, it can be used to diagnose why there's deterioration in the concrete.

DARPA, in a press release, said, "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 spend acres of land similar in scale to concrete buildings." 

One of Battelle's strengths is the interdisciplinary expertise needed to carry out this project. Individuals from various Battelle teams will collaborate in the scientific disciplines of molecular biology, microbiology, material science, and civil engineering. 

The project's lead investigators are biologists Kate Kucharzyk from the CBRNE business line and Fadime Kara Murdoch and materials scientist Heather Luckarift from the Advanced Mission Solutions business line. Fadime Kara Murdoch and Chemical Engineer Rachel Krebs are the technical area leads for developing the biological solutions and incorporating the materials techniques, respectively.

Battelle is working with several partners on this project, including the South Dakota School of Mines and Technology, which brings knowledge of the intersection of civil engineering and biology, and the Massachusetts Institute of Technology and Boston University, which are bringing a method for building strong structures by packing fibers with gravel and concrete.

Luckarift said, " In the civil engineering world, biology is usually seen as a bad thing as it causes mold, corrosion, and other problems." She added, "I'm excited to demonstrate that biology can be applied as the solution to critical infrastructure challenges too."