Tech Briefs Magazine - February 2024 - 48

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TECHNOLOGY & SOCIETY
This monthly column explores the inter-relationships between technology and society. It features people and projects aiming to
deliver a positive impact on the world facing unprecedented social and environmental challenges.
Lengthening the Lifespan of Concrete with Bacteria
An engineered BioFiber can stabilize and heal damaged concrete.
I
magine a concrete surface that, if
cracked or in need of repairs, can
" heal " itself. Well, that's exactly what
a team at Drexel University in Philadelphia
has engineered with BioFiber
- a polymer fiber encased in a bacteria-laden
hydrogel and a protective,
damage-responsive shell with the entire
assembly a little over a half-millimeter
thick.
We're making something that actually
will change once it's damaged - it
will change to heal itself. "
Manufacturing
self-healing conPES
Core-Fiber
0 100 200
According to the Drexel team, a
grid of BioFibers embedded within
a concrete structure can improve its
durability, prevent cracks from growing,
and even enable self-healing - akin
to human skin.
When a person cuts their skin, blood
comes out and the tissue starts to heal.
Of course, that's not the case with infrastructure.
So, the team based its idea on
the human concept and bioengineered
it for brittle material.
" When we have infrastructure that
face damage or cracks, it's static, " said
Associate Professor Amir Farnam. " It
doesn't repair; it's not living material.
The major idea that we had was, 'How
could we make it a living structure, so it
responds like our body?' Such as when
you get a cut and then you heal it. "
The group used a strain of Lysinibacillus
sphaericus bacteria as a bio-healing
agent for the fiber. Typically found in the
AT A GLANCE
INNOVATORS: Associate Professor Amir
Farnam and Caroline Schauer, Margaret C.
Burns Chair in Engineering, Drexel
University
INNOVATION: A BioFiber that can
stabilize and heal damaged concrete.
IMPACT: BioFiber will slow the need for
concrete production, a process that
accounts for about 8 percent of all global
greenhouse gas emissions.
48
Drexel researchers are developing a structural fiber system
that could one day enable damaged concrete structures to
repair themselves. (Image: Drexel.edu)
soil, it has the ability to drive a biological
process called microbial-induced calcium
carbonate precipitation to create a
stone-like material that can stabilize and
harden. When induced into forming an
endospore, the bacteria can survive the
harsh conditions inside concrete, lying
dormant until ready for use.
Placed in a grid throughout the concrete
as it is poured, the BioFiber acts
as a reinforcing support agent. But its
true talents are revealed only when a
crack penetrates the concrete, enough
to pierce the fiber's outer polymer shell.
As water makes its way into the crack, it
causes the hydrogel to expand and push
its way out of the shell and up toward the
surface of the crack. While this is happening,
the bacteria are activated from their
endospore form in the presence of carbon
and a nutrient source in the concrete.
Reacting with the calcium in the concrete,
the bacteria produce calcium carbonate
which acts as a cementing material to fill
the crack all the way to the surface.
The healing time ultimately depends
on the size of the crack and activity of
the bacteria, but early indications suggest
the bacteria could do its job in as
little as one to two days.
" It's the same thing [as skin healing], "
said Caroline Schauer, the Margaret C.
Burns Chair in Engineering. " When
you crack the cement, water gets in and
releases what's in there to then heal itself.
We're making something dynamic.
www.techbriefs.com
crete is much greener than you might
think; it's an incredible way to reduce
greenhouse gas emissions, as the ingredient-production
process - burning
minerals at upward of 2,000 °F
- accounts for about 8 percent of
all global greenhouse gas emissions.
Concocting concrete that can survive
longer would be a game changer.
Schauer added that the team's next
steps are two-fold: The group is considering
manufacturing as the next step but
also looking at what would be the environment
that these fibers are going to
experience.
" We developed these fibers. The next
steps are to scale up this fiber-manufacturing
process. And by scaling up, it's
finding out how it's going to work in a
real field application. So, we make concrete,
we pour some pavements, and
then we wait for few years to see those
results, " said Farnam.
He added that in real-world applications
the concrete very well could - and most
likely will - be subjected to the elements:
salt, snow, vehicles, and other variables.
However, he's hopeful the technology
could be implemented sooner than later.
One potential application is to put the
biopolymers down on the Philadelphia
Airport runway. However, that is awaiting
FAA permission.
" Based on my previous experience,
about seven to 10 years of research and
a scale of work needs to be done for new
technologies, " Farnam said. " This is seven
to 10 years from when you're starting
from scratch. We started the idea four
years ago, so, hopefully, three or four
more years. "
Andrew Corselli is Digital Content
Editor at SAE Media Group. For more
information, visit www.drexel.edu.
Tech Briefs, February 2024

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Tech Briefs Magazine - February 2024

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