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UTILIZING LIMESTONE-PRODUCING BACTERIA IN CONCRETE TO PAVE
THE WAY FOR SELF-HEALING INFRASTRUCTURE
Mark Kosky, [email protected], Mena Lora 1:00, Patrick Schorr, [email protected], Mena Lora 1:00
Abstract—The concept of self-healing materials has always
seemed to be more theoretical than realistic. However, recent
research breakthroughs have led to the fruition of such
materials. Limestone-producing bacteria technology aims to
replace the need for manual repair of our constructed
environment. This technology has been incorporated into
concrete manufacturing, producing a “self-healing” concrete,
which could revamp the construction of sidewalks, buildings,
bridges, dams, roads, and many other components of
infrastructure. Self-healing concrete consists of tiny capsules
of select bacteria mixed in with liquid concrete, which create
limestone to fill cracks in the concrete when brought into
contact with water. It has the potential to solve most problems
facing cities regarding the maintenance of their roads as well
as many other areas of urban infrastructure. It also solves
these problems in sustainable ways because the bacteria
spores pose little threat to the environment yet offer vast longterm benefits to the upkeep of infrastructure.
This technology is important to everyone because it
would eliminate many costs associated with repairing and
rebuilding crumbling infrastructure; people and businesses
rely on structurally sound buildings, roads, and facilities for
everyday operations. Experimental studies, case studies, and a
variety of articles provide ample information regarding selfhealing concrete and its applications. These studies support
the notion that this technology can solve a wide range of
problems from the obvious damaged roads and buildings to the
more subtle costs to motorists and taxpayers. Self-healing
concrete is a significant innovation in engineering and can
help solve a variety of problems and costs associated with
damage to structures, saving time, money, and lives.
Key Words— Bacteria, concrete, construction, limestone,
permeability, preventative, self-healing
A LOOK INTO SELF-HEALING CONCRETE
When most people walk into a building, whether it be a
school or workplace, they usually don’t take the time to think
about the actual structure in which they are standing. Over
time, our built environment, from roads to bridges,
University of Pittsburgh Swanson School of Engineering 1
2/10/2017
deteriorates. There is a need for a more permanent and
sustainable solution.
Limestone-producing bacteria technology, although a
more recent technology, proves to be a promising innovation
in civil engineering. First, explaining the problem of
deteriorating urban infrastructure and why it is significant to
society as a whole is key in providing the context for this
technology. Then, a proposed solution through self-healing
concrete will be offered. Next, this technology’s effectiveness
will be evaluated in repairing not just roads, but many other
components of infrastructure such as buildings and bridges.
Finally, examining the process behind this technology and then
discussing its societal implications exemplifies the versatile
problem solving power of limestone-producing bacteria
technology.
HITTING THE POTHOLE: AMERICA’S
CRUMBLING INFRASTRUCTURE
An overall grand challenge in civil engineering is to
improve America’s crumbling infrastructure. In 2013, the
American Society of Civil Engineer’s (ASCE) compiled a
comprehensive report card detailing the quality of America’s
infrastructure and it reveals startling results. The overall grade
point average was a D+ [1]. More specifically, road quality
was given a D letter grade, stemming from inefficient,
financially straining, and unsafe roads.
In order to fully explain the significance of the problem
of poor road conditions on society and even individual U.S.
motorists, the conditions and capacity of the nation’s roads
must be examined. Regarding the inefficiency aspect, “42% of
America’s major urban highways are congested… Americans
still wasted 1.9 billion gallons of gasoline and an average of 34
hours in 2010 due to congestion, costing the U.S. economy
$101 billion in wasted fuel” [1]. Construction to maintain poor
quality roads results in traffic congestion and vehicle idling,
halting business transports and economic growth. These
effects add to the financial challenges associated with these
roads.
Regarding general road quality, “32% of America’s
major roads are in poor or mediocre condition, costing U.S.
Mark Kosky
Patrick Schorr
motorists who are traveling on deficient pavement $67 billion
a year, or $324 per motorist, in additional repairs and operating
costs” [1]. Subpar roads result in financial problems that affect
individual households and the overall economy. For the
economy as a whole, “after 25 years the cost per lane mile for
reconstruction can be more than three times the cost of
preservation treatments over the same time period” [1]. While
repeated treatment of crumbling roads is a temporary solution,
it still contributes to traffic congestion and its costly effects.
Safety is the most important aspect of any transportation
system and poor-quality roads threaten its implementation.
The ASCE report’s statistics suggest that “roadway conditions
are a significant factor in approximately one-third of all U.S.
traffic fatalities” [1]. The loss of life is the ultimate
consequence of subpar infrastructure and public safety is the
number one priority in civil engineering. In connection with
the financial challenges involved, “[vehicle] crashes cost the
U.S. economy $230 billion each year” [1]. All of the associated
costs and effects with roads in poor conditions point towards a
need for more innovative solutions.
Due to these adverse effects, this problem is significant
to all U.S. motorists and the general public. A new, sustainable
technology is required to mitigate the costly effects of
mediocre roads, from traffic congestion and idling, to the loss
of life. Defining this major infrastructure problem provides
context for our investigation of self-healing concrete as a
versatile problem solver and its foundations in the next section.
FIGURE 1 [2]
Rigid and Flexible Pavement designs and their subsequent
pavement structures.
Rigid pavements have a design life of around 30+ years,
an equivalent unit cost of approximately $6 to $8 per square
foot, low maintenance costs, high compressive strength, and a
low ability to expand and contract with temperature changes.
Flexible pavements have a somewhat shorter design life of
around 10 to 20 years, an equivalent unit cost of $2 to $3 per
square foot, which is influenced by the price of oil due to its
bitumen dependence, high maintenance costs, high flexural
strength, and a higher ability to expand with temperature
changes [2]. Understanding pavement designs allows for the
explanation of why large cracks form and deform roads and
structures.
Although these two designs have been the norm for a
long period of time, they are still susceptible to certain types
of distresses: Fatigue (or Alligator) cracking and Longitudinal
cracking. According to the Pavement Design and Analysis
class at Pitt, fatigue cracking occurs due to repeated load
applications, the most obvious case being a car’s tires. Fatigue
cracking initiates at the bottom level of the base layer of a
pavement structure and capacitates the overall structural
capacity. [3] As evident in Figure 2 below, the rate of
development of the cracks continues exponentially, resulting
in what looks like the scales on an alligator. Longitudinal
cracking results in large elongated cracks parallel to the
laydown direction from repeated load applications.
Longitudinal cracks allow moisture to infiltrate the inner layers
of the pavement structure. Due to the spring-thaw cycles and
freezing temperatures, frost heave permeates the subbase and
turns into water, expanding the pavement structure and
resulting
in
even
larger
cracks.
BRIEF HISTORY AND FOUNDATIONS
In order to fully explain the impact of self-healing
concrete, a closer look into traditional pavement design and the
types of cracks that result in poor roads, sidewalks and other
concrete structures provides context for this technology’s
implementation. It should be noted that although potholes
occur primarily in asphalt pavements, they still can occur in
concrete pavements and structures.
Traditional pavement design entails two common types:
rigid and flexible. Rigid pavements distribute wheel loads over
a wide area of subgrade and are comprised of cement concrete
and may be reinforced with steel [2]. In contrast, flexible
pavements transfer wheel loads to lower levels of the
pavement structure and consist of bituminous, or black viscous
mixtures of hydrocarbons, material. Figure 1 shows these two
types of traditional pavement designs and how they differ.
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microcapsules are mixed with the concrete. The Bacillus
pseudofirmus and the calcium compound are the active
components of limestone-producing bacteria technology.
FIGURE 3 [4]
Microcapsules of bacteria and a calcium nutrient. Tiny
cracks and the presence of water activate the dormant
bacteria.
The active components of limestone-producing bacteria
technology in concrete work together to produce limestone, the
main ingredient in concrete, that fill microcracks of any length
and less than 0.8 mm in width in concrete, according to the
European Patent Office [5]. The calcium compound serves as
the fuel or food for Bacillus pseudofirmus, the bacteria that
actually produces the limestone. According to Materiaux and
Techniques, an academic materials science journal, there are
two conditions that trigger activity of Bacillus pseudofirmus.
These are the presence of oxygen and water [6]. A study
performed by German biologist, U. Schottler, characterized
various Bacillus bacterium and explained this anaerobic
phenomenon. Bacillus pseudofirmus is a facultative anaerobe.
This means that it requires oxygen to function, otherwise, it
remains dormant, for up to 200 years before it is considered
functionally invalid [7]. Therefore, when the bacteria is
encased in concrete, it is dormant due to the absence of oxygen.
However, when a microcrack forms, oxygen reaches the
dormant bacteria which then becomes activated.
When a microcrack forms, the bacteria are exposed to
oxygen, which awakens the bacteria from its dormant state.
When water enters concrete through the microcrack, it
activates the Bacillus pseudofirmus as it comes into contact
with the microcapsules. The activated Bacillus pseudofirmus
then consumes the calcium compound present and produces
calcium carbonate, also known as limestone. This limestone
fills the microcrack through which the water entered the
concrete completely, thus repairing and strengthening the
concrete. The time it takes for the microcrack to be completely
filled depends on the depth and width of the microcrack,
however, most microcracks are filled over a time period of
FIGURE 2 [3]
Fatigue cracking and its subsequent effect on flexible
pavement.
Current paving techniques have been sufficient to meet
today’s needs, but they can be combined with the utilization of
limestone-producing bacteria technology to revolutionize
construction in general. Hendrik Marius Jonkers, a Dutch
microbiologist at Technische Universiteit Delft, patented this
limestone-producing bacteria technology. Self-healing
concrete will not only provide a solution in mitigating fatigue
and longitudinal cracking in sidewalks, roads, and even
buildings, but also has societal and environmental benefits.
Further explanations of this technology will aid in the later
examinations of these impacts.
HOW IT WORKS
Futurism, an online invention catalog, describes the
process of utilizing limestone-producing bacteria technology
as adding several ingredients to a normal concrete recipe.
These ingredients are: the actual bacteria itself, typically
Bacillus pseudofirmus, and a calcium compound [4]. These
two components are mixed together to form many
microcapsules. These microcapsules are dispersed throughout
the normal concrete mixture. Figure 3 depicts how these
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about 3 weeks. It is amazing how such a simple process which
uses naturally occurring materials can have such a large
number of applications.
Limestone-producing bacteria technology can be used in
many ways. This is due to its versatility. In other words, it can
be widely applied because it is not an incredibly delicate
science. The most obvious application of this technology is in
new construction: building structures using concrete
containing the Bacillus pseudofirmus and calcium source
microcapsules.
This method of use can be applied to non self-healing concrete
structures, adding to their sustainability, however, it is more
effective in self-healing concrete structures. This is because
the pre-existing concrete also has self-healing properties
which, in coalition with the self-healing properties of the
mortar patch, creates a stronger bond between the patch and
the concrete itself. This results in a stronger patch, which
makes the patch less likely to fall out or crack itself. One
downside to the patch is that it is relatively more expensive
than a structure made of self-healing concrete. However, if a
structure is already built without self-healing concrete, this
extra cost is negligible compared to the cost of rebuilding a
damaged structure.
New Structures
Sealing Liner
Building new structures utilizing limestone-producing
bacteria technology in concrete is the maximum extent to
which this technology will be utilized in a structure because it
will be incorporated in the original structure rather than just
the repairs to the structure. This application would be
considered preventative maintenance: maintenance done to
prevent larger problems, cracks in this case, from occurring.
While self-healing concrete is more expensive than traditional
concrete, this is the ideal option because once the structure is
constructed, there is not much maintenance needed for the
concrete due to its self-healing nature. This makes self-healing
concrete more sustainable than regular concrete. Periodic
inspection is still necessary, however, to make sure that all the
microcracks are being filled and not progressing to a point
where the crack is too large to be filled by the self-healing
agent alone. In these cases, a repair application of the
limestone-producing bacteria technology would be needed to
fill the crack.
An example of a structure built entirely of self-healing
concrete is a test building constructed by Hendrik Jonkers, a
Dutch microbiologist at Delft University and the inventor of
self-healing concrete. Jonkers built the structure as a trial study
to field test his invention. Constructed in 2012, the structure is
still in pristine structural condition due to its sustainable selfhealing nature. According to Jonkers, the microcracks are
being verifiably filled without issue.
Another method of use of limestone-producing bacteria
technology in concrete is as a sealing liner. This method uses
spray self-healing concrete to seal non self-healing concrete to
protect it from chemical ingression [8]. This would be
considered preventative maintenance because it is typically
done during or shortly after construction of a structure. This
option gives a project the best of both worlds: the self-healing
abilities of self-healing concrete without the cost of an entirely
self-healing structure. Another aspect to this application is the
level of sustainability it adds to the structure to which it is
applied. It greatly adds to the lifespan of the structure, creating
a more sustainable structure. There are two applications for
this method as well, one of which does not add to the strength
of a structure and one of which that does.
An application which does not add strength to a structure
is the use of self-healing concrete as only a sealant. In this
application, the self-healing concrete would cure on top of preexisting structure. This creates two separate slabs of concrete
with very little adhesion between them. This actually has the
opposite effect on the structure. Instead of giving strength to
the structure, it adds a load to the structure: the weight of the
concrete which is not supporting itself. A more efficient option
is to join the two slabs into a single cohesive piece.
For a self-healing slab to add strength to a structure, it
must be part of the structure. This could be accomplished by
pouring the self-healing layer and the non self-healing concrete
together so that they would cure together and become one
piece. While this complicates the construction process, it
would create a stronger structure in the end. Also, this method
would demand fewer resources and therefore be more
sustainable. If the self-healing concrete were part of the loadbearing structure, then the overall structure would not need to
be as large, therefore it would need fewer materials.
APPLICATIONS AND METHODS OF USE
Mortar Patch
A method of use of limestone-producing bacteria
technology that would be considered a reparative measure is a
self-healing mortar patch for damaged pre-existing non selfhealing concrete structures. [8] This is considered a reparative
measure because it is only used when limestone-producing
bacteria technology is either not present or not capable of
filling the respective crack. This mortar patch is inserted into
the cracks and sprayed with water to activate the bacteria in the
mortar. The crack is then filled by a combination of the mortar
as well as the limestone produced by the bacteria in the mortar.
EFFECTIVENESS
Effectiveness in this case is defined as the extent to which
Bacillus pseudofirmus is able to produce calcium carbonate
(CaCO3), also known as limestone. Effectiveness is generally
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a qualitative observation. This observation is taken by
comparing several measures of how much limestone is
produced by Bacillus pseudofirmus while being influenced by
a certain factor. An example of one of these qualitative
observations is the homogeneity of the limestone filling. If the
bacteria are less effective, one will notice that the filling looks
pieced together and has even smaller cracks within it.
Examples of homogenous fillings and non-homogenous
fillings are illustrated in Figures 4 and 5.
capable of filling. Bacteria in a less effective state (Figure 5)
cannot fill a gap as wide as they would if they were in a more
effective state (Figure 4). Notice that in Figures 4 and 5, the
filling ranges from 10-20 micrometers in Figure 4 and only 26 micrometers in Figure 5. This is because Figure 4 represents
bacteria in a more effective state than the bacteria which Figure
5 represents. The previously listed differences, as well as many
more, result from a difference of effectiveness of two separate
cultures. The differences in effectiveness can be attributed to
differing factors in the environment surrounding the bacteria.
There are countless factors which have the potential to
influence the effectiveness of Bacillus pseudofirmus. These
include temperature, surrounding moisture, pressure, type of
fuel source, and many others. A report written by Jing Xu and
Wu Yao, researchers funded by the National Natural Science
Foundation of China, states that the fuel source available to
Bacillus pseudofirmus is actually the most, if not the only,
influential factor on the effectiveness of Bacillus
pseudofirmus. [9]
In the previously referenced study, collected data
supported the notion that the type of fuel source available to
Bacillus pseudofirmus was the greatest influence on the
bacteria’s effectiveness. The fuel source they are speaking of
is the calcium compound added to the concrete mixture. In this
study, they tested two sources of calcium, calcium lactate and
calcium glutamate. The researchers concluded from the data
collected in this study, that calcium glutamate, represented by
Figure 4, causes Bacillus pseudofirmus to produce limestone
more effectively than calcium lactate, represented by Figure 5.
Another measure of the effectiveness of a filling is testing
the strength of the filling. This is a reflection of the bonds
within the filling and the bonds between the filling and the preexisting concrete. More effective bacteria will create stronger
bonds, which will yield more strength against all forces. The
study listed above also tested this factor. The researchers tested
two types of strength, flexural and compressive.
Flexural strength is a material’s ability to resist
deformation from a torque force. The study conducted by Xu
and Yao yielded the results in Figure 6.
Figure 4 [9]
Homogenous fillings: The filling is pieced together with
microcracks. B. pseudofirmus exposed to calcium
glutamate.
Figure 5 [9]
Non-homogenous fillings: The filling is more broken up
and more noticeable cracks can be seen. B. pseudofirmus
exposed to calcium lactate.
Figure 6 [9]
Flexural strength of each respective material: note the
subtle difference between the bacteria and the control
(traditional concrete).
Another way to analyze the effectiveness of Bacillus
pseudofirmus is by quantifying it. One of these quantitative
measures is the width of the microcrack that the bacteria are
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Patrick Schorr
As is evident upon immediate inspection, fillings created
by Bacillus pseudofirmus exposed to calcium lactate are
actually flexurally stronger overall than fillings created by
Bacillus pseudofirmus exposed to calcium glutamate.
However, upon closer inspection, an interesting trend occurs:
the fillings created by bacteria exposed to both calcium lactate
and calcium glutamate are as strong if not stronger than
regular, non-self-healing concrete, the control, after a curing
period of 28 days. At first, fillings created by calcium
glutamate-exposed bacteria are weaker than the control,
however as time passes, they become as strong, if not slightly
stronger than, the control. A similar trend appears with the
compressive strength of the fillings.
Compressive strength is a material’s ability to resist
deformation from a compressing force. The results yielded for
compressive strength in the study by Xu and Yao are illustrated
by Figure 7.
time. Self-healing structures essentially grow stronger
overtime. This supports the notion that it is sustainable.
However, this enhanced strength won’t matter if the bacteria
can not survive the diverse temperatures throughout the year.
Temperature actually has little to no effect on Bacillus
pseudofirmus due to the environment it comes from. Bacillus
pseudofirmus is found in rocks around volcanoes. This means
that it can endure intense heat and cold. Because of this,
temperature does not have an effect on how effective Bacillus
pseudofirmus is at creating limestone. The effectiveness of
self-healing concrete is a great stride for engineering. It is even
more of an accomplishment because self-healing concrete is
incredibly sustainable.
SUSTAINABILITY
Sustainability is a characteristic that describes a process
or technology that can be carried out or produced in an
economical manner for an extended period of time without
negative consequences. Examples of such negative
consequences would be damage to the natural and built
environment, or threats to the health and safety of the populus.
Recently there has been a large push towards
incorporating sustainability into innovation in the engineering
world. This trend is caused by the realization of responsibility
that has struck the engineering world particularly hard. One
way to exercise this responsibility is to make construction of
new structures and repair of existing structures as sustainable
as possible. Self-healing concrete is the perfect way to
accomplish this goal.
The first aspect of self-healing concrete’s sustainability
to consider is what threat, if any, collecting Bacillus
pseudofirmus poses to the environment. Bacillus pseudofirmus
is a naturally occurring bacteria that is found in rocks near
volcanoes. [5] It could be cultured in a lab so that it would not
need to be repeatedly collected from nature. This supports the
notion that self-healing concrete is a sustainable technology.
Another important aspect to consider about the
sustainability of self-healing concrete is what effects there will
be if Bacillus pseudofirmus spores are to escape the concrete
and get into the air or water supply. Bacillus pseudofirmus’
only function is creating limestone in the presence of water.
[5] While it would be surrounded by water and potentially
calcium sources in the water supply, any calcium carbonate
created Bacillus pseudofirmus would not have a medium to
grow on and would therefore be washed away. Also, the
creation of calcium carbonate by Bacillus pseudofirmus is a
slow process. It takes roughly 3 weeks of constant exposure to
a calcium source for Bacillus pseudofirmus to fill a 0.2 mm
wide crack. However, eventually, some bacteria is bound to
attach to some medium and produce limestone. While not
highly frequent, this occurrence could result in precipitation of
limestone bits in our water supply. This may not cause a
problem initially, however, over a long period of time, this
could create a problem of limestone aggregate in the water
Figure 7 [9]
Compressive strength of each respective material: again,
note the subtle difference between the bacteria and the
control.
The same trend occurs for compressive strength as did for
flexural strength: Calcium lactate exposed bacteria created
fillings are initially not as strong as the control but become
stronger than the control when they have more time to cure.
Calcium glutamate exposed bacteria created fillings are always
stronger than the control. This trend creates an interesting
phenomenon: the healed microcracks of the concrete are
actually stronger than the concrete was itself. This is quite
similar to how a bone heals when broken: the bone is stronger
at the fracture point after healing than it was initially. An
important point to note however, is that this is only caused by
the presence of a calcium source.
Upon inspection of Figures 6 and 7, it is apparent that a
part of the experiment tested the strength of fillings created by
bacteria not exposed to a calcium source. These fillings were
weaker than the control entirely except for the test of flexural
strength after a curing period of 3 days. Here, the solelybacteria-created fillings are slightly stronger than the control,
but this goes away as the control strengthens more over
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supply. A different trend occurs for airborne Bacillus
pseudofirmus.
Airborne Bacillus pseudofirmus would not be a threat to
the environment because it requires prolonged contact with
water and a concentrated calcium source to create calcium
carbonate. [5] These conditions would not be met if Bacillus
pseudofirmus were inhaled or dispersed throughout the
atmosphere. Therefore, this also supports the notion that selfhealing concrete is a sustainable technology.
SOCIETAL AND ECONOMIC IMPACTS
With any engineering innovation, there are societal and
economic impacts involved. With America’s subpar
infrastructure, as discussed in the 2013 ASCE Report Card,
subpar roads, bridges, and buildings and their costly effects
prove that there is a need to address the current pavement and
construction techniques. Self-healing concrete aims to replace
the need for constant repair and maintenance of the built
environment due to fatigue, longitudinal, and other types of
cracking.
As aforementioned, potholes usually occur in asphalt
pavements, but can actually affect concrete pavements as well.
Two studies, a ClaimStat Alert from the office of the New
York City Comptroller, Scott M. Stringer, and an article from
the University of Chicago Press Journals, show that subpar
roads and sidewalks have societal and economic impacts. Selfhealing concrete can be a versatile problem solver, and
mitigate the incurred costs with subpar infrastructure; but, it
does have its drawbacks.
Figure 8 [10]
Property damage claims in NYC from potholes: separated
by year and major roadway
It is interesting to note that this breakdown shows which roads
are more susceptible to potholes and in turn, more costly. In
addition, Figure 9 shows the number of personal injury claims
from pothole incidents per year.
Economic
The first report, which discusses the costs associated with
poor roads, presented a data-driven look at New York City’s
roadways and details property damage and personal injury
claims from pothole incidents. The report began by stating that
“over 80 percent of the major roads and highways in the New
York City and Newark metropolitan areas were in poor or
mediocre condition” [10]. This just reinforces that fact that
America’s infrastructure is indeed crumbling and constantly
needs repaired. In New York, “this [poor roads] imposes
nearly $800 in annual additional maintenance costs on car
owners” [10]. These costs not only are imposed on the city
itself but on car owners, resulting in a “hidden pothole tax.”
Due to these subpar roads, the city receives countless
defective roadway claims which include property damage,
primarily to vehicles, and personal injury claims. In total, the
cost of both personal injury and property damage claims
accumulated nearly $138 million between 2010 and 2015,
approximately $27.6 million annually [10]. Figure 8 shows the
number of property damage claims per year and by major
roadway.
Figure 9 [10]
Personal injury claims in NYC from potholes: separated
by year with a total of 5,913.
Referencing the graph, there were 5,913 personal injury
claims in total. During this same time period (2010-2015),
2,681 claims were settled at a cost of $136.3 million [10].
Limestone-producing bacteria technology offers a long term
solution to mitigate the costs associated with subpar roads as
opposed to the quick, but more long term costly, fix with
patching.
Limestone-producing bacteria technology offers a more
permanent solution to the costs associated with subpar roads,
but it also has its drawbacks. The price of this self-healing
concrete depends on its application, as the limestoneproducing bacteria technology can be applied in other
materials other than concrete. But in its current form, “the
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Patrick Schorr
production cost is still twice the cost of regular concrete
manufacture (€ 80/m3)” [5], or about $84/m3. The main reason
the cost is so much higher is due to the calcium lactate nutrient
for the bacteria, but Hendrik Marius Jonkers and his team are
working on a significantly less costly sugar-based nutrient.
Although self-healing concrete offers a more permanent
solution, its high cost limits its availability for all components
of infrastructure. This supports the notion that it is
unsustainable economical wise since it is twice the cost of
regular concrete. However, this fact is negated by the fact that
self-healing concrete lasts a lot longer than traditional
concrete.
Self-healing concrete has many applications in
infrastructure, and because of this, has many societal and
economic benefits. With the costs involved in our D+ average
quality infrastructure, every country is looking for a solution
to mitigate the effects of deteriorating roads, bridges, dams,
etc. This technology is a versatile problem solver as it
addresses economic, in relation to pothole costs, and social
concerns, in regards to political performance.
SELF-HEALING IS AN INNOVATION OF
THE FUTURE
Self-healing concrete is amazing. This technology
utilizes naturally occurring bacteria found in rocks by
volcanoes to fill microcracks in concrete structures. Water
activates the dormant bacterial spores when it enters the
concrete through the cracks. The bacteria then fill said crack
by feeding off the present calcium source and producing
calcium carbonate, otherwise known as limestone. This
technology has many applications ranging from entire selfhealing structures to spray that repairs cracks in pre-existing
structures. Unaffected by temperature, this technology is also
quite effective in that after the fillings completely cure, they
are actually stronger than the concrete surrounding the filling.
Such a groundbreaking (or repairing, pun intended) innovation
is bound to have an impact on many things. Unfortunately, this
technology could potentially create an environmental issue if
bacterial spores escaped into the water supply. Otherwise, selfhealing concrete is quite sustainable. Self-healing concrete has
a positive economic impact because it reduces the costs of
repairing damaged structures or roads. This in turn creates a
positive impact for society because as money is saved, public
funding can be redirected towards other necessary projects that
would have been passed over had there not been enough
money to complete them. Self-healing concrete is an
innovation of the future that will aid in solving the problem of
our country’s failing infrastructure. The ASCE recently
released their 2017 Infrastructure Report Card in which the
United States received a score of a D+ [12]. This is the same
score the US received on their last report four years ago. In
four years, there has been no improvement in the United States
infrastructure. The integration of self-healing concrete in
construction could potentially help solve this problem.
Societal
The second report, a study conducted in San Diego on the
correlation between citizens’ pothole complaints and
incumbent electoral performance, shows the potential political
impact that self-healing concrete can have on society. Craig M.
Burnett, from Hofstra University, and Vladimir Kogan, from
Ohio State University coordinated the study. Again, while
potholes aren’t a direct cause of concrete cracking, it is still of
importance to discuss our current infrastructure quality and
how it affects our society as a whole.
The results of this study conclude that the number of
potholes and subsequent complaints negatively affect
incumbent electoral performance. San Diego is one of the most
pothole populated cities in the U.S., and this study seeks to
determine the relationship between voter’s concerns about
road quality and its effect on local elections. The study found
that “each additional pothole complaint reducing [reduced]
incumbent vote share by roughly 0.2 percentage points” [11].
Although this seems to not be a very significant percentage, it
still has an impact. The study goes onto say that “in a close
election, local road quality could prove pivotal to whether the
incumbent wins another term or loses the election” [11].
Limestone-producing bacteria technology can improve road
quality and concrete structures, resulting in fewer complaints
and overall more sustainable and better quality infrastructure.
In addition, the previously discussed article from the
European Patent Office describes some other societal benefits
from self-healing concrete. After describing Jonkers patented
technology it highlights the costly effects of maintaining
concrete structures, “because around 70% of Europe’s
infrastructure is comprised of concrete, maintenance is an
extremely costly affair… the annual maintenance cost for
bridges, tunnels and earth-retaining walls in the EU member
countries at up to € 6 billion” [5]. Again, this technology can
help lower all around building and maintenance costs,
providing longer-lasting and less costly infrastructure.
Additionally, in regards to sustainability, “anywhere from 7 to
12% of the world’s annual CO2 emissions are related to the
production of the building material [traditional concrete]” [5].
Self-healing concrete is manufactured through a completely
different process and has fewer CO2 emission rates compared
to traditional concrete, making it a more sustainable choice.
SOURCES
[1] “2013 Report Card for America’s Infrastructure; Roads:
Investment and Funding” American Society of Civil
Engineers.
Accessed
1.11.2017
http://www.infrastructurereportcard.org/a/#p/roads/investmen
t-and-funding
[2] “Rigid versus Flexible Pavement Design” R. O. Anderson.
Accessed 3.1.2017
http://www.roanderson.com/2011/12/22/rigid-versus-flexiblepavement-design/
8
Mark Kosky
Patrick Schorr
[3] “Pavement Performance” Lecture. University of Pittsburgh
Pavement Design Course. 2016. Accessed 3.1.2017
[4] “Say ‘Goodbye’ to Cracks, Self-Healing Concrete Has
Arrived”. Accessed 1.26.17
https://futurism.com/videos/say-goodbye-to-cracks-selfhealing-concrete-has-arrived/
[5] “Finalist for the European Inventor Award 2015”.
European Patent Office. 2015. Accessed 2.9.17
https://www.epo.org/learning-events/europeaninventor/finalists/2015/jonkers.html
[6] “Bio-healing: An application for the repair of aged
mortars”. Materiaux & Techniques. Published 11.2.2015.
Accessed 2.21.2017
http://www.mattechjournal.org/articles/mattech/abs/2015/02/mt150013/mt15001
3.html
[7] Schöttler, U. (November 30, 1979). "On the Anaerobic
Metabolism of Three Species of Nereis (Annelida)" (PDF).
Marine
Ecology
Progress
Series.
1:
249–54.
doi:10.3354/meps001249. ISSN 1616-1599. Retrieved
February 22, 2017.
http://www.int-res.com/articles/meps/1/m001p249.pdf
[8] Jonkers, Hendrik M. & Mors, Renee. “Full scale
application of bacteria-based self-healing for repair purposes”.
Concrete Repair, Rehabilitation and Retrofitting III: 3rd
International Edition. Published: Taylor & Francis Group,
London. 2012. Accessed 3.1.2017
https://books.google.com/books?hl=en&lr=&id=nwbNBQA
AQBAJ&oi=fnd&pg=PA349&dq=Full+scale+application+of
+bacteria-based+selfhealing+concrete+for+repair+purposes&ots=kEmBf1ZzOf&s
ig=96Rg48A0n_Wo98OapjRN5povIBc#v=onepage&q=Full
%20scale%20application%20of%20bacteria-based%20selfhealing%20concrete%20for%20repair%20purposes&f=false
[9] Xu, Jing & Yao, Wu. “Multiscale mechanical
quantification of self-healing concrete incorporating nonureolytic bacteria-based healing agent”. ScienceDirect.
Published
10.2014
Accessed
2.21.2017
http://www.sciencedirect.com/science/article/pii/S000888461
4001203
[10] Bureau of Policy & Research and Bureau Of Law And
Adjustment. Office of New York City Comptroller Scott M.
Stringer. “Pothole City: A Data-Driven Look at NYC
Roadways”. 7.2015. Accessed 1.12.17
https://comptroller.nyc.gov/wpcontent/uploads/documents/ClaimStat-Alert-July-2015.pdf
[11] C. Burnett. V Kogan. “The Politics of Potholes: Service
Quality and Retrospective Voting in Local Elections”
11.11.2016.
Accessed
1.11.17
http://rt4rf9qn2y.search.serialssolutions.com/?genre=article&
title=Journal%20of%20Politics&atitle=The%20Politics%20o
f%20Potholes%3A%20Service%20Quality%20and%20Retro
spective%20Voting%20in%20Local%20Elections.&author=
Burnett%2C%20Craig%20M.&authors=Burnett%2C%20Cra
ig%20M.%3BKogan%2C%20Vladimir&date=20170101&vo
lume=79&issue=1&spage=302&issn=00223816
[12] “2017 Report Card for America’s Infrastructure; Roads:
Investment and Funding” American Society of Civil
Engineers. Accessed 3.30.2017
http://www.infrastructurereportcard.org/
ACKNOWLEDGEMENTS
We would like to thank the civil engineering faculty at
the University of Pittsburgh for peaking our interests in the
fascinating world of civil engineering. In addition, we would
like to thank Lindsay Pietz, our conference co-chair, and Ben
Staud, our conference chair, for their invaluable constructive
criticism and lesson in traditional pavement design.
9