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Use of bacteria in a self healing concrete
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The use of bacteria to create self-healing concrete

Last Updated on January 20, 2023 by Admin

In an age where creating materials that can stand the test of time is more critical than ever, researchers have recently been looking into a new potential solution – self-healing concrete. This article will discuss what exactly this is and how bacteria can be used to improve the durability of concrete structures. Read on to find out more about this revolutionary technology!

Introduction

Bacteria are tiny living organisms that can be found everywhere on earth. They are essential for the decomposition of dead organic matter and the recycling of nutrients in the environment. In recent years, scientists have been investigating the use of bacteria to create self-healing concrete.

When concrete cracks, water, and oxygen enter the cracks and begin to corrode the steel reinforcement bars (rebars). This process, known as concrete cancer, can cause severe structural damage to buildings and other structures. Self-healing concrete is designed to repair itself when it cracks by using bacteria to fill the cracks with calcium carbonate.

Calcium carbonate is a white solid found naturally in rocks such as limestone and marble. It is also a major component of seashells and coral reefs. When mixed with water, calcium carbonate forms a thick paste that can fill in cracks in concrete.

The bacteria used in self-healing concrete are usually Sporosarcina pasteurii or Bacillus subtilis. These bacteria produce calcite, a type of calcium carbonate when they come into contact with calcium hydroxide (a common ingredient in cement).

The idea of using bacteria to create self-healing concrete was first proposed in the early 1990s by Dr. Henk Jonkers of Delft University of Technology in the Netherlands. Since then, several research groups have been working on developing this technology further. 

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What is Self-Healing Concrete?

When concrete cracks, water and oxygen enter the structure and cause corrosion of the steel reinforcement. This process leads to further cracking and spalling of the concrete, which can result in significant structural damage. A new type of concrete, known as self-healing concrete, has been developed that uses bacteria to repair cracks when they occur.

The bacteria used in self-healing concrete are known as Sporosarcina pasteurii. These bacteria produce calcium carbonate, filling the cracks and repairing them. The bacteria are encapsulated in a polymer material that is mixed into the concrete.

When a crack occurs, the water and oxygen entering the crack activate the bacteria, producing calcium carbonate and repairing the crack.

Self-healing concrete is effective at repairing cracks up to 0.4 mm wide. The repaired cracks are not visible to the naked eye and do not reduce the strength of the concrete. Self-healing concrete is still in development and is not yet commercially available.

What is Bacterial concrete?

Bacterial concrete is a type of concrete that uses bacteria to create calcium carbonate, which helps to bind the concrete together. The bacteria are mixed with the concrete mix and then left to grow for some time before the concrete is set.

This type of concrete is stronger and more durable than traditional concrete, making it an ideal choice for construction projects.

Bacterial concrete, also known as bio-concrete, is a type of self-healing concrete that uses bacteria to repair cracks and damage in the concrete.

The bacteria are embedded in the concrete mixture before it is poured and is encapsulated in small capsules that dissolve when they come into contact with water.

When a crack forms in the concrete, water enters the crack and dissolves the capsules, releasing the bacteria, the bacteria then consume nutrients embedded in the concrete mixture and produce limestone, which fills the crack and seals it, thus healing the concrete.

One of the most commonly used bacteria in bacterial concrete is the Bacillus bacteria. These bacteria are naturally occurring and can be found in soil and water. They are known for their ability to produce calcium carbonate, which can fill cracks in concrete and repair damage.

Bacterial concrete can potentially improve the durability and longevity of concrete structures. It can reduce the need for frequent repairs and maintenance and can also help to reduce the carbon footprint of the construction industry.

However, it is still a relatively new field of research, and more studies are needed to fully understand the potential of bacterial concrete and develop effective methods for its implementation in construction projects.

Types of Bacteria Used in Self-Healing Concrete

Bacteria used in self-healing concrete are typically strains of Escherichia coli or Bacillus subtilis. These bacteria can secrete calcium carbonate, which can fill in cracks and help to repair concrete structures.

For the bacteria to be effective, they must survive in the harsh concrete environment. This means that they must be able to withstand high levels of salt, heat, and drought.

The bacteria used in self-healing concrete can also produce urease, an enzyme that helps break down urea into carbon dioxide and ammonia.

These products help reduce the concrete’s alkalinity, which can cause cracking over time. Other types of bacteria may also be used, but these two are the most commonly used in self-healing concrete applications.

What is the application of bacterial concrete?

Bacterial concrete, also known as bio-concrete, has many potential applications in the construction industry. Some of the most notable applications include:

  1. Repair of cracks: Bacterial concrete can be used to repair cracks that form in concrete structures over time. The bacteria can fill the cracks and seal them, which can help improve the structure’s durability and longevity.
  2. Durability enhancement: Bacterial concrete can enhance the durability and strength of concrete structures. This is achieved by filling the cracks and pores in the concrete with calcium carbonate, which can help to improve the concrete’s overall performance and resistance to damage.
  3. Maintenance: Bacterial concrete can be used to reduce the need for frequent repairs and maintenance of concrete structures. This can help to save time and money and can also help to reduce the environmental impact of construction projects.
  4. Infrastructure: Bacterial concrete can be used in a wide range of infrastructure projects, such as bridges, roads, and buildings. The ability of the concrete to self-heal can help to improve the longevity and reliability of these structures and can also help to reduce the need for frequent repairs and maintenance.
  5. Climate change mitigation: Bacterial concrete can also be used to mitigate the effects of climate change. The ability of the concrete to self-heal can help to improve the resilience of concrete structures to extreme weather events, such as heavy rainfall and flooding.
  6. Underground structures: Bacterial concrete can be used for underground structures such as tunnels, mines, and underground parking, where the cracks and damages are hard to detect and fix by humans. The ability of the concrete to self-heal can help to improve the durability and longevity of these structures.

It is important to note that while the applications are many, bacterial concrete is still a relatively new field of research and not yet widely used in construction projects. More studies are needed to fully understand bacterial concrete’s potential and develop effective methods for its implementation in construction projects.

How does self-healing concrete work

Self-healing concrete uses microorganisms or other materials to repair cracks that form in the concrete over time. One method of self-healing concrete utilizes bacteria embedded in the concrete mixture before it is poured.

The bacteria are encapsulated in small capsules made of a material that dissolves when it comes into contact with water, when a crack forms in the concrete, water enters the crack and dissolves the capsules, releasing the bacteria.

The bacteria then consume nutrients embedded in the concrete mixture and produce limestone, which fills the crack and seals it.

Another method of self-healing concrete uses materials like shape memory polymers embedded in the concrete mixture and can seal the crack when external triggers like temperature change, pH change, or moisture activate them. In addition, some self-healing concrete also incorporates sensors to detect cracks and trigger the healing process.

It is important to note that self-healing concrete is still being researched and is not yet widely used in construction projects. However, it can significantly improve concrete structures’ durability and longevity.

Advantages and Disadvantages of Bacterial Concrete

There are many potential advantages to using bacteria to create self-healing concrete. Bacteria are very efficient at repairing cracks and can help to extend the life of concrete structures. Bacterial concrete is much more environmentally friendly than traditional concrete, using less energy and water.

However, there are also some potential disadvantages to using bacterial concrete. One of the biggest concerns is that the bacteria could escape from the concrete and enter the environment, where they could cause harm.

Additionally, if the concrete is not sealed correctly, it could allow moisture and oxygen to enter, providing an ideal environment for bacteria to thrive.

Finally, the cost of producing bacterial concrete is much higher than traditional concrete due to the need for specialized equipment and materials. Additionally, it can take much longer to cure bacterial concrete than traditional concrete, which may not be suitable for all applications.

Process of Making Self-Healing Concrete

Concrete is the most widely used construction material in the world, and its durability is crucial to the infrastructure of our built environment. However, concrete is prone to cracking, leading to structural problems and expensive repairs.

Researchers have now developed a new type of concrete that can heal itself when it cracks. This “self-healing concrete” is made with bacteria that are activated by water and fill in the cracks as they grow.

Making self-healing concrete begins with mixing bacteria into the concrete mix. The bacteria are encased in calcium carbonate, protecting them from heat and cold. Once the concrete is cast, the bacteria go into a dormant state.

When cracks form in the concrete, water seeps in and activates the bacteria. The bacteria then grow and multiply, producing calcium carbonate to fill the cracks. After a few days, the cracks completely healed without human intervention.

This self-healing concrete has potential applications in buildings, bridges, and roads. It could help extend the lifespan of our infrastructure and reduce repair costs.

Self-healing concrete is still in its early stages of development, but the potential for this material is exciting. It could revolutionize the way we build and maintain our infrastructure in the future.

Examples of Self-Healing Concrete Projects

1. The Netherlands: In 2003, a trial was carried out on a motorway in the Netherlands using bacteria-based self-healing concrete.

The aim was to reduce the number of potholes that form over time due to weathering and wear and tear. The concrete was mixed with spores of Bacillus subtilis, which is a common soil bacterium. The bacteria are activated when the concrete cracks and produce limestone, filling the crack.

2. United Kingdom: A trial was also carried out on a section of the M25 motorway in the UK in 2006. This time, the concrete was mixed with Sporosarcina pasteurii, another type of bacteria found in soil and water. This bacterium produces calcium carbonate, filling cracks when they appear.

3. United States: In 2009, scientists at Vanderbilt University in Nashville, Tennessee, developed a self-healing concrete that uses a gel made from living bacteria and sand particles. The gel is mixed into the concrete before it sets. When cracks appear, the gel oozes out and fills them in.

4. China: In 2011, researchers in China developed a self-healing concrete that uses a polymer instead of bacteria. The polymer is mixed into the concrete before it sets, and when cracks appear, it expands and fills them in.

5. Australia: In 2012, researchers in Australia developed a self-healing concrete that combines bacteria and polymer. The bacteria and polymer work together to fill in cracks when they appear. This self-healing concrete has been used in several projects, including the construction of a bridge in Sydney, Australia.

These are just a few examples of self-healing concrete projects. Researchers and engineers continue to create new ways to make concrete more durable, resilient, and self-healing.

Conclusion

Self-healing concrete is an exciting new technology that has the potential to revolutionize the construction industry. Thanks to advancements in research, we can now use bacteria to heal existing cracks and prevent new ones from forming. This not only makes buildings safer but also reduces maintenance costs and increases their lifespan. Although this technology is still in its infancy, it holds immense promise for improving sustainability and resilience in our built environment.

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FAQs

What types of bacteria is used in self-healing concrete?

Self-healing concrete is a new type of concrete that uses bacteria to fill in cracks and repair damage. The most common type of bacteria used for this purpose is Bacillus bacteria, which produces calcium carbonate. Other types of bacteria that have been studied for use in self-healing concrete include Sporosarcina pasteurii and Sporosarcina ureae, which also produce calcium carbonate but can also fix nitrogen and produce urea. Additionally, other microorganisms like fungi, yeasts, and algae have also been studied for their potential use in self-healing concrete.

How is the self-healing concrete made?

The self-healing concrete is made by adding a bacteria to the concrete mix. The bacteria are dormant when the concrete is mixed and placed. Once the concrete cracks, the bacteria become active and start to produce calcium carbonate. This process fills in the cracks and makes the concrete stronger.

What are the Benefits of self-healing concrete?

The benefits of self-healing concrete are that it can reduce the need for repairs, it can extend the life of a structure, and it can improve the safety of a structure. Another benefit is that self-healing concrete can be less expensive to maintain than traditional concrete. Additionally, self-healing concrete can improve the overall appearance of a structure by filling in any cracks or damage that may be present.

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