Self-Healing Concrete

Published on 21 May 2022. Written by Reddy Shekar

Cracks are a common phenomenon in concrete structures due to shrinkage. These cracks create a path for liquids and gases (contains harmful substances) into the concrete members. Reinforcement may get corroded if the liquids reach the steel reinforcement. So, it is necessary to take precautionary measures to end these cracks at the very beginning stage. Self-healing concrete is one of the ways to avoid the formation of cracks problem.

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The maintenance and repair work of concrete structure are usually high in cost. Self-healing concrete is an inexpensive solution compared to other conventional methods. It also contributes longer service life to structures. After the years of research and experiments, Dr. Henk Jonkers, a microbiologist developed the self-healing concrete.

The need for Self-Healing concrete: Concrete is the most important building material but most of the concrete members are subject to cracks. Even very small cracks on the concrete surface make the whole building unsafe. Cracks allow water to seeps and it will deteriorate the concrete and corrode the steel reinforcement. It will finally reduce the lifespan of the building. Self-healing concrete is a product that will biologically produce limestone to heal the cracks.

How it works: The specially selected type of bacteria (genus Bacillus), along with a calcium-based nutrient known as calcium lactate, nitrogen and phosphorus are added to the ingredients of the concrete when it is being mixed. These self-healing agents can lie within the concrete for up to 200 years. When concrete cracks and water starts to seep through the cracks, the spores of the bacteria develop contact with the water and nutrients. Then, bacteria start to feed on calcium lactate. As the bacteria feed, oxygen is consumed and the soluble calcium lactate is converted into limestone. The limestone solidifies on the cracked surface, by sealing it up. Conduct the standard tests on both self-healing concrete and normal concrete to find the efficient product.

The consumption of oxygen during the bacterial conversion of calcium lactate to limestone has an extra advantage. Oxygen is the essential element in corrosion of steel. When the bacterial activity has consumed it all it increases the durability of structures.

Self-Healing agents: Bacteria: - The important step in preparing self-healing concrete is to find the right bacteria. It should have the ability to survive in an extreme alkaline environment. Because cement and water have a pH value of up to 13.

Nutrients: - Calcium lactate, Nitrogen and Phosphorus.

Benefits: The following are some of the advantages of self-healing concrete,

Self-repairing of cracks without any external maintenance.

Increases the service life of the structure.

Increase in compressive and flexure strength compared to normal concrete.

Reduces the permeability of concrete.

Bacteria used in concrete making process is harmless to human life.

Reduces the corrosion of steel reinforcement.

Resistance towards freeze-thaw attacks.

Disadvantages:

Cost of the self-healing is much higher than normal concrete.

Design of concrete mix with bacteria and nutrients is not available in IS code or any other code.

Conclusion: Self-healing concrete is the best solution for the demand of sustainable concrete due to its ability of self-repair and durability. In future, self-healing concrete is going to play the most important role in concrete technology.

Kit required to develop Self-Healing Concrete:

• Bacteria and nutrients

Technologies you will learn by working on Self-Healing Concrete:

• Concrete Technology

Any Questions?