This document discusses self-healing concrete and the role of bacteria. It introduces self-healing concrete as concrete that can seal its own cracks through a bacterial process. Various types of bacteria used are listed, including Bacillus species. The preparation and mechanisms are described, with bacteria feeding on nutrients and producing minerals to fill cracks. Advantages include self-repair without external aid and improved strength and durability, while disadvantages include higher costs and limited environments for bacterial growth. The conclusion is that self-healing concrete provides long-term sustainability for infrastructure.

2. Table of content
• Introduction
• Which Bacteria used in concrete and types?
• Self healing concrete Procedure
• Mechanism of bacteria in concrete
• Advantages and disadvantages
• Conclusion

3. INTRODUCTION
"The name suggests that it is a self healed concrete "
• Definition: Self healing of cracks or self-filling of cracks by the
help of bacterial process after hardening is known as self healing
concrete, It is also known as bacterial concrete.
• It can be observed that small cracks that occur in a structure of
width in the range of 0.05 to 0.1mm gets completely sealed in
repetitive dry and wet cycles.
• These types of bacteria can be in dormant cell and be viable for
over 200 years under dry conditions. These bacteria acts as a
catalyst in the cracks healing process.

4. Which Bacteria used in concrete and types?
There are various types of bacteria were used in bacterial concrete
construction are:
✓ Bacillus pasteurizing
✓ Bacillus sphaericus
✓ Escherichia coli
✓ Bacillus subtilis
• Bacillus cohnii
• Bacillus balodurans
✓ Bacillus pseudofirmus
• Any of bacillus is rod-shaped, gram-positive, aerobic or (under some
conditions) anaerobic bacteria widely found in soil and water.

5. Self healing concrete Preparation
• @civilogy
• Bacterial concrete can be prepared in two ways,
• By direct application
• By encapsulation in lightweight concrete
In the direct application method, bacterial spores and calcium lactate is
added into concrete directly when mixing of concrete is done.
• Bacterial spores
• Organics
• ▸ By encapsulation method the bacteria and its food i.e. calcium lactate,
are placed inside treated clay pellets and concrete is prepared. About 6% of
the clay pellets are added for making bacterial concrete.

6. Mechanism of bacteria in concrete
• When cracks are formed in concrete, moisture comes in contact with calcium
in the concrete and bacteria.
▸ Bacteria feeds on calcium lactate (Nutrient) and produces limestone.
CaO +H;0 → Ca(OH)
Ca(OH),+CO_ → CaCOy+HyO
• > From the above chemical reaction,
• > The carbon hydroxide reacts with atmospheric carbon-dioxide to form
limestone and water.
• > Formed limestone hardens to fill up the cracks and extra water continues
the reaction.

7. Advantages
► Self-repairing of cracks without any external aide.
► Significant increase in compressive strength and flexural strength when
compared to normal concrete.
► Resistance towards freeze-thaw attacks.
► Reduction in permeability of concrete.
► Reduces the corrosion of steel due to the cracks formation and improves the
durability of steel reinforced concrete.
• Bacillus bacteria are harmless to human life and hence it can be used
effectively.

8. Disadvantages
► Cost of bacterial concrete is double than conventional concrete.
▸ Growth of bacteria is not good in any atmosphere and media.
► The clay pellets holding the self-healing agent comprise 20% of the
volume of the concrete. This may become a shear zone or fault zone in
the concrete.
► Design of mix concrete with bacteria here is not available any IS
code or other code.
► Investigation of calcite precipitate is costly.

9. Conclusion
From this studies, It is clear that we can implement this technology to
improve many properties of concrete.
• Important aspect to consider is cost but when we look for long term
solution, self healing concrete is the perfect one.
• 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.