Self healing concrete

A special type of concrete which provided with specific bacteria to fill the cracks in the concrete by converting the unreacted silica(cement) to limestone.

1. PRESENTATION ON “SELF HEALING CONCRETE” PRESENTED BY : IRSHAD ANSARI

2. CONTENT Introduction Necessity Bacteria Working on self healing concrete Methods Advantages Disadvantages Applications Conclusion

3. 1. INTRODUCTION DEFINITION- S elf healing concrete is a concrete which heals itself when it comes in contact with air and water, it produces lime on outer layer of concrete. In most of the traditional concrete mixtures 20-30% of the cement is left unhydrated. If cracking of the concrete occurs, unreacted cement grains may become exposed to moisture penetrating the cracks. In that case the hydration process may start again and hydration products may fill up and heal the crack.

4. NECESSSITY

5. BACTERIA Most of the bacteria belongs to genus bacillus are fulfilling required criteria discusseed above. Some of the list of bacteria are- Pseudofirmus Cohnii Filla Pasteurii The suitable chemical precursor found to be most suitable is “CALCIUM LACTATE”.

6. Negatively charged cell wall and the presence of positive charged ions Biomineral production by means of bind Bacteria structure

7. WORKING ON SELF HEALING CONCRETE Self healing concrete is a product that will biologically produce lime stone to heal cracks that appear on the surface of concrete structures. Ca(C3H5O2)2 + 7O2 CaCO3 + 5CO2 + 5H2O (calcium lactate) (lime) Specially selected types of the bacteria genus bacillus along with a calcium–based nutrients known as calcium lactate, and nitrogen and phosphorus, are added to the ingredients of the concrete when it is being mixed.

8. Crack exposes bacteria Bacteria multiply when water fills crack Bacteria produce healing products

9. METHODS BY DIRECT APPLICATION The bacteria and the chemical precursor are added directly while making the concrete ENCAPSULATION LWA The part of the coarse aggregate is replaced by the light weight aggregate, which is impregnated with the twice the calcium lactate solution and the spores of bacteria After impregnation the clay particles with 6% healing agents and the concrete is made

10. ADVANTAGES Helps to fill the cracks Improvement in compressive strength of concrete Better resistance towards freeze thaw attack reduction Reduction in permeability of concrete Reduction in corrosion of reinforced concrete Helps to reduce maintenance and repair

11. DISADVANTAGES Cost of self healing concrete is double than conventional concrete Growth of any bacteria is not good in any atmosphere media There is no IS code or other code is available Investigation of calcite precipitation is costly studied Skilled labor is required

12. APPLICATIONS Self healing concrete can be used for sectors such as tunnel-lining, structural basement walls, highways, bridges, concrete floors and marine structures This new technology can provide ways to durable roads High strength buildings with more earing capacity Long lasting river banks Erosion prevention of loose sands

13. CONCLUSION Microbial concrete technology has proved to be the better than many conventional technologies because of its ecofriendly nature and self healing abilities and increase in durability of various building materials and give them high strength for more bearing capacity and increase the life of the building Hence, self healing concrete is crack resistant Which protects the concrete and reinforcement from cracks and from corrosion By doing this, it prevents water to percolate into reinforced steel concrete and hence it does not comes in contact with reinforcements Thus, it prevents reinforcement from corrosion

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