BACTERIAL BASED SELF HEALING CONCRETE
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This document discusses bacterial-based self-healing concrete. It describes how certain bacteria like Bacillus pasteurii are added to concrete mix and remain dormant. When cracks form and water enters, the bacteria are activated and precipitate calcium carbonate to seal the cracks. The bacteria use oxygen and calcium lactate in the concrete to form insoluble limestone crystals through bio-mineralization. Research shows bacterial concrete achieves up to 88% reduction in water and chloride permeability while increasing compressive strength over time as cracks self-heal. Potential applications include underwater and water-bearing structures.
BACTERIAL BASED SELF HEALING CONCRETE
- 1. G M INSTITUTE OF TECHNOLOGY, DAVANAGERE Department Of Civil Engineering. 2017 – 2018 Presented by: NIKHIL S 4GM14CV028 BACTERIAL BASED SELF-HEALING CONCRETE
- 2. CONTENTS INTRODUCTION BACTERIAL CONCRETE BACTERIA USED CHARACTERISTICS OF BACTERIA CULTURING AND MIXING OF BACTERIAL CONCRETE MACHANISM OF HEALING CHEMICAL REACTION APPLICATION ADVANTAGES & DISADVANTAGES CONCLUSION 2
- 3. INTRODUCTION • Cracks in concrete formed due to various reasons which allows chemicals and water to enter ,and causes corrosion of reinforcement and finally leads to failure of structure. • There are different methods for prevention and control of cracks , bacterial concrete is one of them. • The bacteria’s which are added to concrete and makes the concrete which can repair itself without human work called Bacterial based self healing concrete. • Bacteria’s added with soluble calcium lactate (feed) which convert invert into insoluble crystals of calcium carbonate , when exposed to atmosphere. • Which seals the cracks and makes the concrete impermeable. 3
- 4. BACTERIAL CONCRETE • The principle of the concrete is “Bio mineralization” , precipitation of crystal by using bacteria. • Bacteria’s mixed with concrete at the time of mixing and they remain hibernated for 200 years. • Gets activated when exposed to water or moisture. • The concrete is high in alkalinity and pH varies from 8-9 ,the bacteria’s used should be able to sustain alkaline environment. • Bacillus group of bacteria’s are common soil bacterium and able to sustain high alkaline and harsh environment. • These bacteria’s able to precipitate calcite crystals. 4
- 5. TYPES OF BACILLUS BACTERIA’S There are different types bacteria’s are listed below • Bacillus pasteurii • Bacillus subtilis • Bacillus sphaericus • Bacillus cohnii • Bacillus pseudofirmus Bacillus pasteurii is most commonly used soil bacteria in concrete. 5
- 6. BACTERIA USED Bacillus pasteurii Animated images Bacillus pasteurii diagram Microscopic images of Bacillus pasteurii
- 7. Characteristics Bacillus Pasteurii • Single celled organisms. • Commonly available in all type of soils. • Doesn’t cause any harm to human. • Long rods, 0.6-0.8 μm in width and 2.0 to 3.0 μm in length. • Doesn’t react with other ingredients of the concrete . • Susceptible to high alkaline environment (cultured bacteria up to 13). • Heals up to 0.4 mm wide cracks. • Suitable for all type of concrete. 7
- 8. Culturing & mixing bacteria concrete • Primarily 12.5 gm. of nutrient (calcium lactate) is added to a 500ml conical flask containing distilled water. • It is than covered with thin cotton plug and made it as airtight. • It is than sterilized using cooker for about 10-20 minutes , now the solution is free from any contaminants and clear orange solution is obtained. • Later the flask is opened up and exactly 1 ml of bacterium is added to the sterilized flask and kept shake at a speed of 150-200 rpm overnight. • After 24 hours the bacterium solution was found to be yellow turbid solution with bacteria having cell concentration of 105 cells per ml. 8
- 9. BACTERIAL SOLUTION 9 Incubator Bacterial solution
- 10. MACHANISM OF SELF HEALING • When the cracks develops it allows water and moisture content into the concrete • As soon as the water enters the concrete through cracks ,the bacteria’s become active and it start feeding the calcium lactate and absorbs the oxygen from water or moisture and start precipitating the insoluble crystals of calcium carbonate ( lime stone ) and seals the cracks • When the cracks completely filled and again bacteria’s goes to hibernate. • In the favourable environment it takes around 2 weeks to completely heal a crack width of 0.4mm. 10
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- 13. Healing progress shown in SEM 13
- 14. Healing shown in microscope 14
- 15. Chemical reaction • As the bacteria feeds oxygen is consumed and the soluble calcium lactate is converted to insoluble limestone. • The limestone solidifies on the cracked surface, thereby sealing it up. • Tests all show that bacteria embedded concrete has lower water and chloride permeability by 88% • Reaction: • Ca(C3H5O2)2 + 7O2 → CaCO3 + 5O2 +5H2O (Calcium lactate) • The crystals expand until the entire gap is filled. • The extra molecule of water again continuous the reaction. 15
- 16. Results by Research papers Strength Study Tests on M30 concrete Conventional Concrete Bio Concrete 7 days 28 days 7 days 28 days Compressive Strength 20.85 30.00 27.10 38.95 Split Tensile Strength 3.26 4.51 3.93 5.13 16 Results in (Mpa) for Concrete and bacteria cell concentration 10^5/ml mixing water
- 17. SEM images for cell concentration 17
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- 19. Application • Used in underwater structure • Used in water Bearing structure • Used in under ground structures • Used in pre cast members • Used for all types of concrete works 19
- 20. ADVANTAGES • Concrete become impermeable . • Repairs without a human work. • Self-healing concrete also prevents the exposure of the internal reinforcements. • It has made to extend the life span of a concrete structure of any size, shape. • Increase the strength of the concrete. 20
- 21. DIS ADVANTAGES • Cost of construction more. • Skilled labour required. • Bacterial culture required. • It is still developing technology. • Accuracy in mixing and culturing. 21
- 22. Conclusion • Microbial mineral precipitation resulting improve the overall behaviour of concrete. • The greatest improvement in compressive strength occurs at cell concentrations of 10^5 cells/ml mixing water. • The study result shows that increase in compressive strength of concrete. • Less permeability and corrosion resistance. 22
- 23. References • Ramachandran S.K., Ramakrishnan V. and Bang S.S., Remediation of concrete using microorganisms, ACI Materials Journal 98(1), 3-9 (2001) • S. SUNIL PRATAP REDDY International Journal of Earth Sciences and Engineering ISSN 0974- 5904, Vol. 03, No. 01, February 2010, pp. 116-124. • Chintalapudi Karthik, Rama Mohan Rao.P. Properties of Bacterial-Based Self-healing concrete, International journal of chem tech Research (2016) vol.9, No.02 pp182-188. 23
- 24. • Navneethchahal, Rafat Siddique, Anitha Rajar (2012). “Influence of Bacteria on the compressive strength, water absorption of the concrete”, Asian journal of Civil Engineering, Vol 1, No 1, 43-55. • Abhijit Sing Parmar, Ankit Patel (2013),”Improvement on the concrete cracks by using Bacillus Pasteurii”, International journal for Scientific Research & Development, Vol 1, Issue 1. 24
- 25. Thank You