Cracking is a common phenomenon in concretes which may prove fatal to the structures by allowing water and various chemicals into the concrete decreasing its strength and making it less servicable. In order to make the cracks heal autonomously, we have developed so many processes. These processes have been explained in this presentation with experimental investigations. For the full-text report, mail me at manaruchimohapatra@gmail.com

1. Self-healing Concrete
A Seminar Presentation by
Manaruchi Mohapatra
(manaruchimohapatra@gmail.com)

2. What does “self-healing” imply?
• Self-healing is mostly defined as the ability of concrete
to repair its small cracks autonomously.
• Basically, the cracks has to be filled by some cementing
material in order to stop the crack to develop and
damage the structure.
• It can prove to be vital as it can improve the strength,
durability and may ultimately increase the life span of a
structure.

3. How can we make
concrete to heal itself?
There are 3 categories of processes to do so.
Natural self-healing processes
Chemical self-healing processes
Biological self-healing processes

4. Several natural processes can partially repair concrete
cracks.
Natural self-healing processes

5. Some other methods are :
• Crack is blocked by impurities in the presence of water
• Crack is further blocked by hydration of the unreacted
cement or cementitious material
• Crack is blocked by the expansion of hydrated
cementitious matrix in the crack flanks (swelling of
calcium silicate hydrate gel)
Natural self-healing processes

6. • It refers to the artificial healing by injecting chemical
compounds into the crack for healing. Self-healing
concrete is designed by mixing chemical liquid
regents (i.e. glue) with fresh concrete in small
containers.
• Two common chemical methods are:
o Hollow pipettes and vessel networks containing glue
o Encapsulated glue
Chemical self-healing processes

7. • Hollow pipettes and vessel networks containing glue
Hollow pipettes contain glue that can be mixed with fresh concrete and
will be ruptured during crack propagation and the glue is released into
the cracks and finally it heals the crack.
Chemical self-healing processes
Crack-healing mechanism using vessels containing glue

8. • Encapsulated glue
Cracks rupture the embedded microcapsules which contains glues
and the glue is released into the crack faces through capillary action
and the crack gets filled.
Chemical self-healing processes
Crack-healing mechanisms using encapsulated glue

9. Biological self-healing processes

10. • Biological precipitation of calcium carbonate
• The most stable precipitated form of calcium carbonate is Calcite.
• Microbial metabolisms provide factors for the precipitate
formation and the cell wall of the bacteria acts as nucleation site.
• Biological calcium carbonate precipitation using ureolytic
bacteria is one of the most popular way to design self-healing
concrete.
Biological self-healing processes

11. Biological self-healing processes
• Biological precipitation of calcium carbonate

12. Biological self-healing processes
• Biological precipitation of calcium carbonate
Schematic scenario of crack healing by microorganisms
(A) crack is propagating into concrete
(B) microorganisms can be activated into crack
(C) microorganisms grow and precipitate calcium carbonate around their wall cells
and can fill the crack

13. Biological self-healing processes
• Biological precipitation of calcium carbonate
Different pictures of microbiological precipitated
calcium carbonate on the concrete cracks, figure (a) is
without magnification, figure (b) with 20x magnification,
(c) with 40x magnification and (d) ESEM picture of
bacterial activates and precipitation of calcium carbonate
with 20000x magnification

14. Biological self-healing processes

15. • The compressive strength of concrete was improved by 14.92% by
adding Bacillus subtilis JC3 as compared to the conventional concrete. It
was found that B. sphaericus improved the compressive strength of
concrete by 30.76% in 3 days, 46.15% in 7 days and 32.21% in 28 as
compared to conventional concrete.
• SEM for bio concrete shows that more dense in micro structures as
compare to conventional concrete (which has more voids in
microstructure), which implies that it enhance strength to the concrete.
• 8.6 × 108 cells per ml of concrete has been found to induce maximum
compressive strength & is taken as “optimum concentration”.
Experimental Investigations

16. Experimental Investigations
SEM of Conventional Concrete
Loose Structure
SEM of Bacteriological Concrete
Dense Structure

17. Experimental Investigations

18. • Advantages
o More resistant to the freezing and thawing condition
o Reduce plastic shrinkage cracks
o High impermeability
o High resistance to chemical attacks
o Regular inspection is not needed
Advantages and Limitations

19. • Limitations
• The cost of self-healing concrete is about double that of
conventional concrete, which is presently about €80 Euros (₹ 6720)
per cubic meter.
• Availability of raw material is not easy.
• Its use is costly in comparison to traditional concrete.
• It requires skilled supervision.
• Difficulty in bacterial injection in sands
• Extremely high pH and extreme conditions hampers the action of
bacteria.
Advantages and Limitations

20. • Introducing the bacteria into the concrete makes it very
beneficial it improves the property of the concrete which is
more than the conventional concrete.
• Bacteria repair the cracks in concrete by producing the
calcium carbonate crystal which block the cracks and repair
it.
• It was found that the bacterial concrete shows the better
value of stress and strain as compared to controlled
concrete for the high strength grade of concrete.
Conclusion

21. Thank You for your time.
References
[1] “A Review of Self-healing Concrete Research Development” by Amirreza Talaiekhozan, Ali Keyvanfar,
Arezo Shafaghat, Ramin Andalib, M.Z Abd Majid, Mohamad Ali Fulazzaky, Rosli Mohamad Zin, Chew Tin
Lee, Mohd Warid Hussin, Norhaliza Hamzah, Nur Fatimah Marwar, H.I. Haidar.
[2] “A review paper on self-healing concrete” by Salmabanu Luhar and Suthar Gaurav.
[3] Research papers presented by Dr.Ramkrishnan, Sookie Bang & Ramesh Panchalan.
[4] Self-healing concrete; “Is self-healing concrete a feasible option to reduce long-term maintenance
cost? An evaluation of construction industry’s future” by Meena Hashemi of UCL Dept. of Civil
Engineering, London
[5] “Bacterial Concrete” (2016) from Civil Engineering Seminars. (URL :
http://civilenggseminar.blogspot.in/2016/06/bacterial-concrete.html)