Formation of cracks in concrete is a common phenomenon that allows many chemicals, water to seep inside leading to decrease in durability, including progressive drop in concrete strength. The maintenance and repair of structural concrete is very complex phenomenon. Self-healing concrete, using bacteria at the time of mixing, is an impressive solution to overcome these kinds of adverse effects. It is an economical way is to prepare concrete of better quality. The study was carried out to investigate the concrete performance by adding bacteria “Bacillus subtilis”. This Self-Healing concrete is also known as as Bio-concrete. Bacteria was induced directly in the concrete mix along with calcium lactate i.e., an organic precursor producing calcium carbonate crystals that block cracks and pores in the concrete. Samples were made with different quantities of bacteria and results showed significant increase in compressive strength of concrete and decrease in permeability. The concrete micro-structure was observed under SEM which also confirmed the experimental results obtained.

1. PROPERTIES OF SELF-
HEALING CONCRETE
PREPARED BY : ENGR.MUHAMMAD MUSAAB

2. PRESENTATION
OUTLINE
INTRODUCTION
SELF-HEALING CONCRETE
BACTERIA SELECTION
WORKING PROCESS
PREPARATION OF SHC
TESTING
ADVANTAGES
DISADVANTAGES
APPLICATION
CONCLUSION AND
REFERENCES

3. INTRODUCTION
Concrete is the most common material used in construction. Cracks formation is one of the
most common phenomenon in concrete.
Many research works are being carried out in the world for the modification of concrete
to make it more durable, strong, user friendly and environmental friendly. Many
different materials are combined with concrete like carbon fibers, fly ash, blast furnace
slag etc. to check properties to check concrete performance.
The world is getting advanced in the field of construction. Researches are being made
to improve the concrete behavior by the addition of micro-organisms.

4. SELF-HEALING CONCRETE
Self-healing concrete also known as Bio-Concrete can be produced by
adding bacteria in concrete along with its nutrient to keep it alive for
production of calcite to fill crack after precipitation. Bacteria was
added in concrete along with calcium lactate to repair cracks.
The focus is not only to keep bacteria alive but also to generate much
calcite to fill the cracks.

5. WHICH BACTERIA IS USED
The bacteria from Bacillus family is chosen for self-healing in concrete. Following are
those bacteria:
• Bacillus Pastuerii
• Bacillus Sphearicus
• Bacillus Pseudofirmu
• Bacillus Subtilis

6. BACTERIA SUBTILIS
• Bacillus subtilis, also known as the hay bacillus or grass bacillus, is a Gram-
positive, catalase-positive bacterium, found in soil and the gastrointestinal tract of
ruminants and humans. A member of the genus Bacillus, B. subtilis is rod-shaped,
and can form a tough, protective endospore, allowing it to tolerate extreme
environmental conditions. B. subtilis has historically been classified as an obligate
aerobe, though evidence exists that it is a facultative anaerobe. B. subtilis is
considered the best studied Gram-positive bacterium and a model organism to study
bacterial chromosome replication and cell differentiation. It is one of the bacterial
champions in secreted enzyme production and used on an industrial scale by
biotechnology companies.

7. WHY BACTERIA SUBTILIS
1
It is able to adjust to
alkaline atmosphere
in concrete for the
production of calcium
carbonate.
2
It produces copious
amount of calcium
carbonate without
being affected by
calcium ion
concentration.
3
It is able to
withstand high
pressure and it is
oxygen brilliant to
consume much
oxygen and minimize
corrosion of steel.
4
It is gram-positive bacteria having
an ability to form spores when
subjected to unfavorable conditions.
This spore formation provides its
protection against high mechanical
pressure and alkaline environment,
making it ideal selection

8. WORKING PROCESS
• In bio-concrete when water seeps through the cracks ,the bacteria get activated from
its stage of dormancy and the bacteria starts to feed on calcium lactate and in turn
produces calcium carbonate through its metabolic activities which acts as a healing
material.
• Ca(C3H5O2)2 + 7O2 → CaCo3+5Co2+5H20
• Where,Ca(C3H5O2) is Calcium lactate; and CaCo3 is lime

9. MATERIAL SELECTION
• Ordinary Portland Cement
• Crushed aggregate of size 20mm
• Sand
• Water
• Calcium Lactate
• Bacillus Subtilis

10. QUANTITY OF
BACTERIA
AND CALCIUM
LACTATE PER
CUBIC METER
CONCRETE
Bacteria Subtilis:
8 l/m3 (0.8%)
Calcium lactate:
20 kg/m3 (0.8%)

11. PREPARATION OF CULTURAL BACTERIA
Bacillus subtilis was casted on
nutrient agar plates
A nutrient broth was prepared
for the further growth of
bacteria. L.B (Composition:
Nacl, peptone and yeast
extract) was added in distilled
water.
200 ml broth was prepared in
500 ml conical flask. Then a
single colony of bacterial
culture was picked up from
agar plate and added in the
nutrient broth.
Then it was set for autoclaving
at 121oC for 15 min. After that
the flask was placed in
incubator at 37oC for 24 hours.
After that for storage the flask
was placed in refrigerator at
4oC till further use.
Contamination was checked
periodically.

12. PREPARATION OF CULTURAL BACTERIA
Fig.2.1 Bacteria grown on agar plate Fig 2.2 Culture grown in nutrient broth Fig 2.3 Stored in refrigerator till further use

13. SAMPLES PREPARATION
MIX DESIGN:
Suitable materials were mixed to prepare Concrete of mix ratio 1:1.5:3. The water-
cement ration was kept 0.4.
0ml,15ml,20ml,30ml of Bacteria was added in different cubes.

14. SAMPLE PREPARATION
PREPARATION OF CUBES:
Standard size cubes of 152mm*152mm*152mm were casted with different quantities
of Bacteria Subtilis i.e. 0ml,15ml,20ml, 30ml.
After 24 hours of casting, samples were demolded and soaked in clean water for 7,14
and 28 days.

15. HOW BACTERIA IS ADDED?
BY DIRECT
APPLICATION:
The bacteria and
the chemical
precursor(calcium
lactate) are added
directly while
making concrete.
BY ADDING
BACTERIAL
BROTH:
The bacterial
broth prepared is
added along with
calcium lactate
while making
concrete.

16. SAMPLES
TESTING
Following were the
tests conducted:
•Workability
•Surface Cracks repair
•Compressive strength
•SEM for internal cracks
repair

17. 1.WORKABILITY
Concrete workability was
checked by performing
slump test.

18. 2. SURFACE CRACKS HEALING
The specimens were subjected to compressive test machine under controlled and
careful compressive loading till visible cracks appeared on the surface. The crack
widths were measured at different points on the specimens and the cracks with a
width around 1 mm were selected and marked for further observations of self-healing.
The pre-cracked specimens were continued to cure under controlled curing conditions.
After pre-cracking, crack width was measured on regular intervals of 3,7,14 and 28
days and difference between the original crack width and that observed on later days
was considered as a measure of self-healing.

19. SURFACE
CRACKS
HEALING
AFTER 3RD DAY:
Calcite crystals started appearing
on surface.

20. SURFACE
CRACKS
HEALING
AFTER 7TH DAY:
The bacterial action produced more
calcite to fill the cracks

21. SURFACE
CRACKS
HEALING
AFTER 14TH DAY:
The width of cracks started
decreasing significantly due to
calcite crystals filling the cracks.

22. SURFACE
CRACKS
HEALING
AFTER 28TH DAY:
CRACKS WERE HEALED
COMPLETELY.

23. 3.COMPRESSIVE STRENGTH
The compressive strength was measured after 7,14 and 28 days. Cubes with different
quantities of bacteria were tested after 7,14 and 28 days. The compressive strength
increased by increasing quantity of bacteria.
QUANTITY OF BACTERIA
(ml)
COMPRESSIVE STRENGTH
(MPa)
7 days 14 days 28 days
0 11 12.5 21
15 12 14.8 26
20 16 19 28
30 16.5 25 34

24. COMPRESSIVE
STRENGTH AT
7,14,28 DAYS

25. DIFFERENT CONCRETE MIX COMPRESSIVE
STRENGTH
• The 28 days compressive strength of 1:2:4 concrete was found to be 16 MPa while
1:1.5:3 ( with 30 ml bacteria) concrete had 34 MPa compressive strength.

26. 4.SCANNING ELECTRON MICROSCOPE FOR
INTERNAL CRACKS
The scanning electron microscope (SEM) is one of the most versatile instruments
available for the examination and analysis of microstructural characteristics of solid
objects. The primary reason for the SEM’s usefulness is the high resolution that can
be obtained when bulk objects are examined.

27. SEM SAMPLE PREPARATION
• The specimens extracted from the concrete cubes were 25 mm square and had an approximate
thickness of 5 mm.
• First, one side of each specimen was polished with120#, 220#, 320#, and 600# silicon carbide using
a rotating grinder and mounted it against a 25 mm diameter glass plate with epoxy. To make both
sides of the specimen parallel to each other, the samples were cut 2–3 mm thick by using a
diamond slicing wheel with a nonaqueous lubricant (propylene glycol coolant). The specimens were
then lapped with a wheel grinder and polished with 600# silicon carbide. Further polishing was
performed with 100, 50, and 10 micron aluminum powder on a glass plate. The final stage involved
was treating specimens with 5, 3, and 0.25 micron diamond paste using a special polishing
equipment. After each stage of polishing, the specimens were immersed in acetone and placed in an
ultrasonic bath to remove the residual silica film on their surfaces, thus preparing them for the
next stage of polishing.

28. SEM ANALYSIS
Samples were also subjected to
scanning electron microscope
(SEM) analysis to monitor
microstructural changes due to
mineral formation. The crack set
under observation was of 1mm.

29. SEM ANALYSIS
CRACK HEALED
AFTER 28 DAYSCRACK HEALED

30. ADVANTAGES OF SHC
Improvement in compressive
strength of concrete
Reduction in permeability of
concrete
Reduction in corrosion of
reinforcement
The self healing bacterial
concrete helps in reduced
maintenance and repair costs of
steel reinforced concrete
structures.
Oxygen is an agent that can
induce corrosion, as bacteria
feeds on oxygen tendency for
the corrosion of reinforcement
can be reduced.
Self healing bacteria can be
used in places where humans
find it difficult to reach for the
maintenance of the structures.
Hence it reduces risking of
human life in dangerous areas
and also increases the
durability of the structure.
Formation of crack will be
healed in the initial stage itself
thereby increasing the service
life of the structure than
expected life.

31. SAVES MAINTENANCE COST
• Self-healing concrete could save £40bn in maintenance costs. It is estimated that
around £40billion is spent each year in the UK on structural maintenance, and the
majority of these structures are made of concrete.

32. DISADVANTAGES OF SHC
Preparation of self healing concrete needs the requirement of bacteria and calcium
lactate. Preparation of calcium lactate from milk is costlier. Hence preparation of self
healing concrete costs double than conventional concrete.

33. APPLICATIONS OF SHC
For constructing
underground
retainers for
hazardous waste
1
For high rise
building and
buildings in
seismic zones.
2
Water retaining
structures
3
Concrete floors,
Tunnel linings,
basement walls
4

34. CONCLUSION
• Microbial concrete technology has proved to be better than
many conventional technologies because of its:
• Eco- friendly nature, self-healing abilities.
• Reduction in permeability.
• Reduction in reinforcement corrosion.
• The compressive strength is 34 MPa , that is maximum
,when the addition of bacillus subtilis bacteria is 30 ml.
• This concrete technology will soon prove the foundation for
an alternative solution and high quality structures which
will be affordable and environmentally safe.

35. REFERENCES
• IS 10262,”Recommended Guideline For Concrete Mix Design”.
• IS 456:2000,”Plain and Reinforced Concrete-Code of Practice”.
• Sathish Kumar. R, “Experimental Study on the
• Properties of Concrete Made With Alternate Construction Material”, International
Journal of Modern Engineering Research (IJMER), Vol. 2,Issue. 5, Sept.-Oct. 2012, pp-
3006-3012.
• Self-healing concrete repairs itself with bacteria. Ashley P. Taylor (2012).,
• Engineered bacteria can fill cracks in aging concrete.Prof. Claydillow.,(2010)
• H.G. Schlegel, General Microbiology, seventh ed., Cambridge University Press,1993.