In my project we studied different types of cracks in construction work, its causes and remedial measures.

1. Guided By:-

2. TYPES OF CRACKS IN MASONRY
STRUCTURES
1. Vertical cracks in sidewalls at corner
2. Vertical cracks around balconies
3. Vertical cracks below the opening in line with the window jambs
4. Vertical cracks at the junction of RCC column and masonry wall
5. Vertical cracks in the top most stories at corners of structures having RCC
slab
6. Horizontal cracks at window lintel or sill level in the top most story
7. Horizontal cracks in the top most story below the RCC slab level.
8. Random cracks in all directions involving both external and internal walls.
9. Diagonal cracks over RCC lintels spanning large openings.
10. Shrinkage cracks.

3.  Poor quality of bricks.
 For masonry work, use the porous stones.
 Absence of grading in before the use of fine aggregate fine mortar.
 If percentage of clay and silt in fine aggregate exceed 3 percent.
 Due to the excessive amount of soluble sulphete.
 Plumb alignment.
 The position of the element in the structure.
 Differential loading.
 Weak mortar.
 Insufficient bond.
 Improper curing.
 High daily temperature variations.
 Atmospheric pollutions.
 Lack of strength at corner and at junction of wall.
 Improper binding of thick walls.
GENERAL CAUSES OF CRACKS:

4.  Plastic Shrinkage Cracking
 Plastic Settlement Cracking
 Drying Shrinkage Crack
 Long Term Shrinkage Cracking
 Concrete Crazing
 Thermal Cracking
 Cracking due to Chemical Reaction
 Steel Corrosion induced Cracking
 Errors in Design and Detailing
 Improper Construction Joint
Causes of cracks in concrete structure

5. 1.Plastic Shrinkage Cracking:
 It occurs within 1 to 8 hours after placing, when subjected to a
very rapid loss of moisture caused by a combination of factors,
which include air and concrete temperatures, relative humidity
and wind velocity at the surface of the concrete. These factors
can combine to cause high rates of surface evaporation in either
hot or cold weather.

6. 2. Plastic Settlement Cracking:
 After initial placement, vibration and finishing concrete has
tendency to continue to consolidate. During this period, the
plastic concrete may be locally restrained by reinforcing steel,
earlier placed hardened concrete or formwork. This local
restraint Fig a, Settlement Crack at Surface . Fig 4b, Settlement
Causing Crack & Void.

7. 3.Drying Shrinkage Crack:
 When associated with reinforcing steel, settlement cracking
increases with increasing bar size, increasing slump and
decreasing cover. The degree of settlement may increase with
insufficient vibration, lack of compaction at top layers of
concrete, or by the use of leaking or highly flexible forms. This
is more of a problem with high bleed concrete particularly in
winter when the cooler temperatures provide longer time to
initial set and therefore a higher amount of bleed (Fig.a)
Fig a Drying Shrinkage Cracks in slab

8. 4.Concrete Crazing:
 Crazing is the development of a network of fine random cracks
or fissures on the surface of concrete caused by shrinkage of the
surface layer. These cracks are rarely more than 3mm deep, and
are more noticeable on over floated or steel-troweled surfaces.
The irregular hexagonal areas enclosed by the cracks are
typically no more than 40mm wide and may be as small as 10mm
in unusual instances (Fig a & b).
Fig a, Crazing Fig b, Crazing pattern

9. 5.Steel Corrosion induced Cracking:
 Corrosion of the steel produces iron oxides and
hydroxides, which have a volume much greater than
the volume of the original metallic iron. This increase
in volume causes high radial bursting stresses around
reinforcing bars and results in local radial cracks.
Fig, Corrosion Induced Cracking

10. 1. EPOXY INJECTION
2. CRACK STITCHING
3. SEALING OF CRACKS
4. PROVIDING ADDITIONAL REINFORCEMENT
5. COLUMN JACKETING
6. BEAM JACKETING
CRACK REPAIR METHODS

11. 1.EPOXY INJECTION:
PURPOSE: To provide guidance on use of epoxy injection
to repair cracks in concrete.
DESCRIPTION: This method can be used to repair cracks as
narrow as 0.002 in. The method generally consists of
drilling holes at close intervals along the cracks, in some
cases installing entry ports, and injecting the epoxy under
pressure. For massive structures, an alternative procedure
consists of drilling a series of holes, usually 7/8 in. in
diameter, that intercept the crack at a number of locations.
Typically, holes are spaced at 5-ft intervals
EQUIPMENT, TOOLS, AND PERSONNEL REQUIREMENTS: A
concrete drill, an epoxy injection system, a means of
cleaning holes and cracks, and normal hand tools are
required. One man can repair cracks using this method, but
a two- or three-man operation is more efficient. Epoxy
injection requires personnel with a high degree of skill for
satisfactory execution.

12. Epoxy injection fig

13.  Masonry structures can be sealed effectively with less cost by using
grout provided the cement-base stabilizing mixture contains an
intrusion aid.
 The consistency of intrusion mixture is that of smooth slurry.
 Before the intrusion, grout is pumped , the holes are tested by
pumping water to see the drilling is adequate and to determine
correct consistency for the slurry repairs.
 Firstly plaster is removed near the crack from inside and outside of
wall and clean the crack thoroughly with inject and water.
 Wet the crack , if dry ,by sprinkling water.
 This mixture is pumped into holes previously drilled at various
interval to various depth without damaging the integrity of
structure.
 Pumping the grout simultaneously into multiple series of holes
ensures good penetration into any fissures within the structure
and for making masonry structures watertight
Grouting(cement mortar):

14.  Chemical grouts consist of solution of two or more
chemicals (such as urethanes, sodium silicate) that
react to form a gel. This grout opposed to cement
grouts that consist of suspension of solid particles in a
fluid.
 Advantages of chemical grout include applicability in
moist environment and their ability to be applied in
very fine facture.
 Disadvantage is high degree of skill needed for
satisfactory use and their lack of strength.
 Crack as narrow as 0.05 mm can been filled with
chemical grout.
Grouting (chemical):

15. BEFORE AFTER

16.  This method involves drilling holes on both sides of
crack and grouting in stitching dogs.
 Stitching may be used when the tensile strength must
be re-established across major cracks.
 Stitching a crack tends to stiffen the structure,
causing the concrete to crack elsewhere. therefore it
may be to strengthen the adjacent section with
external reinforcement
CRACK STITCHING:

18.  In concrete structure repairing of cracks is very
important.
 Because it reflects the harmful gases entering the
concrete.
 Before sealing the cracks its length side is made wide.
 Which is known as routing.
SEALING OF CRACKS

19. After routing
cracks is sealed by
using cement.
Before pasting
cement the edge
should be clean
and the edge
should be dry.

20. 1. Cement slurry
2. Cement mortar
3. Epoxy resins
4. Poly vinyl acetate
5. Polymer resins
6. Acrylics
7. Fibber
8. Parma bond(bonding agent)
9. Parma master bond-base(epoxy concrete bonding agent)
10. Parma crack fill(crack repair)
Crack repair Material

21. Causes of cracks at junction of masonry and
concrete
 Temperature Changes
 Final setting time of cement is 600min.as this time
 Fine cement and fine aggregate
 Increased W/C ratio
 Failure to resist tension
 Poor Workmanship
 Inadequate structural supports
CASE STUDY
cracks at junction of masonry and
concrete

22. 1. Temperature Changes
Temperature change is a major cause of cracks in
large concrete applications. This is because of the
temperature variations between concrete that is
poured first and subsequent layers of concrete. These
temperature variations can cause some portions of
the slab to expand while others are shrinking, which
leads to cracks. The more extreme the difference in
temperature, the more dramatic and deep the
cracking will be.

23. 2.FINAL SETTING TIME OF CEMENT
IS 600MIN.AS SOON AS THIS TIME :
 Curing is required to meet with the hydration
temperature during setting of cement. But in High
strength concretes like M50 or more there will be
minor cracks on the surface. To avoid this
immediately sprinkle (spray) the water on the surface
even within half an hour of casting, So that this
immediate cracks can be avoided.

24. 3. Increased W/C ratio
 Increase in water content and less cement content
will allow Bleeding. And hence the accumulated
water will lead to....
 But exactly i think the gases such as CO2, SO2, SO3,
etc. from atmosphere react with the water and
initially making it ACIDIC and then used for mixing
mortar ultimately results in CRACKS.
 In other words also shrinkage, creep, modulus of
elasticity, etc. many other factors lead to formation of
CRACKS

25. 4. Failure to resist tension
 Concrete by character is to crack when
there is unadjusted tension. However
out of other reasons, a rich cement,
poor detailing of reinforcement,
inadequate cover to reinforcement,
variable load conditions etc. also
responsible for cracking of concrete.

26. 5.Poor Workmanship
 There are many reasons why concrete cracks....my
experience shows that the major reasons are poor
curing, imbalanced water cement ratio, poor
compacting of concrete, water used for concrete mix,
leaving steel elements like binding wires, nails, links
exposed, using rusted steel.......yes and other material
characteristics... different contraction and expansion
values.

27. Recron 3s method
Role of Recron 3s Controls cracking
Recron 3S prevents the micro shrinkage cracks developed
during hydration, making the structure/plaster/component
inherently stronger. Further, when the loads imposed on
concrete approach that of failure, Cracks will propagate,
sometimes rapidly. Addition of Recron 3 s to concrete and
plaster arrests cracking caused by volume change (expansion
and contraction), simply because 1 kg of Recron 3s offers
millions of fibres which support mortar/concrete in all
directions.
Method for repair cracks at junction of
masonry and concrete

28.  Concrete:
Use 12mm Recron 3s @ 900 gms/cubic meter.
 Plaster:
Use 6mm recron 3s @ 125 gms/bag of cement of 50 kgs.
In 1:4 cement send ratio. Dosage rate can be altered as
per requirement.
DOSAGE RATE:

29. Applications
 Recron 3s fibres can be used in concrete elements
such as RC and PC lintel, beam, column, flooring and
wall plastering; foundations, tanks, manhole cover
and tiles; plastering; roads and pavements; hollow
blocks and precasts.

30.  MIXER:
Sprinkle Recron 3s in the rotating site mixer with 2-
3liters of water/add chips/sand/cement and balance
water and rotate as usual.
 MANUAI MIXING:
For best results, use one pouch of Recron 3s (appx 100
gms) with one bag of cement. Empty content of pouch
in a bucket (15litres) of water and mix well. Pour
content of the bucket in the pond of cement and sand
and mix thoroughly for few minutes.
Direction for use

32. Reliance recron 3s fibre

33. CHICKEN MESH PLASTER
1) METAL MESH
TECHNICAL DATA:
 Width: 700 mm
 Length: 2500 mm
 Pack Quantity: 1 Pk.
 Material: Galvanized Steel
 Size: 2500 x 700 mm
 Type: Metal Mesh

34. Fiberglass mesh

35.  First of all this technique is used in cracks between
column and masonry.
 Above these it is also used in cracks between
homogenous material.
Use for chicken mesh plaster:

36.  First of all the surface of the wall should be made clean.
And then water is sprayed on wall. Then the height from
plinth to slab is measured and then chicken mesh of that
size is being cut and then chicken mesh is kept on wall and
then keeping washer and then chicken mesh is filleted by
bolt. If necessary then for bolt should be provided and
then water of cement is being prepared and the water is
being sprayed on the wall. So that the strength between
wall and plaster should be strong and then plaster work is
done on the wall by skilled mason. That plaster should
always be done of double coat. In this way plaster is done
than the cracks between walls and columns can be
stopped and then the life span of structure is also
increased.
HOW TO USE:

37. CHICKEN MESH PLASTER SITE PHOTOS

40.  In our project we studied different types of cracks
in construction work, its causes and remedial
measures.
 We carried out case study on cracks occurs
between masonry and concrete work and find out
field solution to minimise this type of cracks.
CONCLUSION