The document discusses different types of cracks in concrete structures, their causes, and repair methods. It describes structural cracks as wider than 3mm and caused by poor construction practices or overloading. Non-structural cracks are thinner and caused by moisture, thermal movement, or vegetation. Various crack repair techniques are outlined, including epoxy injection to fill hairline cracks, routing and sealing, stitching with metal anchors, grouting, and applying an overlay. The conclusion states it is impossible to completely prevent cracks but their development can be minimized by considering construction materials and techniques.

1. PRESENTED BY :-
GAUTAM SWALA

2. Introduction
Principal causes of cracks
Repairing of cracks
Conclusion

3. A crack is a complete or incomplete separation of
concrete, brick walls into two or more parts produced
by breaking or fracturing.

4. 1. Structural Cracks
2. Non- Structural Cracks
1. Structural Cracks : Structural cracks are due to poor
construction sites ,overloading and poor soil
bearing.
• Generally wider than 3 mm.
• These cracks should be addressed immediately.
(A) Nature -wise:

5. 2. Non-Structural Cracks : These are caused by changes in
the moisture content and thermal movement. It
can also be caused by following conditions :
• Creep
• Vegetation/Trees
 Generally, less than 3 mm

6. (a) Thin Crack : Less than 1 mm in width
(b) Medium Crack : 1 to 2mm in width
(c) Wide Crack : More than 2 mm in width
(d) Crazing : Occurrence of closely spaced fine cracks
at the surface of material is called crazing.
(B) Width-wise:

7. (C) Shape-wise :
1.Straight 2.Toothed 3.Horizontal ,vertical &
Diagonal crack

8. 4.Stepped 5.Random

9. EXPOSURE CONDITIONS MAXIMUM ALLOWABLE CRACK
WIDTH IN MM
DRY AIR 0.41
HUMIDITY, MOIST AIR 0.30
WETTING AND DRYING 0.15
WATER RETAINING STRUCTURE 0.10

10. 1. Foundation Movement & Settlement of Soil
2. Faulty workmanship & poor construction practice
3. Elastic Deformation
4. Growth of Vegetation
5. Poor structural design & specifications
6. Temperature effect

11. Shear Cracks in buildings occurs when there is large
differential settlement of foundations due to one of the
following causes :
(a) Unequal bearing pressure under different parts of
structure.
(b) Bearing pressure being in excess of bearing
strength of soil.

12. (c) Low factor of safety in a design of foundations.
(d) Local variation in nature of supporting soil.

13. • Under reamed pile foundation.
• SBC is not exceeded.
• Soil should be well compacted.

14. Causes :
 Premature removal of forms.
 Cold joints.
 Segregation.
Selection of poor quality cheap materials

15. • Water Cement Ratio
• Proper Curing
• Support for forms
• Design recommendations

16. • Structural components of a building under elastic
deformation due to dead and superimposed live loads
in accordance with hook’s law.
• The amount of deformation depend upon elastic
modulus, magnitude of loading and dimension of
component.

17. Firstly, crack occurs on exterior walls due to above
causes.
Then, soil and some small seed is collected through
wind inside cracks which comes in contact with
moisture & finally led to the growth of vegetation.
If these plants are not removed well in time , they
cause severe cracking of walls.

18. 5.Poor structural design & specifications
 Firstly, It’s important to do soil investigations to
determine type of foundation
 It is critical for the structural designer and architect to
know whether the agency proposed to carry out
construction has the requisite skills and experience to
execute their design.

19. 6. Temperature Effect :
 Volume Changes.
 Volume relation to temperature is expressed by
coefficient of thermal expansion.
 Volume change induced stress.

20.  Adequate insulating or terracing treatment.
 Painting exterior walls with some sun reflective
finish
Introducing of expansion and contraction joints at
appropriate locations.

22. Repairing of Cracks
1. Epoxy injection
2. Routing and Sealing the crack
3. Stitching
4. Grouting
5. Overlay of cracks

23. 1.Epoxy injection
 Cracks as narrow as 0.05mm can be bonded by this
method
 Firstly, clean the surface with the wire brush
 Then , Establish entry and venting ports at close
intervals along the cracks
 Remaining exposed surface of cracks are sealed by
epoxy paste
 Now, inject epoxy under pressure
 Finally, hammer the ports & finish the surface to
grinder.

25. This method involves enlarging the cracks along its
expose face & filling & sealing it with a suitable joint
sealant.
This procedure is most applicable to approximately
flat surfaces such as floors & pavements.

26. 3. Stitching
• Firstly, drill holes on both sides, cleaning the holes.
• Then, anchoring the U-shaped metal units in the
holes with either a non-shrink grout or an epoxy resin.

27. This method is effective in stopping water leaks but it
will not structurally bond cracked sections.
Firstly, clean the concrete along the crack & then fill
it with portland cement grout.
Water cement ratio should be kept low to maximize
the strength & minimize shrinkage.

28. Slabs containing fine dormant cracks can be repaired
by applying an overlay, such as polymer modified
portland cement mortar, or by silica fume concrete.

29. It is impossible to guarantee against cracking yet
attempts can be made to minimize development of
cracks
Not all types of cracks require same level of
attention.
The causes of crack can be controlled if proper
consideration is given to construction material &
technique to used.
In case of existing cracks, after detail study & analysis
of crack parameters, most appropriate method of
correction should be adopted for effective & efficient
repair of crack.

30. THANK YOU