crack and their preventive measure

1. IS THAT CRACK SERIOUS?
• Simplest questions to ask.
• One of the most difficult to answer.
• Prof. Mealcom Hollis-”Surveying buildings is an
art, verifying the cause of failure is a science”

2. Cracks:---
these are the defects in the
construction.
• Due to movement of ground.
• Temperature variation
• Moisture changes
• Chemical reaction
• Creep & elastic deformation
• Vegetation.

3. Classification of Cracks
Structural crack Non structural crack
Incorrect design
Faulty construction
Overloading
Internal induced stress in
building material

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• Non Structural Crack
Penetration of moisture through crack
Weathering action
Result in corrosion of reinforcement
Structure become unsafe (structural crack)

5. Classification of cracks
(Based on width)
Type Width
Thin
Medium
Wide
< 1 mm
1-2 mm
> 2 mm

6. Common sight of crack
Vertical
Horizontal
Diagonal
Straight
Toothed
Stepped
Map pattern
Random
Uniform
throughout
Narrow at one
end and gradually
widening at the
other

7. Internal stress in Building
component
• Compressive
• Tensile
• Shear
• Building material
• 1. Masonry, Concrete, Mortar
2. Weak in tension/shear
3. Causing tension/shear crack

8. Present trend in construction
• Modern Structure
- Tall, slender, thin wall
- Designed for higher stress
- Constructed at fast pace
• More crack prone

9. Cause of cracks in buildings
• Movement of ground and settlement of soil
• Moisture changes
• Temp. variation
• Elastic deformation
• Creep
• Chemical reaction
• Vegetation

10. Moisture Movement
• Reversible Movement
- Material expands on absorbing moisture
content
- Shrinks on drying
• Irreversible movement
- Material undergo some irreversible movement
due to initial moisture change

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15. Some measures to avoid cracks

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32. Foundation settlement…

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34. Crack due to vegetation…

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38. Identification of cracks:
• Careful study of location, width, depth-diagnosis
• Observation –stable or temp.
• Detection of change of width of cracks due to
temp.---telltales.
• Glass piece of flat glass is spanned a/c & tuck to
the wall at ends with mortar.
• If crack widens it is shown by glass
• If shortens then glass will cracks.
• Check-super facial /deep.
• Fine wire is used to measure the depth.

39. Repairs of cracks:
A) Gunting:
• Cleaning of cracks
• Filling with thick paste.
• Inverted “v” Groove” 10 mm
• Mortar of 1:2

40. B) Grouting:
C) Use of epoxy /polyepoxides.

42. Types and causes of cracks in
Concrete
• Before hardening
Drying
- Plastic shrinkage
- Settlement shrinkage
- Bleeding
- Delayed curing

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Constructional
- Formwork movement
- Excess vibration
- Subgrade settlement
- Finishing
Early frost damage

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• After hardening
 Unsound material
 Long term drying shrinkage
 Thermal
 Moisture movement
 Biological
 Structural design deficiencies
 Chemical
 Corrosion of reinforcement

45. Constructional Effects
• Crack/Deformation of plastic concrete (After
Compaction)
-Lack of rigidity of formwork (Remains unnoticed)
-Use of high consistency concrete (present trend)
: Pumping requirement, Use of superplasticizer
-Avoid segregation by proper vibration
• Segregated Concrete Mix- Exhibits high
shrinkage crack

46. Thanks…..