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

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

4. Continue… 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 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

43. Continue… Constructional Formwork movement Excess vibration
Subgrade settlement
Finishing
Early frost damage

44. Continue… 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…..