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1. SHAHID ALI
CLASS No 53

2. TOPIC OF PRESENTATION:

3. INTRODUCTION: CRACKS
Cracks can be:
o Structural Cracks
o Non Structural Cracks

4. STRUCTURAL CRACKS:
refers to crack that developed at the core or
frame that form the foundation of the building
itself. Normally, any types of crack occurred
in this case is very dangerous and must be
dealt immediately.

5. PICTURES OF
STRUCTURAL CRACKS:

6. NON STRUCTURAL CRACKS:
as the name itself implies, refers to any parts
of the building that doesn’t belong to the
core or frame of the building for example
wall (except load bearing wall),driveway,
patio, and walkway. Cracks occurred in this
case are not that threatening if compared to
structural crack.

7. PICTURES OF
NON STRUCTURAL CRACKS:

8. CAUSES:
 Structural cracks
 due to incorrect design
 faulty construction
 Overloading
 Non Structural cracks
 Moisture changes
 Thermal movement
 Elastic deformation
 Creep
 Chemical reaction
 Foundation movement and settlement of soil
 Vegetation

9. NON STRUCTURAL CRACKS:
MOISTURE CHANGES:
Building materials expand on absorbing
moisture and shrink on drying. Shrinkage in
concrete or mortar depends on a number of
factors
 Cement concrete: Richer the mix , greater is
the drying shrinkage.
 Water content: More water in mix induces the
more it is to reduce, so greater is the shrinkage.
 Aggregates : Large aggregates with good
grading has less shrinkage for same workability
as less water is used

10.  Curing: If proper curing starts as soon as
initial set has taken place and continued
for 7 to 10 days shrinkage is comparatively
less
 Excessive fines: More fines in aggregate
requires more water for same workability
and hence more shrinkage.
 Temperature: Concrete made in hot
weather needs more water for same
workability hence results in more
shrinkage

11. PICTURES OF
MOISTURE CRACKS:

12. SOME MEASURES FOR CONTROLLING
SHRINKAGE
 Shrinkage cracks in masonry can be
minimized by avoiding use of rich cement
mortar and by delaying plastering till
masonry has dried after proper curing and
has undergone most of its initial shrinkage.

13. TEMPRATURE EXPENSION AND CONTRACTION:
Materials expand or contract when subjected
to changes in temperature. Most materials
expand when they are heated, and contract
when they are cooled. When free to deform,
concrete will expand or contract due to
fluctuations in temperature. The size of the
concrete structure whether it is a bridge, a
highway, or a building does not make it
immune to the effects of temperature.

14. PICTURE OF THERMAL VARIATION:

15. CONTROLLING OF THERMAL VARIATION:
Joints are the most effective way to control
cracking. If a sizable section of concrete is
not provided with properly spaced joints to
accommodate temperature movement, the
concrete will crack in a regular pattern
related to the temperature.

16. ELASTIC DEFORMATION:
When the walls are unevenly loaded, due to
variation in stresses in different parts of wall
the cracks are formed in walls. When two
materials having wide different elastic
properties are built together under the effect
of load, different shear stresses in these
materials create cracks at the junction

17. PICTURE OF ELASTIC DEFORMATION:

18. CHEMICAL REACTION:
 Chemical reactions in building materials
increase their volume and internal stress ,
causes cracks. The components of structure
also weaken due to chemical reactions. Some
common instances of chemical reactions are
following.
 Sulphates attack on cement products
 Carbonation in cement based materials
 Corrosion of reinforcement in concrete
 Alkali aggregate reaction

19. PICTURES OF CHEMICAL REACTION CRAKS:

20. CONTROLLING OF
CHEMICAL REATION CRACKS:
 If sulphates content in soil is more that 0.2 %
or in ground water more than 300 ppm use
rich mix of concrete and mortar has to be
adopted.
 Avoid bricks containing too much soluble
sulphates (more than 5 %) and use rich
mortar in such cases.
 Use expansion and control joint at closure
intervals

21. CREEP:
 deformation of structure under sustained
load. Basically, long term pressure or stress
on concrete can make it change shape. This
deformation usually occurs in the direction
the force is being applied. Like a concrete
column getting more compressed, or a beam
bending

22. PICTURES OF CREEP:

23. CONTROLLING OF
CREEP CRACKS:
 By using aggrigates having high modulus of
elasticity because It can be easily imagined that
the higher the modulus of elasticity the less is
the creep. Light weight aggregate shows
substantially higher creep than normal weight
aggregate.
 it can also be said that creep is inversely
proportional to the strength of concrete, so we
can reduce creep cracks by keeping
water/cement low.

24. VEGETATION:

The roots of trees located in the vicinity of a
wall can create cracks in walls due to growth
of roots under foundation. The cracks occur
in clay soil due to moisture contained by
roots.

25. PICTURE OF VEGETATION CRACKS:

26. CONTROLLING OF
VEGETATION CRACKS:
 Do not let trees grow too close to the
buildings, compound walls etc. Remove any
saplings of trees as soon as possible if they
start growing in or near of walls etc.

27. STRUCTURAL CRACKS:
Structural cracks mainly occur due to:
a) Defective design and defective load assumptions
and perception of behavior of the structure.
b) In correct assessment of bearing capacity of
foundation soil and soil properly.
c) Defective detailing of joints of components like
roof with brick wall corner joints of walls
d) Defective detailing of structural detailing of steel
reinforcement.
e) Lack of quality control during construction.

28. END OF THE PRESENTATION:
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