cracks in buildings
DESCRIPTION
Cracks in buildings are of common occurrence. A building component develops cracks whenever stress in the component exceeds its strength. Stress in a building component could be caused by externally applied forces, such as dead, live, wind or seismic loads, or foundation settlement or it could be induced internally due to thermal variations, moisture changes, chemical action, etc.TRANSCRIPT
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Cracks in Buildings
By M A Azeem
(10N01A0129)
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Introduction• What is CRACK?
• Why crack occurs?
• Classification of CRACKS
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Moisture Changes
• How cracks occur by moisture changes?
• Classification of materials based on
moisture movements
• Reversible movement
• Irreversible movement
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Shrinkage
• What is shrinkage?
• Types of shrinkage
• Effects of shrinkage on concrete
• Factors affecting shrinkage
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Shrinkage crack on:
slab external wall
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Creep
• What is creep?
• Creep phenomenon
• Cracks due to creep in Load bearing structures Framed structures
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Vertical cracks at junction of RCC column and wall masonry in a load bearing structure
Horizontal cracks in brick walls of a framed structure
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Preventive measures of shrinkage & creep cracks
• Shrinkage cracks in masonry could be minimized by avoiding the use of rich cement
mortar in masonry.
• This shrinkage cracks can also be minimized by delaying the plaster work till masonry
has dried after proper curing and has undergo most of its initial shrinkage.
• To minimize the shrinkage cracks in plastering mortar, plaster should not be richer.
• External walls of building are given on the outside finish of rich cement based material. In
such cases, in order to avoid shrinkage cracks the finish is divided into small panels of
dimensions varying between 0.5 to 1.0m by providing grooves of 8 to 10mm width in
both directions.
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Preventive measures of shrinkage & creep cracks
• An effective method of controlling shrinkage cracks is the provision of movement joints i.e.,
expansion, control and slip joints.
• Work done in cold weather will be less liable to shrinkage cracking than that done in hot weather.
• Use concrete which has low shrinkage and low slump.
• Do not adopt a very fast pace of construction.
• When RCC and brick work occur in combination and are to be plastered over allow sufficient time
at least one month before taking up plaster work. Also provide a groove in plaster at the junction
or fix a 10cm wide strip of metal mesh over the junction to act as reinforcement for the plaster.
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Thermal Movement
• How cracks occur by thermal
movement?
• Parts of structure where thermal
cracks occur
• Factors causing thermal movement
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Identification
In Framed structures In Load bearing structures
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Preventive and precautionary measures
• Concrete of slab should be of low shrinkage and low slump.
• Construction of masonry over the slab should be deferred as much as possible (at least
one month) so that concrete undergoes some drying shrinkage prior to the
construction of parapet.
• Wherever feasible, provision should be made in the design and construction of
structures for unrestrained movement parts, by introducing movement joints of
various types. Namely, expansion joints, control joints and slip joints.
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Preventive and precautionary measures
• Over roof slabs, a layer of some insulating material or some other material
having good heat insulation capacity, preferably along with a high reflectivity finish,
should be provided so as to reduce heat load on the roof slab.
• In case of massive concrete structures, rise in temperature due to heat of
hydration of cement should be controlled by using of low-heat cement, use of
pozzolanas, pre-cooling of aggregates and mixing water, post-cooling of concrete
by circulating refrigerated water through pipes embedded in the body of the concrete
etc.
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Settlement of soil
• Foundation movement
due to settlement of soil
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Preventive and precautionary measuresCracks due to foundation settlement
Structural provision for horizontal extension with an expansion joint
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Elastic Deformation
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Diagonal cracks in brick wall
• Causes
• Preventive Measures
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Cracks in load bearing masonry wall below RCC slab
• Causes
• Preventive Measures
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Vertical formation of cracks at the base of parapet wall
• Causes
• Preventive Measures
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Chemical Reaction
• Sulphate Attack
• Carbonation
• Corrosion of Reinforcement
• Alkali-aggregate Reaction
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Cracks due to carbonation
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Vegetation• Cracks in walls due to vegetation
• Cracks in foundation due to
vegetation
• Preventive measures of cracks
due to vegetation
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Building cracks due to vegetation
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CHECK LIST
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Moisture
S. No. DESCRIPTION AT THE SITE
1 Length f the crack 4 feet
2 Width of the crack 2 mm
3 Depth of the crack 1 mm
4 Direction Diagonal
5 Occurrence Slab
6 Conclusion Crack due to moisture
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Moisture
S. No. DESCRIPTION AT THE SITE
1 Length of the crack 6 feet 10 inches
2 Width of the crack 2 mm
3 Depth of the crack 1 mm
4 Direction Horizontal
5 Occurrence External wall
6 Conclusion Crack due to moisture
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Creep
S. No.
DESCRIPTION AT THE SITE
1 Length of the crack 9 feet 11 inches
2 Width of the crack 2 mm
3 Depth of the crack 2.5 mm
4 Direction Horizontal
5 Occurrence Internal wall
6 Conclusion Crack due to creep
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Creep
S. No.
DESCRIPTION AT THE SITE
1 Length of the crack 10 feet 2 Width of the crack 1.5mm3 Depth of the crack 1mm4 Direction Vertical5 Occurrence Junction of RCC column
and brick masonry6 Conclusion Crack due to creep
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Thermal Expansion
S.NO.
DISCRIPTION AT THE SITE
1. Age of crack 14 years2. Length of crack 16 feet 4 inches3. Width of crack 2 mm4. Depth of crack 2 mm5. Direction Horizontal6. Pattern Parallel to movement of
parapet wall7. Conclusion Crack due to thermal
expansion
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Foundation Movement
S.NO.
DISCRIPTION AT THE SITE
1. Age of crack 10 years2. Length of crack 8 feet3. Width of crack 2 mm4. Depth of crack 4 mm5. Direction Diagonal6. Pattern Wide at the top and narrow
at bottom7. Conclusion Crack due to foundation
movement
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Foundation Movement
S.NO.
DISCRIPTION AT THE SITE
1. Age of crack 10 years2. Length of crack 7 feet3. Width of crack >1 mm4. Depth of crack 2 mm5. Direction Vertical to Diagonal6. Pattern Wide at the top and narrow
at bottom7. Conclusion Crack due to foundation
movement
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Elastic Deformation
S.NO.
DESCRIPTION AT THE SITE
1 Length of the crack 6 feet 2 Width of the crack 2 mm3 Depth of the crack 1 mm4 Direction Diagonal5 Occurrence Joint between slab and
floor6 Conclusion Crack due to elastic
Deformation
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Elastic Deformation
S.NO.
DESCRIPTION AT THE SITE
1 Length of the crack 11feet 2 Width of the crack 3 mm3 Depth of the crack 2 mm4 Direction Diagonal5 Occurrence External wall6 Conclusion Crack due to Elastic
Deformation
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Queries…
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The End