Cracks in Buildings

By M A Azeem

(10N01A0129)

Introduction• What is CRACK?

• Why crack occurs?

• Classification of CRACKS

Moisture Changes

• How cracks occur by moisture changes?

• Classification of materials based on

moisture movements

• Reversible movement

• Irreversible movement

Shrinkage

• What is shrinkage?

• Types of shrinkage

• Effects of shrinkage on concrete

• Factors affecting shrinkage

Shrinkage crack on:

slab external wall

Creep

• What is creep?

• Creep phenomenon

• Cracks due to creep in Load bearing structures Framed structures

Vertical cracks at junction of RCC column and wall masonry in a load bearing structure

Horizontal cracks in brick walls of a framed structure

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.

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.

Thermal Movement

• How cracks occur by thermal

movement?

• Parts of structure where thermal

cracks occur

• Factors causing thermal movement

Identification

In Framed structures In Load bearing structures

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.

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.

Settlement of soil

• Foundation movement

due to settlement of soil

Preventive and precautionary measuresCracks due to foundation settlement

Structural provision for horizontal extension with an expansion joint

Elastic Deformation

Diagonal cracks in brick wall

• Causes

• Preventive Measures

Cracks in load bearing masonry wall below RCC slab

• Causes

• Preventive Measures

Vertical formation of cracks at the base of parapet wall

• Causes

• Preventive Measures

Chemical Reaction

• Sulphate Attack

• Carbonation

• Corrosion of Reinforcement

• Alkali-aggregate Reaction

Cracks due to carbonation

Vegetation• Cracks in walls due to vegetation

• Cracks in foundation due to

vegetation

• Preventive measures of cracks

due to vegetation

Building cracks due to vegetation

CHECK LIST

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

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

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

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

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

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

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

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

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

Queries…

The End