Amit Payal

1. GENRAL BUILDING CRACKS
(CAUSES AND PREVENTIVE MEASURES)
Bhagwati Prasad Paliwal (TS)
WCL- Ajmer

2. ❖ Occurrence of various crack patterns in the building during
construction, after completion when it is subjected to super
imposed load or during
phenomenon.
the service life, is a common
❖ A building component develops cracks whenever the stress
in
the components exceeds its strength.
❖ Stress in the building component could be caused
by externally applied forces, such as dead, live, wind or
seismic loads, foundation settlement etc.
OR
❖ it could be induced internally due to thermal
movements, moisture changes, elastic deformation, chemical
action etc.
Preamble :- Cracks in Buildings

3. Cracks in buildings could be broadly classified as structural and non-structural
cracks:-
❖Structural Cracks : These occur due to incorrect design, faulty construction or
overloading and these may endanger the safety of a building. e.g. Extensive cracking of an RCC
beam.
❖Non structural Cracks: These are mostly due to internally induced stresses in buildings
materials and do not endanger safety of a building but may look unsightly, or may create an
impression of faulty work or may give a feeling of instability. In some situations due to
penetration of moisture through them non structural cracks may spoil the internal finishes
thus adding to the cost of maintenance, or corrode the reinforcement, thereby adversely
affecting the stability of the Structure in long run. e.g. Vertical crack in a long compound
wall due to shrinkage or thermal movement.
Cracks may appreciably vary in width from very thin hair crack barely visible to naked
eye to gaping crack. Depending upon the crack width cracks are classified as :-
❖Thin Crack - less than 1 mm in width,
❖Medium Crack - 1 to 2 mm in width,
❖Wide Crack - more than 2 mm in width.
❖Crazing - Occurrence of closely spaced fine cracks at the surface of a material is called
crazing.
Classification of Cracks in Building

4. The measures for prevention of cracks could be broadly grouped under the
following main sub heads:-
➢Selection of materials: - Good quality of building materials according to the
specification if used that will minimize the cracks in the building.
➢Specifications for mortar and concrete:- The ratio of the mortar and
concrete should be according to the prescribed design. Care should be taken
that the coarse aggregate, fine aggregate should be free from silt suspended
impurities and the mix should be homogeneous, well mixed and contain no
excessive of water.
➢Drawing and Design of the building: - While doing the construction work
care should be taken that foundation of the building should not be laid on
loose
/muddy soil. The mortar, M S steel reinforcement should be according to the
design.
➢Good Construction practices: - It is necessary that work proceed uniformly
in all part of building. The workmanship should be according to the prescribed
norms and best practice in the building construction.
➢Weather Effect: - The construction work should be avoided in very hot and
dry weather, and during very low temperature also.
GENERAL MEASURES FOR PREVENTION OF CRACKS

5. TYPES OF CRACKS AND REMEDIES
❖ Cracks in building are a common occurrence and it is important to
understand the causes and the measures to be taken for their
prevention. Materials such as bricks, mortar and concrete, which
contain considerable quantity of water at the time of construction, dry
out subsequently and under go major contraction.
❖ In general quality of water, sand, Bajri, mixing of mortar, quantity of
water in mix, socking of bricks and workmanship have great effect on
construction work. If possible the subsequent items of construction
should be done after the drying of work previously done.

6. CAUSES :-
1)Differential settlement of foundation.
2)Shrinkage of clayey soil below foundation.
some time it happens from the absorption of
moisture by the tree roots in the vicinity.
PREVENTIVE MEASURES :-
1)Building should be constructed over soil
strata have in uniform characteristics.
2)Adequate plinth protection and drainage
arrangements should be made around the
building to minimize water entry in the
foundation.
3)Avoid construction of walls on filled up soil
4)Do not let trees grow too close to buildings
and compound wall specially if the soil happen
to be shrinkage soil/clay.
Diagonal cracks in bricks wall

7. Causes :-
❖Do not leaving expansion/contraction
joints at proper interval, in cold weather
when the wall tense to contract due to
temperature drop but being not allowed
to contract freely. It develops tensile
stress and when the tensile stress
exceeds the strength, the wall cracks.
Similarly in hot weather wall tends to
expend and if expansion is not allowed to
occur freely compressive stresses will
develop in the wall and when they exceed
the strength, wall will break.
PREVENTIVE MEASURES :-
❖Leave expansion/contraction joints at
regular interval specially in long stresses
of wall.
Vertical cracks in long compound wall:-

8. Causes :-
❖Absence of slip joints between RCC slab
and wall does not allow RCC slab to move
freely over wall and leads to cracking in the
wall. Some times the movement of the slab
may also cause cracking in masonry at lintel
and window sill level because here is the
masonry is weak. These cracks are
observed mainly on the top most story of
the building because roof is more exposed
to temperature variation.
PREVENTIVE MEASURES:-
❖Before casting RCC slabs over brick wall,
smooth bearing plaster should be done over
brick walls coupled with white wash /
bitumen coating over it. It allowed slab to
move freely over wall.
Cracks in load bearing masonry wall below
RCC slab

9. CAUSES :-
❖An instant of very frequent occurrences of thermal cracks in building is the formation of
horizontal cracks at the sport of a brick parapet wall. Factors which contribute to this type of
cracking are :-
1)Thermal coefficient of concrete is twice that of brick work and thus differential expansion and
contraction causes a horizontal shear stress at the junction of the two materials.
2)Drying shrinkage of concrete is three to four time that of brick masonry.
3)Parapet are generally built of concrete slab before the latter has undergone its drying
shrinkage fully. Parapet or railing does not have much self weight to resist horizontal shear force
at it sports
4)Caused by differential thermal movement and differential drying shrinkage.
PREVENTIVE MEASURES :-
❖Construction of masonry over the slab should be deferred as much as possible ( at least one
month ) so that concrete under goes some drying shrinkage prior to construction of parapet.
Mortar of parapet masonry should be rich and a good bond should be ensured between masonry
and concrete. Plastering on masonry and RCC work should be deferred as much as possible and
made discontinuous at the junction by Providing V groove in plaster. This way the cracks if occur
, will get concealed behind the groove and not be conspicuous. In case of iron railing, cracks
could be avoided by substituting the brick work with a RCC wall, sporting RCC railing.
Formation of Horizontal cracks at the base of
parapet wall

10. PICTURE of Horizontal cracks at the base of
parapet wall

11. Causes:-
❖Improper bonding of cross walls with main
walls by not leaving proper keys in the main
wall.
PREVENTIVE MEASURES:-
❖Main and cross walls should be properly
bonded by proper toothing.
Vertical cracks at junction of main wall and
cross walls

12. CAUSES :-
❖Panels wall are built very tightly to the RCC beams so that RCC beams are not free to deflect,
load is transmitted to the wall and vertical and horizontal cracks are produced in the wall
depending upon the direction in which wall is more slender ( i.e. Along height or length)
PREVENTIVE MEASURES :-
❖Some gap should be left between top of panel wall and bottom of the beam/slab so that
beam can deflect freely. This gap can be filled by weak mortar. If lateral support is required to
be given to wall beam/slab then some special lateral connections can be made in such a way
that free deflection of beam is not hindered in vertical direction.
Vertical and horizontal cracks in panel walls in
RCC framed structure

13. CAUSES :-
❖Cracks are due to deflection of slab and
lifting up of edge of the slab. Cracks are
mostly confined to the top most story
because of light vertical load of parapet
wall on slab due to which end of the slab
lifts. These cracks normally occur in roof
slabs of large span.
PREVENTIVE MEASURES :-
❖Bearing plaster should be done on top
of wall below RCC slab with a coat of
white wash or bitumen.
❖Avoid large spans of roof slab , if
possible provide beams to reduce the
length of the slab.
Horizontal cracks in the top most story
below slab

14. CAUSES :-
❖When RCC frame moves/deflects due
to loads, temp, variation etc. it causes
diagonal cracks in walls which are
located parallel to the movement.
PREVENTIVE MEASURES :-
❖Walls should not be build tightly to
the columns. For taking lateral
supports from column, special
connections should be made between
wall and column which provide lateral
supports to wall but does not tie it too
tightly to the column.
Diagonal cracks in panel walls in RCC
framed structure

15. CAUSES :-
❖These cracks are caused due to vertical shear
caused by differential strain in the lightly loaded
masonry below the opening and heavily loaded
portion of wall having no opening.
PREVENTIVE MEASURES :-
❖Too much disparity in stress in different walls
or parts of a wall should be avoided.
❖Portion of wall acting as pillars and having too
much concentrated loads should be replaced by
RCC pillars., if possible.
Vertical cracks below openings in line with
window jambs

16. CAUSES :-
❖Due to sulphate action in base concrete. Due
to expansion of clayey soil below by absorbing
moisture.
PREVENTIVE MEASURES :-
❖Take all measures to prevent contact of
sulphates with cement or use sulphate
resistant cement.
❖If clayey soil exists below building, measures
should be taken to prevent water entry under
the ground by constructing suitable plinth
protection and drains etc.
Cracking due to arching and up heaving of a
floor

17. CAUSES :-
❖Due to not leaving
expansion joints wall &
coping.
PREVENTIVE MEASURES :-
❖Leave proper expansion
joints in walls. Avoid long
stretches of wall
Arching up and cracking of coping above
retaining/boundary wall

18. Cracks in Concrete structures
Why Cracks Form in Concrete Structures
❖Concrete provides structures with strength, rigidity, and resilience
from deformation. These characteristics, however, result in concrete
structures lacking the flexibility to move in response to environmental
or volume changes.
❖Cracking is usually the first sign of distress in concrete. It is, however,
possible for deterioration to exist before cracks appear.
❖Cracking can occur in both hardened and fresh, or plastic, concrete
as a result of volume changes and repeated loading.
❖This involves tensile stresses being loaded onto the concrete, the
cracks occurring when the force exceeds its maximum tensile strength.

19. Causes of Cracks in Concrete
Causes of cracks in concrete can be many summarized as..
➢Concrete expands and shrinks due to temperature differences.
➢Settlement of structure.
➢Due to heavy load applied.
➢Due to loss of water from concrete surface shrinkage occurs.
➢Insufficient vibration at the time of laying the concrete.
➢Improper cover provided during concreting.
➢High water cement ratio to make the concrete workable.
➢Due to corrosion of reinforcement steel.
➢Many admixtures with rapid setting and strength gain performance have
an increased shrinkage potential.

20. Types of Cracks in Concrete

21. Concrete cracks
❖Control Joints: Since concrete tends to crack as it shrinks, control joints are sometimes
cut into the slab within a few hours after the concrete is finished to create a "weakened
plane".
Since concrete cracks generally occur at the weakest point (or the point of greatest stress)
this cut in weakened plane "tells" the concrete where to crack, and helps to avoid (as
much as possible) unsightly random cracking.
❖Random Cracks: These meandering, sometimes linear cracks are generally caused by
normal shrinkage (where control joints should have been placed).
If the random crack varies in width or is wider than 1/16", check to determine if the crack
could be the result of settlement, or dynamic movement.
❖Settlement Cracks: If the slab is not level on both sides of a crack, settlement is usually
the cause. This is a situation in which no tile should even be considered until the cause of
the settlement is discovered and corrected. Once the slab is stabilized, it should be leveled
using a sand/cement leveling material before using Torque Lock.
❖Heaving Cracks: A serious situation where the concrete is at a different elevation on
either side of the crack. As in settlement cracks, this condition must be corrected
immediately! Once the slab is stabilized, it should be leveled using a sand/cement leveling
material before applying Torque Lock.

22. Concrete cracks
Plastic Shrinkage Cracks :-
❖As the concrete’s heavier particles settle due to gravity, they push the water
and lighter particles toward the surface. This is called bleeding. If you fail to
monitor the temperature, wind, and humidity conditions properly the
evaporation rate of the surface water may exceed the bleed rate, drying out the
concrete’s superficial layer and therefore shrinking it due to dehydration. The
concrete beneath the surface layer is still well hydrated, however, and maintains
its volume. This applies to oppose tensile forces to the lower part of the drying
concrete on the surface, causing a cracked concrete profile.

23. Concrete cracks
Plastic Settlement cracks :-
➢The settlement process is a major factor in concrete strength development. As
the concrete bleeds, the water works its way to the surface. Sedimentation
then occurs as the aggregate and cement move downwards under the force of
gravity. This separation forms a weaker layer of the concrete near the surface.
If steel reinforcing bars are close to the surface and insufficiently covered with
concrete, the concrete bends back around the restraint and cracks at the apex.

24. Concrete cracks
Drying Shrinkage Cracks -
This is the main cause of cracking in hardened concrete. This cracking
takes place near the restraints due to volume changes in the concrete.
When concrete is exposed to moisture it swells and when it is exposed
to air with relatively low humidity it shrinks. If the shrinkage could
occur without the use of rebar no cracking would result, but in most
cases, the requirements of structural support make this impossible.

25. Concrete cracks
Thermal Stresses :-
Volume differentials are likely to develop in the concrete when different
temperatures occur across a concrete section. The concrete then cracks
when the tensile stresses imposed by a change in volume differential
exceed that of its tensile strength. Thermal stresses usually cause
cracking in mass concrete structures, the main cause of the
temperature differentials being the influence of the heat of hydration on
volume change.

26. Concrete cracks
Cracks due to Corrosion of Steel Reinforcement :-
Three conditions must be present for metals to corrode. These are
oxygen, moisture, and an electron flow within the metal.
Corroding reinforcement steel produces iron oxides and hydroxides as
by-products. As these form on the steelworks surface its volume
increases.
This increase in volume increases the pressure on the concrete and
causes radial cracking as the concrete fails under the tensile stresses.

27. Preventive Measures to avoid
Cracks in Concrete
How to Prevent Cracks in Concrete Structures.
➢ Reduce Water Content in Concrete.
➢ Proper Concrete Mix Design and use of Quality Materials.
➢ Proper finishing of Concrete Surface.
➢ Proper Curing of Concrete.
➢ Proper Placement and Vibration of Concrete.
➢ Proper Compaction of Soil to Prevent Settlement Cracks in Concrete.
➢ Providing Control Joints in Concrete.