Cracks in Concrete

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Cracks in Concrete
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Cracks in Concrete
1-lntroduction
2-Classifications
3-Concrete removal, preparation 4-References
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1-lntroduction
the concrete cracks are caused due to many
reasons as repeated thermal cycle, accidental
overloading, drying shrinkage, inadequate design
or construction, or some other causes . This
seminar is to provide guidance on classification
of concrete cracks and discusses removal of the
existing concrete ,preparation of concrete
surface to receive repair materials and methods
for repairing the reinforcement bars .
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2-Classifications
2-1 SHRINKAGE CRACKS. 2-2 CRACKS DUE TO
CARBONATION OF CONCRETE. 2-3 CRACKS IN
REINFORCED SLABS. 2-4 CRACKS IN BEAMS. 2-5
CRACKS IN COLOUMNS. 2-6 CRACKS IN REINFORCED
WALL . 2-7 CRACKS DUE TO STRUCTURAL PROBLEMS.
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2-Classifications
2-1 SHRINKAGE CRACKS.
Common crack is shown widely in walls and slabs
so must put joint every 12 m , And for cover of
reinforcement bars when it is more than 4 cm or
less than 1 cm so must put mesh of wires and
improve the mix.
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2-Classifications
2-2 CRACKS DUE TO CARBONATION OF CONCRETE.
Especially in coastal area the carbonation of
concrete allows humidity to reach to the bars
then corrosion will occur. So must make cover of
bars more than 4 cm and paint the concrete and
improve the mix.
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2-Classifications
2-3 CRACKS IN BEAMS.
2-3-1 thermal Cracks As vertical cracks
through total height of beam and same thickness
and in L/5 of beam near support
2-3-2 Bending Cracks These cracks exist in
maximum moment zones at middle of span and at
support
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2-Classifications
2-3 CRACKS IN BEAMS.
2-3-3 shear Cracks Cracks at 45 with horizontal
axis (diagonal tension ) Reason shear
reinforcement is less than required.
2-3-4 Torsion Cracks Continuous Cracks at 45
with horizontal axis (diagonal tension )
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2-Classifications
2-4 CRACKS IN COLOUMNS.
2-4-1 Bending Cracks These cracks exist in
maximum moment zones
2-4-2 Cracks due to stirrups Vertical Cracks
Reason lateral tension
2-4-3 Cracks due to settlement Horizontal
Cracks Reason tension force because
Horizontal or vertical movement Of foundation.
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2-Classifications
2-5 CRACKS IN REINFORCED SLABS.
Reason the reinforcement bars is less than
required .
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2-Classifications
2-6 CRACKS IN REINFORCED WALL .
2-6-1 Bending Cracks These cracks exist in
maximum moment zones when wall does as beam
2-6-2 shear Cracks Cracks at 45 with horizontal
axis (diagonal tension )
2-6-3 Cracks due to weight Horizontal Cracks
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2-Classifications
2-7 CRACKS due to structural problems .
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3-Concrete removal, preparation 3.1-Surface
preparation
Methods of surface preparation-Typical methods
a) Chemical cleaning. In most cases chemical
cleaning methods of surface preparation are not
appropriate for use with the Concrete repair
materials. However, with certain coatings under
certain conditions, it may be possible to use
detergents, phosphate, and various proprietary
concrete cleaners. it is important that all
traces of the cleaning agent be removed after the
contaminating material is removed. b) Acid
etching. Acid etching of concrete surfaces has
long been used to remove laitance and normal
amounts of dirt. The acid will remove enough
cement paste to provide a roughened surface
which will improve the bond of replacement
materials. c) Mechanical preparation. This
technique consists of mechanically removing thin
layers of surface concrete using such equipment
as impacting tools (breakers. scabblers),
grinders, and scarifier. Depending on the
equipment used, a variety of surfaces may be
obtained. d) Abrasive preparation. This technique
consists of removing thin layers of surface
concrete using abrasive equipment such as
sandblasters, shotblasters, or high pressure
water blasters.
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3-Concrete removal, preparation 3.1-surface
preparation 3.2-Reinforcement repair
3.2.1 Removal of concrete surrounding
steel removal of the deteriorated concrete
surrounding the reinforcement. 3.2.2 Quantity to
remove. All weak, damaged and easily removable
concrete should be chipped away. 3.2.3Inspection
of reinforcing steel steel is capable of
performing as intended by the designer. 3.2.4
Cleaning of reinforcement steel .
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4-References
1-CONCRETE REPAIR MANUAL VOLUME1
.ACI,ICRI,BRE,CS. 2003 USA 2-DETERIORATION
AND REPAIR OF REINFORCED CONCRETE IN THE ARABIAN
GULF VOLUME1
1989. Bahrain 3-CRACKS IN REINFORCED CONCRETE
STRUCTURES 1997 EYGPT 4-REASONS OF
BUILDINGS COLLAPSE
1999 EYGPT 5-STRUCTURAL EVALUATION
1998
SYRIA 6-REHABILITATION OF BUILDING
2000 SYRIA