11. Distress in Structures
Structural Non-Structural
Caused by faulty design,
faulty construction and/or
overloading.
Endangers building safety.
Needs immediate attention.
Caused by internally induced
stresses in components
Looks unsightly
Indirectly leads to structural
weakening
12. Factors Causing distress
External Internal
Overloads due to dead load,
live load, wind load, seismic
loads, etc. which are not
accounted in the design.
Differential settlements in
the foundation.
Dimensional changes induced
by
moisture penetration
temperature changes
horizontal shifts of building
components
volume changes due to
chemical action
Weakness in tensile and shear
stresses
16. Possible causes of deterioration/defects
Pre-construction
stage
Construction
stage
Post-construction
stage
17. PRE-CONSTRUCTION STAGE
DEFECTS
Poor design
Poor design
detailing
Faulty design
estimations at
changes in sections
Faulty design of
rigid joints in
precast elements
Poor deflection
estimations
18. Leakage through joints
Inadequate drainage
Incompatibility of materials at
critical sections
Cracks due to unanticipated or
under-estimated stresses
Inefficient drainage slopes
Structural
collapse
20. CONSTRUCTION STAGE DEFECTS
Local settlement of subgrade
Swelling of formwork
Premature removal of shores
Setting shrinkage
Internal settlement of concrete
Vibrations
22. CONSTRUCTION STAGE DEFECTS
LOCALSETTLEMENTOF SUBGRADE
Pouring fresh concrete some-
times may cause subgrade
below it to compress or settle.
Uneven stresses thus created
cause cracks in the concrete.
Cracks of this sort are
cured while applying final
finish to the concrete.
24. CONSTRUCTION STAGE DEFECTS
SWELLING OF FORMWORK
• Formwork absorbs moisture from
concrete or the atmosphere, which
results in swelling of form.
• Crushing of wale in the formwork
also causes movements of forms
• These result in cracks in the
concrete while setting
• Coating of the formwork with
moisture resistant material.
• Using unyielding lateral ties with
good end anchorage
26. CONSTRUCTION STAGE DEFECTS
• Differential settlement between
the surface and the interior
volume of the concrete suspension
causes surface cracks.
• Concrete on the surface sets faster
than the interior suspension
• Surface cracks can be cured and
closed by delayed finishing.
• Curing of concrete must start
immediately after casting to delay
setting of the surface concrete.
• Good compaction will also help
prevent this defect.
III. INTERNAL SETTLEMENTOFCONCRETE
28. CONSTRUCTION STAGE DEFECTS
• While setting the concrete shrinks
giving rise to surfacial cracks
resembling the scales of the
alligator.
• Good and timely curing will help
avoid this type of damage.
IV. SETTING SHRINKAGE OF CONCRETE
30. CONSTRUCTION STAGE DEFECTS
• Premature removal of shores from
freshly poured concrete causes re-
distribution of stresses on
formwork, causing movements
and cracking of concrete.
• Shores must be removed only after
the concrete has gained sufficient
strength.
V. PREMATUREREMOVAL OF SHORES
31. CONSTRUCTION STAGE DEFECTS
VI. VIBRATIONS INDUCED DAMAGES
• Vibrations due to indiscreet
walking over concrete and
dumping construction materials,
etc., can also lead to cracking
• Workers have to be trained in
avoiding such carelessness
32. POST-CONSTRUCTION STAGE DEFECTS
Temperature Stresses
Corrosion of reinforcement
Overloading
Weathering action
Aggressive action of chemicals
Moisture effects
Natural disasters
Fire
33. POST-CONSTRUCTION STAGE DEFECTS
• Cracks in concrete can be
produced due to temperature
stresses due to:
i. Difference in temperature
inside and outside the
building
ii. Variation in the internal
temperature
• The finishing of the surface should
be such that it reflects solar
radiation and not absorbs it.
• Good concrete mix with low heat
of hydration
I. TEMPERATURESTRESSES
35. POST-CONSTRUCTION STAGE DEFECTS
• Corrosion of reinforcement
bars cab be due to:
i. Entry of moisture
through cracks
ii. Electrochemical action
• Seal the crack before it reaches the
reinforcement bar
• Protect against corrosive chemical
action by
i. Keeping structure clean
ii. Painting
iii. Prevent from absorbing moisture
iv. Provide bituminous or zinc
coatings.
v. Encase using fibre wrapping
systems
II. CORROSION OF REINFORCEMENT BARS
37. POST-CONSTRUCTION STAGE DEFECTS
• Sulphate attack
• Acid attack
• Actions of Salts
• Alkali-aggregate reactions
• In sulphate environment, the concrete
must be made of sulphate-resistant
cement. Bituminous coating can also
be provided
• In marine environment, C3A (tricalcium
aluminate) content must be less than
8%
• Use of limestone aggregate in acidic
environment is preferable
• Maximum alkali-content in cement
must be less than 0.6%
III. CHEMICALATTACK
39. POST-CONSTRUCTION STAGE DEFECTS
• Shock waves
o Shock waves could be
mechanical or thermal
o Concrete is
heterogeneous - different
constituents have
different wave
transmission rates
• Erosion
• Providing sufficient reinforcement is
said to an excellent resistance to shock
waves.
• Use of high-strength concrete
• Proper curing
• Proper finishing
IV. WEATHERINGACTION
