Repair terminology / Causes of concrete
deterioration
07.09.2015
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
1
Outlines
• Applications of reinforced concrete
• Terminology
• Causes of distress and deterioration of concrete
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
2
Course content
Deterioration
Process
Initiating
Factors Causing
Deterioration
Intrinsic
Extrinsic
Chemical
Physical
Biological
Leads to
Cracking
Scaling
Spalling
Pop-ups
Delamination
etc.
Repair
Visible
Damage
Assessed
Principles for
repair and protection
Condition
evaluation
Condition
survey
Visual inspection
Non-Destructive Testing
Destructive Testing
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
3
Applications of reinforced
concrete
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
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Applications of reinforced concrete
• Residential and commercial structures:
Reinforced concrete is ideally suited for
the construction of floor and roof slabs,
columns and beams.
• Bridges of small, medium and long
spans
Car parking,
Kouvola, Finland
• Earth retaining structures includes
abutments for bridges and retaining
walls for earthen embankments
• Water retaining structures like ground
and overhead tanks and hydraulic
structures like gravity and arch dams.
• The concrete is widely used for the
construction of large domes for water
tanks and sports stadiums and
conference halls.
Residential houses, Espoo, Finland
http://www.elementtisuunnittelu.fi
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
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Applications of reinforced concrete
• Reinforced concrete grid floors
comprising beams and slabs are widely
used for covering large areas like
conference halls where column free
space is essential requirement.
• For aircraft hangers, reinforced
concrete shells comprising of thin
circular slabs and deep edge beams
provide an economical solution.
• In coastal areas where corrosion is
imminent for the construction of marine
structures like platform, quay walls,
watchtowers and lighthouses.
Otakaari 1 Lecture hall A
• Reinforced concrete poles have almost
replaced steel poles for power
transmissions.
• Tall towers for TV transmission
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
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Applications of reinforced concrete
• For heavy duty floors in factories,
reinforced concrete is ideally suited due
to its resistance to wear and tear and
improved durability.
• In NPP structures, reinforced concrete
is preferred to steel for pressure vessel
construction due to the superior
radiation absorption characteristics of
high strength and high-density
concrete.
• Reinforced concrete piles, both precast
and cast-in-situ have been in used for
foundations of structures of different
types like bridges and buildings.
Photo: Hannu Huovila / TVO
Olkiluoto 3 (OL3), an ultra-modern
European Pressurised-water Reactor
(EPR), designed and built by French
nuclear industry giant Areva NP
• Reinforced concrete is also used in the
construction of pavements for highways
and airport runways.
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
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Terminology
https://www.icri.org/GENERAL/RepairTerminology2010.pdf
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
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Terminology
Deterioration
Damage
• A worsening of condition with time,
• Physical disruption or change in
which may result in a progressive
the condition of a structure or its
reduction in the ability of the
components, brought about by
structure or its components to
external actions or influences.
perform some aspects of their
intended function.
• Typically occurs when the material Defects
is exposed the weather, water or
• Defects caused by:
other chemicals over an extended
o Wrong detailing or design
period of time
o Construction practices
o Faulty materials
Degradation
• May result in inadequate structural
capacity, premature deterioration
or aesthetic issues
• A worsening of condition with time,
usually resulting in damage.
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
9
Terminology
Crack
• a complete or incomplete separation
of concrete into two or more parts
produced by breaking or fracturing.
Spall
• a flake, detached from a larger mass
by the action of weather, by
pressure, or by expansion within the
larger mass
Delamination
• a separation along a plane parallel to
a surface
Scalling
• local flaking or peeling away of the
near-surface portion of hardened
concrete or mortar
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
10
Terminology
Condition assessment
Visual inspection
• Investigation and estimation of the
condition of a structure
• An evaluation procedure in which a
qualified investigator observes,
classifies, and documents
deterioration or distress on
exposed concrete surfaces
• Conclusions based on engineering
judgment about the condition of a
structure
• Typically, one of the first steps in
evaluation of a concrete structure.
Condition survey
• Quantitatively defining the physical
condition of a structure,
• By:
o Visual inspection
o non-destructive tests (NDT)
o Supplemented by sampling
and laboratory testing (DT)
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
11
Terminology
Non-destructive tests (NDT)
Destructive tests (DT)
• Techniques for evaluating exiting
concrete structures with regard to
their strength and durability apart
from assessment and control of
quality of hardened concrete
without or partial damage to the
concrete.
• The process of taking samples and
testing them at laboratory
• Destructive testing involves the
physical destruction of the sample
to evaluate its characteristics.
• Laboratory testing of field samples
for:
– Strength
– Chemical and physical
properties of the field samples
– Other tests relevant to the
defect condition
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
12
Causes of distress and
deterioration of concrete
Evaluation and repair of concrete structures
Chapter 3 - Causes of Distress and Deterioration of Concrete
http://www.pdhonline.org/courses/s136/s136_content.pdf
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
13
Causes of distress and deterioration of concrete
• Accidental Loadings
• Erosion
– Abrasion
– Cavitation
• Chemical Reactions
– Acid attack
– Aggressive-water attack
– Alkali-carbonate rock reaction
– Alkali-sllica reaction
– Miscellaneous chemical attack
– Sulfate attack
• Freezing and Thawing
• Settlement and Movement
• Shrinkage
– Plastic
– Drying
• Construction Errors
• Temperature Changes
– Internally generated
– Externally generated
– Fire
• Corrosion of Embedded Metals
• Design Errors
– Inadequate structural design
– Poor design details
• Weathering
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
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Accidental loadings
• Accidental loadings may be
characterized as short-duration,
one-time events such as:
– the impact of a barge against a
lock wall or
– an earthquake.
• Determination of whether
accidental loading caused damage
to the concrete will require
knowledge of the events preceding
discovery of the damage.
• Usually, damage caused by
accidental loading will be easy to
diagnose.
• These loadings can generate
stresses higher than the strength
of the concrete, resulting in
localized or general failure.
• Visual examination will usually
show spalling or cracking of
concrete which has been subjected
to accidental loadings.
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
15
Chemical reactions
Carbon dioxide (CO2)
• CO2 present in the atmosphere (in
proportions of around 0.3 % by
volume) reacts in the presence of
moisture with the hydrated cement
minerals (i.e. the agent usually
being the carbonic acid H2CO3)
• The extent of carbonation
depends on the permeability of
the concrete and on the
concentration of CO2 in the air.
• The penetration of CO2 beyond the
exposed surface of concrete is
extremely slow.
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
16
Chemical reactions
Aggression by sulphates
– Soluble sulphates in the
ground and in water are
calcium and sodium
– Sulphates reacts with the
hydrated calcium aluminates
(C-A-H) to form secondary
ettringite, which increases in
volume and causes
delamination, swelling,
cracking
http://www.mapei.com/public/CN/linedocument/degrado_cls-gb.pdf
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
17
Chemical reactions
Aggression by chloride
– Seawater or de-icing salts
– Once the chloride penetrates
into the concrete and reaches
the reinforcement rods, it
eliminates the passivating
ferrous oxide film on the rods
so that they are exposed to the
corrosion process
– Penetration time depends on:
o The concentration of
chlorides
o Permeability of the
concrete
o Relative humidity
o Concrete cover depth
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
18
Chemical reactions
Alkali-aggregates reaction
– Some types of aggregate
contain reactive silicon that
react with two alkalis contained
in the cement, potassium and
sodium
– This reaction forms a gel which
is highly expansive if exposed
to humidity, and the gel creates
forces which break the
concrete around the
aggregates.
http://www.mapei.com/public/CN/linedocument/degrado_cls-gb.pdf
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
19
Physical elements
Freezing and thawing
Temperature changes
• Water turns to ice, its initial volume
increases by 9%
• Temperature changes can affect
shrinkage.
• Damage due to freeze-thaw cycles
only occurs when there is a
combination of :
1) Low temperatures and
2) Absence of macro-porosity
• The heat of hydration of cement
in large placements can present
problems.
• Climatic conditions involving
heat also have the capability to
affect concrete.
• Fire damage can also contribute
to problems associated with
excessive heat.
• Concrete resists at up to 650°C.
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
20
Physical elements
Shrinkage and cracking
• Plastic and hygrometric shrinkage
• Plastic shrinkage occurs during the
plastic phase of concrete, when it
releases part of the humidity
contained within it into the
surrounding environment, causing
it to contract
• hygrometric shrinkage takes place
within the first six months of
casting
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
21
Aggression by mechanical elements
Abrasion:
–
If a material is repeatedly struck by
particles from a harder body, abrasion
takes place due to the friction
Impact:
–
Damage due to impact is not
necessarily immediately visible, and in
certain cases many impact cycles are
required
Abrasion
Erosion:
–
Erosion is a particular form of wear due
to wind, water or ice which provokes the
removal of material from the surface.
Cavitation:
–
–
Cavitation is a problem where flowing
water (> 12 m/s) is present.
The high speed of the water provoke
turbulence and areas of low pressure,
and vortexes will form which erode the
substrate
Cavitation
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
22
Weathering of concrete
The appearance of a concrete
surface is affected by a number of
tangible factors including:
• The amount of dirt deposited
• The uniformity or non uniformity of
the dirt deposits
• Color of the dirt in relation to the
color and surface texture of the
concrete
• Growth of lichen and moss and
other accretions on the concrete
surface
• Damage to the surface, including
crazing and cracking
http://www.concreteconstruction.net/Images/Weath
ering%20of%20Concrete_tcm45-342061.pdf
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
23
Design and construction errors
Examples of design mistakes:
Examples of construction errors:
• Poor design details
• Adding too much water to concrete
mixtures
• Sudden changes in section
• Poor alignment of formwork
• Insuf cient reinforcement at
corners and openings
• Improper location and installation
of reinforcing steel members
• Inadequate provision for de ection
and drainage
• Vibration of freshly placed concrete
• Incompatibility of materials
• Improper consolidation
• Neglect of creep effect
• Improper curing
• Rigid joints between precast units
• Movement of form work
• Unanticipated shear stresses in
piers, columns, or abutments
• Premature removal of supports
• Inadequate joint spacing in slabs
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
24
Summary
Lecture summary
– Applications of reinforced
concrete
– Concrete repair terminology
– Causes of deterioration in
buildings in general
Next lecture
• Deterioration mechanisms
i. Chemical degradation
• Corrosion (chloride &
carbonation)
• Alkali silica reaction
• Sulfate attack
ii. Physical degradation
• Freeze-thaw attack
iii. Biodegradation of structures
and materials
• Moisture problems
Rak-43.3301 Repair Methods of Structures I (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
25