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Prof. Mufid Samarai
Sharjah Research Academy
Sharjah, UAE
ASSESSMENT AND REPAIR OF BUILDING ANDBRIDGES
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PART ONE
The Concrete Equation
Deterioration of Concrete Structures
Durability Issues Effect of Materials
Deleterious Substances
Corrosion of Reinforcement Exercise
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Materials / Prof.Mufid Samarai
Raw Materials
Cement + Water+Fine Agg. +
Coarse Agg. +AdmixturesMixing + Transportation + Placing +
Finishing + Curing
Manufacture+
Equat ion o f Con crete
Cement+Water+Fine Agg.+Admixture+Mixing+Transportation+Placing+finishing+curing
Strength+Durability+Impermeability+Pleasant Appearance+ Utility+Insulation+Resistance toChemical Attack+ Resistance to Vibration
Product
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IMPORTANCE OF QUALITY CONTROL
It is vital to educate the industry and society to the importance of quality
control and quality assurance and to realize that the additional cost andeffort spent on quality is a greater saving in the long run.
Good construction is always cheaper than poor construction
It is a known fact that you seldom improve quality by
cutting cost, but you can often cut cost by improving
quality.
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Failure of Concrete and Concrete Structures:
There are many causes for the failures of concrete and concrete structures and in most
cases it does not mean complete collapse of the structural element, but that it is no longer
,in a proper way, serving the purpose for which it was designed. It is believed that the
most common causes of failure and the percentage of its occurrence are as follows:
Damages due to Compounds of concrete 40%
Damages due to manufacture of concrete 22%
Damages due to structural design 12%
Damages due to excessive loads 8%
Damages due to foundations 7%
Damages due to fire, etc. 4%
Damages due to collapse of structure 5%
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The problemTypes of Deterioration
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Deterioration & Corrosion
Corrosion is the gradual destruction of material, usually metal,
by chemical reaction with its environment.
Causes:
1. Design Failure
2. Physical Damage
3. Poor Workmanship
4. Structural Movement
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The problem Construction DefectsFeature Cause Effect
Co lour
variations
Variable aggregates Inclusion of
contaminants or deleterious particles
Variable surface texture of theformwork
Staining from formwork
Sugars in some plywood formwork
Uneven curing
Generally only a cosmetic problem
Step in the
surface
Incorrect alignment of formwork
Movement of formwork
Generally a cosmetic problem, but may lead to reduced cover to
reinforcement and long -term durability problems
Blowholes Air trapped against the formwork Slight local reduction in cover to reinforcement, depending on
the blowholes size, but Generally cosmetic problem,only needs to
be filled if filmforming protective coating is to be applied
Honey combing Inadequate aggregate grading and/or
poor compaction
Significant local reduction in the protection to the reinforcement,
could lead to less of effective concrete section
Grout loss Inadequate section of formwork Significant local reduction in the protection to the reinforcement,
Sand runs on
vertical surface
Excessive bleeding Generally a cosmetic problem, but may lead to reduced cover to
reinforcement and long -term durability problems. (May also
indicate plastic settlement cracks on horizontal surface
Scaling Movement of the formwork after
compaction thus removing support
Cosmetic problem only
Staining Rust on formwork before casting:
corrosion pre-duets from elsewhere
(e.g. starter bars that have been
exposed for a period)
Failure of curing membrane to break
down
Cosmetic problem only
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Factors affecting durability
Internal
Causes
Weathering Chemical Action Wear
Freezing
&
Thawing
Moisture
VariationInorganic
SaltsAcids TrafficWindWater
Alkali-
Aggregate
Reaction
Volume
Changes
Permeably
&
Absorption
External
Causes
Temper-
ature
variation
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Effects of Deterioration & Corrosion
1. Frost Attack
2. Chemical Attack
3. Carbonation
4. Alkali-Silica Reaction
5. Chloride Attack
6. Freezing and Thawing
7. Abrasion-Erosion Damage
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Specifying for durable concrete
1. Classification of exposure condition
2. Emphasis on low permeabilty - via
Concrete cover
Mix constituents
Compaction
Curing
3. Specific requirements - eg
Sulphates
Chlorides
ASR
Abrasion
Freeze/thaw
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Adequate cover Adequate cover over the reinforcing steel ensures that
the diffusion of aggressive species to the steel level isdelayed. Rasheeduzzafar et al. (1986), based on their
field and laboratory studies, have recommended a safe
cover for reinforced concrete structures exposed to
various aggressive environments of the Arabian Gulf, as
given below:
Exposure conditions Recommended cover
thickness (mm)
Building components which are permanently exposed to the salt-
laden corrosive atmosphere
50
Building components which are protected against weather and
the aggressive conditions of exposure
25 to 38
Concrete components exposed to seawater and footings as well
as other main structural members cast against the ground
75
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Cube compacted& cured in astandard way
"LABCRETE"
Zone of much poorer
quality concrete
Zone of poorerquality concrete
Zone of poorerquality concrete
Zone of generallyhigher quality
concrete"HEARTCRETE"
"COVERCRETE"
Cross section of a beam
"SITECRETE"
The various "CRETES" according to Dewar
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Durability of RC structures
The durability of a reinforced concretestructure can be related to its permeability
to liquids and gases
an increase indurability can normally be achieved by areduction in the water/cement ratio, which
reduces both the level and size of capillarypores.
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Typical Local Specification for Durability
Parameters.
Test Method Limits
WaterAbsorption-BS 1881 part122
Maximum2% at 28days
WaterPermeability- DIN 1048
Maximum10 mmat 28days
Rapid Chloride
Permeability(RCP),ASTMC1202
Maximum
2000coulombs at 28days
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The problem - Materials
Aggregates ( Coarse & Fine) : contaminated
salty aggregates leads to corrosion of steel,unsound ones leads to deterioration of concrete
and poorly shaped aggregates (Flaky or
elongated) require more water to produce
workable concrete. Other aggregates relateddeterioration:
Aggregates Shrinkage and Swelling
Aggregates Softening
Alkali-Silica Reaction
Contaminated water: used in mixing and
curing causes corrosion of reinforcing steel.
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Admixtures
concrete mixtures incorporating fly ash, silica fume,or fine cements frequently have a low to negligiblebleeding rate, making such mixtures highly sensitiveto surface drying and plastic shrinkage, even under
moderately evaporative conditions (ACI 234R).
Certain admixtures increase the time of initial settingor reduce the amount of water needed for a giveninitial slump or both, but such concretes may stiffen
faster, sometimes too fast even for a cement and anadmixture that separately meet all specifications ,
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pulverized-fuel ash (PFA)
ground granulated blast furnaceslag (GGBS).
condensed silica fume (CSF)
metakaolin (MK)
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Descriptions and Code of practice Advantages Disadvantages
1. The Intrinsic Properties of Concrete1-1. Mix Design PropertiesCement Type(ASTM 150)
Type 1 OPC Isolate steel to avoidattack by chloride
Spoil by sulfateexposure
Type 11 MSRC Isolate steel to avoidattack by chlorideSulfate resistance
5 < C3A< 8
Type III R.H.C For cold weather Not fit in UAEenvironment
Type IV LH.C. For Mass concrete Spoil by sulfateexposure
Type V SRC Sulfate resistance Unable to stopChloride attack
1-2. Cement dosage(variable as to structural design)
300 550 Kg Low permeability Higher heat ofhydration
1-3. Free Water Cement Ratio(DIN 1048 30mm to 60 mm BS5328)
0.36 up to 0.5 Low permeability Low workability
1-4. Use aggregate and dune with lowSO3, Mg2O3 & Acids content, (BS5328)
Not always available
2. Good workmanship
Temperature control, Slump Control,Smooth finish, Preventing watervaporization, (BS 5328)
32o int. 45o ext.
3. Proper vibration(BS 5328)
Avoid honeycombs toreduce air void aspossible stopsegregation
4. Proper curing Prevent sulfate cracksReduce shrinkage
5. Concrete cover Increase as possible Protection for steel
Table : Intrinsic Durability-Enhancing Measures of Concrete in the Region.
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BS8007, CIRIA 91 and
Concrete Society Digest 2 Gross simplification
Not always safe
Crack control not
prevention
(Water retaining
structure designed to
BS 8007)
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Concrete with a waterpermeability coefficient
of not greater than 1x10-
12m/s and with amoderate to high
sulfates resistance
binder (ASTM C1157M)is recommended .
REMARKS
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Durability of ConcreteComponent(s
Descriptio Cause Involve Sympto
Alkali-aggregat Reaction of siliceou Aggregate Coarse "map-crackingaggregates by alkali with viscous flui
ion eruptin
Sulfate attac Reaction of past Paste General cracking an
components wit softenin
sulfate
Acid attack Dissolution by acid Paste (aggregate) General etching o
surfac
Rebar corrosion Rusting of ste Reinforcement Cracks with rust staabove location o
reinforcement
Frost attack Freezing of water i Paste General scaling an
pores spalling at surfac
D-crackin Freezing of water i Aggregate Fine crack patter
pores roughly parallel t
joints in pavemen
Fire damag Decomposition o Paste (aggregate) Cracking and spallin
hydration products an
development of intern
stresses
Thermal cracking Internal stresses fro Paste (aggregate) Localized crackin
Shrinkag restraine
contraction
D R ti RILEM TC 104
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Damage Rating as per RILEM TC 104Damage Damage rating
1( very slight) 2( slight) 3(moderate) 4(severe) 5(very servere)
Cracks in
unreinforcedconcrete
Width 10mm with
spalling
Plastic shrinkage
or settlement, early
thermal
contraction or
drying shrinkage
cracks
Single short
crack
Several
short
cracks
Many short
cracks
Few long cracks Many long cracks
Effects of
reinforcement
corrosion
Individual
narrow cracks
along lines of
bars
Several
narrow
cracks
along lines
of bars
Wide cracks
with edge
spalling or
hollow areas
Many Wide cracks,
some loss of
concrete by
spalling
reinforcement
visible and heavily
corroded
Complete loss of
cover concrete
protruding
Reinforcement,
substantial loss of
reinforcement section
Pop-outs Three-legged
cracks
Pop-outs
barely
noticeable
Pop-outs
noticeable
Holes30mm in
diameter
Surface weathering
or erosion
Barely
noticeable
Clearly
noticeable
in patches
Continuous
weathering
over
area10mm deep
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CHLORIDES Penetration of the chlorides starts at the surface, then
moves inward. The rate of penetration is governed by the
following factors: a) The amount of chlorides coming into contact with the
concrete,
b) The permeability of the concrete, and
c)The amount of moisture present.
Eventually, the concentration of chlorides in contact with
the reinforcing steel will cause corrosion when moistureand oxygen are present.
As the rust layer builds, tensile forces generated byexpansion of the oxide cause the concrete to crack anddelaminate.
Spalling and delamination occur if the natural forces ofravit or traffic wheel loads act on the loose concrete.
cracking overmain steel
tell-tale ruststaining
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Chloride Diffusion shall be Documented- Deterministic Approach
A (10C)
Cs=1.0%
Ccr=0.1%
n=0.30
t0=28 days
D0=1010-13 m2/s
B (30C)
Cs=1.0%
Ccr=0.1%
n=0.30
t0=28 days
D0=4010-13 m2/s
0
0,2
0,4
0,6
0,8
1
1,2
0 20 40 60 80 100 120
Distance from surface [mm]
Northern Europe
Middle East
Critical concentration
34.1 68.20
0,2
0,4
0,6
0,8
1
1,2
0 20 40 60 80 100 120
Distance from surface [mm]
Chloride concentration [%]
Northern Europe
Very hot climate
Critical concentration
34.1 68.2
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Evaluation
Carbonation
tKD CR
Where
D: Depth of carbonation (mm)
KCR: Rate of carbonation mm/yr1/2
t: Service Life in Years
42.0
22.15.2
KR
St
Wheret: Service Life in Years
S: Concrete cover in mm
R= w/c ratio
K: Cl- Content of exposure
solution in PPM
Evaluation
Chloride
Time for carbonation to reach
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Time for carbonation to reach
reinforcement (years)
External concrete sheltered from rain
coverw/c
10 mm 30 mm
0.7
0.5
5 45
15 135
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Enhancements to Chlorides
For structures exposed to chlorides the following enhancementscan be considered (Walker , 1998, 1999 & 2000). Note, that some
of these measures are also useful in offsetting carbonation. 1. Addition of surface treatments or coatings to prevent ingress.
2. Addition of corrosion inhibitors to the concrete mix to reduce theaction of chloride.
3. Addition of coatings to reinforcement to protect its surface.
4. Use non-corroding reinforcement such as stainless steel orpossibly fibre composite materials.
5. Catholic protection
6. Where structurally possible use unreinforced concrete.
note:expansivenature ofcorrosion
Sulfate Attack
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Sulfate Attack
The presence of sulfates in soil and ground waterhas long been a source of attack of concretebelow ground. In hardened cement, calciumaluminates hydrate can react with sulfate salts toproduce a sulphoaluminate some 27% larger in
volume than the solid phase, resulting in gradualdisintegration of the concrete.
Concrete with a water permeability coefficient ofnot greater than 1x10-12 m/s and with a moderateto high sulphate resistance binder (ASTMC1157M) is recommended
.
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sulphates
What is Corrosion of Steel?
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The electrochemical nature of corrosion
anode
+ve
cathode
-vecathode
-ve
What is Corrosion of Steel?
the chemical or electrochemical reaction between a material,usually a metal, and its environment that produces adeterioration of the material and its properties.
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Why is Corrosion of Steel a Concern?
When reinforcement corrodes, the formation ofrust leads to a loss of bond between the steeland the concrete and subsequent delaminationand spalling. If left unchecked, the integrity of
the structure can be affected.
Rust has a substantially higher volume than steel-theoretically
up more than six times greater, depending on oxygen
availability
Stages in Reinforced Concrete Degradation
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Stages in Reinforced Concrete Degradation
Degradation of reinforced concreteoften happens in the following fourstages:
Stage 1: Initially, the concrete appearsto be sound with relatively littlemacroscopic cracking and no reddishdiscoloration from corrosion productformation.
Stage 2: Macroscopic cracks haveappeared and the concrete surface isstained by reddish corrosion products.
Stage 3: Spalling of the concretecover over the reinforcing steel is
clearly visible, due to the formation ofvoluminous corrosion products,
Stage 4: Severe spalling of theconcrete cover over the reinforcingsteel is evident, leaving thereinforcing steel bars directly exposed
to the atmosphere.
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2. Propagation
Corrosion of Reinforcement
1. Initiation
Carbonation Chlorides
Carbonation and chlorides
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Cracking
Why Does Steel in Concrete Corrode?
Rust
Reinforcing Steel
Carbonated zone
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Why Does Steel in Concrete Corrode?
When concrete carbonates to the level of the steel rebar, thenormally alkaline environment, which protects steel fromcorrosion, is replaced by a more neutral environment. Underthese conditions the steel is not passive and rapid corrosionbegins.
Cement Matrix
Carbonated Zone
Steel
Rust
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When chloride moves into the concrete, it disrupts the passive
layer protecting the steel, causing it to rust and pit.
Why Does Steel in Concrete Corrode?
Corrosion Process
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Type of Damage
Transverse cracking
Spalling of concrete
Corrosion inducedlongitudinal cracking
Delamination
Rust and staining Loss of integrity
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Good surface finish Curing
CementAggre-
gateWater
Mixing
Placing Compaction Form_workTempe-
rature
Min.
Moisture
Loss
Quantity
Air entraining
Admixture
Factors that improve
durability
Suitable materialsHomogeneous
Concrete
Workabiliy
Factors that improve
Durability
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Design Strategies for Durability
Avoid or prevent degradation
Reduce environmentalloading
Non reactive aggregate(AAR)
Non-corrodingreinforcement
Cathodic protection
Air entrainment
Service life design
Select the materialcomposition and detailingto resist identifieddegradation risks for aspecific period of time
Multi-Stage ProtectionStrategy
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PART TWO
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PART TWO
Evaluation of Concrete Structures
Types, causes and evaluation of Cracks Non-Destructive tests Maintenance types and Procedures Exercise
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The 3-Stage
Process
Leadingto repair
Investigation
Investigation- Preliminary Survey
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Investigation Preliminary Survey
It is a walk around structure & consists of:
Familiarization with type and extent ofdeterioration
Collecting samples of loose concrete or
lumps that can be easily pulled out
Plan access to hidden areas
Set safety requirements
Equipment required: notebook, camera,measuring tape, hammer, binoculars,
original drawings, papers marked with
grid for sketching
Investigation- Preliminary Inspection
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Investigation Preliminary Inspection
Its objective is to develop an initial of the most
likely causes of deterioration. It mainly consists of
inspecting :
Cracks: location, type, orientation, width and
Length, (To make cracks more visible, spray
concrete with water and avoid noon hours)
Deterioration (spalling, pop-outs, discoloration)
Leaks, damp patches or lime-scale
Reinforcement corrosion
Previous repairs
Location and condition of joints
Condition of any Bearings
Sample of Preliminary inspection Form
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Sample of Preliminary inspection Form
Diagnostic techniques
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Diagnostic techniques visual assessment
Delamination -hammer/chain
covermeter - presence ofreinforcement
chloride analysis
phenolphthalein test for
carbonation half cell measurements to
ASTM C876
resistivity
corrosion rate (linearpolarisation)
permeability
ultrasonics
petrography
radar
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EVALUATION OF RESULTS
Correlation differences between the laboratory conditions and site conditions can vary, and this can affect the
accuracy of our calibration
The variability of the particular test method, the operator skill and the variability of the concrete under
test, control the accuracy with which test results can be calibrated against a particular desired concrete
property
Member
type
Typical 28-day in-situ equivalent
wet cube strength as % of standard
cube strength
Average Likely range
Column 65% 55% - 75%Wall 65% 45% - 95%
Beam 75% 60% - 100%
Slab 50% 40% - 60%
Material Control
and construction
Assumed std.
devn. of control
cube(s)(N/mm2)
Estimated std.
devn. of in-situ
concrete (s )
(N/mm2
)Very good 3.0 3.5
Normal 5.0 6.0
Low 7.0 8.5
EVALUATION OF RESULTS
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EVALUATION OF RESULTS
Tests have well-defined procedures and the methods used for the calculation and assessment of different
parameters from directly measured values will depend to a large extent on the test method used
Variation in properties of hardened concrete tend to be random and requires that the results be analyzed usingvarious statistical tools such as graphical and numerical methods
The number of test types, location and points used has a
significant bearing on the ease with which the variability of
concrete within members and between members can be
assessed.
Test method
No. of individual reading
recommended at a location
Standard cores 3
Small cores 9
Schmidt hammer 12
Ultrasonic pulse
velocity
1
Internal fracture 6
Windsor probe 3
Pull-out 4
Pull-off 6
Break-off 5
Test method
Typical COV forindividual member of
good qualityconstruction
Best 95% confidence limitson strength estimates
Cores standardsmall
10%15%
10% (3 specimens ) 15% ( 9 specimens )
Pull-out 8% 20% ( 4 tests )
Internal fracture 16% 28% ( 6 tests )
Pull-off 8% 15% ( 6 tests )
Break-off 9% 20% ( 5 tests )
Windsor probe 4% 20% ( 3 tests )
Ultrasonic pulse velocity 2.5% 20% ( 1 test )
Rebound hammer 4% 25% ( 12 tests )
introduction
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introduction While concrete look nice when they are new, over time the concrete can chip, crack
and crumble.
Cracks and potholes form due to the freezing and thawing of water that has seeped
through smaller cracks, weed or grass growth in small cracks, and general wearand tear.
Regular maintenance will prevent this problem.
This is usually easy to do and requires up to a half day to complete depending onthe condition and size of your repairs.
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Types
ofCrack
s
External
Restraint
TYPES
OF
CRACKS
BEFORE
HARDENING
AFTER
HARDENING
CONSTRUCTIONAL
MOVEMENT
PLASTIC
EARLY FROST DAMAGE
PLASTIC SETTLEMENT
PLASTIC SHRINKAGE
FORMWORK MOVEMENT
SUB-GRADE MOVEMENT
STRUCTURAL CREEP
DESIGN LOADS
ACCIDENTAL OVERLOAD
THERMAL
FREEZE / THAW CYCLES
EXTERNAL SEASONAL TEMPERATURE VARIATIONS
EARLY THERMAL CONTRACTION
Internal
Temperature
Gradiets
CHEMICAL
CORROSION OF REINFORCEMENT
ALKALI-AGGREGATE REACTIONS
CEMENT CARBONATION
DRYING SHRINKAGE
CRAZING
SHRINKABLE AGGREGATES
PHYSICAL
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Plastic
settlement
Plastic
shrinkage
Plastic shrinkage
Corrosion
Early
thermal
contraction
Alkali-silica
reaction
Crazing
Shear
cracks
Long term drying
shrinkage
Tensio
nbendin
g
cracks
Types of Cracking
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Structural cracks
Types of Cracking1. Structural cracks
2. Non structural cracks or Intrinsic cracks
Non Structural Cracks
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Non Structural Cracks Intrinsic or non structural cracks are attributable to chemical
or physical changes taken place within concrete.
The classification of intrinsic cracks might enable designersand contractors to take measures which will either preventor control these cracks.
Reinforcing bars
Intersecting cracks
Coincident cracks
Cl ifi ti f k
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Classification of cracks
Cracks maybe separated into two classes forthe purpose of deciding upon the type ofrepair.
a) dormant cracks .
1) fine cracks:2) wide cracks:
3) fractures :
b) live cracks.
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The problem Cracking occurring during Construction
Plastic Shrinkage Cracks
Plastic Settlement Cracks
Type of defect Typical time of appearance
Plastic settlementcracks Ten minutes to three hours
Plastic shrinkage
cracks
Thirty minutes to six hours
Construction defects On removal of formwork
Crazing One to seven days-sometimes
much later
Early thermal
contraction cracks
One day to two or three
weeks
Longtern drying
shrinkage cracks
Several weeks or months
Chemical attack
(including sulfate
attack)
Few months up to Several
years depending on nature of
the materials
Damage due to
temperature
movement (seasonal)
Probably up to a year ,but
may be longer
Alkali-silica reaction Several years
Reinforcement
corrosion
Several years, but may be
much shorter
Plastic Shrinkage Cracking
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Plastic Shrinkage Cracking
The probability for plastic-shrinkage cracks
to occur may be increased if the setting time
of the concrete is delayed due to the use ofslow-setting cement, an excessive dosage of
retarding admixture, fly ash as a cement
replacement, or cooled concrete
Surface drying is initiated whenever the
evaporation rate is greater than the rate
at which water rises to the surface of
recently placed concrete by bleeding .
concrete mixtures incorporating fly ash, silica
fume, or fine cements frequently have a low to
negligible bleeding rate, making such mixtures
highly sensitive to surface drying and plastic
shrinkage, even under moderately evaporative
conditions (ACI 234R).
231
0.0
0.8
0.2
Crack width and corrosion
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Crack width and corrosion
There is arelationship
between the
crack width and
corrosion of
steel.
Surface
crack
width(mm)
Average
depth of
corrosion(mm)
Average
corroded
length(mm)
0.13 0.16 9.2
0.25 0.16 12.9
0.51 0.18 12.8
1.27 0.21 15.0 >0.05
0.1
0.4
1.0
0.5
1.5
Reducing cracks
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Reducing cracksCracking in con crete can be reduc ed signi f icant ly or el iminated b y obs erv ing the
fol lowing pract ices:
Use prop er subgrade preparat ion, inc luding u ni form s upp ort and propersubb ase mater ia l at adequate moistu re con tent .
2. Minimize the mix water content by maxim iz ing the size and amou nt ofcoarse aggregate and use low -shr ink age aggregate.
3. Use the lowest amou nt of m ix water required for w orkabi l i ty ; do n otpermit over ly wet consis tencies.
4. Avo id calcium chlor ide admixtu res.
5. Prevent rapid loss of su rface moisture w hi le the concrete is st i l l plast icthroug h us e of spray-appl ied f in ishin g aids or plast ic sh eets to avoidplast ic-shr ink age cracks.
6. Provid e contractio n jo ints at reasonable intervals, 30 times the slabth ickness.
7. Provide isolat ion jo ints to prevent restraint from adjo in ing elements ofa structure.
8. Prevent extreme changes in temperature.
9. To m inimize cracking on top of vapo r barr iers, use a 100-mm thick (4-in.) layer of sl ight ly damp , compact ib le, drainable f i l l choked o ff wi th f ine-grade mater ial . If co ncrete mus t be placed direct ly on polyethylene sheetor other vapor barr iers, use a mix with a low water content .
10. Pro er l lace conso lidate fin ish and cure the concrete.
Testing- Scope and Guidance
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Testing- Scope and GuidanceTesting is performed in order to obtain sufficient
information on the condition of the deteriorated
structure so that the appropriate remedial repairmethod is implemented. The sampling rate, type
and location of tests shall include:
Different elements (Columns, beams, Slab)
Typical deteriorated areas
Typical Non-deteriorated areas
Areas with Different exposure conditions
Previously repaired areas
NO TESTS SHALL BE CARRIED OUT UNLESS IT IS
KNOWN WHAT THE RESULTS WILL BE USED FOR
Testing Types of Tests & Location
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Testing Types of Tests & Location
Location: Concrete on top layer tends to be weaker than the
bottom one- well distribution shall be maintained
ASSESSMENT OF PROPERTIES
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Property under
investigationTest Equipment type
Corrosion of
embedded steel
Half-cell potential
Resistivity
Linear polarization resistance
Cover depth
Carbonation depth
Chloride concentration
Electrochemical
Electrical
Electrochemical
ElectrochemicalChemical/microscopic
Chemical/electrical
Concrete quality,
durability and
deterioration
Surface hardness
Ultrasonic pulse velocity
Radiography
Permeability
Absorption
Petrographic
Sulphate content
Air content
Abrasion resistance
Mechanical
Electromechanical
Radioactive
Hydraulic
Hydraulic
Microscopic
Chemical
Microscopic
Mechanical
Concrete strength
Cores
Pull-out
Pull-off
Break-off
Penetration resistance
Maturity
Mechanical
Mechanical
Mechanical
Mechanical
Mechanical
Chemical/electrical
Integrity and
performance
Pulse-echo
Acoustic emission
Thermoluminescence
Thermography
Radar
Reinforcement location
Strain or crack measurement
Load test
Mechanical/electronic
Electronic
Chemical
Infra-red
Electromagnetic
Electromagnetic
Optical/mechanical/electrical
Mechanical/electronic/ectrical
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TYPES OF TESTS Destructive tests:
These conventional methods enable thestrength of the concrete to be measured byway of cores or cubes cut from the concrete.However, this is not possible in all cases andespecially not for slender members.
Non-destructive tests:
By definition, the strength properties arenot measured directly so some otherproperties are measured and the strengthestimated by calibration. Naturally, thesemethods have the great advantage thatconcrete is not damaged. For example: Ultra-sound test and Schemed Hummer Test.
Partiall y destructi ve tests:
In these tests, the concrete is tested tofailure but the destructive resulting is verylocalized and member under test is notweakened to any significant extent Forexample Core test. .
Testing Types of Tests & Location
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Testing Types of Tests & LocationDirect: equipment gives direct result for property
being tested
Indirect: the required property is determined
indirectly
Qualitative: Test will not yield quantitative results
A Range of Techniques used for the Non-DestructiveTesting of Concrete
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surface
absorption
of water
Indentation Rebound
surface
hardness
surface methods
pulse
velocity
shock waves
pulse
attenuation
ultrasonic
pulse
propagation
damping
capacity
torsional longitudinal
damping
capacity
flexural
Resonance
Vibration methods
Radiography
x-rays rays
Absorption Back -Scater
Radiometry
Neutrons
Radio acive methods
Magnetic
steel
detection
Microwave
absorption
Dielectric
Conductivity
Electrical
methods
Non-destructive testing of concrete
Testing of Concrete
Testing Types of Samples
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Testing Types of Samples
Lump Samples: They are broken small pieces from the
structure good for visual examination and chemical
testing.Cores: are cylindrical shape samples cut by a drill with
hallow barrel tipped with industrial diamond bit. Core
diameter for compressive strength can be either 100, 120,
or 150 mm
Dust Samples: are obtained
directly from structures using
hand held rotary drills and
dust is collected via a shroud
around the bit or by skewedtube connected to a plastic
bag as shown in the adjacent
figure
Testing - Sampling
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Testing SamplingFor elements that contain chloride, it is suggested
that 10 % of each elements (Col, Beams, slabs) to
be tested with a minimum of 3 from each type.
The Building Research Establishment, suggests
the following:
Classification of Various Test Methods
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Destructive tests.
These conventional methods enable the strength of the concrete to be measured by way of cores or cubes cut
from the concrete. However, this is not possible in all cases and especially not for slender members.
Non-destructive tests.
By definition, the strength properties are not measured directly so some other properties are
measured and the strength estimated by calibration.
Naturally, these methods have the great advantage that concrete is not damaged
Partially destructive tests.
In these tests, the concrete is tested to failure but the destructive resulting is very localized
and member under test is not weakened to any significant extent
Ultrasonic Pulse Velocity
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Ultrasonic Pulse Velocity
The ultrasonic pulse velocity technique is based on the ability to measure the propagation velocity of a pulse of
vibrational energy which has passed through a concrete medium.
Knowing the direct path length between the transducers, and the time of travel, the pulse velocity through the
concrete can be obtained.
Property under
investigationTest
Corrosion of
embedded steel
Half-cell potential, Resistivity, Linear
polarization
Cover depth, Carbonation depth
Concrete
quality,
durability anddeterioration
Surface hardness, Ultrasonic pulse velocity
Radiography, Relative humidity,Permeability,
Absorption, Sulphate content.Expansion, Air
content ,Cement type and content,Abrasion
resistance
Concrete
strength
Cores, Pull-out, Pull-off, Break-off
Penetration resistance, Maturity
Integrity and
performance
Pulse-echo, Dynamic response, Radar
Acoustic emission, Thermography
Strain or crack measurement, Load test
V= L / T
Where:
V=Pulse velocity
L= Path length, mm
T= effective time, microsecods
IN-SITU Testing
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IN SITU Testing
Half Cell potential: It measures the electrical
potential on the surface of steel to qualitatively
estimate the its likelihood of corrosion.
Potential P
( mV)
Risk of
corrosion
P > -200 mV 5 %
-350< P< -200 50 %
P< -350 95 %
Half Cell Potential
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Half Cell Potential
BS 1881
PurposeTo determine the risk ofcorrosion in reinforcement.
Results Range
Our results
They range between -200 and -300mV, then we conclude thatthere is 50% risk of corrosion
Concrete Chloride Content
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Concrete Chloride Content
bS 1881
PurposeInspect corrosion of reinforcement
Result Ranges
Not to exceed
Max. Chloride content = 0.4% by weight of cementfor reinforced concrete, InGulf only allow for 0.3%.
= 0.1% by weight of cement
for prestressed concrete Our Results
Ranges between 0.04% and 0.1%
TESTING OF CONCRETE
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METHOD STANDARDS PRINCIPLE
FEATURES
ASTM BS 1881
Rebound
hammer
C805 Existing
concrete,best
used
comparatively
Pull out C900 207 Existing
concrete , high
variability
Pull off 207 Existing
concrete
surface orpartially cored
Break off C1150 207 New
construction or
Exsisting
concrete
IN-SITU Testing
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Surface Hardness: Rebound (schmidt) hammer: used
to indirectly asses the strength of Concrete
Near Surface Strength: used to asses the strength ofconcrete near surface
1) Pull out Test 2) Capo (Cut and Pull-out)
3) Pull off Tests 4) Break off Tests
5) Penetration Resistance
Ultrasonic
Pulse Velocity
Test: used to
assess variationin the strength
and presence of
Void,
Honeycombs Direct IndirectSemi-Direct
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correlation between the pulse velocity & cube compressive
strength
20
22
24
26
28
30
32
34
36
38
40
4.7 4.8 4.9 5 5.1 5.2 5.3 5.4
Pulse KM/s
C
ompressiveStrength(N/mm2)
Maintenance Management System
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Maintenance Management System
Policy & Resources
Committee
Property
Department
Architects Quantity Surveyor
Engineers BuildingMaintenance
Area surveyor
Senior surveyor
Surveyorstechniciansinspectors
Valuers Rural Practice
Maintenance is a combination of any actions carried out to retain an item
in ,or restore it to an acceptable condition
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The maintenance of structures is done to meet thefollowing objectives:
Prevention of damages and decay due to natural
agencies to keep them in good appearance andworking condition.
Repair of the defects occurred in the structure andstrengthen them if necessary.
i f i
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Necessity of MaintenanceThe maintenance of structures is done to meet the
following objectives: Prevention of damages and decay due to natural
agencies to keep them in good appearance andworking condition.
Repair of the defects occurred in the structure and
strengthen them if necessary. MAINTENANCE is a combination of any actions
carried out to retain an item in ,or restore it to anacceptable condition
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Types of Maintenance1. Routine Maintenance (Cyclic Maintenance)
2. Preventive Maintenance (Scheduled maintenance.
3. Corrective Maintenance (Emergency maintenance.)
R ti M i t
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Routine Maintenance
Its the service of maintenance attended to thestructure periodically.
It is done by the fund provided annually for thepurpose which is normally 1 % of the costof construction.
This is rendered to meet day to day problem ofnormal nature and includes the inspection,
planning the program and executing thesame.
It includes white washing, patch repair toplaster, replacement of fittings and fixtures,binding of road surface.
Preventive Maintenance
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Preventive Maintenance
The maintenance work done
before the defects occurred ordamaged developed in the
structure.
It includes through inspection,planning the program if
maintenance and exacting the
same.
It depends upon thespecifications, condition and
use of structure.
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It is the maintenance done after the defects or
damage occurs in the structure.
Corrective Maintenance:
Wh t t k ti
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Corrosion
0
0.5
1
When to take action
Relative
deterioration
Time to onset of corrosion
Time to first cracking
Time to first spalling
Time to failure
Time
A summary of a decision making process for investigating and assessing
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Routine inspection
Required as part of asset management systemAd hoc inspection because:
Evidence of cracking or spalling of concrete
Requirement for durability assessment of structure
Change of use or ownership
Initial assessment of current state of structure
Investigation, testing and durability assessment
(These can be different for individual elements of the structure)
Determine cause of deterioration and whether it is corrosion related
Determine degree of deterioration
Establish:
Intended use of structure
Design life of structure
Residual service lifespan
Required performance characteristics
Consider:
original design approach
Environment and contaminationConditions during construction
Conditions of use
History of structure
Identification of active deterioration mechanisms
Type A Type B Type C Type D
Carbonation Cast-in chlorides Ingressed chlorides Carbonation & Chlorides
Contributory
deterioration
mechanisms
Evaluation of deterioration
Establish cover depth
Establish chloride concentrations
Establish depth of carbonation
Establish condition of steel
Assess structural implications
Monitoring
Periodic Continuous
Modeling and prognosis
Future chloride concentrations
Future depth of carbonation
Future corrosion rate of steel
Detailed assessment of condition of structure or element
Choose repair and protection principle appropriate to type of durability deterioration process
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PART THREE
Purpose and Scope of Concrete Repair
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Purpose and Scope of Concrete Repair
Repairs are performed in various ways on concrete
structures in order to extend its service life
Time
Deterioration
End of Service Life
Initiation Period Propagation Repair Cycles
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Average chloride ion content by weight of cement (%)
4b 40 years-old concrete structures
Negligible
Low Very highHigh
Low Moderate
Moderate
High
Damp
environment
Dry
environment
Dry
environment
Damp
environment
0 0.60.4 0.80.2 1.51.0
Low Moderate
Moderate
High
Very High
Very high
Where the reinforcement is still
within the alkaline zone (pH>10)
Where the reinforcement is in
lower alkaline condition (pH
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Repair techniques
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The scope of repair works is summar ized as fo l low s:
Replacement of spalled areas
Sealing of cracks wider than 0.2mm
Application of Additional Cover
Protective Coating System to Concrete Surfaces
Waterproofing System
Bearings
p q
Materials for repair
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1) Resin mortars:
To resist a wide range of aggressive chemicals. Having the ability to cure under environmental
condition.
2)Epoxy mortars: In a well formulated epoxy mortar the shrinkage
can be as low as 20 micro strains.
3)Bonding coats: bonding coats are used to promote the adhesion of
the repair composition to the concrete substrate.
Details of specimens and test methods utilized to
determine the properties of resin based repair mortars
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Test methodNo. of
specimens
tested per
component
Property
ASTM C 308 [14]3Pot life
ASTM C 884 [15]3Rate of cure
BS 6319 part 4 [12]3Adhesion
ASTM C 579 [16] Method A6Compressive
strength
ASTM C 307 [17]6Tensile strength
ASTM C 580 [18]6Flexural strength
ASTM C 580 [18]6Elastic modulus
ASTM C 531 [11]6Shrinkage
ASTM C 531 [11]6Thermal expansion
ASTM C 1202 [13]3Chloride
permeability
ASTM C 267 [19]3Chemical resistance
determine the properties of resin-based repair mortars
Details of specimens and test methods utilized to determine the properties of bond coat materials.
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Test methodNo. of
specimens
tested per
componen
t
Property
BS 6319 part 4 [12]6Improvement in
bond
ASTM C 1202 [13]3Chloride
permeability
Non-standard3Carbonation
Non-standard3Electrical resistivity
Details of specimens and test methods utilized to determine the properties of steel primers.
Test methodNo. of
specim
ens
tested
percompon
ent
Property
ASTM D 4541 [21]3Adhesion to steel
Non-standard3Sensitivity to steel
cleaning
ASTM D 1654 [22]3Resistance to salt
exposure
ASTM G 78 [23]3Crevice attack
Non-standard3Resistivity
Details of specimens and test methods utilized to determine the properties of surface coatings.
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Specimen sizeTest methodNo. of
speci
mens
tested
percomp
onent
Property
62x 100 x 300 mm (concrete)ASTM D 4541 [21]3Adhesion
25x 25 x 250 mm (mortar)Non-standard3Crack bridging
75mm dia and 50 mm high (concrete)Non-standard3Chloride diffusion
50mm dia and 72 mm high (mortar)Non-standard3Moisture resistance
150x 150 x 150 mm (concrete)DIN 1048 [24]3Water permeability
50mm dia and 72 mm high (mortar)Non-standard3Carbonation
resistance
25x 25 x 25 mm (mortar)ASTM C 267 [19]3Chemical resistance
Sealers and Concrete Surface Coatings
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Environment Preferred concrete surface treatment material
CO2 Silane/siloxane with acrylic topcoat; acrylic coating
Sulfate Silane/siloxane with acrylic topcoat
Chloride Silane/siloxane with acrylic topcoat; silane; acrylic coating
Purpose Suggested coating
Cement-based Resin-based
Moisture barrier Polymer-modified cement Epoxy resin
Chloride barrier Epoxy-modified cement Epoxy resin
Crack bridging Polymer-modified cement Epoxy resin
CO2 barrier Polymer-modified cement Acrylic or epoxy resin
Chemical resistance Polymer-modified cement Epoxy resin
Repair- Reinstatement with Mortar1 Breaking Out
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2- Cleaning The ExposedReinforcement & Substrate
1- Breaking Out
Spalled Concrete
3- Applying protective
Coating to exposed steel
4- Soaking or applyingBonding agent to substrate
6- Reinstatement with mortar
(Patching)
7- Curing
5- Install formworks for
slurry type mortar
Repair- Reinstatement with MortarTypical ShuttersMethods of
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Method
of fixing
anchors
Typical Shutters
For Repair
Methods of
Breaking concrete
Repair- Cathodic ProtectionIt is used to prevent or reduce corrosion rates It works by
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It is used to prevent or reduce corrosion rates . It works by
connecting the metal reinforcement to another material which
is anodic in relation to the metal reinforcements. The metal
becomes a cathode and its corrosion is reduced. Twosystems are used:
Sacrificial anode: It consists of small
zinc, or magnesium blocks tie around
reinforcements at 50 to 75 cm. They aremore reactive than steel and reacts with
chloride faster.
Impressed Current System: Inert
material (mesh) connected to a DC
power supply so that the reinforcement
will stay protected in a cathode state
Re-Alkalization & CL- ExtractionRe-Alkalization is an electrochemical
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Re-Alkalization is an electrochemical
treatment for reinstating the passive
state around reinforcement. This is
achieved by passing an current thruthe concrete to then reinforcement
using an externally applied anode that
is attached to the concrete surface.
Chloride Extraction is anelectrochemical process for removing
corrosive chloride from concrete. It is
achieved by applying an electrical field
between reinforcement and an external
anode mesh. As a result Cl- are
transported towards the anode and outof the concrete. Also a high PH is
formed and protection of steel is re-
established.
Repair Other Techniques
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Coating:
Barrier Coating form a film on the surface Ex :Epoxy coating, Acrylic, Polyurethane and Polymer
cement coating
Pore Blocker: They are solvents that do not form a
film on the surface. Instead they penetrate thecapillary pores and block them via crystallization.
Pore liner: Also do not form a film on the surface.
They react with the silica in concrete to create a water
repelling compound.
Sealer: they form a film on the surface and also
penetrate the pores to block them.
Crack Injection: Resin is injected under
Repair Other Techniques
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Crack Injection: Resin is injected under
pressure through drilled holes that intersecting
the cracks in order to close these cracks and
prevent contamination from reachingreinforcement.
Corrosion Inhibitors:
Calcium Nitrate: they are added to concrete at the time of mixing
and reacts with the ferrous of the steel to make a passive stable
layer up to certain chloride concentration. They are usuallyapplied at a rate of 2 liters of Calcium nitrate / kg of Chloride
concentration per m3 of concrete.
Migrating Corrosion Inhibitors (MCI): Recently developed,
they follow the same principles of calcium nitrate but can be
applied on the surface of the concrete. It is claimed that they
migrate from the surface to the reinforcement to react with it and
form on its surface a monomolecular layer which displace any
chloride and protect the reinforcement from attack. Rate = 1l/m3
Repairing Techniques
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Repairing Techniques
Repairing optionsNo repair Partial Repair full repair
Repairing process:Reinforcement Replacement
Concrete removalConcrete cleaning
Old reinforcement cutting and cleaning
Reinforcement Protection
Coupling systemIt is recommended for the deck slab due to limitation of space
Straight labs system
It is recommended for the wing wall
REPAIR METHOD (Galva shield )
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Can be used in corrosive environments includingchloride contaminated and carbonated concrete
Extends service life of patch repairs User-friendly and easy to install
Galva shield XP anodes provide localized corrosion
protection in reinforced concrete buildings andstructures. The palm-sized anode consists of agalvanic zinc core surrounded by an activecementitious matrix
The Benefits
Repair to spalled concrete
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Install structural supportingsystem as necessary.
Remove spalled concrete instages observing structuralrestrictions to a depth of50mm behind thereinforcement .
Delineate the area to a voidfeathering affects.
Welding new pars.
Apply epoxy coating to
provide adhesion toconcrete.
Apply replacement concreteof cementations mortar.
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Repair ing c racks
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Repair ing c racks
Repairing Techniques
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Repairing Techniques
Repair of cracks:
All cracks are treated the same way except thedifference between live cracks and dead cracks
Live cracks are sealed with flexible material tosupport the effect of its movements
Dead Cracks are sealed with a cementitiousmaterial
Repair failure
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Repair failure
debonding
shrinkage
cracking
corrosionagain
evident
Sealing of cracks & joints
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g j Perrier to drilling for injections
points ,reinforcement shouldbe located using a covermeter.
Spaces between the injectionspoints shall be temporarilysurface sealed along thecracks or joints.
All injection joints shall becleaned using oil freecompressed air.
Injections should start at oneend and work progressivelyalong the joints or cracks.
Repairing cracks
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1-Chisel out the crack 2-Clean loose material
3-Apply at thin layer of bonding 4-Mix vinyl reinforced patching
5- Variation when repairing a large crack
Tips
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Tips
Repair concrete cracks when the temperature is above 50 F degreesand overnight temperatures are not expected to drop below freezingthe next few nights.
Don't do repairs when it's too hot or too windy. The material will dryout too fast resulting in a weak repair. If this is unavoidable, then putplastic over it or shade it.
After you repair concrete cracks, it's always a good idea to put a coatof concrete sealer over the area to help prevent water seapage.
If your repairs are a darker color than the surrounding concrete, tryrubbing it with a flat stone. This will turn it white making it less
noticable.
If you plan to acid stain, be sure the caulk or patching used for anyrepairs contains cement or cementations material. If not the acid won'treact and the repairs will be left uncolored.
Protection of Reinforcing Steel
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Use of Inhibitors: Inhibitors are normally added to concrete to protect thereinforcing steel. They are widely used as durability enhancing materials forreinforced concrete structures. An ideal corrosion inhibitor is a chemical
compound that when added in adequate quantity can prevent corrosion ofembedded steel and has no adverse effect on the properties of fresh andhardened concrete. Several inhibitors have been proposed to inhibitreinforcement corrosion in the presence of chloride ions. Lafave (2002)reviewed nearly 50 papers and reports from research on corrosion-inhibitingadmixtures used individually in structural concrete. Based on the literaturereview they arrived at the following recommended optimum admixturedosage for corrosion protection of mineral and chemical admixtures: Silicafume(10 to 15%) cement replacement, Fly ash (25 to 35%) cementreplacement, GGBFS (40 to 55%) cement replacement, Calcium Nitrite (15to 25 L/m3) of concrete.
Mineral Corrosion Inhibitors: Mineral corrosion inhibitors that are mostcommonly used in the UAE are: Silica Fume, Fly ash, and Ground
Granulated Blast Furnace (Sabouni, 1999).
Chemical Corrosion Inhibitors: The most commonly used chemicalcorrosion inhibitors is calcium nitrite. Calcium nitrite is typically mixed intoconcrete as slurry. In concrete, calcium nitrite promotes stabilization ofreinforcing steel's natural passivating layer. Nitrite is an inhibitor thatreduces the transport of ferrous ions to the electrolyte; in other words, nitrite
blocks the current path between adjoining mats of reinforcement. The
Avoid Deterioration by Mixing Stainless Steel with Black Steel
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In humid atmosphere
Different electro-chemical
potentials leads to Galvanic
Corrosion (Bi-metal corrosion)
In alkaline concrete
High pH leads to the sameelectro-chemical potentials,
hence no corrosion !
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Coating and alloying of rebars
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Coating and alloying of rebars
One of the ways of preventing corrosion of thereinforcing steel is by applying a protective coating onthem.
Coating of conventional reinforcement with organic orinorganic coatings may also result in the prevention ofcorrosion by isolating the steel from coming in contactwith oxygen, moisture, and chlorides.
Epoxy coating and zinc coating (i. e., galvanization) are
also utilized. Yet another way of minimizing the steel corrosion is
through micro-alloying the same.
corrosion inhibitors
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Contamination Preferred corrosion
inhibitor
Chloride (0.8% Cl-) 4% calcium nitrite or 4%
calcium nitrate
Chloride and sulfate
(0.8% Cl- + 1.5% SO3)
4% calcium nitrite or 3%
calcium nitrate
Sea water 4% calcium nitriteBrackish water 2% calcium nitrite
Unwashed aggregate 4% calcium nitrate
A recent study, on the effectiveness of four types of corrosion inhibitors,
calcium nitrite, calcium nitrate, and two organic inhibitors in
contaminated concrete, conducted by Al-Amoudi et al. (2003) showed thatalthough all the four corrosion inhibitors investigated were effective in
delaying the initiation of reinforcement corrosion. However, calcium nitrite
was distinctly efficient in the concrete specimens contaminated with
chloride, chloride plus sulfate and sea water
Monitoring
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Monitoring
Monitoring is primarily a diagnostic or controlprocess to help understand the in-service
performance or management of a structure. It is
also a valuable tool in the routine assessment of
a structure. Monitoring may be either a periodicor repeated activity, or a continuous recording of
data.
The major advantages of continuous
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The major advantages of continuous
monitoring are that:
1. Electrochemical probes embedded in a new
structure can give early warning of potential
durability problems, especially in critical areas.2. Once installed, access is not required again
3. Retrofitted probes can be used to access the
effectiveness of remedial techniques.
SILOS
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Recent Improvements
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The increasing availability and use of Mineral Additions (such as
microsilica, pfa and ggbfs) as cement replacements
Advances in local formulation and production of highly efficient SuperPlasticisers which have enabled the Free Water/Cementitious Ratio to bereduced to 0.35, or even less
Recognition of the importance of the thickness and the quality of theconcrete in the cover zone
Improvements in the quality of Epoxy Coated Rebar
Improvements and increased use of surface coating materials
The availability of Corrosion Inhibitors
The increased use of Cathodic protection and prevention systems
REFERENCES ACI Committee 318 (1999), Building Code Requirements for Structural Concrete
(318M-99) and Commentary (318RM-99), American Concrete Institute, Michigan,
USA
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USA.
ACI Committee 440 (2002), Guide for the design and construction of externally
bonded FRP systems for strengthening of concrete structures, American Concrete
Institute, Michigan, USA.
FIB Bulletin 14, Design and use of externally bonded FRP reinforcement for RC
structures. 2001.
Macdonald, M. D. and Calder, A. J. J. (1982), Bonded steel plating for strengthening
concrete structures, International Journal of Adhesion and Adhesives, No. 4, pp. 119-
127.
Meier, U. (1997), Repair using advanced composites. International Conference :
Composite Construction - Conventional and Innovative, Innsbruck, Austria, IABSE,
pp. 113-123.
Neale, K. (2001). Strengthening reinforced concrete structures with externally-bonded
fibre reinforced polymers - design manual no. 4. ISIS Canada, Winnipeg, Manitoba,
Canada.
SAI (2001), Concrete structures, Australian Standard AS3600-2001, Standards
Australia International, Sydney, Australia. Teng, J. G., Chen, J. F., Smith, S. T. and Lam, L. (2002). FRP strengthened rc
structures. Chichester, England, John Wiley & Sons, Ltd.
BRE Information Paper-Testing Anti-Carbonation Coatings for Concrete. . . . . . . . . . . . . . . . . .
AASHTQ-,Guide Specifications for Polymer Concrete Bridge Deck Overlays-Reference on ly. .
Corrosion Management
, ACI 222R-01-Protection of Metals in Concrete Against Corrosion. . . . . . . . . . . . . . . . . .
V BRE Digest 444 Corrosion of Steel in Concrete
Part3:ProtectionandRemediation 1679
BRE D53-Guide to the Maintenance, Repair, and Monitoring of Reinforced
Concrete Structures-Reference only1691
i/'ts TR 36-Cathodic Protection of Reinforced Concrete. . . . . . . . . . . . . .
CS TR 37-Model Specification for Cathodic Protection of Reinforced Concrete. . . . . . .
A Monograph No: 2-An Introduction to Electrochemical Rehabilitation Techniques. . . . . .. . . . . .
CPA Monograph No: 4-Monitoring & Maintenance of Conductive Coating Anode
Cathodic Protection Systems 1819
CPA Monograph No: 6- The Principles and Practice of Galvanic Cathodic Protection for Reinforced Concrete Structures1823
CSA S448. 1-93-Repair of Reinforced Concrete in Bui ldin gs-Reference only . . . . . . . . . , . .. . . . . . . .
FIP-Guide to Good Practice for Repair and Strengthening of Concrete Bridg es-Reference only . . . . .
ACt 345.1 R-92 (Reapproved 1997)-Routine Maintenance of Concrete Bridg es-Reference only . . . . . .
REFERENCES
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ACt 345.1 R 92 (Reapproved 1997) Routine Maintenance of Concrete Bridg es Reference only . . . . . .
CS TR 33-Assessment and Repair of Fire-Damaged ConcreteStructures. . . . . . . . . . . . . . . . . . . . . . . .
CI 546.1 R-80 (Reapproved 1997)-Guide for Repair of Concrete Bridge Superstructures. . . . . : . . . . . .
ACI 546.2R-98-Guide to Underwater Repair of Concrete. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ACI 210R-93 (Reapproved 1998)-Erosion of Concrete in Hydraulic Structures. . . . . . . . . . . . . . . . . . . .
ACI 210. 1 R-94 (Reapproved 1999)-Gompendium of Case Histories on Repair of
Erosion-Damaged Concrete in Hydraulic Structures 1979
USACE EM 1110-2-2002, Chapter 8-Evaluation and Repair of Concrete Structures. . . . . . . . . . . . . . .
CI362.2R-0D-Gu'de for Structural Maintenance of Parking Structures. . . . . . . . . . . . . . . . . . . . . . . . .
ACPA TB-020.02P- The Concrete Pavement Restoration Guide:
Procedures for Preserving Concrete Pavements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
ACPA TB-002.02P-Concrete Paving Technology-Guidelines for Full Depth Repair. ..
ACPA TB-003.02P-Concrete Paving Technology- Guidelines for Partial-Depth SpaIi Repair
ACPA TB-005P- Technical Bulietin-Guidelines for Unbonded Concrete Overlays. . . ..
ACPA TB-008.01 P-Diamond Grinding and Concrete Pavement Restoration. ..
ACPA TB-007P- Technical Bulietin-Guidelines for Bonded Concrete Overlays. . . . . ...
MSHTuide Specifications for Polymer Concrete Bridge Deck Overlays. . . . . . . ..
CRA-Standard Method of Measurement for Concrete Repair. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
CS TR 38-Patch Repair of Reinforced Concrete-Subject to Reinforcement Corrosion. . . . .. . ...
ICRI Guideline No. 03735-Guide for Methods of Measurement and Contract Types for Concrete Repair Work
ACI 22.1 R-93 (Reapproved 1998), Chapter 3-Causes, Evaluation, and Repair
of racks in concrete Structures
ICRI Guideline No. 03734-Guide for Verifying Field Performance of Epoxy Injection of Concrete Cracks..
ACPA TB-018P-Concrete Paving Technology-Slab Stabilization Guidelines for Concrete Pavements. . . . .
p/ ACI 440.2R-02-Guide for the Design and Construction of Externally Bonded FRP Systems for
Guide to Surface Treatments for Protection and Enhancement of Concrete. . . .. ...
ICRI Guideline No. 03732-Selecting and Specifying Concrete Surface Preparation for
Sealers, Coatings, and Polymer Overlays ..
1JSACE TN CS MR 4.4--Cleaning Concrete Surfaces. . . . . . . . . . . : . . . . . . . .. . . . . . . . . . . ..
USAGE TN CS MR 4.3 ER-Removal and Prevention of Efflorescence on Concrete and Masonry
ACI 224.1 R-93 (Reapproved 1998), Chapter 3-Causes, Evaluation, and Repair of
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