CONTENT
1. Introduction
2. Causes of Deterioration
3. Condition Survey
4. Tests
5. Materials
6. Case study
1.INTRODUCTION
Repair
Strengthening
2.CAUSES OF DETERIORATION
Human Error
Design Mistakes
• Inadequate structural design
• Poor Design Detail
Construction errors
• Improper alignment of formwork
• Improper compaction
• Improper curing
• Premature removal of shores
2.CAUSES OF DETERIORATION
Chemical causes
Acid attack
Sulfate attack
Chloride Attack
Carbonation
2.CAUSES OF DETERIORATION
Chemical causes
Acid attack
Sulfate attack
Chloride Attack
Carbonation
2.CAUSES OF DETERIORATION
Chemical causes
Acid attack
Sulfate attack
Chloride Attack
Carbonation
2.CAUSES OF DETERIORATION
Chemical causes
Acid attack
Sulfate attack
Chloride Attack
Carbonation
2.CAUSES OF DETERIORATION
Thermal Causes
Freezing & Thawing
Plastic shrinkage
2.CAUSES OF DETERIORATION
Thermal Causes
Freezing & Thawing
Plastic shrinkage
2.CAUSES OF DETERIORATION
Mechanical Causes
Abrasion & Erosion
2.CAUSES OF DETERIORATION
Special Causes
Overload
Differential settlement
2.CAUSES OF DETERIORATION
Special Causes
Overload
Differential settlement
3.Condition survey
 Outlines:
3.Condition survey
Introduction
Stages
a) Primary Inspection
b) Planning Stage
i. Grouping of structural
members.
ii. Classification of damage .
c) Visual Inspection
3.Condition survey
Introduction
Stages
a)Primary Inspection
b) Planning Stage
i. Grouping of structural
members.
ii. Classification of damage .
c) Visual Inspection
3.Condition survey
Introduction
Stages
a) Primary Inspection
b) Planning Stage
i. Grouping of structural
members.
ii. Classification of damage .
c) Visual Inspection
Class of damage
Repair
classification
Class 0
cosmetic
General observation on condition of concrete
Only final finishes disfigured. No structural
distress observed.
Class 1
superficial
Final finishes/skin alone damaged. No structural
cracks observed. Carbonation depths not yet
reached reinforcement level.
Class 2
Patch repair
Minor structural cracks observed and /or
carbonation depths reached reinforcement level.
Class 3
Principal Repair
Class 4
Major Repair
Spalling of cover concrete, major structural
cracks, including cracking along reinforcement
due to corrosion or otherwise leading to
substantial reduction of load carrying capacity.
Major structural loss necessitating replacement of
the structural member
3.Condition survey
Introduction
Stages
a) Primary Inspection
b) Planning Stage
i. Grouping of structural
members.
ii. Classification of damage .
c)Visual Inspection
3.Condition survey
Types of Cracks and their pattern:
1.Plastic shrinkage crack
2. Steel corrosion crack
3. structural cracks
a) Flextural cracks
b) Shear cracks
c) Torsional cracks
d) Tension cracks
3.Condition survey
Types of Cracks and their pattern:
1. Plastic shrinkage crack
2.Steel corrosion crack
3. structural cracks
a) Flexural cracks
b) Shear cracks
c) Torsional cracks
d) Tension cracks
3.Condition survey
Types of Cracks and their pattern:
1. Plastic shrinkage crack
2. Steel corrosion crack
3.structural cracks
a)Flexural cracks
b) Shear cracks
c) Torsional cracks
d) Tension cracks
3.Condition survey
Types of Cracks and their pattern:
1. Plastic shrinkage crack
2. Steel corrosion crack
3.structural cracks
a) Flexural cracks
b)Shear cracks
c) Torsional cracks
d) Tension cracks
3.Condition survey
Types of Cracks and their pattern:
1. Plastic shrinkage crack
2. Steel corrosion crack
3.structural cracks
a) Flexural cracks
b) Shear cracks
c)Torsional cracks
d) Tension cracks
3.Condition survey
Types of Cracks and their pattern:
1. Plastic shrinkage crack
2. Steel corrosion crack
3.structural cracks
a) Flexural cracks
b) Shear cracks
c) Torsional cracks
d)Tension cracks
TESTS
Destructive
Tests
PARTIALLY
DESTRUCTIVE
TEST
Non-Destructive
Tests
DESTRUCTIVE TEST
Comp.
Test
Tensile
Test
Bond
Test
PARTIALLY
DESTRUCTIVE TEST
Load
Test
Pull-off
Test
Core
Test
Non-Destructive
Test
HALF-CELL
ELECTRICAL
POTENTIAL
SCHMIDT
REBOUND
HAMMER
ULTRASONI
C PULSE
VELOSITY
RADIOGRAPHIC
TESTING
ELECTROMAGNETIC
METHODS
PENETRATION
RESISTANCE
Petrographic
Analysis of
Hardened
Concrete
HALF-CELL ELECTRICAL POTENTIAL METHOD
non-destructive survey method provides key information in corrosion
evaluation.
How to Perform Half Cell Corrosion Mapping
Measurement Points:
• Rebar Connection
• Electrical Connection to Voltmeter
• Pre-wetting the surface
Perform Measurements
Potential
Chance of re-bar
difference levels
being corroded
(mv)
visible evidence
less than –500
of corrosion
-350 to -500
95%
-200 to -350
50%
More than -200
5%
[Risk of corrosion against the potential difference readings]
Influencing Parameters
• Electrical resistivity of concrete
• Density of concrete
• Cover thickness
• Epoxy coatings
The test does not actual corrosion rate or whether corrosion activity has
already started, but it indicates the probability of the corrosion activity
depending upon the actual surrounding conditions and no information
relating to corrosion kinetics can be obtained.
SCHMIDT REBOUND HAMMER TEST
• The Schmidt rebound hammer is principally a surface hardness tester.
• There is little apparent theoretical relationship between the strength of
concrete and the rebound number of the hammer.
• empirical correlations have been established between strength properties
and the rebound number.
GENERAL PROCEDURE FOR SCHMIDT REBOUND HAMMER
TEST
APPLICATIONS OF SCHMIDT REBOUND HAMMER TEST
• the hammer is perpendicular to the surface under test.
• Prepare a number of 150 mm × 300 mm cylinders (or 150 mm3 cube
specimens).
• testing machine under an initial load of approximately 15% of the
ultimate load to restrain the specimen.
• take 5 readings on each of the 4 molded faces without testing the same
spot twice.
• Test the cylinders to failure in compression and plot the rebound
numbers against the compressive strengths on a graph.
RANGE AND LIMITATIONS OF SCHMIDT REBOUND
HAMMER TEST
• Smoothness of the test surface.
• . Size, shape and rigidity of the specimen.
• Age of the specimen.
• Surface and internal moisture conditions of concrete.
• Type of coarse aggregate.
• Type of cement.
• Carbonation of the concrete surface.
ULTRA SONIC PULSE VELOSITY TEST
The principle of the UPV is measuring the
time of propagation of a wave train
between
two
points.
The
transducer
produces ultrasound pulse and measures
the time required for the wave to reach the
receiver. Knowing the distance from the
transmitter to the receiver (width of
structure), it is possible to know the velocity
ν of the wave in the medium.
Pulse Velocity
(Km/sec.)
Above 4.5
3.5 to 2.5
3 to 3.5
Below 3.0
Concrete Quality
(Grading)
Excellent
Good
Medium
Doubtful
There are three methods used for this test:
(a)Direct method.
(b)semi-Direct method.
(c)Indirect method
CORE TEST
• concrete cores are used for testing of actual properties of concrete in existing
structures such as strength, permeability, chemical analysis, carbonation etc.
•4.MATERIAL SELECTION
Selection of repair material is one of the most important tasks for
ensuring durable and trustworthy repair.
Though the pre-requisite for a sound repair system is the detailed
investigation and determining the exact cause of distress, yet an
understanding of the process of deterioration of the repair materials
Essential Parameters For Repair Materials
• Good bond strength with existing substrate
• Low shrinkage properties
• Low air and water permeability
• curing
• Aesthetics to match with surroundings
• Cost
• Availability of material
• Availability of experienced labours
Classification of Materials
Materials
Cementitious
materials
Polymers
materials
Resins
materials
Steel
Cementitious Materials
• Conventional Concrete / Mortar
• Shotcrete
• Dry Pack and Bonded Dry Pack
• Ferro cement
• Preplaced- aggregate concrete
Cementitious Materials
Conventional Concrete / Mortar
Admixtures are frequently used Conventional concrete without
admixtures should not be used in repairs and strengthening .
Conventional concrete is often used in
thick sections and large volumes .
mortar can be placed in thinner sections.
Admixtures Concrete /Mortar
• Mineral Admixtures
• Fly ash
• Silica fumes
Admixtures Concrete /Mortar
• Advanced Cementations Material
• Shrinkage Reducing admixtures
• Accelerating admixtures
• Water-Reducing Concrete Admixtures
Shotcrete
SHOTCRETE
Dry process
SHOTCRETE
Wet process
Polymers Materials
• POLYMER IMPREGNATED CONCRETE (PIC).
• voids is removed under partial vacuum and low viscosity
monomer is diffused through the pores of concrete.
• POLYMER-MODIFIED CONCRETE:
• The process technology of making the latex-modified mortar and
concrete is similar to that of the conventional binding systems.
RESIN MATERIALS
Epoxies
EPOXY MORTAR
• Epoxy mortars consist of
epoxy resins, hardener, and silica sand
advantages of epoxy mortar are:
• Very High Strength Abrasion Resistance
• Good Water Resistance
MODIFIED EPOXY SYSTEMS
• Coal Tar Epoxy System
widely used as water resistant,
improvement of corrosion resistance
of epoxy resin system
MODIFIED EPOXY SYSTEMS
Rubber Additives
These are used to increase
• flexibility
• fatigue resistance
• crack resistance
• energy absorption (toughness) in epoxy resins
FIBER REINFORCEMENT POLYMER MATERIALS
FIBER REINFORCEMENT POLYMER MATERIALS
• Types of Fibers
Glass Fibers
FIBER REINFORCEMENT POLYMER MATERIALS
• Carbon Fiber
FIBER REINFORCEMENT POLYMER MATERIALS
• Aramid Fiber
FIBER REINFORCEMENT POLYMER MATERIALS
FIBER REINFORCEMENT POLYMER MATERIALS
• Fiber orientation
Unidirectional
woven
random
FIBER REINFORCEMENT POLYMER MATERIALS
Types of Matrix
FIBER REINFORCEMENT POLYMER MATERIALS
Properties of Different Types of Resins
FIBER REINFORCEMENT POLYMER MATERIALS
• Laminates or Strips
Sheets or fabrics
Wet Lay-up
Steel
Composite with concrete
Steel
Plates and angels
CASE STUDY
FOUR-STOREY RC FRAME
RESIDENTIAL QUARTERS AT
MUMBAI
VISUAL OBSERVATIONS
1. Excessive cracking of concrete in RC elements.
2. At many locations the diameter of steel reinforcement reduced by
more than 15% of the original
area provided.
3. Concrete cover on reinforcement was mostly less than the
specified.
4. The diagonal cracks observed in brick masonry walls at many
places.
5. The quality of repairs already carried out is not very good
Cracked cover of concrete in RC slab and Corrosion of
steel reinforcement
Cracked RC Column due to Corrosion of
steel reinforcement
IN-SITU EVALUATION AND LABORATORY TESTING
• Core Test
• The test results were as under-Test Average Value
• Equivalent compressive cube strength 73.29 kg/cm2
• Density of concrete 2231 kg/m3
• Carbonation Test
• Carbonation has taken place beyond the reinforcement levels in
columns, beams and slabs.
• Rebound Hammer Test
The rebound numbers measured on concrete
surfaces of RCC columns, beams and slab. Rebound
values were as under:
• Chemical Analysis of Concrete
a) Water soluble sulphate ions express by weight of cement were
within the permissible value of 4% by weight of cement.
b) Water soluble chloride ions expressed by weight of cement were
0.45% and exceeded permissible limits.
CONCLUSIONS
The main cause for early distress to RCC structures of the building is.
a) Excessive chloride content in concrete.
b) High level of humidity in air combined with hot climate throughout the year
c) Presence of atmospheric CO2 combined with other industrial polluting gases (like
CO2,SO2,CO,SO3,H2S etc), environment is highly acidic causing accelerated
carbonation of concrete and corrosion of reinforcement. Even, rainwater becomes
acidic due to dissolution of such gases and adds to accelerated carbonation.
d) Quality of cover concrete and inadequacy of its thickness is another important factor
for early deterioration of the structures under aggressive environment.
Repair techniques for this case
Concrete Jacketing