CET456 REPAIR AND REHABILITATION OF

BUILDING

Damage diagnosis and assessment

1. Need for Evaluation of Reinforced Concrete Structures
The different types of deterioration get noticed in different forms like cracking, palling, staining
etc. These visual forms indicate the presence of a problem. The symptoms alone are not enough to find
the correct solution, the reason being there could be more than one cause responsible for the particular
symptom. It is imperative to determine and eliminate the cause of the original damage because any repair
that is made on the basis of an incorrect estimation of the cause is likely to damage the repaired concrete
also, resulting in larger and expansive repair of repairs.

1.1. Condition Evaluation of Reinforced Concrete Structures

Condition evaluation is generally carried out under any of the given circumstances Change in resistance
of structure due to deterioration owing to time-depending processes such as corrosion or fatigue Structural
damage due to accidental loadings like earthquake, tsunami, fire, blasts, etc.Structures subjected to
change in use, operational changes or increased load where it is necessary to check the adequacy of the
structure to resist additional loads.

● Condition assessment generally leads to two major findings

● Condition of the structure is satisfactory and requires no further intervention Structures require
any of the following
□ Preservation: The process of maintaining a structure in its present condition and arresting
further deterioration
□ Rehabilitation: The process of repairing or modifying the structure to its desired useful
condition.
□ Repair: The process of replacing or correcting deteriorated, damaged, or faulty materials,
components, or elements of a structure.

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 □ Restoration: the process of re-establishing the materials, form, and appearance of the
structure.
□ Strengthening: The process of increasing the load-resistance capacity of a structure or
portion.
□ Retrofitting: the process of strengthening the structure along with structural system.

Condition assessment of the structure is the systematic and logical examination of the structure to
identify the area and cause of distress.

1.2. The objectives of condition assessment

● To provide insight into the current condition of the structure i.e. to identify the cause & source of
observed distress.
● To assess the extent and development of the deterioration
● To assess the influence of the deterioration on the safety and life expectancy of the structure i.e.
determining the residual strength of structure and its possibility of being repaired.
● To accurately assess the scenario of concrete in structure in terms of its physical, chemical and
electro-chemical properties.
● To prioritize the repair of the distressed elements in order of the seriousness of the deterioration.
● To chart out an effective and economically feasible concrete-repair program.

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 1.3. Stages of conditional Assessment
● Preliminary investigation
● Detailed investigation

1.3.1. Preliminary investigation:

It helps to understand the past record of the structure in terms of the distresses and repairs
carried out if any. It also helps to assess the apparent physical condition, robustness, structural
integrity and strength of structure.

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 1.3.2. The main objectives of preliminary investigation
● To obtain the initial information regarding the condition of structure by studying past records
based on the information obtained from the owners, occupants of the buildings and general
public.
● To get an overview of the existing state of the structure to obtain a reliable assessment of the
available structural capacity.
● To understand the type and the seriousness of the problems affecting the structure
● To determine the feasibility of performing the required repairs and rehabilitation works.
● To identify the need for detailed investigation
● To plan the necessary site preparations, procurement of the required field-testing equipment and
tools for sampling.

Preliminary investigation can be broadly classified into

● Review of records,
● Condition survey.

1.3.3. Review of record:

A thorough review of all pertinent data related to design, construction and service life of the structure is
assessed in evaluating the condition of structure. The list of records which should be gathered includes:

❖ The original plans & specifications

❖ The original design and construction documents like design, drawings, specifications, structural
calculations, and record of modification if any
❖ A record of materials used in construction-tests reports of the material
❖ Building inspection records
❖ Design construction and testing personnel involved
❖ Service history of building-record of maintenance, repairs, alterations, settlement, weather record
and seismic-activity record.
1.3.4. Condition survey:
Condition survey is a qualitative and systematic inspection that forms the keystep for making the
correct evaluation of the distressed structure. In simple words, it is a rapid visual inspection of the
structure which provides a fair idea about the signs of distress and deterioration, the structural and non-
structural deficiencies, irregularities in building configuration and construction defects.

The condition survey when carried out as a part of preliminary investigation is just a rapid visual
inspection. Limited non-destructive and destructive testing techniques can sometimes be used to confirm
the measurements and observations made during the condition survey. This can include non-destructive
physical testing such as visual inspection to find cracks and staining, localization of voids, measurement
of the concrete cover around the reinforcement, measuring the size of cracks, estimate the widths and
length of the cracks, to determine the movement the movement in cracks, i.e. if the cracks are active or
passive, to record the located cracks on structural plan or grid sheet.

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Things one must look for while carrying out the visual inspection

● Verification of information collected during desk study, i.e., to verify if the on-site conditions are
in conformance to the available designs and drawings.
● Structural framing
● Record of the existing condition of concrete, i.e., note of construction faults like bugholes, cold
joints, honeycombing, exposed reinforcement, corrosion etc.
● Presence of cracking (location, depth, width, nature of cracking, the surface appearance of the
cracks, current state of activity, physical state of concrete when the cracking occurred)
● Surface appearance of cracks (pattern of cracks, length of cracks, short cracks or interconnected)
● The surface appearance of concrete (texture, discolouration, staining, spalling,delamination and
erosion)
● Sources of leakage or seepage due to concealed services, through joints or cracks,inadequate
systems of rain water disposal, improper terrace slope or absence of rain water pipes, ponding of
water and discoloration due to dampness must be noted.
● Movements of structures in the form of excessive deflections, heaving or settlement.
● Damage to structural elements & finishes like blistering membranes and coatings.

1.3.5. Rapid Visual Inspection (RVI):

RVI is carried out to make a thorough and accurate inspection of the building. This kind of
inspection is carried out in any of the following situations:

❖ . To carry out the periodic structural inspection of the buildings.

❖ . To have a quick inspection of the structure to determine if it is unsafe for the inhabitants in case
of severe damage due to fire or natural calamity.

2. Overall building assessment:

In overall building assessment, the inspector must look for any abnormal deformation or
deflection. Check for any leaning of the building, soil displacement under foundations, load bearing wall
or settlement of the floor. Water leakage, ponding areas, areas of poor drainage or other indications of
water problems must be noted. Evidence of any type of chemical deterioration on the building must also
be noted.

2.1. Component assessment:

The inspector needs to focus on specific building elements for presence of any kind of defects or
deterioration. The component assessment has to be properly documented along with sketches showing
particular distressed structural member, location, classification and extent of distress, besides the
photographic record of defects like cracks, spalls and other surface defects, honeycombing, corrosion of
reinforcement, loss of c/s, deflections and other misalignments.

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3. Output of preliminary Investigation
The major inferences that can be drawn after the preliminary investigation include the following:

● Description of the actual condition of the existing structure including the location, extent and
nature of the deterioration or distress.
● A quality classification of the components or the whole structure and the repair/rehabilitation
option based on condition and degree of damage.
● Is there any need for detailed investigation

4. Detailed Investigation:
The detailed investigation is required to be conducted when the pertinent data like the original
construction drawings and design of the structure, foundation details and structural details are not
available. It is also required when the information furnished by the preliminary investigation is not
conclusive and further investigation is required to design a repair/retrofitting works. The detailed
investigation may not necessarily be done to document the condition of the whole building, but only the
elements subjected to investigation in detail based on recommendations of preliminary investigation.

4.1 Scope and methodology of detailed investigation

1. Procure complete documentation of information related to design, construction, maintenance and
the history of the building.
2. Assess the structural adequacy by checking the structural plans and calculations and verifying
the same by measuring the dimensions of the elements of the existing building on site.
3. Carry out the tests on the materials used like concrete, steel and masonry with the help of
destructive, semi-destructive and non-destructive test methods in the field and also laboratory
investigation of the samples collected from the field.
4. Conduct all the necessary geotechnical investigations to collect data of the soil profile and its
characterization.
5. Carry out load tests on parts of the building, if necessary.

The detailed investigation generally involves a wide range and types of sampling and testing. The
selection of the testing methods however depends upon the type, extent of deterioration and the
importance of the structure. The use of various testing methods like destructive tests, semi destructive
becomes necessary at the stage of detailed investigation. These tests are required to be conducted to
determine typical parameters like:

● Verification/identification of current geometry/member size

● Estimation of the in-situ compressive strength of concrete
● Detection of hidden flaws and defects, presence of cracks, voids and other imperfections
● Location and spacing of embedded items like reinforcement profile, measure of cover and bar
diameter, etc.
● Assessing the extent of damage, i.e., corrosion, chemical attack (chlorides, sulphate, alkali
content) and degree of carbonation
● Determining the material properties, i.e., concrete and reinforcing steel properties
● Mapping of the cracks
● Installation of instruments to monitor the changes in structure of concrete over time, movement of
cracks

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 5. Rebound Hammer test:
The rebound hammer also called Schmidt hammer – a Swiss hammer is one of the oldest & best known
methods for comparing the concrete in different parts of structure. A simple hand held device
measures the hardness of concrete surface through a rebound of a spring loaded mass rebound measured
on a graduated scale giving a “Rebound Number” Larger the rebound number - harder the surface
concrete. Most hammers come with a calibration chart relating the compressive strength of
concrete and rebound number

Principle
The rebound of an elastic mass depends on the hardness of the surface against which its mass strikes

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 ● When the plunger of the rebound hammer is pressed against the surface of the concrete, the
Spring-controlled mass rebounds and the extent of such a rebound depends upon the surface
hardness of the concrete.
● The surface hardness and therefore the rebound is taken to be related to the compressive
strength of the concrete
● The rebound value is read from a graduated scale and is designated as the rebound number
or rebound index.
● The compressive strength can be read directly from the graph provided on the body of the
hammer

Steps to be followed
• All members to be marked with well defined grid points - spacing of 200 - 300 mm
preferred
• Each grid point to be cleaned and surface smoothened
• A minimum of 6 readings to be obtained at each point and average considered omitting
too low and too high values.
• Do not repeat impacts on same point
• A statistical analysis gives indication on overall quality and variability
• Delamination of cover concrete can be identified with low and very low rebound
numbers
• Very high rebound numbers greater than 50- may represent carbonated concrete - to be
confirmed by chemical test

Points to Remember in Rebound Hammer Test

● The concrete surface should be smooth, clean and dry.
● Loose particles should be rubbed off from the concrete surface with a grinding wheel or stone,
before hammer testing.
● Rebound hammer tests should not be conducted on rough surfaces as a result of incomplete
compaction, loss of grout, spalled or tooled concrete surface.
● The point of impact of the rebound hammer on the concrete surface should be at least 20 mm
away from edge or shape discontinuity.
● Minimum Six readings of rebound number is taken at each point of testing and an average of
value of the readings is taken as rebound index for the corresponding point of observation on
concrete surface.

Application: used for:

● Assessing the compressive strength of concrete with the help of suitable co-relations
between rebound index and compressive strength
● Assessing the uniformity of the concrete
● Assessing the quality of concrete in relation to the standard requirements
● Assessing the quality of one element of concrete in relation to another.

Advantage:
● It is simple & quick method.

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 ● A large number of measurements can be rapidly taken so as to map large exposed areas of
concrete

Limitation:
Results are affected by the angle of test, surface smoothness and mix proportions of concrete. It
does not provide a reliable prediction of the strength of concrete. The possible error may be up to ± 25%

Factors affecting rebound number readings

• Mix Characteristics- Cement type and content and coarse aggregate content.
• Angle of inclination of hammer
• Member Characteristics- Mass, compaction and surface type
• Age of concrete and Rate of hardening, curing type
• Surface texture
• Concrete mix characteristics
• Carbonated concrete, and
• Moisture content

6. Ultrasonic pulse Velocity (USPV) test

It is the most widely used test in evaluation of in-situ concrete. The ultrasonic pulse velocity method
is used for non-destructive testing of plain, reinforced and prestressed concrete whether it is
precast or cast in-situ

Principle
The method is based on the principle that the velocity of an ultrasonic pulse through any material
depends upon the density, modulus of elasticity, the presence of the reinforcing steel & poision’s ratio
of the material.

Application: used to find:

● The Homogeneity of the Concrete

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 ● The Presence of Cracks, Voids and other Imperfections
● Changes in the Structure of the Concrete Caused by the Exposure Condition,
Corrosion, Wear etc. which may occur with time,
● The Quality of the Concrete in Relation to the Specified Standard Requirements.
● The Quality of One Element of Concrete in Relation to the Another.
● The Values of the Dynamic Elastic Modulus of the Concrete.

Procedure
• Divide the members into well defined grid points
• Each grid point is prepared to obtain smooth surface - a thorough cleaning
• Application of acoustical coupling - grease, thick oil, petroleum jelly may be done
• Transmitting the pulses by placing the transmitter and receiving at other end
• Recording the transit time displayed by the instrument - a reliable steady reading to be
recorded
• Measurement of length between transmitter and receiver
• Calculation of velocity, V = L / T ( L – Path length, T-time)

There are three possible ways of measuring pulse velocity through concrete :

1. Direct Transmission (Cross Probing) through Concrete :

In this method transducers are held on opposite face of the concrete specimen under test.
The method is most commonly used and is to be preferred to the other two methods because this
results in maximum sensitivity and provides a well-defined path length.

b. Semi-direct Transmission through Concrete:

Sometimes one of the face of the concrete specimen under test is not accessible, in that case we
have to apply semi-direct method .In this method, the sensitivity will be smaller than cross probing and
the path length is not clearly defined.

c. Indirect Transmission (Surface Probing) through Concrete:

This method of pulse transmission is used when only one face of concrete is accessible.
Surface probing is the least satisfactory of the three methods because the pulse velocity measurements

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indicate the quality of concrete only near the surface and do not give information about deeper layers of
concrete. The weaker concrete that may be below a strong surface cannot be detected. Also in this
method path length is less well defined.

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Advantage:
The test equipment is portable, can be performed quickly and has sufficient power to penetrate about 11m
in good continuous concrete.

Limitations: The test does not give the precise strength of concrete. A large number of factors affect
the values of pulse velocity that include surface condition and moisture content, temperature of concrete,
micro-cracks in concrete, age of concrete, presence of steel rfm, aggregate type, content & size. When the
concrete is subjected to abnormally high stress, pulse velocity value is reduced due to development of
micro-cracks

7. Windsor Probe test

It is one of the most well-known penetration resistance methods. It is based on the determination of
the depth of the penetration of probes (steel rods or pins) into the concrete. The apparatus used in this
method is the Windsor probe which is a special gun .

The principle
The penetration depth is inversely proportional to the compressive strength of concrete, but the relation
depends on the hardness of aggregate.

The minimum distance between the edge of the concrete member should be of the order of 150 mm and
that between the test positions be 200 mm. The penetration will be effected by the presence of reinforcing

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bars within the zone of influence of the penetrating probe. Thus the location of the reinforcing steel
should be determined prior to selecting test locations.

Manufacturers provide calibration charts of strength versus penetration for the normal probe for
aggregates with hardness between 3 and 7 on Mohrs scale. However, the penetration resistance should be
correlated with the compressive strength of a standard test specimen or core of the actual concrete used.

Application:
● Form Removal
● Structural Analysis
● Light-weight concrete strength determination
● Standard concrete strength determination
● High-strength concrete strength determination
● High-precision determination

Advantage:
● The test is relatively quick and the result is achieved immediately provided an appropriate
correlation curve is available.
● The probe is simple to operate, requires little maintenance except cleaning the barrel and
is not sensitive to operator technique
● Access is only needed to one surface.
● The correlation with concrete strength is affected by a relatively small number of
variables.
● The test result is likely to represent the concrete at a depth of from 25 mm to 75 mm
from the surface rather than just the property of the surface layer as in the Schmidt
rebound test.

Limitation:
● The minimum acceptable distance from a test location to any edges of the concrete
member or between two test locations is of the order of 150 mm to 200 mm.
● The minimum thickness of the member, which can be tested, is about three times the
expected depth of probe penetration.
● The distance from reinforcement can also have an effect on the depth of probe penetration
especially when the distance is less than about 100 mm.
● The test is limited to <40 MPa and if two different powder levels are used in an
investigation to accommodate a larger range of concrete strengths, the
● correlation procedure becomes complicated.
● The test leaves an 8 mm hole in the concrete where the probe penetrated and, in older
concrete, the area around the point of penetration is heavily fractured.
● On an exposed face the probes have to be removed and the damaged area repaired

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 Semi-destructive tests for strength estimation of concrete

8. . Pullout test
There are two options for the pullout test:

DANISH LOK TEST which requires that the head be cast into the concrete at the time of
construction. This test gives a good indication of near surface compressive strength. Building Research
Establishment,

Building Research Establishment, UK (BRE) PULL OUT involves drilling a hole and inserting
a “fixing” which is pulled out. The advantage of this test is that it does not require a head to be cast
into the concrete during construction. The disadvantage is that the test really measures tensile
strength and is then calibrated to compressive strength.

The pullout test is a test that falls in the transition area between a destructive test and a
non-destructive test. It is destructive in the sense that a relatively large volume of the concrete is
damaged but non-destructive because the damage can be repaired.

The pullout test measures the force required to pull an embedded metal insert with an enlarged
head from a concrete specimen or a structure. The insert is pulled by a loading ram seated on a bearing
ring that is concentric with the insert shaft. The bearing ring transmits the reaction force to the concrete.

The pullout test is widely used during construction to estimate the in-place strength of
concrete to help decide whether critical activities such as form removal, application of post
tensioning, or termination of cold weather protection can proceed. Since the compressive strength is
usually required to evaluate structural safety, the ultimate pullout load measured during the in-place test is
converted to an equivalent compressive strength by means of a previously established correlation
relationship.

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Application:
Assessment of the bonding strength of all kinds of applied coatings & repairs.

Advantage:
The test is simple & quick to perform. Damage caused to concrete is minor and can be repaired easily.

Limitation:
The main limitation is the curing time of the adhesive which is 24 hours. During testing if the adhesive
fails because of its inferior quality, then the entire test result becomes meaningless. Hence, six discs are to
be used to determine the strength.

9. Core Test:
Condition of concrete in the structure after construction can be assessed directly by core drilling
at required location or at suspected location. The core samples obtained are then taken for visual
inspection and compression test to determine maximum compressive strength. The core drilling and
compression testing shall be done in accordance with ASTM Method C 42-87.

The extracted cores can be subjected to a series of tests and serve multiple functions such as:

● confirming the findings of the non-destructive test

● identifying the presence of deleterious matter in the concrete
● ascertaining the strength of the concrete for design purposes
● predicting the potential durability of the concrete
● confirming the mix composition of the concrete for dispute resolution
● determining specific properties of the concrete not attainable by nondestructive methods such as
intrinsic permeability.

The selection of location of the cores is made after conducting NDT which can give guidance on
the most suitable area of extraction. Cutting of cores requires special equipment. Most of the cores are
either 100 mm or 150 mm in diameter. If the core size is small in relation to the maximum aggregate size,
then care must be taken during analysis. The choice of the core diameter will be influenced by the length
of the specimen. It is generally accepted that cores for compression testing should have a length/diameter
ratio between 1 and 2. T

Application:
The core samples can also be used for the following:

1.Standard and density determination

2.Depth of carbonation of concrete

3.Chemical analysis

4. Water/gas permeability

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5. Petrographic analysis

6.Chloride permeability test

Advantage:
Cores provide the simplest method of obtaining samples of in-situ concrete. chemical analysis can be
performed on the remains of crushed core. Visual inspection of the interior of concrete can prove to be
very valuable where no records of concrete are available.

Limitations:
The main limitation is the cost and inconvenience, damage and localized nature of the results. The test is
possible only if the quality of concrete is reasonably good in the structure that is tested. If the quality is
poor, then core samples will be vulnerable to damage during coring or testing operation.

Chemical Tests of concrete

Chemical tests of the concrete subjected to the environmental attack can provide a great deal of
information regarding the exact cause of the damage. It is a known fact that the corrosion of the
reinforcing steel occurs when the protective passivating film on the steel surface formed due to the high
alkaline condition of the concrete, is destroyed by carbonation or chloride diffusion. Chemical tests like
carbonation test and chloride content test help to determine the amount of diffusion of these atmospheric
pollutants inside the concrete surface

10. Chloride PenetrationTest

The principle
The rapid chloride permeability test of concrete is an in-situ test to check concrete permeability. This test
is very simple and gives results very fast. The rapid chloride permeability test of concrete is conducted to
check the Concrete’s ability to Resist Chloride Ion Penetration.

In this test, the electrical Indication capacity of concrete to Resist Chloride Ion Penetration is checked.
This test enables the prediction of the service life of concrete structures It can also be utilized for
durability-based quality control purposes. In this test, the steady voltage (V) is applied to a concrete
specimen for 6 hours, and the current (i) going through the concrete is recorded to find the coulombs

As we know, electric Current is measured in amperes. A coulomb is an ampere – second;which

implies 1 ampere passed through the concrete specimen in 1 second is a 1 coulomb, and the charge passed
in 60 seconds would be 60 coulombs.

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 The more permeable the concrete, the higher the coulombs; the less porous the concrete, the
lower the coulombs.

Apparatus of Rapid Chloride Permeability Test:

This test apparatus comprises two reservoirs.One of them has 3 % of NaCl solution and another
reservoir has 0.3 M NaOH Solution, Concrete having a thickness of 50 millimeters and diameter 90 to
100 millimeters is used as a test specimen.

Test Procedure
The concrete specimen having a diameter of 100 millimeters and thickness of 50 millimeters is
cast and saturated. The concrete sample is placed in between the two reservoirs having NaCl solution in
one reservoir and NaOH solution in the other reservoir.

These reservoirs are connected to the DC supply and the voltage of 60 Volts is applied to the concrete
specimen at both ends for six hours.

Now measure the current going through the concrete at various time intervals.

The current going through the concrete is calculated by an LCD which is connected to the cell.

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11. Carbonation Test
For the carbonation induced corrosion, determination of the depth up to which the concrete has
become acidic becomes very crucial. In this test, the assessment of the carbonation depth is done by
spraying solution of Phenolphthalein indicator on concrete surface. This solution appears pink
when it comes in contact with un-carbonated concrete with the pH values above 9, or else it appears
colorless when it comes in contact with carbonated concrete, i.e., Concrete with lower values of pH-
acidic

The test is most commonly carried out by spraying 0.2% solution of phenolphthalein in ethanol
on freshly exposed surfaces of concrete broken from the structure or on split cores. Sometimes the powder
from drill holes can also be sprayed or allowed to fall on phenolphthalein impregnated paper. The test
must be applied only to freshly exposed surfaces, because the reaction with atmospheric carbon dioxide
starts immediately.

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 12. CARBONATION DEPTH MEASUREMENT TEST
Principle
Carbonation of concrete occurs when the carbon dioxide, in the atmosphere in the presence of
moisture, reacts with hydrated cement minerals to produce carbonates, e.g. calcium carbonate.
Carbonation penetrates below the exposed surface of concrete extremely slowly. The time required for
carbonation can be estimated knowing the concrete grade and using the following equation:

where t is the time for carbonation, d is the concrete cover, k is the permeability.

The significance of carbonation is that the usual protection of the reinforcing steel generally present in
concrete due to the alkaline conditions caused by hydrated cement paste is neutralized by carbonation.

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Thus, if the entire concrete cover over the reinforcing steel is carbonated, corrosion of the steel would
occur if moisture and oxygen could reach the steel.

Equipment
If there is a need to physically measure the extent of carbonation it can be determined easily by
spraying a freshly exposed surface of the concrete with a 1% phenolphthalein solution. The calcium
hydroxide is coloured pink while the carbonated portion is uncoloured.

General Procedure The 1% phenolthalein solution is made by dissolving 1gm of phenolthalein in

90 cc of ethanol. The solution is then made up to 100 cc by adding distilled water. On freshly extracted
cores the core is sprayed with phenolphthalein solution, the depth of the uncoloured layer (the carbonated
layer) from the external surface is measured to the nearest mm at 4 or 8 positions, and the average taken.
If the test is to be done in a drilled hole, the dust is first removed from the hole using an air brush and
again the depth of the uncoloured layer measured at 4 or 8 positions and the average taken. If the concrete
still retains its alkaline characteristic, the 79 colour of the concrete will change to purple. If carbonation
has taken place the pH will have changed to 7 (i.e. neutral condition) and there will be no colour change.
REFER THE PREVIOUS TEST

Another formula, which can be used to estimate the depth of carbonation, utilizes the age of the
building, the water-to-cement ratio and a constant, which varies depending on the surface coating on the
concrete.

R varies depending on the surface coating on the concrete (β) and whether the concrete has been
in external or internal service (α).

The phenolphthalein test is a simple and cheap method of determining the depth of carbonation in
concrete and provides information on the risk of reinforcement corrosion taking place. The only
limitation is the minor amount of damage done to the concrete surface by drilling or coring

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Question Bank

1. Explain the need for Evaluation of Reinforced Concrete Structures

2. Write a note on Condition assessment of the structure
3. List down the objectives of condition assessment
4. Explain the stages of condition assessment (14 Marks)
5. In what way carbonation of concrete affect the structure
6. Enumerate the significance of primary investigation in rehabilitation of Structures
7. Explain the significance of visual inspection
8. Explain the Scope and methodology of detailed investigation
9. Explain the Rebound Hammer test:
10. Explain theUltrasonic pulse Velocity (USPV) test
11. Explain the Windsor Probe test
12. Explain the Pull Off test
13. Explain the Core test
14. Explain the Chloride penetration test
15. Explain the carbonation test

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