The document discusses repair and rehabilitation of concrete structures. It describes various causes of distress in concrete structures including structural causes, errors in design/construction, chemical reactions, and weathering. It then outlines the evaluation process for repair projects, including visual inspection, non-destructive testing, and laboratory testing to determine the extent of damage and appropriate repair methods. Specific causes of reinforcement corrosion like cracks, moisture, and concrete permeability are explained along with remedial measures.
Quality Control in Concrete and Durability factors : An overviewbybyRAJESH PRASAD,IRSE, CPM/M, RVNL. KOLKATA. An interesting and informative presentation....
Quality Control in Concrete and Durability factors : An overviewbybyRAJESH PRASAD,IRSE, CPM/M, RVNL. KOLKATA. An interesting and informative presentation....
A crack is a complete or incomplete separation of concrete into two or more parts produced by breaking or fracturing.
Cracks are one kind of universal problems of concrete construction as it affects the building artistic and it also destroys the wall’s integrity, affects the structure safety and even reduce the durability of structure
Carbon dioxide penetrates into the concrete through the cracks and speed up carbonation around the cracks, thus shortening the structure usage.
The cracks in the concrete wall would cause the leakage of the building; it reduces the stiffness, durability and seismic performance of buildings.
Cracks on the wall surface damage to the later rendering, will affect to the appearance.
Concrete is the most widely used construction material in India with annual consumption exceeding 100 million cubic meters.
High performance concrete is a concrete in which certain characteristics are developed for a particular application and environment, so that it will give excellent performance in the structure in which it will be placed.
A high-strength concrete is always a high performance concrete, but a high-performance concrete is not always a high-strength concrete.
non destructive concrete testing equipment
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Rebound hammer method
Pull out test method
Ultrasonic pulse velocity method
Radioactive methods
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This presentation gives a brief introduction on FRC's history, definition and why is it used. Types of FRC's and it's applications is explained in detail in later stages.Also, it covers various properties that affects FRC and a Case study in end.
A crack is a complete or incomplete separation of concrete into two or more parts produced by breaking or fracturing.
Cracks are one kind of universal problems of concrete construction as it affects the building artistic and it also destroys the wall’s integrity, affects the structure safety and even reduce the durability of structure
Carbon dioxide penetrates into the concrete through the cracks and speed up carbonation around the cracks, thus shortening the structure usage.
The cracks in the concrete wall would cause the leakage of the building; it reduces the stiffness, durability and seismic performance of buildings.
Cracks on the wall surface damage to the later rendering, will affect to the appearance.
Concrete is the most widely used construction material in India with annual consumption exceeding 100 million cubic meters.
High performance concrete is a concrete in which certain characteristics are developed for a particular application and environment, so that it will give excellent performance in the structure in which it will be placed.
A high-strength concrete is always a high performance concrete, but a high-performance concrete is not always a high-strength concrete.
non destructive concrete testing equipment
non destructive concrete testing methods
non destructive test Penetration method
Rebound hammer method
Pull out test method
Ultrasonic pulse velocity method
Radioactive methods
methods of testing concrete
concrete strength testing methods
types of non destructive testing
non destructive concrete testing equipment
concrete tests pdf
destructive and non destructive testing
concrete testing procedures
non destructive test for concrete
destructive and non destructive testing
non destructive testing pdf
types of non destructive testing
non destructive testing methods
non destructive testing methods ppt
This presentation gives a brief introduction on FRC's history, definition and why is it used. Types of FRC's and it's applications is explained in detail in later stages.Also, it covers various properties that affects FRC and a Case study in end.
Unreinforced masonry structures, buildings are highly vulnerable they often cannot withstand the dynamic horizontal loads in case of earthquakes
Soil structures, such as embankments, are subjected to landslides during earthquakes
Hence the necessity to develop efficient methods for the retrofitting of existing buildings and earthworks and of related monitoring systems to possibly prevent the structural damage
For this purpose multifunctional textile structures are being developed for application in construction for the retrofitting of structures and earthworks
It contains details of retrofitting techniques and their application in various aspects in historical monuments. It would help to protect several heritage structures from the devastating effect of the earthquake. Some applications are also helpful too counter act the severe effect of the wind load. There are many historical heritages especially in India, are reopened to the public after being retrofitted and renovated.
Paste Viscosity!
Attained by one of three means:
High cement content
High content of Fly Ash, Silica Fume etc
Use of Viscosity Modifying Admixture
Also low water content using HRWR
Cracks on concrete.
How to catergorized cracks on newly poured concrete
Thermal cracks
Mass concrete
Fresh concrete
Cracks on concrete have many causes. They may affect appearance only, or it may indicate significant structural distress
Suicide Prevention through Architecture (Building) and City PlanningGAURAV. H .TANDON
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Digital Detox for Sustainability: Unplugging/Redesigning technologies of Smart Cities for a Sustainable Future
“How a small Village in Maharashtra, India teaching importance of Digital detoxing to Mega Smart cities of India”
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Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
Event Management System Vb Net Project Report.pdfKamal Acharya
In present era, the scopes of information technology growing with a very fast .We do not see any are untouched from this industry. The scope of information technology has become wider includes: Business and industry. Household Business, Communication, Education, Entertainment, Science, Medicine, Engineering, Distance Learning, Weather Forecasting. Carrier Searching and so on.
My project named “Event Management System” is software that store and maintained all events coordinated in college. It also helpful to print related reports. My project will help to record the events coordinated by faculties with their Name, Event subject, date & details in an efficient & effective ways.
In my system we have to make a system by which a user can record all events coordinated by a particular faculty. In our proposed system some more featured are added which differs it from the existing system such as security.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
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Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
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Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
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Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
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• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
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Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
Quality defects in TMT Bars, Possible causes and Potential Solutions.PrashantGoswami42
Maintaining high-quality standards in the production of TMT bars is crucial for ensuring structural integrity in construction. Addressing common defects through careful monitoring, standardized processes, and advanced technology can significantly improve the quality of TMT bars. Continuous training and adherence to quality control measures will also play a pivotal role in minimizing these defects.
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The Division of Vaccine and Immunization is facing increasing difficulty monitoring vaccines and other commodities distribution once they have been distributed from the national stores. With the introduction of new vaccines, more challenges have been anticipated with this additions posing serious threat to the already over strained vaccine supply chain system in Kenya.
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2. Syllabus
• Distress in structure: Causes and
precautions, damage assessment of structural
elements, repairing techniques and repairing
materials.
3. Distress In Structure
• Distress means Damage
• Concrete may suffer distress or damage during
its life period due to a number of reasons.
Because of the varying conditions under which
it is produced at various locations, the quality
of concrete suffers occasionally either during
production or during service conditions
resulting in distress.
4. Distress In Structure
Causes of distress of concrete:
• Structural causes
– Externally applied loads
– Environmental loads
– Accidents
– Subsidence's, etc.
• Error in design and detailing
• Poor Construction practices
• Construction Overloads
• Drying Shrinkage
• Thermal Stresses
• Chemical Reactions
• Weathering
• Corrosion
6. In addition to the distress in hardened concrete, the
plastic concrete may also suffer damage due to,
• Plastic Shrinkage
• Settlement Cracking
• Early removal of formwork
• Improper design of formwork.
8. Evaluation Procedure for Repair and
Strengthening of Concrete Structures
• Before finalizing any scheme for repairs and
rehabilitation of a distressed concrete structure, the
concerned engineer has to be fully aware of the
causes of causes of distress, extent of damage to the
structure and the present condition of the concrete
in the structure for repairs to be effective and
lasting. The extent of distress has to be categorized
so that the repair schemes can be formulated
according to the distress in a particular structural
element. So that, pre-repair evaluation and
assessment of a structure is pre-requisite for
working out effective repair schemes.
9. Evaluation Procedure for Repair and
Strengthening of Concrete Structures
• Once the repairs have been carried out on a
distressed structure, the post repair evaluation and
assessment of the structure can be carried out for
checking the efficacy of the repair. The post repair
assessment is a tool with the engineer to evaluate
whether the parent material and the repair
material have obtained bond or whether the
cracks or the voids have been filled up by the
grouting materials. Thus, any scheme for effective
repairs can be based on the pre-repair and post-
repair evaluation of concrete structures
10. Tools for Evaluation of Concrete
Structures
• The various tools available for evaluation of concrete
structures are as follows:
• Visual inspection and observations
• Questioning of concerned personnel
• Scrutiny of field data and records
• Design Checks
• Non- destructive testing (NDT)
• Extraction of cores and testing
• Supplementary laboratory techniques
• Load testing of a structural member
• The general approach adopted for pre-repair evaluation
of distressed concrete structures is given below:
11. Visual Inspection and Observations
• The first step in the process of evaluation of a
distressed concrete structure is visual
inspection and observations. A through visual
inspection and observations. A through visual
inspection leads to proper approach to be
adopted during investigation. It determines the
number of field and laboratory tests required to
be carried out. Visual inspection generally
include the study of the following.
12. Visual Inspection and Observations
• Ambient conditions
• Crack width and patterns
• Spelling of Concrete
• Color, texture and rust stains
• Sinking of columns
• Failure of beam-Column junctions.
• Mal-functioning of machinery, structural
components etc.
• Condition of fixtures
• Deposits/ splashes on structural components.
13. Questioning of Personnel/ Scrutiny
of field Data and Records
• The questioning of personnel and the
scrutiny of field data and records is carried
out for the following:
• Grade of concrete adopted
• Cube test results
• Type of material and sources
• Constructional details
• Environmental Conditions
14. Questioning of Personnel/ Scrutiny
of field Data and Records
• The Scrutiny of the grade of concrete and cube
test results brings out adequacy of strength of
concrete and the degree of quality control
exercised during constructions.
• The study of the type of materials used
particularly cement, coarse aggregate, fine
aggregate, additives etc. also focuses the direction
of investigations. The scrutiny of other
constructional details e.g. removal of formwork,
shifting of formwork for slip form construction,
the height of pouring of concrete, use of
compaction devices etc. are useful information for
further investigation in many cases.
15. • Rebound hammer test
• Ultrasonic pulse velocity test
• Pull- out test
• Pull- off test
• Carbonation test
• Cover measurement
• Break off test
• Endoscopy
• Radar techniques
• Rapid chloride, alkali and sulphate kits, etc.
16. Questioning of Personnel/ Scrutiny
of field Data and Records
• Scrutiny of field data and records:
• Design checks:
• Non-Destructive testing (NDT):
• Any visual inspection and scrutiny of the field
data, the in-situ testing is carried as per the
approach finalized. Various in-situ non-
destructive tests available are:
17. • X-ray diffraction analysis
• Differential thermal analysis
• Chloride permeability test
• Optical and Scanning microscopy
• Chloride permeability test.
• Compressive strength, density and modulus of
elasticity determination on core samples, etc.
• Load testing of a structural member:
• Extraction of Cores and testing:
18. In addition to various in-situ tests carried out, it
becomes necessary to support the findings with
laboratory tests
• The laboratory tests generally adopted are:
• Cement Content of Hardened Concrete
• Chemical Analysis
• Chlorides
• Sulphates
• pH
• Nitrates
19. Corrosion of Reinforcement in
Concrete
The damage to the concrete due to corrosion of
reinforcement is considered to be one of the most
serious problems. It is an universal problem and
property worth of crores of rupees is lost every
years. Due to corrosion problem in bridges,
buildings and other RCC structures, India incurs
heavy loss of about Rs. 1500 cores annually.
This paper deals with various causes of corrosion
and remedial measures thereon.
22. Corrosion Process and Mechanism:
• Corrosion of reinforcement steel is a complex
phenomenon involved chemical, electrochemical
and physical process. When reinforcement steel
rusts, the volume of iron oxide formed is 2-3
times greater than the steel corroded, which
results in bursting stresses in the concrete
surrounding the bar. This causes cracking,
spalling and delimination of concrete. Another
consequence of corrosion is reduction in cross-
sectional area of the steel at anode, thus reducing
its loads carrying capacity.
23. Causes of Corrosion and Remedial
Measures
• Various causes of corrosion and remedial measures are
discussed below:
• Presence of Cracks in Concrete: Certain amount of
cracking always occurs in the tension zone of RCC
depending upon the stresses in the reinforcing steel.
Through these cracks, oxygen or sea water ingress into
concrete and set up good environment for corrosion of
reinforcement. Maximum permissible width of elastic
cracks in RCC members would depend upon
environmental and other factors. For normal
environmental conditions, a maximum crack width of
0.3 mm for protected internal members and 0.2 mm for
unprotected external members may be recommended.
25. Causes of Corrosion and Remedial
Measures
• Presence of moisture: Presence of moisture is a
precondition for corrosion to take place because
concrete can act as electrolyte in electrochemical cell
only if it contains some moisture in pores. Corrosion
can neither occurs in dry concrete or in submerged
concrete.
• The worst combination for corrosion to process is when
the concrete is slightly drier than saturated i.e. about 80
- 90 % relative humidity with a low resistivity and the
oxygen can still penetrate to the steel. Hence in high
humidity areas like coastal India, low permeability
concrete is recommended.
26. Causes of Corrosion and Remedial
Measures
Permeability of Concrete:
• This is also an important factor affecting corrosion of reinforcement.
Ingress of moisture, sea water, oxygen, CO2 etc. is easier in porous
concrete than in dense and impermeable concrete. It is worth
mentioning than with each increases of W/C ratio 0.1, permeability of
concrete increases 1.5 times. Poor curring increases permeability 5 to
10 times in comparison to good cured concrete and poor compaction
increases permeability 7 to 10 times in comparison to good compacted
concrete.
• For this consideration, quantity of cement in concrete should not be
less than 350 kg/ m3 and W/C ratio should not exceed 0.55 for ordinary
structures and 0.45 for marine structures. All other normal
requirements of good quality concrete, namely, grading, and
cleanliness of aggregates, through mixing, proper compaction and
curing should be taken care of.
28. Causes of Corrosion and Remedial
Measures
• Carbonation: Hydrated cement paste forms a
thin passivity layer of Gamma iron oxide (Fe2
O3) strongly adhering to the underlying steel
and gives complete protection from reaction
with the oxygen and water, that is from
corrosion.
• Hydration of cement liberates some calcium
hydroxide which sets up a protective alkaline
medium inhibiting electrochemical cell action
and preventing corrosion of reinforcement.
29. Carbonation
• Carbon Dioxide (CO2) from the atmosphere
diffuse inside the concrete, react with calcium
hydroxide (Ca (OH)2) to form calcium carbonate
which is water soluble. This reaction is known as
carbonation. Carbonation lowers the alkalinity of
concrete and reduce its effectiveness as protective
medium. The pH value of pore water in concrete
is generally between 10.5 to 12.0 but if due to
carbonation it is lowered to 9.0 and below, the
medium converts to acidic type and corrosion of
reinforcement begins.
31. Causes of Corrosion and Remedial
Measures
• Chlorides: Chlorides can enter in the concrete
during concreting or during service conditions.
During concreting, the chloride can enter via
aggregates, gauging water and admixtures like
(CaCl2) In service conditions, the chloride ions
entry is due to ingress of sea water, de-icing and
other salts. The chloride ions (Cl-) attack the iron
oxide film leading to corrosion. Chloride ions
activate the surface of the steel to form an anode,
the passivated surface being the cathode. The rate
of corrosion depends upon chloride ion
concentration.
33. Causes of Corrosion and Remedial
Measures
• Sulphate Attack: Solubility sulphates like sodium,
potassium, magnesium and calcium are sometimes present
in soil, ground water or clay bricks, react with tricalcium
aluminate- 3CaO,Al2O3 (C3A) content of cement and
hydraulic lime in the presence of moisture and from
products which occupy much of cement and hydraulic lime
in the presence of moisture and from products which
occupy much bigger volume than the original constituent.
This, expansive reaction results in weakening of concrete,
masonry and plaster and formation of cracks as well as
corrosion of reinforcement.
• Severity of sulphate attack depends upon amount of soluble
sulphate present in soil, water or clay bricks, permeability
of concrete, amount of C3 A content in cement and duration
for which concrete remains damp.
35. Causes of Corrosion and Remedial
Measures
• Alkali Aggregate Reactions: OPC contains alkalies
like sodium oxide (Na2 O) and potassium Oxide (K2O)
to some extent these alkalies chemically reacts with
reactive siliceous minerals in some aggregate and cause
expansion, cracking and disintegration of concrete give
rise to the corrosion of reinforcement.
• Preventive Measure Consists of:
• Avoid use of alkali-reactive aggregate in concrete.
• Cement with alkali content more than 0.6 % should not
be used.
• Portland Pozzolana cement is recommended.
37. Causes of Corrosion and Remedial
Measures
• Inadequacy of Cover: If Concrete cover to
reinforcement is inadequate, reinforcement is liable to get
corroded soon due to various factors such as
Carbonation, ingress of sea water, moisture penetration
etc. It is therefore necessary that RCC works should have
a minimum clear cover as recommended by IS 456:
2000. Reinforcement shall have concrete cover and
thickness of such cover (exclusive of plaster or other
decorative finish) shall be as follows:
38. Causes of Corrosion and Remedial
Measures
• At each end of reinforcing bars not less than 25
mm nor less than twice the dia. of such bar.
• For longitudinal reinforcing bars in column, not
less than dia. of such bar. In case of columns of
dimensions 200 mm or under, whose reinforcing
bars do not exceed 12 mm in dia. a cover of 25 mm
may be used.
• For longitudinal reinforcing bars in beams, not less
than dia. of such bar.
• for tensile, shear, compressive or other
reinforcement in a slab, not less than 15 mm, not
less than dia. of such bar.
39. Causes of Corrosion and Remedial
Measures
• Increased cover thickness may be provided when
surface of concrete members are exposed to the
action of harmful chemicals (as in case of
concrete in contact with earth faces contaminated
with such chemicals) acid vapours, saline
atmosphere, sulphurous smoke etc. and such
increase of cover may be between 15 mm to 40
mm beyond.
• For RCC members totally immersed in sea water,
cover shall be 40 mm more than the normal cover.
41. Causes of Corrosion and Remedial
Measures
• In all such cases cover should not exceed 75 mm.
Based on part research, concrete, cover more than 50
mm is, however, not recommended as it give rise to
increase crack width which may further allow direct
ingress of deleterious materials to the reinforcement.
• Apart from the remedies discussed above other
preventive measures suggested in various literature are:
• Application of protective coating
• Modification of concrete
• Change in metallurgy of reinforcing steel
• Cathodic protection system
42. Causes of Cracks in Concrete
• The principle causes of cracking are discussed below. It will be
benefit of informative to professional working either for
design, construction or maintenance and repair.
• Temperature and Plastic Shrinkage:
• It is often seen relatively straight parallel with the span of
floors. This is mainly with one way slabs for corridors of large
length and is due to inadequate provision of distribution steel.
IS 456-2000, suggests that minimum reinforcement in slabs in
either direction shall not be less than 0.15 % for mild steel
reinforcement and 0.12 % for high strength deformed bars, of
the total cross sectional area, to avoid shrinkage cracks.
43. Causes of Cracks in Concrete
• Plastic shrinkage cracking occurs when subjected to a very rapid loss of
moisture caused by combination of factors which include air and concrete
temperature, relative humidity, and wind velocity at the surface of the
concrete. These factors can combine to cause high rates of surfaces
evaporation in either hot or cold weather.
• When moisture evaporates from the surface of freshly placed concrete
faster than it is replaced by bleeding water, the surface concrete shrinks,
Due to the restraint provide by the concrete below the drying surface
layer, tensile stresses develop in the weak, stiffening plastic concrete,
resulting in shallow cracks of varying depth which may form are often
fairly wide at surface. Plastic shrinkage cracks begins as shallow cracks
but can become full depth cracks.
• It is usual to see a crack parallel to main steel 4 to 7 m apart. This
particularly creates problem when the slab is for terrace as leakage starts
from these cracks only.
44. Cracks Repair By Routing and
Sealing
• The Crack sealers should ensure the structural
integrity and service ability. In addition they
provide protection from the ingress of harmful
liquids and gases.
• Routing and sealing of cracks can be used in
condition requiring remedial repair and where
structural repair is not necessary. The method
consists of enlarging remedial repair and where
structural repair is not necessary. The method
consists of enlarging the crack along its length on
the exposed surface, called chasing or routing,
and sealing it with a suitable joint sealant.
45. Cracks Repair By Routing and
Sealing
• This is a common technique for crack treatment and is
relatively simple in comparison to the procedures and
the training required for epoxy injection. The procedure
is most applicable to flat horizontal surfaces such as
floors and pavements. However, this method can be
accomplished on vertical surfaces as well as on curved
surfaces.
• This method is used to repair both fine pattern cracks
and larger, isolated cracks. A common and effective use
is for waterproofing by sealing cracks on the concrete
surface where water stands, or where hydrostatic
pressure is applied.
46. Cracks Repair By Routing and
Sealing
• The sealant may be of several materials, including
epoxies, silicones, urethanes, polysulfides,
asphaltic materials polymer mortars. Cement
grouts should be avoided due to the likelihood of
cracking. For floors, the sealant should be
sufficiently rigid to support the anticipated traffic.
• The procedure consists of preparing a groove at
the surface ranging in depth, typically from 6 to
25 mm. A concrete saw, hand tools or pneumatic
tools may be used. This groove is then cleaned by
plastic or sir blasting and allowed to dry. A sealant
is placed into the dry groove and allowed to cure.
49. Crack Repair by Stitching
• The stitching procedure consists of drilling holes on
both sides of the cracks, cleaning the holes and
anchoring the legs of the stitching dogs that span the
crack, which either a non-shrink grout or an epoxy-
resin-based bonding system. The stitching dogs should
be variable in length and orientation or both, and should
be so located that the tension transmitted across the
crack is not applied to a single plane but spread over
area.
• Stitching may be used when tensile strength must be
reestablished across major cracks. Stitching a crack
tends to stiffen the structure and the stiffening may
increase the overall structural restraint, causing the
concrete to crack elsewhere.
51. Providing Additional Reinforcement
• The cracked reinforced concrete bridge gird can
be successfully repaired by using epoxy injection
and reinforcing bars. This techniques consists of
sealings the crack, drilling holes of 20 mm
diameter that intersect the crack plane at
approximately 90 0, filling the hole and crack with
injected epoxy and placing a reinforcing bar into
drilled hole. Typically, 12 to 16 mm diameter bars
extending at least 500 mm on each side of the
crack are used. The epoxy bonds the bar to the
sides of the hole. The epoxy used to rebond the
crack should have a very low viscosity.
52. Drilling and Plugging
• This method consists of drilling down the length of the
crack and grouting it to form a key. A hole, typically 50 to
75 mm in diameter should be drilled, centered on and the
following the crack. The drilled hole is then cleaned, made
tight and filled with grout. The grout key prevents
transverse movements of the sections of concrete adjacent
to the crack. The key will also reduce heavy leakage
through the crack and loss of soil from behind a leaking
wall.
• When structural strength is not the criteria but water-
tightness is essential, the drilled hole, should be filled with a
resilient material of low modulus in lieu of grout. If the
keying effect is essential, the resilient material can be
placed in a second hole, the first being grouted.
54. Cracking Repair by Prestressing Steel
• When a major portion of a member is to be
strengthened, or a crack is to be closed, post-
tensioning is often the desirable solution. The
technique uses prestressing strands or bars to
apply a compressive force. Adequate
anchorage must be provided for the
prestressing steel. The method of correction
crack in slab and beam.
56. Cracking Repair By Grouting
• Based on grouting material used, there are
three methods:
• Portland Cement Grouting
• Chemical Grouting
• Epoxy Grouting
57. Portland Cement Grouting
• Wide Cracks, particularly in gravity dams and thick walls
may be repaired by filling with portland cement grout. This
method is effective in preventing water leakage, but will not
structurally bond cracking sections. The procedure consists
of cleaning the concrete along the crack by air jetting or
water jetting; installing grout at suitable intervals, sealing
the crack between the seats with sealant; flushing the crack
to clean it and test the seal; and then grouting the whole
area. Grout mixtures may contain cement and water or
cement plus sand and water, depending upon the width of
the crack. Water reducers or admixtures may be used to
improve the properties of the grout. For large volumes, a
pump is used and for small volumes, a manual injection gun
may be used. After the crack is filled, the pressure should be
maintained to ensure proper penetration of grout.
59. Chemical Grouting
• Chemicals used for grouting are sodium
silicates, urethanes and acrylamides. Two or
more chemicals are combined to form gel, a
solid precipitate or a foam as opposed to
cement grouts that consists of suspension of
solids particles in a fluid. The advantages of
chemical grouts include applicability in moist
environments and their ability to be applied in
very fine cracks.
62. Column Jacketing
• Column Jacketing is done to improve the load carrying
capacity of the column. The procedure followed is:
• Open the footing of the column by excavating soil around
it.
• Remove the plaster from the surface of the column.
• Make the surface of column concrete rough by sand
blasting.
• Remove the corroded bars by cutting them. Add new bars
from footing to the slab as per the instruction of engineers.
• Apply bonding agent on the old concrete for proper
bonding between old and new concrete.
• Erect necessary shuttering around the column.
• Pour minimum M-25 grade of concrete, vibrate and cure it.
64. Beam Jacketing
• Before taking up the strengthening of a beam, the
load acting on it should be reduced by removing
the flooring tiles and bed mortar from the slab.
Props are erected to support the slab. After clipping
off the existing plaster on the beam, additional
longitudinal bars at the bottom of the beam to-
geather with new stirrups are provided. Stirrups are
inserted by making holes from the slab. The
longitudinal bars are passed through the supporting
columns through holes of appropriate diameter
drilled in the columns. The spaces between bars
and surrounding holes are filled with epoxy grout
to ensure a good bond.
65. Beam Jacketing
• The surface of old concrete is cleaned by air
jetting. Expanded wire mesh is fixed on the two
sides and bottom of the beam. To ensure a good
bond between old concrete and new polymer
modified concrete, an apoxy bond coat is applied
to the old concrete surface. The polymer modified
mortar is applied, while the bond coat is still
fresh. Sometimes 2 to 3 coats of polymer
modified mortar are applied to achieve desired
thickness. The mortar is cured for appropriate
period in water. Epoxy resin grout is injected in
the cracks along top of beams.
67. Questions
• State causes and precautions for distress in structure.
• State new repair system or products.
• Write a SN on properties of repair material and material for
repair.
• Describe the causes of cracks in concrete.
• What is meant by jacketing? Discuss different types of
jacketing?
• Explain in short the procedure for the damage assessment of
structural element.