This document discusses repair and rehabilitation of concrete structures. It covers causes of distress in concrete structures such as structural issues, design/construction errors, chemical reactions, and corrosion of reinforcement. It then describes evaluation procedures for repair projects, including visual inspection, non-destructive testing, and core extraction/testing. Specific causes of cracks in concrete like plastic shrinkage, thermal stresses, and inadequate reinforcement are also outlined. Finally, routing and sealing of cracks is discussed as a common remedial repair technique.
The document provides guidelines for repair and rehabilitation of existing reinforced concrete buildings. It discusses causes of concrete deterioration like permeability, aggressive agents, and condition surveys. Non-destructive tests are recommended to evaluate concrete quality, cracking, and corrosion. The approach involves identifying deterioration causes, assessing damage extent, and selecting appropriate repair materials and methods to rehabilitate structures in a systematic and cost-effective manner.
ASD Rehabilitation of RCC Buildings Feb 21.pptxDyCEPasighat
The document discusses rehabilitation of reinforced concrete buildings and some common issues. It notes that concrete structures sometimes fail prematurely due to deficiencies in design, materials, construction practices, or harsh environments. Periodic inspections are often lacking. Common defects include cracking, corrosion of reinforcement, and deterioration from carbonation or chlorides. Proper repair requires understanding the root causes of damage and using compatible materials and good workmanship. The longevity of repairs depends on adequately addressing the original deterioration mechanisms.
This document discusses quality assurance for concrete construction. It outlines three key components of a quality management system: 1) a quality assurance plan, 2) quality control process, and 3) quality audits. The quality assurance plan establishes organizational responsibilities, control measures, acceptance criteria, and documentation requirements. Quality control ensures conformance to specifications. Quality audits verify that quality assurance and control programs are properly implemented. Factors that affect concrete properties like strength, permeability, cracking and durability are also summarized.
This document discusses quality control and durability factors in concrete. It defines quality as conformance to requirements and durability as a concrete's ability to resist deterioration when exposed to the environment. Several factors influence concrete durability, including the materials used, water-cement ratio, compaction, curing and the physical and chemical conditions of the service environment. Common durability issues include corrosion, cracking from sulfate attack or alkali-silica reaction, and carbonation reducing alkalinity. Proper quality control of materials and construction processes is needed to produce durable concrete.
Condition survey and non destructive evalution of concreteAvinash Kumar Gupta
The document provides information on conducting condition surveys and non-destructive evaluation of concrete structures. It discusses examining concrete to identify distress, collecting a structure's history, and assessing causes of issues like corrosion or cracking. Non-destructive tests mentioned include rebound hammer, ultrasonic pulse velocity, pullout tests, and cover meter readings to evaluate concrete strength, cracking, and rebar location without damaging the structure. The document provides detailed procedures for performing these assessments and tests.
A Case Study of Existing Institutional Building for Assessment and Repair (VJ...Mayur Rahangdale
1) A case study was conducted on an existing 10-year-old institutional building to assess its condition and identify repair needs.
2) Visual inspections, non-destructive testing, and chemical analyses were performed, identifying issues like cracks, dampness, and corrosion.
3) Recommended repairs included replacing damaged floor tiles, treating cracks and dampness, termite treatment, repairing expansion joints, and structural reinforcement.
Inspection,Repair and Strengthening of PSC Bridge.Mohammad Furqan
The document provides information on inspection, repair, and strengthening of pre-stressed concrete (PSC) bridges. It discusses common types of deterioration in concrete bridges such as carbonation, chloride attack, alkali-silica reaction, and corrosion of steel reinforcement. It outlines the inspection process including planning, objectives, equipment used, and what elements to inspect such as cracks, bearings, and prestressing components. Non-destructive testing methods like rebound hammer, ultrasonic pulse velocity, and cover meter tests are described. Finally, common repair methods for concrete like mortar filling, grouting, shotcrete, and fiber reinforced polymer wrapping are presented.
The document provides guidelines for repair and rehabilitation of existing reinforced concrete buildings. It discusses causes of concrete deterioration like permeability, aggressive agents, and condition surveys. Non-destructive tests are recommended to evaluate concrete quality, cracking, and corrosion. The approach involves identifying deterioration causes, assessing damage extent, and selecting appropriate repair materials and methods to rehabilitate structures in a systematic and cost-effective manner.
ASD Rehabilitation of RCC Buildings Feb 21.pptxDyCEPasighat
The document discusses rehabilitation of reinforced concrete buildings and some common issues. It notes that concrete structures sometimes fail prematurely due to deficiencies in design, materials, construction practices, or harsh environments. Periodic inspections are often lacking. Common defects include cracking, corrosion of reinforcement, and deterioration from carbonation or chlorides. Proper repair requires understanding the root causes of damage and using compatible materials and good workmanship. The longevity of repairs depends on adequately addressing the original deterioration mechanisms.
This document discusses quality assurance for concrete construction. It outlines three key components of a quality management system: 1) a quality assurance plan, 2) quality control process, and 3) quality audits. The quality assurance plan establishes organizational responsibilities, control measures, acceptance criteria, and documentation requirements. Quality control ensures conformance to specifications. Quality audits verify that quality assurance and control programs are properly implemented. Factors that affect concrete properties like strength, permeability, cracking and durability are also summarized.
This document discusses quality control and durability factors in concrete. It defines quality as conformance to requirements and durability as a concrete's ability to resist deterioration when exposed to the environment. Several factors influence concrete durability, including the materials used, water-cement ratio, compaction, curing and the physical and chemical conditions of the service environment. Common durability issues include corrosion, cracking from sulfate attack or alkali-silica reaction, and carbonation reducing alkalinity. Proper quality control of materials and construction processes is needed to produce durable concrete.
Condition survey and non destructive evalution of concreteAvinash Kumar Gupta
The document provides information on conducting condition surveys and non-destructive evaluation of concrete structures. It discusses examining concrete to identify distress, collecting a structure's history, and assessing causes of issues like corrosion or cracking. Non-destructive tests mentioned include rebound hammer, ultrasonic pulse velocity, pullout tests, and cover meter readings to evaluate concrete strength, cracking, and rebar location without damaging the structure. The document provides detailed procedures for performing these assessments and tests.
A Case Study of Existing Institutional Building for Assessment and Repair (VJ...Mayur Rahangdale
1) A case study was conducted on an existing 10-year-old institutional building to assess its condition and identify repair needs.
2) Visual inspections, non-destructive testing, and chemical analyses were performed, identifying issues like cracks, dampness, and corrosion.
3) Recommended repairs included replacing damaged floor tiles, treating cracks and dampness, termite treatment, repairing expansion joints, and structural reinforcement.
Inspection,Repair and Strengthening of PSC Bridge.Mohammad Furqan
The document provides information on inspection, repair, and strengthening of pre-stressed concrete (PSC) bridges. It discusses common types of deterioration in concrete bridges such as carbonation, chloride attack, alkali-silica reaction, and corrosion of steel reinforcement. It outlines the inspection process including planning, objectives, equipment used, and what elements to inspect such as cracks, bearings, and prestressing components. Non-destructive testing methods like rebound hammer, ultrasonic pulse velocity, and cover meter tests are described. Finally, common repair methods for concrete like mortar filling, grouting, shotcrete, and fiber reinforced polymer wrapping are presented.
Construction materials testing (CMT) involves testing materials used in construction projects to ensure quality. The specific tests conducted depend on the materials and project scope, but often include tests of aggregates, cement, concrete, steel reinforcement, and other common construction materials. Standard test methods have been established by organizations like ASTM and ISO. Test results help ensure construction materials meet design specifications and standards.
The document discusses various non-destructive testing methods used to evaluate the condition of concrete structures, including rebound hammer testing, ultrasonic pulse velocity testing, carbonation testing, chloride testing, core cutting, half-cell potential testing, pull-out testing, and concrete endoscopy. It describes the objectives and procedures of each method and how they are used to identify distress, assess damage, and evaluate strength.
Assessment and rehabilitation technique of fire damaged structuresMohammed Faazil
This document discusses the assessment and rehabilitation of concrete structures affected by fire. It begins by introducing how concrete behaves when exposed to high temperatures during a fire. It then covers: assessing the damage to non-structural elements, utilities, and structural members through visual inspection and field/laboratory testing; common rehabilitation techniques like fiber reinforced polymer jacketing, concrete jacketing, and steel jacketing; and concludes that a systematic assessment is needed to determine appropriate repairs.
Distress of concrete structures & their repair techniquesZaid Ansari
This document discusses concrete distress and repair techniques. It begins by explaining that concrete structures may need repair after 25-30 years of service without maintenance. It then lists common causes of concrete distress like weathering, environmental effects, poor design/construction, and water leakage leading to corrosion. The document outlines expected service lives for different structure types. It also describes common concrete failure modes and causes of early deterioration. The remainder of the document discusses techniques for identifying distressed concrete, various repair materials and methods, and the need for trained concrete workers.
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Attained by one of three means:
High cement content
High content of Fly Ash, Silica Fume etc
Use of Viscosity Modifying Admixture
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This document provides an introduction to reinforced concrete, including its key components and purposes. Reinforced concrete is a composite material made of concrete, which resists compression well but has low tensile strength, and steel reinforcing bars, which resist tension well. Together they create an economical and strong structural material. The document outlines structural elements, design considerations for safety, reliability, and economy, and limit state design principles which ensure structures do not fail under expected loads. It also discusses factors that affect concrete durability and different failure modes in reinforced concrete depending on steel reinforcement ratios.
This document discusses half-cell potential measurement testing (HCPM) for assessing concrete structures. It describes the objectives and principles of HCPM, including using potential difference measurements between a copper-copper sulfate reference electrode and the reinforcing steel. HCPM is a nondestructive test that can identify locations of reinforcing corrosion and delamination. It also compares HCPM to other tests like rebound hammer and ultrasonic methods, and discusses tips for preventing corrosion like using protective coatings or inhibitors.
Condition Assessment and Evaluation of Concrete Structures by Advanced Non-de...IRJET Journal
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REPAIR AND REHABILITATION OF STRUCTURES.pptxKavinKumars19
Maintenance, repair and rehabilitation of structures aims to extend the life of structures and improve safety and performance. Proper maintenance includes regular inspections to detect issues early and prevent major deterioration. Inspections may be daily, weekly, monthly or yearly depending on the structure. Assessments of damaged structures involve inspection, testing, load analysis, and choosing remedial actions like repairing cracks, strengthening, or full replacement. Deterioration can result from poor design, environmental effects, low quality materials, or lack of supervision during construction. Common causes of deterioration include corrosion, freezing and thawing, chemical reactions, and physical weathering.
This document discusses quality assurance for concrete structures. It defines quality assurance as ensuring all components of a structure perform as intended over the structure's lifetime. It identifies key parties that benefit from quality assurance, including clients, designers, material producers, contractors, and users. The document then describes the three main components of a quality management system: quality assurance plans, quality control processes, and quality audits. It provides details on what should be addressed in quality assurance plans and quality control processes. Finally, it discusses how quality audits are used to monitor and document quality assurance and control programs throughout the design and construction phases.
Dr. S. RAVIRAJ introduces various non-destructive testing (NDT) methods for evaluating concrete structures, including rebound hammer testing, ultrasonic pulse velocity testing, rebar location testing, and corrosion analysis testing. He describes the testing principles, equipment used, factors influencing results, and applications and limitations of these common NDT methods. NDT methods can detect issues like cracks, voids, reinforcement location and cover concrete thickness without harming the structure.
The document discusses the repair and rehabilitation of deteriorated concrete structures. It provides information on:
1) The main causes of concrete deterioration including corrosion of steel reinforcement from chlorides or carbonation, poor quality concrete, and environmental factors.
2) The stages of condition survey to evaluate deterioration including preliminary inspection, planning, visual inspection, and field/laboratory testing on representative structural elements.
3) Common defects observed in concrete like cracks, staining, and evidence of chemical reactions or corrosion of reinforcement.
Epsilon Engineering is a civil engineering consulting firm that provides services including surveying, grading and drainage design, structural design, geotechnical analysis, construction material testing, and environmental assessments. It aims to be a full-service engineering provider through open communication and creative solutions. The firm's laboratories are certified to conduct various material tests for projects, including soil, concrete, asphalt, and aggregate testing to applicable ASTM standards.
This document discusses techniques for repairing, rehabilitating, and retrofitting structures. It covers strengthening structural elements, repairing structures damaged by corrosion, fire, leakage, or earthquakes. Specific techniques addressed include repairing fire-damaged concrete, sealing leaks, repairing cracks, jacketing structural members, and dry packing. The document also covers engineered demolition methods like mechanical demolition, implosion, and deconstruction for taking down structures.
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
The document discusses various topics related to concrete structures including:
- Concrete is the second most used construction material after water due to its durability and ability to be molded into different shapes. Reinforcement is added to concrete to improve tensile strength.
- Types of cement used in concrete structures including Type K and Type M cement.
- Reinforced concrete uses steel reinforcement bars to improve tensile strength. Prestressed concrete applies stress before external loads to increase load capacity.
- Advantages of concrete structures include availability/cost of materials and ability to take compressive/bending forces. Disadvantages include cracking from shrinkage and weakness in tension.
- Concrete creep is a permanent deformation over time under load. Cre
This document provides 26 questions and answers on repairs and rehabilitation of structures. It discusses key topics like the definitions of maintenance, repair, and rehabilitation. It also addresses causes of deterioration like corrosion, environmental effects, and poor quality materials. Methods for evaluating existing structure strengths are outlined, like the fixed percentage method and load testing. Important considerations for repair work are highlighted, such as selecting procedures, addressing design and construction flaws, and the importance of supervision quality. Stages of inspection and maintenance are also summarized.
Experimental Study on Bond Performance of Reinforced Bars in Concreteijtsrd
This paper studied the effects of reinforcement corrosion on bond performance between G-35 concrete and 16mm reinforcing steel for different corrosion levels. The steel rebar embedded in concrete specimens were corroded using an electrochemical accelerated corrosion technique by impressing current to the specimens to develop the different mass losses of reinforcement bars after corrosion. Then, monolithic pull-out loading tests were carried out on the specimens to develop the bond strength which is an important property in concrete construction as it determines the amount of tensile stress a concrete member is able to withstand safely. Bond-slip relationships for the different corrosion levels were compared. The achieved mass losses of rebar were compared with theoretical mass losses obtained by Faraday's law. Thiri Nyein Pyae Aung "Experimental Study on Bond Performance of Reinforced Bars in Concrete" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-1 , December 2018, URL: http://www.ijtsrd.com/papers/ijtsrd19049.pdf
retrofitting of fire damaged rcc slabs,colums,beamsNayana 54321
This document discusses techniques for retrofitting existing reinforced concrete structures. It introduces various problems that can occur in concrete structures like damage, excessive loading, cracks, and corrosion. Retrofitting aims to restore strength and improve serviceability. Factors influencing the selection of a retrofitting technique include cost, time constraints, and existing structure conditions. Conventional techniques discussed are section enlargement, external plate bonding, external post-tensioning, ferrocement covering, and grouting. An advanced technique of fiber reinforced polymer composites is also introduced, with carbon fiber reinforced polymer being highlighted. CFRP has advantages of high strength, corrosion resistance, and suitability for seismic retrofitting but also has high initial costs.
Generative AI Use cases applications solutions and implementation.pdfmahaffeycheryld
Generative AI solutions encompass a range of capabilities from content creation to complex problem-solving across industries. Implementing generative AI involves identifying specific business needs, developing tailored AI models using techniques like GANs and VAEs, and integrating these models into existing workflows. Data quality and continuous model refinement are crucial for effective implementation. Businesses must also consider ethical implications and ensure transparency in AI decision-making. Generative AI's implementation aims to enhance efficiency, creativity, and innovation by leveraging autonomous generation and sophisticated learning algorithms to meet diverse business challenges.
https://www.leewayhertz.com/generative-ai-use-cases-and-applications/
Blood finder application project report (1).pdfKamal Acharya
Blood Finder is an emergency time app where a user can search for the blood banks as
well as the registered blood donors around Mumbai. This application also provide an
opportunity for the user of this application to become a registered donor for this user have
to enroll for the donor request from the application itself. If the admin wish to make user
a registered donor, with some of the formalities with the organization it can be done.
Specialization of this application is that the user will not have to register on sign-in for
searching the blood banks and blood donors it can be just done by installing the
application to the mobile.
The purpose of making this application is to save the user’s time for searching blood of
needed blood group during the time of the emergency.
This is an android application developed in Java and XML with the connectivity of
SQLite database. This application will provide most of basic functionality required for an
emergency time application. All the details of Blood banks and Blood donors are stored
in the database i.e. SQLite.
This application allowed the user to get all the information regarding blood banks and
blood donors such as Name, Number, Address, Blood Group, rather than searching it on
the different websites and wasting the precious time. This application is effective and
user friendly.
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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.