Non-destructive Testing Techniques, Epoxy injection, Shoring, Underpinning, Corrosion protection techniques – Corrosion inhibitors, Corrosion resistant steels, Coatings to reinforcement, cathodic protection.

1. DEPARTMENT OF CIVIL ENGINEERING
CE6021-REPAIR AND REHABILITATION OF
STRUCTURE
UNIT IV – TECHNIQUES FOR REPAIR AND
PROTECTION METHODS
PRESENTATION BY
SHANMUGASUNDARAM N
ASSISTANT PROFESSOR
12/4/2020
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2. UNIT IV
TECHNIQUES FOR REPAIR AND PROTECTION METHODS
Non-destructive Testing Techniques, Epoxy injection, Shoring,
Underpinning, Corrosion protection techniques – Corrosion
inhibitors, Corrosion resistant steels, Coatings to reinforcement,
cathodic protection.
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3. CE6021-RRS/unit 4
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4. Shoring
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5. Shoring
Excavation Shoring Live Demo.mp4
Shoring.mp4
Collapse Structure Search and Rescue,
Shoring.mp4
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6. Shoring
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7. Shoring
 It is the means of providing support to get stability of a structure
temporarily under certain circumstances during construction,
repair or alteration.
Such circumstance arises when
 The stability of a structure is endangered due to removal of
a defective portion of the structure.
 The stability of a structure is endangered due to unequal
settlement during construction itself or in long run.
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8. Shoring
 Certain alterations are to be done in present structure itself.
Eg: remodeling of walls, changing position of windows,etc.
 Alterations are carried out in adjacent building for remodeling,
strengthening of foundation, etc.
 For shoring timber or steel tubes may be used. Sometimes both
are used in combination.
 If timber is used its surface should be coated with a
preservative so as to protect against wet rot
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9. Shoring
 The shoring should be designed based on the load it has to sustain
and duration of load.
 Shoring may be given internally or externally depending on the
case and in certain cases they may be provided on either side of
the wall to produce additional stability.
 Shoring should be installed only after getting the permission if
necessary, of the local authorities.
 There is no time limit to which the shoring has to be kept, it may
range from weeks to years depending on the case.
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10. Types Shoring
 Raking or inclined shores
 Flying or horizontal shores
 Dead or vertical shores
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11. RAKING OR INCLINED SHORES
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12. FLYING OR HORIZONTAL SHORING
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13. DEAD OR VERTICAL SHORING
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14. CE6021-RRS/unit 4
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15. UNDERPINNING
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16. UNDERPINNING
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17. UNDERPINNING
Underpinning.mp4
Underpinning.mp4
Underpinning with 60R Screw Anchors.mp4
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18. UNDERPINNING
It is the method of supporting the structures while
providing new foundations or carrying out repairs and
alterations without disturbing the stability of existing
structures.
It is carried under following conditions:
1. When a building with deep foundation is to be
constructed adjoining a building which is built on
shallow footings. Here the shallow footings should be
strengthened first.
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19. UNDERPINNING
3. In order to protect an existing structure from the danger of
excessive or differential settlement of foundation.
4. In order to improve the bearing capacity of foundation so as
to sustain heavier loads for which deepening or widening of
foundation is done.
5. In order to provide a basement for an existing structure.
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20. METHODS OF UNDERPINNING
 Mass concrete underpinning method (pit method)
 Underpinning by cantilever needle beam method.
 Pier and beam underpinning method.
 Mini piled underpinning.
 Pile method of underpinning.
 Pre-test method of underpinning
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21. Mass concrete underpinning method (pit method)
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22. Underpinning by cantilever needle beam method.
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23. Pile method of underpinning.
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24. Chemical method of underpinning.
 In this method the foundation soil is consolidated by
employing chemicals.
 Perforated pipes are driven in an inclined direction beneath the
foundation . The slopes are provided such that the entire area under the
existing footing comes under the area used to be strengthened.
 After the pipes are installed, solution of sodium silicate in water is
injected through the pipes. This is a two-injection method. The pipes
are withdrawn and at the time of withdrawal of pipes, calcium or
magnesium chloride is injected through pipes.
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25. Chemical method of underpinning.
Chemical reaction takes place between these two chemicals and
the soil is strengthened by consolidation. This method is
suitable for granular soils
Other methods
 Other methods are cement
 Grouting, freezing, vibrofloatation, etc.
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26. Carbonation:
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27. Carbonation:
 Carbonation of concrete is a process by which carbon-dioxide
from the air penetrates into concrete and reacts with calcium
hydroxide. To form calcium carbonation.
 Carbonic acid which attack the concrete.
 The carbonation of concrete is one of the main reasons for
corrosion of reinforcement.
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28. Effects of corrosion:
Strength will reduce.
Structures will failure.
Eccentricity.
Cracks, spalling of concrete.
The cross section of reinforcement progressively reduces.
Determination of cover.
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29. Control the corrosion of steel reinforcement
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Control
Metallurgical
ecological
Corrosion
inhibitors
Cement
coating,
Sealing,
Fusion bond,
Epoxy coating
Galvanized
reinforcement,
cathodic
protection.
De-rusting,
Phosphating,
Coating to
concrete
Coating to
reinforcement
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30. To control the corrosion of steel reinforcement:
Metallurgical ecological method.
Corrosion inhibitors.
Coating to reinforcement.
De-rusting, Phosphating, Coating to concrete.
Cement coating, Sealing, Fusion bond, Epoxy coating.
Galvanized reinforcement, cathodic protection.
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31.  Metallurgical method: - உல ோகவியல்
Steel can be made more corrosion resistance by altering its structure
through metallurgical process.
There are many situation were stainless steel reinforcement are used for
long tern durability of concrete structure.
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32. Corrosion inhibitors:
 Corrosion can be prevented by chemical methods by using certain
corrosion inhibiting chemicals such as Nitrates, Phosphate, Benzoates,
etc.,
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33. Corrosion inhibitors:
 A most widely used admixture is based on calcium Nitrates. It is added to
the concrete during mixing of concrete.
 The steel is protected by a layer of ferric oxide on the surface of the steel.
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34. Coating to reinforcement:
 The object of coating to steel bar is to provide a durable barrier to
aggressive material such as chlorides.
 The coating should be robust to with stand fabrication of reinforcement
cage and pouring of concrete and compaction by vibration needle.
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35. De – rusting: Removing Rust in Less Than 3 Minutes.mp4
 The reinforcement is cleaned with a de-rusting solution.
 This is followed without delay by cleaning the rods with wet
waste cloths and cleaning powder.
 The rods are then rinsed in running water and air dried.
Phosphate
 Phosphate is applied to the surface And in inhibitors solution
is then brushed over the phosphate surface.
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36. Cement coating
 Slurry is made by mixing the inhibitor solution with water
and cement and applied on the bar.
 The sealing solution is brushed after the rods are air cured.
 The sealing solution as an inside curing effect.
 The second coat of slurry is then applied and the bars are air
dried.
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37. Sealing: (solution)
 Two coats of sealing solution are applied to the bars in order
to seal the micro pores of the cement coat and to make it
impermeable to corrosive salt.
Epoxy coating:
 Epoxy coating.mp4
 It is one of the effective method of coating the debars.
 Carrying out in a factory and not at site of work
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38. Epoxy coating:
 The plant are designed to coat the straight bars is a
continuous process.
 The epoxy powder particles are deposited evenly on the
surface of the bars.
 The epoxy coated bars have an excellent protection to
corrosion in aggressive environment.
 After treatment, cutting and bending may injure the steel.
 The coating may get damaged during vibration of concrete.
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39. Galvanized reinforcement:
 Galvanized reinforcement consists of dipping of steel bar in
molten zinc.
 The coating of zinc bonded to the surface of steel.
 The zinc surface reacts with the calcium hydroxide in the
concrete to form a passive layer and prevent corrosion.
Hot Dip Galvanizing- Dipping Process....... in action.mp4
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40. Cathodic protection:
 Cathodic protection is one of the effective, well known and
extensively used methods for preventing of corrosion in
concrete method.
 It is high case and long term monitoring required for this
method.
 The catholic protection comprises of application current to an
elected laid on the concrete above steel reinforcement.
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41. Cathodic protection: CATHODIC PROTECTION
PRINCIPLE FOR CONCRETE STRUCTURES.mp4
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42. Cathodic protection:
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THANK YOU
12/4/2020