Chapter 4 repair, rehabilitation & retrofiiting

REPAIRS, REHABILITATION
AND
RETROFITTING OF
STRUCTURES
Prepared By:
Assistant Professor Ankit Patel

REPAIR, RESTORATION AND RETROFITTING
Repair: To bring back the position of the structure to its previous
condition so it gives performance same as previously.
It doesn’t cover the strength aspect of the structures.
Some examples of repair…….
Decoration of structure,Painting,White Washing
 Checking the wiring of building
 Replastering of any wall if required
 Repairing of damaged flooring
 Repair of door and window
 Checking or repairing of pipe line connections, gas line connections
and plumbing serveries.
 Relaying disturbed roof tiles
BITS Edu Campusprof. Ankit Patel
2

Rehabilitation: Rehabilitation of a building means returning a
building or a structure to a useful state by means of repair,
modification, or alteration.
It is related to the strength aspect of structures.
To Bring back the position and condition of the structure by
considering the strength aspect.
Some of the examples of Rehabilitation…..
 To fill the wide cracks using some suitable material
 Injecting epoxy like material in to cracks in walls,columns,beams,
etc.
 Removal of damaged portion of masonry and reconstructing it
using rich mortar mix.
 Addition of reinforcing mesh on both sides of the wall
3

Retrofitting:
Earthquake creates great devastation in terms of life, money and
failures of structures.
Earthquake Mitigation is an important field of study from a long time
now.
Seismic Retrofitting is a collection mitigation techniques for
Earthquake Engineering.
It is of utmost importance for historic monuments, areas prone to
severe earthquakes and tall or expensive structures
It is the modification of existing structures to make them more
resistant to seismic activity, ground motion, or soil failure due to
earthquakes.
The retrofit techniques are also applicable for other natural hazards
such as tropical cyclones, tornadoes, and severe winds from
thunderstorms. BITS Edu Campusprof. Ankit Patel
4

When is Seismic Retrofitting Needed ?
The two circumstances are:-
Earthquake damaged buildings, and Earthquake-vulnerable
buildings(with no exposure to severe earthquakes)
Some examples of retrofitting ………
 Increasing the lateral strength in one or both directions, by
reinforcement or by increasing wall areas or the numbers of walls
and columns
 Giving unity to the structure by providing a proper connection
between resisting elements.
 Eliminating features that are sources of weakness, asymmetrical
plan distribution of resisting members, abrupt changes of stiffness
from one floor to the other.
 Avoiding the possibility of brittle modes of failure by proper
reinforcement and connection of resisting members. BITS Edu Campusprof. Ankit Patel
5

REPAIR METHODOLOGY
 Evaluation
 Relating observation to causes
 Selecting methods and materials
 Preparation of drawings and specifications
 Selection of a contractor
 Execution of the work
 Quality Control
6

MATERIALS FOR CRACK REPAIR
The various materials used for repairs of cracks are:
 Cement Slurry
 Cement Mortar
 Epoxy resin
 Polymer Modified Cementitious Products
7

CRACK REPAIR TECHNIQUES
 Epoxy-injection Grouting
 Routing and Sealing
 Flexible Sealing
 Stitching
 Providing additional Reinforcement
 Drilling and plugging
 Prestressing steel
 Grouting
 Dry packing
 Surface Coatings
8

 Epoxy-injection Grouting
Cracks as narrow as 0.002 in. (0.05 mm) can be bonded by the
injection of epoxy. The technique generally consists of establishing
entry and venting ports at close intervals along the cracks, sealing the
crack on exposed surfaces, and injecting the epoxy under pressure.
Epoxy injection has been successfully used in the repair of cracks in
buildings, bridges, dams, and other types of concrete structures.
However, unless the cause of the cracking has been corrected, it will
probably recur near the original crack.
The general procedure are given below.
9

Clean the cracks: The first step is to clean the cracks that have been
contaminated; to the extent this is possible and practical. Contaminants
such as oil, grease, dirt, or fine particles of concrete prevent epoxy
penetration and bonding, and reduce the effectiveness of repairs.
Preferably, contamination should be removed by vacuuming or
flushing with water or other specially effective cleaning solutions.
Seal the surfaces: Surface cracks should be sealed to keep the epoxy
from leaking out before it has gelled. A surface can be sealed by
applying an epoxy, polyester, or other appropriate sealing material to
the surface of the crack and allowing it to harden. If a permanent
glossy appearance along the crack is objectionable and if high
injection pressure is not required, a strippable plastic surface sealer
may be applied along the face of the crack.
10

When the job is completed, the surface sealer can be stripped away to
expose the gloss-free surface. Cementitious seals can also be used
where appearance of the completed work is important. If extremely
high injection pressures are needed, the crack can be cut out to a depth
of 1/2 in. (13 mm) and width of about 3/4 in. (20 mm) in a V-shape,
filled with an epoxy, and struck off flush with the surface.
Install the entry and venting ports. Two methods are in general use:
Fittings inserted into drilled holes: This method was the first to be
used, and is often used in conjunction with V-grooving of the cracks.
The method entails drilling a hole into the crack, approximately 3/4 in.
(20 mm) in diameter and 1/2 to 1 in. (13 to 25 mm) below the apex of
the V grooved section.
11

Bonded flush fitting: When the cracks are not V grooved , a
method frequently used to provide an entry port is to bond a
fitting flush with the concrete face over the crack. The flush
fitting has an opening at the top for the adhesive to enter and a
flange at the bottom that is bonded to the concrete.
12

Mix the epoxy: This is done either by batch or continuous methods. In
batch mixing, the adhesive components are premixed according to the
manufacturers instructions, usually with the use of a mechanical
stirrer, like a paint mixing paddle. Care must be taken to mix only the
amount of adhesive that can be used prior to commencement of gelling
of the material.
Inject the epoxy: Hydraulic pumps, paint pressure pots, or air-
actuated caulking guns may be used. The pressure used for injection
must be selected carefully. Increased pressure often does little to
accelerate the rate of injection. If the crack is vertical or inclined, the
injection process should begin by pumping epoxy into the entry port at
the lowest elevation until the epoxy level reaches the entry port above.
For horizontal cracks, the injection should proceed from one end of
the crack to the other in the same manner. The crack is full if the
pressure can be maintained. If the pressure can not be maintained, the
epoxy is still flowing into unfilled portions or leaking out of the crack.
13

Remove the surface seal: After the injected epoxy has cured,
the surface seal should be removed by grinding or other means
as appropriate.
14

15

16

17

18

19

REPAIR BY ROUTING AND SEALING
20

21

22

23

24

25

26

27

REPAIR BY PROVIDING EXTRA
REINFORCEMENT
28

29

30

31

32

REPAIR BY POST TENSIONING
33

34

GROUTING
Grouting is a process of injecting mixture of cement, sand water at
high pressure in the cracks, joints, voids etc.
Purpose of grouting:
 To strengthen the porous Concrete
 To prevent the seepage in dam and water retaining structures
 To reduce uplift pressure below dam
 To fill the cracks in concrete structure
35

GROUTING
Procedure for grouting:
Drilling of Grouting holes
For drilling grouting holes, equipment's like jack hammer, diamond
drill, shot drill etc are used. The choice of type of drilling equipment
depends upon the type of stone, size of hole and depth of hole.
Arrangement of grout pipes
Grout pipes of 4 to 5 cm dia and 45 to 90 cm length are inserted in the
grout holes. The space surrounding the pipe is filled with cement
mortar. The top end of the pipe is connected to the pump.
Cleaning of cracks
Before injecting grout mixture in the cracks, it is necessary to clean
the cracks.
Inserting grout in holes
Normally grout is inserted in the holes at a pressure 0.65kg/cm2 per m
depth hole BITS Edu Campusprof. Ankit Patel
36

GROUTING
Types of grouting:
1. Consolidation Grouting:
This type of grouting is used for shallow depth grouting holes.
Normally pressure below 3 kg/cm2 is known as low pressure grouting.
2. Stage grouting:
When thick layers are to be grouted the total thickness of layer is
divided into stages of 1m each and grouting of each layer is carried out
one by one. Grouting of upper layer is started only after the grout in
the lower layer had properly set.
3. Curtain Grouting:
This type of grouting is done to prevent the seepage of water below
foundation of dam. Grouting holes are drilled in the upstream side of
dam in the bed rock and impermeable grout wall is created.it will
prevent seepage of water through dam foundation.
37

38

39

40

41

42

43

44

45

46

47

48

49

`
50

CAUSES OF DAMAGE IN MASONRY
BUILDING
 Heavy Weight and very stiff buildings, attracting large seismic
inertia forces.
 Very low tensile strength particularly with poor mortars
 Low shear strength
 Brittle behavior in tension as well as in compression
 Weak connection between wall and wall
 Weak connection between roof and wall
 Stress connection at corners of doors and windows
 Overall unsymmetry in plan and elevation of buildings
51

INTRODUCTION
Many of the techniques available for above water
repair can be used underwater with only minor
modifications. The materials specified for use in
air, however, are often completely unsuitable for
underwater use.
The major effects that underwater working has
on repair operations are summarized as follows:
The cost & difficulty of underwater working
requires that operations to be carried out at
the repair site be minimized & made as simple
as possible. The method of repair must be
tailored to suit the available methods of
access.
BITS Edu Campus prof. Ankit Patel 53

INTRODUCTION
Preparation of the damaged area requires
specially adapted techniques. Care must be
taken to ensure that the area is not
contaminated prior to application of the repair
material.
The material selected for the repair must be
compatible with underwater use both during
placing & curing. Many resin-based repair
materials are not suitable for use underwater;
cementitious systems are however in an ideal
medium.
Placement methods & formwork must be adopted
that minimize mixing between repair material &
water.

INTRODUCTION
Checking during the repair operation and regular
inspection on completion is difficult and costly to
achieve underwater.
The cost of underwater repair is far greater than
for similar repairs carried out in the dry. The cost
of failed repairs is also therefore high. Hence it is
important that laboratory trials on both repair
methods and materials be carried out to identify
possible problem areas and ensure smooth site
operations.

UNDERWATER REPAIR
 Preparation of damaged area: The preparation of damaged area
require removal of cracked concrete and cutting of corroded
reinforcement. The damaged concrete can be removed by high
pressure water jetting. Wherein hydraulic expanding cylinder are
inserted in to pre-drilled holes and pressurized until splitting of
concrete occurs.
57

Chapter 4 repair, rehabilitation & retrofiiting

More Related Content

Chapter 4 repair, rehabilitation & retrofiiting