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Chapter: Civil : Repair and Rehabilitation of Structures : Maintenance and Repairs Strategies

Repair and rehabilitation of Structures

Repair is the technical aspect of rehabilitation. It refers to the modification of a structure, partly or wholly which is damaged in appearance or serviceability.


Repair and rehabilitation

 

Repair is the technical aspect of rehabilitation. It refers to the modification of a structure, partly or wholly which is damaged in appearance or serviceability.

 

The following factors to be considered repair of concrete structures:

The cause of damage

Type, shape and function of the structure

 

The capabilities and facilities available with builders

The availability of repair materials

 

1Stages of concrete repair

Repair of concrete structures is carried out in the following stages:

Removal of damaged concrete

Pre treatment of surfaces and reinforcement

     Application of repair material

     Restoring the integrity of individual sections and strengthening of structure as a whole

2 Repair procedure

A repair procedure may be selected to accomplish on or more of the following objectives:

To increase strength or restore load carrying capacity

To restore or increase stiffens

To improve functional performance

To provide water tightness

To improve durability

To prevent access of corrosive material to reinforcement

 

3 Types and classification of repair Types of repair:

 

Cosmetic treatments on surfaces

Partial replacement of surface and subsurface material

       Additional of reinforcements and bonding materials to strengthen the element

       Total replacement of the structural element

Classification of repair:


Classification of repair : Repair reqirements 

  

Superficial : Cement  mortar bonding by  trowelling    

   

General : Non structural or minor  structural ;restoring cover to  rebars     

   

Principal : Significant loss of concrete  strength; shotcreting for slabs  and beams, jacketing for  columns etc   

  

Major : Demolition and recasting  required.    

 

 

4 Methods of Repairs

The following considerations are to be taken care of and observed:

Determination of extent, location and width of cracks

Classification of cracks as structural and non-structural

 

Dormant cracks:

 

Dormant cracks are caused by some event in the part, which is not expected to recur. They remain constant in width, and may be repaired by filling then with a rigid material.

 

Active cracks:

 

Do not remain constant in width, but open and close as the structure in loaded, or due to thermal and hydras changes in the concrete.

 

Growth cracks:

Increase in width becomes the original reason for their occurrence persists.

 

5 Applications:

The repair of cracks can be achieved with the following techniques:

Resin injection

Routing and Sealing

Stitching

External stressing

Bonding

Blanketing

Overlays

Dry pack

Vacuum impregnation

Polymer impregnation

 

6 Rehabilitations

 

The success of repair activity depends on the identification of the root cause of the deterioration of the concrete structures. The repairs can be done for the improvement of strength and durability, thus extending the life of the structure, is not difficult to achieve.

 

It is the processes of restoring the structure to service level, once it had and now lost, strengthening consists in endowing the structure with a service level, higher than that initially planned by modifying the structure not necessarily damaged area.

 

The following steps are generally used in the rehabilitation of distressed concrete structure:

Support the structural members properly as required.

Remove all cracked, spalled and loose concrete.

Clean the exposed concrete surfaces and steel reinforcement

Provide additional reinforcing bars, if the loss in reinforcement is more than 10%

Apply protective coatings over the exposed/repaired surface.

 

Applications:

Shotcrete/Gunite

Resin injection

Dry pack and Epoxy-bonded dry pack

Slab jacking Technique

Sprayed concrete

 

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Civil : Repair and Rehabilitation of Structures : Maintenance and Repairs Strategies : Repair and rehabilitation of Structures |


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