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:
ü The cause of damage
ü Type, shape and function of the structure
ü The capabilities and facilities available with builders
ü The availability of repair materials
1Stages of concrete repair
Repair of concrete structures is carried out in the following stages:
ü Removal of damaged concrete
ü Pre treatment of surfaces and reinforcement
ü Application of repair material
ü 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:
ü To increase strength or restore load carrying capacity
ü To restore or increase stiffens
ü To improve functional performance
ü To provide water tightness
ü To improve durability
ü To prevent access of corrosive material to reinforcement
3 Types and classification of repair Types of repair:
ü Cosmetic treatments on surfaces
ü Partial replacement of surface and subsurface material
ü Additional of reinforcements and bonding materials to strengthen the element
ü 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:
ü Determination of extent, location and width of cracks
ü Classification of cracks as structural and non-structural
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.
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.
Increase in width becomes the original reason for their occurrence persists.
The repair of cracks can be achieved with the following techniques:
ü Resin injection
ü Routing and Sealing
ü External stressing
ü Dry pack
ü Vacuum impregnation
ü Polymer impregnation
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:
ü Support the structural members properly as required.
ü Remove all cracked, spalled and loose concrete.
ü Clean the exposed concrete surfaces and steel reinforcement
ü Provide additional reinforcing bars, if the loss in reinforcement is more than 10%
ü Apply protective coatings over the exposed/repaired surface.
ü Resin injection
ü Dry pack and Epoxy-bonded dry pack
ü Slab jacking Technique
ü Sprayed concrete