This document discusses various techniques for concrete repair, including crack repair, grouting, guniting, reinforcement, settlement issues, demolition, and rebar installation. It addresses types of cracks in concrete, how to determine if they are moving or non-moving, and repair methods like grouting. It also covers using guniting to rehabilitate structurally distressed reinforced concrete, applying proper drainage and waterproofing at plinth level, safely demolishing structures, and installing rebar to reinforce concrete and enhance its strength against different load pressures.

2. 1. CRACKS
2. SETTLEMENT
3. DEMOLITION
4. REBARING
TECHNIQUES

3. CRACKS
•Types of Cracks:
Before you attempt to seal the cracks, you must determine the type and
cause of the cracks since this determination may affect the type of
repair that is needed. Cracks can be divided into two categories:-
moving and non-moving.
•Non-Moving Cracks
Most non-moving cracks are a result of shrinkage during the concrete
curing process and can be hairline to over 1 mm (.039 in.) wide. These
cracks are usually shallow and do not penetrate the full depth of the
concrete deck. There are also non-moving cracks that are a result of the
concrete drying shrinkage. They tend to be 1 mm or wider and
penetrate deeper into the concrete deck up to full depth.
Moving Cracks
•Moving cracks are generated by excessive stress in the concrete and
generally are wider than 1 mm. They penetrate the full depth of the
concrete deck. Moving cracks usually have rough (chipped) edges as a
result of freeze-thaw cycles and edge impacts.

4. •Grouting
•
*Grouting is the process of placing a material into
cavities in concrete or masonry structure for the
purpose of increasing the load bearing capacity of a
structure, restoring the monolithic nature of a
structural member, filling voids around pre cast
connections steel base plates, providing fire stops,
stopping leakages, placing adhesives and soil
stabilization.
GROUT is mixture of water, cement and optional
material like sand, water reducing admixtures,
expansion agents and pozzolans. The water to
cement ratio is around 0.5. Fine sand is used to avoid
segregation.

5. GUNI T ING
• Guniting is an effective technique, which has
been extensively used in the rehabilitation of
structurally distressed R.C members. There has
been case of heavy rusting of the mesh in the
form of powder or in the form of a sheet
coming out. Distressing before restoration is
possible only in case of overheads tanks
which can be restored when the tanks are
empty.

6. •Remedial Measures
Reinforcement steel in concrete structures plays a
very important role as concrete alone is not capable
of resisting tensile forces to which it is often
subjected. It is therefore important that a good
physical and chemical bond must exist between
reinforcement steel and concrete surrounding it.
Due to inadequacy of structural design and /or
construction, moisture and chemicals like chlorides
penetrate concrete and attack steel. Steel oxidizes
and rust is formed. This results in loss of bond
between steel and concrete which ultimately
weakens the structure..

7. SETTLEMENT
DPC above ground level:
For DPC above ground level with wall thickness generally not exceeding
40cm, any one of the type of materials mentioned above may be used.
Cement concrete is however commonly adopted material for DPC at
plinth level, 38 to 50mm thick layer of cement concrete M15 (1:2:4 mix)
serves the purpose under normal conditions.
In case of damp and humid atmosphere, richer mix of concrete should
be used. The concrete is further made dense by adding water proofing
materials like Puddle, Impermo, Waterlock etc in its ingredients during
the process of mixing. It is used to apply two coats of hot bitumen over
the third surface of the concrete DPC.

8. Demolition is the tearing-down
of buildings and other structures.
Demolition contrasts
with deconstruction, which involves
taking a building apart while carefully
preserving valuable elements for re-use.

9. REBARING
Rebar, or "reinforcement" bars, are
long steel bars embedded in
concrete to reinforce and enhance
its strength. Different types of
pressures are defined as specific
types of loads, including lateral, horizontal, vertical,
compression, tension and torsion. The method or
technique used to install rebar prior to pouring concrete
determines the way in which it will enhance the
structure's strength.