1. CRACKS

2. SETTLEMENT

3. DEMOLITION

4. REBARINGTECHNIQUES

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 CracksMost 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.

•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.

G U N I T I N G

• 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.

•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..

SETTLEMENTDPC 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.

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.

REBARINGRebar, 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.