diagnostic approach towards structural repairs
TRANSCRIPT
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Diagnost ics approach
towards
St ructu ral repairs
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Typical issues in RCC structures
- Corrosion
- Cracking- Spalling of concre te
- Leakage / seepage
- Bulging of concre te
- Deflection of structural m em bers, etc.,
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CRACKS indicate the beginning ofdeterioration in most cases
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LEAKAGE
Can be very ugly and dangerous
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SPALLING
Result of neglected leakage & cracks for long time
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Factors that lead to Problems
Built in problems (I nternal)
External Causes
Man made causes
Natural calamities
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I nternal Cause
Design issues
Improper selection of materials
Wrong waterproofing specifications
Faulty construction methods
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External Cause
Environmental attack
Chlorides
Carbon dioxide
Sulphates
Humidity
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Man made causes Change in use of structures
Over loading
Unplanned modifications /alterations
Poor maintenance
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Natural calamities
Earthquake
Flood
Fire
Cyclones
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Typical Causes:Corr osion of reba r
- Chemically active soil
- Pollution
- I ndustrial abuse(chemicals)
- High relative hum idity
- Environmental attack
Chlor ide & Co2
induced
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Cracks due tocorrosion
A major problem
Protection reduced
Concrete becomes porous
Entry of CO2 &
Chlorides & moisture
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Co2 induced corrosion
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Chloride induced corrosion
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Approach to syste m at ic repairs
I nspection most important activity
must be done by a professional
- Every structure requires different approach.
E.g. building structure, industrial str, jetty,
cooling towers, intake pump houses, dams,
bridges, etc.,
- All locations of distress should be noted
- Original drawings, if available, should bereferred
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Approach to syste m at ic repairs
Cause and nee d ident ificat ion:
-W hat is m ain cause?
-W hy repairs?
-W hat is the l ife expectancy?
-W hat is the importance of structure?
-I s the need only to patch repairs? Or any
other
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Unless the cause is ident ified and
rem oved, repa irs can not be
effective & com plete.
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NEED??
- Life ext ension
- Strengthening
- I ncrease in loads
- Seismic
- Restorat ion t o
original design
values
- Protection
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Diagnosis:
( Visual inspection + Diagnosis)
Comparison
Structural engineer = Doctor
Pat hological tests = NDT
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Diagnosis:ND Ts are e ffective tools to
determ ine the hea lth of concrete
TO ASSESS PERFORMANCETO ASSESS PERFORMANCE
LEVEL DURING SERVICELEVEL DURING SERVICE
LIFELIFE
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PARAMETERS TO BE EVALUATEDPARAMETERS TO BE EVALUATED
a) STRENGTH ( I N -SI TU)b) DURABI LI TY PERFORMANCE
presence of internal voids/ cracks,materials likely to cause disruption ofconcrete (sulphate or alkali reactiveaggregates), extent or risk of reinf.corrosion, chloride content, cover
thickness, permeability etc.
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NDT:Com m on NDTs are
1 . Rebound ham m er test
2 . USPV
3 . Half cell potent ial met er
4 . Rebar locator
5 . Core te st
6 . Thickness test
7 . Carbonation test
8 . Chem ical a nalysis