This topic covers introduction regarding repairs of structures.

1. CHAPTER-1
INTRODUCTION
REPAIRS & REHAIBILITATION OF CONCRETE STRUCTURES
BRIJESH RAYCHANDA
M.TECH STRUCTURAL ENGINEERING
HEAD-CED, VIE(092), GTU

2. INDEX
◈ OVERVIEW
◈ CAUSES OF DISTRESS
◈ DEFICIENCIES & FAILURES
◈ DETERIORATION OF STRUCTURES
◈ NEED FOR REPAIRS
◈ INTRODUCTION TO PROCESS OF REPAIR

3. “Distress means damage.
Concrete may suffer distress
during its life period due to many
reasons.

4. Construction
Architectural Concept
Consultation
with Parties
No
Fire Safety
•Authorities
•Fire Brigades
Yes
Construction
Inspection
Structural Design
Design of
Services
Design of Fire
Safety Systems Fire Safety
•Authorities
•Fire Brigades
No
Yes
Acceptance

5. CAUSES OF DISTRESS
• Structural causes
Externally applied loads
Environmental Loads
Accidents
Subsidences etc
• Error in Design & Detailing
• Poor Construction Practices
• Construction Overloads
• Drying Shrinkage
• Thermal Stress
• Chemical Reactions
• Weathering
• Corrosion

6. Shrinkage Cracks
Chemical Reaction
Weathering
Design

7. CAUSES OF DISTRESS
Other then Hardened state, In plastic stage also concrete
may also suffer damages due to:
• Plastic Shrinkage
• Settlement Cracking
• Early removal of formwork
• Improper design of formwork

8. Corrosion
Shrinkage
Settlement

9. The Cost of Error
Construction
Acceptance
DesignArchitecture£
£1 £2
£ Unlimited

10. CONSTRUCTION DEFICIENCIES
◈ Improper Hooks, Bends, Overlap, Concrete cover
◈ Improper Formwork (Early removal, Not properly supported, Improper
strength of props)
◈ Improper Expansion, Contraction, Construction Joints
◈ Improper Curing of concrete, Brick, Blocks
◈ Segregation while transportation
◈ Settlement of foundation
◈ Concrete surface nor covered (Hot weather condition)
◈ In case of Brick masonry
Bricks are not socked, Frogs are provided at downside, improper Joint.
Excess brick bat quantity, Improper strength

11. CONSTRUCTION DEFICIENCIES
◈ Inferior quality of material.
◈ Waste/Saline water usage.
◈ Adding more water then required (Shrinkage cracks).
◈ Poor grading.
◈ Poor mixing.
◈ Batching by Volume using mortar pans
◈ Insufficient compaction (Honeycombing,Porosity)
◈ Improper location of steel
◈ Dropping concrete from height (Seggregation)
◈ Insufficient Reinforcement

12. DESIGN DEFICIENCIES
(Inadequate Design)
◈ Error in Load Calculation
◈ SBC assumed without testing
◈ Design not as per IS:456 & IS:1893
◈ Load transfer path is not proper understood
◈ Design with many cantilevers & projections
◈ Multistorey framed structure without shear walls.
◈ Soft storey effect not considered while designing
◈ Varying stiffness in both direction resulting torsion
◈ Short column effect not considered
◈ Lake of knowledge of using structural softwares.

13. DESIGN DEFICIENCIES
(Poor Design Detailing)
◈ Abrupt changes in section
◈ Insufficient reinforcement at re-entract corners & openings
◈ Inadequate provision for deflection
◈ Inadequate provision for drainage
◈ Inadequate expansion joint
◈ Material incompatibility
◈ Error in signs showing one-way/two-way slabs
◈ Bent up bar not shown properly
◈ Spacing of lateral ties in beams & columns are shown
improper.

14. DESIGN DEFICIENCIES
(Poor Design Detailing)
◈ Hooks for lateral ties & vertical stirrups are shown 90 degree
instead of 135 degree
◈ Ductile detailing is not followed as per IS 13920

15. DETERIORATION OF CONCRETE
STRUCTURES
Defects
Design
Materials
Construction
Damage
Overload
Fire
Impact
Chemical spill
Deterioration
Erosion
Metal corrosion
Freeze/Thaw
Sulfate Attacks

16. CAUSES DETERIORATION OF CONCRETE
Accidental
Loadings
Chemical
Reactions
◈ Acid Attack
◈ Alkali-Carbonation rock
reaction
◈ Aggressive water
attack
◈ Sulfate attack
◈ Alkali-silica reaction
◈ Miscellaneous chemical
attack
Erosion
◈ Abrasion
◈ CavitationConstruction
Errors
Design Errors
◈ Inadequate
Structural
design
◈ Poor Design
Details
Freezing &
Thawing
Settlement
&
Movements
Temperature
changes
◈ Internally
◈ Externally
Shrinkage
◈ Plastic
◈ Drying
Weathering
Corrosion of
embedded
metals

21. SCENARIO OF DISTRESSED STRUCTURES

25. NEED FOR REPAIR OF STRUCTURES
Workmanship
Procedures
Materials

26. PROCESS OF DURABLE CONCRETE REPAIR
◈ Determine Cause of Damage
◈ Evaluate the extent of damage
◈ Evaluate the need of repair
◈ Select the repair method
◈ Prepare the old concrete for repair
◈ Apply the repair method
◈ Cure the repair properly

27. PROCESS OF DURABLE CONCRETE REPAIR

28. Evaluate
Structure
Determine
causes of
damage &
effect
Repair Analysis
User Needs
Urgency Aesthetics Lifespan
Project Needs
Environment
Contractibility &
Effectiveness

29. Thanks!
Any questions?
You can find me at:
brij.raychanda@hotmail.com