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INSITU REHABILITATION-
THE WHEN, THE HOW
By Dr. Yogini DeshpandeDr. Yogini [email protected]@renukac.com
For - NAREDCO- BMTPC Conference on Emerging Technologies in Housing and Building Construction
www.renukac.com
• FOR MAJOR BUILDINGS, BRIDGES, SHORE PROTECTION WORKS AND OFF-SHORE STRUCTURES
• DESIGN OF EARTH RETENTION SYSTEMS AND GROUND IMPROVEMENT STUDIES
GEOTECHNICAL GEOPHYSICAL
INVESTIGATIONS & DESIGNS
• SYSTEMATIC CONDITION ASSESMENT OF STRUCTURES BY NDT AND OTHER TECHNIQUES
STRUCTURAL ASSESSMENTS &
STRUCTURES BY NDT AND OTHER TECHNIQUES
• FIRE DAMAGE ASSESSMENTS, DISTRESS DUE TO AGING
ASSESSMENTS & DESIGN
• BESPOKE SCHEME FOR REPAIRING AND STRENGTHENING OF STRUCTURES,
• SIESIMIC UPGRADATION, CAPACITY ADDITION AND
• REPAIR OF HERITAGE STRUCTURES
ASSET MANAGEMENT REPAIR &
RETROFITTING FOR STRUCTURES
Outline
• Economics of Asset Management • Methodology of Repair and Rehabilitation • Economics of Repair Methodologies • Economics of Repair and Reconstruction
RENUKA CONSULTANTS
• FOR RESIDENTIAL BUILDINGS, SCHOOL BUILDINGS AND COMMERCIAL PREMISES, CAST-IN-SITU and PRECAST SYSTEMS
• BRIDGES,
STRUCTURAL DESIGNS
• SYSTEMATIC CONDITION ASSESMENT OF EXISTING STRUCTURES BY NDT AND OTHER TECHNIQUES
• FIRE DAMAGE ASSESSMENTS, DISTRESS DUE TO AGING
ASSET MANAGEMENT &
STRUCTURAL ASSESSMENTS
• BESPOKE SCHEME FOR REPAIRING AND STRENGTHENING OF STRUCTURES, SIESIMIC UPGRADATION, CAPACITY ADDITION AND REPAIR OF HERITAGE STRUCTURES
REPAIR & RETROFITTING FOR BUILDINGS
• PROJECT MANAGEMENT WITH SUPERVISION
• QUALITY CONTROL INSPECTION
• THIRD PARTY AUDITORS
PROJECT MANAGEMENT &
QUALITY CONTROL INSPECTION
Scales in Concrete Structures
Cement Paste
Macroscale
MesoscaleMicroscale
Aggregate
RENUKA CONSULTANTS
Types of damages
Material Distress /
Damage
Structural Damage
• Over loading
• Impact / High load hits
• Cracking / Fatigue
• Impact / High load hits
• Fire
• Blast
• Earthquake
• Deficiencies in original
design
• Settlement of foundations
• Moisture movement
• Scaling / Spalling
• Corrosion
RENUKA CONSULTANTS
Worst Sin in Engineering
“The worst sin in an engineering material is not lack of strength or lack of stiffness, desirable as these properties are, but lack of toughness, that is to say, lack of resistance to the propagation of cracks.” – J.E.Gordon
RENUKA CONSULTANTS
Picture from Tate’s Museum, London
Importance of Crack Width
No Leakage Leakage Corrosion
Crack Healing
Controllable Leakage
Visible Leakage
0 0.050 0.127 0.330~0.406 0.838
Crack Width
Beginning of visible cracking
mm
RENUKA CONSULTANTS
Crack Repair
MOVING NON-MOVING
� Subject to thermal changes - roof deck, bridges
• Constant Temperature - basement walls
� Subject to transient • One time loading � Subject to transient loading - all floor slabs
• One time loading - basement walls with NO hydrostatic pressure
• Subject to building movement - wind, earthquake, settlement
• Repaired for movement - repaired settlement
RENUKA CONSULTANTS
The Fixes Depend Upon
• Structural Stress vs Shrinkage – Key to know how to repair
• Moving vs Non-moving – Key to know what material to use for repairs– Slab cracks are always moving regardless of the source– Slab cracks are always moving regardless of the source
• Full Depth vs Partial Depth– Key to understanding the potential for damage – Restraint cracks are always full depth
• Wide vs Narrow – Key to know for material selection
RENUKA CONSULTANTS
Repair/Health Monitoring are
similar
Examination Evaluation Prescription Prediction
Non Destructive Testing (NDT), light tapping
High porosity, low strength, low air content
Repair, strengthening, sealing
RENUKA CONSULTANTS
Structural Condition Assessment
• Visual survey of current state of structure• Review of documents and check conformity • Preliminary analysis of structure • Determine the current state of health of the • Determine the current state of health of the
structure – Observe damage– Establish a diagnosis – Arrive at a prognosis
RENUKA CONSULTANTS
Evaluation of Concrete Deterioration /
Damage• Visual Examination –
powerful form of non-destructive testing– Crack size – Crack pattern
• Non-destructive testing
• Coring / destructive • Coring / destructive testing
• Laboratory / microscopicalobservations
• Long-term observation
Repair Methods, Techniques and Materials
• Repair Methods– Necessary to repair symptoms rather than only cause– Extent of damage, accessibility to damaged area,
time, finance and future intended use dictate the type of method adopted.
• Repair Technique– Shotcrete, FRP, CFRP, FRCM– Shotcrete, FRP, CFRP, FRCM
• Repair Materials – Cementitious based materials – Polymer modified concrete – Epoxy based materials and coatings – Sealers and sealants
RENUKA CONSULTANTS
Repair Strategy
Strategy 1:
� Enhanced repair material of a significantly higher quality than existing
Repair system has no redundant features relies on quality of material & construction
Strategy 2:
� Durable repair material of a similar / higher / superior quality than existing
� Protective surface sealer, membrane, coating on surface
Repair Strategy
Strategy 3:
� Enhanced repair material of a significantly higher quality than existing
� Protective surface sealer, membrane, coating on surfacesurface
� Reinforcement protective system
Repair of BDD Chawls Worli, Mumbai
• Owned & occupied by different State and local Govtorganisations
• Built in early 1910s • Built in early 1910s • Currently houses
Class III, IV and V employees
• Some internal repair in mid1990s
RENUKA CONSULTANTS
Repair Technique adopted for BDD
Chawls• Micro concreting for columns and beams
– Bagged product as per PWD schedule
• Remove all old repair concrete and corroded steel
• Visual inspection of underneath slab will determine further actiondetermine further action– Either cast new slab OR– Add new steel with non-corrosive coating– Old steel applied with zinc rich coating – Shotcrete on slab
RENUKA CONSULTANTS
Disadvantages of Shotcrete
RENUKA CONSULTANTS
�Problem to properly encapsulate closely spaced
large diameter rebar
�Fresh shotcrete can fall-off if mixture design is not
proper
Disadvantage of Shotcrete
• Rebound increases quantities
• Requires more cleanup• Rougher surface than
conventional concrete• Requires skilled personnel• Requires skilled personnel• Proper curing of surfaces
is difficult • Difficult to measure actual
depth of shotcrete over complete area
SOLUTION -?RENUKA CONSULTANTS
Self Compacting Concrete- Definition
Fresh concrete that can flow around reinforcement and
consolidate within formwork under its own weight
without vibration and that exhibits no defect due to
segregation or bleeding. - ACI 237
Advantages of SCC
• Easy to cure• Ease of placement in
limited access areas• Excellent durability• Smooth surfaces• Smooth surfaces• Eliminate
honeycombing• Eliminate surface
repairs
RENUKA CONSULTANTS
Restoration and Retrofitting of Old
Factory Premises
• Built in 1950s• Client wants exterior
façade to be retained • Masonry wall
strengthening with steel and Self Compacting Concrete with small size aggregate
RENUKA CONSULTANTS
Fabric or Fiber Reinforced Cementitious
Matrix
• Two Key Components-
– cementitious matrix
– fiber network or grid
• FRCM composite consists of one or more layers of cement-based matrix reinforced by fibre fabric
• ACCEPTANCE CRITERIA FOR MASONRY AND CONCRETE • ACCEPTANCE CRITERIA FOR MASONRY AND CONCRETE
STRENGTHENING USING FIBER-REINFORCED CEMENTITIOUS
MATRIX (FRCM) COMPOSITE SYSTEMS - AC 434 developed by
International Code Council – FRCM material properties.– Axial, flexural and shear capacities of FRCM system.– Performance of FRCM system under environmental exposures.– Performance under exposure to fire conditions.– Structural design procedures
RENUKA CONSULTANTS
Disadvantages of Fiber Reinforced
Polymer • Lower ductility• Inconsistent plastic behaviour and ultimate behaviour• Difficult application on uneven surface• More expensive• The polymeric matrix is prone to the ultra violet
degradation• Impossible to apply on wet surface• Impossible to apply on wet surface• Impossible to apply at low temperature• Low glass transition temperature of matrix• Poor fire/high temperature resistance• May release toxic gas in high temperature from the
matrix
RENUKA CONSULTANTS
Advantages of FRCM
• It possesses most of the advantages of FRP.• The thermal/fire resistance of the
cementitious matrix is superior compared with epoxy resin.
• The cementitious matrix allows vapourpermeability.
• It can be applied on wet surfaces
RENUKA CONSULTANTS
Possible Uses
RENUKA CONSULTANTS
Base coat 5-10mm thick followed by Glass Fiber Sheet and top coat of 10mm on the fiber sheet.
Passive Design/Strengthening
Concrete slab strengthened with FMRC or steel plate
No stress exists in steel plates until live loads are introduced, as slab deflects, the steel plate will begin to share the tension loads
Selection Criteria
• 5 W
• + COST • + Owner’s and engineer’s preference and
comfort with repair solution
= SELECTION OF REPAIR METHOD AND = SELECTION OF REPAIR METHOD AND MATERIAL