INSITU REHABILITATION-

THE WHEN, THE HOW

By Dr. Yogini DeshpandeDr. Yogini Deshpandeyogini@renukac.cominfo@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

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• 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

Life of the Asset

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Scales in Concrete Structures

Cement Paste

Macroscale

MesoscaleMicroscale

Aggregate

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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Disadvantages of Shotcrete

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�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

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Underpass

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Khayat et, al, 2012

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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

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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

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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

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Preparation of FRCM

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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

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Possible Uses

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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 WWHAT

WHYWHOWHO

WHEREWHEN

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

Thank You

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