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Early-Age Properties of Repair Binders
(Lab, Field and Test Methods)
Tuesday, April 16, 4:00 PM - 6:00 PM, C-101 D
Early-Age Repair Material Properties
&Early Age Repairs
Fred GoodwinFellow Scientist
BASF Construction Systems
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Early-Age Repair Material Properties
Early Age Material PropertiesRepairs Performed at Early Ages
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┼ Concrete is economical with a long life & low maintenance ┼ Concrete does not rot, corrode, or decay. ┼ Concrete can be molded or cast into almost any desired shape. ┼ Concrete is fire-safe & able withstand high temperatures. ┼ Concrete is resistant to wind, water, rodents, and insects. ┼ 12 BILLION cu meters per year globally┼ ~1 cu yd / person / year in USA┼>70 Billion cu meters placed in USA since 1930
with ~10 Billion cu meters > 20 years old
What is Concrete?
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Improved Construction Technology
Wood Age →Stone Age→
Masonry Age →
Steel Age →
Concrete Age
Tallest
Largest
Longest
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• The cost to owners for concrete repair, protection, and strengthening in US is $18 to $21B /yr (2004)
htty://www.concrete.org/members/CRB04_Emmons-Sordyl.pdf
• The cost of corrosion of concrete reinforcement is > $125B / yrhttp://www.corrosioncost.com/infrastructure/highway/index.htm
• A 7 year infrastructure investment of $3.6 trillion is needed to return to quality of 1988 infrastructure C�D+
http://www.infrastructurereportcard.org/
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Why does concrete fail?
• Concrete requires repair and strengthening due to
the 3 D’s
– Design and Construction Errors
– Deterioration
– Damage
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Why does concrete fail?
• Concrete has (compared to other building materials)
• -low tensile strength (~10% of compressive strength),
• -low ductility (it’s brittle),
• -low strength-to-weight ratio (it’s heavy),
• -responds to environment (it changes with time)
• -has permeability(ingress of deleterious materials)
• -is susceptible to chemical attack(acids, AAR, etc.)
• -and it cracks.
• Steel corrodes• Chloride, carbonation, and polarization interaction
• Rust expands, causing cracking, spalling, and eventual failure
ALL of these properties change as the concrete ages.
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How does concrete fail?
Cracks
Steel
Concrete
Frost damage, concrete not air entrained
Air entrained concrete
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What to Do?
New Construction
• Usually you inherit the problem, but….• Design!!!
• Place reinforcement with proper cover depth (>1½”)
• Use low W/CM
• Use appropriate admixtures (Air, AAR, SO3, etc.)
• Proper consistency and well consolidated
• Properly cure the concrete
• i.e., good trade practice
–Details, Details, Details, Details……
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Service Life
Maximum Permissible Corrosion
Corrosion Initiation Phase
(i.e., ingress of chloride, carbonation, etc.)
Corrosion Propagation Phase
(i.e., progressive corrosion & degradation of Reinforcement)
Proactive
InterventionPreventative
Intervention
Tuutti Diagram
CO
ST $
Do Unto Your Future Before It Does Unto YOU!
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De Sitter’s Law of Fives$1 spent on Monitoring =
$5 spent on Preventative Maintenance Before Corrosion Initiation =
$25 spent on Repair and Maintenance after Corrosion Initiation =
$125 spent on Repair & Replacement after Generalized Corrosion
Propagation
Pay Me NOW
OR
Pay Me LATER
De Sitters Law of Fives
$0 $20 $40 $60 $80 $100 $120 $140
Monitoring
Preventatvie Maintenance
Repair of Localized Corrosion
Major Repairs Generalized Corrosion
Dela
y o
f Repair
Cost ($)
What is the biggest ROI for concrete repair?
http://irc.nrc-cnrc.gc.ca/pubs/fulltext/nrcc44300.pdf
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Concrete Repair Process
Evaluation, Analysis, & Strategy
Effect RepairAnalysis
Repairrequired?
YESCondition
SurveyRepair
Strategy
Repair
NO
Cause
Maintenance
Maintenance
Demolition
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ConcreteRepair ProcessRepair
required?RepairStrategy
RepairAnalysis
Owner Criteria
� Urgency� Cost� Expectations� Service life� Aesthetics
EngineeringCriteria
� Structural req.� Effect� Constructability� Environment� Safety
Safety
Structural catastrophe
Use dysfunction
Leakage
Effects on environment
Aesthetics
Preventive maintenance
Cause &Effect
� Leakage� Settlement� Deflection� Wear� Spall� Disintegration� Crack
Defect,damage ordeterioration
ConditionSurvey
YES
Evaluate
Quantify
Document
RepairStrategy
Preparation
Materials
Methods
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MethodsRepair materials Placement techniques
Surface Repair� Overlay� Trowel-applied� Shotcrete� Full member� Form & pump
Stabilization� Slab jacking� PT repair� Connections� Crack injection� Soil stabilization
Strengthening� Enlargement� Post-tensioning� Carbon fiber� Span shortening� Shear transfer
Waterproofing� Grouting� Waterstop� Crack treatment� Exp. joints� Sealants
Protection� Sealers� Coatings� Membranes� Galvanic Prot.� Jacketing
Repair Strategy
EffectRepair
required?ConditionSurvey
RepairAnalysis
RepairStrategy
YESCause
Concrete Repair Process
Placement techniques
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Repair Materials– Ordinary Concrete– Preplaced Aggregate Concrete– Fiber Reinforced Concrete – Ferrocement– Low Slump Dense Concrete – Dry Pack– Conventional Concrete & Mortar– Shotcrete
• Wet Process– High Pressure– Low Pressure
• Dry Process– Silica Fume Concrete – Sulfur Concrete
– Cement-Based Grout– Proprietary Repair Mortars– Rapid Setting Cementitious– Magnesium Phosphate– Polymer Based
• Epoxies-mortars, adhesives, coatings
• Polyurethanes-sealants, coatings
• Polyureas-sealants, coatings
• Methacrylates-mortars, injection, coatings
• Polyesters-mortars, coatings
• Silicones-sealants
• FRP Strengthening
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Repair Application Guide (developmental ICRI 320.1 M&M)
Batch Size
Mixer Type
Application Method
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From ICRI 320.1
What are we trying
to accomplish?
What problem did we
inherit?
What do we have to
work around?
What is “unusual”
with the material?
What does the “boss”
(owner) want??
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CompromisesCracking Resistance
�Creep
�Tensile Strength
�Modulus
�Bond Strength
�Length Change
�Thermal Expansion
�Flexural Strength
Durability
�Cracking Resistance
�Freeze Thaw Resistance
�Scaling resistance
�Chloride Ion Permeability
�Sulfate Resistance
�Chemical Resistance
�Abrasion Resistance
Serviceability�Time to Usage
�Compatibility
�Esthetics
�Strength
Economics�Repair or Replace?
�Material Cost
�Installed Cost
�Service Life
Service Conditions
� Chemical Resistance
� Moisture Intrusion
� Abrasion Resistance
� Cleanability
Environmental Conditions
� Exposure Temperature
� Freeze/Thaw
� High Temperature
� Thermal Shock
� Reinforcement Protection
Application Constraints
�Environmental Considerations
�Utilities
�Surface Preparation Options
�Access
�Return to Service Time
�Orientation of Application
�Volume of Material to be Used
CODES
and
SPECIFICATIONS
Material
Availability
Design and
Maintain Concrete
to Prevent
Repairing
It!
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Early-Age Repair Material Properties
Repairs Performed at Early Ages Early Age Material Properties
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What to Do?Existing construction
• Ok, you inherit the problem• Address problems early in the life cycle
• Find the root cause of problems and fix
• Address cracks– Assume all cracks are likely to move
– If structural, get help!
• Keep water out & Protect from chemical attack– Coatings, water repellants
– Drainage
• Know when to walk away
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ACI 308Typical Conditions
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Cement Grains = granular solid + air =
Free flowing powder
Cement + Water = granular solid + water =
Fluid of more or less stability
Settlement ShrinkageOccurs within the concrete paste as air voids collapse and aggregates wet outCracks may form over areas of restraint (i.e., rebar)Settlement may also create pockets under rebar and aggregates.Bleeding is also settlement
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Early Cracking
• Plastic ShrinkageDampen Base if No Vapor RetarderAvoid Use of Under Slab Vapor Retarder
Use Moisture Retaining Coverings/Evaporation Retarders/FibersWind, Sun, Temperature, RH, Mix DesignPostpone Finishing Steps
H2OH2O
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Cement Hydrates
Consumption of water, hydrate rims
form.
=
Increase in viscosity.
Shearing that occurs can be replaced by
new hydration.
Hydration continues
Hydrates begin to interlock.
=
Setting begins
Finishing occurs
Shearing will weaken concrete after
setting
At Early Ages
Creep is high
Shrinkage is high
Porosity is high
Strength is low
Cement exotherms = Thermal stress
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Drying of Concrete- One Side
Time→
Drying Rate→
Stage 1 Bleed water on surface evaporates
Stage 2 Water evaporates from pores refilled from within
concrete = settlement & plastic cracking
Stage 3 Water evaporates from within as vapor =
drying shrinkage
Kanare, H. Concrete Floors & Moisture,
Eng. Bulletin #119 PCA/NRMCA, 2005
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Hydration continues
Porosity decreases
Pore water may be consumed or evaporate
=
Curing Required
Drying shrinkage begins
Freezing will destroy concrete.
A review of early-age properties of cement-based materials
D.P. Bentz
Penetration resistance vs. time
with different W/C
Porosity decrease vs. time with
different W/C
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Curing Induced Strength Variations
Up to 50% Strength Improvement if Properly Cured
ACI 308R
Rate of Strength Development is Much Faster at Early Ages
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Water Permeability vs Curing for Different W/C
ACI 308
With Water Permeability Comes:
•Chloride Ingress (Steel Corrosion)
•F/T Deterioration
•AAR
•Sulfate Attack
•ETC
Permeability Rate is HIGH at Early
Ages
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Drying Shrinkage:
Thinner sections dry (and shrink) faster% of Ultimate Shrinkage
Time (0--------------------------24 Months)
12” Thick
Slab
2” Thick
Slab
8” Thick
Slab
Shrinkage is FASTER at Early Ages
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Concrete becomes a
Hard
Wet
Sponge
A review of early-age properties of cement-based
materials
D.P. Bentz
Boğaziçi University Dept. of Civil Engineering
Lecture Notes 3
Degree of Hydration vs.
Internal RH
Volume change vs. wet +
dry cycles
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Repair Materials– Ordinary Concrete
– Preplaced Aggregate Concrete
– Fiber Reinforced Concrete
– Ferrocement
– Low Slump Dense Concrete
– Dry Pack
– Conventional Concrete & Mortar
– Shotcrete• Wet Process
– High Pressure
– Low Pressure
• Dry Process
– Silica Fume Concrete – Sulfur Concrete
– Cement-Based Grout
– Proprietary Repair Mortars
– Rapid Setting Cementitious
– Magnesium Phosphate
– Polymer Based
• Epoxies-mortars, adhesives, coatings
• Polyurethanes-sealants, coatings
• Polyureas-sealants, coatings
• Methacrylates-mortars, injection, coatings
• Polyesters-mortars, coatings
• Silicones-sealants
• FRP Strengthening
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Epoxy degree of reaction vs. volume changeInvestigation of cure induced shrinkage in unreinforced epoxy resin
Zarrelli, Skordos, Partridge
□ο Specific Volume
●■ Degree of Conversion
Exotherm temperature
Post cure
Polymer Binder Curing Example (epoxy)
●●●●●●●●●●●
■■■■■■■■■■■■■■■■■■
□□□□□□□
οοοοοοοοοοοοο
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BASF Construction Chemicals
Fred Goodwin, Fellow Scientist
?