STRENGTHENING STRUCTURES USING FRP COMPOSITE MATERIALS

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STRENGTHENING STRUCTURES USING FRP COMPOSITE
MATERIALS

• DAMIAN I. KACHLAKEV, Ph.D., P.E.
• California Polytechnic State University
• San Luis Obispo

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WHY COMPOSITES?

• ADVANTAGES OVER TRADITIONAL MATERIALS
• CORROSION RESISTANCE
• HIGH STRENGTH TO WEIGHT RATIO
• LOW MAINTENANCE
• EXTENDED SERVICE LIFE
• DESIGN FLEXIBILITY

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COMPOSITES DEFINITION

• A combination of two or more materials
  (reinforcement, resin, filler, etc.), differing
  in form or composition on a macroscale. The
  constituents retain their identities, i.e.., they
  do not dissolve or merge into each other,
  although they act in concert. Normally, the
  components can be physically identified and
  exhibit an interface between each other.

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DEFINITION

• Fiber Reinforced Polymer (FRP) Composites are
  defined as
• A matrix of polymeric material that is
  reinforced by fibers or other reinforcing
  material

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COMPOSITES MARKETS

• TRANSPORTATION
• CONSTRUCTION
• MARINE
• CORROSION-RESISTANT
• CONSUMER
• ELECTRICAL/ELECTRONIC
• APPLIANCES/BUSINESS
• AIRCRAFT/DEFENSE

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U.S. COMPOSITES SHIPMENTS - 1996 MARKET
SHARE SEMI-ANNUAL STATISTICAL REPORT - AUGUST
26, 1996
Aircraft/Aerospace 0.7
Transportation 30.6
Construction 20
Other- 3.4
Consumer Products - 6
Marine - 11.6
Electrical/ Electronic - 10
Appliance/Business Equipment - 5.3
Corrosion-Resistant Equipment - 12.4
Includes reinforced thermoset and
thermoplastic resin composites, reinforcements
and fillers.
SOURCE SPI Composites Institute
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Infrastructure Benefits

• HIGH STRENGTH/WEIGHT RATIO
• ORIENTATED STRENGTH
• DESIGN FLEXIBILITY
• LIGHTWEIGHT
• CORROSION RESISTANCE
• LOW MAINTENANCE/LONG-TERM DURABILITY
• LARGE PART SIZE POSSIBLE
• TAILORED AESTHETIC APPEARANCE
• DIMENSIONAL STABILITY
• LOW THERMAL CONDUCTIVITY
• LOW INSTALLED COSTS

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FRP COMPOSITE CONSTITUENTS

• RESINS (POLYMERS)
• REINFORCEMENTS
• FILLERS
• ADDITIVES

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MATERIALS RESINS

• PRIMARY FUNCTION
• TO TRANSFER STRESS BETWEEN REINFORCING FIBERS
  AND TO PROTECT THEM FROM MECHANICAL AND
  ENVIRONMENTAL DAMAGE
• TYPES
• THERMOSET
• THERMOPLASTIC

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RESINS

• THERMOSET
• POLYESTER
• VINYL ESTER
• EPOXY
• PHENOLIC
• POLYURETHANE

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RESINS

• THERMOPLASTIC
• ACETAL
• ACRYRONITRILE BUTADIENE STYRENE (ABS)
• NYLON
• POLYETHYLENE (PE)
• POLYPROPYLENE (PP)
• POLYETHYLENE TEREPHTHALATE (PET)

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RESINS

• THERMOSET ADVANTAGES
• THERMAL STABILITY
• CHEMICAL RESISTANCE
• REDUCED CREEP AND STRESS RELAXATION
• LOW VISCOSITY- EXCELLENT FOR FIBER ORIENTATION
• COMMON MATERIAL WITH FABRICATORS

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RESINS

• THERMOPLASTIC ADVANTAGES
• ROOM TEMPERATURE MATERIAL STORAGE
• RAPID, LOW COST FORMING
• REFORMABLE
• FORMING PRESSURES AND TEMPERATURES

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POLYESTERS

• LOW COST
• EXTREME PROCESSING VERSATILITY
• LONG HISTORY OF PERFORMANCE
• MAJOR USES
• Transportation
• Construction
• Marine

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VINYL ESTER

• SIMILAR TO POLYESTER
• EXCELLENT MECHANICAL FATIGUE PROPERTIES
• EXCELLENT CHEMICAL RESISTANCE
• MAJOR USES
• Corrosion Applications - Pipes, Tanks, Ducts

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EPOXY

• EXCELLENT MECHANICAL PROPERTIES
• GOOD FATIGUE RESISTANCE
• LOW SHRINKAGE
• GOOD HEAT AND CHEMICAL RESISTANCE
• MAJOR USES
• FRP Strengthening Systems
• FRP Rebars
• FRP Stay-in-Place Forms

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PHENOLICS

• EXCELLENT FIRE RETARDANCE
• LOW SMOKE TOXICITY EMISSIONS
• HIGH STRENGTH AT HIGH TEMPERATURES
• MAJOR USES
• Mass Transit - Fire Resistance High Temperature
• Ducting

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POLYURETHANE

• TOUGH
• GOOD IMPACT RESISTANCE
• GOOD SURFACE QUALITY
• MAJOR USES
• Bumper Beams, Automotive Panels

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SUMMARY POLYMERS

• WIDE VARIETY AVAILABLE
• SELECTION BASED ON
• PHYSICAL AND MECHANICAL PROPERTIES OF PRODUCT
• FABRICATION PROCESS REQUIREMENTS

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Physical Properties of Thermosetting Resins Used
in Structural Composites
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MATERIAL FIBERREINFORCEMENTS

• PRIMARY FUNCTION
• CARRY LOAD ALONG THE LENGTH OF THE FIBER,
  PROVIDES STRENGTH AND OR STIFFNESS IN ONE
  DIRECTION
• CAN BE ORIENTED TO PROVIDE PROPERTIES IN
  DIRECTIONS OF PRIMARY LOADS

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REINFORCEMENTS

• NATURAL
• MAN-MADE
• MANY VARIETIES COMMERCIALLY AVAILABLE

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MAN-MADE FIBERS

• ARAMID
• BORON
• CARBON/GRAPHITE
• GLASS
• NYLON
• POLYESTER
• POLYETHYLENE
• POLYPROPYLENE

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FIBER PROPERTIESDENSITY (g/cm3)
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FIBER PROPERTIESTENSILE STRENGTH
x103 psi
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FIBER PROPERTIESSTRAIN TO FAILURE
()
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FIBER PROPERTIESTENSILE MODULUS
106 psi
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FIBER PROPERTIESCTE - Longitudinal
x10-6/0C
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FIBER PROPERTIESTHERMAL CONDUCTIVITY
x10-6/0C
BTU-in/hr-ft2 - 0F
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FIBER REINFORCEMENT

• GLASS (E-GLASS)
• MOST COMMON FIBER USED
• HIGH STRENGTH
• GOOD WATER RESISTANCE
• GOOD ELECTRIC INSULATING PROPERTIES
• LOW STIFFNESS

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GLASS TYPES

• E-GLASS
• S-GLASS
• C-GLASS
• ECR-GLASS
• AR-GLASS

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FIBER REINFORCEMENT

• ARAMID (KEVLAR)
• SUPERIOR RESISTANCE TO DAMAGE (ENERGY ABSORBER)
• GOOD IN TENSION APPLICATIONS (CABLES, TENDONS)
• MODERATE STIFFNESS
• MORE EXPENSIVE THAN GLASS

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FIBER REINFORCEMENT

• CARBON
• GOOD MODULUS AT HIGH TEMPERATURES
• EXCELLENT STIFFNESS
• MORE EXPENSIVE THAN GLASS
• BRITTLE
• LOW ELECTRIC INSULATING PROPERTIES

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TYPICAL PROPERTIES OF STRUCTURAL FIBERS
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ADVANTAGES AND DISADVANTAGES OF REINFORCING FIBERS
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FIBER ORIENTATION

• ANISOTROPIC
• UNIDIRECTIONAL
• BIAS - TAILORED DIRECTION
• 0O - flexural strengthening
• 90O - column wraps
• /- 45O - shear strengthening
• ANGLE VARIES BY APPLICATION

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DEGREE OF ANISOTROPY OF FRP COMPOSITES
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PROPERTIES OF UNIDIRECTIONAL COMPOSITES
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ELASTIC AND SHEAR MODULI OF FRP COMPOSITES
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REINFORCEMENTSSUMMARY

• TAILORING MECHANICAL PROPERTIES
• TYPE OF FIBER
• PERCENTAGE OF FIBER
• ORIENTATION OF FIBER

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COMPARISON OF AXIAL AND FLEXURAL EFFICIENCY OF
FRP SYSTEMS
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DESIGN VARIABLESFOR COMPOSITES

• TYPE OF FIBER
• PERCENTAGE OF FIBER or FIBER VOLUME
• ORIENTATION OF FIBER
• 0o, 90o, 45o, -45o
• TYPE OF POLYMER (RESIN)
• COST
• VOLUME OF PRODUCT - MANUFACTURING METHOD

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DESIGN VARIABLESFOR COMPOSITES

• PHYSICAL
• tensile strength
• compression strength
• stiffness
• weight, etc.
• ENVIRONMENTAL
• Fire
• UV
• Corrosion Resistance

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TAILORING COMPOSITE PROPERTIES

• MAJOR FEATURE
• PLACE MATERIALS WHERE NEEDED - ORIENTED STRENGTH
• LONGITUDINAL
• TRANSVERSE
• or between
• STRENGTH
• STIFFNESS
• FIRE RETARDANCY

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STRUCTURAL DESIGN APPROACH FOR COMPOSITES
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SPECIFIC MODULUS AND STRENGTH OF FRP COMPOSITE
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FLOW CHART FOR DESIGN OF FRP COMPOSITES
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MANUFACTURING PROCESSES

• Hand Lay-up/Spray-up
• Resin Transfer Molding (RTM)
• Compression Molding
• Injection Molding
• Reinforced Reaction Injection Molding (RRIM)
• Pultrusion
• Filament Winding
• Vacuum Assisted RTM (Va-RTM)
• Centrifugal Casting

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PROCESS CHARACTERISTICSHand Lay-up/Spray-up

• MAX SIZE Unlimited
• PART GEOMETRY Simple - Complex
• PRODUCTION VOLUME Low - Med
• CYCLE TIME Slow
• SURFACE FINISH Good - Excellent
• TOOLING COST Low
• EQUIPMENT COST Low

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PRODUCT CHARACTERISTICSPultrusion

• CONSTANT CROSS SECTION
• CONTINUOUS LENGTH
• HIGH ORIENTED STRENGTHS
• COMPLEX PROFILES POSSIBLE
• HYBRID REINFORCEMENTS

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MATERIAL PROPERTIES

• PROPERTIES OF FRP COMPOSITES VARY DEPENDING ON
• TYPE OF FIBER RESIN SELECTED
• FIBER CONTENT
• FIBER ORIENTATION
• MANUFACTURING PROCESS

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REPAIR

• HYBRIDS (SUPER COMPOSITES) TRADITIONAL MATERIALS
  ARE JOINED WITH FRP COMPOSITES
• WOOD
• STEEL
• CONCRETE
• ALUMINUM

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BENEFITS - SUMMARY

• LIGHT WEIGHT
• HIGH STRENGTH to WEIGHT RATIO
• COMPLEX PART GEOMETRY
• COMPOUND SURFACE SHAPE
• PARTS CONSOLIDATION
• DESIGN FLEXIBILITY
• LOW SPECIFIC GRAVITY
• LOW THERMAL CONDUCTIVITY
• HIGH DIELECTRIC STRENGTH

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LIFE CYCLE ECONOMICS

• PLANNING/DESIGN/DEVELOPMENT COST
• PURCHASE COST
• INSTALLATION COST
• MAINTENANCE COST
• LOSS/WEAR COST
• LIABILITY/INSURANCE COSTS
• DOWNTIME/LOST BUSINESS COST
• REPLACEMENT/DISPOSAL/RECYCLING COST

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LIFE CYCLE ECONOMICS (Examples)

• IBACH BRIDGE (SWITZERLAND)
• CFRP LAMINATES- 50 TIMES MORE EXPENSIVE THAN
  STEEL PER KILOGRAM
• CFRP LAMINATES- 9 TIMES MORE EXPENSIVE THAN STEEL
  BY VOLUME
• REPAIR WORK REQUIREMENTS-175 KG STEEL OR 6.2 KG
  CFRP
• MATERIAL COST-20 OF THE TOTAL PROJECT COST

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LIFE CYCLE ECONOMICS (Examples)

• HORSETAIL CREEK BRIDGE (OREGON)
• CONVENTIONAL REPAIR (SHEAR ONLY-ONE BEAM)-69,000
• FRP REPAIR (GFRP SHEAR ONLY-ONE BEAM)-1850
• FRP REPAIR SHEAR (GFRP) FLEXURE(CFRP), ONE
  BEAM- 9850

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CONCLUSIONS

• ECONOMICS ARE MORE THAN THE BASIC ELEMENTS OF
  MATERIALS, LABOR, EQUIPMENT, OVERHEAD, ETC.
• ENTIRE LIFE CYCLE ECONOMICS MUST BE CONSIDERED
  AND COMPARED TO THAT OF TRADITIONAL MATERIALS TO
  DETERMINE THE BENEFITS OF COMPOSITES IN A GIVEN
  APPLICATION

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STRUCTURAL DESIGN WITH FRP COMPOSITES
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EXTERNAL REINFORCEMENT OF RC BEAMS USING FRP

• BACKGROUND
• DESIGN MODELS
• LACK OF DUCTILITY
• FLEXURAL STRENGTHENING
• SHEAR STRENGTHENING
• PRESTRESSED FRP APPLICATION
• DESIGN METHODOLOGY AND ANALYSIS
• OTHER ISSUES
• FATIGUE, CREEP, LOW TEMPERATURE FRP PERFORMANCE
• DESIGN EXAMPLES

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FRP STRENGTHENED BEAMSBACKGROUND

• FRP VS. EXTERNALLY STEEL BONDED PLATES
• CORROSION AT THE EPOXY-STEEL INTERFACE
• STEEL PLATES DO NOT INCREASE STRENGTH, JUST
  STIFFNESS
• HIGH TEMPERATURES PERFORMANCE DIFFICULTIES DUE TO
  HEAVY WEIGHT OF THE STEEL PLATES
• STRENGTHENING DESIGN BASED ON MATERIAL WEIGHT,
  NOT STRUCTURAL NEEDS
• CONSTRUCTION DIFFICULTIES
• TIME CONSUMING, HEAVY EQUIPMENT NEEDED

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FRP STRENGTHENED BEAMSLACK OF DUCTILITY

• LINEAR STRESS-STRAIN PROFILE
• DEFINITION OF DUCTILITY
• DEFLECTION AT ULTIMATE/DEFLECTION AT YIELD- NOT
  APPLICABLE FOR FRP MATERIAL
• STRAIN-ENERGY ABSORPTION, I.E., AREA UNDER
  LOAD-DEFLECTION CURVE- OK FOR FRP COMPOSITES
• IN GENERAL- THE HIGHER THE FRP FRACTION AREA, THE
  LOWER THE ENERGY ABSORPTION OF THE STRENGTHENED
  CONCRETE BEAM

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FRP STRENGTHENED BEAMS
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TYPICAL LOAD-DEFLECTION CURVE
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FRP REINFORCED BEAMS- FAILURE MODES
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FRP REINFORCEMENT OF RC COLUMNS

• Advantages of Strengthening Columns with FRP
  Jackets
• Increased Ductility
• Increased Strength
• Low Dead Weight
• Reduced Construction Time
• Low Maintenance

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FRP REINFORCEMENT OF RC COLUMNS

• Factors Influencing the Behavior of
  FRP-Retrofitted Columns
• Column composition
• Column geometry
• Current condition
• Type of loading
• Environmental conditions

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DESIGN OF FRP RETROFIT OF RC COLUMNS

• Shear Strengthening
• Flexural Hinge Confinement
• Lap Splice Clamping

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LOAD-DISPLACEMENT CURVE(Before Strengthening)
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LOAD-DISPLACEMENT CURVE(After Strengthening)
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COLUMN DUCTILITY
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FRP REINFORCEMENT OF RC COLUMNS

• Advantages of Strengthening Columns with FRP
  Jackets
• Increased Ductility
• Increased Strength
• Low Dead Weight
• Reduced Construction Time
• Low Maintenance

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FRP REINFORCEMENT OF RC COLUMNS

• Factors Influencing the Behavior of
  FRP-Retrofitted Columns
• Column composition
• Column geometry
• Current condition
• Type of loading
• Environmental conditions

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LOAD-DISPLACEMENT CURVE(Before Strengthening)
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LOAD-DISPLACEMENT CURVE(After Strengthening)
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COLUMN DUCTILITY
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CONSTRUCTION PROCESS

• Preparation of the Concrete Surface
• Mixing Epoxy, Putty, etc.
• Preparation of the FRP Composite System
• Application of the FRP Strengthening System
• Anchorage (if recommended)
• Curing the FRP Material
• Application of Finish System

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CONCRETE SURFACE PREPARATION

• Repair of the existing concrete in accordance to
• ACI 546R-96 Concrete Repair Guide
• ICRI Guideline No. 03370 Guide for Surface
  Preparation for the Repair of Deteriorated
  Concrete...
• Bond Between Concrete and FRP Materials
• Should satisfy ICRI Guide for Selecting and
  Specifying Materials for Repair of Concrete
  Surfaces

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CONCRETE SURFACE PREPARATION

• Repair Cracks 0.010 inches or Wider
• Epoxy pressure injected
• To satisfy Section 3.2 of the ACI 224.1R-93
  Causes, Evaluation and Repair of Cracks
• Concrete Surface Unevenness to be Less than 1 mm
• Concrete Corners- Minimum Radius of 30 mm

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APPLICATION OF THE FRP COMPOSITE

• In Accordance to Manufacturers and Designer's
  Specifications
• Priming
• Putty Application
• Under-coating with Epoxy Resin
• Application of the FRP Laminate/ FRP Fiber Sheet
• Over-coating with Epoxy Resin

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CURING OF THE FRP COMPOSITES

• In Accordance to Manufacturers Specifications
• Temperature ranges and Curing Time- varies from
  few hours to 15 days for different FRP systems
• Cured FRP Composite
• Uniform thickness and density
• Lack of porosity

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CONSTRUCTION PROCESS

• Typical RC Beam in Need for Repair
• corroded steel
• spalling concrete

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CONSTRUCTION PROCESS

• Deteriorated Column / Beam Connection

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CONSTRUCTION PROCESS

• Concrete Surface Preparation
• Smooth, free of dust and foreign objects, oil,
  etc.
• Application of primer and putty (if required by
  the manufacturer)

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CONSTRUCTION PROCESS

• Preparation of the FRP Composites for Application
• Follow manufacturers recommendations

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CONSTRUCTION PROCESS

• Priming of the Concrete Surface
• Application of the Undercoating epoxy Layer
  (adhesive when FRP pultruded laminates are used)

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CONSTRUCTION PROCESS

• Application of CFRP Fiber Sheet on a Beam- Wet
  Lay-Up Process
• Similar for Application of Pultruded Laminates

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CONSTRUCTION PROCESS

• Column Wrapping with Automated FRP Application
  device

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CONSTRUCTION PROCESS

• Robo Wrapper by Xxsys Technologies

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CONSTRUCTION PROCESS

• Column Wrapping Device