slide1 l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Durability of FRP Composites for Construction PowerPoint Presentation
Download Presentation
Durability of FRP Composites for Construction

Loading in 2 Seconds...

play fullscreen
1 / 77

Durability of FRP Composites for Construction - PowerPoint PPT Presentation


  • 429 Views
  • Uploaded on

ISIS Educational Module 8:. Durability of FRP Composites for Construction. Produced by ISIS Canada. Composites. FRP. For Construction. Module Objectives. To provide students with a general awareness of important durability consideration for FRPs

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Durability of FRP Composites for Construction' - makya


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

ISIS Educational Module 8:

Durability of FRP Composites for Construction

Produced by ISIS Canada

slide2

Composites

FRP

For Construction

Module Objectives

To provide students with a general awareness of important durability consideration for FRPs

To facilitate and encourage the use of durable FRPs and systems in the construction industry

To provide guidance for students seeking additional information on the durability of FRP materials

ISIS EC Module 8

slide3

Composites

FRP

For Construction

Introduction & Overview

Reduction Factors

Case Study

Specifications

Moisture & Marine Exposures

Alkalinity & Corrosion

High Temperatures & Fire

Creep

Fatigue

Cold Temperatures & Freeze-Thaw

UV Radiation

Outline

ISIS EC Module 8

slide4

Composites

FRP

For Construction

Introduction & Overview

Section:

1

  • The problem:

In recent years, our infrastructure systems have been deteriorating at an increasing and alarming rate

New materials that can be used to prolong and extend the service lives of existing structures ??

Fibre Reinforced Polymers (FRPs)

ISIS EC Module 8

slide5

Composites

FRP

For Construction

Introduction & Overview

Section:

1

Key uses of FRPs in construction:

  • Internal reinforcement of concrete

Corrosion of steel reinforcement in concrete structures contributes to infrastructure deterioration

Use non-corrosive FRP reinforcement

  • External strengthening of concrete

Provide external tension or confining reinforcement

(FRP plates, sheets, bars, etc.)

ISIS EC Module 8

slide6

Composites

FRP

For Construction

High-strength fibres

Polymer matrix

Introduction & Overview

Section:

1

What is FRP?

  • FRP is a composite:

Composite = combination of two or more materials to form a new and useful material with enhanced properties in comparison to the individual constituents (concrete, wood, etc.)

  • FRPs consist of:
    • Fibres
    • Matrix

ISIS EC Module 8

slide7

Composites

FRP

For Construction

Introduction & Overview

Section:

1

Polymer matrix

Polymer matrix:

As the binder for the FRP, the matrix roles include:

  • Binding the fibres together
  • Protecting the fibres from environmental degradation
  • Transferring force between the individual fibres
  • Providing shape to the FRP component

ISIS EC Module 8

slide8

Composites

FRP

For Construction

Introduction & Overview

Section:

1

Polymer matrix

Commonly used matrices:

Internal reinforcing applications

  • Vinylester: fabrication for FRP reinforcing bars

(superior durability characteristics when embedded in concrete)

External strengthening applications

  • Epoxy: strengthening using FRP sheets/plates

(superior adhesion characteristics)

ISIS EC Module 8

slide9

Composites

FRP

For Construction

Introduction & Overview

Section:

1

Fibres

Fibres:

Provide strength and stiffness of FRP

  • Protected against environmental degradation by the polymer matrix
  • Oriented in specified directions to provide strength along specific axes (FRP is weaker in the directions perpendicular to the fiber)
  • Selected to have:

ISIS EC Module 8

slide10

Composites

FRP

For Construction

Introduction & Overview

Section:

1

Fibres

  • Three most common fibres in Civil Engineering applications:
    • Glass
    • Carbon
    • Aramid (not common in North America)
  • Required strength and stiffness
  • Durability considerations
  • Cost constraints
  • Availability of materials

Selected based on:

ISIS EC Module 8

slide11

Composites

FRP

For Construction

Introduction & Overview

Section:

1

Fibres

Glass fibres:

  • Inexpensive
  • Most commonly used in structural applications
  • Several grades are available:
    • E-Glass
    • AR-Glass (alkali resistant)
  • High strength, moderate modulus, medium density
  • Used in non weight/modulus critical applications

ISIS EC Module 8

slide12

Composites

FRP

For Construction

Introduction & Overview

Section:

1

Fibres

Carbon fibres:

  • Significantly higher cost than glass
  • High strength, high modulus, low density
    • E = 250-300 GPa: standard
    • E = 300-350 GPa: intermediate
    • E = 350-550 GPa: high
    • E = 550-1000 GPa: ultra-high
  • Superior durability and fatigue characteristics
  • Used in weight/modulus critical applications

ISIS EC Module 8

slide13

Composites

FRP

For Construction

Introduction & Overview

Section:

1

Fibres

Aramid fibres:

  • Moderate to high cost
  • Two grades available:60 GPa and 120 GPa elastic moduli
  • High tensile strength, moderate modulus, low density
  • Low compressive and shear strength
  • Some durability concerns
    • Potential UV degradation
    • Potential moisture absorption and swelling

ISIS EC Module 8

slide14

Composites

FRP

For Construction

Mechanical Properties

Section:

1

Type of fibre and matrix

FRP mechanical properties are a function of:

Fibre volume content

Orientation of fibres

Here we are concerned mainly with unidirectional FRPs!

ISIS EC Module 8

slide15

Composites

FRP

For Construction

2500

2000

1500

Stress [MPa]

1000

500

1

2

3

Strain [%]

FRP vs. Steel

Section:

1

Mechanical Properties

  • FRP properties

(in general versus steel):

    • Linear elastic behaviour to failure
    • No yielding
    • Higher ultimate strength
    • Lower strain at failure
    • Comparable modulus (carbon FRP)

CFRP

GFRP

Steel

ISIS EC Module 8

slide16

Composites

FRP

For Construction

Material

200 GPa

Failure Strain

2-2.6 %

50-74 GPa

147-165 GPa

2-4.5 %

30-55 GPa

>10 %

Elastic Modulus

1-1.5 %

Ultimate Strength

Glass FRP

517-1207 MPa

Carbon FRP

1200-2410 MPa

Aramid FRP

1200-2068 MPa

Steel

483-690 MPa

Quantitative Comparison

Section:

1

Typical Mechanical Properties*

* Based on 2001 data for specific FRP rebar products

ISIS EC Module 8

slide17

Composites

FRP

For Construction

Introduction & Overview

Section:

1

FRP

Physical, mechanical, durability properties of FRPs

  • Overall properties and durability depend on:
  • The properties of the specific polymer matrix
  • The fibre volume fraction

(i.e., volume of fibres per unit volume of matrix)

  • The fibre cross-sectional area
  • The orientation of the fibres within the matrix
  • The method of manufacturing
  • Curing and environmental exposure

ISIS EC Module 8

slide18

Composites

FRP

For Construction

Unidirectional glass FRP bar

Glass FRP grid

Carbon FRP prestressing tendon

Glass fibre roving

Carbon fibre roving

Introduction & Overview

Section:

1

Examples of FRP

ISIS EC Module 8

slide19

Composites

FRP

For Construction

Introduction & Overview

Section:

1

FRPs

  • In the design and use of FRP materials
    • The orientation of the fibres within the matrix is a key consideration
  • Most important parameters for infrastructure FRPs:

Uniaxial tensile properties

→ strength and elastic modulus

FRP-concrete bond characteristics

→transfer and carry the tensile loads

Durability

ISIS EC Module 8

slide20

Composites

FRP

For Construction

Introduction & Overview

Section:

1

What is durability?

  • The ability of an FRP material to:

“resist cracking, oxidation, chemical degradation, delamination, wear, and/or the effects of foreign object damage for a specified period of time, under the appropriate load conditions, under specified environmental conditions”

ISIS EC Module 8

slide21

CAUTION!

Composites

FRP

For Construction

Section:

1

  • Data on the durability of FRP materials is limited
    • Appears contradictory in some cases
    • Due to many different forms of FRPs and fabrication processes
  • FRPs used in civil engineering applications are substantially different from those used in the aerospace industry
    • Their durability cannot be assumed to be the same
  • Anecdotal evidence suggests that FRP materials can achieve outstanding longevity in infrastructure applications

ISIS EC Module 8

slide22

Composites

FRP

For Construction

Introduction & Overview

Section:

1

Durability

Environments

  • All engineering materials are subject to mechanical and physical deterioration with time, load, and exposure to various harmful environments
  • FRP materials are very durable, and are less susceptible to degradation than many conventional construction materials

ISIS EC Module 8

slide23

Composites

FRP

For Construction

Introduction & Overview

Section:

1

Durability

Factors affecting FRPs’ durability performance:

  • The matrix and fibre types
  • The relative portions of the constituents
  • The manufacturing processes
  • The installation procedures
  • The short- and long-term loading and exposure condition (physical and chemical)

ISIS EC Module 8

slide24

Composites

FRP

For Construction

Introduction & Overview

Section:

1

Durability

Potentially harmful effects for FRP:

Environmental Effects

Physical Effects

Moisture & Marine Environments

Alkalinity& Corrosion

Sustained Load:

Creep

DURABILITY

OF FRPs

Heat & Fire

Cyclic loading:

Fatigue

Cold & Freeze-Thaw Cycling

Ultraviolet Radiation

POTENTIAL SYNERGIES

ISIS EC Module 8

slide25

Composites

FRP

For Construction

Moisture & Marine Exposures

Section:

2

  • FRPs are particularly attractive for concrete structures in moist or marine environments
    • FRPs are not susceptible to electrochemical corrosion
    • Corrosion of steel in conventional structures results in severe degradation

HOWEVER

FRPs are not immune to the potentially harmful effects of moist or marine environments

ISIS EC Module 8

slide26

Composites

FRP

For Construction

Moisture & Marine Exposures

Section:

2

Moisture

  • Some FRP materials have been observed to deteriorate under prolonged exposure to moist environments
    • Evidence linking the rate of degradation to the rate of sorption of fluid into the polymer matrix
  • All polymers will absorb moisture
    • Depending on the chemistry of the specific polymer involved, can cause reversible or irreversible physical, thermal, mechanical and/or chemical changes
  • It is important to recognize that…
    • Results from laboratory testing are not necessarily indicative of performance in the field

ISIS EC Module 8

slide27

Composites

FRP

For Construction

Moisture & Marine Exposures

Section:

2

Moisture

Selected factors affecting moisture absorption in FRPs:

  • Type and concentration of liquid
  • Type of polymer and fibre
  • Fibre-resin interface characteristics
  • Manufacturing / application method
  • Ambient temperature
  • Applied stress level
  • Extent of pre-existing damage
  • Presence of protective coatings

ISIS EC Module 8

slide28

Composites

FRP

For Construction

Moisture & Marine Exposures

Section:

2

Moisture

Overall effects of moisture absorption:

Moisture absorption

Plasticization of the matrix caused by interruption of Van der Walls bonding between polymer chains

Reduced matrix strength, modulus, strain at failure & toughness

Subsequently reduced matrix-dominated properties: Bond, shear, flexural strength & stiffness

May also affect longitudinal tensile strength & stiffness

Swelling of the matrix causes irreversible damage through matrix cracking & fibre-matrix debonding

ISIS EC Module 8

slide29

Composites

FRP

For Construction

< 1%

% Mass Gain

0

1

2

Time (years)

Moisture & Marine Exposures

Section:

2

Moisture

Typical moisture absorption trend for a matrix polymer:

ISIS EC Module 8

slide30

Composites

FRP

For Construction

100 %

% Strength Retention

10

0

5

Time (years)

Moisture & Marine Exposures

Section:

2

Moisture

Strength loss trend of typical FRPs due to moisture absorption:

Note: no strength reductions in

some lab studies

Further research needed

ISIS EC Module 8

slide31

Composites

FRP

For Construction

Moisture & Marine Exposures

Section:

2

Potentially Important degradation synergies:

  • Moisture absorption
  • Sustained stress
  • Elevated temperatures

Stress-induced micro-cracking of the polymer matrix

Moisture-induced micro-cracking of polymer matrix in a GFRP

ISIS EC Module 8

slide32

Composites

FRP

For Construction

Moisture & Marine Exposures

Section:

2

Fibres

The effect of moisture on fibres’ performance:

  • Glass fibres:

Moisture penetration to the fibres may extract ions from the fibre and result in etching and pitting. can cause deterioration of tensile strength and elastic modulus

  • Aramid fibres:

Can result in fibrillation, swelling of the fibres, and reductions in compressive, shear, and bond properties. Certain chemicals such as sodium hydroxide and hydrochloric acid can cause severe hydrolysis

  • Carbon fibres:

Do not appear to be affected by exposure to moist environments

ISIS EC Module 8

slide33

Composites

FRP

For Construction

Moisture & Marine Exposures

Section:

2

Resins

FRPs can be protected against moisture absorption by appropriate selection of matrix materials and protective coatings:

Vinylester:

currently considered the best for use in preventing moisture effects in infrastructure composites

Epoxy:

also considered adequate

Polyester:

Available research also suggests poor performance and should typically not be used

ISIS EC Module 8

slide34

Composites

FRP

For Construction

pH > 11

GFRP bar

Alkalinity & Corrosion

Section:

3

Alkalinity

Effects of alkalinity on FRPs’ performance:

  • The pH level inside concrete is > 11 (i.e., highly alkaline)
  • Becomes important for internal FRP reinforcement applications within concrete (particularly for GFRP)

Protection by matrix

Level of applied stress

Temperature

Damage to glass fibres depends on

ISIS EC Module 8

slide35

Composites

FRP

For Construction

GFRP bar

Alkalinity & Corrosion

Section:

3

Alkalinity

Degradation mechanisms for GFRP reinforcement:

Reduction in tensile properties

Damage at the fibre-resin interface

Alkaline solutions cause embrittlement of the fibres

Alkaline solutions

ISIS EC Module 8

slide36

Composites

FRP

For Construction

Alkalinity & Corrosion

Section:

3

Alkalinity

The effect of alkaline environments on fibres:

  • E-glass fibres

Strength reduction of 0 – 75 % of initial values

  • AR-glass fibres

Significant improvement in alkaline environments, but $$$

  • Aramid fibres

Strength reduction of 10 – 50 % of initial values

Need further research

  • Carbon fibres

Strength reduction of 0 – 20 % of initial values

ISIS EC Module 8

slide37

Composites

FRP

For Construction

Alkalinity & Corrosion

Section:

3

Corrosion

Galvanic Corrosion:

  • FRPs are not susceptible to electrochemical corrosion
    • Certain FRPs (e.g., CFRPs) can contribute to increased corrosion of metal components through galvanic corrosion

Galvanic corrosion = accelerated corrosion of a metal due to electrical contact with a nonmetallic conductor in a corrosive environment

ISIS EC Module 8

slide38

Composites

FRP

For Construction

Steel bar

CFRP bar

Spacer

Steel girder

GFRP sheet

CFRP sheet

Alkalinity & Corrosion

Section:

3

Corrosion

Guarding against galvanic corrosion:

  • CFRPs should not be permitted to come in to direct contact with steel or aluminum in structures
  • Internal reinforcement:

place plastic spacers

between steel and CFRP bars

  • External strengthening:

apply a thin layer of epoxy or GFRP sheet between CFRP and steel

ISIS EC Module 8

slide39

Composites

FRP

For Construction

High Temperatures & Fire

Section:

4

  • FRP materials are now widely used for reinforcement and rehabilitation of bridges and other outdoor structures
    • FRPs have seen comparatively little use in building applications
  • FRP materials are susceptible to elevated temperatures
    • Several concerns associated with their behaviour during fire or in high temperature service environments
  • Extremely difficult to make generalizations regarding high temperature behaviour
    • Large number of possible fibre-matrix combinations, manufacturing methods, and applications

ISIS EC Module 8

slide40

Composites

FRP

For Construction

High Temperatures & Fire

Section:

4

FRPs used in infrastructure applications suffer degradation of mechanical and/or bond properties at temperatures exceeding their glass transition temperature

  • Glass transition temperature, Tg

the midpoint of the temperature range over which an amorphous material (such as glass or a high polymer) changes from (or to) brittle, vitreous state to (or from) a rubbery state (ACI 440 2006)

All organic polymer materials combust at high temperatures

Most matrix polymers release large quantities of dense, black, toxic smoke

ISIS EC Module 8

slide41

Composites

FRP

For Construction

High Temperatures & Fire

Section:

4

Potential problems of FRPs under fire:

External FRP strengthening

Internal FRP reinforcement

Too thin for self-insulating layer, loss of bond at T > Tg

Sudden and severe loss of bond at T > Tg

ISIS EC Module 8

slide42

Composites

FRP

For Construction

High Temperatures & Fire

Section:

4

  • Mechanical properties of FRPs deteriorate with increasing temperature
    • “Critical” temperature commonly taken to be Tg for the polymer matrix
    • Typically in the range of 65-120ºC
    • Exceeding Tgresults in severe degradation of matrix dominated properties such as transverse and shear strength and stiffness
    • Longitudinal properties also affected above Tg
  • Tensile strength reductions as high as 80% can be expected in the fibre direction at temperatures of only 300ºC

Important that an FRP component not be exposed to temperatures close to or above Tg during the normal range of operating temperatures

ISIS EC Module 8

slide43

Composites

FRP

For Construction

High Temperatures & Fire

Section:

4

Degradation of mechanical properties is mainly governed by the properties of the matrix:

Carbon fibres

No degradation in strength and stiffness up to 1000 ºC

Glass fibres

20-60% reduction in strength at 600 ºC

Aramid fibres

20-60% reduction in strength at 300 ºC

ISIS EC Module 8

slide44

Composites

FRP

For Construction

High Temperatures & Fire

Section:

4

Deterioration of mechanical and bond properties for GFRP bars:

Critical temperature (T > Tg)

ISIS EC Module 8

slide45

Composites

FRP

For Construction

High Temperatures & Fire

Section:

4

The use of FRP internal reinforcement is currently not recommended for structures in which fire resistance is essential to maintain structural integrity

Exposure to elevated temperatures for a prolonged period of time may be a concern with respect to exacerbation of moisture absorption and alkalinity effects

ISIS EC Module 8

slide46

Composites

FRP

For Construction

Cold Temperatures

Section:

5

  • Potential for damage due to low temperatures and thermal cycling must be considered in outdoor applications
  • Freezing and freeze-thaw cycling may affect the durability performance of FRP components through:
    • Changes that occur in the behaviour of the component materials at low temperatures
    • Differential thermal expansion
      • between the polymer matrix and fibre components
      • between concrete and FRP materials
  • Could result in damage to the FRP or to the interface between FRP components & other materials

ISIS EC Module 8

slide47

Composites

FRP

For Construction

Cold Temperatures

Section:

5

Exposure to subzero temperature may result in residual stresses in FRPs due to matrix stiffening and different CTEs between fibres and matrix

Stiffness

Strength

Dimensional stability

Fatigue resistance

Moisture absorption

Resistance to alkalinity

Matrix micro-cracking and fibre-matrix bond degradation

May affect FRPs’

ISIS EC Module 8

slide48

Composites

FRP

For Construction

Cold Temperatures

Section:

5

Increased severity of matrix cracks

Increased matrix brittleness

Decreased tensile strength

Increasing # of freeze/thaw cycles

HOWEVER

The effects on FRP properties appear to be minor in most infrastructure applications

ISIS EC Module 8

slide49

Composites

FRP

For Construction

Ultraviolet Radiation

Section:

6

Ultraviolet (UV) radiationdamages most polymer matrices

Aramid fibres: significant

Glass fibres: insignificant

Carbon fibres: insignificant

The effects of UV on:

Thus, potential for UV degradation is important when FRPs are exposed to direct sunlight

ISIS EC Module 8

slide50

Composites

FRP

For Construction

Ultraviolet Radiation

Section:

6

Photodegradation: UV radiation within a certain range of specific wavelengths breaks chemical bonds between polymer chains and resulting in:

  • Discoloration
  • Surface oxidation
  • Embrittlement
  • Microcracking of the matrix

UV-induced surface flaws can cause:

  • Stress concentrations → may lead to premature failure
  • Increased susceptibility to damage from alkalinity & moisture

ISIS EC Module 8

slide51

Composites

FRP

For Construction

Ultraviolet Radiation

Section:

6

Combined effects of UV and moisture on FRP bars:

  • CFRP: tensile strength reduction of 0-20 %
  • GFRP: tensile strength reduction of 0-40 %
  • AFRP: tensile strength reduction of 0-30 %

Protection of FRPs from UV radiation:

  • UV resistant paints
  • Coatings
  • Sacrificial surfaces
  • UV resistant polymer resins

ISIS EC Module 8

slide52

Composites

FRP

For Construction

Steel

Steel

P

P

P

P

Creep & Creep Rupture

Section:

7

Creep: A behaviour of materials wherein an increase in strain is observed with time under a constant level of stress (L = final length)

L1

L1

P = P

L > L1

P = P

L = L1

with creep

ideal

ISIS EC Module 8

slide53

Composites

FRP

For Construction

Steel

Steel

P

P

P

P

Creep & Creep Rupture

Section:

7

Relaxation: a reduction in stress in a material with time at a constant level of strain (P = final load)

L1

L1

1

1

P > P1

L = L1

P = P

L = L1

ideal

with relaxation

ISIS EC Module 8

slide54

Composites

FRP

For Construction

Creep & Creep Rupture

Section:

7

Creep

Effects of creep on the performance of FRPs:

  • Fibres → relatively insensitive to creep in absence of other harmful durability factors
  • Matrices→ highly sensitive to creep

Thus, creep is potentially important for FRP

(Because loads must be transferred through the matrix)

ISIS EC Module 8

slide55

Composites

FRP

For Construction

Creep & Creep Rupture

Section:

7

Creep

  • For good performance under sustained loads:
    • Use an appropriate matrix material
    • Take care during the fabrication and curing processes
  • Creep behaviour of different FRP materials is complex and depends on:
    • Specific constituents and fabrication
    • Type, direction, and level of loading applied
    • Exposure to other durability factors such as alkalinity, moisture, thermal exposures
  • Few standard test methods for creep testing FRP materials
    • Difficult to make generalizations about FRPs’ creep performance

ISIS EC Module 8

slide56

Composites

FRP

For Construction

Creep & Creep Rupture

Section:

7

Creep Rupture

Under certain conditions… creep can result in rupture of FRPs at sustained load levels that are significantly less than ultimate

Called Stress Rupture, Creep Rupture, or Stress Corrosion

Creep rupture is influenced largely by the types of fibres and susceptibility to alkaline environments (glass FRPs in particular)

ISIS EC Module 8

slide57

Composites

FRP

For Construction

Sustained stress

Ultimate strength

Creep & Creep Rupture

Section:

7

Endurance time: the time to creep rupture of FRPs under a given level of sustained load

Endurance time

  • Other factors influencing endurance time include:
    • Elevated temperature
    • Alkalinity
    • Moisture
    • Freeze-thaw cycling
    • UV exposure

Endurance time

ISIS EC Module 8

slide58

Composites

FRP

For Construction

Creep & Creep Rupture

Section:

7

Creep rupture stress limits for FRP reinforcing bars (50 years creep rupture strength) :

  • GFRP: 29-55 % of initial tensile strength
  • AFRP: 47-66 % of initial tensile strength
  • CFRP: 79-93 % of initial tensile strength

Note: Laboratory testing is not necessarilyrepresentative of field performance

ISIS EC Module 8

slide59

Composites

FRP

For Construction

Fatigue

Section:

8

Fatigue: all structures are subjected to repeated cycles of loading and unloading due to:

  • Traffic and other moving loads
  • Thermal effects (differential thermal expansion)
  • Wind-induced or mechanical vibrations

Fatigue performance of most FRPs is as good as or better than steel

ISIS EC Module 8

slide60

Composites

FRP

For Construction

Fatigue

Section:

8

Good fatigue performance of FRPs depends on:

  • Toughness of the matrix
  • Ability to resist cracking

Performance of FRPs under fatigue load:

  • CFRP: best
  • GFRP: good
  • AFRP: excellent

NOTE: Fatigue performance of FRP reinforced concrete appears to be best when GFRP reinforcement is used

ISIS EC Module 8

slide61

Composites

FRP

For Construction

Reduction Factors

Section:

9

  • Numerous factors exist that can potentially affect the long term durability of FRP materials in civil engineering and construction applications
  • Durability factorsremain incompletely understood
  • Reduction factors in existing design codes and recommendations:
    • Applied to the nominal stress and strain capacities of FRPs
    • limit the useable ranges of stress and strain in engineering design

ISIS EC Module 8

slide62

Composites

FRP

For Construction

Reduction Factors (FRP bars)

Section:

9

For non-prestressed FRPs

Document

Material

Exposure Condition

Reduction Factor

CHBDC, 2006

AFRP

All

0.60

CFRP

All

0.75

GFRP

All

0.50

CSA S806-02

All

All

0.75

ACI 440.1R-06

AFRP

Not exposed to earth and weather

0.90

Exposed to earth and weather

0.80

CFRP

Not exposed to earth and weather

1.00

Exposed to earth and weather

0.90

GFRP

Not exposed to earth and weather

0.80

Exposed to earth and weather

0.70

ISIS EC Module 8

slide63

Composites

FRP

For Construction

Reduction Factors

Section:

9

Sustained (service) stress levels are limited to avoid creep rupture and other forms of distress:

Document

FRP Bars

Stress limit (% of ultimate)

CHBDC, 2006

AFRP

35

CFRP

65

GFRP

25

CSA S806-02

GFRP

30

ACI 440.1R-06

AFRP

30

CFRP

55

GFRP

20

ISIS EC Module 8

slide64

Composites

FRP

For Construction

Specifications: Durability of FRP Bars

Section: 10

  • ISIS Canada has recently published a product certification document:
    • Specifications for Product Certification of Fibre Reinforced Polymers (2006)
  • Test methods are given for quantitatively defining the durability of FRP reinforcing bars for concrete
  • Classifies FRP bars into different durability “categories” (e.g. D1, D2, etc.)

ISIS EC Module 8

slide65

Composites

FRP

For Construction

Specifications: Durability Criteria

Section: 10

ISIS EC Module 8

slide66

Composites

FRP

For Construction

Case Study:Field Evaluation of GFRP

Section: 11

  • Laboratory experiments have suggested that FRPs may be susceptible to deterioration under many environmental conditions
    • Field data are scant for FRPs used in infrastructure applications
  • Available field data indicate that in-service performance can be much better than assumed on the basis of laboratory testing

ISIS EC Module 8

slide67

Composites

FRP

For Construction

Case Study:Field Evaluation of GFRP

Section: 11

  • ISIS Canada Research project to study in-service performance of glass FRP reinforcing bars in concrete structures in Canada:
    • Joffre Bridge (Sherbrooke, Quebec)
    • Crowchild Bridge (Calgary, Alberta)
    • Hall’s Harbour Wharf (Hall’s Harbour, Nova Scotia)
    • Waterloo Creek Bridge (British Columbia)
    • Chatham Bridge (Ontario)
  • Samples studied for evidence of deterioration using various optical and chemical techniques

ISIS EC Module 8

slide68

Composites

FRP

For Construction

Case Study:Field Evaluation of GFRP

Section: 11

There are many methods to investigate durability performance of GFRP reinforcing bars:

  • Optical Microscopy (OM)
  • Scanning Electron Microscopy (SEM)
  • Energy Dispersive X-ray Analysis (EDX)
  • Infrared Spectroscopy (IS)
  • Differential Scanning Calorimetry (DSC)

ISIS EC Module 8

slide69

Composites

FRP

For Construction

Interface

Interface

Field Evaluation of GFRP

Section: 11

Case study

Optical Microscopy (OM):

  • To visually examine the interface between the GFRP reinforcing bars and the concrete

After 8 years of exposure to alkalinity, freeze-thaw, wet-dry, and chlorides

Chatham Bridge

Crowchild Trail Bridge

No evidence of damage or deterioration

ISIS EC Module 8

slide70

Composites

FRP

For Construction

Field Evaluation of GFRP

Section: 11

Case study

Scanning Electron Microscopy (SEM):

  • To conduct highly detailed visual examination of GFRP

After 8 years of exposure to alkalinity, freeze-thaw, wet-dry, and chlorides

Chatham Bridge

Crowchild Trail Bridge

No evidence of damage or deterioration

ISIS EC Module 8

slide71

Composites

FRP

For Construction

Field Evaluation of GFRP

Section: 11

Case study

Energy Dispersive X-ray Analysis (EDX):

  • To determine if any chemical changes had occurred in glass fibres or in polymer matrix

After 8 years of exposure to alkalinity, freeze-thaw, wet-dry, and chlorides

No Sodium or Potassium are present

ISIS EC Module 8

slide72

Composites

FRP

For Construction

Field Evaluation of GFRP

Section: 11

Case study

Other techniques…

  • Infrared Spectroscopy (IS):
    • to determine the extent of alkali-induced hydrolysis of the matrix
    • No evidence of damage or deterioration
  • Differential Scanning Calorimetry (DSC):
    • to determine the glass transition temperature of a polymer material
    • No evidence of damage or deterioration

ISIS EC Module 8

slide73

Design with

FRP

reinforcement

Durability Research Needs

The durability performance of FRP materials is generally very good in comparison with other, more conventional, construction materials

However, it should be equally clear that the long-term durability of FRPs remains incompletely understood

A large research effort is thus required to fill all of the gaps in knowledge

ISIS EC Module 8

slide74

Design with

FRP

reinforcement

Durability Research Needs

  • Moisture:
    • Effects of under-cure and/or incomplete cure of the polymer matrix
    • Effects of continuous versus intermittent exposure to moisture when bonded to concrete
  • Alkalinity:
    • Determination of rational and defensible standard alkaline solutions and alkalinity testing protocols and database of durability information
    • Development of an understanding of alkali-induced deterioration mechanisms
    • The potential synergistic effects of combined alkalinity, stress, moisture, and temperature are not well understood, particularly as they relate to creep-rupture of FRP components.

ISIS EC Module 8

slide75

Design with

FRP

reinforcement

Durability Research Needs

  • Fire:
    • Non-destructive evaluation methods for fire-exposed composites
    • Fire repair strategies
    • Development of relationships between tests on small scale material samples at high temperature and full-scale structural performance during fire
  • Fatigue:
    • More fatigue data on a variety of FRP materials
    • Mechanistic understanding of fatigue in composites in conjunction with various environmental factors
    • Development of a rational and defensible short term representative exposure to evaluate long-term fatigue performance

ISIS EC Module 8

slide76

Design with

FRP

reinforcement

Durability Research Needs

  • Synergies:
    • Potentially important synergies between most of the durability factors considered in this module remain incompletely understood
    • Research needed to elucidate the interrelationships between moisture, alkalinity, temperature, stress, and chemical exposures

ISIS EC Module 8

slide77

Design with

FRP

reinforcement

Additional Information

Additional information on all of the topics discussed in this module is available from:

www.isiscanada.com

ISIS EC Module 8