Durability of FRP Composites for Construction ISIS Educational Module 8: Produced by ISIS Canada.

Durability of FRP Composites for Construction

ISIS Educational Module 8:

Produced by ISIS Canada

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

FRPComposites

For Construction

Outline

Introduction & Overview

Moisture & Marine Exposures

Cold Temperatures & Freeze-Thaw

UV Radiation

CreepFatigue

ISIS EC Module 8

FRPComposites

For Construction

Alkalinity & Corrosion

High Temperatures & Fire

Reduction Factors

Case Study

Specifications

Section: 1 Introduction & Overview

ISIS EC Module 8

FRPComposites

For Construction

• 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)

Section: 1

ISIS EC Module 8

FRPComposites

For Construction Introduction & Overview

• Key uses of FRPs in construction:

1. Internal reinforcement of concrete

2. External strengthening of concrete

Corrosion of steel reinforcement in concrete structures contributes to infrastructure deterioration

Use non-corrosive FRP reinforcement

Provide external tension or confining reinforcement (FRP plates, sheets, bars, etc.)

Section: 1

ISIS EC Module 8

FRPComposites

For Construction Introduction & Overview

• 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:1. Fibres2. Matrix

High-strength fibres

Polymer matrix

Section: 1

ISIS EC Module 8

FRPComposites

For Construction

Polymer matrix


• Polymer matrix:

As the binder for the FRP, the matrix roles include:1. Binding the fibres together2. Protecting the fibres from environmental degradation3. Transferring force between the individual fibres4. Providing shape to the FRP component

Section: 1

ISIS EC Module 8

FRPComposites

For Construction

Polymer matrix


• Commonly used matrices:

Vinylester: fabrication for FRP reinforcing bars(superior durability characteristics when embedded in concrete)

Epoxy: strengthening using FRP sheets/plates(superior adhesion characteristics)

Internal reinforcing applications

External strengthening applications

Section: 1

ISIS EC Module 8

FRPComposites

For Construction

Fibres


• Fibres:

Provide strength and stiffness of FRPProtected against environmental degradation by the

polymer matrixOriented in specified directions to provide strength

along specific axes (FRP is weaker in the directions perpendicular to the fiber)

Selected to have:

Section: 1

ISIS EC Module 8

FRPComposites

For Construction

Fibres


• Three most common fibres in Civil Engineering applications:GlassCarbonAramid (not common in North America)

Required strength and stiffness Durability considerations Cost constraints Availability of materials

• Selected based on:

Section: 1

ISIS EC Module 8

FRPComposites

For Construction

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

Section: 1

ISIS EC Module 8

FRPComposites

For Construction

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

Section: 1

ISIS EC Module 8

FRPComposites

For Construction

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

Mechanical PropertiesFRPComposites

For Construction

FRP mechanical properties are a function of:

Type of fibre and matrix

Fibre volume content

Orientation of fibres

Here we are concerned mainly with unidirectional FRPs!

Section: 1

ISIS EC Module 8

Strain [%]

1 2 3

500

1000

1500

2000

2500

Stre

ss [M

Pa]

FRP vs. SteelMechanical 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)

Steel

CFRP

FRPComposites

For Construction

GFRP

Section: 1

ISIS EC Module 8

Quantitative ComparisonFRPComposites

For Construction

Typical Mechanical Properties*

Ultimate Strength

517-1207 MPa

1200-2410 MPa

1200-2068 MPa

483-690 MPa

Elastic Modulus

30-55 GPa

147-165 GPa

50-74 GPa

200 GPa

Material

Glass FRP

Carbon FRP

Aramid FRP

Steel

Failure Strain

2-4.5 %

1-1.5 %

2-2.6 %

>10 %

* Based on 2001 data for specific FRP rebar products

Section: 1

ISIS EC Module 8

Section: 1

• Physical, mechanical, durability properties of FRPs

ISIS EC Module 8

FRPComposites

For Construction

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

FRP


ISIS EC Module 8

Examples of FRP

Glass fibre roving

Carbon fibre roving

Unidirectional glass FRP bar

Carbon FRP prestressing

tendon

Glass FRP grid

FRPComposites

For Construction Section: 1Introduction & Overview

• In the design and use of FRP materialsThe 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

FRPs

FRPComposites

For Construction Section: 1Introduction & Overview

Section: 1

• What is durability?

ISIS EC Module 8

FRPComposites

For Construction

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”


Section: 1 CAUTION!

ISIS EC Module 8

FRPComposites

For Construction

Data on the durability of FRP materials is limitedAppears contradictory in some casesDue 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

Section: 1

• Environments

ISIS EC Module 8

FRPComposites

For Construction

Durability

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


Section: 1

ISIS EC Module 8

FRPComposites

For Construction

• Factors affecting FRPs’ durability performance:

The matrix and fibre typesThe relative portions of the constituentsThe manufacturing processesThe installation proceduresThe short- and long-term loading and exposure

condition (physical and chemical)

Durability


Section: 1

ISIS EC Module 8

FRPComposites

For Construction

• Potentially harmful effects for FRP:Durability


Environmental Effects

Physical EffectsMoisture & Marine Environments

Alkalinity& Corrosion

Heat & Fire

Cold & Freeze-Thaw Cycling

Sustained Load:

Creep

Cyclic loading:

Fatigue

Ultraviolet Radiation

POTENTIAL SYNERGIES

DURABILITY

OF FRPs

Section: 2 Moisture & Marine Exposures

ISIS EC Module 8

FRPComposites

For Construction

• FRPs are particularly attractive for concrete structures in moist or marine environmentsFRPs are not susceptible to electrochemical corrosionCorrosion of steel in conventional structures results in severe

degradation

HOWEVER• FRPs are not immune to the potentially harmful

effects of moist or marine environments

Section: 2

ISIS EC Module 8

FRPComposites

For Construction

• Some FRP materials have been observed to deteriorate under prolonged exposure to moist environmentsEvidence linking the rate of degradation to the rate of sorption of fluid

into the polymer matrix

• All polymers will absorb moistureDepending 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

Moisture & Marine ExposuresMoisture

Section: 2

ISIS EC Module 8

FRPComposites

For Construction

• 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


Section: 2

ISIS EC Module 8

FRPComposites

For Construction

• Overall effects of moisture absorption:


Moisture absorptionPlasticization 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

Moisture

Section: 2

ISIS EC Module 8

FRPComposites

For Construction

• Typical moisture absorption trend for a matrix polymer:


Time (years)

1 20

< 1%

% M

ass

Gai

n

Section: 2

ISIS EC Module 8

FRPComposites

For Construction

• Strength loss trend of typical FRPs due to moisture absorption:


5 100

100 %

% S

tre

ng

th R

ete

nti

on

Time (years)

Note: no strength reductions in some lab studies

Further research needed

Section: 2

ISIS EC Module 8

FRPComposites

For Construction

• 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

Section: 2

ISIS EC Module 8

FRPComposites

For Construction

• 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

Fibres

Section: 2

ISIS EC Module 8

FRPComposites

For Construction

• 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

Resins

Section: 3

ISIS EC Module 8

FRPComposites

For Construction

• 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)

pH > 11

GFRP bar

• Protection by matrix• Level of applied stress• Temperature

Damage to glass fibres depends on

Alkalinity

Section: 3

ISIS EC Module 8

FRPComposites

For Construction

• Degradation mechanisms for GFRP reinforcement:


GFRP bar

Alkaline solutions

Alkaline solutions cause embrittlement of the fibres

• Reduction in tensile properties

• Damage at the fibre-resin interface

Alkalinity

Section: 3

ISIS EC Module 8

FRPComposites

For Construction

• The effect of alkaline environments on fibres:

AR-glass fibres• Significant improvement in alkaline environments, but $$$

Aramid fibres• Strength reduction of 10 – 50 % of initial values

Carbon fibres• Strength reduction of 0 – 20 % of initial values

Alkalinity


E-glass fibres• Strength reduction of 0 – 75 % of initial values

Need further research

Section: 3

ISIS EC Module 8

FRPComposites

For Construction

• Galvanic Corrosion:Corrosion


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

FRPs are not susceptible to electrochemical corrosion• Certain FRPs (e.g., CFRPs) can contribute to increased

corrosion of metal components through galvanic corrosion

Section: 3

ISIS EC Module 8

FRPComposites

For Construction

CFRPs should not be permitted to come in to direct contact with steel or aluminum in structures

Corrosion


• Guarding against galvanic corrosion:

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

Steel bar CFRP barSpacer

Steel girder

GFRP sheet CFRP sheet

Section: 4

ISIS EC Module 8

FRPComposites

For Construction

• FRP materials are now widely used for reinforcement and rehabilitation of bridges and other outdoor structuresFRPs have seen comparatively little use in building applications

• FRP materials are susceptible to elevated temperaturesSeveral 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


Section: 4

ISIS EC Module 8

FRPComposites

For Construction

• 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

Section: 4

ISIS EC Module 8

FRPComposites

For Construction

• Potential problems of FRPs under fire:


Internal FRP reinforcement

Sudden and severe loss of bond at T > Tg

External FRP strengthening

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

Section: 4

ISIS EC Module 8

FRPComposites

For Construction

• 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 Tg results 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


Section: 4

ISIS EC Module 8

FRPComposites

For Construction

• 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 fibres20-60% reduction in strength at 600 ºC

• Aramid fibres20-60% reduction in strength at 300 ºC

Section: 4

ISIS EC Module 8

FRPComposites

For Construction

• Deterioration of mechanical and bond properties for GFRP bars:


0

20

40

60

80

100

0 100 200 300 400 500 600

Temperature (deg. C)

% o

f R

oo

m T

em

pe

ratu

re V

alu

e

Elastic Modulus

Tensile Strength

Ave. Bond Strength

Critical temperature (T > Tg)

Section: 4

ISIS EC Module 8

FRPComposites

For Construction

• 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


Section: 5

ISIS EC Module 8

FRPComposites

For Construction

• 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:1. Changes that occur in the behaviour of the component materials at

low temperatures2. 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

Cold Temperatures

Section: 5

ISIS EC Module 8

FRPComposites

For Construction

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

Cold Temperatures

Matrix micro-cracking and fibre-matrix bond degradation

May affect FRPs’

• Stiffness• Strength• Dimensional stability• Fatigue resistance• Moisture absorption• Resistance to alkalinity

Section: 5

ISIS EC Module 8

FRPComposites

For Construction

• Increasing # of freeze/thaw cycles

Cold Temperatures

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

applications

HOWEVER

• Increased severity of matrix cracks

• Increased matrix brittleness• Decreased tensile strength

Section: 6

ISIS EC Module 8

FRPComposites

For Construction

• Ultraviolet (UV) radiation damages most polymer matrices


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

• The effects of UV on:• Aramid fibres: significant• Glass fibres: insignificant• Carbon fibres: insignificant

Section: 6

ISIS EC Module 8

FRPComposites

For Construction

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


• UV-induced surface flaws can cause: Stress concentrations → may lead to premature failure

Increased susceptibility to damage from alkalinity & moisture

Discoloration Surface oxidation Embrittlement Microcracking of the matrix

Section: 6

ISIS EC Module 8

FRPComposites

For Construction

• Combined effects of UV and moisture on FRP bars:


• Protection of FRPs from UV radiation: UV resistant paints

Coatings

Sacrificial surfaces

UV resistant polymer resins

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

Section: 7

ISIS EC Module 8

FRPComposites

For Construction

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

Creep & Creep Rupture

ideal

PP Steel

P = P

L = L1

L1

with creep

PP Steel

P = P

L > L1

L1

Section: 7

ISIS EC Module 8

FRPComposites

For Construction

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


ideal

Steel

P = P

L = L1

L1

with relaxation

Steel

P > P1

L = L1

L1

P P P P1 1

Section: 7

ISIS EC Module 8

FRPComposites

For Construction

• 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)

Creep & Creep RuptureCreep

Section: 7

ISIS EC Module 8

FRPComposites

For Construction

• For good performance under sustained loads:Use an appropriate matrix materialTake care during the fabrication and curing processes

• Creep behaviour of different FRP materials is complex and depends on: Specific constituents and fabricationType, direction, and level of loading appliedExposure to other durability factors such as alkalinity, moisture,

thermal exposures

• Few standard test methods for creep testing FRP materialsDifficult to make generalizations about FRPs’ creep performance

Creep & Creep RuptureCreep

Section: 7

ISIS EC Module 8

FRPComposites

For Construction

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

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


Called Stress Rupture, Creep Rupture, or Stress Corrosion

Creep Rupture

Section: 7

ISIS EC Module 8

FRPComposites

For Construction

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


Sustained stress

Ultimate strengthEndurance time

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

Endurance time

Section: 7

ISIS EC Module 8

FRPComposites

For Construction

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


GFRP: 29-55 % of initial tensile strengthAFRP: 47-66 % of initial tensile strengthCFRP: 79-93 % of initial tensile strength

Note: Laboratory testing is not necessarily representative of field performance

Section: 8

ISIS EC Module 8

FRPComposites

For Construction

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

Fatigue

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

Section: 8

ISIS EC Module 8

FRPComposites

For Construction

• Good fatigue performance of FRPs depends on:

Toughness of the matrixAbility to resist cracking

CFRP: bestGFRP: goodAFRP: excellent

• Performance of FRPs under fatigue load:

Fatigue

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

Section: 9

ISIS EC Module 8

FRPComposites

For Construction

• Numerous factors exist that can potentially affect the long term durability of FRP materials in civil engineering and construction applications

• Durability factors remain incompletely understood

• Reduction factors in existing design codes and recommendations:Applied to the nominal stress and strain capacities of FRPslimit the useable ranges of stress and strain in engineering

design

Reduction Factors

Section: 9

ISIS EC Module 8

FRPComposites

For Construction

• For non-prestressed FRPs

Reduction Factors (FRP bars)

0.70Exposed to earth and weather

0.80Not exposed to earth and weatherGFRP


1.00Not exposed to earth and weatherCFRP


0.90Not exposed to earth and weatherAFRP

ACI 440.1R-06

0.75AllAllCSA S806-02

0.50AllGFRP

0.75AllCFRP

0.60AllAFRP

CHBDC, 2006

Reduction Factor

Exposure ConditionMaterialDocument

Section: 9

ISIS EC Module 8

FRPComposites

For Construction

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

Reduction Factors

20GFRP

55CFRP

30AFRP

ACI 440.1R-06

30GFRPCSA S806-02

25GFRP

65CFRP

35AFRP

CHBDC, 2006

Stress limit (% of ultimate)

FRP BarsDocument

Section: 10

ISIS EC Module 8

FRPComposites

For Construction

• 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.)

Specifications: Durability of FRP Bars

Section: 10

ISIS EC Module 8

FRPComposites

For ConstructionSpecifications: Durability Criteria

Property Specified limits

Void content ≤ 1%

Water absorption ≤ 1% for D2 FRP bars and grids; ≤ 0.75% for D1 bars and grids

Cure ratio ≥ 95% for D2 bars and grids; ≥ 98% for D1 bars and grids

Glass transition temperature

DMA = 90°C, DSC = 80°C for D2 bars and grids; DMA = 110°C, DSC = 100°C for D1 bars and grids

Alkali resistance in high pH solution (no load)

Tensile capacity retention ≥70% for D2 bars and grids; tensile capacity retention ≥80% for D1 bars and grids

Alkali resistance in high pH solution (with load)

Tensile capacity retention ≥60% for D2 bars and grids; tensile capacity retention ≥70% for D1 bars and grids

Creep rupture strength Creep rupture strength:≥35% UTS (Glass)≥75% UTS (Carbon)≥45% UTS (Aramid)

Creep Report creep strain values at 1000 hr, 3000 hr and 10000 hr

Fatigue strength Fatigue strength at 2 million cycles:≥35% UTS (Glass)≥75% UTS (Carbon)≥45% UTS (Aramid)

Section: 11

ISIS EC Module 8

FRPComposites

For Construction

• 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

Case Study: Field Evaluation of GFRP

ISIS EC Module 8

FRPComposites

For Construction

• 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

Case Study: Field Evaluation of GFRPSection: 11

ISIS EC Module 8

FRPComposites

For Construction

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

Case Study: Field Evaluation of GFRP

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

Section: 11

ISIS EC Module 8

FRPComposites

For Construction

• Optical Microscopy (OM):

Field Evaluation of GFRPCase study

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

Interface

Crowchild Trail Bridge

Interface

Chatham Bridge

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

No evidence of damage or deterioration

Section: 11

ISIS EC Module 8

FRPComposites

For Construction

• Scanning Electron Microscopy (SEM):


To conduct highly detailed visual examination of GFRP

Crowchild Trail Bridge Chatham Bridge


No evidence of damage or deterioration

Section: 11

ISIS EC Module 8

FRPComposites

For Construction

• Energy Dispersive X-ray Analysis (EDX):


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


No Sodium or Potassium are present

Section: 11

ISIS EC Module 8

FRPComposites

For Construction

• 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

Section: 11

Durability Research Needs

ISIS EC Module 8

FRPDesign with

reinforcement

• 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

FRPDesign with

reinforcement

• Moisture:Effects of under-cure and/or incomplete cure of the polymer matrixEffects 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 informationDevelopment of an understanding of alkali-induced deterioration

mechanismsThe 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

FRPDesign with

reinforcement

• Fire:Non-destructive evaluation methods for fire-exposed compositesFire repair strategiesDevelopment 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 materialsMechanistic understanding of fatigue in composites in conjunction

with various environmental factorsDevelopment of a rational and defensible short term representative

exposure to evaluate long-term fatigue performance


ISIS EC Module 8

FRPDesign with

reinforcement

• 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

Additional Information

ISIS EC Module 8

FRPDesign with

reinforcement

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

www.isiscanada.com

Durability of FRP Composites for Construction ISIS Educational Module 8: Produced by ISIS Canada.

Documents

durability of frp composites

construction slide

stiffness of frp

frp component slide

stress mpa frp

specific axes frp

isis canada slide

construction gfrp section