Transcript Document

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
• 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
Composites
Outline
FRP
For Construction
Introduction & Overview
Case Study
Moisture & Marine
Exposures
Alkalinity &
Corrosion
Specifications
Reduction
Factors
Fatigue
Creep
High Temperatures
& Fire
Cold Temperatures &
Freeze-Thaw
UV Radiation
ISIS EC Module 8
Composites
FRP
For Construction
Introduction & Overview
• 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
Section: 1
Composites
FRP
For Construction
Introduction & Overview
• Key uses of FRPs in construction:
1. Internal reinforcement of concrete
Corrosion of steel reinforcement in concrete
structures contributes to infrastructure deterioration
Use non-corrosive FRP reinforcement
2. External strengthening of concrete
Provide external tension or confining reinforcement
(FRP plates, sheets, bars, etc.)
ISIS EC Module 8
Section: 1
Composites
FRP
For Construction
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.)
High-strength fibres
 FRPs consist of:
1. Fibres
2. Matrix
Polymer matrix
ISIS EC Module 8
Composites
FRP
For Construction
Introduction & Overview
Section: 1
Polymer matrix
• Polymer matrix:
As the binder for the FRP, the matrix roles include:
1.
2.
3.
4.
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
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
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
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)
• Selected based on:




Required strength and stiffness
Durability considerations
Cost constraints
Availability of materials
ISIS EC Module 8
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
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
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
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
Composites
FRP
For Construction
FRP vs. Steel
Section: 1
Mechanical Properties
2500
Stress [MPa]
• FRP properties
(in general versus steel):
• Linear elastic behaviour
to failure
• No yielding
• Higher ultimate strength
• Lower strain at failure
• Comparable modulus
(carbon FRP)
ISIS EC Module 8
2000
1500
CFRP
GFRP
1000
Steel
500
1
2
Strain [%]
3
Composites
FRP
Quantitative Comparison
For Construction
Section: 1
Typical Mechanical Properties*
Material
Ultimate Strength
Elastic Modulus
Failure Strain
Glass FRP
517-1207 MPa
30-55 GPa
2-4.5 %
Carbon FRP
1200-2410 MPa
147-165 GPa
1-1.5 %
Aramid FRP
1200-2068 MPa
50-74 GPa
2-2.6 %
Steel
483-690 MPa
200 GPa
>10 %
* Based on 2001 data for specific FRP rebar products
ISIS EC Module 8
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
Composites
FRP
For Construction
Introduction & Overview
Section: 1
Examples of FRP
Unidirectional
glass FRP bar
Glass FRP
grid
Carbon FRP
prestressing
tendon
Glass fibre
roving
Carbon fibre
roving
ISIS EC Module 8
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
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
Composites
FRP
For Construction
CAUTION!
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
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
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
Composites
FRP
For Construction
Introduction & Overview
Section: 1
Durability
• Potentially harmful effects for FRP:
Environmental Effects
Physical Effects
Moisture & Marine Environments
Alkalinity& Corrosion
Heat & Fire
Cold & Freeze-Thaw Cycling
DURABILITY
OF FRPs
Ultraviolet Radiation
POTENTIAL
SYNERGIES
ISIS EC Module 8
Sustained Load:
Creep
Cyclic loading:
Fatigue
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
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
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
Composites
FRP
For Construction
Moisture & Marine Exposures
• Overall effects of moisture absorption:
Moisture absorption
•
•
•
•
Section: 2
Moisture
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
Composites
Moisture & Marine Exposures
FRP
For Construction
Section: 2
Moisture
• Typical moisture absorption trend for a matrix
polymer:
% Mass Gain
< 1%
0
1
Time (years)
ISIS EC Module 8
2
Composites
FRP
For Construction
Moisture & Marine Exposures
Section: 2
Moisture
% Strength Retention
• Strength loss trend of typical FRPs due to
moisture absorption:
Note: no strength reductions in
some lab studies
100 %
0
5
Time (years)
10
ISIS EC Module 8
Further
research
needed
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
Composites
FRP
For Construction
Moisture & Marine Exposures
Section: 2
• The effect of moisture on fibres’ performance:
Glass fibres:
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
Composites
FRP
For Construction
Moisture & Marine Exposures
• FRPs can be protected against moisture
absorption by appropriate selection of matrix
materials and protective coatings:
Section: 2
Resins
• 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
Composites
FRP
For Construction
Alkalinity & Corrosion
• Effects of alkalinity on FRPs’ performance:
Section: 3
Alkalinity
 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
Damage to glass
fibres depends on
GFRP bar
ISIS EC Module 8
• Protection by matrix
• Level of applied stress
• Temperature
Composites
FRP
For Construction
Alkalinity & Corrosion
Section: 3
Alkalinity
• Degradation mechanisms for GFRP reinforcement:
Alkaline
solutions
Alkaline solutions
cause embrittlement
of the fibres
GFRP bar
ISIS EC Module 8
• Reduction in tensile
properties
• Damage at the
fibre-resin interface
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
 Carbon fibres
• Strength reduction of 0 – 20 % of initial values
ISIS EC Module 8
Need
further
research
Composites
FRP
For Construction
Alkalinity & Corrosion
• Galvanic Corrosion:
Section: 3
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
Composites
FRP
For Construction
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
Steel bar
 External strengthening:
apply a thin layer of epoxy or
GFRP sheet between CFRP
and steel
Spacer
CFRP bar
Steel girder
GFRP sheet
ISIS EC Module 8
CFRP sheet
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
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
Composites
FRP
For Construction
High Temperatures & Fire
Section: 4
• Potential problems of FRPs under fire:
Internal FRP reinforcement
External FRP strengthening
Sudden and
severe loss of
bond at T > Tg
ISIS EC Module 8
Too thin for selfinsulating layer,
loss of bond at
T > Tg
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 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
ISIS EC Module 8
Composites
FRP
For Construction
High Temperatures & Fire
• 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
Section: 4
Composites
FRP
For Construction
High Temperatures & Fire
Section: 4
Critical
temperature
(T > Tg)
% of Room Temperature Value
• Deterioration of mechanical and bond properties
for GFRP bars:
Elastic Modulus
Tensile Strength
Ave. Bond Strength
100
80
60
40
20
0
0
100 200 300 400 500 600
Temperature (deg. C)
ISIS EC Module 8
Composites
FRP
For Construction
High Temperatures & Fire
• 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
Section: 4
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:
1. Changes that occur in the behaviour of the component materials at
low temperatures
2. 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
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
Matrix micro-cracking and
fibre-matrix bond degradation
May affect FRPs’
ISIS EC Module 8
•
•
•
•
•
•
Stiffness
Strength
Dimensional stability
Fatigue resistance
Moisture absorption
Resistance to alkalinity
Composites
FRP
For Construction
Cold Temperatures
• Increasing # of
freeze/thaw cycles
Section: 5
• Increased severity of matrix
cracks
• Increased matrix brittleness
• Decreased tensile strength
HOWEVER
The effects on FRP properties appear
to be minor in most infrastructure
applications
ISIS EC Module 8
Composites
FRP
For Construction
Ultraviolet Radiation
Section: 6
• Ultraviolet (UV) radiation damages most
polymer matrices
• The effects of UV on:
• Aramid fibres: significant
• Glass fibres: insignificant
• Carbon fibres: insignificant
• Thus, potential for UV degradation is important
when FRPs are exposed to direct sunlight
ISIS EC Module 8
Composites
FRP
Ultraviolet Radiation
For Construction
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
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
Composites
FRP
Creep & Creep Rupture
For Construction
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 P
Steel
Steel
P
P=P
P=P
L = L1
L > L1
with creep
ideal
ISIS EC Module 8
Composites
FRP
Creep & Creep Rupture
For Construction
Section: 7
• Relaxation: a reduction in stress in a material with
time at a constant level of strain (P = final load)
L1
L1
P
P
Steel
P1
P1
Steel
P=P
P > P1
L = L1
L = L1
ideal
with relaxation
ISIS EC Module 8
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
Composites
FRP
For Construction
Creep & Creep Rupture
Section: 7
• For good performance under sustained loads:
Creep
 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
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
Composites
FRP
For Construction
Creep & Creep Rupture
Section: 7
• Endurance time: the time to creep rupture of FRPs
under a given level of sustained load
Sustained stress
Endurance time
Ultimate strength
• Other factors influencing endurance time include:
•
•
•
•
•
Elevated temperature
Alkalinity
Moisture
Freeze-thaw cycling
UV exposure
Endurance time
ISIS EC Module 8
Composites
FRP
For Construction
Creep & Creep Rupture
• 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 necessarily
representative of field performance
ISIS EC Module 8
Section: 7
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
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
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 factors remain 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
Composites
FRP
For Construction
Reduction Factors (FRP bars)
Section: 9
• For non-prestressed FRPs
Document
CHBDC, 2006
CSA S806-02
Material
Exposure Condition
Reduction
Factor
AFRP
All
0.60
CFRP
All
0.75
GFRP
All
0.50
All
All
0.75
Not exposed to earth and weather
0.90
Exposed to earth and weather
0.80
Not exposed to earth and weather
1.00
Exposed to earth and weather
0.90
Not exposed to earth and weather
0.80
Exposed to earth and weather
0.70
AFRP
ACI 440.1R06
CFRP
GFRP
ISIS EC Module 8
Composites
FRP
For Construction
Reduction Factors
Section: 9
• Sustained (service) stress levels are limited to avoid
creep rupture and other forms of distress:
Document
CHBDC, 2006
CSA S806-02
ACI 440.1R-06
FRP Bars
Stress limit
(% of ultimate)
AFRP
35
CFRP
65
GFRP
25
GFRP
30
AFRP
30
CFRP
55
GFRP
20
ISIS EC Module 8
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
Composites
FRP
For Construction
Specifications: Durability Criteria
Section: 10
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)
ISIS EC Module 8
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
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
Composites
FRP
Case Study: Field Evaluation of GFRP
For Construction
• 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
Section: 11
Composites
FRP
Field Evaluation of GFRP
For Construction
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
Interface
Interface
Chatham Bridge
Crowchild Trail Bridge
No evidence of damage or deterioration
ISIS EC Module 8
Composites
FRP
For Construction
Field Evaluation of GFRP
• Scanning Electron Microscopy (SEM):
Section: 11
Case study
 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
Composites
FRP
For Construction
Field Evaluation of GFRP
• Energy Dispersive X-ray Analysis (EDX):
Section: 11
Case study
 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
Composites
FRP
For Construction
Field Evaluation of GFRP
• 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
Section: 11
Case study
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
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
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
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
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