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

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Presentation on theme: "Durability of FRP Composites for Construction ISIS Educational Module 8: Produced by ISIS Canada."— Presentation transcript:

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

2 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 FRP Composites For Construction

3 Outline Introduction & Overview Moisture & Marine Exposures Cold Temperatures & Freeze-Thaw UV Radiation Creep Fatigue ISIS EC Module 8 FRP Composites For Construction Alkalinity & Corrosion High Temperatures & Fire Reduction Factors Case Study Specifications

4 Section:1 Introduction & Overview ISIS EC Module 8 FRP Composites 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 )

5 Section:1 ISIS EC Module 8 FRP Composites 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.)

6 Section:1 ISIS EC Module 8 FRP Composites 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.Fibres 2.Matrix High-strength fibres Polymer matrix

7 Section:1 ISIS EC Module 8 FRP Composites For Construction Polymer matrix Introduction & Overview Polymer matrix: As the binder for the FRP, the matrix roles include: 1.Binding the fibres together 2.Protecting the fibres from environmental degradation 3.Transferring force between the individual fibres 4.Providing shape to the FRP component

8 Section:1 ISIS EC Module 8 FRP Composites For Construction Polymer matrix Introduction & Overview 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

9 Section:1 ISIS EC Module 8 FRP Composites For Construction Fibres Introduction & Overview 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:

10 Section:1 ISIS EC Module 8 FRP Composites For Construction Fibres Introduction & Overview 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:

11 Section:1 ISIS EC Module 8 FRP Composites For Construction Fibres Introduction & Overview 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

12 Section:1 ISIS EC Module 8 FRP Composites For Construction Fibres Introduction & Overview Carbon fibres: Significantly higher cost than glass High strength, high modulus, low density E = GPa: standard E = GPa: intermediate E = GPa: high E = GPa: ultra-high Superior durability and fatigue characteristics Used in weight/modulus critical applications

13 Section:1 ISIS EC Module 8 FRP Composites For Construction Fibres Introduction & Overview 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

14 Mechanical Properties FRP Composites 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

15 Strain [%] Stress [MPa] FRP vs. Steel 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) Steel CFRP FRP Composites For Construction GFRP Section:1 ISIS EC Module 8

16 Quantitative Comparison FRP Composites For Construction Typical Mechanical Properties* Ultimate Strength MPa MPa MPa MPa Elastic Modulus GPa GPa GPa 200 GPa Material Glass FRP Carbon FRP Aramid FRP Steel Failure Strain % % % >10 % * Based on 2001 data for specific FRP rebar products Section:1 ISIS EC Module 8

17 Section:1 Physical, mechanical, durability properties of FRPs ISIS EC Module 8 FRP Composites 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 Introduction & Overview

18 ISIS EC Module 8 Examples of FRP Glass fibre roving Carbon fibre roving Unidirectional glass FRP bar Carbon FRP prestressing tendon Glass FRP grid FRP Composites For Construction Section:1 Introduction & Overview

19 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 FRPs FRP Composites For Construction Section:1 Introduction & Overview

20 Section:1 What is durability? ISIS EC Module 8 FRP Composites 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 Introduction & Overview

21 Section:1 CAUTION! ISIS EC Module 8 FRP Composites For Construction 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

22 Section:1 Environments ISIS EC Module 8 FRP Composites 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 Introduction & Overview

23 Section:1 ISIS EC Module 8 FRP Composites For Construction 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) Durability Introduction & Overview

24 Section:1 ISIS EC Module 8 FRP Composites For Construction Potentially harmful effects for FRP: Durability Introduction & Overview Environmental Effects Physical Effects Moisture & Marine Environments Alkalinity& Corrosion Heat & Fire Cold & Freeze-Thaw Cycling Sustained Load: Creep Cyclic loading: Fatigue Ultraviolet Radiation POTENTIAL SYNERGIES DURABILITY OF FRPs

25 Section:2 Moisture & Marine Exposures ISIS EC Module 8 FRP Composites For Construction 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

26 Section:2 ISIS EC Module 8 FRP Composites For Construction 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 Moisture & Marine Exposures Moisture

27 Section:2 ISIS EC Module 8 FRP Composites 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 Moisture & Marine Exposures Moisture

28 Section:2 ISIS EC Module 8 FRP Composites For Construction Overall effects of moisture absorption: Moisture & Marine Exposures 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 Moisture

29 Section:2 ISIS EC Module 8 FRP Composites For Construction Typical moisture absorption trend for a matrix polymer: Moisture & Marine Exposures Moisture Time (years) 120 < 1% % Mass Gain

30 Section:2 ISIS EC Module 8 FRP Composites For Construction Strength loss trend of typical FRPs due to moisture absorption: Moisture & Marine Exposures Moisture % % Strength Retention Time (years) Note: no strength reductions in some lab studies Further research needed

31 Section:2 ISIS EC Module 8 FRP Composites For Construction Potentially Important degradation synergies: Moisture & Marine Exposures Moisture absorption Sustained stress Elevated temperatures Stress-induced micro-cracking of the polymer matrix Moisture-induced micro-cracking of polymer matrix in a GFRP

32 Section:2 ISIS EC Module 8 FRP Composites For Construction The effect of moisture on fibres performance: Moisture & Marine Exposures 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

33 Section:2 ISIS EC Module 8 FRP Composites For Construction FRPs can be protected against moisture absorption by appropriate selection of matrix materials and protective coatings: Moisture & Marine Exposures 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

34 Section:3 ISIS EC Module 8 FRP Composites For Construction Effects of alkalinity on FRPs performance: Alkalinity & Corrosion 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

35 Section:3 ISIS EC Module 8 FRP Composites For Construction Degradation mechanisms for GFRP reinforcement: Alkalinity & Corrosion GFRP bar Alkaline solutions Alkaline solutions cause embrittlement of the fibres Reduction in tensile properties Damage at the fibre-resin interface Alkalinity

36 Section:3 ISIS EC Module 8 FRP Composites 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 Alkalinity & Corrosion E-glass fibres Strength reduction of 0 – 75 % of initial values Need further research

37 Section:3 ISIS EC Module 8 FRP Composites For Construction Galvanic Corrosion: Corrosion Alkalinity & 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

38 Section:3 ISIS EC Module 8 FRP Composites For Construction CFRPs should not be permitted to come in to direct contact with steel or aluminum in structures Corrosion Alkalinity & 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 bar Spacer Steel girder GFRP sheet CFRP sheet

39 Section:4 ISIS EC Module 8 FRP Composites For Construction 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 High Temperatures & Fire

40 Section:4 ISIS EC Module 8 FRP Composites For Construction FRPs used in infrastructure applications suffer degradation of mechanical and/or bond properties at temperatures exceeding their glass transition temperature High Temperatures & Fire Glass transition temperature, T g 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 ) All organic polymer materials combust at high temperatures Most matrix polymers release large quantities of dense, black, toxic smoke

41 Section:4 ISIS EC Module 8 FRP Composites For Construction Potential problems of FRPs under fire: High Temperatures & Fire Internal FRP reinforcement Sudden and severe loss of bond at T > T g External FRP strengthening Too thin for self- insulating layer, loss of bond at T > T g

42 Section:4 ISIS EC Module 8 FRP Composites For Construction Mechanical properties of FRPs deteriorate with increasing temperature Critical temperature commonly taken to be T g for the polymer matrix Typically in the range of ºC Exceeding T g results in severe degradation of matrix dominated properties such as transverse and shear strength and stiffness Longitudinal properties also affected above T g Tensile strength reductions as high as 80% can be expected in the fibre direction at temperatures of only 300ºC I mportant that an FRP component not be exposed to temperatures close to or above T g during the normal range of operating temperatures High Temperatures & Fire

43 Section:4 ISIS EC Module 8 FRP Composites For Construction Degradation of mechanical properties is mainly governed by the properties of the matrix: Carbon fibres High Temperatures & Fire 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

44 Section:4 ISIS EC Module 8 FRP Composites For Construction Deterioration of mechanical and bond properties for GFRP bars: High Temperatures & Fire Critical temperature ( T > T g )

45 Section:4 ISIS EC Module 8 FRP Composites 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 High Temperatures & Fire

46 Section:5 ISIS EC Module 8 FRP Composites 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 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 Cold Temperatures

47 Section:5 ISIS EC Module 8 FRP Composites 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

48 Section:5 ISIS EC Module 8 FRP Composites 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

49 Section:6 ISIS EC Module 8 FRP Composites For Construction Ultraviolet (UV) radiation damages most polymer matrices Ultraviolet Radiation 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

50 Section:6 ISIS EC Module 8 FRP Composites For Construction Photodegradation: UV radiation within a certain range of specific wavelengths breaks chemical bonds between polymer chains and resulting in: Ultraviolet Radiation 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

51 Section:6 ISIS EC Module 8 FRP Composites For Construction Combined effects of UV and moisture on FRP bars: Ultraviolet Radiation 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 %

52 Section:7 ISIS EC Module 8 FRP Composites 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 P P Steel P = P L = L 1 L1L1 with creep P P Steel P = P L > L 1 L1L1

53 Section:7 ISIS EC Module 8 FRP Composites For Construction Relaxation : a reduction in stress in a material with time at a constant level of strain (P = final load) Creep & Creep Rupture ideal Steel P = P L = L 1 L1L1 with relaxation Steel P > P 1 L = L 1 L1L1 P P P P 1 1

54 Section:7 ISIS EC Module 8 FRP Composites 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 Rupture Creep

55 Section:7 ISIS EC Module 8 FRP Composites For Construction 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 Creep & Creep Rupture Creep

56 Section:7 ISIS EC Module 8 FRP Composites 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) Creep & Creep Rupture Called Stress Rupture, Creep Rupture, or Stress Corrosion Creep Rupture

57 Section:7 ISIS EC Module 8 FRP Composites For Construction Endurance time : the time to creep rupture of FRPs under a given level of sustained load Creep & Creep Rupture Sustained stress Ultimate strength Endurance time Other factors influencing endurance time include: Elevated temperature Alkalinity Moisture Freeze-thaw cycling UV exposure Endurance time

58 Section:7 ISIS EC Module 8 FRP Composites For Construction Creep rupture stress limits for FRP reinforcing bars (50 years creep rupture strength) : Creep & Creep Rupture GFRP : % of initial tensile strength AFRP : % of initial tensile strength CFRP : % of initial tensile strength Note : Laboratory testing is not necessarily representative of field performance

59 Section:8 ISIS EC Module 8 FRP Composites 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

60 Section:8 ISIS EC Module 8 FRP Composites For Construction Good fatigue performance of FRPs depends on: Toughness of the matrix Ability to resist cracking CFRP : best GFRP : good AFRP : excellent Performance of FRPs under fatigue load: Fatigue NOTE: Fatigue performance of FRP reinforced concrete appears to be best when GFRP reinforcement is used

61 Section:9 ISIS EC Module 8 FRP Composites 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 FRPs limit the useable ranges of stress and strain in engineering design Reduction Factors

62 Section:9 ISIS EC Module 8 FRP Composites For Construction For non-prestressed FRPs Reduction Factors (FRP bars) 0.70 Exposed to earth and weather 0.80 Not exposed to earth and weather GFRP 0.90 Exposed to earth and weather 1.00 Not exposed to earth and weather CFRP 0.80 Exposed to earth and weather 0.90 Not exposed to earth and weather AFRP ACI 440.1R All CSA S AllGFRP 0.75AllCFRP 0.60AllAFRP CHBDC, 2006 Reduction Factor Exposure ConditionMaterialDocument

63 Section:9 ISIS EC Module 8 FRP Composites 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 S GFRP 65CFRP 35AFRP CHBDC, 2006 Stress limit (% of ultimate) FRP BarsDocument

64 Section: 10 ISIS EC Module 8 FRP Composites 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

65 Section: 10 ISIS EC Module 8 FRP Composites For Construction Specifications: Durability Criteria PropertySpecified 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 strengthCreep rupture strength: 35% UTS (Glass) 75% UTS (Carbon) 45% UTS (Aramid) CreepReport creep strain values at 1000 hr, 3000 hr and hr Fatigue strengthFatigue strength at 2 million cycles: 35% UTS (Glass) 75% UTS (Carbon) 45% UTS (Aramid)

66 Section: 11 ISIS EC Module 8 FRP Composites 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

67 ISIS EC Module 8 FRP Composites 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) Halls Harbour Wharf (Halls 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 GFRP Section: 11

68 ISIS EC Module 8 FRP Composites 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

69 ISIS EC Module 8 FRP Composites For Construction Optical Microscopy (OM): Field Evaluation of GFRP Case 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

70 ISIS EC Module 8 FRP Composites For Construction Scanning Electron Microscopy (SEM): Field Evaluation of GFRP Case study To conduct highly detailed visual examination of GFRP Crowchild Trail Bridge Chatham Bridge After 8 years of exposure to alkalinity, freeze-thaw, wet-dry, and chlorides No evidence of damage or deterioration Section: 11

71 ISIS EC Module 8 FRP Composites For Construction Energy Dispersive X-ray Analysis (EDX): Field Evaluation of GFRP 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 Section: 11

72 ISIS EC Module 8 FRP Composites For Construction Other techniques… Field Evaluation of GFRP Case study 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

73 Durability Research Needs ISIS EC Module 8 FRP Design 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

74 Durability Research Needs ISIS EC Module 8 FRP Design with reinforcement 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.

75 Durability Research Needs ISIS EC Module 8 FRP Design with reinforcement 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

76 Durability Research Needs ISIS EC Module 8 FRP Design 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

77 Additional Information ISIS EC Module 8 FRP Design with reinforcement Additional information on all of the topics discussed in this module is available from:


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