CONCRETE REINFORCEMENT AND GLASS FIBRE REINFORCED POLYMER

Michael Kemp BEng Civil - General Manager Wagners CFT

David Blowes Sales Engineer - Wagners CFT

Abstract The corrosion of steel reinforcement in concrete reduces the life of stnlctures causes high repair costs and can endanger the structural integrity of the structure itself Glass fibre reinforced polymer (GFRP) offers a number of advantages over steel especially when used in marine and other salt laden environments GFRP reinforcing bars are gradually finding wider acceptance as a replacement for conventional steel reinforcement as it otTers a number of advantages

Technical studies on a number of concrete structures from five to e ight years old and constructed with GFRP reinforcement have shown that there is no degradation of the GFRP from the alkaline environment

Introduction Reinforced concrete is a common building material for construction of facilities and structures While concrete has high compressive strength it has limited tensile strength To overcome these tensile limitations reinforcing bars (rebar) are used in the tension side of concrete structures

Steel rebar has historically been used as an effective and cost efficient concrete reinforcement W hen not subjected to chloride ion attack steel reinforcement can last for decades without exhibiting any visible signs of deterioration

However steel rebar is very susceptible to oxidation (rust) when exposed to chlorides Examples of such exposure include coastal areas salt contaminated aggregates used in the concrete mixture and sites where aggressive chemicals and ground conditions exist In cold climates treating snow with salt is another cause of accelerated deterioration of concrete bridge decks When corrosion of steel rebar occurs the resulting corrosion products have a volume 2 to 5 times larger than the original steel reinforcement As the concrete cannot physically sustain the high internal tensile stresses developed from this volume increase it eventually may crack and spall causing further deterioration of the steel (Figure 1) The combination of ongoing deterioration and loss of reinforcement properties ultimately requires potentially significant and high cost repairs and possibly the endangerment of the structure itself

QUEENS LAND ROA DS Edition No II September 201 1 40

Figure 1 Concrete spalling of a bridge soffit in a corrosive env-ironment

GFRP bars are a competitive reinforcing option in reinforced concrete members subjected to flexure and shear GFRP has compelling physical and mechanical properties corrosion resistance and electromagnetic transparency The lise of GFRP reinforcement is particularly attractive for structures that operate in aggressive environments such as in coastal regions or for buildings that host magnetic resonance imaging (MRT) units or other equipment sensitive to electromagnetic fields

Brief history Fibre reinforced polymers (FRP) have been used [or decades in the aeronautical aerospace automotive and other fields (FRP is the generic name and its primary difference from GFRP is that it can be composed of a range of materials whereas the GFRP is reinforced with glass fibres) Their use in civil engineering works dates back to the 1950s when GFRP bars were first investigated for structural use However it was not until the 1970s that FRP was finally considered for structural engineering applications and its superior performance over epoxy coated steel was recognised The first applications of glass fibre FRP were not successful due to its poor performance within thermosetting resins cured at high molding pressures (I) Since their early introduction many new FRP materials have been developed with a range of different forms such as bars fabric 20 grids 3D grids or standard structural shapes (Figure 2) The fibre materials include aramid (Kevlarreg) polyvinyl carbon and improved glass fibres

Figure 2 Available shapes of FRP products

Manufacturing of FRP A manufacturing process called Pultrusion is the most common technique used for manufacturing continuous lengths of FRP bars that are of constant or nearly constant in profile Figure 3 below shows this manufacturing technique Continuous strands of reinforcing material are drawn from roving bobbins A veil is introduced and they pass through a resin tank where they are saturated with resin followed by a number of wiper rings to remove excess resin The strands are then led to a pre-former and then formed to their final shape and cured by the heated die The speed of pulling through the die is predetermined by the curing time needed To ensure a good bond with concrete the surface of the bars is usually coated with sand and then cut to length (Figure 4) The application of the sand coating is an additional process a layer of resin is applied (but not under heated conditions) and then the bar is coated with a thin layer of sand

QUEENSLAND ROADS Edition No II September 2011 41

Figure 3 Pultrusion process for forming FRP bars

Figure 4 FRP bars with sand coated finish

SI Nominal

diameter (mm) I Tensile modulus of I elasticity (GPa)1

I

Guaranteed tensile strength (MPa)

~6 635 461 788 I

~10 953 462 765

~13 1270 464 710 I

~16 1588 482 683

~19 1905 476 656 I

ltIgt 25 2540 510 611

Figure 5 FRP bar properties

1 For reference the elastic modulus for steel is 200 GPa

QU EENSLAND ROADS Edition No 11 September 20 11 42

Similar to steel reinforcement FRP bars are produced in different diameters depending on the manufacturing process The surface of the rods can be spiral straight sanded-straight sanded-braided and deformed The bar to concrete bond is equal to or better than the bond with steel reinforcing bars

The mechanical properties of FRP reinforcing bars are given in Figure 5

Resins A very important issue in the manufacture of composites is the selection of the optimum matrix because the physical and thermal properties of the matrix significantly affect the final mechanical properties as well as the manufacturing process In order to be able to exploit the full strength of the fibres the matrix should be able to develop a higher ultimate strain than the fibres (2)

The matrix not only coats the fibres and protects them from mechanical abrasion and chemical attack but also transfers stresses betNeen the fibres Other very important roles of the matrix are the transfer of intershylaminar and in-plane shear within the composite and the provision or laterall support to the fibres against

buckling when subjected to compressive loads (3)

There are two types of polymeric matrices commonly used for FRP composites - thermosetting and thermoplastic Thermosetting polymers are used more often than thermoplastic They are low molecular weight liquids with very low viscosity (3) and with their molecules joined together by chemical crossshylinks Hence they form a rigid three dimensional structure that once set cannot be reshaped by applying heat or pressure Thermosetting polymers are processed in a liquid state to obtain good wet-out of fibres Some commonly used thermosetting polymers are polyesters vinyl esters and epoxies These materials have good thermal stability and chemical resistance and undergo low creep and stress relaxation The vinyl ester resin predominately cures during the pultrusion manufacturing process as the bar is drawn through the heated die By the time the bar reaches room temperature it is considered to be fully cured

Thermosetting polymers have relatively low strain to failure resulting in low impact strength Two major disadvantages are their short shelf life and long manufacturing time Mechanical properties of some thermosetting resins are provided in Figure 6

Resin Specific gravity Tensile strength

(MPa) Tensile

modulus (GPa) Cure shrinkage

()

Epoxy 120-1 30 550 - 1300 275-410 10 - 50

Polyester 110 - 140 345 - 1035 210-345 50 - 120

Vinyl ester 112 - 132 730 - 8100 300 - 335 54 - 103

Figure 6 Typical properties of thermosetting resins

QU EENSLAND ROADS Edition No II September 20 II 43

Design standards for GFRP The design of reinforced concrete using FRP reinforcing bars is not currently codified by any Australian standard however there is a Canadian code (14) and a publication by the American Concrete Institute (4) Both of these documents use the limitshystate approach in their design

A design manual (5) has been published by thc ISIS Canada Research Network2 which describes the design process in line with the Canadian code It is patiicularly helpful as it describes the differences in design and behaviour between steel reinforced and FRP reinforced structures

The two main differences in designing reinforced concrete structures using FRP reinforcement are

bull FRP does not yield in a similar way as steel

bull FRP bars have a lower modulus of elasticity than steel Furthermore both codes do not allow for the use of FRP reinforcement as longitudinal reinforcement in columns (due to insufficient research in that area)

Benefits of GFRP The benefits ofGFRP rebar are as follows

bull Corrosion resistance - when bonded in concrete it does not react to salt chemical products or the alkali in concrete As GFRP is not manufactured from steel it does not rust

bull Superior tensile strength - GFRP rebar produced by the pultrusion process offers a tensile strength up to twice that of normal structural steel (based on area)

bull Thermal expansion - GFRP rebar offers a level of thermal expansion comparable to that of concrete due to its 80 silica content

bull Electric and magnetic neutrality - as GFRP rebar does not contain any metals it will not cause interference with strong magnetic fields or when operating sensitive electronic equipment or instruments

bull Thermal insulation - GFRP rebar does not create a thermal bridge within structures

bull Lightweight - GFRP rebar is a quarter the weight of steel rebar of equivalent strength It offers significant savings in transportation and installation

Figure 7 Light weight bundles of FRP are easily moved on site

Utilising these inherent benefits GFRP rebar has a cost effective application as a concrete reinforcing bar in the following markets when analysed on a life-cycle cost basis

bull Reinforced concrete exposed to corrosive environments - car parking structures bridge decks parapets curbs retaining walls foundations roads and slabs

bull Structures b uilt in or close proximity to sea water (Figures 89) - quays retaining wall piers jetties boat ramps caissons decks piles bulkheads floating structures canals roads and buildings offshore platforms swimming pools and aquanums

bull Applications subjected to other corrosive agents - wastewater treatment plants petrochemical plants pulppaper mills liquid gas plants pipelinestanks for fossil fuel cooling towers chimneys mining operations of various types nuclear power plants

2 ISIS Canada Research Network (Intelligent Sensing for Innovative Structures) was established in 1995 to provide civil engineers with smarter ways to build repair and monitor structures using high-strength rlon-corroding fibre reinforced polymers (FRPs) and fibre optic sensors (FOSs)

QUEENSLAND ROADS Edition No II September lOll 44

bull Applications rcquiring low electric conductivity or electromagnetic neutrality - aluminium and copper smelting plants manholes for electrical and telephone communication equipment bases for transmissiontelecommunication towers airport control towers MRI in hospitals railroad crossing sites and specialised military structures

bull Miningtunnelingboring applications shytemporary concrete structures mining walls underground rapid transit structures rock anchors and wash down areas

bull Weight sensitive structures - concrete construction in areas of poor load bearing soil conditions remote geographical locations sensitive environmental areas or active seismic sites posing special issues that necessitate the use of lightweight reinforcement

bull Thermally sensitive applications - apartment patio decks thermally insulated concrete housing and basements thermally heated floors and conditioning rooms

Figure 8 GFRP used on the Anthon Jetty Wyndham Western Australia

Figure 9 Precast deck slab and GFRP rebar for the Anthon Jetty

Technical case study - durability of GFRP composite rodsJ

One of the most pressing durab ility concerns of our time is the rap id corrosion of reinforcing steel that occurs in concrete structures subjected to chloride rich environments Its often argued that if the steel reinforcement in such structures could be replaced by chemically inert reinforcement such as fibre reinforced polymers the problem of cOITosion could be eliminated Of the various options the most economical choice is GFRP but it has been reported to be highly vulnerable to the alkaline environment of concrete

A report (6) summarising the results of several published studies on the alkali resistance of GFRP categorically concluded that GFRP should not be used in direct contact with concrete Similar conclusions were drawn by other researchers (789) Unfortunately all of these studies were conducted by subjecting GFRP to an idealised simulated high pH fluid environment often involving high temperatures Such environments are unduly harsh as they provide an unlimited supply of hydroxyl ions - a condition not present in rea l concrete Also they provide full saturation which is also rarely the case Field conditions should therefore be expected to be different

from these idealised laboratory conditions

3 The bulk of this section comes from a technical report as indicated under reference (5)

QUEENSLAND ROADS Edition No II September 20 11 45

Name of structure Age years

Concrete strength MPa

Seasonal temperature range middotC

Type of chloride exposure

Hall Harbor Wharf 5 45 -35 to 35 Marine

Joffre Bridge 7 45 -35 to 35 Deicing salts

Chatham Bridge 8 35 -24 to 30 Deicing salts

Crowchild Trail Bridge 8 35 -15t023 Deicing salts

Waterloo Creek Bridge 6 35 oto 23 Deicing salts

Figure 10 Samples were taken from these five structures

In 2004 a major study by ISIS Canada was launched to obtain field data with respect to the durability of GFRP in concrete exposed to natural environments Concrete cores containing GFRP were removed from five exposed structures which were five to eight years old (Figure 10) The GFRP was analysed for its physical and chemical composition at the microscopic level Direct comparisons were carried out with control samples - GFRP rods preserved under controlled laboratory conditions

At least ten 75ml11 diameter core samples containing GFRP were taken from each of the five structures Three concrete cores from each of five structures were sent for analysis to three teams of material scientists working independently at various Canadian universities The removal ofGFRP samples along with sUlTounding concrete and the polishing of the samples required special care given that GFRP and concrete have different hardness values

After sample preparation the GFRP reinforcement and surrounding concrete were analysed using several analytical methods The entire surface of each sample was examined and photographs were taken at various locations

Scanning electron microscopy (SEM) was lIsed for a detailed examination of the glass fibrematrix interface and individual glass fibres The specimens used in SEM analyses were also analysed by energy dispersive x-ray (EDX) to detect potential chemical changes in the matrix and glass fibres due to the ingress of alkali from the concrete pore solution Chemical changes in the polymeric matrix of GFRP were characterised by Fourier transfonn infrared spectroscopy (FTIR) Finally changes in the glass transition temperature Tg of the matrix due to exposure to severe environmental conditions were determined using differential scanning calorimetry (DSC)

Findings - The results obtained by the three research teams were very similar A complete account of their findings is available in their respective individual reports (10 I 112) The results found that there was no degradation of the GFRP in the samples provided The results from this scientific study based on samples from actual engineering structures was not in agreement with the results obtained in some simulated laboratory studies

The results from SEM and EDX analyses confirmed that there is no degradation of the GFRP in the concrete structures The EDX analyses also indicated no alkali ingress in the GFRP from the concrete

QUEENS LAND ROADS Edition No II Septelilber 2011 46

pore solution The matrix in all GFRPs was intact and unaltered from its original state The results from the FTIR and DSC analyses supported the results from the SEM examinations The FTIR and DSC results indicated that neither hydrolysis nor significant changes in the glass transition temperature of the matrix After exposure for 5 to 8 years to the combined effects of the alkaline environment in the concrete and the external natural environment no detrimental effects were found

The results of this study were used as the basis for changes to the Canadian Highway Bridge Design Code (13) allowing the use of GFRP both as primary reinforcement and prestressing tendons in concrete components The proviso was made that the stress level for the serviceability limit state does not exceed 25 of its ultimate tensile strength Other refenmces to the use ofGFRP can be found in (141617)

Summary and Conclusion GFRP has a very important role to playas reinforcement in concrete structures that will be exposed to harsh environmental conditions where traditional steel reinforcement could corrode It is the unique physical properties of GFRP that makes it suitable for applications where conventional steel would be unsuitable Detailed laboratory studies of samples taken from reinforced concrete structures aged from five to eight years old have confim1ed that GFRP has performed extremely well when exposed to harsh field conditions

References I Parklyn B Glass Reinforced Plastics Iliffe

London 1970

2 Phillips LN Design with Advanced Composite Materials Springer~Verlag 1989

3 ACI Committee 440 State-olthe-Art Report on Fiber Reinforced Plastic (FRP) Reinforcement for Concrete Structures American Concrete Institute 92-S61 Nov 1995 wwwconcreteorg

4 ACI Committee 440 Guidefor the Design and Construction ofStructural Concrete Reinforced with FRP bars American Concrete Institute ACI 4401 R-06 440 I 03 April 2006 wwwconcrete org

5 Mufti A Banthia N Benmokr B Boulfizaane M Newhook J Durability ofGFRP Composite Rods Concrete international Vol 29 Issue 2 February 2007

6 Malvar J Durability ofComposites in Reinforced Concrete Durability of Fiber Reinforced Polymer (FRP) Composite for Construction Proceedings of the First International Conference on Durability of Composites B Benmokrane and Rahman eds Sherbrooke QB Canada 1998

7 Uomoto r Durability ofFRP as Reinforcement for Concrete Structures Proceedings of the 3rd International Conference on Advanced Composite Materials in Bridges and Structures J Bumar and AG Razaqpur eds Canadian Society for Civil Engineering Ottawa ON Canada 2000

8 Sen Research Marsical D Issa M Shahawy M Durahili(v and Ductility ofAdvanced Composites Structural Engineering in Natural Hazards Mitigation V 2 AB-SAng and R Villaverde eds Structures Congress ASCE Irvine CA 1993

QUEENSLAND ROADS Edition No II September 20 11 47

Figure 1 Concrete spalling of a bridge soffit in a corrosive env-ironment

GFRP bars are a competitive reinforcing option in reinforced concrete members subjected to flexure and shear GFRP has compelling physical and mechanical properties corrosion resistance and electromagnetic transparency The lise of GFRP reinforcement is particularly attractive for structures that operate in aggressive environments such as in coastal regions or for buildings that host magnetic resonance imaging (MRT) units or other equipment sensitive to electromagnetic fields

Brief history Fibre reinforced polymers (FRP) have been used [or decades in the aeronautical aerospace automotive and other fields (FRP is the generic name and its primary difference from GFRP is that it can be composed of a range of materials whereas the GFRP is reinforced with glass fibres) Their use in civil engineering works dates back to the 1950s when GFRP bars were first investigated for structural use However it was not until the 1970s that FRP was finally considered for structural engineering applications and its superior performance over epoxy coated steel was recognised The first applications of glass fibre FRP were not successful due to its poor performance within thermosetting resins cured at high molding pressures (I) Since their early introduction many new FRP materials have been developed with a range of different forms such as bars fabric 20 grids 3D grids or standard structural shapes (Figure 2) The fibre materials include aramid (Kevlarreg) polyvinyl carbon and improved glass fibres

Figure 2 Available shapes of FRP products

Manufacturing of FRP A manufacturing process called Pultrusion is the most common technique used for manufacturing continuous lengths of FRP bars that are of constant or nearly constant in profile Figure 3 below shows this manufacturing technique Continuous strands of reinforcing material are drawn from roving bobbins A veil is introduced and they pass through a resin tank where they are saturated with resin followed by a number of wiper rings to remove excess resin The strands are then led to a pre-former and then formed to their final shape and cured by the heated die The speed of pulling through the die is predetermined by the curing time needed To ensure a good bond with concrete the surface of the bars is usually coated with sand and then cut to length (Figure 4) The application of the sand coating is an additional process a layer of resin is applied (but not under heated conditions) and then the bar is coated with a thin layer of sand

QUEENSLAND ROADS Edition No II September 2011 41

Figure 3 Pultrusion process for forming FRP bars

Figure 4 FRP bars with sand coated finish

SI Nominal

diameter (mm) I Tensile modulus of I elasticity (GPa)1

I

Guaranteed tensile strength (MPa)

~6 635 461 788 I

~10 953 462 765

~13 1270 464 710 I

~16 1588 482 683

~19 1905 476 656 I

ltIgt 25 2540 510 611

Figure 5 FRP bar properties

1 For reference the elastic modulus for steel is 200 GPa

QU EENSLAND ROADS Edition No 11 September 20 11 42

Similar to steel reinforcement FRP bars are produced in different diameters depending on the manufacturing process The surface of the rods can be spiral straight sanded-straight sanded-braided and deformed The bar to concrete bond is equal to or better than the bond with steel reinforcing bars

The mechanical properties of FRP reinforcing bars are given in Figure 5

Resins A very important issue in the manufacture of composites is the selection of the optimum matrix because the physical and thermal properties of the matrix significantly affect the final mechanical properties as well as the manufacturing process In order to be able to exploit the full strength of the fibres the matrix should be able to develop a higher ultimate strain than the fibres (2)

The matrix not only coats the fibres and protects them from mechanical abrasion and chemical attack but also transfers stresses betNeen the fibres Other very important roles of the matrix are the transfer of intershylaminar and in-plane shear within the composite and the provision or laterall support to the fibres against

buckling when subjected to compressive loads (3)

There are two types of polymeric matrices commonly used for FRP composites - thermosetting and thermoplastic Thermosetting polymers are used more often than thermoplastic They are low molecular weight liquids with very low viscosity (3) and with their molecules joined together by chemical crossshylinks Hence they form a rigid three dimensional structure that once set cannot be reshaped by applying heat or pressure Thermosetting polymers are processed in a liquid state to obtain good wet-out of fibres Some commonly used thermosetting polymers are polyesters vinyl esters and epoxies These materials have good thermal stability and chemical resistance and undergo low creep and stress relaxation The vinyl ester resin predominately cures during the pultrusion manufacturing process as the bar is drawn through the heated die By the time the bar reaches room temperature it is considered to be fully cured

Thermosetting polymers have relatively low strain to failure resulting in low impact strength Two major disadvantages are their short shelf life and long manufacturing time Mechanical properties of some thermosetting resins are provided in Figure 6

Resin Specific gravity Tensile strength

(MPa) Tensile

modulus (GPa) Cure shrinkage

()

Epoxy 120-1 30 550 - 1300 275-410 10 - 50

Polyester 110 - 140 345 - 1035 210-345 50 - 120

Vinyl ester 112 - 132 730 - 8100 300 - 335 54 - 103

Figure 6 Typical properties of thermosetting resins

QU EENSLAND ROADS Edition No II September 20 II 43

Design standards for GFRP The design of reinforced concrete using FRP reinforcing bars is not currently codified by any Australian standard however there is a Canadian code (14) and a publication by the American Concrete Institute (4) Both of these documents use the limitshystate approach in their design

A design manual (5) has been published by thc ISIS Canada Research Network2 which describes the design process in line with the Canadian code It is patiicularly helpful as it describes the differences in design and behaviour between steel reinforced and FRP reinforced structures

The two main differences in designing reinforced concrete structures using FRP reinforcement are

bull FRP does not yield in a similar way as steel

bull FRP bars have a lower modulus of elasticity than steel Furthermore both codes do not allow for the use of FRP reinforcement as longitudinal reinforcement in columns (due to insufficient research in that area)

Benefits of GFRP The benefits ofGFRP rebar are as follows

bull Corrosion resistance - when bonded in concrete it does not react to salt chemical products or the alkali in concrete As GFRP is not manufactured from steel it does not rust

bull Superior tensile strength - GFRP rebar produced by the pultrusion process offers a tensile strength up to twice that of normal structural steel (based on area)

bull Thermal expansion - GFRP rebar offers a level of thermal expansion comparable to that of concrete due to its 80 silica content

bull Electric and magnetic neutrality - as GFRP rebar does not contain any metals it will not cause interference with strong magnetic fields or when operating sensitive electronic equipment or instruments

bull Thermal insulation - GFRP rebar does not create a thermal bridge within structures

bull Lightweight - GFRP rebar is a quarter the weight of steel rebar of equivalent strength It offers significant savings in transportation and installation

Figure 7 Light weight bundles of FRP are easily moved on site

Utilising these inherent benefits GFRP rebar has a cost effective application as a concrete reinforcing bar in the following markets when analysed on a life-cycle cost basis

bull Reinforced concrete exposed to corrosive environments - car parking structures bridge decks parapets curbs retaining walls foundations roads and slabs

bull Structures b uilt in or close proximity to sea water (Figures 89) - quays retaining wall piers jetties boat ramps caissons decks piles bulkheads floating structures canals roads and buildings offshore platforms swimming pools and aquanums

bull Applications subjected to other corrosive agents - wastewater treatment plants petrochemical plants pulppaper mills liquid gas plants pipelinestanks for fossil fuel cooling towers chimneys mining operations of various types nuclear power plants

2 ISIS Canada Research Network (Intelligent Sensing for Innovative Structures) was established in 1995 to provide civil engineers with smarter ways to build repair and monitor structures using high-strength rlon-corroding fibre reinforced polymers (FRPs) and fibre optic sensors (FOSs)

QUEENSLAND ROADS Edition No II September lOll 44

bull Applications rcquiring low electric conductivity or electromagnetic neutrality - aluminium and copper smelting plants manholes for electrical and telephone communication equipment bases for transmissiontelecommunication towers airport control towers MRI in hospitals railroad crossing sites and specialised military structures

bull Miningtunnelingboring applications shytemporary concrete structures mining walls underground rapid transit structures rock anchors and wash down areas

bull Weight sensitive structures - concrete construction in areas of poor load bearing soil conditions remote geographical locations sensitive environmental areas or active seismic sites posing special issues that necessitate the use of lightweight reinforcement

bull Thermally sensitive applications - apartment patio decks thermally insulated concrete housing and basements thermally heated floors and conditioning rooms

Figure 8 GFRP used on the Anthon Jetty Wyndham Western Australia

Figure 9 Precast deck slab and GFRP rebar for the Anthon Jetty

Technical case study - durability of GFRP composite rodsJ

One of the most pressing durab ility concerns of our time is the rap id corrosion of reinforcing steel that occurs in concrete structures subjected to chloride rich environments Its often argued that if the steel reinforcement in such structures could be replaced by chemically inert reinforcement such as fibre reinforced polymers the problem of cOITosion could be eliminated Of the various options the most economical choice is GFRP but it has been reported to be highly vulnerable to the alkaline environment of concrete

A report (6) summarising the results of several published studies on the alkali resistance of GFRP categorically concluded that GFRP should not be used in direct contact with concrete Similar conclusions were drawn by other researchers (789) Unfortunately all of these studies were conducted by subjecting GFRP to an idealised simulated high pH fluid environment often involving high temperatures Such environments are unduly harsh as they provide an unlimited supply of hydroxyl ions - a condition not present in rea l concrete Also they provide full saturation which is also rarely the case Field conditions should therefore be expected to be different

from these idealised laboratory conditions

3 The bulk of this section comes from a technical report as indicated under reference (5)

QUEENSLAND ROADS Edition No II September 20 11 45

Name of structure Age years

Concrete strength MPa

Seasonal temperature range middotC

Type of chloride exposure

Hall Harbor Wharf 5 45 -35 to 35 Marine

Joffre Bridge 7 45 -35 to 35 Deicing salts

Chatham Bridge 8 35 -24 to 30 Deicing salts

Crowchild Trail Bridge 8 35 -15t023 Deicing salts

Waterloo Creek Bridge 6 35 oto 23 Deicing salts

Figure 10 Samples were taken from these five structures

In 2004 a major study by ISIS Canada was launched to obtain field data with respect to the durability of GFRP in concrete exposed to natural environments Concrete cores containing GFRP were removed from five exposed structures which were five to eight years old (Figure 10) The GFRP was analysed for its physical and chemical composition at the microscopic level Direct comparisons were carried out with control samples - GFRP rods preserved under controlled laboratory conditions

At least ten 75ml11 diameter core samples containing GFRP were taken from each of the five structures Three concrete cores from each of five structures were sent for analysis to three teams of material scientists working independently at various Canadian universities The removal ofGFRP samples along with sUlTounding concrete and the polishing of the samples required special care given that GFRP and concrete have different hardness values

After sample preparation the GFRP reinforcement and surrounding concrete were analysed using several analytical methods The entire surface of each sample was examined and photographs were taken at various locations

Scanning electron microscopy (SEM) was lIsed for a detailed examination of the glass fibrematrix interface and individual glass fibres The specimens used in SEM analyses were also analysed by energy dispersive x-ray (EDX) to detect potential chemical changes in the matrix and glass fibres due to the ingress of alkali from the concrete pore solution Chemical changes in the polymeric matrix of GFRP were characterised by Fourier transfonn infrared spectroscopy (FTIR) Finally changes in the glass transition temperature Tg of the matrix due to exposure to severe environmental conditions were determined using differential scanning calorimetry (DSC)

Findings - The results obtained by the three research teams were very similar A complete account of their findings is available in their respective individual reports (10 I 112) The results found that there was no degradation of the GFRP in the samples provided The results from this scientific study based on samples from actual engineering structures was not in agreement with the results obtained in some simulated laboratory studies

The results from SEM and EDX analyses confirmed that there is no degradation of the GFRP in the concrete structures The EDX analyses also indicated no alkali ingress in the GFRP from the concrete

QUEENS LAND ROADS Edition No II Septelilber 2011 46

pore solution The matrix in all GFRPs was intact and unaltered from its original state The results from the FTIR and DSC analyses supported the results from the SEM examinations The FTIR and DSC results indicated that neither hydrolysis nor significant changes in the glass transition temperature of the matrix After exposure for 5 to 8 years to the combined effects of the alkaline environment in the concrete and the external natural environment no detrimental effects were found

The results of this study were used as the basis for changes to the Canadian Highway Bridge Design Code (13) allowing the use of GFRP both as primary reinforcement and prestressing tendons in concrete components The proviso was made that the stress level for the serviceability limit state does not exceed 25 of its ultimate tensile strength Other refenmces to the use ofGFRP can be found in (141617)

Summary and Conclusion GFRP has a very important role to playas reinforcement in concrete structures that will be exposed to harsh environmental conditions where traditional steel reinforcement could corrode It is the unique physical properties of GFRP that makes it suitable for applications where conventional steel would be unsuitable Detailed laboratory studies of samples taken from reinforced concrete structures aged from five to eight years old have confim1ed that GFRP has performed extremely well when exposed to harsh field conditions

References I Parklyn B Glass Reinforced Plastics Iliffe

London 1970

2 Phillips LN Design with Advanced Composite Materials Springer~Verlag 1989

3 ACI Committee 440 State-olthe-Art Report on Fiber Reinforced Plastic (FRP) Reinforcement for Concrete Structures American Concrete Institute 92-S61 Nov 1995 wwwconcreteorg

4 ACI Committee 440 Guidefor the Design and Construction ofStructural Concrete Reinforced with FRP bars American Concrete Institute ACI 4401 R-06 440 I 03 April 2006 wwwconcrete org

5 Mufti A Banthia N Benmokr B Boulfizaane M Newhook J Durability ofGFRP Composite Rods Concrete international Vol 29 Issue 2 February 2007

6 Malvar J Durability ofComposites in Reinforced Concrete Durability of Fiber Reinforced Polymer (FRP) Composite for Construction Proceedings of the First International Conference on Durability of Composites B Benmokrane and Rahman eds Sherbrooke QB Canada 1998

7 Uomoto r Durability ofFRP as Reinforcement for Concrete Structures Proceedings of the 3rd International Conference on Advanced Composite Materials in Bridges and Structures J Bumar and AG Razaqpur eds Canadian Society for Civil Engineering Ottawa ON Canada 2000

8 Sen Research Marsical D Issa M Shahawy M Durahili(v and Ductility ofAdvanced Composites Structural Engineering in Natural Hazards Mitigation V 2 AB-SAng and R Villaverde eds Structures Congress ASCE Irvine CA 1993

QUEENSLAND ROADS Edition No II September 20 11 47

Figure 3 Pultrusion process for forming FRP bars

Figure 4 FRP bars with sand coated finish

SI Nominal

diameter (mm) I Tensile modulus of I elasticity (GPa)1

I

Guaranteed tensile strength (MPa)

~6 635 461 788 I

~10 953 462 765

~13 1270 464 710 I

~16 1588 482 683

~19 1905 476 656 I

ltIgt 25 2540 510 611

Figure 5 FRP bar properties

1 For reference the elastic modulus for steel is 200 GPa

QU EENSLAND ROADS Edition No 11 September 20 11 42

Similar to steel reinforcement FRP bars are produced in different diameters depending on the manufacturing process The surface of the rods can be spiral straight sanded-straight sanded-braided and deformed The bar to concrete bond is equal to or better than the bond with steel reinforcing bars

The mechanical properties of FRP reinforcing bars are given in Figure 5

Resins A very important issue in the manufacture of composites is the selection of the optimum matrix because the physical and thermal properties of the matrix significantly affect the final mechanical properties as well as the manufacturing process In order to be able to exploit the full strength of the fibres the matrix should be able to develop a higher ultimate strain than the fibres (2)

The matrix not only coats the fibres and protects them from mechanical abrasion and chemical attack but also transfers stresses betNeen the fibres Other very important roles of the matrix are the transfer of intershylaminar and in-plane shear within the composite and the provision or laterall support to the fibres against

buckling when subjected to compressive loads (3)

There are two types of polymeric matrices commonly used for FRP composites - thermosetting and thermoplastic Thermosetting polymers are used more often than thermoplastic They are low molecular weight liquids with very low viscosity (3) and with their molecules joined together by chemical crossshylinks Hence they form a rigid three dimensional structure that once set cannot be reshaped by applying heat or pressure Thermosetting polymers are processed in a liquid state to obtain good wet-out of fibres Some commonly used thermosetting polymers are polyesters vinyl esters and epoxies These materials have good thermal stability and chemical resistance and undergo low creep and stress relaxation The vinyl ester resin predominately cures during the pultrusion manufacturing process as the bar is drawn through the heated die By the time the bar reaches room temperature it is considered to be fully cured

Thermosetting polymers have relatively low strain to failure resulting in low impact strength Two major disadvantages are their short shelf life and long manufacturing time Mechanical properties of some thermosetting resins are provided in Figure 6

Resin Specific gravity Tensile strength

(MPa) Tensile

modulus (GPa) Cure shrinkage

()

Epoxy 120-1 30 550 - 1300 275-410 10 - 50

Polyester 110 - 140 345 - 1035 210-345 50 - 120

Vinyl ester 112 - 132 730 - 8100 300 - 335 54 - 103

Figure 6 Typical properties of thermosetting resins

QU EENSLAND ROADS Edition No II September 20 II 43

Design standards for GFRP The design of reinforced concrete using FRP reinforcing bars is not currently codified by any Australian standard however there is a Canadian code (14) and a publication by the American Concrete Institute (4) Both of these documents use the limitshystate approach in their design

A design manual (5) has been published by thc ISIS Canada Research Network2 which describes the design process in line with the Canadian code It is patiicularly helpful as it describes the differences in design and behaviour between steel reinforced and FRP reinforced structures

The two main differences in designing reinforced concrete structures using FRP reinforcement are

bull FRP does not yield in a similar way as steel

bull FRP bars have a lower modulus of elasticity than steel Furthermore both codes do not allow for the use of FRP reinforcement as longitudinal reinforcement in columns (due to insufficient research in that area)

Benefits of GFRP The benefits ofGFRP rebar are as follows

bull Corrosion resistance - when bonded in concrete it does not react to salt chemical products or the alkali in concrete As GFRP is not manufactured from steel it does not rust

bull Superior tensile strength - GFRP rebar produced by the pultrusion process offers a tensile strength up to twice that of normal structural steel (based on area)

bull Thermal expansion - GFRP rebar offers a level of thermal expansion comparable to that of concrete due to its 80 silica content

bull Electric and magnetic neutrality - as GFRP rebar does not contain any metals it will not cause interference with strong magnetic fields or when operating sensitive electronic equipment or instruments

bull Thermal insulation - GFRP rebar does not create a thermal bridge within structures

bull Lightweight - GFRP rebar is a quarter the weight of steel rebar of equivalent strength It offers significant savings in transportation and installation

Figure 7 Light weight bundles of FRP are easily moved on site

Utilising these inherent benefits GFRP rebar has a cost effective application as a concrete reinforcing bar in the following markets when analysed on a life-cycle cost basis

bull Reinforced concrete exposed to corrosive environments - car parking structures bridge decks parapets curbs retaining walls foundations roads and slabs

bull Structures b uilt in or close proximity to sea water (Figures 89) - quays retaining wall piers jetties boat ramps caissons decks piles bulkheads floating structures canals roads and buildings offshore platforms swimming pools and aquanums

bull Applications subjected to other corrosive agents - wastewater treatment plants petrochemical plants pulppaper mills liquid gas plants pipelinestanks for fossil fuel cooling towers chimneys mining operations of various types nuclear power plants

2 ISIS Canada Research Network (Intelligent Sensing for Innovative Structures) was established in 1995 to provide civil engineers with smarter ways to build repair and monitor structures using high-strength rlon-corroding fibre reinforced polymers (FRPs) and fibre optic sensors (FOSs)

QUEENSLAND ROADS Edition No II September lOll 44

bull Applications rcquiring low electric conductivity or electromagnetic neutrality - aluminium and copper smelting plants manholes for electrical and telephone communication equipment bases for transmissiontelecommunication towers airport control towers MRI in hospitals railroad crossing sites and specialised military structures

bull Miningtunnelingboring applications shytemporary concrete structures mining walls underground rapid transit structures rock anchors and wash down areas

bull Weight sensitive structures - concrete construction in areas of poor load bearing soil conditions remote geographical locations sensitive environmental areas or active seismic sites posing special issues that necessitate the use of lightweight reinforcement

bull Thermally sensitive applications - apartment patio decks thermally insulated concrete housing and basements thermally heated floors and conditioning rooms

Figure 8 GFRP used on the Anthon Jetty Wyndham Western Australia

Figure 9 Precast deck slab and GFRP rebar for the Anthon Jetty

Technical case study - durability of GFRP composite rodsJ

One of the most pressing durab ility concerns of our time is the rap id corrosion of reinforcing steel that occurs in concrete structures subjected to chloride rich environments Its often argued that if the steel reinforcement in such structures could be replaced by chemically inert reinforcement such as fibre reinforced polymers the problem of cOITosion could be eliminated Of the various options the most economical choice is GFRP but it has been reported to be highly vulnerable to the alkaline environment of concrete

A report (6) summarising the results of several published studies on the alkali resistance of GFRP categorically concluded that GFRP should not be used in direct contact with concrete Similar conclusions were drawn by other researchers (789) Unfortunately all of these studies were conducted by subjecting GFRP to an idealised simulated high pH fluid environment often involving high temperatures Such environments are unduly harsh as they provide an unlimited supply of hydroxyl ions - a condition not present in rea l concrete Also they provide full saturation which is also rarely the case Field conditions should therefore be expected to be different

from these idealised laboratory conditions

3 The bulk of this section comes from a technical report as indicated under reference (5)

QUEENSLAND ROADS Edition No II September 20 11 45

Name of structure Age years

Concrete strength MPa

Seasonal temperature range middotC

Type of chloride exposure

Hall Harbor Wharf 5 45 -35 to 35 Marine

Joffre Bridge 7 45 -35 to 35 Deicing salts

Chatham Bridge 8 35 -24 to 30 Deicing salts

Crowchild Trail Bridge 8 35 -15t023 Deicing salts

Waterloo Creek Bridge 6 35 oto 23 Deicing salts

Figure 10 Samples were taken from these five structures

In 2004 a major study by ISIS Canada was launched to obtain field data with respect to the durability of GFRP in concrete exposed to natural environments Concrete cores containing GFRP were removed from five exposed structures which were five to eight years old (Figure 10) The GFRP was analysed for its physical and chemical composition at the microscopic level Direct comparisons were carried out with control samples - GFRP rods preserved under controlled laboratory conditions

At least ten 75ml11 diameter core samples containing GFRP were taken from each of the five structures Three concrete cores from each of five structures were sent for analysis to three teams of material scientists working independently at various Canadian universities The removal ofGFRP samples along with sUlTounding concrete and the polishing of the samples required special care given that GFRP and concrete have different hardness values

After sample preparation the GFRP reinforcement and surrounding concrete were analysed using several analytical methods The entire surface of each sample was examined and photographs were taken at various locations

Scanning electron microscopy (SEM) was lIsed for a detailed examination of the glass fibrematrix interface and individual glass fibres The specimens used in SEM analyses were also analysed by energy dispersive x-ray (EDX) to detect potential chemical changes in the matrix and glass fibres due to the ingress of alkali from the concrete pore solution Chemical changes in the polymeric matrix of GFRP were characterised by Fourier transfonn infrared spectroscopy (FTIR) Finally changes in the glass transition temperature Tg of the matrix due to exposure to severe environmental conditions were determined using differential scanning calorimetry (DSC)

Findings - The results obtained by the three research teams were very similar A complete account of their findings is available in their respective individual reports (10 I 112) The results found that there was no degradation of the GFRP in the samples provided The results from this scientific study based on samples from actual engineering structures was not in agreement with the results obtained in some simulated laboratory studies

The results from SEM and EDX analyses confirmed that there is no degradation of the GFRP in the concrete structures The EDX analyses also indicated no alkali ingress in the GFRP from the concrete

QUEENS LAND ROADS Edition No II Septelilber 2011 46

pore solution The matrix in all GFRPs was intact and unaltered from its original state The results from the FTIR and DSC analyses supported the results from the SEM examinations The FTIR and DSC results indicated that neither hydrolysis nor significant changes in the glass transition temperature of the matrix After exposure for 5 to 8 years to the combined effects of the alkaline environment in the concrete and the external natural environment no detrimental effects were found

The results of this study were used as the basis for changes to the Canadian Highway Bridge Design Code (13) allowing the use of GFRP both as primary reinforcement and prestressing tendons in concrete components The proviso was made that the stress level for the serviceability limit state does not exceed 25 of its ultimate tensile strength Other refenmces to the use ofGFRP can be found in (141617)

Summary and Conclusion GFRP has a very important role to playas reinforcement in concrete structures that will be exposed to harsh environmental conditions where traditional steel reinforcement could corrode It is the unique physical properties of GFRP that makes it suitable for applications where conventional steel would be unsuitable Detailed laboratory studies of samples taken from reinforced concrete structures aged from five to eight years old have confim1ed that GFRP has performed extremely well when exposed to harsh field conditions

References I Parklyn B Glass Reinforced Plastics Iliffe

London 1970

2 Phillips LN Design with Advanced Composite Materials Springer~Verlag 1989

3 ACI Committee 440 State-olthe-Art Report on Fiber Reinforced Plastic (FRP) Reinforcement for Concrete Structures American Concrete Institute 92-S61 Nov 1995 wwwconcreteorg

4 ACI Committee 440 Guidefor the Design and Construction ofStructural Concrete Reinforced with FRP bars American Concrete Institute ACI 4401 R-06 440 I 03 April 2006 wwwconcrete org

5 Mufti A Banthia N Benmokr B Boulfizaane M Newhook J Durability ofGFRP Composite Rods Concrete international Vol 29 Issue 2 February 2007

6 Malvar J Durability ofComposites in Reinforced Concrete Durability of Fiber Reinforced Polymer (FRP) Composite for Construction Proceedings of the First International Conference on Durability of Composites B Benmokrane and Rahman eds Sherbrooke QB Canada 1998

7 Uomoto r Durability ofFRP as Reinforcement for Concrete Structures Proceedings of the 3rd International Conference on Advanced Composite Materials in Bridges and Structures J Bumar and AG Razaqpur eds Canadian Society for Civil Engineering Ottawa ON Canada 2000

8 Sen Research Marsical D Issa M Shahawy M Durahili(v and Ductility ofAdvanced Composites Structural Engineering in Natural Hazards Mitigation V 2 AB-SAng and R Villaverde eds Structures Congress ASCE Irvine CA 1993

QUEENSLAND ROADS Edition No II September 20 11 47

Similar to steel reinforcement FRP bars are produced in different diameters depending on the manufacturing process The surface of the rods can be spiral straight sanded-straight sanded-braided and deformed The bar to concrete bond is equal to or better than the bond with steel reinforcing bars

The mechanical properties of FRP reinforcing bars are given in Figure 5

Resins A very important issue in the manufacture of composites is the selection of the optimum matrix because the physical and thermal properties of the matrix significantly affect the final mechanical properties as well as the manufacturing process In order to be able to exploit the full strength of the fibres the matrix should be able to develop a higher ultimate strain than the fibres (2)

The matrix not only coats the fibres and protects them from mechanical abrasion and chemical attack but also transfers stresses betNeen the fibres Other very important roles of the matrix are the transfer of intershylaminar and in-plane shear within the composite and the provision or laterall support to the fibres against

buckling when subjected to compressive loads (3)

There are two types of polymeric matrices commonly used for FRP composites - thermosetting and thermoplastic Thermosetting polymers are used more often than thermoplastic They are low molecular weight liquids with very low viscosity (3) and with their molecules joined together by chemical crossshylinks Hence they form a rigid three dimensional structure that once set cannot be reshaped by applying heat or pressure Thermosetting polymers are processed in a liquid state to obtain good wet-out of fibres Some commonly used thermosetting polymers are polyesters vinyl esters and epoxies These materials have good thermal stability and chemical resistance and undergo low creep and stress relaxation The vinyl ester resin predominately cures during the pultrusion manufacturing process as the bar is drawn through the heated die By the time the bar reaches room temperature it is considered to be fully cured

Thermosetting polymers have relatively low strain to failure resulting in low impact strength Two major disadvantages are their short shelf life and long manufacturing time Mechanical properties of some thermosetting resins are provided in Figure 6

Resin Specific gravity Tensile strength

(MPa) Tensile

modulus (GPa) Cure shrinkage

()

Epoxy 120-1 30 550 - 1300 275-410 10 - 50

Polyester 110 - 140 345 - 1035 210-345 50 - 120

Vinyl ester 112 - 132 730 - 8100 300 - 335 54 - 103

Figure 6 Typical properties of thermosetting resins

QU EENSLAND ROADS Edition No II September 20 II 43

Design standards for GFRP The design of reinforced concrete using FRP reinforcing bars is not currently codified by any Australian standard however there is a Canadian code (14) and a publication by the American Concrete Institute (4) Both of these documents use the limitshystate approach in their design

A design manual (5) has been published by thc ISIS Canada Research Network2 which describes the design process in line with the Canadian code It is patiicularly helpful as it describes the differences in design and behaviour between steel reinforced and FRP reinforced structures

The two main differences in designing reinforced concrete structures using FRP reinforcement are

bull FRP does not yield in a similar way as steel

bull FRP bars have a lower modulus of elasticity than steel Furthermore both codes do not allow for the use of FRP reinforcement as longitudinal reinforcement in columns (due to insufficient research in that area)

Benefits of GFRP The benefits ofGFRP rebar are as follows

bull Corrosion resistance - when bonded in concrete it does not react to salt chemical products or the alkali in concrete As GFRP is not manufactured from steel it does not rust

bull Superior tensile strength - GFRP rebar produced by the pultrusion process offers a tensile strength up to twice that of normal structural steel (based on area)

bull Thermal expansion - GFRP rebar offers a level of thermal expansion comparable to that of concrete due to its 80 silica content

bull Electric and magnetic neutrality - as GFRP rebar does not contain any metals it will not cause interference with strong magnetic fields or when operating sensitive electronic equipment or instruments

bull Thermal insulation - GFRP rebar does not create a thermal bridge within structures

bull Lightweight - GFRP rebar is a quarter the weight of steel rebar of equivalent strength It offers significant savings in transportation and installation

Figure 7 Light weight bundles of FRP are easily moved on site

Utilising these inherent benefits GFRP rebar has a cost effective application as a concrete reinforcing bar in the following markets when analysed on a life-cycle cost basis

bull Reinforced concrete exposed to corrosive environments - car parking structures bridge decks parapets curbs retaining walls foundations roads and slabs

bull Structures b uilt in or close proximity to sea water (Figures 89) - quays retaining wall piers jetties boat ramps caissons decks piles bulkheads floating structures canals roads and buildings offshore platforms swimming pools and aquanums

bull Applications subjected to other corrosive agents - wastewater treatment plants petrochemical plants pulppaper mills liquid gas plants pipelinestanks for fossil fuel cooling towers chimneys mining operations of various types nuclear power plants

2 ISIS Canada Research Network (Intelligent Sensing for Innovative Structures) was established in 1995 to provide civil engineers with smarter ways to build repair and monitor structures using high-strength rlon-corroding fibre reinforced polymers (FRPs) and fibre optic sensors (FOSs)

QUEENSLAND ROADS Edition No II September lOll 44

bull Applications rcquiring low electric conductivity or electromagnetic neutrality - aluminium and copper smelting plants manholes for electrical and telephone communication equipment bases for transmissiontelecommunication towers airport control towers MRI in hospitals railroad crossing sites and specialised military structures

bull Miningtunnelingboring applications shytemporary concrete structures mining walls underground rapid transit structures rock anchors and wash down areas

bull Weight sensitive structures - concrete construction in areas of poor load bearing soil conditions remote geographical locations sensitive environmental areas or active seismic sites posing special issues that necessitate the use of lightweight reinforcement

bull Thermally sensitive applications - apartment patio decks thermally insulated concrete housing and basements thermally heated floors and conditioning rooms

Figure 8 GFRP used on the Anthon Jetty Wyndham Western Australia

Figure 9 Precast deck slab and GFRP rebar for the Anthon Jetty

Technical case study - durability of GFRP composite rodsJ

One of the most pressing durab ility concerns of our time is the rap id corrosion of reinforcing steel that occurs in concrete structures subjected to chloride rich environments Its often argued that if the steel reinforcement in such structures could be replaced by chemically inert reinforcement such as fibre reinforced polymers the problem of cOITosion could be eliminated Of the various options the most economical choice is GFRP but it has been reported to be highly vulnerable to the alkaline environment of concrete

A report (6) summarising the results of several published studies on the alkali resistance of GFRP categorically concluded that GFRP should not be used in direct contact with concrete Similar conclusions were drawn by other researchers (789) Unfortunately all of these studies were conducted by subjecting GFRP to an idealised simulated high pH fluid environment often involving high temperatures Such environments are unduly harsh as they provide an unlimited supply of hydroxyl ions - a condition not present in rea l concrete Also they provide full saturation which is also rarely the case Field conditions should therefore be expected to be different

from these idealised laboratory conditions

3 The bulk of this section comes from a technical report as indicated under reference (5)

QUEENSLAND ROADS Edition No II September 20 11 45

Name of structure Age years

Concrete strength MPa

Seasonal temperature range middotC

Type of chloride exposure

Hall Harbor Wharf 5 45 -35 to 35 Marine

Joffre Bridge 7 45 -35 to 35 Deicing salts

Chatham Bridge 8 35 -24 to 30 Deicing salts

Crowchild Trail Bridge 8 35 -15t023 Deicing salts

Waterloo Creek Bridge 6 35 oto 23 Deicing salts

Figure 10 Samples were taken from these five structures

In 2004 a major study by ISIS Canada was launched to obtain field data with respect to the durability of GFRP in concrete exposed to natural environments Concrete cores containing GFRP were removed from five exposed structures which were five to eight years old (Figure 10) The GFRP was analysed for its physical and chemical composition at the microscopic level Direct comparisons were carried out with control samples - GFRP rods preserved under controlled laboratory conditions

At least ten 75ml11 diameter core samples containing GFRP were taken from each of the five structures Three concrete cores from each of five structures were sent for analysis to three teams of material scientists working independently at various Canadian universities The removal ofGFRP samples along with sUlTounding concrete and the polishing of the samples required special care given that GFRP and concrete have different hardness values

After sample preparation the GFRP reinforcement and surrounding concrete were analysed using several analytical methods The entire surface of each sample was examined and photographs were taken at various locations

Scanning electron microscopy (SEM) was lIsed for a detailed examination of the glass fibrematrix interface and individual glass fibres The specimens used in SEM analyses were also analysed by energy dispersive x-ray (EDX) to detect potential chemical changes in the matrix and glass fibres due to the ingress of alkali from the concrete pore solution Chemical changes in the polymeric matrix of GFRP were characterised by Fourier transfonn infrared spectroscopy (FTIR) Finally changes in the glass transition temperature Tg of the matrix due to exposure to severe environmental conditions were determined using differential scanning calorimetry (DSC)

Findings - The results obtained by the three research teams were very similar A complete account of their findings is available in their respective individual reports (10 I 112) The results found that there was no degradation of the GFRP in the samples provided The results from this scientific study based on samples from actual engineering structures was not in agreement with the results obtained in some simulated laboratory studies

The results from SEM and EDX analyses confirmed that there is no degradation of the GFRP in the concrete structures The EDX analyses also indicated no alkali ingress in the GFRP from the concrete

QUEENS LAND ROADS Edition No II Septelilber 2011 46

pore solution The matrix in all GFRPs was intact and unaltered from its original state The results from the FTIR and DSC analyses supported the results from the SEM examinations The FTIR and DSC results indicated that neither hydrolysis nor significant changes in the glass transition temperature of the matrix After exposure for 5 to 8 years to the combined effects of the alkaline environment in the concrete and the external natural environment no detrimental effects were found

The results of this study were used as the basis for changes to the Canadian Highway Bridge Design Code (13) allowing the use of GFRP both as primary reinforcement and prestressing tendons in concrete components The proviso was made that the stress level for the serviceability limit state does not exceed 25 of its ultimate tensile strength Other refenmces to the use ofGFRP can be found in (141617)

Summary and Conclusion GFRP has a very important role to playas reinforcement in concrete structures that will be exposed to harsh environmental conditions where traditional steel reinforcement could corrode It is the unique physical properties of GFRP that makes it suitable for applications where conventional steel would be unsuitable Detailed laboratory studies of samples taken from reinforced concrete structures aged from five to eight years old have confim1ed that GFRP has performed extremely well when exposed to harsh field conditions

References I Parklyn B Glass Reinforced Plastics Iliffe

London 1970

2 Phillips LN Design with Advanced Composite Materials Springer~Verlag 1989

3 ACI Committee 440 State-olthe-Art Report on Fiber Reinforced Plastic (FRP) Reinforcement for Concrete Structures American Concrete Institute 92-S61 Nov 1995 wwwconcreteorg

4 ACI Committee 440 Guidefor the Design and Construction ofStructural Concrete Reinforced with FRP bars American Concrete Institute ACI 4401 R-06 440 I 03 April 2006 wwwconcrete org

5 Mufti A Banthia N Benmokr B Boulfizaane M Newhook J Durability ofGFRP Composite Rods Concrete international Vol 29 Issue 2 February 2007

6 Malvar J Durability ofComposites in Reinforced Concrete Durability of Fiber Reinforced Polymer (FRP) Composite for Construction Proceedings of the First International Conference on Durability of Composites B Benmokrane and Rahman eds Sherbrooke QB Canada 1998

7 Uomoto r Durability ofFRP as Reinforcement for Concrete Structures Proceedings of the 3rd International Conference on Advanced Composite Materials in Bridges and Structures J Bumar and AG Razaqpur eds Canadian Society for Civil Engineering Ottawa ON Canada 2000

8 Sen Research Marsical D Issa M Shahawy M Durahili(v and Ductility ofAdvanced Composites Structural Engineering in Natural Hazards Mitigation V 2 AB-SAng and R Villaverde eds Structures Congress ASCE Irvine CA 1993

QUEENSLAND ROADS Edition No II September 20 11 47

Design standards for GFRP The design of reinforced concrete using FRP reinforcing bars is not currently codified by any Australian standard however there is a Canadian code (14) and a publication by the American Concrete Institute (4) Both of these documents use the limitshystate approach in their design

A design manual (5) has been published by thc ISIS Canada Research Network2 which describes the design process in line with the Canadian code It is patiicularly helpful as it describes the differences in design and behaviour between steel reinforced and FRP reinforced structures

The two main differences in designing reinforced concrete structures using FRP reinforcement are

bull FRP does not yield in a similar way as steel

bull FRP bars have a lower modulus of elasticity than steel Furthermore both codes do not allow for the use of FRP reinforcement as longitudinal reinforcement in columns (due to insufficient research in that area)

Benefits of GFRP The benefits ofGFRP rebar are as follows

bull Corrosion resistance - when bonded in concrete it does not react to salt chemical products or the alkali in concrete As GFRP is not manufactured from steel it does not rust

bull Superior tensile strength - GFRP rebar produced by the pultrusion process offers a tensile strength up to twice that of normal structural steel (based on area)

bull Thermal expansion - GFRP rebar offers a level of thermal expansion comparable to that of concrete due to its 80 silica content

bull Electric and magnetic neutrality - as GFRP rebar does not contain any metals it will not cause interference with strong magnetic fields or when operating sensitive electronic equipment or instruments

bull Thermal insulation - GFRP rebar does not create a thermal bridge within structures

bull Lightweight - GFRP rebar is a quarter the weight of steel rebar of equivalent strength It offers significant savings in transportation and installation

Figure 7 Light weight bundles of FRP are easily moved on site

Utilising these inherent benefits GFRP rebar has a cost effective application as a concrete reinforcing bar in the following markets when analysed on a life-cycle cost basis

bull Reinforced concrete exposed to corrosive environments - car parking structures bridge decks parapets curbs retaining walls foundations roads and slabs

bull Structures b uilt in or close proximity to sea water (Figures 89) - quays retaining wall piers jetties boat ramps caissons decks piles bulkheads floating structures canals roads and buildings offshore platforms swimming pools and aquanums

bull Applications subjected to other corrosive agents - wastewater treatment plants petrochemical plants pulppaper mills liquid gas plants pipelinestanks for fossil fuel cooling towers chimneys mining operations of various types nuclear power plants

2 ISIS Canada Research Network (Intelligent Sensing for Innovative Structures) was established in 1995 to provide civil engineers with smarter ways to build repair and monitor structures using high-strength rlon-corroding fibre reinforced polymers (FRPs) and fibre optic sensors (FOSs)

QUEENSLAND ROADS Edition No II September lOll 44

bull Applications rcquiring low electric conductivity or electromagnetic neutrality - aluminium and copper smelting plants manholes for electrical and telephone communication equipment bases for transmissiontelecommunication towers airport control towers MRI in hospitals railroad crossing sites and specialised military structures

bull Miningtunnelingboring applications shytemporary concrete structures mining walls underground rapid transit structures rock anchors and wash down areas

bull Weight sensitive structures - concrete construction in areas of poor load bearing soil conditions remote geographical locations sensitive environmental areas or active seismic sites posing special issues that necessitate the use of lightweight reinforcement

bull Thermally sensitive applications - apartment patio decks thermally insulated concrete housing and basements thermally heated floors and conditioning rooms

Figure 8 GFRP used on the Anthon Jetty Wyndham Western Australia

Figure 9 Precast deck slab and GFRP rebar for the Anthon Jetty

Technical case study - durability of GFRP composite rodsJ

One of the most pressing durab ility concerns of our time is the rap id corrosion of reinforcing steel that occurs in concrete structures subjected to chloride rich environments Its often argued that if the steel reinforcement in such structures could be replaced by chemically inert reinforcement such as fibre reinforced polymers the problem of cOITosion could be eliminated Of the various options the most economical choice is GFRP but it has been reported to be highly vulnerable to the alkaline environment of concrete

A report (6) summarising the results of several published studies on the alkali resistance of GFRP categorically concluded that GFRP should not be used in direct contact with concrete Similar conclusions were drawn by other researchers (789) Unfortunately all of these studies were conducted by subjecting GFRP to an idealised simulated high pH fluid environment often involving high temperatures Such environments are unduly harsh as they provide an unlimited supply of hydroxyl ions - a condition not present in rea l concrete Also they provide full saturation which is also rarely the case Field conditions should therefore be expected to be different

from these idealised laboratory conditions

3 The bulk of this section comes from a technical report as indicated under reference (5)

QUEENSLAND ROADS Edition No II September 20 11 45

Name of structure Age years

Concrete strength MPa

Seasonal temperature range middotC

Type of chloride exposure

Hall Harbor Wharf 5 45 -35 to 35 Marine

Joffre Bridge 7 45 -35 to 35 Deicing salts

Chatham Bridge 8 35 -24 to 30 Deicing salts

Crowchild Trail Bridge 8 35 -15t023 Deicing salts

Waterloo Creek Bridge 6 35 oto 23 Deicing salts

Figure 10 Samples were taken from these five structures

In 2004 a major study by ISIS Canada was launched to obtain field data with respect to the durability of GFRP in concrete exposed to natural environments Concrete cores containing GFRP were removed from five exposed structures which were five to eight years old (Figure 10) The GFRP was analysed for its physical and chemical composition at the microscopic level Direct comparisons were carried out with control samples - GFRP rods preserved under controlled laboratory conditions

At least ten 75ml11 diameter core samples containing GFRP were taken from each of the five structures Three concrete cores from each of five structures were sent for analysis to three teams of material scientists working independently at various Canadian universities The removal ofGFRP samples along with sUlTounding concrete and the polishing of the samples required special care given that GFRP and concrete have different hardness values

After sample preparation the GFRP reinforcement and surrounding concrete were analysed using several analytical methods The entire surface of each sample was examined and photographs were taken at various locations

Scanning electron microscopy (SEM) was lIsed for a detailed examination of the glass fibrematrix interface and individual glass fibres The specimens used in SEM analyses were also analysed by energy dispersive x-ray (EDX) to detect potential chemical changes in the matrix and glass fibres due to the ingress of alkali from the concrete pore solution Chemical changes in the polymeric matrix of GFRP were characterised by Fourier transfonn infrared spectroscopy (FTIR) Finally changes in the glass transition temperature Tg of the matrix due to exposure to severe environmental conditions were determined using differential scanning calorimetry (DSC)

Findings - The results obtained by the three research teams were very similar A complete account of their findings is available in their respective individual reports (10 I 112) The results found that there was no degradation of the GFRP in the samples provided The results from this scientific study based on samples from actual engineering structures was not in agreement with the results obtained in some simulated laboratory studies

The results from SEM and EDX analyses confirmed that there is no degradation of the GFRP in the concrete structures The EDX analyses also indicated no alkali ingress in the GFRP from the concrete

QUEENS LAND ROADS Edition No II Septelilber 2011 46

pore solution The matrix in all GFRPs was intact and unaltered from its original state The results from the FTIR and DSC analyses supported the results from the SEM examinations The FTIR and DSC results indicated that neither hydrolysis nor significant changes in the glass transition temperature of the matrix After exposure for 5 to 8 years to the combined effects of the alkaline environment in the concrete and the external natural environment no detrimental effects were found

The results of this study were used as the basis for changes to the Canadian Highway Bridge Design Code (13) allowing the use of GFRP both as primary reinforcement and prestressing tendons in concrete components The proviso was made that the stress level for the serviceability limit state does not exceed 25 of its ultimate tensile strength Other refenmces to the use ofGFRP can be found in (141617)

Summary and Conclusion GFRP has a very important role to playas reinforcement in concrete structures that will be exposed to harsh environmental conditions where traditional steel reinforcement could corrode It is the unique physical properties of GFRP that makes it suitable for applications where conventional steel would be unsuitable Detailed laboratory studies of samples taken from reinforced concrete structures aged from five to eight years old have confim1ed that GFRP has performed extremely well when exposed to harsh field conditions

References I Parklyn B Glass Reinforced Plastics Iliffe

London 1970

2 Phillips LN Design with Advanced Composite Materials Springer~Verlag 1989

3 ACI Committee 440 State-olthe-Art Report on Fiber Reinforced Plastic (FRP) Reinforcement for Concrete Structures American Concrete Institute 92-S61 Nov 1995 wwwconcreteorg

4 ACI Committee 440 Guidefor the Design and Construction ofStructural Concrete Reinforced with FRP bars American Concrete Institute ACI 4401 R-06 440 I 03 April 2006 wwwconcrete org

5 Mufti A Banthia N Benmokr B Boulfizaane M Newhook J Durability ofGFRP Composite Rods Concrete international Vol 29 Issue 2 February 2007

6 Malvar J Durability ofComposites in Reinforced Concrete Durability of Fiber Reinforced Polymer (FRP) Composite for Construction Proceedings of the First International Conference on Durability of Composites B Benmokrane and Rahman eds Sherbrooke QB Canada 1998

7 Uomoto r Durability ofFRP as Reinforcement for Concrete Structures Proceedings of the 3rd International Conference on Advanced Composite Materials in Bridges and Structures J Bumar and AG Razaqpur eds Canadian Society for Civil Engineering Ottawa ON Canada 2000

8 Sen Research Marsical D Issa M Shahawy M Durahili(v and Ductility ofAdvanced Composites Structural Engineering in Natural Hazards Mitigation V 2 AB-SAng and R Villaverde eds Structures Congress ASCE Irvine CA 1993

QUEENSLAND ROADS Edition No II September 20 11 47

bull Applications rcquiring low electric conductivity or electromagnetic neutrality - aluminium and copper smelting plants manholes for electrical and telephone communication equipment bases for transmissiontelecommunication towers airport control towers MRI in hospitals railroad crossing sites and specialised military structures

bull Miningtunnelingboring applications shytemporary concrete structures mining walls underground rapid transit structures rock anchors and wash down areas

bull Weight sensitive structures - concrete construction in areas of poor load bearing soil conditions remote geographical locations sensitive environmental areas or active seismic sites posing special issues that necessitate the use of lightweight reinforcement

bull Thermally sensitive applications - apartment patio decks thermally insulated concrete housing and basements thermally heated floors and conditioning rooms

Figure 8 GFRP used on the Anthon Jetty Wyndham Western Australia

Figure 9 Precast deck slab and GFRP rebar for the Anthon Jetty

Technical case study - durability of GFRP composite rodsJ

One of the most pressing durab ility concerns of our time is the rap id corrosion of reinforcing steel that occurs in concrete structures subjected to chloride rich environments Its often argued that if the steel reinforcement in such structures could be replaced by chemically inert reinforcement such as fibre reinforced polymers the problem of cOITosion could be eliminated Of the various options the most economical choice is GFRP but it has been reported to be highly vulnerable to the alkaline environment of concrete

A report (6) summarising the results of several published studies on the alkali resistance of GFRP categorically concluded that GFRP should not be used in direct contact with concrete Similar conclusions were drawn by other researchers (789) Unfortunately all of these studies were conducted by subjecting GFRP to an idealised simulated high pH fluid environment often involving high temperatures Such environments are unduly harsh as they provide an unlimited supply of hydroxyl ions - a condition not present in rea l concrete Also they provide full saturation which is also rarely the case Field conditions should therefore be expected to be different

from these idealised laboratory conditions

3 The bulk of this section comes from a technical report as indicated under reference (5)

QUEENSLAND ROADS Edition No II September 20 11 45

Name of structure Age years

Concrete strength MPa

Seasonal temperature range middotC

Type of chloride exposure

Hall Harbor Wharf 5 45 -35 to 35 Marine

Joffre Bridge 7 45 -35 to 35 Deicing salts

Chatham Bridge 8 35 -24 to 30 Deicing salts

Crowchild Trail Bridge 8 35 -15t023 Deicing salts

Waterloo Creek Bridge 6 35 oto 23 Deicing salts

Figure 10 Samples were taken from these five structures

In 2004 a major study by ISIS Canada was launched to obtain field data with respect to the durability of GFRP in concrete exposed to natural environments Concrete cores containing GFRP were removed from five exposed structures which were five to eight years old (Figure 10) The GFRP was analysed for its physical and chemical composition at the microscopic level Direct comparisons were carried out with control samples - GFRP rods preserved under controlled laboratory conditions

At least ten 75ml11 diameter core samples containing GFRP were taken from each of the five structures Three concrete cores from each of five structures were sent for analysis to three teams of material scientists working independently at various Canadian universities The removal ofGFRP samples along with sUlTounding concrete and the polishing of the samples required special care given that GFRP and concrete have different hardness values

After sample preparation the GFRP reinforcement and surrounding concrete were analysed using several analytical methods The entire surface of each sample was examined and photographs were taken at various locations

Scanning electron microscopy (SEM) was lIsed for a detailed examination of the glass fibrematrix interface and individual glass fibres The specimens used in SEM analyses were also analysed by energy dispersive x-ray (EDX) to detect potential chemical changes in the matrix and glass fibres due to the ingress of alkali from the concrete pore solution Chemical changes in the polymeric matrix of GFRP were characterised by Fourier transfonn infrared spectroscopy (FTIR) Finally changes in the glass transition temperature Tg of the matrix due to exposure to severe environmental conditions were determined using differential scanning calorimetry (DSC)

Findings - The results obtained by the three research teams were very similar A complete account of their findings is available in their respective individual reports (10 I 112) The results found that there was no degradation of the GFRP in the samples provided The results from this scientific study based on samples from actual engineering structures was not in agreement with the results obtained in some simulated laboratory studies

The results from SEM and EDX analyses confirmed that there is no degradation of the GFRP in the concrete structures The EDX analyses also indicated no alkali ingress in the GFRP from the concrete

QUEENS LAND ROADS Edition No II Septelilber 2011 46

pore solution The matrix in all GFRPs was intact and unaltered from its original state The results from the FTIR and DSC analyses supported the results from the SEM examinations The FTIR and DSC results indicated that neither hydrolysis nor significant changes in the glass transition temperature of the matrix After exposure for 5 to 8 years to the combined effects of the alkaline environment in the concrete and the external natural environment no detrimental effects were found

The results of this study were used as the basis for changes to the Canadian Highway Bridge Design Code (13) allowing the use of GFRP both as primary reinforcement and prestressing tendons in concrete components The proviso was made that the stress level for the serviceability limit state does not exceed 25 of its ultimate tensile strength Other refenmces to the use ofGFRP can be found in (141617)

Summary and Conclusion GFRP has a very important role to playas reinforcement in concrete structures that will be exposed to harsh environmental conditions where traditional steel reinforcement could corrode It is the unique physical properties of GFRP that makes it suitable for applications where conventional steel would be unsuitable Detailed laboratory studies of samples taken from reinforced concrete structures aged from five to eight years old have confim1ed that GFRP has performed extremely well when exposed to harsh field conditions

References I Parklyn B Glass Reinforced Plastics Iliffe

London 1970

2 Phillips LN Design with Advanced Composite Materials Springer~Verlag 1989

3 ACI Committee 440 State-olthe-Art Report on Fiber Reinforced Plastic (FRP) Reinforcement for Concrete Structures American Concrete Institute 92-S61 Nov 1995 wwwconcreteorg

4 ACI Committee 440 Guidefor the Design and Construction ofStructural Concrete Reinforced with FRP bars American Concrete Institute ACI 4401 R-06 440 I 03 April 2006 wwwconcrete org

5 Mufti A Banthia N Benmokr B Boulfizaane M Newhook J Durability ofGFRP Composite Rods Concrete international Vol 29 Issue 2 February 2007

6 Malvar J Durability ofComposites in Reinforced Concrete Durability of Fiber Reinforced Polymer (FRP) Composite for Construction Proceedings of the First International Conference on Durability of Composites B Benmokrane and Rahman eds Sherbrooke QB Canada 1998

7 Uomoto r Durability ofFRP as Reinforcement for Concrete Structures Proceedings of the 3rd International Conference on Advanced Composite Materials in Bridges and Structures J Bumar and AG Razaqpur eds Canadian Society for Civil Engineering Ottawa ON Canada 2000

8 Sen Research Marsical D Issa M Shahawy M Durahili(v and Ductility ofAdvanced Composites Structural Engineering in Natural Hazards Mitigation V 2 AB-SAng and R Villaverde eds Structures Congress ASCE Irvine CA 1993

QUEENSLAND ROADS Edition No II September 20 11 47

Name of structure Age years

Concrete strength MPa

Seasonal temperature range middotC

Type of chloride exposure

Hall Harbor Wharf 5 45 -35 to 35 Marine

Joffre Bridge 7 45 -35 to 35 Deicing salts

Chatham Bridge 8 35 -24 to 30 Deicing salts

Crowchild Trail Bridge 8 35 -15t023 Deicing salts

Waterloo Creek Bridge 6 35 oto 23 Deicing salts

Figure 10 Samples were taken from these five structures

In 2004 a major study by ISIS Canada was launched to obtain field data with respect to the durability of GFRP in concrete exposed to natural environments Concrete cores containing GFRP were removed from five exposed structures which were five to eight years old (Figure 10) The GFRP was analysed for its physical and chemical composition at the microscopic level Direct comparisons were carried out with control samples - GFRP rods preserved under controlled laboratory conditions

At least ten 75ml11 diameter core samples containing GFRP were taken from each of the five structures Three concrete cores from each of five structures were sent for analysis to three teams of material scientists working independently at various Canadian universities The removal ofGFRP samples along with sUlTounding concrete and the polishing of the samples required special care given that GFRP and concrete have different hardness values

After sample preparation the GFRP reinforcement and surrounding concrete were analysed using several analytical methods The entire surface of each sample was examined and photographs were taken at various locations

Scanning electron microscopy (SEM) was lIsed for a detailed examination of the glass fibrematrix interface and individual glass fibres The specimens used in SEM analyses were also analysed by energy dispersive x-ray (EDX) to detect potential chemical changes in the matrix and glass fibres due to the ingress of alkali from the concrete pore solution Chemical changes in the polymeric matrix of GFRP were characterised by Fourier transfonn infrared spectroscopy (FTIR) Finally changes in the glass transition temperature Tg of the matrix due to exposure to severe environmental conditions were determined using differential scanning calorimetry (DSC)

Findings - The results obtained by the three research teams were very similar A complete account of their findings is available in their respective individual reports (10 I 112) The results found that there was no degradation of the GFRP in the samples provided The results from this scientific study based on samples from actual engineering structures was not in agreement with the results obtained in some simulated laboratory studies

The results from SEM and EDX analyses confirmed that there is no degradation of the GFRP in the concrete structures The EDX analyses also indicated no alkali ingress in the GFRP from the concrete

QUEENS LAND ROADS Edition No II Septelilber 2011 46

pore solution The matrix in all GFRPs was intact and unaltered from its original state The results from the FTIR and DSC analyses supported the results from the SEM examinations The FTIR and DSC results indicated that neither hydrolysis nor significant changes in the glass transition temperature of the matrix After exposure for 5 to 8 years to the combined effects of the alkaline environment in the concrete and the external natural environment no detrimental effects were found

The results of this study were used as the basis for changes to the Canadian Highway Bridge Design Code (13) allowing the use of GFRP both as primary reinforcement and prestressing tendons in concrete components The proviso was made that the stress level for the serviceability limit state does not exceed 25 of its ultimate tensile strength Other refenmces to the use ofGFRP can be found in (141617)

Summary and Conclusion GFRP has a very important role to playas reinforcement in concrete structures that will be exposed to harsh environmental conditions where traditional steel reinforcement could corrode It is the unique physical properties of GFRP that makes it suitable for applications where conventional steel would be unsuitable Detailed laboratory studies of samples taken from reinforced concrete structures aged from five to eight years old have confim1ed that GFRP has performed extremely well when exposed to harsh field conditions

References I Parklyn B Glass Reinforced Plastics Iliffe

London 1970

2 Phillips LN Design with Advanced Composite Materials Springer~Verlag 1989

3 ACI Committee 440 State-olthe-Art Report on Fiber Reinforced Plastic (FRP) Reinforcement for Concrete Structures American Concrete Institute 92-S61 Nov 1995 wwwconcreteorg

4 ACI Committee 440 Guidefor the Design and Construction ofStructural Concrete Reinforced with FRP bars American Concrete Institute ACI 4401 R-06 440 I 03 April 2006 wwwconcrete org

5 Mufti A Banthia N Benmokr B Boulfizaane M Newhook J Durability ofGFRP Composite Rods Concrete international Vol 29 Issue 2 February 2007

6 Malvar J Durability ofComposites in Reinforced Concrete Durability of Fiber Reinforced Polymer (FRP) Composite for Construction Proceedings of the First International Conference on Durability of Composites B Benmokrane and Rahman eds Sherbrooke QB Canada 1998

7 Uomoto r Durability ofFRP as Reinforcement for Concrete Structures Proceedings of the 3rd International Conference on Advanced Composite Materials in Bridges and Structures J Bumar and AG Razaqpur eds Canadian Society for Civil Engineering Ottawa ON Canada 2000

8 Sen Research Marsical D Issa M Shahawy M Durahili(v and Ductility ofAdvanced Composites Structural Engineering in Natural Hazards Mitigation V 2 AB-SAng and R Villaverde eds Structures Congress ASCE Irvine CA 1993

QUEENSLAND ROADS Edition No II September 20 11 47

pore solution The matrix in all GFRPs was intact and unaltered from its original state The results from the FTIR and DSC analyses supported the results from the SEM examinations The FTIR and DSC results indicated that neither hydrolysis nor significant changes in the glass transition temperature of the matrix After exposure for 5 to 8 years to the combined effects of the alkaline environment in the concrete and the external natural environment no detrimental effects were found

The results of this study were used as the basis for changes to the Canadian Highway Bridge Design Code (13) allowing the use of GFRP both as primary reinforcement and prestressing tendons in concrete components The proviso was made that the stress level for the serviceability limit state does not exceed 25 of its ultimate tensile strength Other refenmces to the use ofGFRP can be found in (141617)

Summary and Conclusion GFRP has a very important role to playas reinforcement in concrete structures that will be exposed to harsh environmental conditions where traditional steel reinforcement could corrode It is the unique physical properties of GFRP that makes it suitable for applications where conventional steel would be unsuitable Detailed laboratory studies of samples taken from reinforced concrete structures aged from five to eight years old have confim1ed that GFRP has performed extremely well when exposed to harsh field conditions

References I Parklyn B Glass Reinforced Plastics Iliffe

London 1970

2 Phillips LN Design with Advanced Composite Materials Springer~Verlag 1989

3 ACI Committee 440 State-olthe-Art Report on Fiber Reinforced Plastic (FRP) Reinforcement for Concrete Structures American Concrete Institute 92-S61 Nov 1995 wwwconcreteorg

4 ACI Committee 440 Guidefor the Design and Construction ofStructural Concrete Reinforced with FRP bars American Concrete Institute ACI 4401 R-06 440 I 03 April 2006 wwwconcrete org

5 Mufti A Banthia N Benmokr B Boulfizaane M Newhook J Durability ofGFRP Composite Rods Concrete international Vol 29 Issue 2 February 2007

6 Malvar J Durability ofComposites in Reinforced Concrete Durability of Fiber Reinforced Polymer (FRP) Composite for Construction Proceedings of the First International Conference on Durability of Composites B Benmokrane and Rahman eds Sherbrooke QB Canada 1998

7 Uomoto r Durability ofFRP as Reinforcement for Concrete Structures Proceedings of the 3rd International Conference on Advanced Composite Materials in Bridges and Structures J Bumar and AG Razaqpur eds Canadian Society for Civil Engineering Ottawa ON Canada 2000

8 Sen Research Marsical D Issa M Shahawy M Durahili(v and Ductility ofAdvanced Composites Structural Engineering in Natural Hazards Mitigation V 2 AB-SAng and R Villaverde eds Structures Congress ASCE Irvine CA 1993

QUEENSLAND ROADS Edition No II September 20 11 47

9 Sen Research Mullins G Salem T Durability ofE-Glassl Vinylester Reinforcement in Alkaline Solution ACI Structural Journal V 99 No3 May-June 2002

10 Benmokrane B Cousin P University of Sherbrooke GFRP D1Irability Study Report ISIS Canada University of Manitoba Winnipeg MB Canada 2005

11 Boulfiza M Banthia N University of Saskatchewan amp University of British Columbia Durability Study Report ISIS Canada University of Manitoba Winnipeg MB Canada 2005

12 Onofrei M Durability ofGFRP Reinforced Concrete from Field Demonstration Structures ISIS Canada University of Manitoba Winnipeg MB Canada 2005

13 CANCSA-S6-06 Canadian Highway Bridge Code December 2008 http wwwShopCSAca

14 CANCSA-S806-02 Constmction ofBuilding Components vith Fibre-Reinforced Polymers Product Number 2012972 2007 http www ShopCSAca

15 Rizkalla S Mufti A Manual No3 - Reinforcing Concrete Structures with Fibre Reinforced Polymers (FRPs) ISIS Canada Research Network httpisiscanadacom

16 Various American Concrete Institute Committee 440 reports http wwwconcreteorg COMMITTEEScommitteehomeaspcommittee_ code=0000440-00

17 AASHTO LRFD Bridge Design Guide Specifications for GFRP-Reinjorced Concrete Bridge Decks and Traffic Railings GFRP-l ISBN 1-56051-458-9 2009 https lbookstore transportationorgltem _detailsaspxid= 1545

QUEENSLAND ROADS Edition No II September 2011 48