comparative performance of frp & frcm systems at …

COMPARATIVEPERFORMANCE OF FRP &FRCM SYSTEMS ATELEVATED TEMPERATUREDr Luke Bisby, Reader

BRE Centre for Fire Safety EngineeringSchool of Engineering, University of Edinburgh, UK

Introduction• Externally-Bonded FRP Strengthening Systems

– Widely accepted, method of choice, polymer-based (concerns infire)

• Textile Reinforced Mortar (TRM) Strengthening Systems:– Emerged in last 5-10 years– Repairing damaged or deficient concrete or masonry (axial, shear,

flexure)– Open-weave carbon fibre fabrics applied using inorganic mortars– Comparatively low strength, stiffness, adhesion properties

• Fibre Reinforced Cementitious Matrix (FRCM) Systems:– Emerged in last 5 years– Non-woven PBO fibre grids applied using

modified inorganic mortars– Repairing damaged or deficient concrete– Superior strength, stiffness, adhesion

Ruredil X Mesh GoldTM

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Research Motivation• Thermal & mechanical performance

in fire– A key issue in the application of any

structural strengthening system

• Fire-rated, insulated externallybonded FRP strengthening systemsare available– Current design guidance ignores the

FRP during fire (even with insulation)– Ability of FRP strengthening systems to

maintain structural effectiveness underload at high temperature remainsunproven

– Applications of FRPs are hindered

• It has been suggested thatTRM/FRCM systems mayoutperform FRP systems during fireor in elevated temperature serviceenvironments

www.ruredil.it

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Background• FRCM:

– Advantages over externally bondedFRP systems:

• Installation and aesthetics• Breathability• Non-combustibility, zero flame spread• Mechanical performance at high

temperature?

• Current presentation:– Pilot study into comparative performance of FRCM

systems– Tests at ambient & elevated temperatures– Comparison against externally-bonded

carbon/epoxy FRP strengthening systems

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QUESTION: How does FRCM compare withFRP?

OBJECTIVES:

1. Experimentally investigate the performance of FRCMflexural strengthening systems for reinforced concretestructures

– In comparison with externally-bonded FRP systems– In bond-critical applications without supplemental anchors– At temperatures that they might experience if insulated and

exposed to a standard fire scenario, or in elevatedtemperature service environments

2. Investigate the hypothesis that FRCM systems mayprovide superior retention of mechanical propertiesat elevated temperature as compared with externally-bonded FRP

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Experimental Programme

• 36 notched beam bond tests

• Three strengthening systems:– FRCM system– FRP 1 system from an Italian supplier– FRP 2 system from a global FRP supplier

• Three test temperatures (tested @ hightemperature):– 20°C– 50°C– 80°C

• All tests performed in triplicate

6 hours pre-conditioning prior to testing

0

10

20

30

40

50

60

70

80

90

0 60 120 180 240 300 360 420Time (minutes)

Tem

pera

ture

(deg

. C)

80 deg. C

50 deg. C

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Beam Specimens

Strengthening system

Notch

400

600

36

A

A

80

150

18

150

100

1 layer FRP 2 layers FRCM

Bond breaker18

100

U-wraps for shearstrengthening

U-wraps for shearstrengthening

200 50

SIDE ELEVATION

FRP STRENGTHENED SECTION A-A FRCM STRENGTHENED SECTION A-A

* All dimensions in mm

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Shear Strengthening Scheme• Pilot tests demonstrated shear failures• Remedial shear strengthening was required

– Inverted U-wraps– shear strengthening without supplemental anchorage– Does not significantly affect the flexural strengthening

Strengthening system

400 100100

Major shear crack

FRP strengthening systemNo. 1

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Testing Matrix

3X Mesh M750X MeshGold

--FRCM 80

3Saturant Nº22Carbonfibre3

Primer Nº22FRP Nº2 80



3

680------PC 80


--FRCM 50





3

650------PC 50


--FRCM 20





3

--20------PC 20

No. ofbeams

Durationof

heating(hrs)

Targettest

temp.(°C)

Adhesivesystem

FibresystemPrimerSpecimen

ID

1 Commercially available epoxy primer and saturant system currently selling in Italy.2 Commercially available epoxy primer and saturant system currently selling globally.3 Commercially available unidirectional carbon fibre fabric currently selling in Italy.

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FRCM Installation

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Testing Methodology

Applied load

Linearpotentiometer

200 10050

Pin

ConcretebeamThermocouple

Reaction beam

50200

Strengthening systemgeoPIV region

11

0

5

10

15

20

25

30

0 1 2 3 4 5Crosshead displacement (mm)

Load

(kN

)

FRP No2 20RC 20FRCM 20FRP No1 20

Load vs. Displacement: Tests @20°C

Shear Failure

Flexural Failure

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Failure Modes: 20°CUnstrengthened

FRP 1 strengthened

FRP 2 strengthened

Flexural failure

Shear failure

Shear Failure

Painted texture for digital image analysis

FRCM strengthened

Shear Failure

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0

5

10

15

20

25

30

0 1 2 3 4 5

Crosshead Displacement (mm)

Load

(kN

)

FRCM 50FRP No1 50FRP No2 50RC 50

Shear Failure

Flexural Failure

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FRP 1 strengthened

FRP 2 strengthened

Flexural failure

Flexural / bond failure

Shear Failure

FRCM strengthened

Shear Failure

15


0

5

10

15

20

25

30

0 1 2 3 4 5

Crosshead Displacement (mm)

Load

(kN

)

FRCM 80FRP No2 80RC 80FRP No1 80

Shear Failure

Flexural Failure

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FRP 1 strengthened

FRP 2 strengthened

Flexural failure

Flexural / bond failure

Flexural / bond Failure

FRCM strengthened

Shear Failure

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Effect of Temperature

0.0

0.2

0.4

0.6

0.8

1.0

1.2

10 20 30 40 50 60 70 80 90

Temperature (deg. Celsius)

Nor

mal

ized

Fai

lure

Loa

d

FRCMFRP No1FRP No 2

Shear failure in concrete

Debonding failure of strengthening

Strength reduction of FRCM beams may be due to reductionsin shear strength of concrete at 80°C, rather than indicating

damage to the FRCM

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Aside: Characterization of EpoxyResins

• DMTA testing on polymer primer & saturants

0.000E+00

5.000E+08

1.000E+09

1.500E+09

20.0 50.0 80.0

Temperature (deg. C)

Mod

ulus

(Pa)

FRP No 1 Primer

FRP No 1 SaturantFRP No 2 PrimerFRP No 2 Saturant

Stiffness required toprevent bond failure

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Conclusions1. The FRCM system can be effectively used, without

supplemental anchorage, to strengthen RC beams inbending

2. Effects of Temperature:– FRP Nº1 experienced reductions of 52% at 50°C and 74% at

80°C– FRP Nº2 experienced reductions of 10% at 50°C and 64% at

80°C– FRCM experienced reductions of only 6% at 50°C and 28% at

80°C• May represent a reduction in the strength of the concrete rather

than damage to the FRCM system

3. FRCM appears to be a superior candidate for use instrengthening applications at temperatures of 25°C to80°C

4. FRCM’s inherent non-combustibility and superiorperformance at temperatures up to 80°C make it anattractive system for structural strengthening(particularly in buildings)

20

Acknowledgements

The OveArupFoundation

Thank you for your attentionFor additional information email: [email protected]

Dr T Stratford, J Smith, SHalpinUniversity of Edinburgh

Ruredil SPA,Milano, Italy

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Aside: Flame Spread &Combustibility

• FRP systems:– Loss of the strengthening systems’ mechanical performance during

fire may not be critical if reasonable strengthening limits are imposed

• Structural performance is only one of many concerns infire:– Fire severity and fuel load– Flame spread– Smoke generation and toxicity

• FRP strengthening systems often require flame spreadcoatings in interior applications to meet life-safetyobjectives in fire

• FRCM systems bonded with inorganic mortars:– Inherently non-combustible– Can be used unprotected– Reductions in material and installation costs– Improved aesthetics

Aside: Aging of Polymer Resins?

• DMTA testing after 3 hrs at high temperature

0.000E+00

5.000E+08

1.000E+09

1.500E+09

2.000E+09

20 50 80Temperature ( oC)

Mod

ulus

(Pa)

FRP1 PrimerFRP1 Saturant

FRP No1 FRP No2

comparative performance of frp & frcm systems at …

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