Demonstrating steel fibres from waste tyres as reinforcement i

Demonstrating Steel Fibres from Waste Tyres as Reinforcement in Concrete: Material Considerations

Demonstrating Steel Fibres from Waste Tlemat, Pilakoutas and Neocleous Tyres as Reinforcement in Concrete: Material Characterisation Houssam Tlemat Research scholar

Kypros Pilakoutas Professor of Construction Innovation

Kyriacos Neocleous Marie-Curie Post-doctoral Research Fellow Centre for Cement and Concrete, Department of Civil and Structural Engineering, The University of Sheffield, UK http:/www.shef.ac.uk/tyre-recycling

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Demonstrating Steel Fibres from Waste Tyres as Reinforcement in Concrete: Material Considerations Tlemat, Pilakoutas and Neocleous

Outline Waste Tyre Recycling Recycled Steel Fibres Pull-out Tests Flexural Tests Conclusions

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Waste Tyre Recycling • International Problem:

EU Average Tyre Statistics 2002

1 billion annual arisings worldwide Quarter of this amount arises in EU • EU directives driving force for waste management

Landfill, stockpile 34%

• Landfill directive prohibits disposal of tyre by-products by 2006 • Develop new markets to avoid disposal

Energy recovery 22%

Export, reuse 11% Retreading 12%

Material recovery 21%

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Material Recovery:

Waste Tyre Recycling

• Mechanical processes (e.g. tyre shredding) reduces tyres to steel fibres & granulated rubber

• Thermal degradation processes (e.g. microwave induced pyrolysis) breaks down tyres into steel, char, liquids and gases AMAT LTD™

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Patent Applied For

The University of Sheffield has filed a patent application for the Use of Tyre Fibres in Concrete.

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Examined Fibres Pyrolysed Recycled Steel Fibre (PRSF) • Clean from rubber • Tensile properties not affected (1250 MPa) • Fibres contain carbon black on surface • Fibre not so easy to cut 12 wires (φ0.23mm) twisted to a core strand (φ0.85mm), surrounded with another 15 twisted wires. On the surface there is a twisted single wire. Overall external diameter: 1.55 mm Effective diameter: 1.16 mm 6


Examined Fibres Shredded Recycled Steel Fibre (SRSF) • Fibres contain small amounts rubber and fluff • Long bid wires need to be removed (sieving) • Fibres are magnetised

• Fibres tend to ball-up • Inconsistent size and shape • Diameter ~ 0.23mm 7


Examined Fibres Industrially Available Steel Fibre (ISF) • Fibre industrially produced from wire with flattened ends • Fibre is rigid • Diameter: 1mm • Tensile Strength: 1150 MPa

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Pull-out Tests Why ?

• Useful to understand fibre bond characteristics • Determination of the critical fibre length

Problems: • Not always easy to perform on fibres (high accuracy required for very small displacement and load) • No standard method • A suitable test must be developed for each fibre 9


Double-sided Pull-out Tests • Specimen Preparation: Lemb

Perspex plate with ISF

10mm plastic tubes filled with silicon were used

Nominal size 100x100x80 mm

Casting done in two stages

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Double-sided Pull-out Tests • Specimen Preparation: Perspex plate

LVDT

Applied Load

Concrete specimen

Fixed part

Tested fibre

Steel clamps are fixed at the end of each specimen. Deformation is measured over a gauge length of 50mm using two transducers. 11


Double-sided Pull-out Tests • Test set-up

1

2 3

4 5

6

7

8

1.

5 kN strain gauged spring beam

2.

Chuck attached the clamp with a pin

3.

Fixed metal clamp pinned on the chuck

4.

Perspex plate with the fibre through its central holes placed in middle of specimen

5.

230 volt Single Phase Motor fitted with 3step pulley drives the cross-head at a speed of 1.5 mm/min

6.

Pulled part of the specimen

7.

Cross-head attached to motor

8.

Manual handles 12


Double-sided Pull-out Tests Test Results for PRSF and ISF fibres (10 mm embedment length) 0.4 C2

C1

l = 10mm

LOAD [kN]

0.3 B1

• PRSF fibre has better bond at the initial stages

B2

PRSF

0.2

ISF 0.1

• Bond resistance of ISF provided by end anchorage

D2 D1

A 0 0

2

4

6

8

10

SLIP [mm]

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Double-sided Pull-out Tests Effect of aspect ratio - PRSF and ISF fibres

TENSILE STRES [MPa]

1-ISF

average of 3-PRSF

1-PRSF

1-PRSF with end anchoring

1600 1200

• Peak tensile stress increases linearly with the aspect ratio • Better behaviour for PRSF with end anchoring

800 400 0 0

5

10

15

20

ASPECT RATIO l/d

25

30

• Critical length: more than 60mm PRSF, but for practical reasons, 50 mm recommended

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Double-sided Pull-out Tests Test results for shredded fibres 10 mm

20 mm

• The tested 0.23mm diameter shredded fibres are very fragile

30 mm

100

• Only fibres with 10mm embedment length pulled out during loading

LOAD [N]

80 60 40 20 0 0

2

4

6

SLIP [mm]

8

10

12

• All fibres with 20mm and 30mm embedded length fractured during loading

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Flexural Toughness Tests

Why ?

• Examine the toughness and energy absorption capacity of steel fibre reinforced concrete • Determination of design parameters

Problems: • Results prone to experimental errors • Variety of testing methods

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Specimen preparation:

• Accurate deflection measurement – using a yoke • 150 x 150 x 550 mm specimens • Crack inducer: 25 x 4mm notch at mid-span • Four point loading – 100 kN servo-hydraulic machine – crack mouth opening displacement

Aluminium bar

LVDT on each side

LVDT Pins 17


Flexural Toughness Tests • Effect of fibre volume (average of 3 tests)

Average load [kN]

70 60

PRSF 1.5%

50

PRSF 3% PRSF 6%

40

SRSF 0.5%

30 SRSF 1%

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Peak load and residual strength after cracking increase with fibre volume.

SRSF 2%

10

ISF-1 6%

0 0

1

2

3

Average mid-span deflection [mm]

4 18



Effect of fibre type: (average of 3 tests) SRSF 2% PRSF 6% ISF 6%

80 60 50

30

40

PRSF 1.5%

25

30

SRSF 2% Load [kN]

LOAD [kN]

70

20 10 0 0

0.5

1 1.5 2 DEFLECTION [mm]

2.5

• Response just after peak load is stable for PRSF and ISF fibres

20 15 10

3 5 0 0

1

2 Deflection [kN]

3

• PRSF is comparable to ISF 19


Conclusions •

Tensile strength of tested fibres is influenced by the pull-out test method used

•

Double-sided pull out tests eliminate measurement errors

•

If possible, PRSF should be provided with end anchorage

•

PRSF has stiffer initial bond-slip characteristics than the ISF fibre

•

An increase in fibre volume increases the flexural toughness significantly

•

PRSF and ISF exhibit good energy absorption capacity

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Acknowledgements

UK’s Department of Trade and Industry

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