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INTERNATIONAL CONFERENCE

BEFIB200420-22 September 2004

Lecco, Italy

Slurry Infiltrated Shredded Fibre Reinforced Concrete (SIScon) for Pre-cast Applications

ByHoussam TlematResearch scholar

Kypros PilakoutasProfessor of Construction Innovation

Kyriacos NeocleousMarie-Curie Post-doctoral Research Fellow

Centre for Cement and Concrete at the Department of Civil & Structural Engineering of the University of Sheffield

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Introduction

Fibres from Recycled Waste Tyres

Example of Pre-cast Application

Testing Procedure

Comparison with Rcon and Pcon

Results and Conclusions

SLURRY INFILTRATED SHREDDED FIBRE REINFORCED CONCRETE (SIScon) FOR PRE-CAST APPLICATIONS

Tlemat, H., Pilakoutas, K. and Neocleous, K.

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Waste Tyres• International Problem• 400 k tonnes used tyres/year in UK • > 160 k tonnes go to landfill• > 60 k (100) tonnes of steel fibre

Waste shredded fibres



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Reduction Processes

European Union Landfill

directive which stopped the

disposal of whole tyres to

landfills (July 2003), will

prohibit the disposal of the tyre

by-products by 2006

• SHREDDING

• MECHANICAL

• PYROLYSIS

• MICROWAVE

• CRYOGENIC

• CHEMICAL



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Reduction Processes



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• Fibres contain small amounts of rubber and fluff

• Fibres are magnetised

• Fibres tend to ball-up

Fibre from the third shredding process (SRSF)

Fibres used in experimentsFibre from the second shredding process (SRSF)

Un-sieved Fibres Sieved Fibres



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Pyrolysed Recycled Steel Fibre (PRSF)

• Clean from rubber

• Tensile properties not affected

• Fibres from PRSF process contain carbon black on surface

• Fibre not so easy to cut

Fibres used in experiments



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Pre-cast Concrete• Toughness/impact resistance

• Crack Control• Strength?

• Weight Coatings• Inner tunnel linings• Tunnel segments• Manholes/access shafts• Standard units• Pipes• Permanent formwork



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Decathlon system drainage cover slabSlab Dimension

Most common applications are in the road carriageway, hard shoulder and parking areas



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Decathlon system drainage cover slabSlab Description-Rcon Slabs

The slab is normally reinforced in the bottom with nine ordinary steel bars 12 mm in diameter to satisfy the EN 124 (1994) loading condition C250

Ready mixed concrete was cast in the steel mould by Hdkin and Jones Ltd



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Decathlon system drainage cover slab

Slab test programme

Objective: Replace conventional reinforcement with steel fibres extracted from waste tyres

Mix code Test type Concrete type Reinforcement type

Fibre content (% by weight)

Rcon Two Slabs OPC 40 conventional - Pcon Two slabs, prisms and cubes SP 40/30 PRSF 6% Scon Slab, prisms and cubes SP 40/30 Sieved SRSF 2% SIScon Slab, prisms and cubes Slurry SRSF 17.5%



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Decathlon system drainage cover slabSlab Description-SIScon Slab

Un-sieved shredded fibre from the third shredding process was simply placed in up to the top of the mould

specimens were cast by pouring the slurry from the specimens top. The specimens were vibrated during casting to ensure a good penetration of the slurry



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Decathlon system drainage cover slabSlab Description - Pcon

Pylolysed fibre was used fro different tyres – 50mm length – diameter in the range of 0.8-1.5 mm

•12 wires Ø 0.23mm twisted to a core strand of Ø 0.85 mm surrounded with another 15 twisted wires. On the surface there is a twisted single wire.

•Overall external diameter is 1.55 mm

•Effective diameter 1.16 mm. Tensile strength 1250 MPa



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Decathlon system drainage cover slabSlab Description-Scon Slabs

Only the fibre from the third shredding process, that passed through the 8.0 mm sieve and that remained in the 6.3mm sieve was used – Average diameter around 0.23mm



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Decathlon system drainage cover slabResults and DiscussionCompressive test results

The compressive test of the SIScon cube indicated an extremely high ductility due to the high fibre content and very good bond between shredded fibre and cement paste.

Mixes Cube strength [N/mm2] Slump (day of test) (28 d) [mm]

OPC40 (Rcon slab) 47.0(40d) 45.0 80 SP 40/30 (Control specimen, Pcon slab) - 59.0 200 Pcon (6% pyrolysed fibres, Pcon slab) 46.8 (19d) 54.4 110 SP 40/30 (Control specimen, Scon slab) - 43.6 180 Scon (2% shredded fibres, Scon slab) 35.9 (19d) 45.3 60 SIScon (17.5% shredded fibres) 52.8 (17d) 54.2 -



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Decathlon system drainage cover slabTesting Procedure

• Simply supported on two opposite steel beams. To avoid stress concentrations within the support, a 5mm thick dental plaster was placed on a plywood base.

• Single point loading acting on a Ø 250mm steel plate in a 500 kN displacement controlled scew -jack machine was used

• Slab deflections and crack opening were measured using LVDTs; One was fixed underneath in the centre of the slab, two in the support edge, two in the corner and two on the side

• To record the initial hysteresis loops and stabilise the slab, each slab was subjected to five load cycles up to 2/3 of the design load at a rate of up to 5 kN/s



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Decathlon system drainage cover slabResults and DiscussionBehaviour of SIScon slab – Initial deflection

Slurry Infiltrated Shredded Fibre Reinforced Concrete Slab (SIScon)

0

50

100

150

200

250

300

350

-8 -6 -4 -2 0 2 4 6 8 10Deflection [mm]

Load

[kN]

4 & 6 7 & 8 3 2 & 5

The central stiffer part of the slab is not as deformable, hence the centre of the slab, initially deforms less than its central support

The support is deforming as if on an elastic foundation.



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Decathlon system drainage cover slabResults and DiscussionBehaviour of SIScon slab – load versus slab deflection

Slurry Infiltrated Shredded Fibre Reinforced Concrete Slab (SIScon)

0

50

100

150

200

250

300

350

-2 -1 0 1 2 3 4 5 6 7 8 9Deflection [mm]

Load

[kN

]

Peak load/Crack w idth297.8 / 0.41

Load at BOP/Crack w idth196.8 / 6e-3

BOP

Crack Opening [mm]

Load at 0.02mm(2224 kN)

-The shape of the initial curve is influenced by high initial deflection of the support

- The transition from the uncracked behaviour is very gentle. This indicate a favourable crack development and good anchoring of the fibres

- The load at first crack is highest of all slabs investigated



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Decathlon system drainage cover slabResults and DiscussionBehaviour of SIScon slab – failure

- The slab cracked in to parts along the edge of the ribs

- The slab collapsed at peak load of 297 kN



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Decathlon system drainage cover slabResults and DiscussionBehaviour of Rcon slab – absolute load-displacement and slab failure -

Conventional Reinfoced Concrete Slab (RC2)

0

50

100

150

200

250

300

0 1 2 3 4 5 6 7 8 9

Deflection [mm]

Load

[kN

]

First-crack load/defl93.5 kN / 0.29 mm

Peak load/deflection253.1 kN / 5.68 mm

Region II

Region I

Region III

Fu

F`r

Fr BOP

U

Region 1: Elastic behaviour

Region II: Elastic plastic behaviour. The cracks propagated from the applied load to the boundary of the slab

Region III: The radial cracks increased in length until a yield pattern was formed. Final failure due to the punching shear



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Decathlon system drainage cover slabResults and DiscussionBehaviour of Pcon slab – relative load-displacement and slab failure -

- The slab cracked in two parts along the edge of the ribs

- The location of the crack confirms that many of the fibres did not penetrate in the narrow gaps of the diagonal slots.

-The fibre were well anchored since there was a lot of residual strength at post peak load

- Slab did not make the c250 class, it passes the B125

AMAT Fibre Reinforced Concrete Slab (AMATcon)

0

40

80

120

160

200

-1 0 1 2 3 4 5 6 7 8

Deflection [mm]

Load

[kN]

Load at BOP / Crack w idtht 103 kN / 0.7e-2 mm

Peak load / Crack w idth170 kN / 1.5 mm

Load at crack-w idth 0.02mm

(135 kN)

BOP

U

0

50

100

150

-0.1-0.050Crack opening [mm]

Load

[kN

]



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Decathlon system drainage cover slabResults and DiscussionBehaviour of Scon slab – relative load-displacement and slab failure -

Shredded Fibre Reinforced Concrete Slab (Scon)

0

20

40

60

80

100

120

140

160

-1 0 1 2 3 4 5 6 7 8

Deflection [mm]

Load

[kN]

Load at BOP/crack w idth107 kN / 2e-4 mm

Crack opening [mm]

Load at 0.02mm(112.9 kN)

Peak load/crack w idth141 kN / 0.71 mm

BOP

-The slab was tested successfully for the class B125 loading condition

- The crack propagation is similar to Rcon

-The fibres did not penetrated completely in the slot region

- The relatively low capacity is more a function of the small amount of fibre.



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Decathlon system drainage cover slabResults and DiscussionEquivalent flexural strength

Code Slab test Prism tests

Fibre content

[%]

BOP load

[kN]

Peak load

[kN]

fe,2

[kN/mm2]

fe,3

[kN/mm2]

Rcon - 93.5 253 - -

Pcon 6 103 170 13.5 11.4

Scon 2 107 141 5.0 3.6

SIScon 17.5 196.8 299 8.99 10.8



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Conclusions• steel fibres from recycled tyres can be successfully used to reinforce structural elements.

• Rcon passed the test for class C250 (BS EN 124, 1994), failurewas due to punching shear and had the lowest bend-over-point (BOP) of all slabs.

• Scon slab (2% by weight) passed the test for class B125 loadingcondition. The penetration of the fibre in the slotted region of the slab was not perfect.

• Pcon (6% by weight) passed only the B125 loading condition, high energy absorption due good fibre anchoring, the penetrationof the fibres in the slotted region of the slab was poor.

• SIScon (17.5% by weight). The fibre was placed in the mould without any processing and had a high amount of rubber. The cement slurry pretreated the bundled fibres well and hence, a good result was obtained. The slab exhibited extremely high strength and ductility, even higher than Rcon and passed the test for C250 comfortably.

Tested Concrete Slabs

0

50

100

150

200

250

300

350

-1 0 1 2 3 4 5 6 7 8 9

Deflection [mm]

Load

[kN

]

Pcon Rcon2 Scon SIscon



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I wish they were recycled instead



University of Sheffield, Department of Civil and Structural Engineering

Documents

Slurry Infiltrated Shredded Fibre Reinforced Concrete ...ci.group.shef.ac.uk/files_RT_site/befib_2004.pdf · Slurry Infiltrated Shredded Fibre Reinforced Concrete ... Slurry Infiltrated