4.3.3 Case study 3

Steel fiber concrete 16/11/2018 - Brussels

Prepared by Svatopluk Dobrusky Presented by François de Larrard

LCR LafargeHolcim, Lyon, France

Case study 3 - FRC

• 4.3.3: Case study 3: Demonstration of technological solutions fostering circular economies of steel fibre reinforced concrete fractions from C&DW Leader: LAFAR; Participants: TECH, ACC, RTT, BRGM, SELF.

• Objectives: To demonstrate technological developments for the selective recovery of steel fibers, aggregates and cement paste contained in fiber reinforced concrete waste.

• Description: LAFAR will stock steel fiber reinforced concrete waste in their plants in France (potentially in Paris, Lyon, Nantes and/or Marseille). Also, selected masonry waste with adhered impurities will be collected and stocked at LAFAR facilities. The novel mobil electro-fragmentation unit (by SELF) will be transported to LAFAR facilities. On the basis of conclusions in Task 3.1.2 (BRGM), the parameters in the mobile unit will be adjusted. Crushed steel fiber reinforced concrete and, in a second stage, ceramic waste will be fed into the electro-fragmentation unit. The fractions will be post-processed (by using magnetic separators and sieving) to recover metallic fibers and recycled aggregates distinguishing between coarse and fine fractions. The recovered fractions will be used in the manufacturing of new reinforced concrete in LAFAR facilities. Diverse recipes of concrete will be firstly designed (based on Task 3.1.4) and the produced in real manufacturing plants belonging to LAFAR. The incremental innovation in low-embodied energy cements manufactured with recovered C&DW materials will be used in the concrete recipes. new concretes will be characterized: slump, compressive strength at 7, 8 and 90 curing days, determination of shrinkage, modulus of elasticity at 28 curing days and durability issues to be defined on the basis of the exposure. Precast elements will be produced and then installed in the ACC's Demo-park. Durability performance will be monitored under real conditions.

Principles of the high voltage electric pulse fragmentation (EPF) technology

• Use of highly energetic electrical pulses (150 - 750 J/pulse) with a very fast voltage ramp-up time (<500 ns)

- Dielectric strength of the water > Dielectric strength of the solid

- Discharges go through the solid, causing electrical breakdowns and internal shockwaves

- Selective breakage (liberation around grain boundaries) based on the discontinuities of the electrical and acoustic properties

EPF equipment

Lab scale tests Continuous pilot scale tests: SELFRAG Pre-Weakening Test-

Station

General overview

160 Mpa* Ductal concrete waste

Electro-Fragmentation

Crushing

Magnetic separators &

sieving 0-2mm recycled aggregate

HISER concrete manufacturing

Steel fiber

Coarse aggregate cement

* a real element, which should be recycled (footbridge/beam), made from 160MPa" UHPFRC

Recycled Ductal® manufacturing

Ductal® Premix

Recycled Fine sand*

Case study phases

Laboratory optimization of

UHPFRC using recycled materials

Real-scale casting of

UHPFRC HISER beam

Laboratory optimization of

GFRC using recycled materials

Real-scale casting of

GFRC HISER panels

Phase 1 Laboratory optimization

Phase 2 Real-scale casting

Each phase included Electric-Pulse Fragmentation tested in Task 3.1.2

Laboratory optimization of UHPFRC

• Replacement of steel fibers by HISER fibers

– 25%, 50%, and 100% ratio

• Replacement of sand by HISER sand

– 10%, 20%, and 30% ratio

Lab UHPFRC

UHPFRC beam

Lab GFRC

GFRC panel

Laboratory optimization of UHPFRC

• Fibers replacement

– No reduction of performances up to 100% ratio

• Sand replacement

– Reduction of elastic properties (compression & tension)

– Marginal reduction of post-cracking characteristics

Lab UHPFRC

UHPFRC beam

Lab GFRC

GFRC panel

Laboratory optimization of GFRC

• 100% replacement of virgin sand by the recycled HISER sand

– Two alternatives for Rheology optimization – Mix 3 & 4 vs. Mix 5 & 6

ELEMENT Mix 1 Mix 2 Mix 3 Mix 4 Mix 5 Mix 6

Ordinary Portland Cement (OPC) 759 759 759 759 759 759

Sand Hiser - 1 0 0 380 380 380 380

Sand Hiser - 2 0 0 380 380 380 380

Reference Sand 759 759 0 0 0 0

Water 266 266 266 266 266 266

Superplasticizer 13,3 14,4 21,3 21,3 18,5 18,5

Superplasticizer (%) - tempo/20HE 1,8% 1,9% 2,8% 2,8% 2,4% 2,4%

Acelerator - Sika Rapid - - - - 1,2% 1,2%

Cem-FIL AR glass fibres 65 65 65 65 65 65

Lab UHPFRC

UHPFRC beam

Lab GFRC

GFRC panel

Laboratory optimization of GFRC

Lab UHPFRC

UHPFRC beam

Lab GFRC

GFRC panel

• No reduction of mechanical performances when HISER sand

– Even slightly better performance were observed compared to traditional limestone sand

0

10

20

30

40

50

60

70

7 days 14 days 28 days

Co

mp

ress

ive

Str

en

gth

(M

Pa)

Compressive strength

Reference sand- 1 & 2

HISER sand - 3 & 4

HISER sand - 5 & 6

0

1

2

3

4

5

6

7

7 daysFl

exu

ral S

tre

ngt

h (

KN

)

Flexural strength

Real scale crushing – Scaling up Task 3.1.2

UHPFRC beams: 8 x 5.6m

Lab UHPFRC

UHPFRC beam

Lab GFRC

GFRC panel

Real scale crushing

• Crushing: – Sub-contracted

– Hydraulic Hammer

– On the ground (pollution)

– Difficult to crush = No less than 50mm (+ flaky materials: up to 8x)

• Total: about 650kg + corroded fibers + pollution + large particles…

BRGM had to handle this quality (thanks to them). Even for real case, the process of pre-crushing

UHPC is to be more deeply investigated

Lab UHPFRC

UHPFRC beam

Lab GFRC

GFRC panel

El. Fragmentation

• Sample preparation

– Jaw crushing of all the > 40 mm particles

– Sieving at 5 mm and 40 mm

– Jaw crushing of the oversize (> 40 mm)

• Most of the tests were performed with the Pre-Weakening Test Station (PWTS):

– Feed < 40 mm to avoid blockage

– Energy injected: about 13 kWh/t

– Circulation loop of the > 5 mm in the process

• A test with a bigger machine were performed on about 20 kg:

– Feed > 100-150 mm and no blockage!

– Feasibility test => Good results

Lab UHPFRC

UHPFRC beam

Lab GFRC

GFRC panel

C&DW Separation

• Sieving is requested since: – The fibers are liberated in the size fraction < 2 mm

– The conveyor belt of the PWTS is made with metal plates with a 5 mm spacing between each plate

• Magnetic separation performed with a dry low intensity magnetic separator (450 G)

Lab UHPFRC

UHPFRC beam

Lab GFRC

GFRC panel

Real-scale casting of UHPFRC HISER beam

Lab UHPFRC

UHPFRC beam

Lab GFRC

GFRC panel

HISER

UHPFRC [Unit]

Premix 2221 [kg/m3]

Fibres 67 [kg/m3]

HISER fibres 67 [kg/m3]

Spreading 265 [mm]

fc,mean 179.3 [MPa]

F3pnt,mean 29.5 [MPa]

Chloride

migration 2-8 x 10-12 [m2/s]

Real-scale casting of GFRC HISER panels

ELEMENT MIX HISER

GRC PANELS

MIX

REFERENCE

PANELS

OP Cement (kg) 49,4 49,4

HISER Sand – 1 (kg) 49,4

Reference Sand (kg) 49,4

Water (L) 17,3 17,3

Superplasticizer (L) 1,2 0,9

Superplasticizer (%) 2,40% 1,90%

Acelerator (%) 1,20% 1,00%

AR glass fibres (kg) 4,25 4,25

Lab UHPFRC

UHPFRC beam

Lab GFRC

GFRC panel

Case Study 4.3.3

UHPFRC HISER beam GFRC HISER panel

• Panels are being currently installed by Acciona

Illustrative photo

Lab UHPFRC

UHPFRC beam

Lab GFRC

GFRC panel

General overview

160 MPa* Ductal concrete waste

Electro-Fragmentation

Crushing

Magnetic separators &

sieving 0-2mm recycled aggregate

GFRC HISER panels

Steel fiber

Glass fibers cement

* a real element, which should be recycled (footbridge/beam), made from 160MPa" UHPFRC

UHPFRC HISER beam

Ductal® Premix

Lab UHPFRC

UHPFRC beam

Lab GFRC

GFRC panel

Conclusions

• Real-scale recyclability of UHPFRC has been proven

• EPF Technology is efficient recycling method (energy & speed)

• Simple crushing can be a good alternative to EPF

• HISER fibers can be used in new UHPFRC without any loss of performance

• HISER sand can be used in new GFRC without any loss of performance

Lab UHPFRC

UHPFRC beam

Lab GFRC

GFRC panel

Many thanks to all HISER partners, and especially to those of this task: BRGM (France),

Tecnalia and Acciona (Spain)