Triple-blend mixtures

Portland cement & silica fume blended with GGBS or Fly Ash

20th April 2016

Abstract • This presentation investigates the use of triple-blend cementitious

mixtures with silica fume, now widely used in the production of high performance concrete.

• These high performance triple-blend mixtures are often comprised of Portland cement + fly ash + silica fume, or Portland cement + GGBS + silica fume.

• The presentation reviews a selection of international projects, including the Burj Khalifa building in Dubai and the Confederation Bridge in Canada.

• It is concluded that a triple-blend approach to high performance concrete mix design can enable cost savings, increased performance and improved sustainability.

Reasons for selecting triple blends with silica fume:

• Improved performance

• Economical

• Sustainability

Corrosion of steel reinforcement

Structures at risk from chloride ion induced damage:

• Marine structures in or near seawater

• Bridges, roads and other structures exposed to deicing salts

Marine structures – Triple blend concrete for long service life

Storebæ lt Bridge, Denmark

Tsing Ma Bridge, HK

Tall buildings – Benefits of Triple blends

Burj Khalifa

Petronas Towers

Triple Blend Mix Designs

Foundations of the Petronas

Towers:

•Triple blend for lower heat of

hydration

• PC + fly ash + silica fume

Example projects Project Country Blend

1 Storebaelt Bridge Denmark PC:FA:SF

2 Oresund Link Denmark - Sweden PC:FA:SF

3 Burj Khalifa, Dubai UAE PC:FA:SF

4 Kingdom Tower, Jeddah Saudi Arabia PC:FA:SF

5 Bandra-Worli Sealink Bridge, Mumbai India PC:FA:SF

6 East Sea Bridge, Shanghai China PC:GGBS/FA:SF

7 Confederation Bridge Canada PC:FA:SF

8 Indianapolis International Airport parking complex USA PC:FA:SF

9 New York DOT bridge deck overlays USA PC:FA:SF

10 One Island East Hong Kong PC:FA:SF

11 Tsing Ma Bridge Hong Kong PC:GGBS:SF & PC:FA:SF

12 MTRC Hong Kong PC:GGBS:SF

13 DTSS Singapore PC:GGBS:SF

14 Petronas Towers Malaysia PC:FA:SF

15 Muscat International Airport Oman PC:FA:SF

GGBS (~ 10 microns)

Silica Fume (~ 0.1 microns)

Fly Ash (~ 10 microns)

Comparison of particle size & shape

Silica fume manufacturing plants – Examples in Norway

Bremanger High purity metallurgical silicon Silgrain capacity: 40,000 tpy

Thamshavn Silicon capacity: 45,000 tpy

Salten Silicon capacity: 65,000 tpy

Production of silicon & silica fume (microsilica)

Silica fume – Physical properties

Silica fume particles: •Extremely small size; <1 µm •Spherical shape

Particle size comparison: •Each silica fume particle about 100 times smaller than Portland cement

Silica fume – Chemical properties

Silica fume is safe, pure & consistent: •Typically >90% amorphous silicon dioxide

Silica fume is Pozzolanic: •When mixed with Portland cement it reacts with calcium hydroxide, forming calcium silicate hydrate

S iO 2

Reaction in Concrete Concrete without Silica fume:

•permeable cement paste structure

•weak ‘transition zone’ between aggregate & cement paste

Cement particle

Aggregate

Concrete with Silica fume:

•Pozzolanic reaction; SiO2 reacts with Ca(OH)2

•Extremely small particles; beneficial packing

•Impermeable paste structure with strong transition zone

Reaction in Concrete

Oresund Link (Bridge & Tunnel) – Denmark to Sweden

• Triple blend, 100 year service life

Sandberg report, UK, 1991 (testing: taywood engineering)

0

0.5

1

1.5

2

2.5

100% Portland cement 50:50 PC + GGBS 50:40:10 PC + GGBS + Silica fume

Chloride Permeability, x10-9 cm2 / sec

Sandberg report, UK, 1991 (testing: taywood engineering)

0

20

40

60

80

100

120

140

100% Portland cement 50:50 PC + GGBS 50:40:10 PC + GGBS + Silica fume

Electrical resistivity, after 9 months wet curing

Electrical resistivity

• Corrosion progress is controlled by electrical resistivity of concrete • As concrete resistivity increases, the rate of corrosion decreases (Gannon

and Cady, 1992) • Electrical resistivity of concrete influenced by:

• Moisture content • Ion content within pores • Pore structure • Temperature

• Silica fume increases the resistivity of concrete

Yangshan Deep Water Port, Phase III, 2008

• Port is linked to mainland by

32.5 km bridge

• 东海大桥 = ‘East Sea Bridge’

• Bridge contains 13,000 tonnes of SF (opened 2005)

• Port contains 10,000 tonnes of SF

Yangshan Deep Water Port, Phase III, 2008

Yangshan Deep Water Port, Phase III, 2008

C45 kg/m3

Cement (pre-blended with

15% fly ash + 5% silica fume)

441

Fine aggregate 757

Coarse aggregate 1046

Water 150

Super plasticiser 6.17

Target slump 160 mm

w/c ratio 0.34

Theoretical density 2400

Yangshan Deep Water Port – Mix Design

Bridge deck, New York State DOT, USA Requirement: Resist chloride ion penetration

Mix Design: Portland cement 300 kg/m3 Fly ash 80 kg/m3 Microsilica 25 kg/m3 w/cm 0.40 Slump 75 - 100 mm Air 6.5 %

Wet cure 7 days

Burj Khalifa

Burj Khalifa

Superstructure concrete mix: The 80 MPa superstructure concrete mix contained silica fume (10% of binder), along with fly ash (13% of binder) and specially selected admixtures. Maximum aggregate size 20mm. Designed to be almost self-consolidating in consistence, with slump flow typically 600mm, this mix was used until pumping pressure exceeded approximately 200 bar.

Burj Khalifa

Piling concrete mix (SCC): Total binder content 450kg/m3 incorporating 37% fly ash & 7% silica fume. Maximum aggregate size 10mm. Self-compacting consistence, using two superplasticers at water/binder ratio 0.32, strength required 60 MPa

Bandra – Worli sea link, Mumbai • Length 5.86 km; 4 km marine bridge portion

• More than 200,000 m3 of high performance concrete

• M50 for piles and M60 grade for piers, pile caps & pre-cast structures

• Triple blend PC + FA + SF specified for pile caps and piers

Pile cap concreting in progress

Mix Details of Pile Cap Concrete (kg/m3) Cement (53 Grade) 300

Silica fume 40

Fly ash 196

Coarse aggregate 20mm 577

Coarse aggregate 10mm 500

Natural sand 423

Crushed rock 327

Free water (litres) 134

Water Binder ratio 0.25

Admixture (litres) 13.4

Confederation Bridge, Canada

• 13 km bridge linking Nova Scotia with Prince Edward Island

• Opened 1997

• 100 year design life

Confederation Bridge, Canada

Design Requirements Mix Proportions

91-day Strength 60 MPaCement(incl. 7.5% microsilica)

430 kg/m3

(32 kg/m3)

Min. CementingMaterials

450 kg/m3 Fly Ash 45 kg/m3

Max. w/c 0.34 Sand 705 kg/m3

Cement Type 10 SF Stone 1030 kg/m3

Fly Ash 10% max. Water 145 kg/m3

Permeability <1000 coulombs Water Reducer 1.8 litre/m3

Air Content 5-8% Superplasticiser 3.3 litre/m3

Slump 250 +/- 40 mm Air Entrainment As required

• Completed in 2009

• Total cost 24.3 billion RMB

• 67,000m3 of C50 abrasion-erosion resisting concrete

• Around 2,000mt silica fume

• Designer: Central Southern Geotechnical Design Institute Co Ltd

Longtan Hydropower Station, PRC

Longtan Hydropower Station, PRC

• Portland cement + Fly ash + Silica fume mix design:

W/C FA％ SF％(of cement)

Sand Ratio%

Total Binder kg/m3

C50 Anti-abrasion Concrete ( kg/m3 )

Water Cement FA SF Sand Stone Admix

0.296 10 8 40 460 136 387 43 30 735 1102 3.68

Rheology / Pumping - Example – Guangzhou IFC

• C80 pumped to 410m: • PC 42.5 R (Chinese GB175) – 420 kg/m

3

• GGBS – 140 kg/m3

• Silica fume – 20 kg/m3

• Superplasticiser – PCE • Water/binder ratio 0.26 • Consistence 220~260mm

Sustainability

Material Embodied CO2

(kg / tonne)

Portland cement, CEM I 930

GGBS 52

Fly ash 4

Silica fume powder 28

Source: TR 74 – Embodied CO2 of main constituents of reinforced concrete

High performance triple blend concrete with silica fume

• Higher performance • Strength • Durability

• Less permeable • Higher resistance to chemical ingress & damage • Greater protection for reinforcing steel, especially in critical infrastructure e.g.

marine structures

• Improved rheology • Pumping, shotcrete, SCC & grouts

• Economical

• Sustainable

Conclusion

• A triple-blend approach to high performance concrete mix design can enable cost savings, increased performance and improved sustainability