Burj KhalifaA new high for high performance SCC

James Aldred PhD, CPEng, LEED AP, FIEAust, FACI, FICT

Technical Director – AECOMAdjunct Associate Professor - School of Civil & Environmental Engineering, University of New South Wales

Why build supertall buildings?Isn’t it unsustainable?

Holders of the Title of “World’s Tallest Building”

Burj Khalifa

Piling:

• 60 MPa SCC

Raft:

• 50 MPa SCC

Tower:

• 80 MPa to 440 metres

• 60 MPa to 581 metres

• 80 MPa to 585 metres

• 60 MPa to 605 metres

Burj Khalifa – Tower Foundations

Mix Design for raft (Temperature and durability considerations)

Cement (MSRPC) 252 kg/m3

Fly Ash 168 kg/m3

Silica fume 30 kg/m3

Aggregate (20 mm) 368 kg/m3

Aggregate (10 mm) 368 kg/m3

Washed crushed sand (0-5 mm) 552 kg/m3

Dune Sand (0 – 0.6 mm) 552 kg/m3

Fine Aggregate Component 60%Polycarboxylate SP 4 - 6 L/m3

VMA 1 - 1.5 L/m3

w/cm 0.32

Slumpflow during production (Approx 5000 m³)

Burj KhalifaTemperature rise in centre of tower raft

THE BURJ DUBAI TOWER RAFT FOUNDATION WORKS

Automated Concrete Temperature Monitoring

COLUMN H

10

20

30

40

50

60

70

80

13-Oct 18-Oct 23-Oct 28-Oct 2-Nov 7-Nov 12-Nov 17-Nov 22-Nov 27-Nov 2-Dec 7-Dec 12-Dec 17-Dec 22-Dec 27-Dec 1-Jan

Date : Time

Tem

pera

ture

(D

eg

ree C

)

Ambient

TC_H1

TC_H2

TC_H3

TC_H4

TC_H5

TC_H6

Compressive strength of cores (ASTM C39)

ASTM Core tests

0 10 20 30 40 50 60 70 80

28-3000 (2)

24-2800 (2)

20-2400 (1)

16-2000 (0)

12-1600 (4)

8-1200 (1)

4-800 (3)

0-400 (6)

Dep

th in

to r

aft

(N

o o

f re

su

lts)

Strength MPa

Modulus of cores (ASTM C469)

Modulus

0 5000 10000 15000 20000 25000 30000 35000 40000 45000

28-3000 (1)

24-2800 (1)

20-2400 (0)

16-2000 (5)

12-1600 (0)

8-1200 (5)

4-800 (3)

0-400 (2)

Dep

th in

to r

aft

(n

o o

f re

su

lts)

Modulus N/mm2

Coulomb values (ASTM C 1202)

Rapid Chloride Permeability Test

0 100 200 300 400 500 600

28-3000 (1)

24-2800 (0)

20-2400 (0)

16-2000 (0)

12-1600 (1)

8-1200 (1)

4-800 (1)

0-400 (3)

Dep

th in

to r

aft

(n

o o

f re

su

lts)

Permeability - coulomb

Burj Khalifa - Structural System Description

Reinforced Concrete Core Wall System

hotel / residential / office

Steel Braced Frame

spire, communication

Pile Supported Raft Foundation

Mixture proportions

Code C80-20 C80-14 C80-10 C60-10 C50-20 C50-14

Max.Agg 20 14 10 10 20 14

w/cm 0.27 0.30 0.29 0.35 0.36 0.36

OPC 380 384 400 376 328 338

FA 60 96 100 94 82 112

SF 44 48 50 25 25 25

F.Agg % 50 49 49 51 49 50

Pumping Trial

Reductions in slumpflow during pumping trials

Pipe Length(m) Concrete grade

Slumpflow(mm)

At plant Before

pumping

After

pumping

Loss

/100m

250 C80-20 600 580 495 34

450

C80-14 600 545 475 16

C80-10 630 560 415 32

C80-20 600 540 420 27

600

C50-14 630 580 480 17

C60-10 620 560 395 28

C80-14 600 410 32

Concrete pressure during trials

Pipe

Length(m)

Concrete grade

Output(m3/hr)

Friction factor

Concrete pressure (bars)

Hopper 250m 450m 600m

250 C80-20 29 5.3 119 21 - -

450

C80-14 29 2.3 88 43 10 -

C80-10 33 2.0 90 47 11 -

600

C50-14 30 1.6 88 51 27 8

C60-10 27 1.9 99 63 34 11

Increases in temperature during pumping trials

Pipe Length(m) Concrete grade

Temperature (0C)

At plant Before

pumping

After pumping Increase

/100m

250 C80-20 26 27 30 1.2

450

C80-14 25 25 29 0.9

C80-10 28 27 32 1.1

C80-20 27 28 37 2.0

600

C50-14 26 27 33 1.0

C60-10 27 28 35 1.2

C80-14 29 35 1.0

Pump Station at ground level

0

5

10

15

20

25

30

35

40

0

100

200

300

400

500

600

700

17-Jun-06 24-Jun-06 1-Jul-06 8-Jul-06 15-Jul-06 22-Jul-06 29-Jul-06 5-Aug-06 12-Aug-06 19-Aug-06 26-Aug-06

Co

ncre

te t

em

pera

ture

(0C

)

Slu

mp

flo

w (

mm

)

Date poured

C80A - Slumpflow and temperature data

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

0

25

50

75

100

29/11/06 18/1/07 09/3/07 28/4/07 17/6/07 06/8/07 25/9/07 14/11/07

Std

Dev

iati

on

(M

Pa)

Stre

ngt

h (

MP

a)

Measuring Pressure

Pumping pressure vs height

0

20

40

60

80

100

120

140

160

180

200

0 100 200 300 400 500 600

Height (m)

Pre

ssu

re (

bar)

C80-20

C80-14

C60-14

Linear

(C60-14)Linear

(C80-20)Linear

(C80-14)

Concrete Rheology – Key to High Pressure Pumping

Effect of pumping on fresh concrete properties

Grade of concrete

Level

Samplingbefore

pumping

after

pumping

before

pumping

after

pumping

before

pumping

after

pumping

before

pumping

after

pumping

before

pumping

after

pumping

before

pumping

after

pumping

Slump Flow (mm) 640 545 620 570 710 635 640 620 570 550 690 600

T-500 (sec) 2.4 2.5 2.6 2.0 3.5 3.1 4.7 3.9 9.2 4.1 4.3 6.9

Temperature (C ) 25.0 29.0 25.0 28.0 25.0 27.0 25.0 26.5 28.0 31.0 24.0 26.0

P lastic viscosity (P a.s) 24.0 12.7 24.7 13.0 39.8 29.7 40.9 16.0 51.4 26.9 93.4 45.8

Dynamic Yield Stress (Pa) 56.8 116.8 61.5 125.4 12.1 37.1 62.6 92.4 85.4 116.0 18.5 48.3

C80/20 (5inch)

L102L126

C60/14

L129

C80/14

L115-1 L115-2 L125

Tower Height: 1,000+ meters

Number of floors: 240 +

Estimated Concrete: 250,000 m3

– 85 MPa to L98 170,000 m3

– 75 MPa to L168 70,000 m3

– 65 MPa to 975m 10,000 m3

Kingdom Tower

Conclusions

• Concrete has now replaced steel as the material of choice for supertall building construction.

• Self consolidating concrete provides for rapid and high quality construction which can be pumped great distances.

• Good quality control to maintain consistent concrete properties is important to ensuring continuous uninterrupted concrete pumping at high pressure.

• Ensuring a cohesive slurry to prime the pipeline is important to prevent segregation and blockage, especially in pumping highly workable concrete.

Thank You

James.Aldred@aecom.com