KHAYAT Rheology and Worability Abreviated - GERMANN Rheometer/7-Presentation5_Khayat... · ACI Fall 2009 Convention Kamal H. Khayat Relationship between Rheology and Flowable Concrete

ACI Fall 2009 Convention Kamal H. KhayatRelationship between Rheology and Flowable Concrete Workability U. de Sherbrooke, Canada

1

Relationship between Rheology and Flowable Concrete Workability

Kamal Henri Khayat

Things you Need to Know about Workability of Concrete - 2009 Fall Convention

Relationship between Rheology and FlowableConcrete Workability

• Rheology vs. washout resistance

• Rheology vs. workability of SCC– Rheology vs. workability test methods

– Workability of fiber-reinforced SCC

– Effect of mix design on rheology of SCC

• Rheology vs. hardening properties - form pressure

- interlayer bond of green SCC

- top-bar effect

Oh, I see !

Rio.. what.. ?

Rheology affects ease of mixing,

pumping, flow, segregation, washout,

formwork pressure, surface finish,

microstructure development …

First encounter with rheology

Binder

W/CM

CM (kg/m3)

Sand / agg.

Slump (mm)

Welan gum (% cwt)

Cell. (mL/100 kg CM)

100% cement & 8% silica fume

0.37 0.41 0.47 0.47

450 420 400 540

0.41 0.41 0.41 0.47

220 190 220 270 SCC UWC

0, 0.05, 0.10, and 0.15

600, 900, and 1200

Rheology vs. slump and washout

Rheology of Underwater Concrete

Washout loss test (CRD C61)

Slump = 210 ± 20 mm

NoAWA

0.10% cwt WG

0

4

8

12

16

0.36 0.38 0.4 0.42 0.44 0.46 0.48

w / cm

Was

ho

ut l

oss

(%)

100% C- - - 8% SF

1200 ml Cell

Khayat and Assaad, 2003


2

20151050

180

200

220

240

260

280

W/C = 0.37

W/C = 0.47

W/C = 0.47SCC

Washout loss (%)

Slu

mp

(mm

)

W/C = 0.41

Washout not a function of slump


0.80.60.40.200

1

2

3

4

5

6

7

8

Speed (rev/s)

Torq

ue

(Nm

)

g

h

T = g + h N

N

Time

MK-III Rheometer

1.00.80.60.40.200

5

10

15

20

25

30 S= 220 +10 mmW/CM= 0.47

8%SF

Speed (Rev/s)

Torq

ue

(Nm

)

No AWA

AWA + SP

Effect AWA + HRWRA on g and h

201510500

2

4

6

8

Washout loss (%)

g (N

m)

W/CM = 0.37

W/CM = 0.47

W/CM = 0.47 SCC

W/CM = 0.41

100% C 8% SFWG Cell.


201510500

10

20

30

40

50

Washout loss (%)

h (

N m

. s)

W/CM = 0.37

W/CM = 0.47

W/CM = 0.47 SCC

W/CM = 0.41

100% C 8% SFWG Cell.


h (Nm.s)0

1

2

3

4

5

6

7

0 10 20 30 40 50

g (N

m)

2% < wash. < 4%

4% < wash. < 7%

washout > 10%7% < wash. < 10%

Washout = f (g, h)

Workability box for washout loss



3







- top-bar effect


Conventional

concrete

high passing ability (low ττττ0 + mod. visc.)

low resistance to flow (low ττττ0)

Flow behavior of SCC is complex and must be

optimized to secure adequate performance

high stability (moderate visc.)

low yield value and viscosity

Lack of static stability after casting

ττττy ≥ 2/3 g (ρ ρ ρ ρ p −−−− ρ ρ ρ ρ m) MSA

Rheology of matrix must be controlled

to avoid particle segregationLaboratory & field test methods to assess SCC workability

2

4

6

8

10

10 15 20 25 30 35h (N.m.s)

Slu

mp

flo

w ti

me

T50

(sec

)

Cement content = 385 kg/m³


Khayat et al. 2004

T50 vs. h

0

10

20

30

40

10 15 20 25 30 35

h (N.m.s)

V-f

un

nel

flo

w ti

me

(sec

)



Khayat et al. 2004

V-funnel flow vs. h


4

0

4

8

12

16

10 15 20 25 30 35h (N.m.s)

L-b

ox

flo

w ti

me

(sec

)

0

10

20

30

40

50

U-b

ox

flo

w ti

me

(sec

)

L-box test; R² = 0.65

U-box test; R² = 0.74

U-box test

Khayat et al. 2004

Increase of L-box and U-box flow times with h

Correlate workability characteristics to

intrinsic rheological properties

Relative error, %

T50 27

V-funnel

34

µp 8

(R2 = 0.81)

N=24

(R² = 0.70)

N = 31

0

2

4

6

8

10

50 150 250 350 450 550 650

µp (Pa.s)

T5

0 (

sec)

0

5

10

15

20

25

30V

-fun

nel flo

w tim

e (sec)

T50

V-funnel

T50

V-funnel

(φφφφ = 680 ± 20 mm)

NCHRP 628, 2005

Viscosity vs. passing ability

(φφφφ = 680 ± 20 mm)

(R2 = 0.63)N = 24

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 200 400 600 800

µµµµp (Pa.s)

L-B

ox b

lock

ing

ra

tio

, h

2/h

1

MSA C3/4 in.

MSA C3/8 in.

MSA C1/2 in.

MSA G1/2 in.

NCHRP 628, 2005

ττττy≥ 2/3 g (ρ ρ ρ ρ p −−−− ρ ρ ρ ρ m) MSA

MSA ¾ in.

0

1

2

3

4

5

6

7

8

0 200 400 600 800µµµµp (Pa.s)

Seggre

gati

on

in

dex (%

)

MSA 3/8, ½ in.

(φφφφ = 670 ± 20 mm)

Viscosity vs. static stability

ττττ0 controls onset of

segregation

µµµµpl affects rate of segregation

NCHRP 628, 2005

Surface settlementSurface settlement

0

0.2

0.4

0.6

0.8

0 100 200 300 400 500 600Elapsed time (h)

Su

rfac

e se

ttle

men

t (%

)

Conv concrete 0.40

0.42 No VEA

0.39 No VEA

0.35 No VEA

(φφφφ = 670 ± 20 mm)

0

100

200

300

400

500

0.0 0.2 0.4 0.6 0.8 1.0

Maximum settlement (%)

Pla

stic

vis

cosi

ty (

Pa.

s)

Surface settlement vs. Surface settlement vs. µµµµµµµµpp

NCHRP 628, 2005


5

550

610

670

730

0 20 40 60 70 90 100

Filling capacity (%)

Slu

mp

flo

w (m

m)

0% no fibers

0.5% steel fibers

1% steel fibers

Slump flow ≠ filling capacity

Khayat and Roussel, 2000

0

20

40

60

80

100

0 5 10 15 20 25

h (Nm.s)

Fill

ing

cap

acit

y (%

)

1.0 350 0.75

0 250 0.60 250 0.750 300 0.60 300 0.750 350 0.60 350 0.750.5 250 0.60.5 250 0.750.5 300 0.60.5 300 0.750.5 350 0.60.5 350 0.751.0 250 0.6

1.0 300 0.751.0 300 0.61.0 250 0.75

1.0 350 0.6

Vf Vca S/P


0

0.4

0.8

1.2

1.6

0 5 10 15 25 30

Plastic viscosity (Nm.s)

Yiel

d s

tres

s (N

m)

8971

Filling capacity≥ 75%

50% - 75%

Volume of steel fibers0 0.5% 1%

70

5662

50

41

52

31

26

36

25

22

14

16

9

17

15

49

78

91

93 88

78

87

9693

91

94

88

96 77

79

96

8566

772095

9389

92

56

73

4328

49

23

14

71

41

83

83

Vca = 0.25-0.36

S/P = 0.6-0.754

20

Filling capacity of FR-SCC

can be related to rheological parameters








- top-bar effect


0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 10 20 30 40 50

Lateral pressure (kPa)

Hei

gh

t o

f co

ncr

ete

(m)

ρρρρgh

at casting

~ 50% after 4 hr

R = 10 m/hr

Variations in lateral pressure envelope

Slump flow = 650 mm

60 70

Loss in slump flow is not sufficient to evaluate decay in lateral pressure

50

60

70

80

90

100

0 50 100 150 200 250 300

Loss in slump flow after 2 hrs of rest (mm)

K0

at 2

hrs

(%)

Around 70 SCC mixtures

Khayat et al., 2003


6

0

40

80

120

160

0 200 400 600 800 1000

Time (s)

γ = fixed

γ = 0.03 s-1

sample at rest

Sh

ear

stre

ss (

Pa)

Thixotropy: variation of viscosity withtime at constant shear rate (reversible))

Structural build-up(flocculation, coagulation)

Testing protocol of thixotropy

1

Sh

ear

stre

ss (

Pa)

0

200

400

600

800

0 5 10 15 20 25

Time (sec)

0

200

400

600

800

0.2 0.4 0.6 0.8

Rotational speed (rps)

thixotropy (J/m³.s)

Magnitude of

(Breakdown area)N = 0.3 rps

N = 0.7 rps

N = 0.9 rps

N = 0.5 rps

Khayat et al., 2003

Ab2 60 – 90 min vs. K at 100 min

Ab3 120 – 150 min vs. K at 200 min

Ab vs. lateral pressure measured initially and after 100 and 200 min

0

20

40

60

80

100

50 200 350 500 650 800

Breakdown area (J/m³.s)

P(m

axim

um

) / P

(hyd

rost

atic

) (%

)

Ab1 0 - 30 min. vs. K @ 0 min

70 SCC

2.8-m high column

R² = 0.89

R² = 0.85

R² = 0.84


Field validation

H = 5.5 - 6 mL = 7 mW = 0.19 mAs = 0.4%

7 pressure sensors

Typical formwork pressure diagram

0

1

2

3

4

5

6

0 20 40 60 80 100 120

Pressure developed on formwork (kPa)

Hea

d o

f co

ncr

ete

(m)

ρ.ρ.ρ.ρ.g.h

Slump flow = 720 mm S/A = 0.50Ternary cement = 475 kg/m³ w/cm = 0.40

R = 6.5 m/hr

right after casting

1 hr3 hr

P(max)

Khayat et al., 2005

Actual pressure is less than hydrostatic !

0.0

0.2

0.4

0.6

0.8

1.0

0 200 400 600 800 1000 1200

Time after casting (min)

P(m

axim

um

) / P

(hyd

rost

atic

)

R = 6.5 – 9.5 m/hr

Khayat et al., 2005


7

37

N = 0.03 rps

0.00

0.05

0.10

0.15

0.20

0 5 10 15 20

To

rqu

e (N

.m)

Tmax

Time (s)

Structural build-up: Static yield stress at rest (τ0rest)

τ0rest = Tmax/G

0

20

40

60

80

100

0 400 800 1200 1600 2000

K0

(%)

PVτ0 rest@15min (Pa)

R = 2 m/hr

T = 22 oC

Dmin= 200 mm

MSA = 14 mm

WP = 0

H=2m4m6m8m

10m12m

K0 = f(H, R, Dmin , PVτ0rest@15min@Ti].fMSA.fWP

Khayat and Omran, 2009

Homogeneity of bond strengthHomogeneity of bond strength

H = 1.5 m

• J-Ring: 630 – 640 mm

• L-box ≥ 0.75

• Filling capacity ≥ 90%

• VSI: 0 – 1

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10

Elapsed time (hour)

Su

rface

set

tlem

ent (%

)

High µµµµp, Ab

Vibrated HPC

Low ττττ0, µµµµp, Ab

Med. µµµµp, Ab

SCC mixtures

NCHRP 628, 2009

In-situ compressive strength

0

30

60

90

120

150

80 85 90 95 100 105 110

f'c (core)/f' c (bottom) (%)

Dis

t. f

rom

bo

tto

m (

cm) Vibrated

HPCMed. µµµµp, AbHigh

µµµµp, Ab


NCHRP 628, 2009

Top-bar effect

0

30

60

90

120

150

0.8 1.0 1.2 1.4 1.6 1.8 2.0

Dis

t. fr

om

bo

tto

m (c

m) Vibrated

HPC

−

)situin(//)bottom(/ fUfU

'

ct

'

cb

l1

l2

P

P

Med.

µµµµp, Ab

High

µµµµp, Ab


Lack of proper consolidation

NCHRP 628, 2009


8

FACULTÉ DE GÉNIEFACULTÉ DE GÉNIEFACULTÉ DE GÉNIEFACULTÉ DE GÉNIEwww.USherbrooke.ca/genie

Static stability

Maximum surface settlement ≤ 0.5%

Column segregation index (Iseg) ≤ 5%

Percent static segregation (S) ≤ 15

Viscosity

Plastic viscosity ≤ 0.073 psi.s (500 Pa.s)

(Modified Tattersall two-point rheometer with

vane device)

Mechanical

properties

Core-to-cylinder compressive strength ≥ 90%

(similar curing conditions)

Bond strength modification factor ≤ 1.4

Recommended values to ensure homogeneous properties

NCHRP 628, 2009

References• Assaad, J., Khayat, K.H., Mesbah, H., Assessment of Thixotropy of Flowable and Self-

Consolidating Concrete, ACI Materials Jr., 100, (2), 2003, pp. 111-120.

• Assaad, J., Khayat, K.H., Daczko, J., Evaluation of Static Stability of Self-Consolidating Concrete,

ACI Materials Jr., 101, (3) 2004, pp. 207-215.

• Khayat, K.H., Assaad, J. Relationship Between Washout Resistance and Rheological Properties of

High-Performance Underwater Concrete, ACI Materials Jr., 100, (3), 2003, pp. 287-295.

• Khayat, K.H., Assaad, J. Use of Rheological Properties of SCC to Predict Formwork Pressure, SCC

2005, Proceedings of the 2nd North American Conference on the Design and Use of Self-

Consolidating Concrete and the 4th International RILEM Symposium on Self-Compacting Concrete,

Evanston, IL, Ed. S.P. Shah, pp. 671-677.

• Khayat, K.H., Assaad, J., Daczko, J., Comparison of Field-Oriented Test Methods to Assess

Dynamic Stability of Self-Consolidating Concrete, ACI Materials Jr., 101, (2) 2004, pp. 168-176.

• Khayat, K.H., Omran, A.F., Evaluation of SCC Formwork Pressure, Proceedings of the 2nd

International Symposium on the Design, Performance and Use of Self-Consolidating Concrete

(SCC’2009), Beijing, China, Ed. C. Shi, Z. Yu, K.H. Khayat, and P. Yan, June 5-7, 2009, pp. 43-55.

• Khayat, K.H., Roussel, Y., Testing and Performance of Fiber-Reinforced, Self-Consolidating

Concrete, RILEM Materials and Structures, 33, July 2000, pp. 391-397.

• NCHRP 628 Report, Self-Consolidating Concrete for Precast, Prestressed Concrete Bridge

Elements, Khayat, K.H., Mitchell, D., 2009.

Documents

KHAYAT Rheology and Worability Abreviated - GERMANN Rheometer/7-Presentation5_Khayat... · ACI Fall 2009 Convention Kamal H. Khayat Relationship between Rheology and Flowable Concrete