3/2/2012

Factors Affecting the Improvement of Clay with Blast-Furnace Slag

Lynn Salvati, M. ASCE, P.E., Ph.D, Jacobs AssociatesAndrew Pozolo, A.M. ASCE, Sargent & Lundy

Ground Granulated Blast-Furnace Slag (GGBFS) Used to Modify Clay

Advantages:Use of industrial byproduct / reduces greenhouse gas productionAdds significant strength

Disadvantages:Strength gain from pozzolanic reaction is slowLack of experience in usage

Materials UsedClay LL PL

Bentonite 500 50Kaolinite 45 25

Bentonite/Kaolinite Blend 240 40

Soils Tested:

Water Content:• LL to PLGGBFS: • US Steel plant in Gary, IN • Calcium content was 20% by weightPortland Cement (PC):• Type III Cement mixed with GGBFSBinder Content:• bc=(GGBFSdryweight+PC dryweight)/Soildryweight• 5% to 166% (or w/bc 1.5 to 25)

Sample Preparation• Dried clay and water were mixed

and then slurry was added• The slurry consisted of water

and GGBFS and/or PC• PC/Slag=0/10• PC/Slag=1/9• PC/Slag=2/8• Type I PC• Type III PC

Previous ResearchPrevious formulation [Horpibulsuk (2001, 2003), Miura et al. (2001), Kaushinger et al. (1992)]:

cwu

b

aq

Clay LL PL a (kPa) b R2 Study

Bentonite 500 50 2278 1.25 0.72 this study

Bentonite/Kaolinite 240 40 1864 1.22 0.59 this study

Ariake 120 57 7949 1.23 N/A Horpibulsuk et al. 2003

Bangkok 103 76-84 1739 1.29 N/A Horpibulsuk et al. 2003

Singapore 63-90 24-31 4730 1.87 N/A Lee et al. 2005

Boston Blue Clay 40-50 20 5626 1.87 N/A Kauschinger et al. 1992

Kaolinite 45 25 14240 2.44 0.92 this study

0

300

600

900

1200

1500

0 2 4 6 8 10

PC/Slag = 1/9, w = LLPC/Slag = 1/9, w = PL, w

opt

Su(kPa) = 18(1-LI+Vb)1.7

Su (k

Pa)

1 - LI + Vb

BentoniteR2=0.83

0

300

600

900

1200

1500

0 2 4 6 8 10

PC/Slag = 1/9, w = LLPC/Slag=1/9, w = PLSu(kPa) = 11(1-LI+Vb)1.9

Su (k

Pa)

1 - LI + Vb

Bentonite/Kaolinite BlendR2=0.67

0

500

1000

1500

2000

0 2 4 6 8 10

PC/slag = 1/9, w = LLPC/Slag = 1/9, w = w

opt

Su(kPa) = 3.9(1-LI+Vb)2.8

Type I PC only, w = LL Type III PC only, w = LL

Su (k

Pa)

1 - LI + Vb

KaoliniteR2=0.92

Proposed Strength

Relationship

where so and n are material coefficients, LI is the liquidity index and Vb is the volume of binder

100*

1

waterdrysoilPCslag

PCslag

no

VVVVVV

Vb

VbLIsSu

Ratio of Slag to Cement

0200400600800

1000120014001600

0 10 20 30 40 50 60

PC/Slag = 0/10

PC/Slag = 2/8 PC/ Slag =1/9

Su (k

Pa)

Time Between Mixing and Testing (Days)

Bentonite, w/bc = 3

w = LL

0

100

200

300

400

500

600

0 10 20 30 40 50 60

Su (k

Pa)

Time Between Mixing and Testing (Days)

Bentonite, w/bc = 6

0

20

40

60

80

100

0 10 20 30 40 50 60

Su (k

Pa)

Time Between Mixing and Testing (Days)

Kaolinite, w/bc = 6

Modulus MeasuresTwo measures of stiffness were measured:

Constrained modulus, M:• M= *(ultrasonic pulse velocity)2

• Measured using ultrasonic transducers• Non-destructive, low strain measure

Young’s Modulus at 50% failure stress level, E50• In this study, E50,tan taken at 50% of the failure

stress• Measured from compression test• Destructive test, higher strain measure

0

2

4

6

8

10

0 2 4 6 8 10

PC/Slag = 1/9, w = LLPC/Slag = 1/9, w = PLM(GPa) = 0.48(1-LI+Vb)

M (G

Pa)

1-LI+Vb

Bentonite/Kaolinite Blend

R2=0.83

0

2

4

6

8

10

0 2 4 6 8 10

PC/Slag = 1/9, w = LLPC/Slag= 1/9, w = PL, w

opt

M(GPa) = 0.44(1-LI+Vb)

M (G

Pa)

1-LI+Vb

Bentonite

R2=0.45

0

2

4

6

8

10

0 2 4 6 8 10

PC/Slag = 1/9, w = LLPC/Slag = 1/9, w= w

opt

Type I PC only, w = LL Type III PC only, w = LL

M(GPa) = 0.93(1-LI+Vb)

M (G

Pa)

1-LI+Vb

Kaolinite

R2=0.72

Proposed Modulus

Relationship

where Mo is a material coefficient

VbLIMM o 1

Comparison with Previous Correlations between Strength and Modulus

Study - Material E50/qu

this study – bentonite with GGBFS 125

this study – kaolinite with GGBFS 228

this study - bentonite/kaolinite blend with GGBFS 185

Lee et al. (2005) – singapore clay with PC 84-140

Van Impe et al. (2005) – clay mixed with GGBFS and PC 110

Kitazume (2005) - cement stabilized clay 350-1000

Correlation between Strength and Modulus

0

500

1000

1500

0 100 200 300 400

Su(kPa)=2.7*E50

(MPa)

Su (k

Pa)

E50

(MPa)

Bentonite/Kaolinite Blend

0

500

1000

1500

2000

2500

0 200 400 600 800 1000

Su(kPa)=2.2*E50

(MPa)

Su (k

Pa)

E50

(MPa)

Kaolinite

PC/Slag = 1/9

Type I PC onlyType III PC only

PC/Slag = 2/8PC/Slag = 0/10

0

500

1000

1500

2000

0 200 400 600 800

Su(kPa)=4.0*E50

(MPa)Su

(kPa

)

E50

(MPa)

Bentonite

Bentonite PC/Slag = 1/9 Bentonite: PC Type I onlyBentonite: PC/Slag = 2/8Kaolinite: PC/Slag = 1/9 Kaolinite: PC/Slag = 2/8Kaolinite: PC/Slag = 0/10Blend: PC/Slag = 1/9 Blend: PC Type III only

Time between Mixing and Compaction:Effect on Strength

0

250

500

750

1000

0 500 1000 1500 2000

Su (k

Pa) -

24

hour

del

ay

Su (kPa) - No Delay

1:2 line

0

100

200

300

400

500

0 2 6 24

28 days

Und

rain

ed S

treng

th (k

Pa)

Time Between Mixing and Compaction (Hours)

Bentonite, w =LL, w/bc = 67 days

56 days

Time between Mixing and Compaction:Effect on Modulus

0

2

4

6

8

10

0 2 4 6 8 10M

(GPa

) - 2

4 ho

ur d

elay

M (GPa) - No Delay

1:1 line

0

100

200

0 100 200 300 400

Bentonite PC/Slag = 1/9 Bentonite: PC Type I onlyBentonite: PC/Slag = 2/8Kaolinite: PC/Slag = 1/9

Kaolinite: PC/Slag = 2/8Kaolinite: PC/Slag = 0/10Blend: PC/Slag = 1/9 Blend: PC Type III only

E 50 (M

Pa) -

24

hour

del

ay

E50

(MPa) - No Delay

1:2 line

1:2 line

Conclusions• GGBFS is effective in improving the properties

of clay• The improvement of properties with GGBFS or a

blend of GGBFS and PC is comparable to or better than with PC

• Relationships based on the LI and Vb were developed to predict the strength the modulus of the improved clay

• Relationships between the strength and modulus are also provided

3/2/2012

AcknowledgementsThis study was made possible by financial assistance from the Office of the Lieutenant Governor of Indiana, Energy Group through an Innovations Grant with matching funds provided by the University of Notre Dame.

Support for this work was also provided by Holcim (US) Inc. The assistance provided by Barry Descheneaux of Holcim (US) Inc. is gratefully acknowledged