Shear strength of compacted soils using geopolymer

Shear Strength Enhancement of Compacted Soils Using Geopolymer

Soe ThihaM5640010

A Thesis Submitted of the Requirement for the Degree of

Master of Engineering in Geotechnology

Suranaree University of Technology

25 May 2015

Background and rationale Research objectives Scope and limitations Research methodology Literature review Sample preparation and collection Basic property test Compaction test Direct shear test Conclusion Future study

Outline

Back Ground and Rationale

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Back Ground and Rationale …

To increase the strength of soil properties

To decrease the permiability.

To decrease soil slope failure.

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Back Ground and Rationale …

SourceMaterial

By-pr

oduc

t

Alkaline

Liquid

Cutting the world’s carbon. Low price of materials Better compressive

strength. Fire proof. Low permeability. Eco-friendly. Excellent properties within

both acid and salt environments.

Advantages

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Research Objective

This study is to experimentally assess shear strength

enhancement of compacted soil using geopolymer in three-

ring shear testing device.

The test results from the research will figure out how shear

strength of compacted soil samples (with water and with

geopolymer) between curing and non-curing under room

temperature (27 30 C).

Scope and Limitations

Three types of soils are used.

The soil samples are mixed with water and with geopolymer.

Geopolymer is a mixture of fly ash and alkaline liquid with

equal amount of Na2Sio3 and NaOH.

Na2Sio3 and NaOH are liquid state.

The curing time has two stages as non-curing (for 0 day) and

curing (7 days) under room temperature.

Normal stresses (n) are 0.4, 0.6, 0.8 and 1 MPa.

Research Methodology

Geopolymer

Basic Properties Tests Three-ring direct shear test

Sample Collection and Preparation

Literature Review

Resolving and Comparison

Discussions and Conclusion

Thesis Writing

Water

Literature Review

Bagherzadeh-Khalkahali and Mirghasemi (2009) studied the

effects of particle size on macro and micro mechanical

behavior of coarse-grained soils. The results showed that the

internal friction angle the sample dilation increases with

growing the particle size.

Bhat et al. (2003) researched the effect of shearing rate on

residual strength of kaolin clay and showed that hardly

increases in residual strength with increase shearing rate of

kaolin clay (0.233 - 0.586 mm/min).

Literature Review …

Begrado et al. (2006) proposed that the internal frictional

angle of compacted clay is high at low normal stress and

decreases with increasing normal stress.

Sonsakul et al. (2013) proposed the performance

assessment of three-ring compaction and direct shear testing

device and found that shear strength and MDD obtained

from three-ring mold are higher than ASTM standard mold.

Davidovits (1978) coined the geopolymer which are new

material explored in many scientific fields and industrial

disciplines.

Moayedi et al. (2011) reported that the effect of Na2SiO3 on

UCS of soft clay become less and less with longer curing

time. Temperature and curing period are significant in

influence of strength development.


Sukmak et al. (2013) studied the geopolymerization

decreases with increasing moisture content due to the

reduction of alkaline liquid activator (L). At low moisture

content, low strength is obtained by inadequate L.

Phummiphan et al. (2014) found that the optimum liquid

alkaline activators for lateritic soil – fly ash geopolymer

specimens decreases as NaOH solution increases. The fly

ash geopolymer could improve the mechanical properties of

the marginal soil.


Chimoye (2014) studied the strength of soft Bangkok clay

improved by palm fuel ash geopolymer and found that higher

percentage of NaOH or palm fuel ash would give higher

compressive strength of Bangkok clay.

Chanprasert et al. (2014) studied the strength and

microstructure of water treatment sludge-fly ash geopolymer.

The geopolymerization increases with heat duration and

weld clay and FA particles, and fill up the pore spaces..


Sample Collection and Preparation

In this study, the soil samples are mixed together with

geopolymer blended raw materials, fly-ash and alkaline liquid

activator homogenously.

Raw materials are collected as three types of soils:

from Bang Nong Bong, Muang district, Nakhon

Ratchasima.

from Bang Khen water treatment plan, Bangkok.

from Dan Keen, Chock Chai district, Nakhon

Ratchasima.

Sample Collection and Preparation …

Fly ash (FA) is a by-product of waste materials obtained from

Mae Moh Power Plant in Northern Thailand. According ASTM

D618, FA is classified as class F.

Alkaline liquid is a mixture of Na2SiO3 and NaOH.

Na2SiO3 is composed of 15.5% of NaOH, 32.75% of

SiO2 and water of 51.75% by weight.

NaOH is 12.5 molars in solution.

Sample Collection and Preparation …

Fly-ash (FA) Sodium Hydroxide

(NaOH)

Sodium silicate

(Na2SiO3)

0 10 20 305 15 25 mm

Basic Property Test

All basic property tests are followed ASTM standards and

procedures. They are included as follow as:

Natural water content (ASTM D2216)

Specific gravity (ASTM D854)

Atterberg’s limit (ASTM D4318)

Grain size analysis (ASTM D422)

Unified soil classification system (ASTM D2487)

0

20

40

60

80

100

0.000.010.101.00

Per

cent

Pas

sing

(%)

Particle Size (mm)

10.00

Silty Sand (SM) Sludge (MH) Clay (CH)

Basic Property Test …

Grain size distribution curve for three types of soils

0.075

4.75


Soil plasticity chart (Casagrande, 1942)

Silty sand (SM)Passing (no.4) - 100%

Passing (no.200) - 30%

LL -

12.7%

PI -

0.6%Sludge (MH)Passing (no.4) - 100%

Passing (no.200) - 98%

LL - 58%

PI - 25.5%

High plasticity clay (CH)Passing (no.4) - 100%

Passing (no.200) - 93.2%

LL - 68%

PI - 39.2%

U-line P

I = 0.

9 (LL

-8)

0 10 20 30 40 50 60 70 80 90 1000

10

20

30

40

50

60

70

CL-ML

CL or OL

ML or OL

CH or OH

MH or OH

A-line

Liquid limit

Pla

stic

ity in

dex

0 10 20 305 15 25 mm

0 10 20 305 15 25 mm

0 10 20 305 15 25 mm

Table. Basic property test results of soil samples

Locations W (%) SG LL(%) PI(%) Soil Types

Ban Nong Bong 3.0 2.68 12.7 0.6 Silty sand (SM)

Dan Keen 10.5 2.67 68.0 39.2 High plasticity clay (CH)

Bang Khen Water Treatment

Plant5.6 2.56 55.0 23.0 High plasticity

silt (MH)


Compaction Test

Compaction is essential in many geotechnical applications to

improve the engineering properties of soils (Horpibulsuk et

al., 2013).

Proctor (1933) proposed the compaction test for MDD and

OMC, known as Proctor compaction test.

The proctor compaction test is easy to perform in the

laboratory due to workability of simple equipment.

Compaction Test …

To find OMC and MDD of compacted soils, the empirical

equations are used as follow as: (1)

(2)

Where = moist unit weight, W = moist weight of soil,

Vm = moist volume of soil, d = dry unit weight,

w = water content of soil

Compaction Test …

Table1. Modified compaction test (ASTM D1557)

Method A Method B Method C

Material≤ 20%

retained on sieve No.4

>20% retained on No.4 and ≤ 20%

retained on sieve 3/8”

>20% retained on sieve 3/8” and <30% retained on sieve 3/4”

Passing Sieve No.4 Sieve 3/8” Sieve 3/4”

Mold Dia. 4” 4” 6”

Layer No. 5 5 5

No. of Blow/Layer 25 25 56

116.43 mm

Ø 114.3 mm

Ø 101.6 mm

Lower Ring

Upper Ring

457 mm

Standard mold and dropped hammer (ASTM D1557)

Compaction Test (cont.)

Two types of samples are prepared as sample with water

and sample with geopolymer.

For sample with water, soil sample and water are mixed

together as a normal way.

For sample with geopolymer, fly ash and dry soil are mixed

together with a ratio FA/soil = 0.1 for five minutes. Then, the

mixture of liquid activator and water (LA/water = 0.1) is

added to soil-fly ash mixture and blending for next ten

minutes to be homogenous.

Compaction Test …

Mix design for test samples

Compaction Test …

Soil Water

Mixture with water

Sample with Water

ASTM Compaction Test

OMC & MDD

FA/Soil = 0.1 AL/Water = 0.1

Mixture with geopolymer

Sample with Geopolymer

(GP)

Compaction Test …

3

2

1

Soil mixing process take a time for almost 15 minutes to get

homogenous mixture for compaction test sample.

Silty sand compaction results between sample with water and sample with geopolymer

Sample with water

MDD – 1940 kg/m3

OMC – 7.8 %

Sample with geopolymer

MDD – 1925 kg/m3

OMC – 9.5 %

1780

1820

1860

1900

1940

1980

0 2 4 6 8 10 12 14Water content (%)

Dry

den

sity

(kg/

m3 )

Compaction Test …

High plasticity clay compaction results between sample with water and sample with geopolymer

1400

1450

1500

1550

1600

1650

0 5 10 15 20 25 30 35Water content (%)

Dry

den

sity

(kg/

m3 )

Sample with water

MDD – 1634 kg/m3

OMC – 21 %


MDD – 1571 kg/m3

OMC – 19 %

Compaction Test …

Sludge compaction results between sample with water and sample with geopolymer

900

1000

1100

1200

1300

1400

0 20 30 40 50Water content (%)

Dry

den

sity

(kg/

m3 )

6010

Sample with water

MDD – 1360 kg/m3

OMC – 26 %


MDD – 1250 kg/m3

OMC – 33 %

Compaction Test …

Soil Type Compaction Characteristic OMC (%) MDD (kg/m3)

Silty sand(SM)

Water 7.8 1940

Geopolymer 9.5 1925

High plasticityclay (CH)

Water 21 1634

Geopolymer 19 1573

Sludge(MH)

Water 26 1360

Geopolymer 32 1250

Table. Compaction parameters of three types of soils

Compaction Test …

Direct shear test

Direct shear test is the oldest and simplest form in laboratory

and it is used to measure shear strength of soil (Das, 2010).

Cohesion and friction are main parameters and they are

calculated by Mohr-Coulomb failure criterion.

f = c + n tan (3)

Where f = shear strength in failure, n = normal stress,

c = cohesion of soil, = friction angle of soil

In this study, the shear strength is measured by using three-

ring direct shear test device.

Three-ring direct shear test has an advantage to measure

shear strength after compaction without sample disturbance

due to changing mold (Sonsakul et al., 2013).

Three-ring direct shear testing device has two portions:

Three-ring compaction and shear mold

Direct shear frame

Direct shear test …

Ø107.6 mm

Ø101.6 mm

50.8 mm

50.8 mm

50.8 mm

Upper ring

Middle ring

Lower ring

Three-ring compaction and shear mold


Method A(ASTM D1557)

Three-ring Compaction (Sonsakul et al., 2013)

Material ≤ 20% retained on sieve No.4 -

Passing Sieve No.4 Under 10 mm (max. grain size)

Mold Dia. 4” 4”

Layer No. 5 6

No. of Blow/Layer 25 27

Energy 2700 kN-m/m3 2700 kN-m/m3

Table. Comparison between ASTM and Three-ring method


Three-ring direct shear testing device

Vertical Dial gauge

Normal load

Three-ring mold

Shear force load cell

Shear force dial gauge

Hydraulic hand pump


Side view of three-ring direct shear testing device

Normal force

Shear force


Three-ring direct shear test is performed to measure the

shear strength of two kinds of soil samples under two curing

condition.

As two kinds of soil samples,

sample with water and sample with geopolymer

As two curing conditions,

non-curing (0 day) and curing (7 days)


Direct shear test …ASTM Compaction Test

Three-ring Compaction

Curing (7 days) Non-curing (0 day)

Direct Shear Test

FA/Soil = 0.1 AL/Water = 0.1

Mixture with geopolymer

Sample with Geopolymer

(GP)

Water

Mixture with water

Sample with Water

Soil

OMC & MDD

The test samples for curing are under ambient temperature

(27 30C) in laboratory for 7 days before shearing.

For non-curing samples, they are sheared directly after

compacting in three-ring mold with the normal forces (0.4,

0.6, 0.8 and 1.0 MPa).

The shear displacement rate is 1 mm/min (approximately) to

be obvious different outcome in shearing soil grains.


0.0

0.4

0.8

1.2

1.6

2.0

0 1 2 3 4 5 6 7 8

She

ar s

tress

(MP

a)

Shear displacement (mm)

n = 1.0 MPa0.8 MPa0.6 MPa0.4 MPa

n = 1.0 MPa

0.0

0.4

0.8

1.2

1.6

2.0

0 1 2 3 4 5 6 7 8

She

ar s

tress

(MP

a)


0.8 MPa0.6 MPa0.4 MPa

0.0

0.4

0.8

1.2

1.6

2.0

0 1 2 3 4 5 6 7 8

She

ar s

tress

(MP

a)



0.0

0.4

0.8

1.2

1.6

2.0

0 1 2 3 4 5 6 7 8

She

ar s

tress

(MP

a)


n = 1.0 MPa0.8 MPa

0.6 MPa

0.4 MPa

Shear stresses and shear displacements of silty sand

Water (7 days)

Geopolymer (7 days)

Water (0 day)

Geopolymer (0 day)


Under shearrate

1mm/min

0.0

0.4

0.8

1.2

1.6

0 1 2 3 4 5 6 7 8

She

ar s

tress

(MP

a)



n = 1.0 MPa

0.0

0.4

0.8

1.2

1.6

0 2 4 6 8

She

ar s

tress

(MP

a)


0.8 MPa0.6 MPa0.4 MPa


0.0

0.4

0.8

1.2

1.6

0 2 4 6 8

She

ar s

tress

(MP

a)


n = 1.0 MPa

0.8 MPa0.6 MPa

0.4 MPa

0.0

0.4

0.8

1.2

1.6

0 2 4 6 8

She

ar s

tress

, MP

a

Shear displacement, mm

Shear stresses and shear displacements of sludge

Water (7 days)

Geopolymer (7 days)

Water (0 day)

Geopolymer (0 day)


Under shearrate

1mm/min

0.0

0.4

0.8

1.2

1.6

0 2 4 6 8

She

ar s

tress

(MP

a)




0.0

0.4

0.8

1.2

1.6

0 2 4 6 8

She

ar s

tress

(MP

a)


0.0

0.4

0.8

1.2

1.6

0 2 4 6 8

She

ar s

tress

(MP

a)



0.0

0.4

0.8

1.2

1.6

0 2 4 6 8

She

ar s

tress

(MP

a)



Direct shear test (cont.)

Shear stresses and shear displacements of high plasticity clay

Water (7 days)

Geopolymer (7 days)

Water (0 day)

Geopolymer (0 day)


Undershearrate

1mm/min

Curing sample with geopolymer ( 7 days )

Non-curing sample with water ( 0 day )

Sludge

High Plasticity Clay

Silty Sand

Silty Sand Sludge

High Plasticity Clay


0 5 10 in 0 5 10 in 0 5 10 in

0 5 10 in 0 5 10 in 0 5 10 in


Soil Type

Curing time

(days)

Tested samples with

Peak Residual

cp (MPa) p ( ) cr (MPa) r ( )

Silty Sand(SM)

0Water 0.20 37.8 0.11 32.5

Geopolymer 0.22 43.3 0.12 37.3

7Water 0.23 36.7 0.11 32.4

Geopolymer 0.59 51.4 0.13 45.1

Normal stress (MPa)

0.0

0.4

0.8

1.2

1.6

2.0

Res

idua

l she

ar s

tere

ngth

(MP

a)

0.0 0.8 1.0 1.20.2 0.4 0.6

-

Res - G7Res - G 0 Res - W 7Res W0

Peak -G7Peak -G0 Peak - W7

-Peak W0

0.2 0.4 0.6 0.8 1.0 1.2

Pea

k sh

ear s

treng

th (M

Pa)

Normal stress (MPa)

0.0

0.4

0.8

1.2

1.6

2.0


Soil Type

Curing time

(days)

Tested samples with

Peak Residual


Sludge(MH)

0Water 0.32 25.0 0.25 23.8

Geopolymer 0.30 27.2 0.19 26.8

7Water 0.37 25.4 0.21 23.3

Geopolymer 0.29 41.3 0.08 40.5

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Pea

k sh

ear s

treng

th (M

Pa)

Normal stress (MPa)

Peak-G7Peak-G0 Peak-W7

-Peak W0

0.0

0.4

0.8

1.2

1.6

2.0

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Res

idua

l she

ar s

treng

th (M

Pa)

Normal stress (MPa)

Res -G7Res -G0 Res -W7

-Res W0

0.0

0.4

0.8

1.2

1.6

2.0


Soil Type

Curing time

(days)

Tested samples with

Peak Residual


Clay(CH)

0Water 0.38 26.5 0.23 18.0

Geopolymer 0.17 32.4 0.21 26.2

7Water 0.48 26.2 0.14 17.4

Geopolymer 0.66 41.8 0.24 25.2

0.0

0.4

0.8

1.2

1.6

2.0

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Pea

k sh

ear s

treng

th (M

Pa)

Normal stress (MPa)

Peak - G7Peak -G0 Peak - W7

-Peak W0

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Res

idua

l she

ar s

treng

th (M

Pa)

Normal stress (MPa)

Res -G7Res -G0 Res -W7

-Res W0

0.0

0.4

0.8

1.2

1.6

2.0

Conclusions

For silty sand and sludge, the soil samples with fly ash

geopolymer are increase optimum moisture content and

decrease maximum dry density.

For high plasticity clay, fly ash geopolymer decreases

optimum moisture content corresponding with decrease of

maximum dry density.

The compaction results point out that fly ash based

geopolymer cannot improve the maximum dry density.

Conclusions …

The results of three-ring direct shear tests give higher

strengths in shearing when soil samples are mixed with

geopolymer and more higher strengths are attained through

the curing state.

After compacting with fly ash geopolymer, the soils are

attained a harden state depending upon the curing period.

Conclusions …

The more laboratory strengths based on curing period under

ambient temperature (27 – 30 C) point out that field strength

can be attained after construction because of chemical

reaction under ambient temperature in actual condition.

The short time interval of mixing process of soil samples

reflects the advantages on field condition as in-situ mixing

process can be performed as fast as possible.

Although clay soils are normally low internal friction angle,

the compacted condition with geopolymer gives higher

internal friction angle.

The geopolymer can increase the shear strength of high

plasticity clay almost double.

Conclusions …

The compacted soil mixed with geopolymer transform to

more brittle behavior in strain softening.

Fly ash based geopolymer enhances the shear strength of

soils by increasing of cohesion and friction angle.

“ Soil improvement techniques using geopolymer can be applied

for strengthening the soil embankment, soil slope and earth dam

foundation.”

Conclusions …

Recommendations for future study

The more soil specimens should be used to experimentally

perform three-ring direct shear test with various shearing

rates.

The various ratios of geopolymer and raw materials might be

performed under high ambient temperature (>30 C) and

more curing periods (>7 days).

The soil specimens may be under wet-dry cycle process

according to ASTM standard before shearing the sample in

direct shear device.

Microscopic studies as SEM and XRD may be employed

when shearing for soil specimens with geopolymer.

Recommendations for future study …

Acknowledgement

Shear strength of compacted soils using geopolymer

Engineering

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