Engineering Properties of Black cotton soil Modified … Properties of Black cotton soil Modified with Fly ash and Cement Jaya Prakash Babu.V#1, Satyanarayana.P.V.V*2, Surya Manikantha

International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 10 - May 2016

ISSN: 2231-5381 http://www.ijettjournal.org Page 477

Engineering Properties of Black cotton soil

Modified with Fly ash and Cement Jaya Prakash Babu.V

#1, Satyanarayana.P.V.V

*2, Surya Manikantha

#3 Abdul Moin

#4

#1PG Student,

#2Professor,

#3,#4PG students &Civil eng. department& Andhra University

Visakhapatnam, India

Abstract: Black cotton soil is a typical volume

change soil which loses its strength on wetting due

to increase in its volume and in absence of water it

shows multiple cracks due to decrease in its

volume. This volume change behavior causes

distress when structures located on these soils and

also these soils can be used as construction

material.. Present paper describes the strength

behavior of Black cotton soil treated with fly ash as

stabilizer. Fly ash is a fine powder obtained from

burning of coal during the production of electricity.

Disposal of Fly ash is a big problem. To minimize

the disposal of Fly ash onto large land areas, it can

be used as a construction material in civil

engineering works. In this an attempt is made for

the utilization of Fly ash in bulk quantities by

adding it to expansive soil at various percentages

of cement and tests like plasticity, swell,

compaction and CBR tests were performed. From

the test results it is identified that addition of Fly

ash and cement decreases plasticity and improves

strength characteristics. Addition 32-40% Fly ash

and 6-8% cement attains higher CBR values and

improved swell characteristics.

Key words: Expansive soil, Fly Ash,

cement, CBR

1.0 INTRODUCTION:

Black cotton soils accounts about 20% of land area

in India and are predominantly located in the

Deccan trap covering the states. Most Indian Black

cotton soils are rich in Montmorillonate, this

mineral is responsible for swell-shrink behavior of

the soil. It is highly sensitive to moisture changes;

Katti(1979)2 has given properties of Black cotton

soils which have Liquid limit 40%-100%, Plastic

limit 20%-60%, Differential Free Swell index 20%-

100%.Structures located on these soils subjected to

differential settlements due to moisture variations

(Bala Subramanyam et.al 1989)1. Hence the

subgrade and its undesirable characteristics to be

modified using a suitable stabilization technique.

Stabilization involves the methods used for

modifying the properties of a soil to improve its

engineering performance. Keeping in this view

investigation carried out with fly ash. In India,

about 120 million tonns of coal ash is produced

annually.Coal-ash management poses a serious

environmental problem for India and requires a

mission-mode approach. Disposal of wastage

requires costly land at thermal power plants and the

transport of flyash to the ash ponds entail heavy

expenditure. some researchers

P.V.V.Satyanarayana et.al (2013)11

studied on the

Strength characteristics of Expansive soil-Fly ash

mixes at various moulding water contents,Kiran

B.Biradar et.al (2014)3 studied the Influence of

steel slag and Fly ash on Strength Properties of

Clayey soil, Ramakrishnan, A.K. et.al(2001)10

Stabilization of Annamalainagar Clay with lime-

Fly ash,Nalbantoglu, Satyanarayana.P.V.V et.al

(2013)12

studied the Bulk utilization of flyash lime

sodium silicate mixes in geotechnical

applications,Satyanarayana.P.V.V et.al(2016)13

studied on the Engineering Properties of Expansive

Soil Stabilized with Fly ash and Lime Mixes,

Prabakar, J.et.al (2003)9 studied Influence of fly

ash on strength behavior of typical soils,Sridharan,

A.et.al (1998)15 studied Use of Fly ash to improve

the CBR of soil, Pandian, N.S. et.al (2002)7 studied

California bearing ratio behavior of cement

stabilized fly ash-soil mixes, Kolias, S. et.al

(2005)4 studied Stabilization of Clayey soils with

high calcium fly ash and cement, Phanikumar, B.R.

et.al (2007)8 studied Volume changes Behaviour of

fly ash-stabilized clay, Pandian, N.S. et.al (2002)6

studied The pozzolanic effect of fly ash on the CBR

behaviour of black cotton soil.

In present investigation various percentages of Fly

ash and cement mixes are added to expansive soils

and effect of these mixes was studied in terms of

plasticity, compaction, swell and strength

characteristics.

2.0. MATERIALS:

To study the performance of Fly Ash and Cement

mixes on expansive soil, which is obtained from

delta areas of Godavari River in Bhimavaram,

Andhra Pradesh, India and Fly Ash was collected

from NPTC, Parawada of Visakhapatnam

district,Andhra Pradesh, India and cement of OPC

43 grade obtained from local markets.

2.1. Black cotton soil:

http://www.ijettjournal.org/



Expansive soils in India are popularly known as

Black cotton soils. Expansive soil under study was

collected dried and pulverized into the required

sizes and tested for properties like gradation

,compaction, strength as per IS2720 and the results

are shown in table-1 and fig-1

Table.1.Geotechnical properties of Black cotton

soil

Fig-1: Gradation curve of Black Cotton soil

From the test results it is identified that it contains

fines (less than 75µm) of 95% .shows alluvial

origin out of which 40% of silt and 55% as clay

particles. The presence of fines contributed for high

liquid limit ( wL ) of 74% and plasticity index of

45% can be classified as CH soil based on IS1498

1970 It also exhibited high swelling characteristics

with FIS as 100 and swell pressure as 90kpa and

attained very low strength values under soaking in

terms of CBR as 1%.

2.2Fly ash: Fly ash was collected from National Thermal

Power Corporation (NTPC), which is located at

Parawada, Visakhapatnam, Andhra Pradesh. The

collected dried Fly Ash was subjected to various

geo-technical characterizations such as gradation,

compaction, strength, permeability etc., and the test

results are shown in table -2 and Fig 2(a),2(b)

Table 2. Geotechnical Characterizations of Fly ash

Fig-2: Gradation curve of Fly ash

Table 3. Chemical Composition of Flyash

From the test results it is identified that, it has 72%

fine particles (<75µm) and all these particles are

silt ranges. It is non-plastic and incompressible

material. It has low specific Gravity and attained

less dry Density with high Moisture Contents due

to nature of Flyash particles. From the chemical

composition it isd identified that it has less

percentage of CaO (1.74<15%) classified under

0

20

40

60

80

100

120

0.0001 0.001 0.01 0.1

% F

iner

Grain size (mm)

0

20

40

60

80

100

120

0.001 0.01 0.1 1

Fin

er (

%)

Particle size (mm)

Property Values

Gravel (%) 0

Sand (%) 4

Fines (%) 96

a) Silt 50

b) Clay 46

Liquid Limit (%) 74

Plastic Limit (%) 29

Plasticity Index (IP) 45

IS Classification CH

Optimum moisture content (OMC) (%) 26

Maximum dry density (MDD) (g/cc) 1.52

California bearing ratio (%) (CBR

Soaked) 1.0

Angle of shearing resistance (Ø)

15

Cohesion (t/m2)

10

Property Values

Gravel (%) 0

Sand (%) 28

Fines (%) 72

a. Silt (%) 72

b. Clay(%) 0

Liquid Limit (%) 28

Plastic Limit (%) NP

Specific gravity 2.1

Optimum moisture content (OMC) (%) 21

Maximum dry density (MDD) (g/cc) 1.28

California bearing ratio (CBR) (%) 4

Coefficient of uniformity (Cu) 28.89

Coefficient of curvature (Cc) 2.13

Compound Formula Percentage

SiO2 59.83

Al2O3 30.48

CaO 1.74

MgO 0.86

TiO2 6.91

V2O5 0.09

ZnO 0.09




class F flyash (ASTM) and presence of high

percentages of sio2 and Al2O3 (90%) make the

Flyash Pozzolanic with addituion of Lime, Cement

and other additives.

3.0 RESULTS AND DISCUSSIONS

3.1 Effect of Fly ash on Engineering

Properties of Expansive Soils To study the effect of Fly ash on Expansive soil,

various percentage of fly ash i.e. 0,20,…50% by dry

weight of soil were added and effectively mixed and

tested for characteristics like consistency,

compaction, CBR and swell as per IS2720,as the

results are shown in table-4 and fig-3(a)-3(e)

Table 2. Various characteristics of soil-Fly ash

mixes

Fig 3(a).Consistency limits

Fig 3(b).OMC Vs FLY ASH (%)

Fig 3. MDD Vs FLY ASH (%)

Fig 3. FSI Vs FLY ASH (%)

Fig 3. CBR Vs FLY ASH (%)

From the consistency test data, it is identified that

as the percentage of fly ash is increasing liquid

limit and plasticity index values are decreasing and

plastic limit values are increasing. This

phenomenon is continued up to 30% after it

became non-plastic. The decrease in liquid limit is

due to the decrease in diffused double layer by

replacement of clay particles by fly ash particles

and increase in plastic limit is due to the

development of shear resistance at inter particle

level and the particles in soil-fly ash matrix require

more water to mobilize for rolling.

From the compaction test data it is

identified that with increasing the percentage of fly

ash OMC values are increasing and MDD values

are decreasing. This increase in OMC values are

0

10

20

30

40

50

60

70

80

0 10 20 30 40 50

Wat

er c

onte

nt

(%)

Fly ash (%)

Liquid limit

Plastic limit

Plasticity index

25

26

27

28

29

30

31

32

0 10 20 30 40 50 60

OM

C (

%)

Fly ash (%)

OMC

1.38

1.4

1.42

1.44

1.46

1.48

1.5

1.52

1.54

0 10 20 30 40 50 60

MD

D (

g/c

c)

Fly ash (%)

MDD

0

20

40

60

80

100

120

0 10 20 30 40 50 60

FS

I

Fly ash (%)

FSI

0

1

2

3

4

5

6

7

8

0 10 20 30 40 50 60

CB

R

Fly ash (%)

CBR

FLYASH

%

WL

%

WP

%

IP

%

OMC

%

MDD

g/cc

FSI

%

CBR

%

0 74 29 45 26 1.52 100 1

10 66 30 36 27 1.5 80 2.5

20 55 32 23 28 1.48 56 4

30 40 34 6 29 1.46 30 6

40 24 NP NP 30 1.43 15 7

50 NP NP NP 31 1.4 0 6.5




due to the development of flocculated structure

which resists the compaction effort and the

particles in the soil-fly ash matrix requires more

water to mobilize and less solids occupied in the

given volume and low dry densities are also due to

nature and low specific gravity of fly ash particles

compared to clay particles.

It is also observed that with increasing

percentage of fly ash free swell values are

decreasing. At a dosage of 40% it became low

swelling and at 50% it is non-swelling. The

decrease in swelling characteristics is due to

decrease of the amount of repulsion between clay

particles due to replacement of clay by fly ash

particles.

From the test results of CBR it is identified

that as the percentage of Fly ash is increasing CBR

values are also increasing up to 40% and then

decreasing. Fly ash –Clay blend offers more

resistance compared to individual Fly ash particles

and clay particles.

3.2 Effect of Cement on Fly ash Stabilized

Expansive soil

To study the effect of Cement on

Fly ash stabilized expansive soil, various

percentage of cement i.e. 2,4,6,….10% by dry

weight of soil were added and effectively mixed

and tested for characteristics like compaction,

strength and swell as per IS2720,and the results are

shown in below.

Table.5.Various Characteristics of Lime Stabilized

Expansive soil fly ash mixes

Fig 4(a).FSI (%) Vs CEMENT (%)

Fig 4(a).OMC (%) Vs CEMENT (%)

-10

0

10

20

30

40

50

60

0 2 4 6 8 10

FS

I

CEMENT (%)

20% Fly ash

30% Fly ash

40% Fly ash

20

25

30

35

40

0 2 4 6 8 10

OM

C (

%)

CEMENT (%)

20% Fly ash

30% Fly ash

40% Fly ash

CEMENT

(%)

FLY ASH (%)

20 30 40

OMC

(%)

MDD

(g/cc)

FSI

%

CBR

%

OMC

(%)

MDD

(g/cc)

FSI

% CBR

%

OMC

(%)

MDD

(g/cc)

FSI

%

CBR

%

0 28 1.48 56 4 29 1.46 30 5 30 1.43 15 6

2 28.5 1.47 40 10 35 1.48 10 12 31.5 1.45 0 15

4 29 1.46 15 20 32 1.5 0 26 33 1.47 0 30

6 29.8 1.45 0 34 33.5 1.52 0 48 34.5 1.49 0 54

8 31 1.44 0 52 35 1.54 0 68 36 1.51 0 80

10 32 1.43 0 74 37 1.55 0 84 37.5 1.53 0 90




Fig 4(a).MDD (g/cc) Vs CEMENT (%)

Fig 4(a).CBR (%) Vs CEMENT (%)

Compaction test data shows that with

increasing the percentage of fly ash & cement OMC

values are increasing & MDD values are decreasing.

Increase in OMC values are due to increase in

cement concentration in pore water makes the

particle further flocculate and more pore water is

needed to mobilize the particle against compaction

effort and hydration of cement is also responsible.

Decrease in MDD values are due to occupation of

solids contributed less weight due to replacement of

clay particles by Fly ash particles and acceleration of

flocculated structure by cement particles.

From the test results it is also identified

that as the percentage of Fly ash and cement

increases Differential Free Swell Index values

decreases. At 4% dosage of cement with respective

to all Fly ashes the soil became non-swelling.

Addition of cement makes the soil-Fly ash matrix

move repultant against swelling due to absorption

of calcium particles on to the surface of clay

particles.

CBR test data shows the increase in

percentage of cement increases the CBR values of

soil-Fly ash matrix and attained high CBR values at

dosage of 8% of cement. Addition of cement to

soil-Fly ash blends offers more resistance against

compression is due to development of cementitious

compounds and became crystalline over a period of

time.

APPLICATIONS:

1. Addition of 40% Fly ash to Black cotton

soil attained CBR value of 7% with non-

plastic and low swelling can be used as

Sub-Grade material.

2. Addition of 4% cement and 30-40% Fly

ash to the Black cotton soil attained CBR

values 26-30% can be used as Sub-Base

material.

3. Addition of 8-10% cement and 32-40% of

Fly ash to the Black cotton soil attained

CBR value 80% can be used as Base

course material.

CONCLUSIONS:

High Expansive Black cotton soil can be

effectively utilized as a Geo technical material by

addition of 30-40% fly ash and 6-10% cement. At

these dosage of admixtures the Black cotton soil

can be behaves non-plastic and non-swelling can

reduce the problems of volume change. Bulk

utilization of Fly ash reduces its deposal problem.

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0 2 4 6 8 10

MD

D (

g/c

c0

CEMENT (%)

20% Fly ash

30% Fly ash

40% Fly ash

0102030405060708090

100

0 2 4 6 8 10

CB

R (

%)

CEMENT (%)

20% Fly ash

30% Fly ash

40% Fly ash




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Documents

Engineering Properties of Black cotton soil Modified … Properties of Black cotton soil Modified with Fly ash and Cement Jaya Prakash Babu.V#1, Satyanarayana.P.V.V*2, Surya Manikantha