This document discusses various methods for soil stabilization using locally available materials, with a focus on using fly ash. The key methods discussed are mechanical stabilization, soil-cement stabilization, soil-lime stabilization, and soil-bitumen stabilization. It provides details on factors that affect each method and suitable applications. Specifically, it describes how fly ash can be used effectively in embankments, subgrades, and various pavement layers to reduce costs while utilizing an industrial waste product.

1. Use of Locally Available Materials
and Stabilisation Technique
Dr. M.S. AMARNATH
Bangalore University
Bangalore

2. Soil Stabilization
The soil stabilization means the improvement of
stability or bearing power of the soil by the use of
controlled compaction, proportioning and/or the
addition of suitable admixture or stabilizers.
Basic Principles of Soil Stabilization….
• Evaluating the properties of given soil
• Deciding the lacking property of soil and choose
effective and economical method of soil stabilization
• Designing the Stabilized soil mix for intended stability
and durability values

3. Need for Soil Stabilization
 Limited Financial Resources to Provide a
complete network Road System to build
in conventional method
 Effective utilization of locally available
soils and other suitable stabilizing agents.
 Encouraging the use of Industrial
Wastages in building low cost construction
of roads.

4. Methods of Soil Stabilization
• Mechanical Stabilization
• Soil Cement Stabilization
• Soil Lime Stabilization
• Soil Bitumen Stabilization
• Lime Fly ash Stabilization
• Lime Fly ash Bound Macadam.

5. Mechanical Stabilization
• This method is suitable for low volume roads i.e.
Village roads in low rainfall areas.
• This method involves the correctly
proportioning of aggregates and soil,
adequately compacted to get mechanically
stable layer
• The Basic Principles of Mechanical Stabilization
are Correct Proportioning and Effective
Compaction

6. Desirable Properties of Soil-
Aggregate Mix
• Adequate Strength
• Incompressibility
• Less Changes in Volume
• Stability with Variation in water content
• Good drainage, less frost Susceptibility
• Ease of Compaction.

7. Factors Affecting Mechanical
Stabilization
 Mechanical Strength of aggregates
 Gradation
 Properties of the Soil
 Presence of Salts
 Compaction

8. Mechanical Strength
• When the soil is used in small proportion to fill
up the voids the crushing strength of aggregates
is important
Gradation
• A well graded aggregate soil mix results in a
mix with high dry density and stability values
Properties of soil
• A mix with Plasticity Index, results poor stability
under soaking conditions. Hence it is desirable to
limit the plasticity index of the soil

9. Presence of Chemicals
• Presence of Salts like Sulphates and mica
are undesirable
• Presence of Calcium Chloride is Beneficial
Compaction
• Effective Compaction is desirable to
produce high density and stability mix

10. Soil Cement Stabilization
• Soil Cement is an intimate mix of soil,
cement and water, compacted to form a
strong base course
• Cement treated or cement modified soil
refers to the compacted mix when cement is
used in small proportions to impart some
strength
• Soil Cement can be used as a sub-base or
base course for all types of Pavements

11. Factors affecting soil cement stabilization
• Soil
• Cement
• Pulverisation and Mixing
• Compaction
• Curing
• Additives

12. Soil
THE PHYSICAL PROPERTIES
• Particle Size Distribution
• Clay content
• Specific Surface
• Liquid limit and Plasticity Index
Cement
A increase in cement content generally
causes increase in strength and durability

13. Pulverisation and Mixing
• Better the Pulverisation and degree of mixing,
higher is the strength
• Presence of un pulverised dry lumps reduces
the strength
Compaction
• By increasing the amount of compaction dry
density of the mix, strength and durability also
increases

14. Curing
Adequate Moisture content is to be retained in
order to accelerate the strength
Additives
There are some additives to improve properties
• Lime
• Sodium hydroxide
• Sodium Carbonate
• Calcium Chloride

15. Design of Soil –Cement Mix
• Soil – Cement specimens are prepared with
various cement contents in constant volumes
moulds
• The compressive strength of these specimens
tested after 7 days of curing
• A graph is plotted Cement content Vs
compressive strength
• The Cement Content Corresponding to a
strength of 17.5 kg/cm2 is taken as design
cement content

16. Soil Lime Stabilization
• Soil- Lime has been widely used as a
modifier or a binder
• Soil-Lime is used as modifier in high plasticity
soils
• Soil Lime also imparts some binding action
even in granular soils

17. Soil-Lime is effectively used in Expansive
soils with high plasticity index.

18. Factors affecting Properties of Soil-Lime
Lime Content
• Generally increase in lime content causes
slight change in liquid limit and considerable
increase in Plasticity index
• The rate of increase is first rapid and then
decreases beyond a certain limit
• The point is often termed as lime fixation
point
This is considered as design lime content

19. Type of Lime
 After long curing periods all types of limes
produce same effects. However quick lime
has been found more effective than
hydrated lime
 Calcium Carbonate must be heated at
higher temperature to form Quick lime
calcium oxide( CaO)
 Calcium oxide must be slaked ( by the
addition of water) to form Hydrated lime
 Compaction
 Compaction is done at OMC and maximum
dry density.

20. Curing
• The strength of soil-lime increases with curing
period upto several years. The rate of
increase is rapid during initial period
• The humidity of the surroundings also affects
the strength
Additives
• Sodium metasilicate, Sodium hydroxide and
Sodium Sulphate are also found useful
additives

21. Soil- Bituminous Stabilization
• The Basic Principles of this stabilization are
Water Proofing and Binding
• By Water Proofing inherent strength and
other properties could be retained
• Most Commonly used materials are Cutback
and Emulsion
• Bitumen Stabilized layer may be used as
Sub-base or base course for all the roads

22. Factors affecting properties of soil-bitumen
Soil
• The particle size, shape and gradation of the
soil influence the properties of the soil-bitumen
mix.
Types of Bitumen
• Cutbacks of higher grade should be preferred
• Emulsions generally gives slightly inferior
results than Cutback.

23. Amount of Mixing
• Increasing proportion of bitumen causes a
decrease in dry density but increases the
stability after a certain bitumen content
• The optimum bitumen content for maximum
stability generally ranges from 4 to 6%
Mixing
• Improved type of mixing with low mixing period
may be preferred

24. Compaction
• Effective Compaction results higher
stability and resistance to absorb water
Additives
• Anti stripping and reactive chemical
additives have been tried to improve the
properties of the mixes
• Portland cement can also be used along
with the soil bitumen

25. Use of Locally Available
Materials in Road Construction

26. Necessity
 Scarcity of good quality
aggregates / soil for road
construction
 Production and accumulation of
different waste materials
 Disposal and environmental
problem
 Economical and gainful
utilisation

27. Limitations of Using Waste Materials
 Quality of waste is not controlled by
their manufacturers
 Characteristics of by-products vary in a
wide range
 Road construction practice is
accustomed to traditional materials of
steady quality
 Specifications of layers compaction of
traditional materials are not suitable for
waste materials

28. General Criteria for Use of Waste
Materials
 Amount of yearly produced waste
material should reach a certain lower
limit
 The hauling distance should be
acceptable
 The material should not have a
poissonous effect
 The material should be insoluble in
water
 The utilisation should not have a
pollutional effect to the environment

29. Special Requirement for Using Waste
Materials
 Free from organic matter
 Should not swell or decay as
influenced by water
 Should not be soluble in water
 Particles should be moderately
porous

30. Industrial wastes
 Thermal Power Stations
* Fly ash
* Bottom ash
* Pond ash
 Steel Plants
* Blast furnace slag
* Granulated blast furnace slag
* Steel slag

31. Utilisation of fly ash
 Thermal power - Major role in power
generation
 Indian scenario - Use of coal with high
ash content
- Negligible utilisation
of ash produced
 Bulk utilisation - Civil engineering
applications like
construction of roads
& embankments

32. Utilisation of fly ash
Can be used for construction of
Embankments and backfills
Stabilisation of subgrade and sub-base
Rigid and semi-rigid pavements
Fly ash properties vary widely, to be
characterised before use
Major constituents - oxides of silica,
aluminum, iron, calcium & magnesium
Environmentally safe material for road
construction
Possesses many favourable properties
for embankment & road construction

33. Favourable properties of fly ash
Light weight, lesser pressure on sub-soil
High shear strength
Coarser ashes have high CBR value
Pozzolanic nature, additional strength due to
self-hardening
Amenable to stabilisation
Ease of compaction
High permeability
Non plastic
Faster rate of consolidation and low
compressibility
Can be compacted using vibratory or static roller

34. Engineering properties of fly ash
Parameter Range
Specific Gravity 1.90 – 2.55
Plasticity Non plastic
Maximum dry density (gm/cc) 0.9 – 1.6
Optimum moisture content (%) 38.0 – 18.0
Cohesion (kN/m 2 ) Negligible
Angle of internal friction (j) 30 0 – 40 0
Coefficient of consolidation C v (cm 2 /sec) 1.75 x 10 -5 – 2.01 x
10 -3
Compression index C c 0.05 – 0.4
Permeability (cm/sec) 8 x 10 -6 – 7 x 10 -4
Particle size distribution (% of materials)
Clay size fraction 1 – 10
Silt size fraction 8 – 85
Sand size fraction 7 – 90
Gravel size fraction 0 – 10
Coefficient of uniformity 3.1 – 10.7

35. Differences between Indian & US fly
ashes
Property compared Indian fly ash US fly ash
Loss on ignition Less than 2 per 5 to 8 per cent
(Unburnt carbon) cent
SO 3 content 0.1 to 0.2 per 3 to 4 per cent
cent
CaO content 1 to 3 per cent 5 to 8 per cent
Increase in 3 to 4 times in 10 times or more in
concentration of comparison to comparison to source
heavy metals source coal coal
Rate of leaching Lower Higher

36. Fly ash for road embankment
 Ideally suited as backfill material for urban/
industrial areas and areas with weak sub
soils
 Higher shear strength leads to greater
stability
 Design is similar to earth embankments
 Intermediate soil layers for ease of
construction and to provide confinement
 Side slope erosion needs to be controlled by
providing soil cover
 Can be compacted under inclement weather
conditions
 15 to 20 per cent savings in construction
cost depending on lead distance

37. Fly ash for road embankment
Typical cross section of fly ash road embankment

38. Approach embankment for second
Nizamuddin bridge at Delhi
– Length of embankment - 1.8 km
– Height varies from 6 to 9 m
– Ash utilised - 1,50,000 cubic metre
– Embankment opened to traffic in 1998
– Instrumentation installed in the embankment
showed very good performance
– Approximate savings due to usage of fly ash is
about Rs.1.00 Crore

39. Approach embankment for second
Nizamuddin bridge at Delhi

40. Spreading of pond ash
Second Nizamuddin bridge approach embankment
Compaction of pond
ash

41. Stone pitching for slope
protection
Second Nizamuddin bridge approach embankment
Traffic plying on the
embankment

42. Utilisation of fly ash
Four laning work on NH-6 (Dankuni to Kolaghat)
Length of stretch – 54 km
Height of embankment – 3 to
4m
Fly ash utilisation – 2 Million
cubic metres
Water logged area
(soft ground conditions)
Compaction of fly ash over layer of
geotextile

43. Reinforced fly ash embankment
 Fly ash - better backfill material for
reinforced embankments
 Polymeric reinforcing materials –
Geogrids, friction ties, geotextiles
 Construction sequence – similar to
reinforced earth structures

44. Okhla flyover approach embankment
– First geogrid reinforced fly ash
approach embankment constructed in
the country
– Length of embankment – 59 m
– Height varied from 5.9 to 7.8 m
– Ash utilised – 2,700 cubic metre
– Opened to traffic in 1996
– Performance has been very good

45. Okhla flyover approach embankment
Filter
Facing medium Geogrids
panels
7.8 to
5.9 m
Reinforced foundation mattress of bottom ash

46. Erection of facing
panels
Okhla flyover approach embankment
Rolling of pond
ash

47. Support provided to
facing panels during
construction
Okhla flyover approach embankment
Laying of geogrids

48. Hanuman Setu flyover approach embankment
– Geogrid reinforced fly ash approach
embankment
– Length of embankment – 138.4 m
– Height varied from 3.42 m to 1.0 m
– Opened to traffic in 1997

49. Sarita Vihar flyover approach embankment
– Length of embankment – 90 m
– Maximum height – 5.25 m
– Embankment opened to traffic
in Feb 2001
– Polymeric friction ties used for
reinforcement

50. Laying of friction ties
Sarita Vihar flyover reinforced approach embankment
Arrangement of
friction ties before
laying pond ash

51. Compaction of pond
ash using static and
vibratory rollers
Sarita Vihar flyover reinforced approach embankment
Compaction using
plate vibrator near
the facing panels

52. Fly ash for road construction
 Stabilised
soil subgrade & sub-
base/base courses
– Mixing with soil reduces plasticity
characteristics of subgrade
– Addition of small percentage of lime or
cement greatly improves strength
– Leaching of lime is inhibited and
durability improves due to addition of fly
ash
– Pond ash & bottom ash can also be
stabilised
– Lime-fly ash mixture is better alternative
to moorum for construction of WBM /
WMM

53. Fly ash for road construction
 Construction of semi-rigid/ rigid
pavements
– Lime-fly ash concrete
– Dry lean cement fly ash concrete
– Roller compacted concrete
– Fly ash admixed concrete pavements
– Lime-fly ash bound macadam
– Precast block paving
– High performance concrete

54. Bituminous concrete 40
mm 100 mm
DBM
BM 75 mm
WBM Gr III/WMM 75 mm
WBM Gr II/WMM 150 mm
GSB 350 mm
Typical cross section of flexible
pavement – conventional section

55. Bituminous concrete 40 mm
DBM 100 mm
BM 75 mm
WBM Gr III/WMM 75 mm
Fly ash + 6% cement
stabilised layer 150 mm
Pond ash 350 mm
Typical cross section of flexible
pavement – using fly ash

56. Fly ash admixed PQC 300
mm
DLFC 100 mm
Pond ash 300
mm
Typical cross section of rigid pavement
– using fly ash

57. Demonstration road project
at Raichur
 Total length of the road – 1 km
 Five sections of 200 m each with different
pavement sections
 Pond ash has been used for replacing moorum
in sub-base course
 Stabilised pond ash used for replacing part of
WBM layer
 One rigid pavement section using DLFC and
RCCP technology was laid
 Performance of all the specifications is good

58. Mixing of lime
stabilised pond ash
Demonstration road project using fly ash at Raichur
Compaction of
stabilised pond ash
using road roller

59. Construction of roller
compacted concrete
pavement
Demonstration road project using fly ash at Raichur
View of the
demonstration road
stretch after three years

60. Demonstration road project using fly ash
near Dadri (U.P)
 A rural road near Dadri in District
Gautam Budh Nagar, Uttar Pradesh was
selected
 Total length of road – 1.4 km
 Bottom ash used as embankment fill
 Base course constructed using fly ash
stabilised with 8% cement
 RCCP Wearing course – 10 cm thickness
 RCCP Mix proportion – 1:2:4
 30 per cent of cement and 20 per cent of
sand replaced with fly ash in RCCP
 Shoulders – 8% cement stabilised fly ash

61. Demonstration road project using fly ash
near Dadri (U.P) – Typical section
RCCP wearing course - 0.1 m
Stabilised fly ash Stabilised fly ash
base - 0.1 m Shoulder
Soil cover
Bottom ash

62. Demonstration
road project using
fly ash near Dadri
(U.P)
Stabilised base course
Mixing & laying of RCCP Compaction of RCCP

63. IRC Guidelines / Specifications
 Guidelines available on pavement
construction
 IRC 60 ‘Tentative guidelines for use of lime
fly ash concrete as pavement base or sub-
base’
 IRC 68 ‘Tentative guidelines on cement fly
ash concrete for rigid pavement
construction’
 IRC 74 ‘Tentative guidelines for lean
cement concrete and lean cement fly ash
concrete as a pavement base or sub-base’
 IRC 88 ‘Recommended practice for lime fly
ash stabilised soil as base or sub-base in

64. Guidelines for use of fly ash in road
embankments
 Published recently by Indian Roads Congress
(SP- 58:2001)
 Includes design aspects also
 Handling and construction
– Loose layer thickness of 400 mm can be
adopted if vibratory rollers are used
– Moisture content - OMC + 2 per cent
– Use of vibratory rollers advocated
– Minimum dry density to be achieved - 95
per cent of modified Proctor density
– Ash layer and side soil cover to be
constructed simultaneously

65. Utilisation of steel slags
 Total production of slag from steel
industries is about 8.0 million tonnes
 Types of slags
– Blast furnace slag
 Granulated blast furnace slag
(GBFS)
 Air cooled slag
– Steel slag

66. Granulated blast
furnace slag
Contains reactive silica
Suitable for lime / cement
stabilisation
Air cooled blast
furnace slag
Non – reactive
Suitable for use
as coarse

67. CRRI work on utilisation of
steel slags
 Characterisation of slags produced at
different steel plants
 Laboratory studies on Lime-GBFS mixes
 Semi-field studies on Lime-GBFS
concrete
 Test track studies on usage of slags in
road works

68. Properties of air cooled slag
Property Durgapur Bhilai Rourkela Delhi Specification
Quartzite requirements
Specific 2.78 – 2.82 – 2.97 – 2.67 -
gravity 2.82 3.33 2.99
Water 1.53 – 0.58 – 0.74 – 0.48 2% Max
absorption 1.72 1.38 1.29
(%)
Los 18.80 25.00 14.28 34.00 40% Max
Angeles
abrasion
value (%)
Impact 15.79 14.80 16.90 24.50 30% Max
value (%)
Soundness 1.66 1.17 0.33 0.17 12% Max
value (%)
Percentag 46.40 43.90 43.10 43.80 -
e voids

69. Steel slags
 Obtained as a waste product during
production of steel
 Particle size varies from 80 mm to
300 microns
 Compared to blast furnace slag, steel
slag contains lower amount of silica,
higher amounts of iron oxide and
calcium oxide
 Due to presence of free lime, steel
slag should be weathered before
using it in construction

70. Road projects executed under CRRI
guidance using slags
 Plant roads at Visakhapatnam
 Test tracks in collaboration with AP
PWD using slags from
Visakhapatnam Steel Plant
 Test tracks in collaboration with
Orissa PWD using slags from
Rourkella Plant
 Test tracks at R&D Centre for Iron &
Steel, Ranchi using Slags from
Bokaro Plant

71. Construction
of test track
using slag at
Orissa
Labour based
techniques for
construction of
stabilised layer

72. Lime
stabilisation
of iron slags
(Orissa)
View of finished
surface of road
constructed
using slags at
Orissa

73. Processed municipal wastes
 Processed municipal wastes
utilised for construction of
test track on village road
near Delhi
 Stabilised municipal waste
used for construction of
sub-base layer
 Performance of stretch is
good

74. Kimberlite tailings
 Kimberlite tailings are waste produced from
diamond mining
 Can be used in base or sub-base course by
adopting mechanical or cement
stabilisation
 High value of water absorption makes them

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