Bituminous Road Construction Techniques

Transportation Engineering
CE 6014(R15)
Dr. Anitha Jacob
Lecturer in Civil Engineering
Govt. Polytechnic College, Chelakkara, Thrissur
Bituminous Road Construction

CE 6014 (R15) – Transportation Engineering
Module II
Road Construction:
Construction of bituminous road
• Flexible pavement & Rigid pavement
• Prime coat & tack coat – premix Macadam &
penetration Macadam – Seal coat
• Bituminous Macadam road maintenance using
cutback/emulsion and hot pre-mix Macadam
2

What is a pavement ?
• A structure to carry vehicle wheel load
– safely
– smoothly
– at a faster rate
– without any deformation
3

Types of Pavement
RIGID
FLEXIBLE
4

Wheel Load
Granular
structure
Load transfer mechanism
6

Comparison
Flexible
• Flexible in nature
• Grain to grain load transfer
• Multiple layers of
Subgrade, sub base, Base
course and Surface course
• Low initial cost
• High maintenance cost
• Eg. Bituminous road, WBM
Rigid
• Rigid in nature
• Load transfer by slab action
• Slab directly put over
subgrade or a sub-base
course
• High initial cost
• Low maintenance cost
• Eg. Cement Concrete road
7

BT. SURFACE
BASE
SUB - BASE
SUB – GRADE
Bituminous Pavement – Typical Cross section

Bituminous Pavement Construction
Bitumen
• Distillation of petroleum crude oil
• Hydrocarbon of high molecular weight
• Form can be gaseous, liquid, semisolid or solid
Tar
• Destructive distillation of coal or wood
• More temperature sensitive than bitumen
• Carcinogenic material
9

Adequate Viscosity
Low temperature susceptibility
Adequate affinity between
bitumen and aggregates
Properties of Bitumen
10

• Hot mix technique – Bitumen require proper
heating to attain viscosity before mixing with
aggregates
• Cold mix technique – Cutback and emulsion
do not require heating of the binder
11

General Construction Procedure
1. Formation of subgrade soil
– Soil exploration to check the dry density of soil
– For week soil up to 50 cm depth should be
replaced with good soil (2 layers of 25 cm thick is
compacted)
– Criteria –95 % of proctor density should be
achieved
– Proper longitudinal slope for drainage
– Proper camber is provided
12

General Construction Procedure (Contd)
2. Preparation of Sub-base course
– Granular Sub-Base (GSB)
• Broken stone (60 mm down), quarry dust and water
• 100 mm to 150 mm
– Wet Mix Macadam (WMM)
• Broken stone (40 mm down), quarry dust and water
• Properly mixed, laid and compacted
• 150 mm to 200 mm
Static compactors are used
13

General Construction Procedure (Contd)
3. Preparation of base course
– Prime Coat
– Tack Coat
– Bituminous Macadam
4. Preparation of wearing course
– Tack Coat
– Seal coat or Bituminous Concrete
Explained in
next slides
14

Bituminous pavement construction techniques
Interface
treatment
• Prime coat
• Tack coat
Grouted or
penetration
• Penetration
Macadam
• Built up
spray grout
Premix
pavement
• Bituminous
Macadam
• Bituminous
Concrete
• Mastic
Asphalt
Surface
dressing
• Seal coat
• Bituminous
Concrete
15

Types of bituminous construction
Interface
treatment
Prime Coat Tack Coat
16

Interface treatment
To provide necessary bond between old and new
pavement layers
a) Prime Coat
– First application of low viscosity bitumen is used
– To plug the capillary voids
– To bind loose mineral particles on the existing
porous pavement
– 24 hours curing
– Rate of application is 7.3 to 14.6 kg/10m2
17

Prime coat over WMM
Check for rate of spread
18

Interface treatment (Contd)
b) Tack Coat
– Viscous bituminous material over existing
impervious pavement surface (bituminous or CC)
– Rate of application is 4.9 to 9.8 kg/10m2
19

Interface
treatment
• Prime coat
• Tack coat
Grouted or
penetration
• Penetration
Macadam
• Built up
spray grout
Premix
pavement
• Bituminous
Macadam
• Bituminous
Concrete
• Mastic
Asphalt
Surface
dressing
• Seal coat
• Bituminous
Concrete
20

Penetration Type
Penetration Macadam
– Used as a base course
– Broken stones are dry compacted
– Hot bituminous binder is sprayed at the top
– Bitumen penetrate into the voids of aggregates
and bind the aggregates together
• Full grout and Half grout
21

Penetration Type
Built-up spray grout
– Two layers of composite construction rolled aggregates
– Each layer of compacted crushed stone is applied with
bituminous binder at a rate of 12.5 to 15 kg/m2
– After the second application of binder, key aggregates
are spread and rolled
– An initial tack coat is applied
before the first layer of coarse
aggregates
22

Interface
treatment
• Prime coat
• Tack coat
Grouted or
penetration
• Penetration
Macadam
• Built up
spray grout
Premix
pavement
• Bituminous
Macadam
• Bituminous
Concrete
• Mastic
Asphalt
Surface
dressing
• Seal coat
• Bituminous
Concrete
23

Premix pavement
Bituminous Macadam (BM)
– Used as a base course
– Crushed aggregates premixed with bitumen in a
hot mix plant at specified temperature
– Laid at hot in compacted thickness of 75 mm or 50
mm thickness
– Depending upon the gradation, it can be open
graded or semi dense BM
24

Premix pavement
Bituminous Concrete (BC)/Asphaltic Concrete
(AC)
– Used as a pavement surface course of high quality
– Mix design for a dense mixture of coarse
aggregate, fine aggregate, mineral filler and
bitumen
– 40 mm thick AC surface course for highway
pavement (IRC)
26

Premix pavement
Mastic Asphalt (MA)
– Used as a pavement surface course of high quality for
bridge deck
– Mixture of fine aggregate, mineral filler and bitumen
– Each component is heated and cooked at a
temperature of 200 to 223o C for over 5 hrs.
– On cooling, it hardens to semi-solid or solid state
– Without compaction itself an impervious surface can
be obtained
– 25 mm to 50 mm thick
28

Interface
treatment
• Prime coat
• Tack coat
Grouted or
penetration
• Penetration
Macadam
• Built up
spray grout
Premix
pavement
• Bituminous
Macadam
• Bituminous
Concrete
• Mastic
Asphalt
Surface
dressing
• Seal coat
• Bituminous
Concrete
30

Bituminous Surface Dressing (BSD)
– To provide a thin wearing coat over existing
pavement
– Application of Bituminous binder followed by
spreading of aggregate cover and rolling
• Functions
– To serve as thin wearing course
– To water proof pavement surface
– To make surface dust free
31

Bituminous Surface Dressing (BSD)
Seal Coat
– Very thin surface dressing
– Provided over an existing
black top
– 9 mm thick using 6mm stone
• Functions
– To seal the surface to prevent water ingress
– To provide skid resistant surface
32

Dumping Of Subgrade Material
33

Grading Of Subgrade Material
34

Rolling Of Subgrade Material
35

Field Density Testing Of Subgrade Material
36

Tandem
vibratory
roller
Static roller
37

Small
vibratory
roller
Plate
compactor
40

Interface
treatment
• Prime coat
• Tack coat
Grouted or
penetration
• Penetration
Macadam
• Built up
spray grout
Premix
pavement
• Bituminous
Macadam
• Bituminous
Concrete
• Mastic
Asphalt
Surface
dressing
• Seal coat
• Bituminous
Concrete
44
HOT MIX
METHODS

Cold Mix Techniques
Bituminous emulsions
• A mixture of emulsifiers and fine bitumen droplets(as
suspended particles) in water.
• Emulsifiers add charge to droplets and keeps them in
suspension
• Bitumen droplets having high affinity to aggregates,
make a quick and strong bond with aggregates, once
applied on road surface
• Water then evaporates
45

Cold Mix Techniques (Contd)
Bituminous emulsions – Types
Based on setting time
Slow setting (SS)
Medium setting (MS)
Rapid setting (RS)
Based on surface charge
Anionic Bitumen Emulsion
Cationic Bitumen Emulsion
46

Cold Mix Techniques (Contd.)
Bituminous emulsions – Advantages
• Can be used in wet weather even if it is raining.
• Eco-friendly as it is water based.
• Used in soil stabilization in desert areas.
• No need of extra heating while placing.
• No wastage in placing and laying of bitumen.
• Anti-stripping properties.
• Rapid setting type of emulsion are used in surface of roads.
• Medium setting type of emulsion are used in premixing of bitumen
emulsion and coarse aggregate.
• Slow setting type of emulsion are used with fine aggregates as the surface
area is large and requires time for uniform mixing.
47

Cutback bitumen
• Bitumen dissolved in volatile solvents of petroleum distillates like gasoline,
naptha, kerosene
• Curing time depends on type of solvent
• Quantity of solvent controls the viscosity of bitumen
• After laying, solvent get evaporated leaving behind the bitumen to bind
with the aggregate
48

Cutback bitumen – Types
Depending on the solvent used
• Rapid curing
• Medium curing
Advantage over emulsion
Compared to Emulsion, the residual percentage of bitumen is more in the
case of cutback bitumen
49

Maintenance of bituminous pavement
1. Patch Repair
Pot holes cut open to rectangular shape
Affected material removed, cleaned and recoated
with bitumen (emulsion or cutback)
Premix is filled and compacted well.
Finished level of patch is slightly higher than normal
road surface
50

2. Surface treatment
Suitable for bleeding pavement
Blotting material such as sand is spread and rolled
51

3. Resurfacing
For total damage of pavement
Additional surface course is provided
Overlay roads are provided
52

Summary
• Flexible and Rigid Pavements
• Bituminous pavements – Construction
procedure
• Maintenance of bituminous roads 53
Hot mix
Interface
Grouted
Premix
Surface
dressing
Cold mix
Emulsion Cutback

PREPARED BY :
HARSHIT PRAKASH GARG 1406800044
ANURAG MISHRA 1406800023
ANKIT KUMAR PANCHAL 1406800019
AMIT RANJAN 1406800017
GAURAV JAINER 1406800042
JAYANT 1406800050
ANIKET KUMAR SIROHI 1406800018
AGAM DAHIYA 1406800010
ASHWANI KUMAR 1406800027
MEERUT INSTITUTE OF
ENGINEERING AND TECHNOLOGY
MEERUT

TABLE OF CONTENT
PROJECT LOCATION
INTRODUCTION
TYPES OF PAVEMENT
LEVELLING
SOIL TESTS
LAYERS OF PAVEMENT
DESIGN OF A FLEXIBLE
PAVEMENT
COST & ESTIMATION
PLANT OVERVIEW

ROAD
DIMENSIONS
Total Length of Road =
750meter
Road width= 3.7meter

INTRODUCTION
What is a ROAD ?
A road is a thoroughfare, route, or
way on land between two places
that has been paved or otherwise
improved to allow travel by foot or
some form of conveyance,
including a motor vehicle, cart,
bicycle, or horse etc.
PAVEMENT
A structure consisting of
superimposed layers of processed
materials above the natural soil
subgrade, whose primary function is
to distribute the applied vehicle loads
to the sub-grade.

TYPES OF PAVEMENT
There are two types of pavement as
follows:
1.Flexible Pavements: Flexible
pavement can be defined as the
one consisting of a mixture of
asphaltic or bituminous material
and aggregates.
2. Rigid Pavements: A rigid
pavement is constructed from
cement concrete or reinforced
concrete slabs.

DIFFERENCE BETWEEN
FLEXIBLE AND RIGID
PAVEMENT

Properties Flexible Rigid
Design
Principle
Empirical method
Based on load distribution
characteristics.
Designed and
analyzed by using the
elastic
theory
Material Granular material Made of Cement
Concrete reinforced
or pre stressed
concrete
Excessive
Loading
Local depression Causes Cracks
Design
Practice
Constructed in number of
layers
Laid in slabs with
steel reinforcement
Opening to
Traffic
Road can be used for
traffic
within 24 hours
Road cannot be used
until 14 days of curing
Stress Transmits vertical and Tensile Stress and

LEVELLING
 AUTO LEVEL: An auto level is similar to the dumpy
level, with its telescope fixed to the tribrach.
For more precise leveling of the instrument a
spirit level is attached to the telescope. It is used to
measure the reduced level of any plane. Using the
formula :
Height of the Instrument = Back sight+ Reduced Level
i.e. HI = BS + RL
Here, considering BM= 100

PROPOSED METHODOLOGY
 To meet the above mentioned objectives of the present study,
following steps are adopted:
 1. We have used California Bearing Ratio Method for designing
the Flexible Pavement. With the help of this method we have
found the thickness of pavement.
 2. The Codes for designing of flexible pavement used are IRC
37:2001 – (Guidelines for the Design of Flexible), IS: 20:2007.
 3. The instruments used are Auto level, Prismatic Compass for
survey work.
 4. The Height of Instrument Method is used for leveling purpose
of the ground surface.
 5. Mid Sectional Area Method is used for Estimating the
earthwork

TESTS
 There are several types of tests which are as
follows:
1. CBR Test
2. Sieve Analysis
3. Dry Density Test
4. Bitumen Test

 DEFINITION OF C.B.R. :-
It is the ratio of force per unit area required to penetrate a
soil mass with standard circular piston at the rate of 1.25
mm/min. to that required for the corresponding
penetration of a standard material.
C.B.R. = Test load/Standard load X 100
 The same samples were further tested for CBR using Static
Compaction with 56 blows by standard rammer of 2.6 kg.
1. CBR TEST

2. Sieve Analysis
S . no Sieve
no
mm)
Wt.
Ret.
(kg)
% Wt.
Ret.
Cum %
Wt
retain
%
Passin
g
JHF
(BC)
1 19.5 0 0 0 100 100
2 13.2 .350 3.681 3.681 96.319 99.60
3 9.5 2.056 21.628 25.309 74.691 87.98
4 4.75 3.954 41.594 66.903 33.097 58.80
5 2.36 1.496 15.737 82.64 17.36 44.28
6 1.18 1.65 17.357 99.997 .003 34.48
7 Total 9.506

3. Maximum Dry Density Test
 Test pits were excavated
 Maximum dry density (MDD) corresponding optimum
moisture content (OMC) were determined using standard
compaction method and modified method in accordance
with IS:10074:1987, BIS 270 (Part-VIII)

PROPERTIES OF BITUMEN
 Bitumen is a sticky, black, and highly viscous liquid
or semi-solid form of petroleum.
 It may be found in natural deposits or may be a
refined product, and is classed as a pitch. Before the
20th century, the term asphalt was also used
 It consists chiefly high molecular weight
hydrocarbons derived from distillation of petroleum
or natural asphalt.
 Bitumen is often confused with Tar.
 Tars are resides from the destructive distillation of
organic substances such as coal, wood, or

TYPYCAL LAYERS OF FLEXIBLE
PAVEMENT

Seal Coat: The seal coat has to be provided which is
a thin surface treatment used to water-proof the
surface and to provide skid resistance.
Tack Coat: It coat is very light application of asphalt,
usually asphalt emulsion diluted with water. It must be
thin, uniformly cover the entire surface, and set very
fast.
Prime Coat: Prime coat provides bonding between
two layers which penetrates into the layer below,
plugs the voids, and forms a water tight surface.
That’s why both prime coat and tack coat has to be
provided. They both have different functions.

 Surface course
Surface course is the layer directly in contact with
traffic loads and generally contains superior quality
materials. They are usually constructed with dense
graded asphalt concrete(AC).
 Binder course
This layer provides the bulk of the asphalt concrete
structure. It's chief purpose is to distribute load to the
base course The binder course generally consists of
aggregates having less asphalt and doesn't require
quality as high as the surface course, so replacing a
part of the surface course by the binder course results
in more economical design.

 Base course
The base course is the layer of material immediately
beneath the surface of binder course and it provides
additional load distribution and contributes to the sub-
surface drainage It may be composed of crushed stone,
crushed slag, and other untreated or stabilized materials.
 Sub-Base course
The sub-base course is the layer of material beneath the
base course and the primary functions are to provide
structural support, improve drainage. A sub-base course is
not always needed or used.
 Sub-grade
The top soil or sub-grade is a layer of natural soil prepared
to receive the stresses from the layers above. It is essential
that at no time soil sub-grade is overstressed. It should be
compacted to the desirable density, near the optimum
moisture content.

Design of a Flexible Pavement:
 A Flexible Pavement of 750 meters patch is being
designed in accordance with the charts in IRC 37-2012.
With reference to the Geotechnical tests and traffic
survey performed, the important parameters and their
values are determined, & on that basis, the design of
the pavement is done.
 Though, the available width is taken as 4.5 meters, in
which the carriageway width is taken as 3.7 meters and
shoulders on the either side of the road as 1.00 meters,
and also the provision of the side drains is made as
well.

Computation of Design Traffic
 The design traffic is considered in terms of the cumulative
number of standard axles(in the lane carrying maximum traffic)
to be carried during the design life of the road. This can be
computed using the following equation:-
N = 365 x [ (1+r)n – 1] x A x D x F/r
Where,
N = Cumulative number of Standard axles to be catered in the
design in terms of use.
A = Initial traffic in the year of completion of construction in
terms of the number of commercial vehicles per day.
D = Lane distribution factor
R = Annual growth rate of commercial vehicles
F = Vehicle damage factor
N = Design life in years

Design Data
1.) According to the test results, the C.B.R. value of the
sub-grade soil is found to be =2.93 %
2.) Traffic Vehicle per Day is assumed to be 100 CVPD.
3.) Traffic growth rate, to be taken as 2%.
4.) Vehicle Damage Factor, for plain terrain = 3.5
5.) Design Life = 10 Years.
6.) Distribution Factor = 0.75
7.) Single Lane Road.

 So the Flexible Pavement thickness according to
IRC 37-2012 for 1.05 msa is 635mm.

ESTIMATION AND COSTING
S.N
o
Particulars Length
(m)
Broa
d
(m)
Depth
(m)
Quantity
(cum)
Rate
(Rs)
Amount
1 Subgrade Lime
Stabilization for
Improving
subgrade
750 4.5 0.335 1130.625 157 177,508.125
2 Granular Sub
Base with Coarse
Graded Material
750 4.5 0.225 759.375 719 545,990.625
3 Base coarse
Bituminous
Macadam
750 3.7 0.050 138.75 799 110,861.25
4 Surface coarse
Bituminous
Macadam
750 3.7 0.025 69.375 6808 472,305
5 Total Cost 13,06,665

PLANT OVERVIEW
 For the construction of bitumen concrete pavement there is
requirement of mix plant which ready the material for
laying the pavement.
Types of Plant :
1.Batch Mix Plant
2.Drum Mix Plant
We’ll use DRUM MIX PLANT for mixing the materials.

DRUM MIX PLANT
 The name of the plant is DRUM MIX 5O.
 In this there is a cylindrical drum in which mixing is done.

PARTS OF DRUM MIX
PLANT
 Water Pump
 Gathering Conveyer
 Slinger Conveyer
 Drum
 Load out Conveyer
Exhauster
Feeder
Bitumen Tank
Temperature Gun

MACHINES USED FOR THE
ROAD CONSTRUCTION
 BACK HOE LOADER

VIBRATORY ROLLER
BITUMEN SPRAYER

Construction of
Flexible Pavement
BY:
SHILPA KUMTHE FP15054
KIRAN D R FP15056
ARUN RAVINDRANATH FP15058
AJINKYA THAKRE FP15059
NATIONAL INSTITUTE OF CONSTRUCTION MANAGEMENT AND RESEARCH, PUNE.

INTRODUCTION
 PAVEMENT:-
“Pavement is load bearing and load distributary component of road”
 PURPOSE OF PAVEMENT:-
1. LOAD SUPPORT
2. SMOOTHNESS
3. DRAINAGE
4. ALL WEATHER OPERATION
5. DIRECTION AND GUIDANCE

TYPE OF PAVEMENT Type of
pavement
Flexible
pavement
Rigid
pavement
1 .FLEXIBLE PAVEMENT:
Those pavements which reflect the deformation of subgrade and the subsequent
layers to the surface.
2. RIGID PAVEMENT: The pavement are associated with rigidity or flexural strength
or slab action so the load is distributed over a wide area of subgrade soil. Rigid
pavement is laid in slabs with steel reinforcement.

FLEXIBLE PAVEMENT
 THE ADVANTAGES OF FLEXIBLE PAVEMENTS INCLUDE -
 Adaptability to stage construction
 Availability of low-cost types that can be easily built
 Ability to be easily opened and patched
 Easy to repair frost heave and settlement
 THE DISADVANTAGES INCLUDE -
 Higher maintenance costs
 Shorter life span under heavy use
 Damage by oils and certain chemicals
 Weak edges that may require curbs or edge devices

THICKNESS DESIGN
 Several Procedures are used.
 Based on volume and weight of traffic
 Load supporting capacity of soil is important.
 Heavy vehicle wheel load has greater impact.
 Traffic analysis in necessary.
 Designs are chosen based on
1) Designed traffic in terms of cumulative numbers of std. axels.
2) CBR value of subgrade.

Total thickness of pavement consists of :-
 Bituminous Surface (Wearing Course).
 Base Course.
 Subbase.
 Subgrade.

WEARING COURSE
 Three types of bituminous layers-
1. Bituminous Macadam.
2. Penetration Macadam.
3. Built up spray Grout.

 BITUMINOUS MACADAM
 It consist of crushed aggregate and bituminous binder heated and mixed
in a hot mix plant at specified temperature, transported to the
construction site, laid with a mechanical pawer and compacted by roller.
 Material used : Bitumen binder of grade VG -30,20 and Max size of
aggregate 50mm.

 BITUMINOUS PENETRASION MACADAM.
The coarse aggregate of specified size are first spread and compacted well in dry
state. Compacted thickness 50-75 mm. After compacting of dry aggregates, hot
bituminous binder of specified grade is spread in large quantity on the top of
this layer. Filling up a part of void and binding by key aggregate.
 BUILT UP SPRAY GROUT
It consist of a two layer composite construction of compacted crushed stone
aggregate with bituminous binder applied after each layer and key aggregate
placed on the top surface of the second layer.

BASE COURSE
 The base course is immediately beneath the surface course. It provides
additional load distribution and contributes to drainage and frost resistance.
Base courses are usually constructed out of
 AGGREGATES: Base courses are most typically constructed from durable
aggregates that will not be damaged by moisture and frost action.
Aggregates can be either stabilized or un-stabilized.

SUB-BASE COURSE
 Intermediate layer between subgrade and granular base
course
 Essentially a drainage layer
 Distributes the stresses imposed by traffic

FUNCTION OF SUB-BASE COURSE OF
FLEXIBLE PAVEMENT
It functions primarily as structural support but it can also help:
 Minimize the intrusion of fines from the sub-grade into the pavement
structure.
 Improve drainage.
 Minimize frost action damage.
 Provide a working platform for construction.
 The subbase generally consists of lower quality materials than the base course
but better than the sub-grade soils.

MATERIALS FOR SUB BASE
 LOCALLY AVAILABLE MATERIALS
 Natural sand
 Gravel or moorum
 Kankar
 Crushed stone
 Laterite
 INDUSTRIAL WASTE AND OTHER MATERIALS
 Steel slag
 Pond ash or Pond ash – Bottom ash mix
 Crushed concrete
 Brick bats

SUBGRADE
 It forms the foundation of the pavement system
 Subgrade soils are subjected to lower stresses than the surface, base, and
subbase courses.
 Since load stresses decrease with depth, the controlling subgrade stress
usually lies at the top of the subgrade.
 The combined thickness of subbase, base, and wearing surface must be
great enough to reduce the stresses occurring in the subgrade to values
that will not cause excessive distortion or displacement of the subgrade
soil layer.

FACTORS TO BE CONSIDERED
 General characteristics of the subgrade soils.
 Depth to bedrock.
 Depth to the water table.
 Compaction that can be attained in the subgrade.
 CBR values of uncompacted and compacted subgrades.
 Presence of weak or soft layers or organics in the subsoil.
 Susceptibility to detrimental frost action or excessive swell.

METHODS FOR SUBGRADE
PREPARATION
 COMPACTION
 In fill areas, subgrade below the top 150 mm (6 inches) is often considered
adequate if it is compacted to 90 percent relative density.
 In order to achieve these densities the subgrade must be at or near its
optimum moisture content (the moisture content at which maximum density
can be achieved).
 Usually compaction of in situ or fill subgrade will result in adequate
structural support.

 STABILIZATION
 The binding characteristics of these materials generally increase subgrade
load-bearing capacity.
 Typically, lime is used with highly plastic soils (plasticity index greater than
10), cement is used with less plastic soils (plasticity index less than 10) and
emulsified asphalt can be used with sandy soils.
 For flexible pavements, a primecoat is not effective on silty clay or clay
soils because the material cannot be absorbed into such a fine soil (TRB,
2000).

 OVER-EXCAVATION
 The general principle is to replace poor load-bearing in situ subgrade with
better load-bearing fill.
 Typically, 0.3 – 0.6 m (1 – 2 ft.) of poor soil may be excavated and replaced
with better load-bearing fill such as gravel borrow.

CONSTRUCTION STEPS
1. Preparation of Base
2. Provision of lateral confinement of aggregates
3. Preparation of Mix
4. for small quantity concrete mixer may be used
5. find OMC after replacing retained on 22.4 mm with material 4.75 to 22.4
mm
6. Spreading of Mix
 Spreading of mix to be done uniformly / evenly
 Should not be dumped in heaps

 Finishing by Paver /exceptional cases grader
 Due importance for segregation
7. Compaction
 8to 10 tonne static compactor up to 100 mm
 8-10 vibratory roller up to 200 mm
 Speed of compactor not to exceed 5 km/hour
 Displacement occurring due to roller operations are to be rectified
 Use small compactors near kerb/places not assessable to roller
 Rolling not be done when subgrade is soft/yielding/causes wave like
motion

8. Any defections on the surface to be rectified
9. Setting and Drying
10. Opening to traffic after sealing

FLEXIBLE PAVEMENT
THEORY AND DESIGN
Guide : Dr. Shashikant Sharma,
Assistant prof. Civil engineering department.
NATIONAL INSTITUTE OF TECHNOLOGY, HAMIRPUR
DEPT. OF CIVIL ENGINEERING, 2016

THEORY OF
FLEXIBLE PAVEMENT :
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Presented by:
 Md. Taiyab Jawed (16M144)
 Pawan Kumar (16M145)
 Gyandeep Singh Arya (16M146)

What is pavement ?
 A structure consisting of superimposed layers of
processed materials above the natural soil sub-
grade, whose primary function is to distribute the
applied vehicle loads to the sub-grade.
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Types of Pavement
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PAVEMENT
FLEXIBLE PAVEMENT RIGID PAVEMENT

Flexible pavement:
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 Flexible pavements are those which on a whole have
low or negligible flexural strength and rather flexible
in their structural action under load.

Load transfer:
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 Load is transferred to the lower layer by grain to
grain distribution as shown in the figure given below;

Load Transfer (continue …)
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 The wheel load acting on the pavement will be
distributed to a wider area, and the stress decreases
with the depth. Flexible pavement layers reflect the
deformation of the lower layers on to the surface
layer

TYPICAL LAYERS OF A FLEXIBLE
PAVEMENT :
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 Typical layers of a conventional flexible pavement
includes seal coat, surface course, tack coat, binder
course, prime coat, base course, sub-base course,
compacted sub-grade, and natural sub-grade.

PAVEMENT
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 Seal coat is a thin surface treatment used to water-
proof the surface and to provide skid resistance.
 Tack coat is a very light application of asphalt
emulsion diluted with water. And It provides bonding
between two layers of binder course.
 Prime coat is an application of low viscous cutback
bitumen to an absorbent surface like granular bases
on which binder layer is placed and provides
bonding between two layers.

PAVEMENT (Continue ….)
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 Surface course is the layer directly in contact with
traffic loads and are constructed with dense graded
asphalt concrete.
 Binder course purpose is to distribute load to the
base course. Binder course requires lesser quality of
mix as compared to course above it.
 Base course provides additional load distribution
and contributes to the sub-surface drainage

PAVEMENT (Continue ….)
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 Sub-base course the primary functions are to
provide structural support, improve drainage, and
reduce the intrusion of fines from the sub-grade in
the pavement structure
 Sub-grade The top soil or sub-grade is a layer of
natural soil prepared to receive the stresses from the
layers above

FACTORS AFFECTING PAVEMENT DESIGN
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 1. Design Wheel Load
 Max. Wheel load
 Axle configuration
 Contact pressure
 ESWL.
 Repetition of loads
 2. Climatic Factor
 3. Pavement component material

Design Wheel Load.
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 Max. Wheel load - It is used to determine the depth
of the pavement required to ensure that the
subgrade soil does not fail.
 Contact pressure - It determines the contact area and the
contact pressure between the wheel and the pavement
surface. For simplicity elliptical contact area is consider to
be circular.

Design Wheel Load (Continue)
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 Axle configuration - the axle configuration is important to
know the way in which the load is applied on the pavement
surface.

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 Equivalent single wheel load (ESWL)

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 Repetition of loads :
 Each load application causes some deformation and the
total deformation is the summation of all these.
 Although the pavement deformation due to single axle
load is very small, the cumulative effect of number of load
repetition is significant.
 Therefore, modern design is based on total number of
standard axle load (usually 80 KN single axle)

Climatic Factor
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 1. Temperature -
 Wide temperature variations may cause damaging
effects.
 Pavement becomes soft in hot weather and brittle in very
cold weather.
 2. Variation in moisture condition –
 It depends on type of the pavement, type of soil type,
ground water variation etc.
 It can be controlled by providing suitable surface and sub-
surface drainage.

Characteristic of Pavement material
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 1. California bearing ratio- It determines the strength
of soil sub-grade, sub-base or base and it is used for
the design of pavement.
 2. Elastic modulus -It measures the materials
resistance to being deformed elastically upon
application of the wheel load.
 3. Poisson Ratio – It is the ratio of lateral strain to the
axial strain caused by a load parallel axis along axial
strain.
 4. Resilient modulus- The elastic modulus based on
the recoverable strain under repeated loads is called
the resilient modulus MR =σd/σr .

Characteristic of Pavement material
(Continue ….)
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 The following material properties are consider for
both flexible and rigid pavements.
 When pavements are considered as linear elastic, the
elastic moduli and poisson ratio are specified.
 If the elastic modulus of a material varies with the time of
loading, then the resilient modulus is selected.

Design procedures for flexible pavements:
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Design Procedures
Empirical Design
Mechanistic-
Empirical Design
Mechanistic
Design
IRC:37-2012 is based on Mechanistic-Empirical
Design

Mechanistic-empirical design
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 1. It can be used for both existing pavement
rehabilitation and new pavement construction
 2. It can accommodate changing load types
 3. It uses material proportion that relates
better with actual pavement performance
 4. It provides more reliable performance
predictions

Failures of flexible pavements:
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 Different types of failure encountered in flexible
pavements are as follow.
 1. Alligator cracking or Map cracking (Fatigue)
 2. Consolidation of pavement layers (Rutting)
 3. Shear failure cracking
 4. Longitudinal cracking
 5. Frost heaving
 6. Lack of binding to the lower course
 7. Reflection cracking
 8. Formation of waves and corrugation
 9. Bleeding
 10. Pumping

1. ALLIGATOR OR MAP CRACKING
(FATIGUE CRACKING)
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 Followings are the primary causes of
this type of failure.
 Relative movement of pavement
layer material
 Repeated application of heavy
wheel loads
 Swelling or shrinkage of subgrade
or other layers due to moisture
variation

2. CONSOLIDATION OF PAVEMENT
LAYERS (RUTTING)
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 Formation of ruts falls in this
type of failure.
 A rut is a depression or
groove worn into a road by
the travel of wheels.
 This type of failure is caused
due to following reasons.
 •Repeated application of
load along the same
wheel path resulting
longitudinal ruts.
 •Wearing of the surface
course along the wheel
path resulting shallow
ruts.

3. SHEAR FAILURE CRACKING:
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 Shear failure causes
upheaval of pavement
material by forming a
fracture or cracking.
 Followings are the primary
causes of shear failure
cracking.
 •Excessive wheel loading
 •Low shearing resistance of
pavement mixture

4. LONGITUDINAL CRACKING:
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 This types of cracks extents to the
full thickness of pavement.
 The following are the primary
causes of longitudinal cracking.
 Differential volume changes in
subgrade soil
 Settlement of fill materials
 Sliding of side slopes

5. FROST HEAVING:
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 Frost heaving causes
upheaval of localized
portion of a pavement.
The extent of frost
heaving depends upon
the ground water table
and climatic condition.

6. LACK OF BINDING WITH LOWER LAYER
(POTHOLES & SLIPPAGE)
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 When there is lack of
binding between surface
course and underlying
layer, some portion of
surface course looses up
materials creating patches
and potholes.
 Slippage cracking is one
form of this type of failure.
 Lack of prime coat or tack
coat in between two layers
is the primary reason
behind this type of failure.

7. REFLECTION CRACKING:
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 This type of failure
occurs, when
bituminous surface
course is laid over the
existing cement
concrete pavement
with some cracks. This
crack is reflected in
the same pattern on
bituminous surface.

8. FORMATION OF WAVES &
CORRUGATION :
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 Transverse
undulations appear
at regular intervals
due to the unstable
surface course
caused by stop-and-
go traffic.

9. BLEEDING:
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 Excess bituminous
binder occurring on the
pavement surface
causes bleeding.
Bleeding causes a shiny,
glass-like, reflective
surface that may be
tacky to the touch.
Usually found in the
wheel paths.

10. PUMPING:
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 Seeping or ejection
of water and fines
from beneath the
pavement through
cracks is called
pumping

FAILURES OF FLEXIBLE PAVEMENTS
DESIGN CONSIDERATION:
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 The design of flexible pavement as per IRC is
based on two major failure that are, fatigue
cracking and rutting failure.

IRC METHOD OF DESIGN OF FLEXIBLE
PAVEMENTS (IRC: 37-2012)
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 1. IRC:37-1970
 based on California Bearing Ratio (CBR) of subgrade
 Traffic in terms of commercial vehicles (more than 3
tonnes laden weight)
 2. IRC:37-1984
 based on California Bearing Ratio (CBR) of subgrade
 Design traffic was considered in terms of cumulative
number of equivalent standard axle load of 80 kN in
millions of standard axles (msa)
 Design charts were provided for traffic up to 30 msa using
an empirical approach.
 .

Continue ….
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 3. IRC:37-2001
 based on Mechanistic-Empirical method
 Pavements were required to be designed for traffic as
high as 150 msa.
 The limiting rutting is recommended as 20 mm in 20 per
cent of the length for design traffic
 4. IRC:37-2012
 based on Mechanistic-Empirical method
 The limiting rutting is recommended as 20 mm in 20 per
cent of the length for design traffic up to 30 msa and 10
per cent of the length for the design traffic beyond

Guidelines for Design by IRC: 37: 2012
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 Design Traffic:
 The recommended method considers design traffic
in terms of the cumulative number of standard axles
(80 kN) to be carried by the pavement during the
design life.
 Only the number of commercial vehicles having
gross vehicle weight of 30 kN or more and their axle-
loading is considered for the purpose of design of
pavement.
 Assessment of the present day average traffic
should be based on seven-day-24-hour count made
in accordance with IRC: 9-1972 "Traffic Census on
Non-Urban Roads".

Traffic growth rate (r):
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 Estimated by Analyzing:
 The past trends of traffic growth,
 Change in demand of Traffic by factors like specific
development, Land use changes etc.
 If the data for the annual growth rate of commercial
vehicles is not available or if it is less than 5 per
cent, a growth rate of 5 per cent should be used
(IRC:SP:84-2009).

Design life (n)
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 The design life is defined in terms of the cumulative
number of standard axles in msa that can be carried
before a major strengthening, rehabilitation or
capacity augmentation of the pavement is
necessary.
 Depending upon road type, Design traffic is ranges
from 10 to 15 years.

Vehicle damage factor (VDF)
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 It is defined as equivalent number of standard axles
per commercial vehicle.
 The Vehicle Damage Factor (VDF) is a multiplier to
convert the number of commercial vehicles of
different axle loads and axle configuration into the
number of repetitions of standard axle load of
magnitude 80 kN.


Sample Size for Axle Load Survey:
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Lane distribution factor
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 Distribution of commercial traffic in each direction
and in each lane is required for determining the total
equivalent standard axle load applications to be
considered in the design.
 In the absence of adequate and conclusive data, the
following distribution may be assumed until more
reliable data on placement of commercial vehicles
on the carriageway lanes are available:

Lane distribution calculation:
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 1) Single-lane roads:
 2) Two-lane single carriageway roads:
 3) Four-lane single carriageway roads:
 4) Dual carriageway roads:

Computation of Design traffic:
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 The design traffic in terms of the cumulative number
of standard axles to be carried during the design life
of the road should be computed using the following
equation:

Sub-grade
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 Requirements of CBR: Sub grade is made up of in-
situ material, select soil or stabilized soil.
 Compacted to a minimum of 97% of laboratory dry
density achieved with heavy compaction.
 Minimum CBR of 8% for traffic > 450 CVPD
 CBR can also be determined from Dynamic Cone
Penetrometer (60º cone) by ..
 Log10 CBR = 2.465-1.12log10 N
 Where, N = mm/blow

Sub-grade (Continue…)
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 Where different types of soils are used in sub grade
minimum 6 to 8 average value for each type is required.
 90th percentile for high volume and 80th percentile for
other category of road is adopted as design CBR .
 Maximum permissible variation
 Where variation is more average CBR should be average
of 6 samples and not three.

Effective CBR
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 Where there is significant difference between the
CBRs of the select sub grade and embankment
soils, the design should be based on effective CBR.
The effective CBR of the subgrade can be
determined from Fig.

Lab procedure for CBR calculation:
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 The test must always be performed on remoulded
samples of soils in the laboratory.
 The pavement thickness should be based on 4-day
soaked CBR value of the soil, remoulded at
placement density and moisture content ascertained
from the compaction curve.
 In areas with rainfall less than 1000 mm, four day
soaking is too severe a condition for well protected
sub-grade with thick bituminous layer and the
strength of the sub-grade soil may be
underestimated.

Continue ….
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 If data is available for moisture variation in the
existing in-service pavements of a region in different
seasons, molding moisture content for the CBR test
can be based on field data.
 Wherever possible the test specimens should be
prepared by static compaction. Alternatively dynamic
compaction may also be used.

Resilient Modulus:
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 Resilient modulus is the measure of its elastic
behavior determined from recoverable deformation
in the laboratory tests.
 The modulus is an important parameter for design
and the performance of a pavement.
 The relation between resilient modulus and the
effective CBR is given as:

Continue ….
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 The CBR of the sub-grade should be determined as
per IS: 2720 (Part 16) (36) at the most critical
moisture conditions likely to occur at site.

Principle of pavement design:
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 Pavement Model:
 Modeled as linear elastic
multilayer structure.
 Stress Analysis is based on
IITPave software
 Critical parameters for
analysis are
 1. Tensile strain at the bottom
of bituminous layer
 2. Vertical sub-grade strain at
the top of sub-grade.
 Failure of pavement is
considered due to cracking
and rutting

Check for Fatigue:
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 Micro cracks at the bottom of bituminous layer are
developed with every load repetition
 These cracks goes on expending till they propagate
to the surface due to the large load repetition
 In these guidelines, cracking in 20 per cent area has
been considered for traffic up to 30 msa and 10 per
cent for traffic beyond that.

Check for Fatigue (Continue….)
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 Two fatigue equations developed based on
performance data collected during various study are
 Nf= 2.21 * 10-04x [1/εt]3.89* [1/MR]0.854 (80 %
reliability)…(a)
 Nf= 0.711 * 10-04x [1/εt]3.89* [1/MR]0.854 (90 %
reliability)...(b)
 Where,
 Nf= fatigue life in number of standard axles,
 εt= Maximum Tensile strain at the bottom of the
bituminous layer, and
 MR= resilient modulus of the bituminous layer.
 Equation for 90% reliability implies that only 10% of
the pavement area will have more than 20% cracks.

Check for Fatigue (Continue….)
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 To consider the effect of volume of the bitumen and air
voids equation (b) is modified as follows
 Nf =0.5161 * C * 10-04 x [1/ εt]3.89 * [1/MR]0.854………(c)
 Va= per cent volume of air void and Vb= per cent volume
of bitumen in a given volume of bituminous mix.
 Nf= fatigue life, єt= maximum tensile strain at the bottom
of DBM.
 MR= Resilient modulus of bituminous mix.
 For traffic < 30 msa consider equation (a); For traffic >
30msa equation (c) is recommened.

Check for Rutting:
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 Rutting is the permanent deformation in pavement
usually occurring longitudinally along the wheel path.
 Causes –
 1. Deformation in sub grade /non-bituminous layer
 2. Secondary compaction and shear deformation of
bituminous layer
 Limiting value
 20 mm in 20% length for upto 30 msa
 20 mm in 10% length for > 30 msa
 Rutting affects the serviceability of pavement.

Rutting (Continue …)
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 Based on various studies the two equation develops
are;
 N = 4.1656 x 10-08[1/εv]4.5337 (80 per cent reliability)
 N = 1.41x 10-8x [1/εv]4.5337 (90 per cent reliability)
 Where,
 N = Number of cumulative standard axles, and
 εv= Vertical strain in the sub-grade

Pavement composition as per IRC:
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 A flexible pavement covered in these guidelines
consists of different layers as shown in figure;

SUB-BASE LAYER
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 UNBOUND SUB-BASE LAYER
 Sub-base materials may consist of natural sand,
moorum, gravel, laterite, kankar, brick metal,
crushed stone, crushed slag
 Sub-base materials passing 425 micron sieve when
tested in accordance with IS:2720 (Part 5) should
have liquid limit and plasticity index of not more than
25 and 6 respectively.

SUB-BASE LAYER(Unbound SB Continue…)
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 When coarse graded sub-base is used as a drainage
layer, Los Angeles abrasion < 40
 Required permeability; fines passing 0.075 mm
should be less than 2 per cent.
 Sub-base is constructed in two layers, the lower
layer forms the separation/filter layer to prevent
intrusion of subgrade soil into the pavement and the
upper GSB forms the drainage layer to drain away
any water
 Resilient modulus (MR) for granular sub-base
 MRgsb = 0.2 h0.45 * MR subgrade
 Where, h = thickness of sub-base layer in mm

SUB-BASE LAYER
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 Bound Sub base
 Material for bound sub-base may consist of soil,
aggregate or soil aggregate mixture modified with
chemical stabilizers such as cement, lime-flyash.
 The drainage layer of the sub-base may consist of
coarse graded aggregates bound with about 2 per
cent cement while retaining the permeability.
 Drainage and separation layers are essential when
water is likely to enter into pavements from the
shoulder, median or through the cracks in surface
layer.

SUB-BASE LAYER(Unbound SB Continue…)
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 Strength Parameter:
 Elastic Modulus E of bound sub-bases is
 Ecgsb = 1000 * UCS
 Where UCS = 28 day strength of the
cementitious granular material

BASE LAYER
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 UNBOUND BASE LAYER
 Base layer may consist of wet mix macadam, water
bound macadam, crusher run macadam, reclaimed
concrete etc.
 Resilient modulus of the granular base is given as..
 MR granular = 0.2 * h0.45 MR subgrade
 Where h = thickness of granular sub-base and base,
mm
 Poisson's ratio of granular bases and sub-bases
is recommended as 0.35.

BASE LAYER(Continue..)
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 CEMENTITIOUS BASES :
 Cemented base layers may consist of aggregates or
soils or both stabilized with chemical stabilizers, to
give a minimum strength of 4.5 to 7 MPa in 7/28
days.
 Default values of modulus of rupture are
recommended for cementitious bases (MEPDG).
 Cementitious stabilized aggregates - 1.40 MPa
 Lime—flyash-soil - 1.05 MPa
 Soil cement - 0.70 MPa
 Poisson's ration of the cemented layers may be
taken as 0.25.

Criteria for selecting Bitumen grade.
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 The recommended resilient modulus values of the
bituminous materials with different binders are:

Continue …..
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 The Poisson’s ratio of bituminous layer depends upon the
pavement temperature and a value of 0.35 is
recommended for temperature up to 35°C and value of
0.50 for higher temperatures.
 Higher viscosity of bituminous binders, which can be
achieved either by using higher viscosity grade bitumen
or modified bitumen will improve both fatigue and rutting
behavior of mixes as compared to mixes with normal
bitumen.
 Fatigue equation at any pavement temperature from
20°C to 40°C can be evaluated by substituting the
appropriate value of the resilient modulus of the
bituminous mix, air void and volume of bitumen.
Catalogue of designs has been worked out for a
temperature of 35°C.

Drainage Layer
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 Improvement of drainage can significantly reduce the
magnitude of seasonal heave. The desirable
requirements are:
 (a). Provision must be made for the lateral drainage of the
pavement structural section. The granular sub-base/base
should accordingly be extended across the shoulders
 (b). No standing water should be allowed on either side of
the road embankment.
 (c). A minimum height of1 m between the subgrade level
and the highest water level

Drainage Layer(Continue…)
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 Some typical drainage system is illustrated in
following Figs….
 Fig.1 Pavement along a Slope

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 Fig. 2 Pavement with Filter and Drainage Layers

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 Criteria to be satisfied:
 The filter/separation layer should satisfy the following
criteria:
 To prevent entry of soil particles into the drainage layer:
 D85 means the size of sieve that allows 85 per cent by
weight of the material to pass through it.
 Similar is the meaning of D50 and D15.

DESIGN OF
FLEXIBLE PAVEMENT :
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Presented by:
 Aditya Upadhya (16M150)
 Aniruddha Chopadekar (16M151)
 Samarth Bhatia (16M152)

What is design ?
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 Design of pavement includes deciding
the number of layers, its composition and
thickness for selected material, to
support traffic load safely without failure.

Various cases in design.
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 The flexible pavement with different combinations of
traffic loads and material properties.
 1) Granular base and Granular sub-base.
 2) Cementitious base and sub-base with agg.
Interlayer.
 3) Cementitious base and sub-base with SAMI.
 4) RAP agg. Over cemented sub-base
 5) Cemented base and Granular sub-base

Problem statement.
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 Design the pavement for construction of a
new flexible pavement with the following data:
 Four lanes divided National Highway.
 Design life is 15 years.

Data collection
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 Material properties :
 California Bearing Ratio (CBR)
 Resilient Modulus (MR)
 Modulus of Elasticity (E)
 Poisson’s ratio (µ)

Material properties
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 CBR : The CBR values are calculated after
every kilometre on selected stretch of 10 km
having the same type of soil. Suppose the
values obtained are: 3.8, 2.8, 4.5, 3.9, 4.2, 2.9,
4.7, 4.3, 4.0 and 4.6%. Based on the
collected data the design CBR (90th percentile
CBR) is calculated as below:

Solution :
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 Arrange in ascending order : 2.8, 2.9, 3.8, 3.9, 4.0,
4.2, 4.3, 4.5, 4.6 and 4.7.
 Calculate the percentage greater than equal of the
value as follows:
 For CBR of 3.8, percentage of values greater than
equal to 3.8 = (8/10) x100 = 80%
 Similarly for 2.8 % is 100%, 4.5% CBR is 80% and
so on.
 Now a plot is made between Percentages of values
greater than equal to the CBR values versus the
CBR as follows.

Continue …
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RESULT : The 90th Percentile CBR value is 2.90%

Effective CBR:
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 (Figure 5.1, Page 11, IRC: 37: 2012)

Poisson’s ratio
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 Poisson’s ratio µ is define as the ratio of lateral strain
(ɛl) to the axial strain (ɛa), caused by load parallel to
the axis along which ɛa is measured.
 It is found that for most of the pavement structures,
the influence of µ value is normally small.
 For most of cement treated materials (soil cement,
cement treated base, lean concrete and PCC), the
value of µ normally lies between 0.10 and 0.25.
 Unbound granular material lie between 0.2 and 0.5
and those for bituminous mixes range from 0.35 to
0.50

Elastic modulus
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 Elastic moduli of various pavement materials
are obtained either through tests or through
the recommendations available in the
guidelines.
 Repeated flexure or indirect tensile tests are
carried out to determine the dynamic modulus
Ed of bituminous mixes.

Resilient modulus
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 Resilient modulus is the measure of its elastic
behaviour determined from recoverable deformation
in the laboratory tests.
 The behaviour of the subgrade is essentially elastic
under the transient traffic loading with negligible
permanent deformation in a single pass.
 This can be determined in the laboratory by
conducting tests.

Calculation of MR for Sub-grade.
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 The resilient modulus is calculated as follow;
 MR (Mpa) = 10 x CBR …………. For CBR 5
= 17.6 x CBR0.64 ………For CBR > 5
 (From equation 5.2, Page no. 12, IRC: 37: 2012)

Calculation of MR for Granular base and
sub-base.
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 The resilient modulus is calculated as follow;
 MRgsb = 0.20 x h0.45 x MR subgrade
 h = Thickness of sub-base layer in mm, …… sub-
base,
 = Cumulative thickness of Base layer and Sub-
base layer in mm ... for base

Traffic count
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 Assessment of average daily traffic should be normally
based on 7 day-24hr count made in accordance with
IRC: 9 “Traffic census on non-urban roads”.
 Classify traffic into different categories such as two
wheelers, three wheelers, passenger cars, trucks etc.
 But only commercial vehicle with laden weight > 3 tonne
is taken into consideration of design.
 Commercial vehicles are further categorised as single
axle single wheel, single axel dual wheel, Tandem axle
dual wheel and Tridem axle dual wheel.
 Where no traffic count data is available, data from roads
of similar classification and importance may be used to
predict the design traffic

Calculation of Design factor
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 1) Design Traffic,
 2) Axle load survey,
 3) Vehicle Damage Factor
 4) Lane Distribution Factor

Design Traffic:
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 Initial traffic after construction in terms of number of
Commercial Vehicles per day (CVPD).
 Traffic growth rate during the design life in
percentage.
 Design life in number of years.
 Spectrum of axle loads.
 Vehicle Damage Factor (VDF).
 Distribution of commercial traffic over the
carriageway.

Calculation of Design traffic:
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 For our case the number of heavy commercial vehicle
per day is taken as 7 day average for 24 hour count
comes to be 2792 vehicle per day as per the last count.
 i. e. P = 2792 cvpd, r = 7 %, and x = 10 years
 A = 2792 (1+0.07)10 = 5000 cvpd.
 RESULT: Traffic in the year of completion of construction
is 5000 cvpd in both the directions.

Axle load survey :
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 Required for VDF calculation and Fatigue damage
analysis of cementitious base.
 The axle load spectrum is formulated by considering
10 kN, 20 kN and 30 kN intervals for single, tandem
and tridem axle respectively.
 RESULT: As per study the percentage of Single,
Tandom and Tridom axle are 45%, 45% and 10%
respectively

Axle load spectrum
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Single Axle Load Tandem Axle Load Tridem Axle Load
Axle load Class
(KN)
Percentage of
Axles
Axle load Class
(KN)
Percentage of
Axles
Axle load Class
(KN)
Percentage of
Axles
185-195 0.64 390-410 1.85 585-615 1.40
175-185 0.80 370-390 2.03 555-585 1.60
165-175 0.80 350-370 2.03 525-555 1.60
155-165 2.58 330-350 2.08 495-525 1.80
145-155 2.58 310-330 2.08 465-495 1.80
135-145 5.80 290-310 4.17 435-465 4.40
125-135 5.80 270-290 4.17 405-435 4.40
115-125 11.82 250-270 12.67 375-405 13.10
105-115 11.82 230-250 12.67 345-375 13.10
95-105 12.90 210-230 10.45 315-345 10.90
85-95 12.16 190-210 10.45 285-315 10.40
< 85 32.30 170-190 7.05 255-285 7.15
<170 28.28 <255 28.33
Total 100 100 100

Vehicle damage factor
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 The formula to calculate VDF is given as follows:
 W1, W2, ….. are the mean values of the various axle load
groups.
 V1, V2, …. are the respective traffic volumes.
 Ws is the standard axle load.
 Standard axle load for Single axle, Tandem axle and
Tridem axle is 80 KN, 148 KN and 224 KN as per
IRC: 37:2012 (Page 7)
 RESULT: The VDF for Single axle load, Tandem axle
load and Tridem axle load is 4.11, 8.37 and 7.51.

Vehicle Damage factor (Continue.)
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 Were sufficient information on axle loads are not
available or the small size of project does not
warrant an axle load survey the default values of
VDF may be adopted as given in the table given
below.

Lane distribution factor.
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 Distribution of commercial traffic in each direction
and in each lane is required for determining the total
equivalent standard axle load applications to be
considered in the design.
 Single lane road : Total vehicle in both direction.
 Two lane single carriage way : 50% of total vehicle in
both direction.
 Four lane single carriage way : 40% of total vehicle
in both direction.
 Dual carriage way: Two lane 75%, Three lane 60%,
Four lane 45% of number of CV in each direction.

Lane distribution factor (Continue….)
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 RESULT: In the present design problem we are
given to design a four lane divided highway,
therefore the Lane distribution factor is 75 percent of
number of commercial vehicle in each direction.

Million standard axle
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 The design traffic is calculated in terms of cumulative
number of standard axle of 80 kN carried during the
design life of the road.
 r = 7.5 %,
 n = 20 yr. ( Expressway and Urban roads), 15 yr (NH
and SH), In this problem we have to design National
highway take n as 15 years,
 A is 5000cvpd in both direction and 2500 in one
direction

Calculation of Million std. axle.
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 Single axle load (N1): 45 percent vehicles are of single
axle.
A : 0.45 x 2500 = 1125, F : 4.11
N1 = 33.06 x 106 = 33.06 msa
 Tandem axle load (N2): 45 percent vehicles are of
tandem axle.
A : 0.45 x 2500 = 1125, F : 8. 37
N2 = 67.33 x 106 = 67.33 msa
 Tridem axle load (N3): 10 percent vehicles are of tridem
axle.
A : 0.10 x 2500 = 250, F : 7.51

Calculation of Million std. axle. (Continue…)
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 Total msa (N1+N2+N3)
 = 33.06 + 67.33 + 13.42
= 113.81 ̴ 150 msa (Aprox.)
 RESULT: The cumulative million standard axles to
be consider for design is 150 msa.

Determination pavement thickness
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 Case 1 : Bituminous pavement with untreated
granular layer

Determination of thickness for Case 1
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 The thickness of various layers is determined with
the help pavement design catalogue given in IRC:
37: 2012 from page 26 to 28, for various values of
effective CBR.

(Continue ….)
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 RESULT:
 For design traffic of 150msa and CBR of 7%
 Thickness of subbase (GSB) is 230 mm,
 Thickness of base (G. Base) is 250 mm,
 Thickness of Dense Bitumen macadam (DBM) is 140
mm,
 Thickness of Bituminous concrete (BC) is 50 mm

Case 2 : Bituminous pavement with
cemented base and cemented sub-base
with aggregate inter layer of 100mm
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Determination of thickness for case 2.
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 RESULT:
 For design traffic of 150msa and CBR of 7%
 Thickness of Cementitious sub-base (CT Subbase)
is 250 mm,
 Thickness of Cementitious base (CT Base) is 120
mm, Aggregate interlayer is 100mm
mm
 Thickness of Bituminous concrete (BC) is 50 mm are
 Obtained by interpolating the thickness of CBR 5%
and 10%.

Calculation of Resilient Modulus (MR) for
case 2
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 MR subgrade = 17.6 x CBR0.64 = 17.6 x 70.64 = 61.15
Mpa.
 MR Bituminous layer = 3000 Mpa (From table 7.1
Resilienent Modulus of Bituminous Mixes, page 23,
IRC: 37: 2012)
 Pavement composition for 90 per cent Reliability is
BC + DBM = 100 mm,
 Aggregate interlayer = 100 mm (MR = 450 MPa),
 Cemented base = 120 mm (E = 5000 MPa),
 Cemented subbase = 250 mm (E = 600 Mpa)

cemented base and cemented sub-base with
SAMI layer over cemented base.
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Continue ….
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PAGE 33 AND 34 OF IRC: 37: 2012

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RESULT:
 Design traffic of 150 msa and CBR of 7%
 thickness of Cementitious sub-base (CT Subbase) is
250 mm,
 Thickness of Cementitious base (CT Base) is 165
mm,
mm
are
 obtained by interpolating the thickness of CBR 5%
and 10%.

Case 4 Bituminous pavement with base of
fresh aggregate or RAP treated with foamed
bitumen/ Bitumen emulsion and cemented
sub-base
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Continue …
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110
PAGE 36 AND 37 OF IRC: 37: 2012

Determination of thickness for case 4
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 RESULT:
 Thickness of Cementitious sub-base (CT Subbase) is
250 mm,
 Thickness of Treater reclaimed aspalt pavement (Treated
RAP) is 180 mm,
 Thickness of Dense Bitumen macadam (DBM) is 50 mm
 Thickness of Bituminous concrete (BC) is 50 mm are
 Obtained by interpolating the thickness of CBR 5% and
10%.
 Instead of RAP base of fresh aggregates treated with
bitumen emulsion/ foamed bitumen can be used to obtain
stronger base.

cemented base and granular sub-base with
100mm WMM layer over cemented base:
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Determination of thickness for case 5
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 RESULT:
 Thickness of Granulated Subbase (GSB) is 250 mm
 Cementitious sub-base (CT Subbase) is 195 mm,
 Thickness of aggregate layer is 100 mm, Thickness
of Dense Bitumen macadam (DBM) is 50 mm
 Obtain by interpolating the thickness of CBR 5% and
10%.
 The upper 100 mm of granular sub-base should be
open graded so that its permeability is about 300
mm/day or higher for quick removal of water entering
from surface.

Calculation of Resilient Modulus (MR) and
Modulus of Elasticity (E):
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 For traffic of 150 msa, Subgrade CBR 7%,
 MR subgrade = 17.6 x CBR0.64 = 17.6 x 70.64 = 61.15
Mpa.
 MR Bituminous layer = 3000 Mpa (From table 7.1
Resilienent Modulus of Bituminous Mixes, page 23,
IRC: 37: 2012)
 MR Aggregate = 450 Mpa and
 E of cemented base is 5000 MPa,
 E Granular subbase = MR subgrade x 0.20 x h0.45
 Where, h = Thickness of GSB = 250 mm
 = 61.15 x 0.20 x 2500.45 = 146.72 Mpa.

Design check
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 To check the suitability of pavement design
discussed above we carry out checks, which ensure
safety against the failure of designed pavement.
 The flexible pavement is checked for two types of
failures i.e. Rutting in pavement and Fatigue in
bottom layer of bituminous surfacing.
 The following condition should be satisfied for the
design to be satisfactory
 Design strain < Allowable strain
 Allowable strain = Obtained by fatigue model and
rutting model
 Design strain = IITpave software

Design of Drainage layer
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 Design a granular drainage layer for a four lane
heavy duty divided highway for an annual
precipitation of 1200 mm. Longitudinal slope = 3 per
cent, Camber = 2.5 percent.
 Crack Infiltration Method

Continue ...
 Depth of drainage layer = 450 mm (WMM 250mm
and Sub-base 200mm) By design.
 Width of drainage layer : Calculate
 AB = 8.5+1+2x0.45 = 10.4 m (1m unpave shoulder)
 AC = 10.4 x(3/2) = 12.48 m.
 AD = 16.24 m
 (hypotenious of AB and AC)
 Elevation drop :
 Along AC: 12.48x3% = 0.374m
 Along CD: 10.40x2.5% = 0.26m
 Total drop = 0.634
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Continue ….
 Hydraulic gradient = [Elevation drop/ length AD]
 = [0.634/16.24] =0.039
 Infiltration rate calculation:
 qi = Ic [Nc/Wp + Wc / (Wp.Cs)]
 Ic = 0.223 cub. m/day/meter
 Nc = 3
 Wp = 10.4 m
 Wc = Wp,
 Cs = 12 m
 q = 0.083 Cub.meter/day/meter
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Continue.
 Amount of water infiltrated (Q);
 Q = 0.083 x 1 x 16.24 = 1.35 Cub.meter/ day.
 Compare with
 Q = KIA
 A = Area of cress section = 1 x 0.1 = 0.1 sq.m
 K = Coeff of permeability (Unknown)
 I = Hydraulic gradient (0.039)
 1.35 = K x 0.039 x 0.1
 K = 346.62 m/day
 This value of K is useful for deciding gradation.
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(Decide grade by using table)
% Passing
Sieve
Opening,
Mm
Grading 1 Grading 2 Grading 3 Grading 4 Grading 5 Grading 6
20 100 100 100 100 100 100
12.5 85 84 83 81.5 79.5 75
9.5 77.5 76 74 72.5 69.5 63
4.76 58.3 56 52.5 49 43.5 32
2.36 42.5 39 34 29.5 22 5.8
2.00 39 35 30 25 17 0
0.84 26.5 22 15.5 9.8 0 0
0.42 18.2 13.3 6.3 0 0 0
0.25 13.0 7.5 0 0 0 0
0.10 6 0 0 0 0 0
0.075 0 0 0 0 0 0
Coeff. Of
permeability
m/day
3 35 100 350 850 950
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Provide Grading 4 for K 346.62 m/day = 350m/day

Recommendation
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 Specifications should be modified according to local
condition. In wet climate wearing course should be
impermeable.
 long duration and low intensity rainfall causes more
damage as compare with rainfall of small duration
and more density.
 If DBM and SDBC/BC are designed properly (4% air
voids and protected shoulder) impermeably can be
ensure.
 Adequate provision for sub-surface drainage prevent
pavement damage.

Recommendations.
 Thickness charts with BC/ SDBC are valid for all
rainfall area.
 For pavement carrying heavy traffic wearing course
laid over WBM shows better performance.
 For low traffic (upto 5 msa) bitumen surfacing with
two coats is found to be suitable.
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Conclusion
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 Time to time revisions of code provision are needed
keeping in view changes in traffic pattern and
development of new technologies. Further with the
gain of experience in the design as well as
construction procedure of flexible pavement have
demanded certain changes.
 Hence by considering the above factors IRC: 37:
2012 includes some conceptual changes in the
design of flexible pavement such as inclusion of
Resilience moduli and consideration of strain in
design.

Conclusion .
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 This code also encourages the use IIT pave software
which is newly recommended.
 Since the use of semi-mechanistic approach, the
design is not only based on the experience but it
also gives parameters (strain parameter) to check
the obtained design.
 Solution to the above pavement design problem
shows that the thickness design varies with the
variation in various factors.

References
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 [1] IRC: 37: 2012, “Guidelines for Design of Flexible
pavement”, second revision.
 [2] IRC: 37: 2001, “Tentative guidelines for Design of
Flexible pavement”

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