CE407– Transportation Engg

Dr. Rahul T.M

Assistant Professor
Department of Civil Engineering
Indian Institute of Technology Ropar

Contact Number: 9945670883

Email id: tm.rahul@iitrpr.ac.in
 Syllabus

Lecture description
Classification, economical relevance of transportation, Transportation system concept and its components

Cross sectional elements, sight distance and its application, super elevation,
Horizontal alignment and vertical alignment.
Pavement layers, Pavement materials
Tests on pavement materials –soil, aggregate, asphalt.
Mix design of asphaltic pavements
Structural design of asphaltic pavements
Types of bituminous construction, Pavement maintenance and rehabilitation.
Introduction to traffic engineering; Traffic control devices – signs, markings, signals, islands; types of
intersection for Compaction

Traffic flow characteristics-speed, flow, density

Traffic studies and data collection.
 COURSE PLAN

• Quizzes (February 16 -2022 and April 13 -2022):15%

• Mid-Semester Written Exam:25%

• End-Semester Written Exam:40%

• Lab Viva (towards end of semester, date would be announced) + calculations (which needs to be submitted
every week) – 20 %
• The video of an experiment will be shared which you need to see and learn.
• Values for lab experiment will be given as question, which you need to submit as calculation within stipulated
time.
Suggested texts and reference materials (If any)
Text Books
1. P. Chakroborty and A. Das, Principles of Transportation Engineering, Prentice Hall India
2003 (2nd edition).
2. S.C. Saxena and S.P. Arora, A text book of Railway Engineering, Dhanpat Rai, 2001.
3. S. K. Khanna, M. G. Arora, and S. S. Jain. Airport planning and design. Nem Chand
Brothers, 1999 (6th edition)
4. S.K. Khanna, C.E.G. Justo and A. Veeraragavan, Highway Engineering, Nem Chan
Bros., 2002(10th edition).
5. Relevant codes from Indian Roads Congress (IRC), Bureau of Indian standards (BIS
and Asphalt Institute Manuals (AI).
Reference Books
1. C.J. Khisty and B.K. Lall, Transportation Engineering: an introduction, Prentice Hall India
2003 (3rd edition)
C.S. Papacostas and P.D. Prevedouros, Transportation Engineering and Planning, Prentic
Hall India, 2001 (3rd edition).
 Time table

• Interaction session (Wednesday 3-3.50 PM)

CE407– Transportation Engg

Dr. Rahul T.M

Assistant Professor
Department of Civil Engineering
Indian Institute of Technology Ropar

Contact Number: 9945670883

Email id: tm.rahul@iitrpr.ac.in
Introduction to Transportation
Engineering
 Role of Transportation
Transport and economic growth
Transport and utility of goods
Producer and consumer
Preservation of quality of goods
Utilization of natural resources
Transport and urbanization
Transport and industrial development

Introduction to Transportation Engineering 3

 Role of Transportation…
• Transport and agricultural development
• Costs of goods
• Administration
• Defence and strategic needs
• Tourism
• Transport facilities and social activities

Introduction to Transportation Engineering 4

 Modes of Transport
• Railways
• Surface
• Underground
• Elevated
• Road Transport
• Air Transport
• Water Transport
• Pipelines

Introduction to Transportation Engineering 5

Transport Modes Characteristics

• Speed
• Safety
• Adequacy
• Frequency
• Regularity
• Integration
• Cost
• Cheapness
• Fuel efficiency

Introduction to Transportation Engineering 7

 Transport modes in India
• Railways : (Facts and figures 2016-17, Indian
railways)
• Total length - 67368 km
• Total revenue generated -626.3 Crore
• 811.6 crore people used it
• Road Transport (ROADS - Statistical Year Book India
2017)
• National Highways: 97991 Km
• Total Surfaced road:3157806 Km

Introduction to Transportation Engineering 8

 Transport modes in India…
• Air India and Indian airlines, other private airlines
• 7.1 million passengers (2004-2005)
• Domestic air traffic increasing 10% per annum

• Indian coast-line: 7516 km, 12 major ports

Introduction to Transportation Engineering 9

 Advantages and Disadvantages of
Road Transport
• Wide geographical coverage provided by roads
• Low capital investments
• Quick and assured deliveries
• Flexibility
• Door-to-door service
• Personalized service
• Personalized travel

Introduction to Transportation Engineering 11

 Advantages and Disadvantages of
Road Transport….
• Short hauls
• Safety
• Environmental pollution
• Parking problem
• Energy

Introduction to Transportation Engineering 13

Role of Roads in Indian Economy

• Connection to villages
• Communications in hilly terrain
• Strategic importance
• Carriers of fright and passengers as a feeder to other
modes
• Helps agriculture, dairy, forest, fisheries, tourism, etc.
development
• Employment
• Famine and flood relief
• Administrative convenience

Introduction to Transportation Engineering 14

CE407– Transportation Engg

Dr. Rahul T.M

Assistant Professor
Department of Civil Engineering
Indian Institute of Technology Ropar

Contact Number: 9945670883

Email id: tm.rahul@iitrpr.ac.in
 Objective of todays class
 Understand various classification of Transportation
Engineering

 Understand the concept of transportation system

 Definition
 Components

Introduction to Transportation Engineering 2

Source: Chakraborty and Das
 General classification of transportation
problems

• Functional classification
• Elemental classification
• Modal classification
 Functional classification
• General classification based on the functional area that is focussed
• Traffic engineering
• Analysis, design and operation of transportation facilities used by the
vehicles.
• This field commonly focus on vehicles travelling on roads
• Includes planning, geometric design and traffic operation along roads
• Pavement engineering
• Deals with structural analysis and design, construction and maintenance of
roads, airport pavements etc.
• Need to understand the materials used in construction also.
• Transportation planning
• Planning for transportation infrastructure
• Includes Urban transportation planning, intercity planning, planning
connectivity of rural areas etc.
• Should be planned keeping in mind sustainability
• Consider various solutions for the planning problem at hand.
• The best solution is selected
• Transportation economics
• Analyze the costs and benefits of transportation infrastructure
• Deals with various techniques that are used in their analysis
• Understands how to finance and recover costs of projects
• Public transportation
• Deals with analysis, design and operations of public transportation systems
• Public transport is important from a sustainability perspective.
• They move on a fixed route and move people from one point to another.
• Public transport includes bus, metro, regional rail (Mumbai and Chennai) etc.
 Elemental classification

• Driver
• Vehicle
• Way
• Road, rail etc.
• Control
• Traffic signals, signage etc.
• Terminal
• Bus station
• User
 Modal classification
• Roadway
• Bus, car, two-wheelers, auto rickshaw, bicycle, pedestrian etc.
• Railway
• Metro, mono-rail, regional rail etc
• Airways
• Waterways
 Definition

• System: A group of related parts – components - that move or work together

• Eg: Computer system

• Transportation System: A system for moving persons or goods

• Urban Transportation System Planning
• Public Transportation System planning
 Characteristics of an efficient transportation
system

• The system should be well designed

• Should be constructed and operated at a reasonable cost.
• Should have high degree of safety and reliability.
• Avoid unnecessary traffic flow
• Well maintained and managed
Characteristics of an inefficient transportation
system
• Transport congestion
• High transportation cost
• Increase in travelling time
• More traffic accidents
• Loss of life and property
• Air pollution
• Decrease in productivity
• Urban sprawl.
Causes of inefficiency
• Increased demand
• Lack of road space
• Inadequate transport facilities
• Lack of a long term traffic improvement program
• Mismanagement of transport facilities
• Lack of urban planning
System approach towards transportation
planning
 Definition

• Goals
• General definition of a desired result
• Improve the mobility of people
• Objectives
• Specific aims to be achieved or specific strategies to be adopted to achieve
goal
• Eg. reduction in average travel time of people in a city, reduction in transport
expenditure
 Government or political set-up

Definition of transportation goals and objectives

Forecasted condition Identification of needs Existing condition

Determination of alternatives

Financial feasibility analysis Technical implication analysis

Economic impact analysis Land-use and demographic

impact determination

Environmental impact analysis

Evaluation of alternatives

Are there
Development of
any good
implementation plan
alternatives
 Transportation planning process

• Case study - Building an over bridge at Kharar junction

 Government or political set-up

Definition of transportation goals and objectives

Forecasted condition Identification of needs Existing condition

Determination of alternatives

Financial feasibility analysis Technical implication analysis

Economic impact analysis Land-use and demographic

impact determination

Environmental impact analysis

Evaluation of alternatives

Are there
Development of
any good
implementation plan
alternatives
 Objective of today’s class

• Understand the road planning process

 Need for highway planning

• To plan road network for efficient and safe traffic operation

• Efficient with respect to cost if construction, operation and different impacts like on
economy, environment etc.
• To arrive at the road system and the length of categories.
• Road type to be adopted, number of lanes, facilities
• To determine date wise priorities
• By when land acquisition can be completed, when road construction needs to start,
which segments of road should be given preference first, when construction should
end
• To plan for future requirements
• Considering future facilities required at highway and future additional connectivity that
might be required.
• To work out financing system
 Road planning

• The planning of road projects has four stages:

• Feasibility study

• preliminary engineering planning

• final engineering planning

• Construction planning
 Highway feasibility planning

• Two major parts

• Assessment of road length requirement for an area – for a state, district etc.
• This is determined by the utility offered by various types of road and their
approximate location in the proposed area.

• Preparation of master plan – phasing of plan

• Final road development plan- where road and accessory facilities are
required in an area.
• Mater plan will encompass the current and future requirement

• Requires planning surveys to understand the current scenario and the future
scenario.
 Types of planning surveys (fact finding surveys)

• Economic studies

• Financial studies

• Traffic or road user studies

• Engineering studies
 Economic Studies
• Current economic activities and their projection

• Details collected
• Population and its distribution along the proposed areas
• Trend of population growth
• Agricultural and industrial products along the proposed areas.
• Trends of industrial and agricultural development
• Existing facilities with regard to communication, recreation, education etc.
• Per capita income
 Financial studies
• Sources of income, and estimated revenue from taxation on road
transport

• Toll taxes, vehicle registration and fines

• Standard of living of people in the study area.

• Future trends in financial aspects

 Traffic or road user studies
• Volume studies, AADT, peak and design hourly traffic volume.
• Origin and destination studies
• Traffic flow patterns
• Mass transportation facilities
• Accidents –cause and cost analysis
• Future trend and growth of traffic
 Engineering studies
• Topographic survey
• Soil survey
• Location and classification of existing roads
• Road life studies
 Fact finding surveys –as plans
• General area plan
• Topography, existing road network, drainage structures, towns and
villages with population, type of activities
• Distribution of population groups
• Locations with productivity
• Road network with desire lines
 Interpretation of planning surveys
• To arrive at the road network
• Traffic flow patterns (current and future)
• To prioritize the phase of road development plan.
• Priority for congested areas
• Priority for high productivity areas
• To arrive at accessory facilities for highway
 Objective of today’s class

• Understand the road planning process

• Factors controlling alignment of roads

• The cost and benefits of constructing a road

 Outcomes of feasibility studies

• Goals
• alternatives
• approximate actions
• preliminary impact assessments
• cost forecasts
Outcomes of preliminary engineering planning

• Approximate location of the road

• Basic traffic and road engineering solutions
• Landscaping of the road side and the handling of green areas
• How to prevent negative impacts on the environment
• Target timetable and stages of construction
• Cost estimate
 Outcomes of final engineering planning

• Precise road alignment – the GIS co-ordinates through which the road
should pass

• Detailed design solutions – the thickness of pavement, materials to be

used, the properties of materials to be used etc.

• Cost estimate and possible division of costs

• Cost for land acquisition
• Cost of construction
• Cost for carrying out administrative proceedings
 Outcomes of construction plan

• Sanctioning various documents required in construction

• Planning various stages of construction
 Factors controlling alignment of roads

• Obligatory points
• Points through which the road had to pass – an intermediate town, location
for construction of bridge etc.
• Ponts through which road should not pass – religious places, costly land etc.
• Road alignment should cater to areas with high traffic.
• Geometric design
• Should avoid areas with high gradient
• Economics
• Need to consider the life cycle cost of pavements
 Economic evaluation of highway projects
• Compares cost and benefit of highway project – feasibility analysis

• Cost and benefit is spread over a time frame – life of the project

• Costs and benefits are brought to a base year and their Net Present
Value (NPV) is calculated.
 Costs
• Agency cost
• Planning
• Land acquisition
• Highway construction
• Accessory infrastructure
• Administration
• User Cost
• Vehicle Operating Cost (VOC)
• Variable costs – distance and time related
• Fixed costs – capital cost, vehicle insurance
• Accident cost
• Cost of travel time
 Benefits

• Road user benefits

• Savings in VOC
• Reduction in travel times
• Reduction in accidents
• Savings in maintenance costs

• Social benefits
 Objective of today’s class

• Understand the elements of geometric design

• Determine the stopping sight distance (SSD)

• Level surface
• Slope
 Geometric design

• Design of road layout

• Requirement
• Safety
• Smooth traffic flow

• Need to be planned - alignment stage

• Should consider future growth and upgradation
• Difficult improve it in later stages
 Elements of Geometric design

• Provision for sight distances

• Design of Horizontal alignment considerations

• Providing cross-sectional elements

• Design of vertical alignment considerations

• Intersection design
 Sight Distance

• Sight Distance
• Visibility of stationary or moving objects by driver at a
specified height above the carriageway
• Measured in distance

• Types
• Stopping or absolute minimum sight distance
• Safe overtaking or passing sight distance
 Stopping sight distance
• Distance ahead that a motorist should be able to see
so that the vehicle can be brought safely to a stop
short of an obstruction or foreign object in the road.

• Requirement of stopping sight distance knowledge to

• To design vertical curves
• To manage restrictions at horizontal curves
• To mange uncontrolled intersection
 STOPPING DISTANCE

Lag Distance Braking Distance

Distance Travelled during total Distance Travelled after

Reaction Time application of brakes

6
• Total reaction time (t) –perception time and brake
reaction time in seconds
• Speed of travel in meter per second (V )
• Frictional resistance between the road and the tyres
(F)
• Gradient if the road (n%)
• W = weight of the vehicle
• Efficiency of brakes
Stopping distance at level

• Distance Traveled during Perception and Brake

reaction time
d = V. t

• Distance traveled during braking

d1 = V2 / 2g f
Stopping distance at slopes

d1 = V2 / (2g (f +n/100)) (upward slopes)

d2 = V2 / (2g (f - n/100)) (downward slopes)

• Always take care of the units

• When the road is single lane and vehicle is

moving in two directions.
• twice calculated stopping distance

• When SSD is not available at any place –

restrict speed.
 Objective of today’s class

• Understand the concept of Overtaking Sight

Distance (OSD)

• Elicit the various components of OSD

• Derive the OSD

 Overtaking sight distance
• The minimum distance required by a driver,
overtaking a slow vehicle, to see the traffic in
opposite direction is called “minimum OSD” or
“safe passing distance”.
• Need to maintain minimum OSD for safety
 Overtaking sight distance
2 3 4 5
s b s

1 d1 d2 d3
2 5 6

3
• OSD = d1 + d2 + d3

– d1 = Distance travelled by overtaking vehicle

during the reaction time ‘t’ seconds of driver from
1 to 2 (m)

– d2 = Distance travelled by overtaking vehicle from

2 to 5 in ‘T’ seconds (m)

– d3 = Distance travelled by vehicle coming in

opposite direction from 6 to 5 in ‘T’ seconds (m)
 Factors affecting overtaking sight
distance
• Speeds of overtaken vehicle (Vb -m/s)and vehicle
coming from opposite direction (v – m/s).
• Distance between overtaking and overtaken
vehicles (minimum spacing required (s - metre)
• Reaction time of driver of overtaking vehicle (t -
seconds)
• Rate of acceleration of overtaking vehicle (a –
m/s2)
• T = time taken for the overtaking operation
• d1 = vb. t

• d2 = vb. T + 2.s

• T = (4.s/a) 0.5

• d3 = v.T
 Objective of today’s class

• Understand the concept of Horizontal curves

• Forces acting on horizontal curves

• Overturning
• skidding

• How to design horizontal curves safely

• Radius
• Super elevation
 Horizontal curves
• A horizontal curve provides change in direction to the central line of
the road

• Necessary for gradual change in direction when a direct point of

intersection is not feasible

• Ex. Highways, Interstates, high speed

roads with constant flow of traffic
 Types of Curves

• Simple Curve
• Compound Curve
• Reverse Curve
• Spiral Curve
• Design of roadway curves should be based on an
appropriate relationship between design speed and
curvature and on their joint relationships with super
elevation and side friction
• Centrifugal force – throws vehicle outwards
• Depends on speed of vehicles
• Overturning effect (counteracted by mass of vehicle)
• Transverse skidding
(counteracted by
transverse frictional
resistance)
Centrifugal force

• P = (W. V2)/(g.R)
P = centrifugal force in Newton
W = Weight in Newton
R = Radius of circular curve in ‘m’
V = speed in m/sec
g = acceleration due to gravity (9.8 m/s2)
 Overturning effect
• There is a chance of overturning along curve when
P/W = v2/(gR) > (b/2h)

‘P/W ‘ is called the centrifugal ratio or impact factor

h = height of centre of gravity of vehicle from
ground (m)
b/2 = horizontal distance between centre of
gravity and centre of tyre (m)
 Transverse skidding effect

• There is a chance of lateral skidding along curve

when P/W > f
f = coefficient of friction between pavement and tyre

• Indian Roads Congress (IRC) codes suggests a ‘f’

value of ‘0.15’
Super elevation

• To prevent overturning and skidding outer edges are

raised inside a horizontal curve.

• This transverse inclination is called super elevation or

cant (e).

• e = tan θ (approximately sin θ )

= super elevated height of outer edge/ width
of pavement
Linking super elevation (e) with radius and
velocity

• Centrifugal force = P = (W.v2)/(gR) (acting horizontally

outwards)

• Weight of the vehicle (W) (acting vertically downwards)

• The frictional force on tyres (F) (acting towards centre of

curve)
• e + f = v2/(gR)
.
• Some times super elevation cannot be provided.
• Need to reduce speed
• Increase radius
Steps in super elevation design along non-urban
highways

• Take care of fast moving vehicles

• Maximum super elevation

• Take care of slow moving vehicles

• Depend more on lateral friction

• Usually super elevation is provided for 75% of design

speed.
• Step 1
• Neglect friction and provide super elevation
• e = (0.75 * V) 2/(g*R)
• Step 2
• Check whether e< 7%
• if yes, provide value obtained and stop
• If no, provide maximum of 7%
• Step 3
• Find ‘f’ – coefficient of friction – for 7%
• Use design speed
• If ‘f’ <0.15, stop
• If no, calculate the allowable speed with e + f = 0.07 + 0.15
• If allowable speed is more than design speed, adopt latter
• Else, restrict speed to allowable speed or increase radius
 Objective of today’s class

• Knowledge of Extra widening

• Various constituents extra widening

• Derive the formula for extra widening

 Extra widening
• Horizontal curves not having large radius
• Increase the width of pavements.
• Reasons for this widening
• Off-tracking at low speed Mechanical widening
• Off-tracking at high speed

• Drivers - use outer side as the beginning of a curve

Psychological • Psychological tendency of drivers
widening • More clearance while overtaking at curves
 Two components of extra widening

• Mechanical widening (W m)
• Length of vehicle (l) (metres)
• Radius of curve to centre line (R) (metres)
• Number of lanes (n)

• Psychological widening (Wp)

• Design speed of vehicle (v) (metre/second)
• Radius of curve (R) (metres)
• Mechanical widening (Wm)
• l2/(2R)
• nl2/(2R) (n = number of lanes)

• Psychological widening (Wps)

• v/(2.63 *(R)1/2)
 Objective of today’s class

• Summit curve and deviation angle

• Estimating Length of summit curve

 Summit curve (vertical alignment)

• Curves with convexity upwards

• They are formed when two gradients meet

• Mostly these curves are formed in form of a parabola
– Easy for computing co-ordinates
– Good riding comfort

• Sight distance is limited by the curve itself

– The curve is the obstruction

• Main aim - is to find its length of curve (L in meter)

• Length of summit curve depends on
– Deviation angle between interacting gradients =
algebraic difference between them (N).
– Sight distance
• Stopping Sight Distance (S in metre) or Overtaking
Sight distance (OSD in metre)
• Proper sight distance should be there
– Height of eye level of driver (h1 in metre)
– Height of object above road surface (h2 in metre)
 Design with respect to Stopping Sight
distance
• Two cases
– length of summit curve when L>S
L=

• length of summit curve when L<S

• The same formula can be used for overtaking

sight distance also.
• Offsetting in field – Chakraborty and Das, IRC SP 23
 Objective of today’s class

• Types of urban roads

• Understand various cross sectional elements of a

highway
Classification of Urban roads (IRC -86)

• Arterials
• Arterial are highways with full or partial access
• Parking, loading and unloading activities are restricted
• Serves through traffic
• Used in intra-urban travel as well as travel between sub-
urban centres

• Sub-arterials
• Similar to arterial but with lower level of mobility
• Collector streets
• They collect traffic from local streets and feed on to
arterials and sub-arterials, and vice versa
• Local streets
• Provide access on to property
• Does not have heavy traffic
• Trips originate or end along these streets
• These adjoining area of these streets would be having a
land-use depending on whether the area is residential,
industrial etc.
Highway cross-section elements

• Pavement surface characteristics

• Cross-slope or camber (Drainage)

• Width of pavement or carriageway

• Road margins

• Kerbs
Pavement surface characteristics

• Friction

• Pavement unevenness

• Light reflecting characteristics

Friction

• Requirement
• Required for determining operating speed
• Prevent lateral movement
• Set minimum distance for stopping vehicles

• Slide

• Slip
• Factors affecting skid resistance
• Type of pavement surface
• Condition of pavement
• Wet or dry, oil spilled
• Condition of tyre
• New or worn out
• Speed of vehicle
• Brake efficiency
• Tyre pressure
• Coefficient of friction along longitudinal direction (IRC-73)
• 0.4 (20 Km/hr) and 0.35 (100 km/hr)
• Coefficient of friction along lateral direction – 0.15 (IRC-73)
Pavement unevenness

• Reasons
• Lack of subgrade compaction
• Unscientific construction practices
• Use of low-quality pavement materials
• Non-functional construction machinery
• Lack of drainage provision
• Combination
• Measured using road roughness or unevenness indicator
• Effects
• Lack of speed
• More Accidents
• High vehicle operating and maintenance costs
• Absence of comfort
 Light reflecting characteristics

• Important from perspective of night visibility

• Wet pavement – high reflection

• Black top pavements – poor visibility at night but absence of

reflection in bright sunlight
 Camber
• Transverse slope provided on the road surface (‘1’ in ‘n’)
• To drain off water
• Need to drain off water
• Prevent percolation to subgrade
• Prevent entry of water to bituminous layer
• To reduce skid
• Factors affecting rate of camber
• Type of road surface
• Amount of rainfall
Recommended camber values (IRC –73)

Heavy rain Light rain

Surface type

Concrete/Bituminous 2% 1.7 %

Gravel/WBM 3% 2.5 %

Earthen 4% 3.0 %
Shapes of camber
• Parabolic camber
• Flat at middle - Provided for fast moving vehicles
• Y = (2x2)/(nW)

• Straight line camber

• Provided in case of flat surface

• Combination camber
• Provided when flat edges and flat middle section is
required
 Objective of today’s class

• Understand the cross sectional elements of a highway

Width of carriage way
• Depends on number of lanes and width of a traffic lane
• Usually for a single lane road a width of 3.75m is considered desirable
• For a two or more lane 3.5 m width per lane is considered suitable
• Components for identifying width of lanes
• Width of vehicle – maximum width as per IRC is 2.44m
• Side clearance
• Clearance between lanes (for more than 1 lane)
Medians
• Seperate traffic in two direction
• Uses
• Prevent head on collision
• Channelize traffic
• Protect turning and crossing traffic
• Safety of slow moving vehicles
• Specification
• Minimum 5 m width on highways (3m when land is restricted)
• 1.2 to 1.5 m width on bridges
Kerbs

• Boundary between pavement and shoulder

• Usually provided on urban roads

• Type of kerbs
• Low kerbs (10cm height above pavement)
• Semi-barrier type kerbs (15 cm Height)
• Barrier type kerbs (20 cm height)
Kerb diagram
Road margin
• Elements
• Shoulders
• Emergency lane for vehicles forced to take out of highway
• Lane for vehicles under repair
• Minimum shoulder width recommended by IRC is 2.5m
• Rougher than regular lane –to prevent usage as regular traffic lane
• Color should be different
• Parking lanes – urban area –parallel parking, angle parking

• Bus bays to stop public transport buses

• Drive ways or service roads

• Cycle tracks – urban areas

• Footpaths –urban areas

Parallel parking
Diagram of a highway cross section
Diagram of a typical highway cross section in urban
areas
 Objective of today’s class

• Understand different Pavement materials

• Pavement structure

• Source and characterization of pavement materials

 Pavement materials

• Soil
• Ground base on which construction of road is done
• This ground support is compacted and is called
subgrade

• Aggregate
– processed Rocks of certain size ranges
– Component of bituminous layer
– Take wheel loads by interlocking
 Pavement materials

• Bitumen
– “Bind” the aggregate particles together.
– Usually obtained through fractional distillation
of crude oil
– Natural bitumen is called asphalt
– The term “bitumen” and “asphalt” are used
interchangeably
 Pavement structure

Surface layer or Wearing course

base

subbase

subgrade

Figure: Different layers in a flexible pavement

 Pavement material definition
• Source

• Characterization

• Tests
Soil
• Source
– Weathering of rocks
• Characterization
– Resilient modulus
– Poisson’s ratio
– Permeability
• Tests
– CBR test
– Plate load test
– Shear test
– Triaxial test
Stone aggregate
• Source
– Quarries
– Classification: Igneous, metamorphic and
sedimentary rocks
– Broken –
• Initially: earth moving equipments, explosion
• Then using crushers –gyratory, impact
– Sieved and batched
– Scalping
 Characterization
• Resilient modulus (MR)

• In pavement -granular material is used in subbase

• One cannot use directly determined Resilient

modulus for subbase during pavement design
Bitumen
 Source
• Fractional distillation of petroleum
• Tar- different from bitumen
– Destructive distillation of coke
• Types of bitumen
– Viscosity grade (VG) - earlier called penetration
grade
– Emulsions
– Cutback bitumen (naphtha, kerosene, light oil)
• The type of bitumen used depends on
– Weather, economy , construction time etc
 Characterization
• Viscosity
– Resistance against flow
• Rheology
– Stress, strain and time relation
• Bitumen behavior
– High temperature – viscous liquid
– Low temperature – brittle material
 Objective of today’s class

• Desirable bitumen and aggregate properties

• Tests to check it
 Desirable properties of road aggregates

• Strength
• Hardness
• Toughness
• Shape of aggregate
• Packing of aggregate (Angularity)
 Tests on aggregates

• Crushing strength test

• Los Angeles abrasion test
• Aggregate Impact test
• Elongation index and flakiness index tests
 Asphaltic rock
Bitumen
 Requirements of bitumen

• Able to mix – viscosity

• Survive adverse weather –temperature susceptibility
• Flexible – stretchable - ductility
• Adhesion to aggregates
 Desirable properties

• Adequate viscosity

• Adequate temperature susceptibility

• Adequate stretchability
 Tests on bitumen

• Ductility of bitumen
• Penetration of bitumen
• Softening point of bitumen
• Flash and fire point of bitumen
• Specific Gravity of Bitumen
 Objective of today’s class

• Concept of bituminous mix design

• Various elements in mix design

 Pavement structure

Surface layer or Wearing course

base

subbase

subgrade

Figure: Different layers in a flexible pavement

 Classification of layer

• Bound layer –
– Bitumen or cement or water bounded
• Mostly used in base and wearing course
• Water Bound Macadam (WBM) (IRC 19 -2005)

• Unbound layer (mostly used in sub-base)

– Granular sub base
 Some bitumen bounded layers

• Dense graded bituminous mixes

– Dense Bituminous Macadam (IRC 94: 1986)
– Bituminous concrete (IRC 29 -1988)
• Good quality bitumen mix
• Prepared using dense graded aggregates
• Bitumen binder is of good quality
• Aggregate and bitumen - mixed in controlled conditions
• What is bituminous mix design
– Determination -optimum bitumen -aggregate bitumen mix

• Why can’t we take a constant value of bitumen

– Differ based on gradation of aggregate, type of bitumen,
aggregate batching

• What are the issues if we are not properly doing mix design
– Fatigue cracking - repetitive application of loads
– It starts from bottom and propagate to top
– In the formula for structural, values of constants depends on
bitumen content, air voids, gradation of aggregates etc.
• Other issues because of improper mix design
– Bleeding: appearance of bituminous binder on the surface
– Corrugations
• Ripples formed laterally across pavement
• These occur as a result of lack of stability of mix
– Locations where vehicles brake often.
– Rutting
• Longitudinal depression along wheel path
• with or without transverse displacement
• Rut depth of 0.5 in. is considered a rutting failure.
• Caused by excessive or less air voids in the in-place mix
 General steps in mix design
1)Selection of bituminous mix
- For example, bituminous concrete
2)Select the standard specification - IRC and IS codes.
– Specific tests
– details of the tests
– Acceptable/not acceptable levels of results that are to be used.
3) Select aggregates, blends of aggregates, and bitumen binder
4) Test selected blend with different asphalt contents
5)Determine the Volumetric properties, stability and flow
6) The optimum bitumen content is selected based on
– Volumetric properties, stability and flow.
7)Estimate relevant structural design parameters
 Important elements in mix design

• Voids in Mineral Aggregates (VMA)

• VFB – Voids Filled with bitumen
• VA (Air Voids)
• Stability
• Flow
 𝑉𝑎
• 𝑉𝐴 = ( ) X 100
𝑉𝑚𝑏

𝑉𝑎 +𝑉𝑏𝑒
• 𝑉𝑀𝐴 = ( ) X 100
𝑉𝑚𝑏

𝑉𝑀𝐴 − 𝑉𝐴
• 𝑉𝐹𝐵 = ( ) X 100
𝑉𝑀𝐴
 Objective of today’s class

• Sample preparation for mix design

• Determination of various mix design elements

• Estimation of optimum bitumen content

Sample preparation for element determination (Marshall
Specimen)

• Take a 1200 g of graded aggregates

• Prepare bituminous mix
• For various proportion of bitumen.
• Initial bitumen quantity
• 5-6% of weight of bituminous mix
• Each mix we have to make a compacted specimen.
• Put the mix in a Marshall mould
• Compact it using a hammer
• Typically 35, 50 or 75 blows depending upon anticipated traffic loading
(MORTH -1975, pg 178)
• Specimen should be ideally having a diameter of 4 inch and height of 2.5 inch
Parameters for finding elements in mix design

• Gsb = bulk specific gravity of aggregate

• Gsb1 (for an aggregate type – coarse aggregate, fine aggregate,
fines)
• A/(B-C)
• A= Aggregate weight in air oven dry condition
• B= Aggregate weight in air at saturated surface dry condition
• C= Weight of aggregate in submerged condition

• Average aggregate specific gravity for various gradation.

Gsb = W/ (W1/Gsb1+ W2/Gsb2 + W3/Gsb3+…)
W = Total aggregate percentage
W1 , W2 …= percentage of each sample in total aggregate
percentage
• Gmm =Theoretical maximum specific gravity of the mix
=Mt / Vma
• Total mas of the mix = Mt
• (Total Volume of mix – Volume of the air voids in it) = Vma
• A vacuum test is used to measure it
• Gmb =bulk specific gravity of the mix
• Mt / Vmb
• Vmb = Total Volume of mix
• A/(B-C)
• A= Mix sample weight in air
• B= Mix sample weight in air at saturated surface dry condition
• C= Weight of Mix sample in submerged condition
 Determination of elements

𝐺𝑚𝑏
• 𝑉𝐴 = (1 − ) X 100
𝐺𝑚𝑚

𝐺𝑚𝑏
• 𝑉𝑀𝐴 = (1 − 𝑃𝑠 ) X 100 Ps = 1-Pb
𝐺𝑠𝑏 Pb = bitumen content in the total mix

𝑉𝑀𝐴 − 𝑉𝐴
• 𝑉𝐹𝐵 = ( ) X 100
𝑉𝑀𝐴
 Marshall stability-flow test
• Submerge the sample in water for 30 – 40 minutes
• Temperature of 60 degree Celsius.

• Test stability using a Marshall stability-flow equipment

• Breaking head put on both sides of the specimen
• A compressive load is applied along the diameter of the
specimen at a rate of 51 mm per minute
• Observe the load at which the specimen breaks – stability
• Deformation at failure condition has to be observed ( flow)
 Plot different trends
• Stability - Bitumen content
• Flow - Bitumen content
• VA - Bitumen content
• VMA - Bitumen content
• VFB - Bitumen content
 Volumetric criteria for BC (IRC 29- 1988)

Binder content that gives us 4% air void content is the optimum binder
content provided it satisfies all the other requirements that are given