Prajee Uel Final Project

CE3216- Asphalt Concrete for Road Pavements Construction and its Behaviours under Vehicular Loads.CE3216-Final Year Project-BEng Civil Engineering

By Prajee Embogama-0747642

School of Computing Information Technology & Engineering

Supervisor- Dr. Phebe Mann, Module Tutor- Dr. John Walsh

BEng Civil Engineering (Hons)

University of East London

2011-04-29

ABSTRACT

Pavement, the major element of a road or highway is the paved structure which

traffic is allowed to run on. Durability, comfortably, safety and economy are the main

criterions concerned. Pavement may be constructed either with cement concrete or

asphalt concrete. Later is the most popular and common due to economical

considerations. Asphalt concrete pavement behaves structurally flexible under wheel

stresses. Hence in cases it is termed as “Flexible Pavement”.

Pavement has to serve the traffic while standing against the stresses and distresses

exerted by wheel loads, consequently the liable failures and the damages. Climatic

and weather changes also affect the pavement adversely. Wheel loads and

environmental effects not only individually but also simultaneously deliver the

stresses, consequently distresses on and into the pavement while the pavement has

to response vis a vis. The resultants may be occurring failures unless it can stand

strong enough to bear all those. These stress-collectiveness is complicate process

within the pavement-system. Hence it needs serious attentions in every aspects of

designing, constructing and maintaining. This is a fact learnt doing this project.

Density is an important quality of asphalt concrete regarding the quality control

aspect of asphalt concrete. A density test also was carried out with the field samples

collected from the road construction site of Beam Rich project Dagenham.

Concern to above facts this project focused to investigate, identify and study the

related subjective matters covering the under mentioned. And this paper tries to

present and discuss those found to be important as below briefing.

Road and pavement structure; asphalt concrete which is used to build pavement;

bitumen and aggregate; the constituents of asphalt concrete; refinery process by

which bitumen is obtained; bitumen modifications which enhance its properties;

thermal effects adverse to pavement; behaviours of pavement under traffic wheels;

stresses, distresses, consequent failures and damages; recycling pavements and

sustainability are discussed in this paper covering the prominent findings of the

project. Efforts were made much to collect relevant figures and display them which

may illustrate the facts simplifying the details.

Prajee Embogama-0747642 BEng Civil-University of East LondonPage 2

Acknowledgements

I would like to thank the following people for whom I was able to finish my project

successfully. My supervisor Dr. Phebe Mann who has given the main idea, details

and guidance on how to approach the project. I also greatly appreciate the co-

operation from Dr. John Walsh to provide me with the basic information that i nee

for my project.

I’m grateful to the following people and organisations. City of London-Highway

Engineering Department, senior consultant Mr R. Manmadan. And Galliford Try Civil

Engineering company, Site Engineer Mr. A. Madushanath.


List of Figures.

2.1.1 Cross section of typical road way....................................................................14

2.2 Cross section of a pavement..............................................................................14

2.3 Component of pavement....................................................................................14.

2.3.1 Typical pavement structure..............................................................................16

2.3.2 Load distribution and pavement deflection under loads...................................16

2.5.1 Asphalt concrete pavement structure..............................................................18

2.5.2 Asphalt concrete pavement structure loading responds..................................18

2.5.3 Wheel load distribution and pavement deflection............................................18

2.6.1 Basic Component of typical pavement system...............................................19

2.6.2 Common variations of asphalt concrete pavement section............................19

2.7.1 Pavement components load distribution and stress distribution......................21

3.2 Load pressure and deflection result tensile and compressive stresses..............23

3.4.1 Aspects of designs...........................................................................................24

3.5.1 Pavements design parameters........................................................................25

3.5.3 Example for ELEF...........................................................................................26

3.6.1 Pavement structure.........................................................................................27

3.6.2 Pavement recommended thicknesses............................................................27

3.6.2 Vehicle spectrum of loads...............................................................................27

3.6.3 Type of flexible pavements.............................................................................28

3.8.1 Asphalt concrete layers paving to thicknesses...............................................30

4.1.1 Schematic view of asphalt concrete................................................................31

6.1.1 Asphalt concrete grading samples..................................................................41


6.3.1 Close graded mixture................................................................................42

6.4.1 Interlocked aggregates .............................................................................43

6.4.2 Stone mastic asphalts................................................................................43

6.4.3 Stone mastic asphalt lab sample...............................................................43

6.4.4 Stone mastic surface..................................................................................43

6.5.1 Cross section of typical porous pavement including base course.............44

6.5.2 Porous asphalt concrete............................................................................45

6.5.3 Open graded asphalt concrete..................................................................45

6.5.4 OGFC surface............................................................................................46

6.5.5 OGFC lab samples.....................................................................................46

8.1.1 Schematic view of the petroleum distillation process..................................54

8.1.2 Schematic view of the petroleum distillation temperature status................54

8.1.3 Distillation temperature of petroleum products...........................................55

9.2.1 Types of emulsions ....................................................................................57

9.3.1 Schematic views of asphalt emulsion preparation model samples.............58

9.5.1 Emulsion setting.........................................................................................59

9.5.2 Stages in the brake down of emulsions.....................................................62

10.1.1 Aggregate samples..................................................................................66

11.4.1 Finished RAC-G pavements....................................................................69

12.2.1 Energy balance in asphaltic pavements..................................................69

13.1.1 Vertical pressure transfer in asphalt concrete layers...............................71

13.1.2 Load transfer through granular materials.................................................71

13.1.3 Flexible plate deflection............................................................................71


13.1.4 Pavement strains under wheel load causing stress and deflection..........71

13.1.5 Strains and responds by the layers and load distribution.........................71

13.1.6 Stability of the Pavement layers...............................................................72

13.1.7 Schematic vies of asphalt concrete pavement deflection.........................72

13.5.1 Pavement happens to wear by wheel and heavy loads...........................75

14.1.1 Examples distress, water collected, weekend vice versa........................76


CONTENTS Page

ABSTACTAcknowledgement

List of Figures

23

4

Contents pages

Chapter 1 INTRODUCTION 12

Chapter 2 PAVEMENT 14

2.1 Pavement is the major element of Roadway 14

2.2 Fundamentals and Components of Pavement 15

2.3 Pavement Structure 16

2.4 Pavement Types 17

2.5 Asphalt Concrete Pavement Structure 18

2.6 Pavement system Types 19

2.7 Asphalt Concrete Pavement’s Elements 21

Chapter 3 ASPHALT CONCRET PAVEMENT DESIGN 22

3.1 Philosophy of Pavement 22

3.2 Design criteria 23

3.3 Asphalt Concrete characterisation

24

3.4 Principles and Aspects of Pavement Design 24

3.5 Design Parameters 25

3.6 Pavement Structure 27

3.7 Design Life 28

3.8 Stress distribution factors in Asphalt Pavement 29

Chapter 4 ASPHAT CONCRETE 31

4.1 What is Asphalt 31


4.2 Component / Constituents 32

4.3 Properties of asphalt Concrete 33

4.3.1 Desirable Properties for Asphalt Concrete 34

4.4 Density is the Significant Property 34

4.4.1 Desired Density & Lab test 35

4.5 Stability of Asphalt Concrete 38

4.6 Safety 38

4.7 Durability 39

4.8 Characterisation 39

Chapter 5 ASPHALT CONCRETE MIX TYPE 39

5.1 Asphalt Concrete to use in Hot or Cold weather 39

5.1.1 1 Hot mix Asphalt Concrete 40

5.1.2 Worm Mix Asphalt Concrete 40

5.1.3 Cut-back Asphalt Concrete 40

5.1.4 Cold mix Asphalt Concrete 40

Chapter 6 ASPHALT CONCRETE MIX GRADE

41

6.1 Grading for different Functions 41

6.2 Dense Graded Mix 42

6.3 Hot Mix Asphalt Concrete 42

6.4 Stone Mastic Asphalt concrete 43

6.5 Open Graded Mix 44

Chapter 7 BITUMEN 48

7.1 What is Bitumen 48

7.2 Bitumen as ideal binder 49

7.3 Composition of Bitumen 50


7.4 Properties of Bitumen 50

7.4.1 Adhesiveness 50

7.4.2 I permeability 50

7.4.3 Viscosity 50

7.4.4 Consistency

51

7.4.5 Durability 51

7.5 Uses of Bitumen 52

Chapter 8 CRUDE OIL REFINERY

53

8.1 Petroleum Crude Oil Refinery 53

8.2 Refinery Process 55

Chapter 9 ASPHALT EMULSION 56

9.1 What is Emulsion 56

9.2 Asphalt Emulsion Preparation 57

9.3 Emulsion Technology 58

9.4 Composition Asphalt Emulsion 59

9.5 Setting Process 59

9.6 Classification of Asphalt Emulsion 60

9.7 Variables affecting Asphalt Emulsion 60

9.8 Advantage of Asphalt Emulsion 61

Chapter 10 AGGREGATE 62

10.1 Use of Aggregate 62

10.2 Aggregate Properties 63

Chapter 11 BITUMEN BINDER MODIFICATION 64

11.1 Needs of Modification 64


11.2 What is Asphalt Rubber 64

11.3 Use of Asphalt Rubber 65

11.4 Benefit of Asphalt Rubber 66

11.5 Disadvantages 67

Chapter 12 THERMAL EFFECTS 68

12.1 Thermal Distresses 68

12.2 Energy Balance of Asphalt Pavement 69

Chapter 13 BEHAVIOUR OF ASPHALT CONCRETE PAVEMENT 70

13.1 Factors influencing Pavement behaviours 70

13.2 Pavement Distress Mode due to Traffic 73

13.3 Effects of the pavement Materials 73

13.4 Effect by the tire-pavement contacts 73

13.5 Combine stresses by wheels and Thermal 74

Chapter 14 PAVEMENT DISTRESSES AND FAILURES 76

14.1 Identifying the Distresses and Failures 77

14.2 Asphalt Pavement Distresses Summary 78

Chapter 15. ASPHALT CONCRETE PAVEMENT RECYCLING 84

15.1 Demand for recycling 84

15.2 Recycling Process 85

15.3 Recycling methods 85

15.4 Use of Recycled Materials for Asphalt Concrete 86

15.5 Benefit of Recycling 87

Chapter 16 SUSTAINABILUTY 88

16.1 What is sustainability 88


16.2 Need of Sustainable Pavement 88

16.3 Pavement Sustainability 89

16.4 Components of Sustainable Pavement 89

16.5 Basics of Sustainable Recycling Technology 90

Chapter 17 CONCLUSIONS 91

BIBLOGRAPHY 92


Chapter 1. INTRODUCTION

Pavement is the topmost major element of any road or highway system. Highways or

roads are found to be an important key infrastructure which serve immensely to

transportation services mainly the traffic. It is reasonable to say “no roads no go”

because every things nowadays including developments of any nation and day to

day needs of any society are depended on the transportation. It needs good roads in

other words roads with right pavements.

Durable but economical pavements therefore are a must so that traffic can run

comfortably and safe-faster. Yet, it is to observe that road-pavements are subjected

to regular repairs or rehabilitation sometimes constructing new roads. This is very

impressive as the roads or highway net-works are the vastly spread civil engineering

infrastructure in any country.

Majority of the roads and highways are black. It is because of the “asphalt” as

commonly told. That material is technically termed as “asphalt concrete” with which

pavements are built. Alternatively some pavements are done with cement concrete

which is considered comparatively have higher cost at the construction.

In the context of all above facts, it is impressive and interesting to investigate and

study subjective facts and matters about pavements and also to see any

development of those towards further improvements. The aim of this project has

been focus to study and investigate about the pavement system, asphalt concrete

using to construct it, pavement behaviour, stresses distresses and failures. The

findings of those have been presented in this paper mostly summarised.

Traffic loads and environmental effects not only individually and relatively but also

collectively offer various stresses, consequently distresses on and into the pavement

while the pavement has to behaves hence or vis a vis, or simultaneously, These

collective issues result a complicate process due to which pavement happen to

occur failures. Education, know-how and technology about the aspects of designing,

constructing and maintaining pavements are essential for construction and

maintenance of good pavements.


Objectives and research questions

1.0 Majority of the road pavements are built, paved or surfaced with asphalt concrete. What are the advantages in use of asphalt concrete hence?

2.0 Road pavement structure should be of dense materials to withstand vehicular wheel loads and such stresses. What are the components of asphalt concrete and how it is produced?

3.0 To find out the density of asphalt concrete. What is the desired density of asphalt concrete and how it is achieved when pavements are constructed?

4.0 How is the pavement constructed? Road pavements get damages or various failures at places what are those, causes?


Chapter 2. PAVEMENT

2.1 Pavement is the major Element of Roadway

Pavement is the major element of roadway, highway or street. The section on which

traffic are allowed to run on. It is the superior, factual and vital structure as far as

roads, highways or streets are concerned. Following figures illustrate the main

components of roadway including the pavement.

(Fig. 2.1.1-.dot.ca.gov, 2001)

Drain Shoulde P A V E M E N T .

(Fig. 2.1.2)

Compacted Subgrade

(existing or formed ground on which Sub base is laid)

(Fig. 2.1.3)

Above typical cross sections show the main components of roadway.


Asphalt layer ( aggregate + asphalt binder )

Base Course (compacted aggregate + fines)

Sub base Course ( compacted gravel )

2.2 Fundamentals and Pavement Components

Accounted to traffic loads, AC pavements are made up of several layers which are

laid one after the other to withstand the distribution of traffic loads. The individual

layers are to meet with the following requirements:

The purpose of road pavement is to carry the loads by vehicles smoothly and safely

under all weather conditions for a pacified design life. This is done by:

Stabilizing and forming the existing subgrade to providing stable subbase and

base courses above it.

2) Providing adequate drainage, because water can weaken soils and asphalt

materials of the pavement.

Constructing a pavement structure thick and strong enough structurally to

carry all expected traffic loads for the expected period of time.

Surfaced with a wearing course that resists wear, deformation, weather,

moisture and remains skid resistant.

2.3 Pavement Structure


A road pavement is a layers of structure constructed with specified materials to

facilitate the movements of vehicles with loads. It is to withstand the stresses

applied by vehicle wheels and also by environment.

(Fig. 2.3.1- dot.ca.gov, 2001) Typical pavement structure

To perform effectively road pavement must not depress, crack, rut or wash away.

The typical stress and distresses of road-pavement and the structure are illustrated

by below figures.

(Fig. 2.3.2- dot.ca.gov, 2001) Load distribution and pavement deflection under loads


2.4 Pavement Types

Pavement of a road is an engineering structure composed of several layers

(courses) of materials. Top layers are to withstand the intensity of stress from traffic

loads while the underneath stand supportively as foundation structure.

There are mainly two types:

Flexible pavements ( constructed with asphalt concrete materials)

Rigid pavements ( constructed with Portland / hydraulic cement

concrete)

Composite pavements (combination of above

both) typically, composite pavements is asphalt

overlays on top of concrete pavements.

In addition to those there are natural

roads formed with earthen materials

such as soil, gravel or aggregate

compacted to dense course.

This project’s paper has been focussed and discusses towards the flexible

pavements and asphalt concrete.


2.5 Asphalt Concrete Pavement Structure

A typical AC pavement structure may consist of (from bottom) subgrade, subbase,

AC-base course and AC-surface layer respectively. Subgrade is stabilised and

strengthen. Subbase is constructed with good earth, gravel or coarse materials.

Figures below illustrate typical formation of the total structure.

(Fig. 2.5.1) (Fig. 2.5.2- tpub.com, 2009)

(Fig. 2.5.3) Wheel load distribution / spreading Pavement deflection under loads

(dot.ca.gov, 2001)

Pavement structure is so built to meet and to distribute the stresses under the loads.

AC mixture of quality aggregates and bitumen binder provide the needy

characteristics responding to the conditions applied on the pavement.


2.6 Pavement System Types

The pavement system is to be stable not only to provide a smooth surface but to

carry loads and performing the functions not failing at all conditions dynamic or

climatic. Therefore pavement system is to be developed in order to meet those

functions. The components are basically the same. AC is the main material. Under

shown figures may to explain how defer pavement systems to thus.

(Fig. 2.6.1) Basic components of a typical pavement system-

(pavementinteractive.org, 2010)

(Fig. 2.6.2) Common variations of Asphalt Concrete Pavement sections-

(pavementinteractive.org, 2010)


Information source- pavementinteractive.org, 2010


2.7 Components of Pavement’s elements

Sub-grade (roadbed) course: natural material that serves as the foundation

of the pavement structure,

Sub-base course: above the sub-grade, superior to sub-grade course,

Base course: above the sub base, granular materials such as crushed

stone, crushed or uncrushed slag, gravel, and sand,

Surface course: upper course of the road pavement, should withstand tire

pressures, resistant to abrasive forces of traffic, provide skid-resistant driving

surface, prevent penetration of surface water

When wheel loads exert pressure on the pavement permanent deformations may

happen to develop due to vertical compressive stress to the pavement layers;

wearing course, binder course, and if any bituminous layer below it respectively.

This vertical pressure results tensile stress to each of those layers. Lowest layers

will be subjected to smaller tensile stress due to vertical pressure distribution

increases over a larger area. Unbound granular materials (exist at a relaxed mode

but stands for vertical pressure) in the base course or sub base do not hold

significant tensile stress and they do not require effective elastic modulus hence.

This situation can be illustrated by flowing figures: (training.ce.washington.edu, 2010)

(Fig. 2.7.1) Pavement components, load distribution and tress distribution


Chapter 3. ASPHALT CONCRETE PAVEMENT DESIGN

3.1 Philosophy of Pavements

Pavements are alive structures. They are subjected to moving traffic loads that are

repetitive in nature. Each traffic load repetition causes a certain amount of damage

to the pavement structure that gradually accumulates over time and eventually leads

to the pavement failure. Thus, pavements are designed to perform for a certain life

span before reaching deterioration. Hence, they have a certain design life span after

which rehabilitation will be the need. Nowadays recycling the pavement.


3.2 Design criteria

Characteristics and performance of Asphalt Concrete (AC) mix are prominent in AC

pavement design. The AC mix design also is to be so considered in this regard.

Choices of AC type and mix design have to be appropriate and compatible to the

overall pavement purposes.

The structure of a flexible pavement is assumed to be a linear elastic multi-layer

system. The pavement materials are assumed to be homogeneous and

characterised by their elastic modulus and Poisson’s ratio. The primary criteria for

structural design are:

The limitation on compressive strain in the surface of the sub-grade. If

this is excessive, permanent deformation will occur at the top of the

sub-grade leading to deformation at the pavement surface.

The limitation on horizontal tensile strain in any bound layer. Typically,

tensile strain achieves its maximum value at the bottom of the layer.

Excessive strain will cause cracking of the layer.

At present there are no explicit pavement design criteria to control rutting in asphalt

layers. Rutting is controlled by evaluating the deformation resistance of the asphalt

as part of the mix design procedure. The pavement strains under traffic loading are

illustrated in the figure. (dot.ca.gov, 2001)

(Fig. 3.2.1) Load pressure and deflection result tensile and compressive stresses


3.3 Asphalt Concrete Characterisation in Pavement Design

AC is a mixture of bitumen (binder) and aggregates, which is spread and compacted

in hot form to form a pavement layer. Bitumen is usually conventional but for special

applications it may be modified by the addition of specific polymers. The strength

/stiffness of AC is depend of the friction between the aggregate particles, the

viscosity of the binder and the cohesion within the product due to the binder itself.

Adhesion between the binder and the aggregate is a vital characteristic required.

These frictional and adhesion characteristics are the vital to resist the distresses of

AC layers commonly rutting, shoving and cracking due to fatigue.

3.4 Principles and Aspects of Pavement Design

Pavement design is the process of developing the most economical combination of

pavement layers (in relation to both thickness and type of materials) to suit the soil

foundation and the traffic to be carried during the design life.

The tensile and compressive stresses induced in a pavement by heavy wheel

loads decrease with increasing depth. This permits the use, particularly in

flexible pavements, of a gradation of materials, relatively strong and

expensive materials being used for the surfacing and less strong and cheaper

ones for base and sub-base.

The pavement as a whole limit the stresses in the sub-grade to an acceptable

level, and the upper layers must in a similar manner protect the layers below.

(Fig. 3.4.1) Aspects of Pavement Design- (onlinemanuals.txdot.gov)


3.5 Design Parameters

• Subgrade

• Loads

• Environment

(Fig. 3.5.1-

onlinemanuals.txdot.gov)

Subgrade: Characterized by strength and stiffness / California Bearing Ratio (CBR)

o Measures shearing resistance

o Units: percent

Resilient Modulus (MR) Measures stress-strain relationship, Units: psi or Pa,Typical

values: 3,000 to 40,000 psi

Some Typical CBR Values

Classification CBRMR

(psi)Typical Description

Good ≥ 10 20,000Gravels, crushed stone and sandy soils. GW, GP, GM,

SW, SP, SM soils are often in this category.

Fair 5 – 9 10,000Clayey gravel and clayey sand, fine silt soils. GM,

GC, SM, SC soils are often in this category.

Poor 3 – 5 5,000Fine silty sands, clays, silts, organic soils.CL, CH, ML,

MH, CM, OL, OH soils are in this category.

In addition to above wheal loads concerning axel and configuration, repletion of

load, vehicle speeds and traffic distribution are also involved.


LEF Example: The standard axle weights for a standing-room-only loaded Metro

articulated buses (60 ft. Flyer) are:

(Fig. 3.5.3)

Axle Empty Full

Steering 13,000 lb. 17,000 lb.

Middle 15,000 lb. 20,000 lb.

Rear 9,000 lb. 14,000 lb.

Using the 4th power approximation, determine the total equivalent damage caused by

this bus in terms of ESALs when it is empty. How about when it is full?

Environment: Temperature extremes, climate, weather (rains and frost action)

A road should be designed and constructed to provide a riding quality acceptable for

both private cars and commercial vehicles and must perform the functions i.e.

functional and structural, during the design life.

Ride quality

Shape, cross fall or drainage

Noise levels

Skid resistance

Waterproofing

Surface integrity

Surface reflectivity

Appearance


3.6 Pavement Structure

Surface

course

Base

course

Subbase

course

Subgrade

(Fig. 3.6.1- tpub.com, 2009)

Recommended thickness:

(Fig. 3.6.2-tpub.com,2009)

Recommended thickness (design catalog the Washington Asphalt Pavement

Association WAPA)

(Fig. 3.6.2) Pavement design is to account for the entire spectrum of traffic loads.


Pavement Thickness Design is the determination of required thickness of various

pavement layers to protect a given soil condition for a given wheel load. Pavement

Thickness Design is the determination of thickness of various pavement layers

(various paving materials) for a given soil condition and the predicted design traffic in

terms of equivalent standard axle load that will provide the desired structural and

functional performance over the selected pavement design life.

Dense-graded Gap-graded Open-graded

(Fig. 3.6.3- civil.iitb.ac.in) Types of Flexible Pavements

3.7 Design Life

The concept of design life has to ensure that a new road will carry the expected

volume of traffic within that life span without failures or deterioration. For roads in

Britain the currently recommended design is 20 years for asphalt concrete

pavements. If the rut depth increases beyond 10mm or the beginning of cracking

occurs in the wheel paths, this is considered to be a critical stage and if the depth

reaches 20mm or more or severe cracking occurs in the wheel paths then the

pavement is considered to have failed, and requires a substantial overlay or

reconstruction.


3.8 Stress Distribution Factors in Asphalt Pavements

Following are the main factors considered and counted in structural design of

pavement.

Load related responses:

Vertical ( compressive)stresses and strains,

Shear stresses and strain,

Radial ( compressive or tensile) stresses and strain

Temperature induced responses:

Shrinkage stresses and strains ( temp: cycling,

Low temperature cracking,

Thermal cracking

Critical responses:

Horizontal tensile stress/strain at the bottom of bound layers,

Vertical compressive stress/strain at the top of sub-grade

Calculating responses:

Using equations,

Graphical solutions,

Elastic layer computer programs

Thermal Cracking Model

Low temperature cracking,

Thermal fatigue cracking,


(Fig. 3.8.1) Asphalt concrete layers paving to the thicknesses

(pavementinteractive.org,2011)

Adequately designed pavement with best construction practices and quality control

can serve the purposes longer.


Chapter 4. ASPHALT CONCRETE

4.1 What is Asphalt Concrete

Asphalt concrete (AC) “well known as asphalt” (more technically “ Asphalt Concrete”)

is a road pavement construction material which consists of blends of fine and coarse

mineral aggregates and bitumen as a mixture. Bitumen acts as a cement to bind the

aggregates. AC is designed and produced to provide optimal physical properties to

perform well structurally, and for durability in service of the pavements. The

performance of AC is depended on both to the physical properties of the individual

constituents and of the combined mixture. Strength, flexibility and stiffness are the

main properties.

AC is widely used for road pavement constructions. Asphalt concrete provides a

resilient, waterproof, load distributing flexible structure (layer or a course) that

protects the base course against water and traffic loads. It has to be thoroughly

compacted to provide a stable, watertight course. The flexibility of asphalt concrete

permits minor adjustments in the pavement course due to traffic loads and other

environmental effects.

(Fig. 4.1.1) Schematic view of Asphalt Concrete


4.2 Components / Constituents

Bitumen

Aggregate ( Coarse material, Fine material and Filler )

Air voids

By Weight %:

Coarse aggregate - 62,

Fine aggregate - 28,

Filler - 5,

Bitumen - 4.5 ~ 5.2

By Volume %:

Coarse aggregate - 55,

Fine aggregate - 25,

Filler - 5,

Bitumen - 13.3

Air Voids - 3 ~ 7


4.3 Properties of Asphalt Concrete

The mix proportions for a properly compacting AC paving mixture are determined in

the laboratory during mix design testing. This is importantly necessary to provide the

mixture an ability to resist the potential damaging effects during its response when

and after paving to serve as the pavement. To perform properly in the field, a well-

designed asphalt concrete mixture must be used within the proper temperature

range. It must be adequately compacted. Asphalt concrete paving mixtures should

exist with the following properties:

Stability – Sufficient mix stability is required to satisfy the demands of traffic

without distortion or displacement.

Air Voids – Percentage of void spaces within the mix sufficiently exist to allow

for a slight additional compaction under traffic and any expansion due to

temperature increases, without flushing, bleeding or loss of stability. A void

content between 3 to 5% assures proper mix.

Stripping Resistance – Ability to resist the loss of tensile strength due to

bitumen stripping from the aggregate. Stripping cause disintegrating aggregate.

Resilient Modulus – Better stiffness of AC mixture under loading conditions.

Low resilient modulus would be susceptible to deformation, whereas a high

resilient modulus indicates a brittle mixture.

Desired Density – The density of a properly designed paving mixture

compacted under prescribed laboratory compaction procedures. Measure of

the density of a paving mixture compacted in the field in accordance with the

specifications.

4.3.1 The desirable properties for Asphalt concrete Pavement:


Resistance to permanent deformation: The mix should not distort or be

displaced when subjected to traffic loads and at high temperatures.

Fatigue resistance: Should not crack when subjected to repeated loads.

Resistance to low temperature cracking is important in cold conditions.

Durability: Should contain sufficient binder for an adequate film around the

aggregates. Compacted mix should not have very high air voids which

accelerates aging process.

Resistance to moisture-induced damage.

Skid resistance.

Low noise and good drainage properties: It is important if the mix is to be

used for the surface (wearing) course.

4.4 Density is the significant property

Density is one of the most important parameters of AC. Acquire of proper density of

AC layers is very important to produce a stable, durable and waterproofing course. If

satisfactory density is not obtained failures may occur suddenly or gradually due to

densification under traffic or durability problems such as oxidation and ravelling.

Therefore AC is to contain specified ( 3 – 5 %) air voids to prevent rutting due to

plastic flow. Density of AC pavement is subjected to vary throughout its life.

Therefore even after years of traffic flow the voids exist must be high enough to

prevent plastic flow and low enough to prevent permeability of water.

There are three primary methods of specifying density: 1. Percent control strip, 2

Percent of lab density and 3. Percent theoretical maximum density.

4.4.1 Desired Density & Lab Test


All three methods can be used to obtain satisfactory compaction if used correctly.

The voids in an asphalt mixture are directly related to density; thus, density must be

closely controlled to insure that the voids stay within an acceptable range. The initial

in-place air voids must be below approximately 8% and the final in-place air voids

must be above approximately 3% . High voids lead to permeability of water and air

resulting in water damage, oxidation, ravelling and cracking. Low voids lead to rutting

and shoving of the asphalt mixture. Most mixtures are designed to have 3-5 percent

air voids when compacted.

Asphalt Concrete test for Density AND Bitumen Content

Tests were done from the sample obtained from the under detailed Project. Details of test carried out followed.

Company- Galliford Try

Supervisor- City of London-Highway Engineering Department- Guildhall, PO Box 270, London EC2P 2EJ

Project: Beam Rich

Site: Pavement Construction on Consul Avenue, Dagenham, London

Name of Site Agent (assisted) : Mr. A. Madushanath

Sample Lot No: BRC / 1

Date of Sample collection: 23.04. 2011

Date of testing: 25.04.2011

Lab: BAM, Richies

Extraction and Bitumen Content


Test No. BRC/1Weight of Bowl W1 (g) 2890.1Weight of Bowl + Sample

W2 (g) 4294.9

Weight of Sample W3 = W2 - W1 (g) 1404.8Weight of Bowl + Extracted Aggregate W4 (g)Including Dust Recovered for Solution 4239.8

Weight of Extracted Aggregate W5 = W4 - W1 (g) 1349.7Weight of Dry Filter Paper Before Test W6 (g) 14.1Weight of Filter Paper After Test W7 (g) 16.0Weight of Dust Accumulated In Filter paper W8 = W7 - W6 (g) 1.9Weight of Total Extracted Aggregate W9 = W5 + W8 (g) 1351.6Weight of Bitumen W10 = W3 - W9 (g) 53.2

Percent of Bitumen By Weight of ix Bitumen % = W10

W3

× 100 (%)

3.79

Specified Bitumen Content (%)

3.5 – 4.0

Therefore the Bitumen content in the sample is within the specified limit.

Pavement Density and Compaction

Sample from pavement (core)

Specimen No

In airIn

waterSSD in air

Bulk volume(cm3)

Bulk densit

y Pavement compaction ( % )

Measured thickness of

core

i j k l=k-i m=i/l n=m/h*100

BRC/1/11835.

11070.

11842.

1772 2.377 99.7 105.5

BRC/1/2 903.1 525.2 906.6 381.4 2.368 99.3 56.8BRC/1/3 638.7 364.1 642.0 277.9 2.298 96.4 40.8BRC/1/4 918.4 528.3 922.6 394.3 2.329 97.7 55.2

BRC/1/51270.

8739.5

1274.8

535.3 2.374 99.6 72.2

Marshell specimen from plant mixThicknes

s (mm)

In air In water SSD in airBulk volume(cm3)

Bulk density (Gmb)

d e f G=f-e H=d+g

63.9 1209.4 705.6 1212.3 506.7 2.38764.0 1204.6 701.9 1207.7 505.8 2.38263.8 1200.0 698.2 1201.9 503.7 2.382

2.384 GRADINGS EVALUATION


Sieve Weight Percentage PercentageSpecified

Limits Job MixSize Retained Retained Passing Min Max Min Max(mm) (g) (%) (%) (%) (%) (%) (%)25.0 0.0 0.0 100.0 100 100 100 10019.0 0.0 0.0 100.0 88 100 88 1009.5 484.7 35.9 64.1 54 80 57 69

4.75 328.4 24.3 39.8 34 56 36 482.36 112.4 8.3 31.5 21 38 29 381.18 70.0 5.2 26.3 15 33 22 330.60 61.8 4.6 21.8 10 26 14 240.30 109.4 8.1 13.7 6 20 7 170.15 67.8 5.0 8.7 3 13 2 10

0.075 63.9 4.7 3.9 1 7 1 5Pan 53.2

Total 1,351.6

Aggregate gradation limits Evaluation

The test results were found to be compatible in accordance to the specified values.

4.5 Stability of the Asphalt concrete


AC stability depends on the strength and flexibility of the mixture and the degree of

compaction. The strength must be sufficient to carry the load without shear

occurring between particles remaining intact. The main contributor to strength is

friction between particles. Flexibility is also important as to receive imposed load

distribution allowing deflections slightly but no cracking or permanent deformation

take place. Strength and flexibility are evaluated by various tests.

4.6 Safety

Safety is very important for the surface course. This involves skid resistance and

drainage of water from the surface. Skid resistance is enhanced by using smaller

sized, very hard aggregates for the surface course. This provides more points of

contact for the development of friction forces. Open-graded surface courses are

used in very heavy traffic areas to allow immediate drainage of rainwater before it

can result in hydroplaning. These pavements also increase skid resistance due to

the coarse texture provided.

4.7 Durability


Durability of the asphalt concrete is critical to ensure that it maintains the stability

and skid resistance properties for the design service life. Asphalt ages, and

pavements become denser with time and traffic. Pavements fail due to:

changes in the aggregates

permanent deformation or rutting

cracking, either due to fatigue, or low temperatures

bleeding of asphalt to the surface

4.8 Characterization

The structural performance of an asphalt pavement or its ability to withstand the

destructive effects of traffic and environment is defined in terms of the following

engineering properties of the AC mixture.

Deformation or stress-strain characteristics ie. elastic modulus (stiffness)

Primary structural distress modes: fatigue excessive permanent deformation

(rutting). The elastic stiffness and fatigue life of a mix are primarily dependent

on the stiffness of the binder

5. ASPHALT CONCRETE MIX TYPES

5.1 Asphalt Concrete to use in Hot or Cold weather conditions

Asphalt Concrete is usually not available readily. Due to high viscosity of the binder

bitumen at the ambient temperature (atmospheric) it needs heating ( 175 c) to mix

properly with the aggregates. And storage of the mixtures are not suitable due to

hardening thereby no workability exist for paving. Hence, required AC mixtures are

mechanically ( by mixing plant) produced, transported and laid at worm conditions.

However for cold weather needs AC is produced and used at cold conditions.

Emulsified binder ( liquid form bitumen) is used in cold producing. Types of AC

mixtures thus prepared for those conditions are:

5.1.1 Hot mix asphalt concrete (HMA)


is produced at 160 degrees Celsius which helps to decrease viscosity of the binder

and any moisture of the aggregates at the production process making a properly

mixed AC.

5.1.2 Warm mix asphalt concrete (WMA)

It is produced at a reduced temperature which is made possible by adding

bituminous emulsion or waxer to make the binder to a mixable viscosity.

Environmentally and economically friendly but quality not up to HMA.

5.1.3 Cut-back asphalt concrete

Cut-back bitumen binder (Bitumen dissolved in kerosene oil and made to liquid form)

is mixed with the aggregate. Reduced viscosity of the binder makes proper mixing

and AC can be laid compacted. Kerosene later evaporates leaving the bitumen

properties to get harden. Air polution is than the other forms

5.1.4 Cold Mix Asphalt Concrete

It is produced at the normal air temperature by mixing the aggregate with

(emulsified) bitumen of liquid state binder. The emulsion gets break after water

evaporates back, and the mix will ideally achieve the properties of normal AC but not

as to the product of HMA.

(wisegeek.com/what-are-different-types-of-asphalt.htm, 2011)

Chapter 6. ASPHALT CONCRETE MIX GRADES


http://www.wisegeek.com/what-are-different-types-of-asphalt.htm

6.1 Grading for deferent Function

It is important to use the proper compatible asphalt mixtures / types in the layers of

pavement to response positively towards the expected functions. Properties such as

durability, resistance to fatigue cracking, rutting resistance, strength to withstand the

traffic loads and the environment distresses must prevail in the mix.

To meet those conditions, varying needs, services and construction of different

layers in the pavement structure asphalt concrete has to be compatibly differ with the

characteristics and properties. AC is graded for those uses and in paving of surface

course, binder course and base course.

The most common type of AC using for flexible pavement is hot mix asphalt (HMA).

HMA is designed and produced by significant methods to different grades those to

meet as detailed above. The prominently using grades are:

Dense-graded

Hot Rolled AC

Stone matrix asphalt

Open-graded

Porous AC

(Fig. 6.1.1) Asphalt concrete grading samples-

6.2 Dense graded Mix


A dense-graded mix (see above figures) is a well-graded HMA intended for general

use. When properly designed and constructed, a dense-graded mix is relatively

impermeable. They are further classified as Fine-graded or Coarse-graded

Dense graded HMA contains all grades of aggregates (coarse and fines) thus

providing structural ability to stress transmission distributed over a considerable area

of the course. Suitable for all pavement layers and for all traffic conditions. They

work well for structural, friction, levelling and repairing needs.

6.3 Hot Rolled Asphalt Concrete

This is very common AC mix using for pavement layers. It imparts recommended

strength and durability. The strength of this material is from the stiffness produced as

a result of the combination of a 50pen binder, aggregate and sand blended properly.

The correctly designed binder content and low void content of this mixture

results in a very durable material, with a "common" life of 20 years or more.

(Fig. 6.3.1- eecongress.org,) Close Graded Mixture

6.4 Stone Mastic Asphalt Concrete (SMA)


"The aggregate grading is similar to that of Porous Asphalt, but with the voids filled

with mortar." "The process of designing a SMA mixture involves adjusting the

grading to accommodate the required binder and void content rather than the more

familiar process of adjusting the binder content to suit the aggregate grading."

A very high binder content is essential to ensure durability and laying characteristics.

(Fig. 6.4.1) Interlocked aggregate (Fig. 6.4.2) Stone matrix asphalt (SMA)

Where heavy traffic is operated and to resists rutting stone, matrix asphalt is

recommended. Stone matrix asphalt is comparatively at a higher cost as the mixing

and the laying operation are expensive. To obtain a higher quality of the binder

material modifiers and fibber material are added. However stone matrix asphalt

concrete is durable.

(Fig. 6.4.3) SMA Lab Sample (Fig 6.4.4) SMA surface

(Information resource- eecongress.org)

6.5 Open graded Mix


Open graded porous AC exhibits degree of porosity to permeable of surface water

drainage. It is recommended porous surface course material need be laid on an

impervious binder course (basecourse) or thick tack-coat / bond coat to prevent

water entering the road pavement surface from the underneath. Porous surface

course bituminous mixtures must be laid on a strong and impervious base layer.

Although this AC cause less surface tire and reduce spray, there have been

problems in laying, and durability. Its life is much shorter than a hot rolled asphalt

wearing course and there are problems with winter maintenance as porous asphalt

needs salting at higher rates than impervious materials.

Porous AC when paved allows water to leak through. It is made and applied

with conventional asphalt paving equipment but for porous AC, the smaller

particles are left out and the percentage of tar is reduced. This provides

bonding while allowing spaces through which the water may pass.

(Fig 6.5.1) Cross-section of Typical Porous Pavement, including Base Courses


(Fig 6.5.2) Porous Asphalt Concrete (Fig 6.5.3) Open-Graded Asphalt Concrete

Open-graded HMA mixture is designed to be water permeable. Open-graded mixes

use only crushed stone (or gravel) and a small percentage of sands. The two most

typical open-graded mixes are:

Open-graded friction course (OGFC). Typically 15 percent air voids and no

maximum air voids specified. Used for only surface course

Asphalt treated permeable bases (ATPB). OGFC is used only under dense-

graded HMA, SMA or PCC for drainage.


(Fig 6.5.4) OGFC Surface (Fig 6.5.5) OGFC Lab Samples

Improve skid resistance due to rapid removal of water from the aggregate tyre

interface. They reduce tire splash/spray in wet weather. The high air void contents

reduce tire-road noise considerably.

However open-graded friction course is susceptibility to studded tire wear. Tire studs

will tend to dislodge aggregate from the mix in the wheel paths forming a depression.

After 2-3 years the surface voids of the OGPA start to become chocked with debris

or dust which reduces the pavement’s ability to drain water. Once this happens the

effectiveness of the OGPA reduces. Needs back-flushing system or cleansing.

(Information source-mineralproducts.org,2002)


Mix type selection Guide for perpetual pavements

(Information source-mineralproducts.org,2002)


Chapter 7. BITUMEN

7.1 What is Bitumen

Bitumen (usually called “asphalt” chemically termed “bitumen”) is widely used in

pavement construction. For AC it is binder “cement”. Its mechanical properties are

more complex than typical civil engineering materials. Bitumen can be described as

a viscous liquid, or a solid, consisting essentially of hydrocarbons and their

derivatives, which is soluble in trichloroethylene and is substantially non-volatile and

softens gradually when heated. It is black or brown in color and possesses

waterproofing and adhesive properties. Bitumen is obtained by refinery process from

petroleum crude oil. This process is discussed under chapter 8.

It is the most important material for AC production. The bitumen binder content of an

AC mixture is generally 5 to 6 percent. It as a cementing agent coats and binds the

aggregate particles together at its liquid state by heating. Asphalt also can be

dispersed in water with the aid of an emulsifying-agent or solvent to make it liquid. It

is called “asphalt emulsion”.

The properties of asphalt binders are often improved or enhanced by using additives

or modifiers to improve adhesion (stripping resistance), flow, oxidation

characteristics, and elasticity. Asphalt binders are classified by methods of:

penetration or viscosity. Penetration graded asphalt binders include 40-50, 60-70,

85-100, 120-150, & 200-300 grades. Viscosity graded asphalt binders include AC-

2.5, AC-5, AC-10, AC-20, AC-30, & AC-40 grades.

A viscosity / temperature may be obtained from the asphalt producer. Figure shown

below is an example of this curve. The temperature of the asphalt at 170 centistokes

will result in the ideal mixing temperature to provide adequate coating film thickness.

The temperature at 280 centistokes is the ideal compaction temperature. The

asphalts with flatter slopes on this curve are less susceptible to thermal cracking.


7.2 Bitumen as Ideal Binder

The most important property of bitumen as a binder in AC is the way its stiffness

(viscosity) changes with temperature. Ideally a binder is to be stiff enough at

elevated temperatures so that it can resist deformation while flexible enough at low

temperature restricting cracking. An ideal binder must exhibit the following

properties:

Sufficient stiffness/rigidity to minimize the rutting during worm

condition. In addition, it must have positive effect on the fatigue life

of the bituminous hot mixture.

Flexible enough at cold temperature to avoid thermal cracks.

It must exist the pumping / liquid state as a binder faster during

mixing and hardness (or viscosity) should be decreased to facilitate

compaction.

Bitumen having prominent characteristics such as waterproofing, versatile,

thermoplastic, viscoelastic and adhesive acts as the glue (cement) and holds the

aggregates intact. It is very acceptably used for AC for its so prominent

characteristics which can meet the AC purposes specially the pavement needs.

Although bitumen’s usual state is solid or semi-solid at ordinary temperatures it can

be liquefied by applying heat or dissolving in solvents (cut-back) or emulsifying

(emulsion). Bituminous binders of the various grades are characterized by their

physical properties, which directly describe how it will perform as a constituent in AC

mixtures.


7.3 Composition of Bitumen

Chemical analysis have shown that asphalt contains mainly

Carbon - 83%

Hydrogen - 10%

Oxygen - 5%

Nitrogen & Sulphur - 1%

Vanadium, Nickel, Aluminum & Silicon etc. – 1%

7.4 Properties of Bitumen

7.4.1 Adhesiveness:

The most important property related to AC. It depends upon the nature of aggregates

when using for AC production. Bitumen of liquid state can adhere the worm

aggregate effectively. This “aggregate-binder” property can be enhanced by

additives or modifier agents when an as required in AC productions.

7.4.2 Impermeability:

Water resistance property of asphalt. Even a very thin film or a coating can provide

an excellent water barrier. The degree of impermeability depends also upon the

nature of aggregate specifically fine materials. Solubility of bitumen in water is

negligible.

7.4.3 Viscosity:

Liquidity / flow property of asphalt significantly important. Bitumen must necessarily

be of high viscosity ( liquid form / softer) at the temperatures during AC production so

as to effectively coating the aggregates to bond together due to the thermoplastic


property. And there must not be any flow (less viscosity / harder) after AC is paved.

Having this property bitumen gives a excellent binder service while behaving flexible.

7.4.4. Consistency:

The resistance to flow. It changes according to the volatile substances’ contents in

the bitumen and also as the temperature varies. Consistency of bitumen is

expressed as "the distance in 1/10th of mm that a standard needle vertically

penetrates a sample under standard conditions of load, time and temperature." It is

the measure to grade the types of bitumen.

7.4.5 Durability:

Bitumen counts the life time of pavement structure. The volatile materials in the

bitumen can be reduce or loss through evaporation and oxidation due ultra-violet

radiation. It effects the flexibility consequently the durability.


7.5 Uses of Bitumen

As a binder (a cementing material) to set aggregates together asphalt has its

greatest use in road pavements construction and maintenance as written above and

below in this report. Some air ports ground surface course are built with asphalt

materials.

Emulsions are dispersions of very small drops of bitumen in water. When it is not

desirable to use fire or heating methods to boil asphalt it is made to use in so-called

cold applications, in liquid form as emulsion. A satisfactory emulsion is smooth in

appearance, usually brown in color. An obvious advantage of emulsions over other

bituminous products is that they are easy to handle and apply. Curing involves

primarily a loss of water by evaporation. its stability depends upon many factors such

as asphalt concentration, size and distribution of asphalt droplets, freezing of the

water and the nature of the stabilizing agent.

Cutback asphalt is a solution of the asphalt in a suitable solvent like kerosene or

petrol. After application of cutback asphalt to the solid surface, the solvent

evaporates leaving the asphalt film to act as a coating. Numerous solvents are

sufficiently volatile and are good solvents for asphalt.


Chapter 8. CRUDE OIL RFINERY AND BITUMEN EXTRACTION

Bitumen is an oil based substance. It is the end product at the distillation process of

oil refinery. Bitumen being the major material within the pavement industry it is really

worthy to understand the refinery systems / process from which it is manufactured

and how.

8.1 Petroleum Crude Oil Refinery

Refinery is a very distinctive longer process of distillation the crude oil fractionation

into petroleum hydrocarbon groups. Crude oil originally extracted from the deeper

grounds is a black, muddy liquid.

Crude oil is heated in a boiler and transferred to a distillation tower. The alkenes

(substances) of it are made to evaporate in the order of their boiling points,

commencing from the lowest, being heated liquefied petroleum gas (LPG), which is

lighter and can easily evaporate, followed by naphtha, gasoline, kerosene, jet fuel,

and light oil, in that order, are extracted from a distillation system, and heavy oil and

asphalt (bitumen) remains at the end. Heavy oil is used as fuel for ships; bitumen is

used to pave roads.


ORDER OF THE BOILING POINTS OF ALKANES PRODUCTS BY REFINERY SYSTEM- (black-

tides.com,2011)

.

(Fig 8.1.1) Schematic view of the Petroleum Distillation Process, (black-

tides.com,2011)


(Fig 8.1.2) Schematic view of the Petroleum Distillation temperature status.

(nyk.com,2011)

(Fig 8.1.3) Distillation temperature of petroleum products. (elmhurst.edu,2011)

8.2 Refinery Processes


The oil is heated and the resultant vapours rise up the tower. The vapours cool as

they rise and condense onto trays. The lightest compounds condense at the top of

the tower and are taken off as LPG (liquefied petroleum gas). The oil then undergoes

further processing prior to distribution. The octane rating is increased to improve

engine ignition. Sulphur is removed because when products are used the sulphur

compounds emitted would smell of rotten eggs and dissolve in rain to form sulphuric

acid which would contribute to the problem of acid rain. Other strong smelling

compounds are also removed. Heavy residue is taken off at the base of the tower

and reprocessed. In the fluid catalytic cracker (FCC) the heavy oil is distilled again,

using a chemical catalyst this time, to produce gasoline and diesel. The heaviest

sticky residue is redistilled in the vacuum distillation unit then taken to the Lubricants

Zone where it is processed to make bitumen, lubricating oils and wax.

Chapter 9. ASPALT EMULSION

9.1 What is Emulsion

Sometimes asphalt emulsion is used for the production of AC. Bitumen binder

necessarily to be of liquid form to produced AC. It is usually done by heating. Where

heating of asphalt is not possible or not desirable the binder has to be in liquid form

at the normal temperature which it is to be used.

Bitumen can be mixed into water by specialized equipments with controlled

conditions using chemical emulsifying agents and additives. Dispersion of the

bitumen in the water with help of emulsification agent is the mechanism of producing

asphalt emulsion.


9.2 Asphalt Emulsion Preparation

An emulsion is a dispersion of small droplets of one liquid in another liquid.

Emulsions can be formed by any two immiscible liquids, but in most emulsions one

of the phases is water. Emulsions can have more complex structures. In multiple

emulsions, the disperse phase contains another phase which may not have the

same composition as the continuous phase.

Types of emulsions


(Fig 9.2.1) O/W emulsion W/O emulsion multiple W/O/W

Standard bitumen (asphalt) emulsions are normally considered to be of the O/W type

and contain from 40% to 75% bitumen, 0.1% to 2.5% emulsifier, 25% to 60% water

plus some minor components. The bitumen droplets range from 0.1–20 micron in

diameter. They are brown liquids with consistencies from that of milk to double

cream, which depend mostly on the bitumen content and the particle size. Some

bitumen droplets may contain smaller water droplets within them; a better description

of asphalt emulsion would be a W/O/W multiple emulsion. The viscosity of the

emulsion and especially changes in the viscosity of the emulsion during storage are

strongly influenced by this internal water phase.

(Transportation Research Board,Characteristics of Bituminous Materials Committee,August 2006)

9.3 Emulsion Technology

Bituminous emulsions form the basis for many paving applications in the asphalt

Industry. Their rheological (i.e., flow) properties often dictate the uses for which they

are suitable. Even when rheological properties are not critical in the final product,

they influence the workability of the emulsion as it is applied in the field. The

advantages of asphalt emulsion compared to hot asphalt and cut back binders are

related to the low application temperature, compatibility with other water-based

binders like rubber latex and cement, and low-solvent content. Faster-setting

surface treatments, quick-drying tack coats, penetrating emulsion primes


that are superior to cut backs, and cold-mixed materials with improved properties.

(Fig 9.3.1) Schematic views of Asphalt emulsion preparation model sample

The basis of emulsification is the creation of small (1-5 micron) particles of asphalt

that are coated with a chemical that allows the particles to stay apart. The emulsion

must, however break back to asphalt films to be able to perform its function of

coating, water proofing adhesion etc.

(Transportation Research Board, Characteristics of Bituminous Materials Committee, August 2006)

9.5 The Setting Process

Emulsified asphalt must revert to a continuous asphalt film in order to act as cement

in road materials. This involves flocculation and coalescence of the droplets and

removal of the water.

Evaporation and absorption of water by the aggregate may be the main breaking

mechanism for very slow-setting emulsions, but in most cases chemical reactions

between the aggregate and the emulsion contribute to the emulsion setting and it is

not necessary for all the water to evaporate before curing takes place.


The strength of the reaction of emulsion with aggregate is in many cases sufficient to

squeeze the water from the system. Clean water can be seen separating from the

mixture. The speed of these setting and curing processes depends on the reactivity

of the emulsion, the reactivity of the aggregate and environmental factors, such as

temperature, humidity, wind speed, and mechanical action.

(Fig 9.5.1) Emulsion setting Micrograph of asphalt

(Fig 9.5.2) Stages in the breakdown of emulsions

9.6 Classification of Asphalt Emulsion

It is classified on the basis of the charge-signs on the droplets and to their reactivity.

Cationic emulsions have droplets which carry a positive charge. Anionic emulsions

have negatively charged droplets.

Rapid-setting (RS) emulsions set quickly when contact on aggregates of low-

surface area, such as the chippings used in chip seals (surface dressings).

RS emulsions are reactive and are used with unreactive aggregates.


Medium-setting (MS) emulsions set less quickly that they can be mixed with

aggregates of low surface area, such as those used in open-graded mixes.

Slowsetting (SS) emulsions will mix with reactive aggregates of high surface

area. SS emulsions are unreactive and are used with reactive aggregates.

Cationic RS, cationic MS, and cationic SS emulsions are denoted by the codes CRS,

CMS, and CSS, whereas anionic emulsions are called RS, MS, and SS, followed by

numbers and text indicating the emulsion viscosity and residue properties.

9.7 Variables affecting Asphalt Emulsion

There are many factors that affect the production, storage, use, and performance of

an asphalt emulsion. The variables do significant affect are:

Chemical and physical properties of bitumen,

Nature, properties and concentration of the emulsifying agent

Manufacturing conditions temperatures and pressures

Ionic charge on the emulsion particles

Addition of chemical modifiers.

9.8 Advantages of Asphalt Emulsion

Asphalt Emulsion ie. Emulsified bitumen is of lower viscosity than normal bitumen

itself and hence possible to use at lower temperature reducing emissions and energy

consumptions. They are economical and environmentally friendly than using cut

back asphalts. Emulsions are water-based and in many cases can be diluted further

with water for applications such as dust control and priming.

The main advantage of emulsions can be summarized in terms of:


Energy Conservation and Pollution Control

Safety and Ease of Use

Improvement in adhesion to aggregates

Extensive applications.

Economy of materials

Versatility and Performance

(Transportation Research Board,Characteristics of Bituminous Materials Committee,August 2006)

Chapter 10. AGGREGATE

10.1 Use of Aggregate

"Aggregate" is the mineral materials such as sand and crushed stone that are used

with a binding agent to form compound materials like hot mix asphalt (HMA)

Aggregate accounts for about 75 to 85 percent of HMA by total volume of mixture

(about 92 to 96 percent by total weight of mixture).


Aggregates used for asphalt concrete mixtures have to be in proper grading,

strength, toughness, and shape for better mixture stability. Well graded aggregate

make better interlock (setting) between stones to provide satisfactory performance.

All sizes from course to fine should be contained in the asphalt concrete mixture.

A ¾ inch maximum aggregate size provides higher stability and improved skid

resistance.

(Fig 10.1.1) Aggregate samples

Aggregate properties of concern are generally found in nature and can be divided up

into three major categories:

Gradation and the sizes: Particle size distribution.

Consensus needs; Properties associated with physical shape and

contamination measurements that can at least partially be controlled during

production.

Source of Properties: Properties inherent in the rock source.

10.2 Aggregate properties

Aggregate are to: resist abrasion, surface texture-friction and be interlocking mass

to bear and transmit wheel loads, to provide a non skid surface. Following is

summery of the properties of aggregate in the use for AC.

Uniformity; Must be of the one grading and shape. Shape; Should be

angular in shape and have several crushed faces. Grading; Must be as

single sized as possible. Cleanliness; Should be free of dust and as clean


as possible. Durability; Should resist to abrasion, impact, polishing,

weathering etc. Adhesion; Aggregate and the asphalt have chemical

affinity to create bonding.

Aggregates should be tested to ensure that they comply with specification.

The Los Angeles (L.A.) abrasion test is a common test method used to indicate

aggregate toughness and abrasion characteristics. Aggregate abrasion

characteristics are important because the constituent aggregate in HMA must resist

crushing, degradation and disintegration in order to produce a high quality HMA.

Typical quantum contents of aggregate in AC

By Weight %: Coarse aggregate 62, Fine aggregate 28, Filler 5, (Bitumen 4.5 ~ 5.2)

By Volume %: Coarse aggregate 55,Fine aggregate 25, Filler 5,

Air Voids 3 ~ 7

Chapter 11. BITUMEN BINDER MODIFICATION

11.1 Needs of Modification

Some bitumen as a binder require modification in order to meet specifications. There

are numerous binder additives available on the market today. The benefits of

modified bitumen binder in general should be modified to achieve the following types

of improvements.


Lower stiffness (or viscosity) at the high temperatures associated with

construction. This facilitates pumping of the liquid asphalt binder as well as

mixing and compaction of HMA.

Higher stiffness at high service temperatures. This will reduce rutting and

shoving.

Lower stiffness and faster relaxation properties at low service temperatures. This

will reduce thermal cracking.

Increased adhesion between the asphalt binder and the aggregate in the

presence of moisture. This will reduce the likelihood of stripping. of an anti-

stripping modifier, which results in good aggregate-asphalt binder adhesion.

11.2 What is Asphalt Rubber.

Reclaimed tire rubber (from waste tires) recycled and is used as a modifier (CRM)

which is added to bitumen to enhance its properties. The product is a rubberised

bitumen but called Asphalt rubber.

Reclaimed tire rubber (crumb rubber) 15% by weight and certain additives are

blended into the bitumen binder. They are heated at elevated temperatures (≥ 350°F,

177°C) and allowed to react together sufficiently. Some petroleum distillates or

extender oil may be added to reduce viscosity, facilitate spray applications, and

promote workability. The resulting product has a higher viscosity over a wider range

of temperature compared to conventional asphalt

11.3 Use of Asphalt Rubber

Asphalt rubber is used as a binder in various types of asphalt pavement construction

(HMA). It is also used in crack sealants. For hot mixes, asphalt rubber has been

found to be most effective and is most commonly used in gap-graded and open-

graded mixes, particularly for surface courses and for thin overlays. It may be used

in new construction or to rehabilitate an existing pavement.

Use of asphalt rubber in hot mixes is typically suitable for gap and opens gradations

because they are most effective with respect to performance and cost. Gap and


http://pavementinteractive.org/index.php?title=Stripping

open-graded RAC mixes are most often used as overlays in rehabilitation of existing

asphalt pavements. RAC is also used as surface courses for new pavement

construction, specially to reduce traffic noise.

How ever RAC during paving has to be in worm condition for it workability. This is

not much practical as temperature also affects placement and compaction. Asphalt

rubber paving materials should not be placed in the following conditions:

During cold or rainy weather with ambient or surface temperatures <55°F

(13°C).

Over pavements with severe cracks more than 0.5 inch (12.5 mm) wide.

Where traffic and deflection data are not available.

11.4 Benefits of Asphalt Rubber

The primary reason for using asphalt rubber is that it provides significantly improved

engineering properties over conventional paving grade asphalt. RAC binders can be

engineered to perform at ambient climate or weather conditions.

The rubber stiffens the binder and increases elasticity (proportion of deformation that

is recoverable) over these pavement operating temperature ranges, which


decreases pavement temperature susceptibility and improves resistance to

permanent deformation (rutting) and fatigue with little effect on cold temperature

properties. Following are the benefits of asphalt rubber paving materials:(State of

California Department of Transportation)

Have higher viscosity that allows better film thickness no bleeding.

Perform elasticity and resilience at high temperatures.

RAC pavements stand for better durability, resistance to fatigue/reflection

cracking due to higher binder contents and elasticity.

Reduce temperature susceptibility.

Higher binder contents, thicker binder films, and anti-oxidants in the tire

rubber improve resistance to aging and oxidation.

Higher viscosity, softening points and resilience improve resistance to rutting

(permanent deformation)

Lower pavement maintenance costs due to durability and performance.

Reduced construction times due to thinner lifts.

Better chip retention in chip seals due to thick films of highly modified asphalt.

Safety due to better long-term color contrast for pavement markings.

(Fig 11.4.1 dot.ca.gov,2006) Finished RAC-G Pavement

11.5 Disadvantages

Rubber modified asphalt is done at worm conditions. The crumb rubber and asphalt

are of deferent phases, because of the weak interaction between the rubber particle

surface and the asphalt. It may sometimes result a non-homogeneous blend. This

non-homogeneity reduces the reliability of the product properties decreasing the

expected life of the rubber modified asphalt.


Chapter 12. THERMAL EFFECTS

12.1 Thermal Distresses

The temperature profile in asphaltic pavement is affected directly by the thermal

environmental conditions to which it is exposed. The fluctuation in temperatures

significantly affects pavement stability. Therefore selection of asphalt grading to be

used for pavements must be concerned to insure that the proper asphalt binder is


used to resist pavement rutting in hot temperatures and to resist cracking in cold

temperatures. Daily and seasonal ambient temperature fluctuations and solar

radiation significantly affects the pavement stability and therefore the durability. High

temperature rutting and low temperature cracking are the results mostly at cold

weather.

There may be variations of temperature at different depths and horizontal locations

based on ambient air temperatures. The top pavement layer normally is exposed to

greater temperature fluctuations than the layers below it. This temperature

distribution in asphalts may also be an issue to allow sophisticated specification for

lower layers of less expensive binder and thus cost effective as well.

12.2 Energy balance on Asphalt Pavement Surface.

The primary modes of heat transfer are incident solar radiation, thermal and long-

wave radiation between the pavement surface and the open air. Heat transfer

between the pavement surface and the air contacts with the pavement surface is

shown in figure.


(Fig 12.2.1- wpi.edu) Energy Balance in Asphaltic Pavements

The intensity of solar radiation is dependent on the sun’s rays, its incident angle

between the surface. The solar radiation contacts directly and pavement happens to

absorb the heat. The heat convection functions with the wind velocity over the

surface. High wind velocities a convective cooling of the surface occurs when the

temperature of the wind is lower than the temperature of the pavement surface.

Chapter 13. BEHAVIOUR OF THE ASPHALT CONCRETE PAVEMENT

The very purpose of the pavement is traffic run it while to stand for their wheels

loads. And it is to exist within the varying nature conditions as well, the climatic and


weather. Pavement responding all those stresses may behave positively if it can, but

adversely other vice resulting failures.

13.1 Factors influencing Pavement behaviours

The exact behaviour of flexible pavements under wheel load is very difficult to dealt

with. Due to varying effects by dynamical or statically or environmental conditions

pavement meets crucial but critical stresses. And the strains against them too

become critical causing destructive displacements unless pavement’s behaviour or

the response are not compatible or capable. The main but the excellent property

“flexibility” due to “viscoplastoelastic” property in the binder of the asphalt concrete

pavement can tolerate those effects and stresses to a greater extent. Behaviour

against those stresses by AC pavement after it is allowed to serve, may depend on

the following factors:

Properties of materials

Nature of vehicular wheels and loadings

Nature of environmental conditions

Nature of failure modes.

AC pavements get various failures consequently its behaviours under those

stresses. Therefore this paper focuses to identify and discuss about those failures

and how they are occurring as well. The effects of wheel loads on pavements are

prominently important for pavement design and bituminous mixture design.

Stresses > strains > response> deflection > distresses> failures ?


(Fig 13.1.1- How vertical pressure of the wheel (Fig 13.1.2) Load transfer

may transfer through a stiffer AC layer to the lower downwards through

is comparatively of less stiffer. - granular materials.

(Fig 13.1.3)Flexible plate deflection (Fig 13.1.4) Pavement strains under wheel

load causing stress then deflection

(13.1.5) Strains and response by the layers Wheel load pressure distribution


(13.1.6- bts.gov, 2010) Stability of the pavement layers

(13.1.7- bts.gov, 2010) Schematic view of asphalt pavement deflection


13.2 Pavement distress modes due to traffic

Some deterioration and wear on AC pavement occur not only by environmental

factors but mainly due to the traffic-related factors influencing by various vehicle

parameters, such as wheel loads and tyre type (single / dual / wide single), tyre size,

wheel load, inflation pressure. Those factors effect distinctive different modes of

distress.

When vehicles move the wheels exert dynamic stresses on the pavement. The

dynamic loading stresses are characterized by the speed, duration of loading and

traffic volume. The response of the pavement structure under the dynamic loading is

totally different from that under static loading.

13.3 Effects of Pavement Material

Pavement material properties also influence the stress and displacement variation

under dynamic loading. Usually, the material properties are time dependent and

temperature dependent. The faster the speed of vehicles, the stiffer the pavement

materials. Both deflections and the periods decrease with increase of the subgrade

modulus.

13.4 Effects by tire-pavement contacts

When a vehicle moves over the pavement there is a tire -pavement interface and a

tire -pavement contact pressure. This gives an interaction stress between the rolling

tire and pavement topmost surface. The imprint area at the tire -pavement interface

due to the action of vehicle axle load. Conventional structural design and analysis of

asphalt concrete pavements assumes that the vertical component of the contact

pressure is uniformly distributed over a circular imprint area. This assumption of

uniformly circular contact pressure distribution seems to be adequate for asphalt

pavement design and simplifies considerably the theoretical relationships of

pavement performance used by highway engineers. However the highest contact

pressure may be in the middle of a tire-pavement contact area.


13.5 Combined Stresses by Wheel loads and Thermal Conditions

Behaviour of flexible pavement under wheel and thermal loading conditions is

another distress mode in pavements. Failures to form cracks appear on asphalt

layers. These stresses induce forms of bottom-up fatigue cracking, reflective

cracking and top-down fatigue cracking. Combined stress intensity due to both

vehicle loads and thermal effects may produce favourable conditions for fast

distresses to the pavement. How ever restrictions to these combination stresses are

not practicable. In addition, due to thermal effects some damage modes dominate

pavement to contraction and shrinkage which are possible to enhance by wheel

loads.

Effect of Thermal Expansion Factor on Horizontal Stress under the Center of loading

(road-transport-technology.org,2001)


(Fig 13.5.1 - nrc-cnrc.gc.ca) Pavement happens to wear by the wheels of heavy

vehicles.


Chapter 14. PAVEMENT DISTRESSES AND FAILURES.

14.1 Fact of Distresses

Pavement has to undergo various stresses exerted by the wheel loads of traffic

running. It is well obvious that the pavement is designed and constructed to stand for

these loads consequently bear the stresses.

But the factual issue is that the varying conditions of those stresses, same of the

pavement behaviours, and also environmental changes happen to play together or

vis a vis, or simultaneously. The stresses under these situations do effect the

pavement to have particular distresses, subsequently failures, consequently certain

damages. And pavement then may render structural or functional failures

simultaneously or collectively. As an example rutting is a common failure happening

all those.

(14.1.1) Example: Depressed , water collected, weakened and vice versa.


14.1 Identifying the Pavement Distresses and Failures

Pavement serving thus, becoming older, is the more of those happenings as read

above. Therefore regular maintenance and rehabilitation on pavement become

essential to arrest those failures, rather unlike other civil engineering constructions.

Hence identifying and understanding of pavement distresses, failures and causes,

are very important. As those are of very descriptive nature, They are happened to

conveniently summarised below.


14.2 Asphalt Pavement Distresses Summary

TYPE OF DISTRESS POSSIBLE CAUSE

Fatigue Failure

1. Unbearable loading.

2. Subgarde and base courses

are poor condition.

3. Thickness of base courses

less.

4. Drainage system not

functioning.

Formation of Cracking block wise.

1. Aged asphalt concrete.

2. More fine materials had

been added to the mixture.

3. Had paved dry mixture.

4. Poor quality of bitumen

binder.

Formation of cracks along the edge 1. Uneven of settlement of

embankment.

2. Soil shrinkage.

3. Drainage functions are

poor.

4. Lateral support failure.

5. Effects by vegetation along

the edge.



Crack formation transfers wise 1. Thermal differences.

2. Poor quality of underlying

layers.

3. Poor constructions

methods.

4. Uneven paver operation.

Reflection Cracking formation 1. Uneven settlement and

the movement of

underneath layers.

2. Traffic operation

movements.

Cracks formed by slippages. 1. Poor bonding of the

material.

2. Higher sand content

3. Braking effects by heavy

traffic.

4. Vehicular turning or

stopping movements.



Formation of Corrugations 1. Low air voids content.

2. Higher usage of fine

aggregate.

3. Aggregates of poor granular

4. Aggregate used are rounded.

5. Poor quality of the binder

Formation of Rutting 1. Improper compaction.

2. Poor quality of the asphalt

concrete.

3. The layer thickness not

sufficient.

4. Moisture affects due to

weakness of the material.

Formation of Depressions

1. Poor compaction.

2. Uneven settlements of the

underneath layers.

3. Moisture attacks weaken the

underneath material strengths.



Formations of Swells

1. Usage of clay material which

swells due to moisture.

2. Frost heave.

3. Lateral Pressure applied by

traffic.

Depression at utility service trenching.

1. Improper compaction.

2. Unequal usage of material.

3. Failures of the adjoining

layers.

Formation of Pot Hole

1. Poor drainage system.

2. Deterioration of the surface

material.

3. All the courses related to

above distresses.

4. Lack of maintenance.


Formation of Weathering


1. Usage of poor quality asphalt

concrete.

2. Combination of vehicle loads

and moisture.

3. Aging the asphalt binder.

Formation of Bleeding

1. Bitumen binder used

excessively.

2. Tack coat application at higher

rate.

3. Heat affects.

4. Content of fine materials

higher in the asphalt concrete.

5. Less content of air voids

Smooth surface

1. Usage of poor quality

aggregate.

2. Higher traffic movements.



Segregation of surface materials. 1. Poor quality of aggregate

2. Seal coat used cooled

condition.

3. Aggregate embedded poor.

4. Usage of dusty aggregate.

5. Traffic had been allowed before

curing.

Formation of transfer’s weaker lines on the surface.

1. Sealed coat spraying unequally.

2. Spreading blinding aggregate

done after cooling the seal coat.

3. Application of high viscosity

bitumen when spraying.

Pavement becoming older (aging) is the more of these happenings to develop.

Therefore regular maintenance and rehabilitation on pavement become essential to

arrest those failures.

Chapter 15. ASPHALT CONCRETE PAVEMENT RECYCLING


15.1 Demand for Recycling

AC is a versatile material which contains durable and longer lasting ingredients

(aggregates and binder). It can be easily recycled and reused. Pavements after their

life times need rehabilitation or expansions thereby subjected to demolishing and

removal. The debris or the removed materials thus is /can be recycled for reuse.

Aged AC pavements can be effectively recycled by recycling processes. The end

product materials (mainly aggregate) may be of the same quality (strength) and

performance level as they were before. By effectively recycle process the old AC

pavement can be brought (rehabilitate) to a new pavement which can perform

original state.

Demand for recycling is increasing due to rising costs for materials and some

scarcity of quality aggregates near the locations / sites. At these situations on

economical and environmental needs recycling become prominently important.

According to Highway Agencies, nearly 35 percent of asphalt concrete pavement is

recycled into HMA with a substantial cost savings over virgin HMA mixes achieving

almost similar performance characteristics.

15.2 Recycling Process


It is a process of excavation (demolishing and removing), milling and repaving

process by roadway milling machine or “roadmiller”. A typical road milling operation

is shown in the figure below.

(Fig. 15.2.1) Recycling Operations of a Asphalt concrete pavement

The steps include:

Excavating the old AC-pavement material,

Milling it to particle size of 20 – 10 mm. approximately (referred as reclaimed

asphalt pavement “RAP” ),

Conveying RAP to asphalt plant, reusing to produce (commonly by HMA

production process) a new AC mixture. and finally

Paving to form the pavement.

15.3 Recycling Methods

Asphalt Recycling and Reclaiming Associations recommends recycling methods as

defined by:

Cold planing,

Hot recycling,

Hot in-place recycling,

Cold in-place recycling

15.4 Use of Recycled materials for Asphalt Concrete


HMA is produced in a plant through usual process within which predetermined

quantity of RAP is added typically 25 to 35 percent by weight. Professionals do

recommend even higher additions are feasible. The new product can perform same

as HMA unadded with RAP. How ever there are some precautions when using RAP:

RAP at heating may produce emissions in the form of gaseous hydrocarbons.

It is minimized by adding RAP into pre-heated new aggregates thus making

RAP heats up through contacts with the heated aggregates.

RAP addition may require additional heating in the plant process.

RAP generally contains 3 to 7 percent asphalt binder by weight and may be of

higher viscosity (stiffer) due to aging. Therefore a lesser viscous (softer)

binder should be used.

It is to note RAP gradation is generally finer than pure virgin aggregate because of

the degradation that occurs during removal and milling at the recycling process.

15.5 Benefits of Recycling


Recycling of RAP has both environmental and economical benefits. RAP saves

natural resources. In comparison to the use of virgin material, a cost saving of nearly

30% can be achieved by RAP through which same materials can be used.

Following figure shows the Life Cycle of Asphalt Concrete Pavement. It reads some

thing to understand how beneficial is the recycling.

(15.5.1) Life Cycle of Sustainable asphalt concrete pavement

(www.lrrb.org,2011)

Chapter 16. SUSTAINABILTY


16.1 What is Sustainability

The basis of sustainability commonly consists of three elements: economy, society,

and environment. It is well said ” Meeting the needs of the present without

compromising the ability of future generation to meet their needs”

Sustainable pavement is a subset of sustainable transportation with the main

emphasis in pavement design and management, material use and recycling. In

order to achieve sustainable pavement, it is necessary to integrate economic, social,

and environmental considerations into practice.

16.2 Need of sustainable pavement

Road / pavement infrastructures get aging and deteriorate over times. With limited

resources and funding, transportation agencies face challenges but have to continue

in maintaining or building pavement infrastructures to meet the needs of the users.

These issues together with the concept of sustainable development are compelling

the pavements not only be sustainable but to use sustainable materials as well.

16.3 Pavement Sustainability


Pavement has a vital roll in the sustainable transportation. It is the prominent

component within sustainable transportation system considering a broad spectrum of

engineering activities. It can be illustrated by below figures:

16.4 Components of Sustainable Pavement

Sustainable pavement concept has driven many research motivations. These

motivations are in the form of sustainable paving material utilization, innovative

design and construction methods. One of the goals behind these research

motivations is maximizing pavement performance using the given funding and

resources available.

(Fig 16.4.1) Components of Sustainable Pavement and Transportation

The pavement ages and deteriorates over times. Proper construction and

maintenance techniques are essential to ensure roads to provide the required

performance for road users. As resources and funding are becoming limited yet

important it is compelling the transportation agencies to utilize the resources with

maximum benefits. This requires recycling of existing aged pavements of which

materials can be reused to construction new pavement while saving economical and

environmental aspects.

16.5 Basics of sustainable pavement in recycling technology


From aged pavements:

Reclaiming Asphalt Pavement (RAP)

In-Place Recycling ( Milling and Plant operations)

Factory Recycling ( Milling, Transporting, Plant operation)

Hot-Mix Asphalt / Warm-Mix Asphalt

Sustainable Pavement

From wastes:

Reuse Application

Fly ash / Coal ash

Tire Rubber ( Crumb Rubber from waste tires)

Shingles

Slag

Foundry sand

Plant Operations

Hot-Mix Asphalt / Warm-Mix Asphalt

Sustainable Pavement

CONCLUSION


Pavements have to undergo the various stresses exerted not only by the traffic loads

but also by environmental conditions of weather and climatic. All of them are at

varying status often, liable to varying distresses on and into the pavement. Traffic

loads and environmental effects when happen simultaneously pavement structure

happens to bear complicate stresses and its behaviours become serious. The

resultant would be distresses mostly leading towards failures.

It is a fact to observe pavements get deteriorated and regular damages when they

are at the use. Respective authorities or agencies take efforts to restrict the causes.

Professionals of the subjects have developed various techniques in this regard as

well. More researches have been done, particularly towards the asphalt concrete for

pavement construction.

Quality, particularly the density of asphalt concrete pavement is to concern highly.

Bitumen content, air void content and density are the vitally important. These are to

be so desirable, because those are the main factors governing the behaviour of

asphalt concrete pavement. However they are depended according to the types and

purposes of the pavement layers. As an example for “dens graded asphalt

pavement” the allowable volume percentages found to be 4 ~ 5 %, 3 ~4 % and

97~98 % respectively.

The results of density test done proved to be compatible as the proper quality control

system had been applied there. However these factors achieved at the construction

(just before) may be changed due to all the reasons explained above, especially

when pavement is at the use. Therefore further investigations and studies are

needed to carry out why and how they vary leading to failures as said above. Time

verses traffics would be the appropriate and find any possible improvements to

control or restrict the causes.

Bibliography


Alaska University Transportation Center. (2010, 12 30). Retrieved from Airport Manager's Guide for the Maintenance of Asphalt Pavements of General Aviation Air ports: http://www.dot.ca.gov/hq/planning/aeronaut/document/CALTRANS_Final_Report_1.12.09.

Arthur Wingnall, P. S. (1991). Road Work Theroy and Practice. Third Edition. Published in association with the Institution of Works adn Highways Management.

Asphalt Additives Symposium. (2011, 01 03). Retrieved from Innovative Asphalt Emulsion ApplicationsEmulsion Applications: http://www.petersenasphaltconference.org/download/2004/32King.

black tides. (2011, 03 01). Retrieved from Products obtain fron crude oil refinery: http://www.black-tides.com/uk/oil/oil-everyday-lives/products-obtained-from-crude-oil.php

Breach, M. (2009). Dssertation Writting for Engineers and Scientists. Student Edition. Nottingham Trent University: Pearson Education.

CHEMISTRY AND ISSUES IN THE ENVIRONMENT. (2011, 03 14). Retrieved from Fractional Distillation of Crude Oil: http://www.elmhurst.edu/~chm/onlcourse/chm110/outlines/distill.html

Construction Division. (2011, 03 01). Retrieved from Super Heavy Load Analysis Background: http://onlinemanuals.txdot.gov/txdotmanuals/pdm/super_heavy_load_analysis_background.htm

Cornell Local Roads Program-NEW YORK LTAP CENTER. (2011, 03 10). Retrieved from Asphalt Paving Principles: http://www.clrp.cornell.edu/workshops/pdf/asphalt_paving_principles-web

Engine Mechanics. (2011, 02 16). Retrieved from Stage of Constrauction: http://www.tpub.com/content/engine/14081/css/14081_465.htm

FAO-Foresty Department. (2010, 12 15). Retrieved from ROAD CONSTRUCTION TECHNIQUES: http://www.fao.org/docrep/006/t0099e/T0099e06.htm

Fernando, H. (2001). Road Contraction Techniques and Failures. Second edition. University of Peradeniya-Civil Engineering Department: G.M Publishres.

Group, O. R. (October 1978). Maintenance techniques for Road Surfacing. Organisation for Economic co-operation and development.

Institute of Transportation Studies-California. (2011, 02 13). Retrieved from Summary Report on permanent deformation in asphalt concrete: http://onlinepubs.trb.org/onlinepubs/shrp/SHRP-A-318.)

Maintenace technical Advisory Guide. (2010, 12 11). Retrieved from Common Distresses on flexible pavements: http://www.dot.ca.gov/hq/maint/MTAG-CommonFlexiblePavementDistresses.

NKY group. (2011, 03 15). Retrieved from Petroleum Products: http://www.nyk.com/english/seascope/200604/index.htm

Nottinhgam Center for Pavement Engineering-University of Nottingham. (2010, 12 17). Retrieved from Pavement Design: http://www.nottingham.ac.uk/~evzncpe/docs/introduction.


NRC. (2011, 03 14). Retrieved from Effects of tire - pavement contact pressure distributions on the: http://www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/nrcc38864.pdf

Pavement interactives. (n.d.).

Pavement interactives. (2010, 11 24). Retrieved from HMA Pavement: http://pavementinteractive.org/index.php?title=Base

Pavement tool consortium. (18, 11 2010). Retrieved from PTC Pavement Guide: http://training.ce.washington.edu/PGI/

Quarry Products Association. (2011, 01 02). Retrieved from Asphalt - road materials with quality: http://www.mineralproducts.org/documents/asp-quality-road_materials.pdf

Rogers, M. (2003). Highway Engineering. oxford-blackwell science.

Salter, R. (1998). Highway Design and Constration.Second Edition. University of Bradfor: Macmillan.

Scott Wilson Pavement Engineering Ltd. (2011, 02 07). Retrieved from ASPHALT CRACKING UNDER ULTRA-SLOW STRAIN: http://www.eecongress.org/2000/pdfbook3/session2/Proc0115uk

Smith, J. P. (1995). Petroleum Refining. First Edition.

State of California Department of Transportation. (2011, 03 25). Retrieved from ASPHALT RUBBER USAGE GUIDE: http://www.asphaltrubber.org/ari/California_AR_Design_Guide/Caltrans_Asphalt_Rubber_Usage_Guide

TAMS. (2011, 02 13). Retrieved from Flexible pavement construction: http://www.tams.act.gov.au/pv_obj_cache/pv_obj_id_5CC17A2F8A0A2E629E71DF5A7CC860326F590500/filename/SS04_Flexible_Pavement_01_00.pdf

the constructor civil engineer home. (2011, 01 03). Retrieved from FLEXIBLE PAVEMENT COMPOSITION AND STRUCTURE: http://theconstructor.org/transportation/flexible-pavement-composition-and-structure/5499/

training CE washinton. (2010, 12 01). Retrieved from Flexible Pavement: http://training.ce.washington.edu/wsdot/Modules/07_construction/07-6_body.htm

Transport Road and Traffic Authority. (2010, 11 22). Retrieved from Typical Road Pavement Section: http://www.rta.nsw.gov.au/doingbusinesswithus/designdocuments/cross_sections.html

Transportation Systems Engineering. (2011, 04 11). Retrieved from Introduction to pavement design: http://www.civil.iitb.ac.in/tvm/1100_LnTse/105_lntse/plain/plain.html

Transportation, U. D. (May 2006). Geotechnical Aspects of Pavement. National Highway Institute.

troxler. (25, 11 2010). Retrieved from vertual superpave laboratory: http://training.ce.washington.edu/VSL/index.htm


Watson, J. (1989). Highway Construction and Maintence. Longman Scientific & Technical.

wise geek. (2011, 03 01). Retrieved from What are Different Types of Asphalt?: http://www.wisegeek.com/what-are-different-types-of-asphalt.htm


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