Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94

8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94

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Roads BranchPublic Works Department Malaysia

Jalan Sultan Salahuddin50582 Kuala Lumpur

JKR 20709-0315-94

Interim Guide To

Evaluation And Rehabilition

Of Flexible Road

Pavements

5.0m0m

7.0m0m


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Interim Guide To Evaluation AndRehabilitation Of Flexible Road pavements.

Cawangan Jalan, Ibu Pejabat JKR, K.L

IKRAM can accept no responsibility for mis-appropriate use of this manual. Engineering

judgement and experience must be used to

properly utilise the principles and guidelines

outlined in this manual taking into account

available equipment, local materials and condi-

tion.

Photographs and drawings of equipment in this

publication are for illustration only and do not

imply preferential endorsement of any particu-

lar make by IKRAM.

PREFACE

This guide is written primarily as an interim

guideline for practising road engineers and

those who are involved in road maintenance

activities. An attempt has been made to draw

together all the information required in the

evaluation and rehabilitation of flexible road

pavements within one volume.

It is hoped that the background information

given, together with the review of current

research work carried out at IKRAM, particu-

larly in relation to the pavement behaviour and

performance under Malaysian climatic condi-tions will make it of interest to those engaged

in the research aspects of road engineering and

in teaching the subject.

Some of the practical experiences on which the

guide is based have been gained under

Malaysian climatic conditions. However, due

to limitations, some references were drawn

from various overseas agencies in particular the

Transport and Research Laboratory (TRL),

U.K.

Although it is the intention of the authors to

make this guide as comprehensive as possible,

it has not always been possible to do so as the

performance of flexible road pavements in

Malaysian environment is not yet fully under-

stood. However, to facilitate the early under-

standing of the present practices, this interim

guide has been produced. The authors are

FOR INTERNAL USE ONLY

INTERIM GUIDE TO EVALUATION

AND REHABILITATION OF FLEXIBLE

ROAD PAVEMENT


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aware of the necessary work still needed to

complete this guide and are, at present, under-

taking research to make this possible.

The chapters have been written so that they can

be read and understood largely independent ofeach another, but where necessary cross-refer-

encing to specific paragraphs should make the

reader's task easier.

This guide aims to be factual but some expres-

sion of opinion is inevitable where gaps in

knowledge exist.

ACKNOWLEDGEMENTS

This guide is prepared by the PavementResearch Unit

Head: Ir. Mohamed Shafii Mustafa

lnstitut Kerja Raya Malaysia (IKRAM).

The authors of this guide are :

- Mohd. Sabri Hasim

- Abd. Mutalif Abd. Hameed

- Ir. Koid Teng Hye

- Ahmad Fauzi Abdul Malek- Ir. Mohamed Shafii Mustafa.

This document forms part of a series of guide-

lines on the design, construction and mainte-

nance of flexible road pavements which the

Pavement Research Unit is producing as part of

their studies.

This guide was reviewed by a Committee

headed by the Director of IKRAM :

Ir Ng Chong Yuen. Other members of the

Committee were :

- Ir Han Joke Kwang (IKRAM)

- Ir. Aik Siaw Kong

- Ir. Tai Men Choi

- Ir. Zainol Rashid Zainuddin

Of Roads Branch (JKR Headquarters) and

Ir Abdul Shokri Mohd. Dalian (JKR Selangor).

The authors would like to express their heart-

felt thanks to the Director General of Public

Works Malaysia for his permission to publish

this guide. Thanks are also due to Tan Kee

Hock and Mooi Jiann Liang for their assistance

in preparing this guide. Finally, special thanks

are due to C. R. Jones of the Overseas Centre,Transport Research Laboratory, U.K. for his

advice on specific topics of the guide.

CHAPTER 1 : INTRODUCTION

1.1. BACKGROUND

1.1.1 Brief history of Malaysian road

pavements 1.1

1.1.2 The need for engineeringevaluation of the road

pavement 1.1

1.1.3 Economic analysis as a part of the

engineering decision

making process 1.2

1.2 SCOPE OF THE GUIDE 1.3

1.2.1 Limitation of the Guide 1.4

1.3 OBJECTIVES 1.4

CHAPTER 2 : PAVEMENT BEHAV-

IOUR AND PERFORMANCE

2.1 PAVEMENT COMPONENTS AND

MATERIALS

2.1.1 Surfacing 2.1

2.1.2 Road-base 2.1

2.1.3 Sub-base 2.1

2.1.4 Subgrade 2.2

2.2 FUNCTIONS OF FLEXIBLE

PAVEMENT 2.2

2.2.1 Road users requirements 2.2

2.2.2 Engineering requirements 2.2



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Interim Guide To Evaluation And

Rehabilitation Of Flexible Road Pavements.


2.3 FAILURE DEFINATIONS 2.3

2.3.1 Failure modes 2.3

2.3.2 Failure manifestation 2.3

2.3.3 Failure mechanisms 2.3

2.4 PAVEMENT BEHAVIOUR 2.3

2.4.1 Behaviour of thin surfacing 2.5

2.4.2 Behaviour of component lavers in a

typical flexible pavement 2.5

2.5 PAVEMENT PERFORMANCE 2.9

2.5.1 Terminal condition 2.9

2.5.2 Users requirements 2.9

2.5.3 Engineers and managers

requirements 2.9

2.5.4 Empirical interpretation

of performance 2.12

2.5.5 Mechanistic interpretationof performance 2.12

2.5.6 Future undertakings 2.15

2.6 REFERENCES 2.15

CHAPTER 3 : PAVEMENTEVALUATION

3.1 GENERAL 3.1

3.1.1 Project initiation 3.1

3.1.2 Physical condition assessment 3.1

3.1.3 Non-destructive testing (NDT)3.1

3.1.4 Analysis and rehabilitation

design 3.3

3.1.5 Selection of remedial

measures 3.3

3.1.6 Cost analysis 3.3

3.1.7 Implementation 3.3

3.2 INITIALASSESSMENT 3.3

3.2.1 Surface condition assessment 3.4

3.2.2 Drainage assessment 3.4

3.2.3 Prelirninarv analysis,

sectioning 3.7

3.3 DETAILASSESSMENT 3.8

3.3.1 General 3.8

3.3.2 Choice of NDT devices 3.9

3.3.3 Choices of NDT analysis

techniques 3.14

3.3.4 Test interval, variability and

accuracy level for structural

assessment 3.24

3.3.5 Surface evaluation 3.25

3.3.6 Other key factors to consider

during evaluation 3.26

3.3.7 Detail material investigation 3.29

3.4 REFERENCES 3.31

CHAPTER 4 : TRAFFIC LOADINGASSESSMENT

4.1 GENERAL 4.1

4.2 TRAFFIC CATEGORIES 4.1

4.2.1 Normal traffic 4.1

4.2.2 Generated traffic 4.2

4.2.3 Diverted traffic 4.2

4.2.4 Special traffic 4.2



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4.3 TRAFFIC AND AXLE LOAD

SURVEYS 4.2

4.3.1 Specific survey method 4.2

4.4 FORECASTING FUTURETRAFFIC 4.4

4.4.1 Base data 4.4

4.4.2 Methods of predicting

growth and compounding 4.4

4.4.3 Estimating damaging effect 4.4

4.4.4 Sensitivity and accuracy 4.4

4.5 EXAMPLES 4.6

4.6 REFERENCES 4.10

CHAPTER 5 : METHODS OF

REHABILITATION

5.1 SELECTION PROCEDURE 5.1

5.2 REHABILITATION OPTIONS 5.1

5.3 RESTORATION 5.4

5.3.1 Rejunevating 5.5

5.3.2 Crack Sealing 5.6

5.3.3 Cutting and Patching 5.7

5.3.4 Thin asphalt overlay 5.11

5.3.5 Surface recycling 5.15

5.4 RESURFACING 5.17

5.5 RECONSTRUCTION 5.20

LIST OF FIGURESFigure 1.1 Elements in pavement

evaluation 1.2

Figure 1.2 Decision making levels in road

pavement maintenance 1.3

Figure 1.3 Cross-section of a typical

flexible 1.4

Figure 2.1 Typical serviceability require-

ments for different class of road

(AASHO Road Test) 2.2

Figure 2.2 Stresses and strains in a bitumi-

nous pavement (Asphalt

Institute) 2.4

Figure 2.3 A typical rate of binder

hardening in service 2.7

Figure 2.4 Hardening of binder in the top

3mm of the road surfacing 2.7

Figure 2.5 Typical strain-life relationship

for bituminous unixes 2.10

Figure 2.6 Typical strain-life relationship

for subgrade (SHELL) 2.10

Figure 3.1 Flow chart of pavement

evaluation process 3.2

Figure 3.2 Schematics of Benkelman

Beam 3.11

Figure 3.3 Schematics of the Dynamic

Cone Penetrometer 3.11

Figure 3.4 Schematics of the Road

Rater 3.15

Figure 3.5 Schematics of the Falling

Weight Deflectometer

arrangements 3.16

Figure 3.6 Reduction in deflection after

overlay 3.19

Figure 3.7 Distribution of cracking

and rutting 3.19

Figure 3.8 Deflection bowl and

materials characterisation 3.20

Figure 3.9 DCP test results 3.23



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Figure 3.10. Typical plot of the DCP

results 3.23

Figure 3.11. Micro and macro-lextUre 3.25

Figure 5.1 General Process for SelectingAppropriate Rehabilitation

Alternatives 5.2

Figure 5.2 The Spectrum of Pavement

Rehabilitation Alternatives 5.3

Figure 5.3 Replacement of Loss

Chemical Constituents by

Rejuvenation 5.5

Figure 5.4 Proper methods of cuttingand patching 5.9

Figure 5.5 Surfacing Recycling Using

Hot Milling Method 5.16

Figure 5.6 Methods of Reducing

Reflection Cracks Using

Interlayers 5.18

Figure 5.7 Full Reconstruction

Options 5.23

LIST OF TABLES

Table 2.1 Failure modes, manifestations

and mechanisms 2.4

Table 2.2 Examples of formula and

coefficients for strain-life

relationship 2.11

Table 3.1 Surface condition survey

form. 3.5

Table 3.2 Classification of cracks 3.6

Table 3.3 Material condition

intrepetation 3.20

Table 3.4 Estimated values of structural

coefficients for various conditions

of asphalt. 3.22

Table 3.5 Estimates of structural

coefficients, based on DCP

in-situ CBR values. 3.22

Table 4.1 Typical HPU traffic survey

results 4.3

Table 4.2 Axle load survey results for

direction 1, Southbound. 4.6

Table 4.3 Axle load survey results for

direction 2, Northbound. 4.6

Table 4.4 Traffic count results for

direction 1, Southbound. 4.7

Table 4.5 Distribution of yearlydamaging effect 4.8

Table 4.6 Summary of traffic counts

results obtained from HPU.4.9

LIST OF PLATES

Plate 3.1 Rut depth measurement 3.6

Plate 3.2 Surface condition survey 3.7

Plate 3.3 The Road Rater 3.12

Plate 3.4 The Falling Weight

Deflectometer 3.13

Plate 3.5 The Heavy Weight

Deflectometer 3.15

Plate 3.6 Pendulum Skid Resistance

Tester 3.26

Plate 3.7 The Griptester 3.27

Plate 3.8 Sand Patch test 3.27

Plate 3.9 TRRL Minitexture meter 3.28

Plate 3.10 The Friction Tester 3.28

Plate 4.1 Axle load weighing 4.3



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Plate 5.1 Rejuvenating aged Asphalt

Surfacings in Progress 5.7

Plate 5.2 Crack Sealing 5.8

Plate 5.3 Cutting and Patching 5.10

Plate 5.4 Cold Milling 5.11

Plate 5.5 Surface Dressing 5.13

Plate 5.6 Slurry Seal 5.13

Plate 5.7 Application of Geosynthetic

Materials 5.19

Plate 5.8 Reconstruction Works 5.21

Plate 5.9 Recycling for Base 5.21

CHAPTER l :INTRODUCTION

1.1 BACKGROUND

1.1.1 Brief history of Malaysian road pave-

ments.

Bituminous pavements were first constructed in

Malaysia some time before the Second World

War. In those years, the road pavements were

constructed using block stone pitching on sand

or laterite sub-bases covered with a layer of tar

or bitumen stabilized aggregates. Since the war,

road pavements have been constructed using

crushed stones road bases and sand sub-bases

with dense bituminous surfacings. This con-

struction method is still being practiced today.

To ensure the smooth operation of the road net-

work, the road pavements have been constantly

maintained and upgraded. Invariably, the road

networks along the main trade routes were

given more attention than the others. As such

the road pavements along these routes are

thicker than those along the minor roads. Even

though the roads were regularly maintained and

upgraded, there were, generally, a lack of

record keeping, on the conditions of the roads

and the type of maintenance carried out. Most

of the upgrading works carried out were either

not designed or designed using methodologies

imported from the various western countries.

An engineering-based road management sys-

tem was only introduced in Malaysia in 1974

when a Benkelman Beam survey of 2291 kmof Federal and State roads was carried out by_

KAMPSAX International.

1.1.2 The need for engineering evalu-ation of the road pavements.

In order to ensure that the road network is able

to satisfy the ever increasing demand placed on

it due to increased traffic, there is a need for a

systematic approach to the maintenance of the

road network. The lack of proper engineeringrecords on past construction and maintenance

works now . necessitates the need for full

engineering evaluation to be carried out before

the design of further road improvements or

rehabilitation.

By using definitive and sound engineering

decisions, appropriate solutions for pavement

maintenance problems can be found.

Comprehensive evaluation on distressed pave-

ments can fulfill this requirement. This allowsthe most appropriate method of rehabilitation to

be selected thus nninimising long term total

expenditure.

After a new pavement is constructed, both

environmental and traffic stresses will cause it

to deteriorate. The rate of deterioration will

depend on the severity of the traffic loads and

the variability of the road materials. In the eval-

uation process, the identification and classifica-

tion of the type of failure is necessary if correct

remedial treatments are to be undertaken.

Pavement engineers are faced with the difficult

task of evaluating pavements that have been

subjected to varying traffic loads under variable

environmental conditions and material proper-

ties (Figrure 1.1). Field measurements are valu-

able practical tools in the evaluation of road

performance and in the identification of the

causes of failure. The task becomes more diffi-

cult if the pavement has gone through a series



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Figure 1.1 Elements In Pavement Evaluation

Fugure 1.2 Decision Making Levels In Pavement Maintentenance


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of previous unrecorded maintenance treat-

ments.

1.1.3 Economic analysis as part of engi-

neering decision malting process.

To ensure a good return on the investment in

road construction, a cost benefit analysis is

needed to ensure that the most cost effective

method of maintenance is employed. If the

future performance of the road is not correctly

predicted, then large sums of money may be

wasted.

The details to which the engineering and eco-

nomic needs are considered are dependent on

the level at which decisions are made (Figure1-2). The considerations on economic needs are

more important at the Network Level than at

the Project Level.

In most cases, road improvement projects are

identified after due economic consideration are

taken at the network level. At all levels of deci-

sion making, a simple, systematic and work

able solution is necessary.

The introduction of the BS(M) Management

System in 1983 was an attempt by the govern-

ment to use engineering-based criteria to main-

tain and upgrade the road networks. With theintroduction of the Pavement Appraisal and

Management Suite (PAMS) in 1992, this was

extended to balance the engineering and the

economic needs of the country.

1.2 SCOPE OF THE GUIDE

This guide covers the processes needed in car-

rying out an engineering evaluation on flexible

pavements that allows a better decision to be

made at the Project Level. It incorporates briefand relevant discussions of behaviour, perform-

ance and deterioration of flexible pavements

subjected to local climatic and

traffic conditions. It subjected the evaluation

process and discusses the most appropriate

solutions in rectifying pavement deficiencies.

This guide should be used in conjunction with

other


Fugure 1.3 Cross-section Of A Typical Flexible Road Pavement


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IKRAM guidelines on road pavements

and existing JKR Standard Specifications for

Roadworks.

1.2.1.Limitations of the Guide

Even though it is the intention of the authors to

provide comprehensive and accurate informa-

tion in this guide, the users are cautioned that

the procedures and remedial measures

described in this guide are interim. On-going

research work at IKRAM in this field will be

able to add more information to the guide in

the next revision. The behaviour and perform-

ance of the pavements addressed in this guideis for flexible pavements only. A typical flexi-

ble pavement is as shown in Figure 1.3.

1.3 OBJECTIVES

The aim of this guide is to provide a procedure

for the engineering evaluation of flexible road

pavements. The objectives are :

(i) To provide a systematic method of pave-

ment evaluation.

(ii) To assist engineers in identifying primary

modes of pavement deterioration.

(iii) To assist engineers in selecting appropriate

methods of rehabilitation.

This guide is structured in a manner to provide

simple, systematic and workable solutions to

the users. It is aimed at engineers at the project

level.

CHAPTER 2

PAVEMENT BEHAVIOURAND PERFORMANCE

2.1. PAVEMENT COMPONENTS ANDMATERIALS

A flexible pavement is a layered structure con-

sisting of the sub-base, road-base and the sur-

facing overlying the natural ground or sub-

grade.

2.1.1 Surfacing

]The surfacing is the upper layer of the pave-ment which fulfils the following requirements :

a) To provide an even, non-skidding and

good riding quality surface

b) To resist wear and shearing stress imposed

by traffic

c) To prevent water from penetrating into the

underlying pavement layers

d) To be capable of surviving a large number

of repeated loading without distress

e) To withstand adverse environmental condi-tions

The form of bituminous surfacing commonly

used can either be thick or thin. Thick bitumi-

nous surfacings nornally consist of crushed

mixed aggregates. bitumen and filler. Most

common types of plant mixed surfacings in

Malaysia are asphaltic concrete or bituminous

macadam. Currently constricted thin surfacings

are surface dressings and slum seals.

Thick bituminous surfacings provide additional

strength to the pavement and seal the pavement

from water ingress. Thin surfacings do not give

direct additional strength. They merely protect

the pavement from water and provide a skid

resistant riding surface.

2.1.2 Road-base

The road-base is the main structural layer of

the pavement which spread the load from

heavy vehicles thus protecting the underlying

weaker layers. Its functions are to reduce the

compressive stress in the subgrade and the sub-

base to an acceptable level and to ensure that

the magnitude of the flexural stresses in the

surfacing will not lead to cracking. Unbound

crushed mixed aggregate has been widely used

as a road base material throughout the country.

Granite and limestone are readily available in

most areas in Malaysia and have historically

been the major sources of aggregate for road-



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bases.

2.1.3 Sub-base

The sub-base is the secondary load-spreading

layer underlying the road-base. It will nornallyconsist of lower grade granular material as

compared to that of the road-base. Sand and

lateftes are commonly used and are easily

available. This layer also serves as a separating

layer preventing contamination of the road-base by the subgrade and also acts as a prepara-

tory layer for road-base construction. It can

also act as a drainage layer.

2.1.4 Subgrade

The subgrade refers to the soil under the pave-

ment within a depth of approximately 1 meter

below the subbase. It is the upper layer of

earthworks prepared for subsequent construc-

tion of the pavement layers described above.It

can either be natural undisturbed soil or com-

pacted soil obtained from elsewhere and placed

as fill material. The strength of the subgrade

layer is important as the thicknesses of the

upper layers are dependent on it.

2.2. FUNCTIONS OF FLEXIBLEPAVEMENT

The general function of a road pavement is to

provide a safe and comfortable riding surface

for the road users. Its condition with respect to

these characteristics is normally assessed by

two groups of people, namely the users and the

road engineers.

2.2.1 Road user requirements

A safe and comfortable riding surface is what

the road users nontially require. The aestheticaspect of it is also a concern but will receive

considerable attention only on heavily traf-

ficked pavements. The life of the pavement

perceived by the users will be primarily relate

to its riding quality. Road pavements that do

not provide a safe and comfortable riding sur-

face will trigger the road users' awareness as to

the increase in vehicle operating cost.

The users requirement for a road pavement can

be quantified in ternis of serviceability index

(1). The terns serviceability was first intro-

duced during the AASHO Road Test to repre-

sent pavement performance. The road pave-

ment was given a rating in terms of riding

comfort by various drivers, with a value of 5 as

the highest index of serviceability and 0 as the

lowest. A terminal serviceability of 2.5 was

suggested as the condition when major road

rehabilitation works. For the rehabilitation of

minor roads, a terminal serviceability of 1.5

mvas suggested by AASHO (Figure 2.1).



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2.2.2 Engineering requirements

The engineer is mostly concern with whether

the road will achieve its design life. The rate of

deterioration is also a major concern. A rapid

rate of deterioration requires immediate inter-vention. The road user may not be aware of the

occurrence of early deterioration since the rid-

ing quality may still be acceptable. In contrast

the engineer must be alert to such problems as

early maintenance enhances the road perform-

ance.

It is thus necessary to understand the behaviour

and performance of road pavement under

Malaysian condition. In evaluating and rehabil-

itating a road pavement in this country, wherethe environmental factors are different from

Western nations, there are dangers in applying

those rehabilitation solutions that have been

obtained elsewhere as they may not suit condi-

tions in this country without some modifica-

tion.

Road user and engineering needs must be prop-

erly balanced to suit budget requirements and

maximise benefit through appropriate methods

of maintenance. Experience elsewhere has indi-

cated that prompt maintenance can indeed save

expensive reconstruction costs.

2.3 FAILURE DEFINITIONS

2.3.1 Failure modes

The predominant failure modes are fracture,


Mode Manifestation Comman Mechanisms

Frature CrackingExcessive loading Repeated loading

Moisture changes Age hardening

Distortion permanent DeformationExcessive loading Creep Densification

Consolidation Moisture changes

Disintegration Stripping and ravelling

Lack of adhesion Chemical aggression

Abrasion by traffic Degradation of

aggregate.

Table 2.1. Failure Modes, Manifestations And Mechanisms

Figure 2.2. Stresses And Strains In A Bituminouns Pavement


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distortion and disintegration. Fracture nornially

occurs in thick bituminous layers. Distortion

manifests itself in any of the pavement layers

and will normally appear on the bituminous

surface as netting or other forms of deforma-

tion. Disintegration will normally take place onthe bituminous surfacing. Loss of aggregates is

a common manifestation of this failure mode.

2.3.2 Failure manifestations

Each component of the pavement layers may

contribute to failures. The most difficult task is

to identify which layer is the cause of primary

failures of the road. Failure in flexible pave-

ments most commonly manifests itself as

cracking or deformation. These defects canbe visually identified and measured using

appropriate techniques.

2.3.3 Failure mechanisms

Extensive research has established the various

mechanisms that cause road failures. Some

common mechanisms are :

i) Repeated axle loading

ii) Excessive loadingiii) Thermal and moisture changes

iv) Material densification

v) Consolidation of subgrade

vi) Shear in subgrade

vii) Time dependent deformation (creep)

viii)Abrasion by traffic

ix) Chemical degradation

x) Degradation of aggregate

xi) Hardening of the bitumen

Early detection of these mechanisms during the

evaluation process can help in identifying the

probable remedy. Suitability and accuracy of

evaluation procedures and analysis are depend-

ent on accurate identification of actual modes

of failure. The relationship between failure

mode, their manifestations and probable mech-

anisms is as shown in Table 2.1.

2.4 PAVEMENT BEHAVIOUR

Before moving further into pavement evalua-

tion methodology, it is necessary for a road

engineer to understand pavement behaviour

especially under local environmental condi-

tions.

Repeated axle loading, the environment, soilcharacteristics and drainage, are some factors

that affect pavement behaviour. Stresses and

strains are induced in the pavement layers by

both the influences of traffic and environmental

stresses, an example of the latter being diurnal

temperature changes (Figure 2.2).

The bituminous surfacing suffers from tensile

strains at the bottom and the top of the layer

(2). The road-base, the sub-base and the

subgrade are mainly subjected to compressivestresses.

Theoretically, pavements will only behave as a

composite material under go ideal condition.

This condition exists only when the pavement

materials are homogenous and isotropic and the

adhesion between the component layers is per-

fect.

A point on the pavement subjected to a moving

load will deflect temporarily. The elastic prop-erties, characteristics of the component materi-

als and the loading nature and magnitude will

determine the size of the deflection. The tem-

porary deflection will rebound after the load

has been moved away from the spot. This

deflection is usually referred to as the transient

deflection.

Deflection measurements had been used as an

overall pavement strength indicator. Field

experiments from other authorities have shown

significant relationships between deflection val-

ues and pavement life. Deflection test results

can be used to predict the performance of pave-

ment and to design overlay thicknesses.

The behaviour of individual pavement layers

under traffic loadings can be very different.

Each has its own significant role in the overall

behaviour of a pavement.

2.4.1 Behaviour of thin surfacings



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Surface dressings mid slurry seals are the com-

mon types of thin surfacings used to seal road

pavements in Malaysia. These surfacings do

not provide direct structural strength to the

pavement.

Bituminous sealed road pavements are normal-

ly used in Malaysia for roads with low traffic

volumes and axle loads (low class road). There

is limited field experience and knowledge of

the behaviour of thin surfacings constructed on

high volume roads in the country.

Surface dressing have been used by many

developed countries for highways and high

class road pavements. Theoretically, if the road

base layers can be made to spread the loadimposed upon a pavement and meet the expect-

ed structural requirement, then a thin layer is

sufficient to fulfil the functional requirement of

a good riding surface. This is the adopted prin-

ciple behind the successful use of surface

dressings in developed countries.

Thin bituminous seals, and in particular surfac-

ing dressings, have high bitumen contents that

leads to high bitumen film thickness. They are

very flexible and are able to withstand highpressures from heavy wheel loads if construct-

ed properly. Furthermore, they should be able

to withstand environmentally induced stresses.

Bituminous surfacings with high bitumen con-

tents will have improved resistance against age

hardening. These properties cannot be obtained

from thick bituminous mixes since stability,

skid resistance and texture depth decrease with

increased bitumen content.

Strong adhesion with the road-base is another

important factor which determines the life of

thin seals. The proper application and curing of

the bituminous prime coat on the road base is

therefore vital to its perfornance.

Water can have a deleterious effect on this type

of construction. Serviceability will be reduced

if water is allowed to penetrate the surfacing.

The condition of surface and side drainage will

significantly affect the pavement behaviour and

performance. Therefore drainage is a major

area that must be emphasised during evaluation

on the performance of this type of road pave-

ment.

2.4.2 Behaviour of the component layers in

a typical flexible pavement.

Bituminous laver

The deflection experienced by the bituminous

layers due to a loaded wheel induces tensile

strains underneath the bituminous layer. Under

repeated loading this layer is liable to experi-

ence fatigue. Permanent deformation of the

subgrade and fatigue failure of the road surfac-

ing are the two major characteristics that are

normally used to predict flexible pavement per-formance.

The elastic behaviour of the bituminous mix is

mainly governed by the properties of the bitu-

men. Bitumen in the mix is visco-elastic and its

behaviour is highly dependent on temperature

and the rate of loading (3). At low temperatures

and short times of loading they are essentially

elastic but at high temperatures and long load-

ing times the material undergoes viscous flow.

The effective modulus is defined as the ratio ofstress to strain at a particular temperature and

loading time and is usually referred to as stiff-

ness. In practice, high stress areas such as

climbing lanes and junctions suffer long load-

ing time at high temperature therefore reducing

its modulus value (2). Deformation in the form

of shear failure in the surfacing is normally

prominent in these areas.

Laboratory tests have been carried out for vari-

ous types of bituminous mixes under repeated

loading to estimate fatigue failure. Apart from

the test procedures (e.g. testing temperature,

loading method or cycles), bitumen type, bitu-

men content and air void content in the mix

also influence the fatigue behaviour.

The time lapse between loading cycles is also

known to affect the test results. The type of

aggregate used is a secondary variable, and is

assumed to have negligible effect. Laboratory

fatigue tests under fully controlled conditions



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can produce more repeatable results compared

to those observed in empirical experiments.

In the field, cracks starting from the bottom of

the bituminous layer due to repetitive tensile

strain is normally called the traditional fatiguefailure. This form of failure slowly manifests

itself in the form of crocodile cracking in the

wheel-path and is easily identified by a surface

condition survey.

The factors that affect fatigue failure in the

field are loading pattern, channeling and mate-

rial properties. Laboratory fatigue values can

shift between 20 to nearly 700 times when

compared to those observed in the field (3).

This indicates that the behaviour of the individ-ual materials under laboratory conditions is

unfortunately not a good substitute for a thor-

ough knowledge of the behaviour of the mate-

rials when combined within a pavement.

Improvement in this area can only come from

the study of the behaviour of bituminous sur-

facings using empirical tests.

Additional compaction under repeated traffic

loading contributes to permanent deformation

that is normally manifested as rutting. Mixeswith high bitumen contents and are subjected

to loading at high temperatures are liable to

result in permanent deformation.

Environmentally induced stresses and strains

also affect bituminous surfacings. Temperature

changes will cause the bituminous material to

expand and contract. If the material is tempera-

ture susceptible, the stresses and strains

induced will cause thermal cracking.

Another common factor that hasten the deterio-

ration process significantly within the bitumen

surfacing in the tropics is the hardening of the

bitumen primarily at the surfacing (4). The top

layer of the bituminous mix can become brittle

and may crack easily under traffic loading or

temperature changes. This is common in surmy

and hot regions where the oxidation process is

rapid. The principal causes of bitumen harden-

ing are (5) :

i) Oxidation

ii) Loss of volatiles

iii) Physical hardening

iv) Exudative hardening

Oxidation is the main cause of hardening thatcan occur at storage, during mixing and on the

road. The bitumen viscosity of the top few

imillirnetres of the exposed surfacing changes

rapidly in our environment (6). Figure 2.3

shows a typical rate of hardening of binder in

service. The hardening is more severe in the

top 3 mm of the road surfacing and decreases

with depth. Figure 2.4 shows that the rate of

hardening is more rapid during the first 20

months. After this period, the rate decreases

until the binder viscosity reaches approximately6.2 log Poise. At this point, environmental age-

ing apparently ceases to have any further sig-

nificant effect. Suitable considerations and

allowances must be made to deal with this criti-

cal problem.

On bituminous roads, cracking and rutting are

usually more severe in,the verge-side (near-

side) wheel-path compared to the off-side

(outer-side) wheel-path. On the other hand, pol-

ishing of the road surface by vehicle tyres isnormally seen to be more severe on the off-side

wheel-path.

Unbound layer (road-base and sub-base)

Vertical compressive stresses affect the

unbound granular layer. The strength of this

layer is dependent on its elastic properties,

thicknesses and subgrade strength. The elastic

characteristic of this layer under repeated load-

ing is difficult to model. The modulus in the

vertical direction can be different from that in

the horizontal direction which suggest that it is

anisotropic.

The intrinsic properties of the material and

problems in setting up samples for laboratory

tests have resulted in the use of the term

'resilient modulus' instead of the usual modu-

lus' for this material. It is defined as the quo-

tient of repeated axial stress in triaxial com-

pression divided by the recoverable axial strain.



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In the laboratory repeated loading triaxial tests

can be used to studv the individual deformation

characteristic and resilient modulus of thislayer. The Poisson ratio can also be obtained.

The subgrade strength and the road-base layer

thicknesses affect the actual field properties of

the sub-base. This is common for all pavement

layers. Apart From individual properties,

surrounding properties affects actual field per-

formance. It was found in the United Kingdom

that nearly two thirds of the total permanent

deformation of the combined layer was con-

tributed by the surfacing and the unbound

layer.

Subgrade layer

The subgrade layer bears the final compressive

stress. The top one meter is the most critical

since it suffers almost all the transmitted load.

Properly designed and constructed road base

and sub-base layers will spread the load and

reduce the stresses induced by the vehicle on

the subgrade. The aim is to limit the compres

sive stress to an acceptable level so that the

subgrade will not fail or move under repetitive

loading.


Figure 2.4. Hardening Of Binder In The Top 3 mm Of The Road Surfacing

Figure 2.3. A Typical Rate Of Binder Hardening In Service


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The strength of a road subgrade is commonly

assessed in ternis of the California Bearing

Ratio (CBR). New pavements are mostly

designed using subgrade CBR values as the

primary soil strength indicator. It's popular use

in Malaysia has prompted development of rela-tionships to other useful soil-strength indica-

tors. The CBR and in general, the soil strength

is dependent on the type of the soil, its mois-

ture content and its density.

During pavement evaluation, the moisture con-

ditions primarily govern assessment decision. A

well-constructed pavement would have a sub-

grade in equilibrium moisture condition most

of the time and there will be no change in

behaviour. This scenario however is not achiev-able in most areas in Malaysia. The subgrade is

subjected to variable conditions in the

Malaysian environment. Two most common

conditions are :

i) Where the water table is near or possibly

higher than the formation level. This

water table will influence the subgrade

moisture content and also the pavement

layers above it.

ii) Where the water table is far from the

formation level but seasonal variation

and drainage efficiency will influence its

moisture conditions.

Pavements under condition (i) above, will be

weakest when the water table is at the highest

point. This may happen diurnally (tidal change)

or seasonally (monsoon season).Nondestructive

measurements that simulate pavement behav-

iour taken at these locations should consider

this. Measurements are best taken at the wettest

time, when the pavement is probably at its

weakest.

Heavy rainfall during wet weather allows mois-

ture to enter the pavement layers and the sub-

grade through the shoulder and at the edges.

This is more pronounced where earth shoulders

are used. Sealed road shoulders substantially

reduce the ingress of water. Drainage is the

most important factor that determines the

behaviour of the subgrade throughout its serv-

ice life. High standards of drainage provision

govern the longevity of pavement life at these

areas.

2.5 PAVEMENT PERFORMANCE

2.5.1 Terminal condition

Terminal pavement condition or the end of

pavement life is used to describe its condition

when major maintenance is needed. This con-

dition is predicted to occur at the end of the

design period.

The residual life of a road pavement is depend-

ent on the definition of the terminal condition.A pavement will have a residual life if its con-

dition has not reached terminal level.

In Malaysia, definition of terminal condition

and prediction of residual life were very

dependent on experience from other countries.

There are no standards on 'end of life' criteria

for Malaysian pavements as yet.

2.5.2 Users requirements

As mentioned in para. 2.1.1, the users' require-

ment is for safety and comfort. Only serious

pavement failure can be felt or measured in

relation to this. The AASHO road test in the

United States suggests a serviceability level of

2.5 as the terminal condition (1). At this level,

riding on the road will be uneconomical and

uncomfortable. However, the choice of this

level to be used locally needs careful study,

taking into consideration local pavement

behaviour.

2.5.3 Engineers and managers requirements

Two forms of distress modes can normally be

identified from the road pavement surface (i.e

cracking and rutting). The degree of cracking

or rutting or both are normally used as a gener-

al indicator of the overall pavement condition.

These failure manifestations can be used as a

criterion to quantify an empirical terminal con



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Page 17




dition. One of the empirical terminal condition

known (7), suggests the existence of both the

initial cracking and ten millimetres rutting as

failure criteria.

Theoretical or mechanistic terminal condition

will be based on asphalt strain or subgrade

strain criteria. The minimum permissible strain

level is currently based on laboratory findings

that can be reduced to mathematical formulae.

Typical examples are shown in Figures 2.5 and

2.6.

Various authorities had perform similar tests

and the formulae adopted are shown in Table

2.2. This terminal condition can be accepted if

the mechanistic model used depict exact field

behaviour.

The effect of age hardening in the field that

induce top-down cracking is not included in

those models. Allowance for this effect must be

made if the above terminal criteria are to be

used. At this juncture, empirical terminal condi-

tion seems to be more realistic and therefore it

is more reliable.

2.5.4. Empirical interpretation of

performance


Figure 2.6. Typical Strain-life Relationship For Subgrade (SHELL)

Figure 2.5. Typical Strain-life Relationship For Bituminous Mixes


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Empirical definitions and constraints

Predicting the field performance of visco-elas-

tic materials under variable loading patterns

and environmental conditions is not a simple

and straight forward task. Material strength andbehaviour are dependent on many variables

and involve the combined effect of other mate-

rials. The combinations of bitumen and aggre-

gate, on top of other unbound layers makes the

material difficult to model theoretically.

Fluctuations in moisture level within the pave-

ment create further uncertainties. Most theoreti-

cal models assume an equilibrium moisture

condition.

Empirical experiments are best carried outwhere the variables can be measured and con-

trolled. The performance can be monitored and

recorded. The recorded experience can be used

for future construction work or to assess exist-

ing pavement conditions provided similar

materials and specifications are used.

The empirical approach has been used widely

to design new road pavements and to assess

maintenance needs. The results are absolute but

are only applicable locally and its usage is lim-ited to similar materials and construction speci-

fications. Adaptation of this methodology

beyond its defined scope needs in-house verifi-

cation and modification especially if the envi-

ronment and materials used in the experiment

are different.

Past experiments and findings

The AASHO Road Test is perhaps the most

comprehensive pavement experiment ever

undertaken. Field behaviour and performance

of bituminous material were studied with con-

trolled repeated loading pattern under a specific

environment. Results from this test have been

accepted world-wide. One of the major find-

ings of the road test was the pavement fatigue

life definition in terms of repetition of a stan-

dard axle load. This principle had been extend-

ed and various other studies on bituminous

road pavements relate to these findings.

However, the modes of failure in a particular

local field condition can be very different from

what had been experienced in the road test.

Environmental effects

The major constraint in using experimentalresults carried out from other countries is the

existence of different soil types and environ-

mental conditions. Local experience is still

regarded as the best guide for the right solution.

These points had been proven from the various

findings from the AASHO road test. Studies

carried out by TRRL had shown that common

modes of failure in the tropics are often differ-

ent from those encountered in temperate

regions. These indicate that pavement behav-iour and performance in Malaysia would be

different and require different treatment and

emphasis.

Research work carried out at IKRAM shows

that cracking is the major failure mode on

asphaltic concrete overlays (8). Rutting is not a

major problem and only occurs on highly

stressed areas. Observations made over four

years on pavement o~7erlays throughout the

Peninsular Malaysia have produced sufficientdata to predict pavement performance in this

country.

2.5.5 Mechanistic interpretation of

performance

The constraints of the empirical design

approach have resulted in other methods being

developed to make it possible to predict other

modes of failure and possible usage of different

material types.

The structural analysis is to consider the pave-

ment, consisting of different materials. to be

characterised' by their elastic parameters which

are typical of dynamic load conditions. The

layered system concept (or multilayer elastic

system) is normally used. Many assumptions

must be made to model field behaviour to a

mechanistic model that can be computed math-

ematically. The major assumptions used in the

model are (9) :



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21/78

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i. The component layers are homogenous

and isotropic (the property at a point is

similar to that at another point and is the

same in any direction)

ii. Complete friction between layers at eachinterface

iii. The stress solutions are characterised by

the materials Poisson Ratio and modulus

values

iv. Each layer has a finite thickness and is

in ideal condition

v. Surface shearing force are not present at

the surface

vi. The material is infinite in the horizontal

direction

These assumptions are made clear in this guide

to caution users on indiscriminate use of the

theoretical methods. Specialised laboratory test

needs to be undertaken to support its proper

use. Field verification experiment governs the

validity of the approach.

Pavement response and model

The most common model used to date is the

three layer model. The road pavement is divid-

ed into three component layers :

i. the bituminous surfacings

ii. the unbound granular layer and

iii. the subgrade

More detailed four layer models that separate

the unbound layer into two layers can also be

used. However, the practicality and accuracy

obtained is still very subjective. More effort

should be given in handling variability in the

analysis (thickness of material and subgrade

condition) so that the accuracy of the

interpretation can be improved.

In the multilayer model, the pavement acts as a

composite structure. In theory, when the pave-

ment is subjected to a wheel load it will

respond and produce a temporary deflection

known as transient deflection. The deflection

can be measured in the field by various means

which will be discussed later in Chapter 3.

If the measured deflection is similar to the the-oretical deflection, then the elastic properties of

the material in the model could be used as an

estimate of its actual values in the field. The

analyses use the method of equivalent thick-

ness, normally required to analyse composite

structures under loading. Comparing the theo-

retical deflections to the actual field deflection

values is normally ternied 'backcalculation'.

This is an iterative process. Convergence accu-

racy of the iteration can be chosen as required.

The initial elastic properties for each laver haveto be estimated. The elastic properties of com-

ponent layers obtained are then used to esti-

mate the condition of the material.

It must be emphasised that the theoretical

model must be able to predict the actual failure

mode in the field for it to be used with reason-

able confidence. Failure to do so may result in

erroneous predictions.

Material fatigue problems have been investigat-ed in great detail in the laboratory by various

authorities and attention has now been directed

to the relationship between these results and the

fatigue performance of bituminous materials on

the road. It has been found that the fatigue life

of the bituminous materials under traffic condi-

tion in flexible pavements is considered longer

than that found in the laboratory. It is believed

that these resulted from the. differences

between conditions in the road and the test pro-

cedure adopted in the laboratory. As an exam-

ple, it has been suggested that a factor of 100

times is appropriate for condition in the U.K.

i.e. the field fatigue life is 100 times that in the

laboratory.

It is also very difficult to model climate related

failure in this approach. At this juncture, practi-

cal application of this approach may remain

conjectural.

Theoretical modes of failure



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The most common theoretical mode of failure

adopted in the model are fatigue failure at the

bottom of bituminous laver and deformation

failure on top of the subgrade. Additional fail-

ure on top of the unbound base is often includ-

ed. Theoretical deflections, stresses or strains atthese locations can be calculated using the

method of equivalent thickness. Research in the

laboratory can be used to measure stresses and

strains .at which pre-detennined failure condi-

tions occur and relationships established.

These failure modes were considered based on

experience overseas. Care must be taken in

accepting these as the only failure criteria.

Local research work carried out shows that the

top of the bituminous surfacing exposed toenvironmentally induced deterioration should

be considered. On-going research at IKRAM is

looking into this problem.

Materials characterisation

In multilayer analysis the material characteris-

tics namely Poisson Ratios, thicknesses and

elastic moduli are the main parameters to be

considered. The Poisson Ratio can be assumed

to be of a certain value based on laboratory andengineering experiences. Layer thicknesses can

be obtained from construction as built drawings

or measured directly in the field. The Elastic

modulus of each liver is the property that nor-

mally needs to be predicted.

Mechanistic terminal condition

In the mechanistic approach the terminal condi-

tion will be based on the calculated stresses and

strain levels. The terminal conditions are pre-

determined from laboratory experiments. The

stresses and strains described in para 2.-1.2 are

measured by repeated loading cycles applied in

laboratory conditions. The relationship between

repeated load cycles and strain level at failure

is plotted. Equations for the strain-life relation-

ships of the particular material can be obtained.

Residual life is determined by comparing the

strain estimated from the interpretation of

deflection measurement with the allowable

strain obtained from the laboratory relation-

ships. The strain level closest to the allowable

strain for a given type of material will indicate

the critical residual life.

Most stress-strain relationships available are for

materials that were obtained overseas. Thereare many different variables in the Malaysian

environment that must be simulated in order to

present actual loading and material conditions.

A recent research finding indicates a rapid

change in asphalt properties for the top layer

that are exposed to the environment. These

impose another consideration in the testing.

Laboratory fatigue test should also simulate

field loading frequency, otherwise a discrepan-

cy of the length of rest period between loading

will distort simulation.

Uncertainty

The major uncertainties using the mechanistic

approach are :

i. The validity of predicted failure

conditions,

ii. The discrepancy between conditions in

laboratory experiments compared to

those in the field,iii. The limitation and validity of the

assumptions used,

iv. The deficiency in the model that may

ignore actual field condition.

The above uncertainties can be overcome by

full-scale experiments under local conditions.

Computerised solutions

The mechanistic approach demands extensive

calculations and iterative computations whick

require time. Many computer programs exist in

the market. However, in principle almost all

will use the method of equivalent thickness and

back calculation procedures to estimate the

modulus values. Some packages have

advanced with full mechanistic bituminous

overlay design. The accuracy and reliability of

estimates from the computerised solution still

remain conjectural unless the problems in

mechanistic interpretation as described earlier



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can be overcome.

JKR currently have a number of computer pro-

grams undergoing tests. Recent developments

have found that the use of PHOENIX can pro-

duce reasonably practical estimation of modu-lus values. These values are sensitive to pave-

ment layer thicknesses. Astudy carried out by

TRRL found that the moduli estimations using

back-calculation procedure by four pavement

consultants were nearly similar. However, sub-

stantial differences in treatment recommenda-

tions and bituminous overlay thicknesses indi-

cate a general uncertainty over the evaluation

concepts.

Verification of mechanistic interpretation

Controlled field experiment is the best method

to verify mechanistics performance prediction

methods. Such work is now being undertaken

by IKRAM. The task is to develope a realistic

model depicting actual field conditions.

2.5.6 Future undertakings

There is understandable interest in the full

mechanistic approach that will result in greaterflexibility in the choice of materials. However,

this demands comprehensive laboratory and

field experiments for Malaysian materials and

environment. Suitable field deflection testing

equipment has been identified. Improvements

in the interpretation and modelling methodolo-

gy coupled with field verification is still in

progress.

2.6 REFERENCES

1. AASHTO Guide for Design of

Pavement Structures 1986, American

Association of State Highway and

Transportation Officials,

Washington D. C.

2. SHELL PAVEMENT DESIGN MAN-

UAL, Shell Petroleum Company Inc.,

London, 1978.

3. DAVID CRONEY, The Design and

Performance of Road Pavements,

Department of Environment,

Department of Transport, Transport and

Road Research Laboratory, HMSO,

London 1977.

4. ROLT, J. 'Flexible Pavement Design

Methods' Overseas Unit, Transport and

Road Research Laboratory, Crowthorne,

Berkshire, United Kingdom, 1987.

5. THE SHELL BITUMEN HAND

BOOK, Shell Bitumen U.K., 1990

6. PUBLIC WORKS DEPARTMENT,

The Deterioration of Bituminous

Binders in Road Surfacings, ResearchReport 5, Institute of Training and

Research, PWD Malaysia, 1991.

7. KENNEDY, C.K. and N.W. LISTER.

Prediction of pavement performance and

the design of overlays. Department of

the Environment, Department of

Transport, TRRL Report LR 833.

Crowthorne, 1978 (Transport and Road

Research Laboratory).

8. PUBLIC WORKS DEPARTMENT,

Long Term Performance Study of

Overlays, Institute of Training and

Research, PWD Malaysia, 1989.

9. YODER. ,E.J, WITCZAK. M.W.,

Principles of Pavement Design, 1975.

CHAPTER 3 :

PAVEMENT EVALUATION

3.1 GENERAL

The pavement evaluation processes practised in

the JKR road pavement maintenance are at

three levels. These was described earlier in

Chapter 1 as the System Level, Network Level

and Project Level. For the network level, pave-

ment evaluation requires a different methodolo-

gy and equipment. The scope of evaluation

methodology is described in detail elsewhere.



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This chapter deals with pavement evaluation at

project and detail level. The choice of equip-

ment, information quality requirement, accura-

cy, methods of analysis and techniques used are

given.

The main steps of the evaluation can be sum-

marized as follows :

i) To divide the road into suitable lengths

of design sections

ii) Predict the mode of failure

iii) Identify failure causes and delimit the

failure area

iv) Select suitable short or long term reme

dial solutions

The above can be carried out efficiently by

dividing the tasks into two assessment tiers, ini-

tial and detail assessments. The scope of work

in the process is shown in Figure 3.1. Brief

description of the flow of the work is given

below.

3.1.1 Project initiation

There are two normal mechanisms that initiate

pavement evaluation at the project level :

i) From network level priority listing

ii) Specific evaluation request when a

pavement requires upgrading due to

special reasons

After a specific budget has been allocated for a

project in a network priority list, a detailed

pavement evaluation is normally required to

optimise the budget. This evaluation exercise is

necessary as the condition of the pavement

may have changed since it was evaluated dur-

ing the network level pavement survey. For

accurate results, the time lapse between the

evaluation exercise and the commencement of

the rehabilitation construction must be min-

imised.

3.1.2 Physical condition assessment

Simple physical condition assessment of the

pavement at the beginning of the evaluation

exercise helps efficient organisation of this

task. This can be done visually or using a sim-

ple and cheap methods. A general condition of

the pavement is recorded. A decision should be

made at this juncture whether the pavement is

suffering from structural or non-structural fail-

ure. If it is structurally sound, its functionalcondition should be queried. If the pavement is

both structurally and functionally adequate then

the pavement is considered sound, otherwise

detail testing will be needed.

3.1.3 Non-destructive testing (NDT)

Non-destructive testing is currently the state-of

the-art method for detailed pavement

investigation.The selection of NDT devices is

described in para 3.3.2. NDT allows more datacollection along the road and provides a more

confident representation of the pavement con-

dition. It is necessary not to miss any weak

areas at this level of testing. This testing will

provide the base data for analysis and rehabili-

tation design.

3.1.4 Analysis and rehabilitation design

The base data from the NDT tests together with

other information that was taken previously iscompiled and analysed at this stage. Additional

tests may be required if the information is not

sufficient. Suitable methods of analysis are

applied to produce recommendations of reme-

dial measures and the procedure of choosing

the appropriate method is described in para

3.3.3.

3.1.5 Selection of remedial measures

This can be the most important part of the eval-

uation exercise. A detailed description and

interim guide for this task is explained in

Chapter 5. The first step is to understand and

diagnose the pavement problem. This will then

help to provide the solution. The correct solu-

tion is not always easy to achieve. Longtenn

engineering solution should be chosen at this

juncture. It must be assumed that budget is not

a constraint at this stage.



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3.1.6 Cost analysis

With budget constraints, the balance between

engineering or non-engineering driven solution

must be considered carefully. This scenerio is

common in Malaysia. A simple costing analysis

of the remedial measures may provide suffi-

cient answers to the problem.

The costing analysis should provide informa-

tion to ascertain the budget requirements. If the

cost of actual rehabilitation requirement exceed



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tire allocated budget, the rehabilitation solution

may require changes. Short terns and long term

remedial measures are selected depending on

the allocated budget. Staged constriction is

another option worth considering in order to

reduce initial rehabilitation costs but still fulfillsthe engineering requirement.

The feasibility of various remedial measures

may involve discussions with the appropriate

authorities before the final options are selected.

Other feasible remedial methods can be applied

if the conventional method are not appropriate

or slow.

3.1.7 Implementation

Projected actual time of implementation of the

evaluation proposal should be considered dur-

ing the evaluation exercise. The estimates of

remedial works normally increase if the time

lapse between the evaluation period and the

implementation phase is expected to be long.

This is common in Malaysia. where contractual

arrangements are often lengthy. Allowance for

this problem should be considered in the evalu-

ation exercise.

3.2 INITIALASSESSMENT

Pavement evaluation at project level starts by

carrying out an initial assessment of the physi-

cal condition of the pavement. The principle is

to use cheap equipment and simple method of

assessment. More expensive and detailed tests

can be scheduled if and when required.

Engineers nonually carry out or supervise this

work. The scope of work involves two main

tasks :

i) Surface condition assessment

ii) Drainage assessment.

Other information related to the surroundings

of the pavement helps to ensure a comprehen-

sive evaluation work. Historical data of the

pavement would be very useful if available.

However, it is not mandatorv to have this data

to accomplish the pavement evaluation task.

The results from this initial assessment will be

used to :

i) Decide preliminary lengths and loca

tions of `design sections'

ii) Plan for the frequency and interval ofdetailed tests

Optimum and economical data collection and

sampling can be carried out following the

selection of the design sections. The final rec-

ommendation of rehabilitation measures should

be adiusted to suit these individual sections.

A minimum length of a selected design section

should not be less than one kilometre to allow

for efficient construction operation. Preliminarydesign sections are chosen first from the initial

assessment results. At a later stage, other infor-

mation such as soil type, topography, hydrolo-

gy, deflection and traffic data can influence the

final selection of the design sections. The engi-

neer should carefully review all the available

data to judge whether a particular treatment is

suitable over the entire project length or

whether shorter design sections using separate

treatments are necessary. Changing remedial

treatments too frequently may result in difficultand expensive construction.

3.2.1 Surface condition assessment

The surface condition survey provide a means

of quantifying the failures of the pavement,

shoulder and drainage. Using appropriate tech-

niques, the extent of the failures can be classi-

fied and quantified. Astandard surface condi-

tion survey method has been used in JKR. The

main parameters recorded are cracking and rut-

ting as well as shoulder and drainage condi-

tions. Details of the information recorded is

shown in Table 3.1.

Visual assessment of cracks using a classifica-

tion system simplified in Table 3.2 provide suf-

ficient information for further analysis. It is

easier to divide each section into short 10

metres block for accurate and efficient data col-

lection. Alternative lengths of sections can be

used. A straight edge and a wedge are used to



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measure the rut depth within the block

(late 3.1). The maximum rut depth in the block

is measured. The location of the maximum rut

depth is estimated visually. The condition of

shoulders and side drainage facilities are initial-

ly assessed by visual judgement. Afull assess-ment of the drainage condition can be made

separately if necessary. This will be described

in more detail inpara. 3.2.2.

The personnel needed to carry out the surface

condition survey vary depending on the traffic

intensity of the site. Plate 3.2 shows the com-

mon personnel layout on a low volume road

with fast traffic. Four persons are required to

collect the data and two persons are needed to

control the traffic flow. Safety requirementsvary from site to site. Safety jackets must be

worn. Police assistance is recommended at

locations with very heavy traffic.

Surface condition surveys must be carried out

during the day time. It should not be carried out

at night unless proper lighting is provided.

3.2.2 Drainage assessment

The condition of surface and side drainage ofthe pavement will contribute significantly to its

performance. Aclassification of its condition

will indicate whether this is the primary or con-

tributory cause of damage to the pavement

structure. Some existing road pavements have

been upgraded from previous construction that

may not have emphasised on drainage provi-

sion. Sometimes the drainage has disappeared

through sequence of widening work. It is

important to remedy drainage problems before

any pavement rehabilitation work is imple-

mented. Water is the most important environ-

mental factor that influences pavement per-

formance. Prediction of moisture condition

and the resulting variation in pavement

response is still a major unsolved problem that

has not deen defined precisely in any pavement

design method.

Adequate provision of drainage facilities will

minimise this area of uncertainty. Keeping

water away from pavement materials is still the

best solution especially where heavy rainfall is

expected.

Surface drainage is judged by the ability of the

pavement surface to drain water rapidly, not

allowing water to pond either on the bitumi-

nous surfacing or on the road shoulder.Observation is best carried out after or during

rainfall when the road surfacing is still wet. The

results of these observations should provide an

indication whether it is necessary to improve

the cross section profile of the pavement and

the road shoulder. This is critical if the probable

maintenance measures would only need minor

treatment such as sealing or cut and patch.

The structural drainage condition is more diffi-

cult to assess. Past construction records will behelpful if available. This assessment is more

critical in hilly areas where the pavement is

constructed on cut slopes. The engineers need

to judge with reasonable confidence by obser-

vation whether a particular area requires sub-

soil drainage, side drains or interceptor drains

or whether existing drains are sufficient

and functioning properly to safeguard the pave-

ment. Failure as a result of drainage deficiency

would have been very obvious by the time the

pavement undergoes investigation. Comparisonto similar pavement construction on adjacent

areas that have good drainage provision can

assist on the judgement of the drainage condi-

tion.

3.2.3 Preliminary analysis, sectioning

The existing pavement construction and the

underlying condition of the pavement structure

govern the initial selection of homogeneous

sections within a road length having a uniform

traffic loading. Visual surface condition data

and deflection results can be used to refine the

sections. Statistical analysis can be used to

define representative characteristics and homo-

geneity of key parameters within the sections.



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Confidence level of 85%,


Crack Type Crack Width Crack Extent

0 - No Cack - -

1 - Single crack < 1 mm < 1 m

2 - Many cracks 1 - 3 mm 1 - 5 m

3 - Interconnected cracks > 3 mm > 5 m

4 - Crocodile cracks > 3 mm and spalling -

5 - Crocodile cracks and

spalling- -

Table 3.2 Classification of cracks

Plate 3.1. Rut Depth Measurement

Plate 3.2. Surface Condition Survey


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or more is recom

mended for statistical representation. Adjacent

sections must not contain significantly similar

attributes. Significant tests should be carried

out to resolve this problem.

The distribution and population mean of the

deflection, rutting, cracking and other quanti-

fied failures highly influence the proposed

method of treatment. The primary mode of fail-

ure often dictates preliminary sectioning.

Sectioning by evidence of cracking

Cracking suggests that predominant failure

mode is either by traditional fatigue or age

hardening. If the road has been overlaid thecracking can often be reflective cracking from

an overlaid surfacing. Pavement strength that is

mostly defined by the layer thicknesses can

influence the degree of cracking and its distri-

bution. Information on pavement layer thick-

ness will help in the selection of the sections.

This method of sectioning is not suitable for a

road pavement that has been inadequately

maintained and has extensively failed.

Sectioning by rutting severity

Severity of rutting can sometimes be used to

assist preliminary sectioning. Areas with uni-

form problems of material stability can be iden

tified. Rutting normally indicates evidence of

asphalt instability or weak underlying layers.

Rutting alone is not the predominant failure

manifestation where weak underlying layer

exists. Cracking and rutting normally appears

in this area. Sectioning by rutting alone will

suggest the predominant role of asphalt insta-

bility.

Sectioning by formation type

The contribution of the strength of the subgrade

to road failure can result in variations in either

cracking or rutting or both. Distinct formation

types exist in hilly areas and are common in

this country. Fill areas are prone to construction

deficiency where quality of imported subgrade

may effect the pavement performance.

Drainage and ground water condition influence

the performance and stability of cuttings.

Drainage deficiency could provide further evi-

dence to justify division into sections. Distinct

differences in failure at different formationtypes indicates the suitability of sectioning by

formation types.

3.3 DETAILED ASSESSMENT

3.3.1 General

The next stage in the evaluation process is the

detail assessment of the road pavement. The

assessment can be either the structural condi-

tion or the surface characteristics of the roadpavement. In most project level assessments

that lead to major rehabilitation, the structural

condition assessment is vital. The surface func-

tional requirement may not be critical since

major reconstruction requires the existing sur-

face to be removed.

The strength of the existing pavement needs to

be measured. The results from those tests will

assist in identifying the mode of failure.

The current interest world-wide is to use Non

Destructive Testing (NDT) devices. NDT is a

preferred approach that is fast and reduces or

eliminates laborious and expensive destructive

testing (1).

Destructive testing can give a more accurate

indication of the condition and performance of

pavement materials at a specific location.

However, it is likely that high variability of

pavement layer thicknesses and material condi-

tions over a long stretch of road exists. This is a

common situation along most roads in

Malaysia. It is therefore more important to con-

centrate the evaluation effort in achieving accu-

rate true mean characteristics of the materials

from adequate sampling over the stretch con-

cerned. Putting emphasis on achieving an accu-

rate single sample characteristics could distort

the overall scenario.

NDT surveys for the structural assessment



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should be conducted at the time of the year

when the pavement is at its weakest due to sea-

sonal environmental condition. Relationships

between environmental factors and deflections

need to be established to know when the pave-

ment will be at its weakest. For a start anassumption can be made that the pavement is at

its weakest after the monsoon season. Diurnal

temperature variation must be considered as

well. Deflection reading is best taken close to

the standardised temperature of 40C to reduce

temperature correction error. Proper tempera-

ture correction relationships for different types

of surfacing should also be established.

Temperature susceptibility of bituminous mixes

varies with mix types and conditions. Different

temperature corrections are required for differ-ent mixes. Temperature correction becomes

more significant as the pavement gets hotter

during the day whereby the deflection response

becomes more sensitive as the surfacing gets

softer. It is not significant if the surface has

severely cracked.

NDT equipment is available in many forms.

Broadlv, they can be divided into two major

groups :

i) Deflection-based equipment

ii) Non-deflection-based equipment

There are three mechanised deflection-based

systems most commonly used in Malaysia.

Non-deflection based systems are equipment

using radar sensors, nuclear devices, ultrasonic

devices, laser sensors and penetrometers such

as die Dynamic Cone Penetrometer.

Currently JKR uses four types of NDT equip-

ment to evaluate structural condition of pave-

ment. The sophisticated machines are the

Falling Weight Deflectomcter (FWD) and the

Road Rater. The simpler devices are the

Dynamic Cone Penetrometer (DCP) and the

Benkelman Beam. Description of this equip-

ment and its usage is covered in para. 3.3.2

below.

The background to the NDT approach of stnic-

tural assessment was explained in Chapter 2. It

must be emphasised here that the accuracy of

the results will depend on the experience of the

user in handling all evaluation information

described earlier including the NDT results. No

in-house study has compared the results pro-

duced by each device and its approach.Preference in the choice of equipment will

depend on speed of test, safety, cost of equip-

ment, maintenance, reliability and case of use.

Another factor that could be important is the

authority's requirements and emphasis for spe-

cific aspects of testing. Safety of the public

during any testing on the road is of paramount

importance. Test vehicle sometimes may be

disallowed from stopping on the road. Amov-

ing test equipment (such as Deflectograph)

could be preferred for such case. However, thistype of equipment can be very, expensive and

not easily maintained.

Comprehensive understanding of the elements

involved in the detailed pavement assessment

is critical. Over-emphasizing certain aspects of

the elements can lead to uneconomical deci-

sions. It inav be necessary to carry out cost-

benefit analyses when choosing the most suit-

able NDT equipment for the pavement evalua-

tion.

3.

Documents

Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94