8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
1/78
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
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
2/78
Page 1
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
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
3/78
Page 2
Interim Guide To Evaluation AndRehabilitation Of Flexible Road pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
4/78
Page 3
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
5/78
Page 4
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
6/78
Page 5
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
7/78
Page 6
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
8/78
Page 7
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
FOR INTERNAL USE ONLY
Figure 1.1 Elements In Pavement Evaluation
Fugure 1.2 Decision Making Levels In Pavement Maintentenance
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
9/78
Page 8
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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
FOR INTERNAL USE ONLY
Fugure 1.3 Cross-section Of A Typical Flexible Road Pavement
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
10/78
Page 9
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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-
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
11/78
Page 10
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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).
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
12/78
Page 11
Interim Guide To Evaluation AndRehabilitation Of Flexible Road pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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,
FOR INTERNAL USE ONLY
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
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
13/78
Page 12
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
14/78
Page 13
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
15/78
Page 14
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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.
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
16/78
Page 15
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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.
FOR INTERNAL USE ONLY
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
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
17/78
Page 16
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
18/78
Page 17
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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
FOR INTERNAL USE ONLY
Figure 2.6. Typical Strain-life Relationship For Subgrade (SHELL)
Figure 2.5. Typical Strain-life Relationship For Bituminous Mixes
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
19/78
Page 18
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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) :
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
20/78
Page 19
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
21/78
Page 20
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
22/78
Page 21
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
23/78
Page 22
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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.
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
24/78
Page 23
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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.
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
25/78
Page 24
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
26/78
Page 25
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
27/78
Page 26
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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.
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
28/78
Page 27
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
29/78
Page 28
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
Confidence level of 85%,
FOR INTERNAL USE ONLY
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
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
30/78
Page 29
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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
FOR INTERNAL USE ONLY
8/3/2019 Interim Guide to Evaluation and Rehabilitation of Flexible Road Pavements - JKR 20709-0315-94
31/78
Page 30
Interim Guide To Evaluation And
Rehabilitation Of Flexible Road Pavements.
Cawangan Jalan, Ibu Pejabat JKR, K.L
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.