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

JKR 20709-0315-94

Interim Guide To Evaluation And Rehabilition Of Flexible Road Pavements

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Roads Branch Public Works Department Malaysia Jalan Sultan Salahuddin 50582 Kuala Lumpur

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Interim Guide To Evaluation And Rehabilitation Of Flexible Road pavements.

INTERIM GUIDE TO EVALUATION AND REHABILITATION OF FLEXIBLE ROAD PAVEMENT IKRAM can accept no responsibility for misappropriate 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 condition.

performance under Malaysian climatic conditions 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

Photographs and drawings of equipment in this publication are for illustration only and do not imply preferential endorsement of any particular 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, particularly in relation to the pavement behaviour and Cawangan Jalan, Ibu Pejabat JKR, K.L

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 understood. However, to facilitate the early understanding of the present practices, this interim guide has been produced. The authors are Page 1

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aware of the necessary work still needed to complete this guide and are, at present, undertaking research to make this possible. The chapters have been written so that they can be read and understood largely independent of each another, but where necessary cross-referencing to specific paragraphs should make the reader's task easier.

Interim Guide To Evaluation And Rehabilitation Of Flexible Road pavements. 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

This guide aims to be factual but some expression of opinion is inevitable where gaps in knowledge exist. ACKNOWLEDGEMENTS This guide is prepared by the Pavement Research 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 guidelines on the design, construction and maintenance 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 heartCawangan Jalan, Ibu Pejabat JKR, K.L

1.1. BACKGROUND 1.1.1 Brief history of Malaysian road pavements 1.1 1.1.2 The need for engineering evaluation 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 1.2.1 Limitation of the Guide 1.3 OBJECTIVES

1.3 1.4 1.4

CHAPTER 2 : PAVEMENT BEHAVIOUR 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

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2.3 FAILURE DEFINATIONS

Interim Guide To Evaluation And Rehabilitation Of Flexible Road Pavements. 2.3

3.1.6 Cost analysis

3.3

2.3.1 Failure modes

2.3

3.1.7 Implementation

3.3

2.3.2 Failure manifestation

2.3

3.2 INITIAL ASSESSMENT

3.3

2.3.3 Failure mechanisms

2.3

3.2.1 Surface condition assessment 3.4

2.4 PAVEMENT BEHAVIOUR

2.3

3.2.2 Drainage assessment

3.4

2.5

3.2.3 Prelirninarv analysis, sectioning

3.7

2.4.1 Behaviour of thin surfacing

2.4.2 Behaviour of component lavers in a typical flexible pavement 2.5 2.5 PAVEMENT PERFORMANCE 2.9

3.3 DETAIL ASSESSMENT

3.8

3.3.1 General

3.8

2.5.1 Terminal condition

2.9

3.3.2 Choice of NDT devices

3.9

2.5.2 Users requirements

2.9

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

2.5.3 Engineers and managers requirements

2.9

2.5.4 Empirical interpretation of performance

2.12

2.5.5 Mechanistic interpretation of performance

2.12

2.5.6 Future undertakings

2.15

3.3.6 Other key factors to consider during evaluation 3.26 3.3.7 Detail material investigation

2.6 REFERENCES

3.4 REFERENCES CHAPTER 3 : PAVEMENT EVALUATION 3.1 GENERAL 3.1.1 Project initiation

3.29

2.15 3.31

CHAPTER 4 : TRAFFIC LOADING ASSESSMENT 3.1 4.1 GENERAL

4.1

4.2 TRAFFIC CATEGORIES

4.1

3.1

3.1.2 Physical condition assessment 3.1 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

3.1.3 Non-destructive testing (NDT) 3.1 3.1.4 Analysis and rehabilitation design 3.1.5 Selection of remedial measures Cawangan Jalan, Ibu Pejabat JKR, K.L

3.3

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4.3 TRAFFIC AND AXLE LOAD SURVEYS

4.2

4.3.1 Specific survey method

4.2

4.4 FORECASTING FUTURE TRAFFIC

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

Figure 1.3

Cross-section of a typical flexible 1.4

Figure 2.1

Typical serviceability requirements for different class of road (AASHO Road Test) 2.2

Figure 2.2

Stresses and strains in a bituminous pavement (Asphalt Institute) 2.4

Figure 2.3

A typical rate of binder hardening in service

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

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 FIGURES Figure 1.1 Elements in pavement evaluation Figure 1.2

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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

1.2

Decision making levels in road pavement maintenance 1.3

2.7

3.23

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Figure 3.10. Typical plot of the DCP results

Interim Guide To Evaluation And Rehabilitation Of Flexible Road Pavements. Table 3.5

Estimates of structural coefficients, based on DCP in-situ CBR values. 3.22

3.23

Figure 3.11. Micro and macro-lextUre 3.25 Figure 5.1

Figure 5.2

Figure 5.3

Figure 5.4

Table 4.1 General Process for Selecting Appropriate Rehabilitation Alternatives 5.2

Typical HPU traffic survey results 4.3

Table 4.2

Axle load survey results for direction 1, Southbound. 4.6

The Spectrum of Pavement Rehabilitation Alternatives 5.3

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

Distribution of yearly damaging effect

4.8

Replacement of Loss Chemical Constituents by Rejuvenation 5.5 Proper methods of cutting and patching 5.9

Table 4.5

Figure 5.5

Surfacing Recycling Using Hot Milling Method 5.16

Table 4.6

Figure 5.6

Methods of Reducing Reflection Cracks Using Interlayers

LIST OF PLATES 5.18

Full Reconstruction Options

5.23

Summary of traffic counts results obtained from HPU.4.9

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

Surface condition survey form. 3.5

Plate 3.7 The Griptester

3.27

Table 3.2

Classification of cracks

3.6

Plate 3.8 Sand Patch test

3.27

Table 3.3

Material condition intrepetation

Plate 3.9 TRRL Minitexture meter

3.28

3.20 Plate 3.10 The Friction Tester

3.28

Plate 4.1 Axle load weighing

4.3

Figure 5.7

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

Table 3.4

Estimated values of structural coefficients for various conditions of asphalt. 3.22

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Interim Guide To Evaluation And Rehabilitation Of Flexible Road Pavements.

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 pavements. 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 construction method is still being practiced today. To ensure the smooth operation of the road network, 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 Cawangan Jalan, Ibu Pejabat JKR, K.L

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 system was only introduced in Malaysia in 1974 when a Benkelman Beam survey of 2291 km of Federal and State roads was carried out by_ KAMPSAX International. 1.1.2 The need for engineering evaluation 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 engineering records 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 pavements can fulfill this requirement. This allows the 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 evaluation process, the identification and classification 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 properties (Figrure 1.1). Field measurements are valuable practical tools in the evaluation of road performance and in the identification of the causes of failure. The task becomes more difficult if the pavement has gone through a series Page 6

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Figure 1.1 Elements In Pavement Evaluation

Fugure 1.2 Decision Making Levels In Pavement Maintentenance

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Interim Guide To Evaluation And Rehabilitation Of Flexible Road Pavements.

of previous unrecorded maintenance treatments. 1.1.3 Economic analysis as part of engineering 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 economic needs are considered are dependent on the level at which decisions are made (Figure 1-2). 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 decision 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 government to use engineering-based criteria to maintain and upgrade the road networks. With the introduction 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 carrying out an engineering evaluation on flexible pavements that allows a better decision to be made at the Project Level. It incorporates brief and relevant discussions of behaviour, performance 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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Interim Guide To Evaluation And Rehabilitation Of Flexible Road Pavements. facing overlying the natural ground or subgrade.

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 information 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 performance of the pavements addressed in this guide is for flexible pavements only. A typical flexible 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 pavement 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 BEHAVIOUR AND PERFORMANCE 2.1. PAVEMENT COMPONENTS AND MATERIALS A flexible pavement is a layered structure consisting of the sub-base, road-base and the surCawangan Jalan, Ibu Pejabat JKR, K.L

2.1.1 Surfacing ]The surfacing is the upper layer of the pavement 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 conditions The form of bituminous surfacing commonly used can either be thick or thin. Thick bituminous 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 subbase 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 roadPage 9

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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 nornally consist 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 roadbase by the subgrade and also acts as a preparatory 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 pavement within a depth of approximately 1 meter below the subbase. It is the upper layer of earthworks prepared for subsequent construction of the pavement layers described above.It can either be natural undisturbed soil or compacted 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 FLEXIBLE PAVEMENT The general function of a road pavement is to Cawangan Jalan, Ibu Pejabat JKR, K.L

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 aesthetic aspect of it is also a concern but will receive considerable attention only on heavily trafficked 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 surface 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 introduced during the AASHO Road Test to represent pavement performance. The road pavement 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). Page 10

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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 intervention. The road user may not be aware of the occurrence of early deterioration since the riding quality may still be acceptable. In contrast the engineer must be alert to such problems as early maintenance enhances the road performance. It is thus necessary to understand the behaviour and performance of road pavement under Malaysian condition. In evaluating and rehabilitating a road pavement in this country, where the environmental factors are different from Mode

Manifestation

Western nations, there are dangers in applying those rehabilitation solutions that have been obtained elsewhere as they may not suit conditions in this country without some modification. Road user and engineering needs must be properly balanced to suit budget requirements and maximise benefit through appropriate methods of maintenance. Experience elsewhere has indicated that prompt maintenance can indeed save expensive reconstruction costs. 2.3

FAILURE DEFINITIONS

2.3.1 Failure modes The predominant failure modes are fracture, Comman Mechanisms

Frature

Cracking

Excessive loading Repeated loading Moisture changes Age hardening

Distortion

permanent Deformation

Excessive 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 deformation. Disintegration will normally take place on the 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 pavements most commonly manifests itself as cracking or deformation. These defects can be 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 loading iii) 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 dependent on accurate identification of actual modes of failure. The relationship between failure mode, their manifestations and probable mechanisms is as shown in Table 2.1. 2.4

tion methodology, it is necessary for a road engineer to understand pavement behaviour especially under local environmental conditions. Repeated axle loading, the environment, soil characteristics 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 compressive stresses. 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 perfect. A point on the pavement subjected to a moving load will deflect temporarily. The elastic properties, characteristics of the component materials and the loading nature and magnitude will determine the size of the deflection. The temporary 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 values and pavement life. Deflection test results can be used to predict the performance of pavement 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.

PAVEMENT BEHAVIOUR 2.4.1 Behaviour of thin surfacings

Before moving further into pavement evaluaCawangan Jalan, Ibu Pejabat JKR, K.L

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Surface dressings mid slurry seals are the common 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 normally 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 load imposed upon a pavement and meet the expected structural requirement, then a thin layer is sufficient to fulfil the functional requirement of a good riding surface. This is the adopted principle behind the successful use of surface dressings in developed countries. Thin bituminous seals, and in particular surfacing dressings, have high bitumen contents that leads to high bitumen film thickness. They are very flexible and are able to withstand high pressures from heavy wheel loads if constructed properly. Furthermore, they should be able to withstand environmentally induced stresses. Bituminous surfacings with high bitumen contents 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 Cawangan Jalan, Ibu Pejabat JKR, K.L

area that must be emphasised during evaluation on the performance of this type of road pavement. 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 experience fatigue. Permanent deformation of the subgrade and fatigue failure of the road surfacing are the two major characteristics that are normally used to predict flexible pavement performance. The elastic behaviour of the bituminous mix is mainly governed by the properties of the bitumen. 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 loading times the material undergoes viscous flow. The effective modulus is defined as the ratio of stress to strain at a particular temperature and loading time and is usually referred to as stiffness. In practice, high stress areas such as climbing lanes and junctions suffer long loading 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 various 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, bitumen 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 Page 13

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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 fatigue failure. 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 material 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 individual materials under laboratory conditions is unfortunately not a good substitute for a thorough knowledge of the behaviour of the materials when combined within a pavement. Improvement in this area can only come from the study of the behaviour of bituminous surfacings using empirical tests. Additional compaction under repeated traffic loading contributes to permanent deformation that is normally manifested as rutting. Mixes with high bitumen contents and are subjected to loading at high temperatures are liable to result in permanent deformation.

i) ii) iii) iv)

Oxidation Loss of volatiles Physical hardening Exudative hardening

Oxidation is the main cause of hardening that can 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 approximately 6.2 log Poise. At this point, environmental ageing apparently ceases to have any further significant effect. Suitable considerations and allowances must be made to deal with this critical problem. On bituminous roads, cracking and rutting are usually more severe in,the verge-side (nearside) wheel-path compared to the off-side (outer-side) wheel-path. On the other hand, polishing of the road surface by vehicle tyres is normally seen to be more severe on the off-side wheel-path. Unbound layer (road-base and sub-base)

Environmentally induced stresses and strains also affect bituminous surfacings. Temperature changes will cause the bituminous material to expand and contract. If the material is temperature susceptible, the stresses and strains induced will cause thermal cracking. Another common factor that hasten the deterioration 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 hardening are (5) :

Cawangan Jalan, Ibu Pejabat JKR, K.L

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 loading 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 ‘modulus' for this material. It is defined as the quotient of repeated axial stress in triaxial compression divided by the recoverable axial strain. Page 14

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Figure 2.3. A Typical Rate Of Binder Hardening In Service

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

In the laboratory repeated loading triaxial tests can be used to studv the individual deformation characteristic and resilient modulus of this layer. 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 performance. It was found in the United Kingdom that nearly two thirds of the total permanent deformation of the combined layer was contributed by the surfacing and the unbound

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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.

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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 relationships to other useful soil-strength indicators. The CBR and in general, the soil strength is dependent on the type of the soil, its moisture content and its density. During pavement evaluation, the moisture conditions primarily govern assessment decision. A well-constructed pavement would have a subgrade in equilibrium moisture condition most of the time and there will be no change in behaviour. This scenario however is not achievable 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 behaviour 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 moisture to enter the pavement layers and the subgrade 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 Cawangan Jalan, Ibu Pejabat JKR, K.L

behaviour of the subgrade throughout its service 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 condition is predicted to occur at the end of the design period. The residual life of a road pavement is dependent on the definition of the terminal condition. A pavement will have a residual life if its condition 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' requirement 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 general 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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Figure 2.5. Typical Strain-life Relationship For Bituminous Mixes

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

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

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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 condition seems to be more realistic and therefore it is more reliable. 2.5.4. Empirical interpretation of performance

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Empirical definitions and constraints Predicting the field performance of visco-elastic materials under variable loading patterns and environmental conditions is not a simple and straight forward task. Material strength and behaviour are dependent on many variables and involve the combined effect of other materials. The combinations of bitumen and aggregate, on top of other unbound layers makes the material difficult to model theoretically. Fluctuations in moisture level within the pavement create further uncertainties. Most theoretical models assume an equilibrium moisture condition. Empirical experiments are best carried out where the variables can be measured and controlled. The performance can be monitored and recorded. The recorded experience can be used for future construction work or to assess existing 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 limited to similar materials and construction specifications. Adaptation of this methodology beyond its defined scope needs in-house verification and modification especially if the environment 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 controlled repeated loading pattern under a specific environment. Results from this test have been accepted world-wide. One of the major findings of the road test was the pavement fatigue life definition in terms of repetition of a standard axle load. This principle had been extended and various other studies on bituminous road pavements relate to these findings. However, the modes of failure in a particular Cawangan Jalan, Ibu Pejabat JKR, K.L

local field condition can be very different from what had been experienced in the road test. Environmental effects The major constraint in using experimental results carried out from other countries is the existence of different soil types and environmental 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 different from those encountered in temperate regions. These indicate that pavement behaviour 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 sufficient data 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 pavement, 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 mathematically. The major assumptions used in the model are (9) : Page 18

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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)

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.

ii. Complete friction between layers at each interface

If the measured deflection is similar to the theoretical 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 thickness, normally required to analyse composite structures under loading. Comparing the theoretical deflections to the actual field deflection values is normally ternied 'backcalculation'. This is an iterative process. Convergence accuracy of the iteration can be chosen as required. The initial elastic properties for each laver have to be estimated. The elastic properties of component layers obtained are then used to estimate the condition of the material.

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 divided 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 pavement is subjected to a wheel load it will Cawangan Jalan, Ibu Pejabat JKR, K.L

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 reasonable confidence. Failure to do so may result in erroneous predictions. Material fatigue problems have been investigated 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 condition 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 procedure adopted in the laboratory. As an example, 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, practical application of this approach may remain conjectural. Theoretical modes of failure Page 20

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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 failure on top of the unbound base is often included. Theoretical deflections, stresses or strains at these 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 conditions 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 to environmentally induced deterioration should be considered. On-going research at IKRAM is looking into this problem. Materials characterisation In multilayer analysis the material characteristics 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 and engineering 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 normally needs to be predicted. Mechanistic terminal condition In the mechanistic approach the terminal condition will be based on the calculated stresses and strain levels. The terminal conditions are predetermined 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 relationships 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 relationCawangan Jalan, Ibu Pejabat JKR, K.L

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. There are 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 discrepancy 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 Page 21

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can be overcome. JKR currently have a number of computer programs undergoing tests. Recent developments have found that the use of PHOENIX can produce reasonably practical estimation of modulus values. These values are sensitive to pavement layer thicknesses. A study carried out by TRRL found that the moduli estimations using back-calculation procedure by four pavement consultants were nearly similar. However, substantial differences in treatment recommendations and bituminous overlay thicknesses indicate 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 greater flexibility 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 methodology coupled with field verification is still in progress.

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, Research Report 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 :

2.6 REFERENCES PAVEMENT EVALUATION 1. AASHTO Guide for Design of Pavement Structures 1986, American Association of State Highway and Transportation Officials, Washington D. C. 2. SHELL PAVEMENT DESIGN MANUAL, Shell Petroleum Company Inc., London, 1978. 3. DAVID CRONEY, The Design and Cawangan Jalan, Ibu Pejabat JKR, K.L

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, pavement evaluation requires a different methodology and equipment. The scope of evaluation methodology is described in detail elsewhere. Page 22

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This chapter deals with pavement evaluation at project and detail level. The choice of equipment, information quality requirement, accuracy, methods of analysis and techniques used are given. The main steps of the evaluation can be summarized 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

task. This can be done visually or using a simple 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 failure. If it is structurally sound, its functional condition 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)

The above can be carried out efficiently by dividing the tasks into two assessment tiers, initial 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.

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 data collection along the road and provides a more confident representation of the pavement condition. It is necessary not to miss any weak areas at this level of testing. This testing will provide the base data for analysis and rehabilitation design.

3.1.1 Project initiation

3.1.4 Analysis and rehabilitation design

There are two normal mechanisms that initiate pavement evaluation at the project level :

The base data from the NDT tests together with other information that was taken previously is compiled 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 remedial measures and the procedure of choosing the appropriate method is described in para 3.3.3.

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 during the network level pavement survey. For accurate results, the time lapse between the evaluation exercise and the commencement of the rehabilitation construction must be minimised. 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 Cawangan Jalan, Ibu Pejabat JKR, K.L

3.1.5 Selection of remedial measures This can be the most important part of the evaluation 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 solution 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

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of the remedial measures may provide sufficient answers to the problem. The costing analysis should provide information 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 fulfills the engineering requirement.

The results from this initial assessment will be used to :

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.

Optimum and economical data collection and sampling can be carried out following the selection of the design sections. The final recommendation of rehabilitation measures should be adiusted to suit these individual sections.

3.1.7 Implementation Projected actual time of implementation of the evaluation proposal should be considered during 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 evaluation exercise. 3.2 INITIAL ASSESSMENT Pavement evaluation at project level starts by carrying out an initial assessment of the physical 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 comprehensive 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.

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i)

Decide preliminary lengths and loca tions of `design sections' ii) Plan for the frequency and interval of detailed tests

A minimum length of a selected design section should not be less than one kilometre to allow for efficient construction operation. Preliminary design sections are chosen first from the initial assessment results. At a later stage, other information such as soil type, topography, hydrology, deflection and traffic data can influence the final selection of the design sections. The engineer 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 difficult and 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 techniques, the extent of the failures can be classified and quantified. A standard surface condition survey method has been used in JKR. The main parameters recorded are cracking and rutting as well as shoulder and drainage conditions. Details of the information recorded is shown in Table 3.1. Visual assessment of cracks using a classification system simplified in Table 3.2 provide sufficient information for further analysis. It is easier to divide each section into short 10 metres block for accurate and efficient data collection. Alternative lengths of sections can be used. A straight edge and a wedge are used to Page 25

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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 initially assessed by visual judgement. A full assessment of the drainage condition can be made separately if necessary. This will be described in more detail in para. 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 common 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 requirements vary 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 of the pavement will contribute significantly to its performance. A classification of its condition will indicate whether this is the primary or contributory cause of damage to the pavement structure. Some existing road pavements have been upgraded from previous construction that may not have emphasised on drainage provision. Sometimes the drainage has disappeared through sequence of widening work. It is important to remedy drainage problems before any pavement rehabilitation work is implemented. Water is the most important environmental factor that influences pavement performance. 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 Cawangan Jalan, Ibu Pejabat JKR, K.L

expected. Surface drainage is judged by the ability of the pavement surface to drain water rapidly, not allowing water to pond either on the bituminous 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 difficult to assess. Past construction records will be helpful 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 observation whether a particular area requires subsoil drainage, side drains or interceptor drains or whether existing drains are sufficient and functioning properly to safeguard the pavement. Failure as a result of drainage deficiency would have been very obvious by the time the pavement undergoes investigation. Comparison to similar pavement construction on adjacent areas that have good drainage provision can assist on the judgement of the drainage condition. 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 homogeneity of key parameters within the sections.

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Crack Type

Crack Width

Crack Extent

-

-

1 - Single crack

< 1 mm

3 mm

>5m

> 3 mm and spalling

-

-

-

0 - No Cack

4 - Crocodile cracks 5 - Crocodile cracks and spalling

Table 3.2 Classification of cracks

Plate 3.1. Rut Depth Measurement

Plate 3.2. Surface Condition Survey Confidence level of 85%, Cawangan Jalan, Ibu Pejabat JKR, K.L

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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 quantified failures highly influence the proposed method of treatment. The primary mode of failure often dictates preliminary sectioning.

may effect the pavement performance. Drainage and ground water condition influence the performance and stability of cuttings. Drainage deficiency could provide further evidence to justify division into sections. Distinct differences in failure at different formation types indicates the suitability of sectioning by formation types. 3.3 DETAILED ASSESSMENT 3.3.1 General

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 the cracking 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 distribution. Information on pavement layer thickness 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.

The next stage in the evaluation process is the detail assessment of the road pavement. The assessment can be either the structural condition or the surface characteristics of the road pavement. In most project level assessments that lead to major rehabilitation, the structural condition assessment is vital. The surface functional requirement may not be critical since major reconstruction requires the existing surface 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.

Sectioning by rutting severity Severity of rutting can sometimes be used to assist preliminary sectioning. Areas with uniform 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 instability. 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 Cawangan Jalan, Ibu Pejabat JKR, K.L

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 conditions over a long stretch of road exists. This is a common situation along most roads in Malaysia. It is therefore more important to concentrate the evaluation effort in achieving accurate true mean characteristics of the materials from adequate sampling over the stretch concerned. Putting emphasis on achieving an accurate single sample characteristics could distort the overall scenario. NDT surveys for the structural assessment Page 29

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should be conducted at the time of the year when the pavement is at its weakest due to seasonal environmental condition. Relationships between environmental factors and deflections need to be established to know when the pavement will be at its weakest. For a start an assumption 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 40°C to reduce temperature correction error. Proper temperature 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 different 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 equipment to evaluate structural condition of pavement. 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 equipment and its usage is covered in para. 3.3.2 below. The background to the NDT approach of stnictural assessment was explained in Chapter 2. It Cawangan Jalan, Ibu Pejabat JKR, K.L

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 produced by each device and its approach. Preference in the choice of equipment will depend on speed of test, safety, cost of equipment, maintenance, reliability and case of use. Another factor that could be important is the authority's requirements and emphasis for specific 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. A moving test equipment (such as Deflectograph) could be preferred for such case. However, this type 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 decisions. It inav be necessary to carry out costbenefit analyses when choosing the most suitable NDT equipment for the pavement evaluation. 3.3.2 Choice of NDT devices Benkelman heam. This is the original NDT deflection device and was developed in the United States. The principle used by this device is to iueasure the maximum relative pavement surface deflection under a moving wheel load. Direct measurements using an aluninium beam and dial gauge are made (Figure 3.2). This equipment is included in this manual because it is accepted world-wide and had been use extensively over 30 Nears. JKR had used this equipment for the last 1 years. Because of its simplicity. the confidence in its results is higher than others. The portability of the equipment is also an added advantage. The latest version can be modified such that it measures the complete dellectionn bowl. Page 30

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There are two ways io measuring the ntaximturt dellection using the Benkelman Beam. namely the 'rebound' and the 'transient' method. The transient method is recommended. Maximum deflection is measured on the nearside wheeltrack. Temperature, rut depth measurement and visual inspection is also carried out simultaneously. The deflection is then corrected to a standard temperature of 40°C. Deflection tests should be carried out at regular intervals. 20 to 50 metre intervals can be chosen. The deflection values at those intervals can then be plotted along the test chainages to check the deflection profile. Simple stastistical calculations can be used to find a representative deflection over a selected section. This deflection value is then compared to a prerecorded deflection history of similar pavements in similar environments. The residual life of the pavement can then be predicted and the required surfacing overlay thickness can also be determined. The use of Benkelman Beam is recommended in places where expensive equipment cannot be justified such as small rehabilitation projects. Where traffic is light the deflection beam can also be used to assess in-situ pavement strength. However, it may not be suitable for testing on a busy road. Some fatal accidents involving the beam operators have occurred when using the Benkelman Beam on such roads in Malaysia. This is the main reason for JKR preference for other deflection devices. The cost of a Benkelman Beam ranges from RM10,000-00 to RM50,000-00. A loaded lorry is needed which add to another RM50,000-00 to RM10O,00O-00 for a complete and operational equipment cost. Maintenance cost is low depending mostly on the lorry efficiency. In full operation, 1 skilled staff and 3 unskilled staff are required. Minimum of 2 more unskilled staff is needed to control traffic. Dynamic Cone penetrometer (DCP)

asphalt layer is required. Therefore in principle, the test could be considered as destructive. However, it can be accepted as an NDT since the damage caused by coring is minimal. The DCP can be used to establish : i)

the strength of the granular pavement layers ii) pavement layer thickness The DCP is a penetrometer, suitable for road pavements with unbound granular bases. A steel rod with a 60° cone is driven through the unbound pavement layers by using a steel hammer applied at constant force (Figure 3.3). The rate of penetration is inversely proportional to the strength of the material. The relationship between the rate of penetration and CBR enables the strength of granular pavement to be determined. A complete set of DCP costs between RM1,00000 to RM3,000-00. Maintenance cost is low. Only the cone needs frequent replacement. A coring machine and a light truck are needed if testing is done on existing asphalt pavement. The cost of a fully operational equipment costs ranges between RM50,000-00 to RM70,000-00. In a typical 8 hours day work on asphalt pavement more then 10 points can be carried out. Cost of testing per point is estimated between RM50-00 to RM150-00. Road Rater The Road Rater is a vibratory NDT device (Plate 3.3). A steady state harmonic vibration is applied to the road pavement by a dynamic force generator through a circular loading plate. The frequency of the force function remains constant with depth. A static pre-load is applied to the pavement to provide a reaction during the vibratory phase. The transient deflections are measured during the steady-state loading phase.

Before a DCP test is carried out coring of the Cawangan Jalan, Ibu Pejabat JKR, K.L

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Figure 3.2 Schematics Of A Typical Benkelman Beam

Figure 3.3 Schematics Of The Dynamic Cine Penetrometer

Four velocity transducers are placed at the centre of the circular loading plate, and at offset distances of 300, 600 and 900 millimetres. An analogue computer is used to convert the output of the velocity transducers into deflections using a measuring technique normally referred as inertial system. This measuring system does Cawangan Jalan, Ibu Pejabat JKR, K.L

not require an external reference point for the measurement of deflection that is needed for FWD or Benkelman beam (Figure 3.4). The Road Rater produces a steady state harmonic loading and a static preload. It induces a stiffened response of the pavement subgrade Page 32

Interim Guide To Evaluation And Rehabilitation Of Flexible Road Pavements.

FOR INTERNAL USE ONLY

Plate 3.3. The Road Rater

system and can possibly overestimate its true strength. Allowance for this can be made with engineering judgement and field experience in using the device. Previous direct use of the Road Rater has shown correct results where the deficient aspects of the pavement has been accurately identified and repaired. The Road Rater deflections and the FWD deflection are highly correlated. For this reason and for the purpose of standardising procedures it is recommended to convert the Road Rater deflection into an equivalent FWD deflection which is then used for the evaluation analysis. The relationship to convert the Road Rater deflection values is : FWD = 0.0246 + 6.87 Road Rater At the time of writing, the Road Rater is not widely manufactured and has become less popular as compared to the FWD. Moreover it is cheaper and faster than most FWDs and has the advantage of low operation cost. Similar to the FWD it must stop when taking measurements. Therefore adequate traffic control must be provided during testing for maximum safety.

Cawangan Jalan, Ibu Pejabat JKR, K.L

Falling Weight Deflectometer The FWD uses an impulse loading system. A transient force is delivered to the pavement surfaces. The transient pavement response is recorded electronically. The force is applied by a mass falling on a circular plate that is connected to a baseplate by a set of rubber springs. There are three ways of changing the force amplitude : i). Changing the mass ii). Changing the drop height iii). Changing the spring constant (a linear spring constant is assumed) The force amplitude is measured by a load cell placed at the baseplated sandwiched between two steel plates. The transient deflection is measured by geophones. A geophone has an internal mass that moves relative to the casing. The mass velocity generates an output signal that is integrated to obtain a deflection. One geophone is normally placed at the centre of the loading plate. The other offset geophones can be adjusted according to one's own preferences or the manufactur Page 33

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Plate 3.4. The Falling Weight Deflectometer

er specifications (Fir ure 3.5).

porating suitable allowance factors.

The pavement deflection induced by the FWD is typical of that produced by a single heavy vehicle which passed through a point on the pavement surface. However. this fact must not be confused with the final requirement of the testing that the device must indicate accurate condition of the existing material. It is not necessary that accurate simulation of actual vehicle provide accurate indication of materials condition.

Heavy Weight Deflectometer

The results from the FWD are used to estimate the pavement layer moduli. The estimated modulus values may indicate the current condition of the pavement materials.

The HWD spans a loading range of 30 - 240 kN, thus covering the half-axle load imposed by a moderately heavy truck upwards through the single wheel load of a loaded BOEING 747 aircraft.

Bituminous overlay can be design from these estimated parameters. Various approaches using the FWD deflection readings have been developed to design bituminous overlays. None of these has been verified in the field or supported with sufficient laboratory test for confident use in the Malaysian environment. However, extensive work by SHELL laboratories have presented a more convincing approach in the analysis which was supported by extensive laboratory testings. Other researchers have carried out field tests to verify the approach. The result shows that reasonable estimates of the fatigue life of asphalt can be obtained from the SHELL fatigue curves incor Cawangan Jalan, Ibu Pejabat JKR, K.L

The principle behind this model is similar to that of the FWD except that it has been specifically designed to fully meet the needs of both highway and airfield pavement deflection testing, up to and including the effect of very heavy aircraft loads. This model is called the Heavy Weight Deflectometer (HWD) (Plate 3.5).

HWD generalised data, combined with other related parameters can be used in structural analysis to determine such informations as the bearing capacity of a pavement. Availability of equipment in Malaysia. The equipment described above is available at the Pavement Unit, Research Centre, Public Works Institute Malaysia (IKRAM). The Institute is currently undertaking pavement research and evaluation prgjects. There are 2 sets of Benkelman Beams, 3 units of Road Raters, six sets of the DCP and 3 units of the Page 34

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FOR INTERNAL USE ONLY

Plate 3.5. Heavy Weight Deflectometer

Figure 3.4. Schematics of the Road Rater

light weight Falling Weight Deflectometer. A heavy duty version of the FWD is also available for further research and the evaluation of airport pavements. A Benkelman Beam test costs ranges between RMIO-00 to RM40-00 per test point. Road Rater testing costs between RM30-00 to RM5000 per point for an estimated 300 points per day work. The FWD testing costs normally Cawangan Jalan, Ibu Pejabat JKR, K.L

range between RM30-00 to RM80-00 per test point and is capable of covering an estimated 250 points daily in a normal 8 hours working day. Comparatively the FWD is the more costly to operate and maintain. However, it is gaining popularity world-wide with the growing interest in using the mechanistic engineering approach of pavement analysis.

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FWD, Road Rater or Benkelman Beam maximum deflection readings.

3.3.3 Choices of NDT analysis technique An interim evaluation method using the Falling Weight Deflectometer or Road Rater and the DCP is given below. The mechanistic or empirical approaches will bo improved by further research. It is anticipated that changes to this methodology will be necessary in due course when comprehensive field test results are available. Empirical structural assessment using the

Deflection-life relationship can be developed from field experiments and historical measurements. The observations and measurements of all failure manifestations take into account all the failure modes by default. Terminal conditions can be chosen that balance both users' and engineers' requirement. It can also follow exactly the basic concept of overlaying; that it is only applicable for non fractured or seriously deformed road conditions.

The temperature is taken at 40 mm depth below the riding surface. Deflections obtained from Benkelman Beam and the Road Rater requires conversion of their maximum deflection to standard deflection.

Long term monitoring of pavement overlays in JKR roads has successfully resulted in the development of a deflection based performance prediction. Several design curves have been developed by IKRAM. The curves depict real field situation of current material and construc tion standard of asphaltic concrete overlays throughout the country. Terminal condition is defined as crack type 2. Pavement with cracking more serious than this is deemed unsuitable for resurfacing. These areas can easily be identified from the surface condition survey.

Standard deflection had been used as a basis of pavement performance prediction. Pavements with similar deflection levels and application of repetitive axle loading will reach terminal condition at the same time. High deflections indi cate weak pavements whilst low deflections indicate strong pavements.

The reduction in deflection before and after overlay indicate the improvement of strength if asphaltic concrete or similar overlay is used. The required strengtening overlay for the expected design traffic can be derive from the relationship as shown in Figure 3.6. The steps to be adopted for this approach are :

Standard deflection refers to FWD central deflection at the verge-side (near-side) wheelpath under 700 kPa pressure on a 150 mm radius plate at 40°C pavement temperature.

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Step 1. Deflection survey Deflection measurement is first carried out in the field using the FWD, Benkelman Beam or the Road Rater. The reading must be reduced to the standard deflection values. The frequency and interval of tests may depend on the preliminary sections. Deflection measurements should not be restricted to specific testing intervals. Simple checks on the variability of the deflections should be made by comparing groups of ten consecutive values. The maximum and minimum values in the group should not differ from the mean by one-third of the mean. This procedure may reveal all possible weak and highly variable areas. More tests may be needed at highly variable areas.

structural adequacy of the pavement respective to terminal failure conditions. The pavement is suitable for application of bituminous overlay if it nearly reaches its end of life. Other methods of treatment should be selected if the pavement has significantly past its life (Chapter 5 . Summary. The simple approach of this method had made it practical and simple for use by engineers. Historical observations ascertain all failure modes are included for better and more realistic prediction of performance. The accuracy of the results largely dependent on the accuracy of the historical data, the deflection measurements and the estimates of traffic loading.

Step 2. Sectioning

Examples

The road can be divided into representative sections with respect to the deflection levels and checked with the preliminary sections. The standard deflection data is plotted against the chainage. Confidence level at 85% is normally used to select representative mean deflection values within a selected section. Mean deflections from adjacent sections must not be significantly similar at 95% confidence level or else they have to be merge to make up a longer section.

The road between Muar to Tangkak with a connection to the North South Expressway is to be upgraded. The last rehabilitation exercise was carried out five years ago. Surface condition survey was carried out during an initial visit to the site. The results of cracking and rutting survey was plotted as shown in Figures 3.7.

Step 3. Traffic estimates Past traffic information provides estimates of the number of axle loadings that have traversed the pavement since the last major rehabilitation exercise. This requires a review of past traffic data collected by the Highway Planning Unit (HPU), Ministry of Works. Traffic survey records dates to more than 10 years back and is sufficient to estimate accurate past traffic loading. Estimates of the load equivalency factor can be made using procedures described in Chapter 4.

Preliminary sections were selected from the above results. The survey was done at the right time depicted by the level of rutting and cracking. Cracking is more prominant than rutting. It is expected that an application of a suitable thickness of bituminous overlay is a reasonable solution provided pre-treatment is carried out in areas which have localised failure. Traffic is similar throughout the length of the road since there are no major intersections in between. Traffic loading estimations have been explained in Chapter 4. Traffic would not influence the earlier selected sections. Deflection survey was carried out at 50 and 100 metres intervals depending on the condition of the pavements.

Step 4. Estimate residual pavement life Estimate the pavement residual life from the deflection life curve. The residual lives define Cawangan Jalan, Ibu Pejabat JKR, K.L

Inspection and statistical analysis of the deflection data normally result in a revision of the preliminary sections. The representative deflecPage 37

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tion is estimated over a section by statistical calculation. The required overlay thickness can be design for each section from this deflection value.

the interpretation with respect to the other shortcomings of the mechanistic model desribed earlier. An interim condition criterion is given in Table 3.3.

Mechanistic structural assessment using the Falling Weight Deflectometer or the Road Rater

The stresses and strains in the pavement layers can also be calculated. The tensile stress below the surfacing and the compressive stress on the subgrade are the two critical stresses normally consider. The calculated stresses in the analysis are compared to their respective allowable stresses pre-determined in the laboratory to estimate their residual life. The material with the lowest residual life is normally assumed to represent the residual life of the pavement. This calculation also requires traffic loading information that provides an estimate of the number of repeated axle loading.

The deflection readings at the various offsets when plotted, produced a bowl shape diagram shown in Figures 3.8, normally termed as the deflection bowl. This response from the loading system is the basis of a theoretical approach that leads to the estimation of pavement layer moduli and residual life described earlier in Chapter 2. The materials characteristics, such as the moduli of each layer, Poisson ratios, layer thicknesses are first estimated. A deflection bowl is predicted using the multi-layer elastic theory. The predicted deflection bowl is compared to the actual deflection bowl measured by the FWD. When they are equal or within a predetermined identical range, the layer moduli satisfying this condition is taken as the estimated moduli of the layer. These modulus values can be used to estimate the condition of the materials in the pavement. The ratio of moduli of different layers in the pavement (modular ratio) may also be used to interpret its condition. The moduli values can be translated to CBR using a relationship given by :

In summary, the steps involved in determining the moduli are as follows : i)

ii)

iii)

iv) v) vi)

CBR = E/10 ...... (after SHELL International) Where, CBR = California Bearing Ratio E = Modulus of material The modulus of asphalt surfacing may vary from as low as 500 MN/mm- to more than 10,000 MN/mm-. For the Federal Route Network it may be assumed that asphalt modulus greater than 3500 MN/mm- is sound. Easier and clearer interpretation can be made if there are available relationship between modulus of asphalt against traffic damage. Research work by IKRAM is currently studying this aspect of Cawangan Jalan, Ibu Pejabat JKR, K.L

Input parameters are measured deflec tions, layer thicknesses and loading characteristics and geophone arrange ments Estimate the moduli of surfacing (El), base (E2) and sub-base (E3) and the sub-grade. Transform the layers to equivalent homogeneous structures using the Method of Equivalent Thickness (MET) Calculate a set of deflections. Compare computed and measured deflections. If the differences in deflections are less than + 5 %, then the moduli values can be accepted, otherwise repeat iteration from step 4 onwards.

Many computer programs are available in dealing with the above computation. Currently there are more than 10 available packages. These programs need proper evaluation and verification for correct use and interpretation. It is important to bear in mind that the programmes demand full understanding of its input and output procedure. Most importantly, its approach must be correct for local environ

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Figure 3.6. Reduction in deflection after overlay

Figure 3.7. Distribution of cracking and rutting

ment and its limitations are clearly outlined. JKR is currently using the PHOENIX program that was purchased with the FWD and is fully documented. This program was design complete with moduli estimation, residual life prediction and overlay design. The output modulus values was found to be reasonable and practical for pavements in Malaysia. Further development and verification of the program are in progress. Areas related to local temperature, moisture,

Cawangan Jalan, Ibu Pejabat JKR, K.L

loading and actual field conditions are covered. At IKRAM, specific focus is given on the development of a cornputer package called SERF (System for Evaluation and Rehabilitation of Flexible Pavements) using local performance models. These models are derived from research at IKRAM and are verified against established computer packages. This package has two main modules on evaluation and rehabilitation. The evaluation module is currently in use while the rehabilitation module is being designed to incorporate the expert system.

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Figure 3.8. Deflection bowl and material characterisation

Pavement Layer Subgrade

Sub-base

Gramular Base

Bituminous Surfacing

Strength Indication

Rating

CBR < 5% (50MN/m2) 5 - 10 % > 10 % (100 MN/m2) Modular ratio (E3/Esg) < 1.5 1.5 - 2.0 > 2.0 Modular ratio (E2/Esg) < 1.5 1.5 - 2.0 > 2.0 Modular value (MN/m2) < 1500 1500 - 2500 2500 - 3500 > 3500

Poor Satisfactory Sound

Estomated Structural Coeffecient 0.10 0.20 0.23

Poor Satisfactory Sound

0.23 0.30 0.32

Poor Satisfactory Sound

0.25 0.30 0.32

Very poor Poor Satisfactory Sound

0.60 0.70 0.85 0.95

Table 3.3. Material condition interpretation

The PHOENIX program produces estimated modulus values of each pavement layer and suggests an overlay thickness. A reasonable and practical overlay thickness can be obtained by this method. However, it is still not certain whether the overlays can achieve the design life when age hardening effect govern the performance. There are lack of fatigue studies of Malaysian pavement materials that closely

Cawangan Jalan, Ibu Pejabat JKR, K.L

simulate field behaviour. This is a subject of further research at IKRAM on the application of the multi-layer model. There are several precautionary measures to be taken when using the multi-layer elastic theory to estimate pavement residual life. This theory can be used to estimate the dynamic behaviour of relatively stiff pavement. However, deviations occur under high temperature conditions Page 40

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where it is difficult to establish an effective modulus for biturninous materials and for pavements that derive a large part of their structural stiffness from granular materials (2). Non-linear behaviour of pavement material is an added problem (3). The limitation of using multi-layer theory must be rnade clear and the engineer must not rely exclusively on results from the analysis alone. Reasonable results are achievable if four major areas listed below are covered and supported with adequate laboratory or field testings : i)

Laboratory fatigue testing on various type of materials ii) Major evidence of failure indicated by traditional fatigue failure iii) Temperature effect on modulus values can be adjusted according to local con ditions iv) Field verification of fatigue perform ance.

The first three areas are covered in the SHELL method. Accelerated field fatigue testing has been carried out elsewhere. The results suggest a factor of 10 or 20 is used when using the SHELL fatigue curves for estimating residual pavement life (4). However, there is evidence that age hardening may dominate actual field behaviour in hot climate (5). If these modes of failure are dominant the isotropicity and homogeneity of bituminous materials will slowly cease to exist thus distorting the multi-layer model. Cracked pavements also alter the above conditions. Application of the multi-layer theory to estimate residual life under this condition may deviate frorn the original assumptions and must be treated with caution. These problems are now under study at IKRAM. At present, the PHOENIX program is considered applicable but it should be supported by adequate engineering judgement. Structural assessment using the DCP The DCP is portable and lightweight and can be operated easily. It is a penetration test equipment that directly measures the ability of the material to resists penetration thus indirectly Cawangan Jalan, Ibu Pejabat JKR, K.L

indicating its strength. Detailed methods of operating the DCP are given in a Guideline being prepared by IKRAM. The penetration resistance is measured in millimetres per blow (DCP number). The DCP number is often correlated to other established strength parameters commonly used in pavement engineering. Such parameters are the CBR values, structural number and unconfined compressive strength. It is necessary to calibrate the parameters to the DCP number for local condition. DCP Number relationship with in-situ CBR had been established for use in Malaysia. The following relationship was developed for quick estimate of the CBR at each layer :CBR = 269/DCP This estimate is limited for subgrade strength between 5 to 100 % CBR (6, 7, 8). Research in developing specific a DCP evaluation methodology for local use is still in progress. In this guide, the approach using the structural number to evaluate structural strength is considered. The procedures outlined below make use of the current Arahan Teknik (Jalan) on pavement design which uses a similar technique. The steps are : Step l. The road stretch is first divided into uniform sections determined by the visual survey results from the initial assessment. The test locations and intervals should be representative of the sections. Step 2. DCP tests are carried out on the near-side wheel track. The frequency of tests depends on the length of sections and the uniformity of the pavement. A typical DCP test result and DCP plot is shown in Figure 3.9 and 3.10. A summary plot of the results will show the variability of the pavement thickness and estimated strength. Similar simple variability check procedure can be used as described earlier in para. 3.3.3.

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Laboratory test need to be carried out on the asphalt layer. A 100 mm size core is normally extracted at the verge-side wheel-path. The asphalt core can be tested to estimate its existing structural coefficient. Resilient modulus test, if available, is recommended to estimate structural coefficients. The condition of the core sample can also be used to estimate the layer coefficient. This coefficient can be used to calculate the structural number of the pavement (Table 3.4 . If the above method is used, it is best to include an estimate or a measure of the void content in the mix. High void content may reduce the

Structural Coefficient

Condition 1. Sound, stable, uncracked. Little deformation in the wheel path. 2. Crack type 1 and < 5mm rutting. 3. Crack type 2 - 3, 5 -10 mm rutting 4. Crack type 4 or greater, > 10 mm rutting.

0.6 0.7 0.5 0.4

Table 3.4. Estimated values of structural coefficients for various conditions of asphalt

Step 4. Estimate the existing layer thicknesses and the respective CBR values. The procedures given in the IKRAM DCP guideline, includes methods of determining the layer thicknesses and CBR values. A uniform section consists of significantly similar layer thicknesses. If the layer thicknesses are significantly different, the sectioning may be adjusted. Pavement layer thicknesses are normally critical in selecting the remedial measures.

Estimated of structural coefficients

CBR Sub-base > 30 % 20 - 30 % < 20 % Road-base > 100 % 80 - 100 % < 80 %

0.3 0.2 0.1 0.32 0.30 0.25

Table 3.5. Estimates of strictural coefficients, based on DPC in-situ CBR values.

ROUTE NUMBER : 1 SECTION NUMBER : 238 DIRECTION : UP No. No Blows

(sum) Blow

Pen. Pen ( mm )

DATE : 1/1/1993 METREAGE : 50 CORE THICKNESS : 120 mm No. No Blows

(sum) Blow

Pen. Pen ( mm )

No. No Blows 10

(sum) Blow 180

Pen. Pen ( mm ) 420

0

0

0

10

90

180

10

10

20

10

100

190

5

185

443

10

20

50

10

110

200

2

187

486

10

30

90

20

130

220

2

189

525

10

40

90

10

140

250

1

190

590

10

50

105

5

145

280

1

191

643

10

60

120

5

150

320

1

192

695

10

70

140

10

160

350

1

193

748

10

80

160

10

170

380

1

194

800

Step 3. Cawangan Jalan, Ibu Pejabat JKR, K.L

Figure 3.9. DPC test results Page 42

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Figure 3.10. Typical plot of the DPC results Step 5. Estimate the base and sub-base structural coefficient based on the in-situ CBR values from the DCP test. Their in-situ CBR obtained is indicative of the structural coefficient of the base and sub-base layers. Available estimates are based on overseas research. Verification of the values suiting localmaterial is in progress. The estimate can be made using Table 3.5. Step 6. Calculate the existing pavement structural number. The structural number of the existing pavement can be found by using structural number equation as follows : SN = h I x C I + h2 x C2 + h3 x C3 Where hl, h2 and 10 are the thicknesses of the asphalt, base and sub-base respectively. Cl, C2, and C3 are their respective structural layer coefficient. Step 7.

pavement will experience within the design period. The CBR values from the DCP tests can be used as a basis of selection. Step 9. Estimate the required structural number and overlay thickness using the design chart in Arahan Teknik (Jalan) on pavement design. The required structural number should be higher than the existing pavement structural number. The difference is converted to asphalt layer thickness taking" structural coefficient of asphalt as 1.0. The accuracy of this approach relies very much on the accuracy of the structural number concept and estimation of the structural coefficient of each material. Field testing of the material has an advantage of determining actual condition of each layer. A low CBR values indicates a weak layer. This evidence provide valuable clues in determining the deficiency and failure causes of the pavement.

Calculate the desired design traffic level. The design traffic loadings for the required design period should follow the examples given in Chapter 4.

3.3.4 Test interval, variability and accuracy level for structural assessment

Step 8. Estimate the design subgrade CBR that is expected to represent the worst condition the

The frequency and accuracy level needed for this assessment is primarily based on the results from the initial assessment. Poorly deteriorated pavements may require closer intervals of data collection compared to a sparsely deteriorated

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pavement. The final selection of sampling frequency depends also on the uniformity of failure conditions. Less samples need be taken from a more uniformly failed pavement. Sampling interval of 10 to 100 metres are normally selected. Each preliminary section requires a uniform interval of testing. A variation in sampling interval allows more data collection at uncertain areas with dominant failure manifestations. Simple variability checks described earlier allows variation of test frequency. The engineers need to employ suitable statistical technique to analyse the data and make useful interpretation of the information. The selected testing interval will determine the sample sizes that should be sufficient to produce at unbiased estimate of the population mean of parameters under study. Extravagant tests frequencies could result in wasted expensive deflection or other NDT testings. Useful basic statistical calculation such as mean, standard deviation, variance and range improve interpretation of each parameter along the road under study. The accuracy of the structural assessment depends on the engineers experience in handling and interpreting available data. Each length of road under study may have unique problems. The variable standards of previous construction method could pose further difficulties. The choice of assessment approach must be made with due regards to these problems.

3.3.5 Surface evaluation General Pavements without structural deficiency or do not need crack sealing require only surface evaluation. Slipperiness of the surface is the guiding criteria for road surface evaluation. The road surface can be assessed by testing two attributes of the surfacing that relates to slipperiness : i) The wet skidding resistance ii) The surface texture The micro-textures of the surfacing contribute largely for skidding resistance at low speed. Both the micro and macro texture are relevant for high speed skid resistance, but the role of rnacro texture is critical under wet conditions. Figure 3.11 shows the micro and macro-texture. To date, the skid resistance of a road surface can be assessed by using the Pendulum Skid Resistance Tester (PSRT) developed by TRRL (8) (Plate 3.6 . The tester yields Skid resistance values (SRV) standardised at 35°C for local inservice pavement condition. This value simulates the wet tyre resistance of a vehicle travelling at 50 kph. The other device that is available to meet this need is the Griptester (Plate 3.7 Studies in U.K. have shown that the Griptester could produce accurate results if used correctly. However, it has limitations in accuracy of testing at difficult road geometries (9). Surface texture

Figure 3.11 Micro and macro-texture

Cawangan Jalan, Ibu Pejabat JKR, K.L

It is important for the engineer to know that skid resistance is critical not only for low speed driving but also for high speed driving. Surface texture of the surfacing plays a more important role for high speed driving under wet conditions. Adequate surface texture is needed to provide channels for the bulk water trapped between the road surface and tyre to drain quickly to reinstate contact between the tyre and road surface. If this is not achieved a phe Page 44

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Plate 3.6 Pendulum Skid Resistance Tester nomenon called aquaplaning is highly likely to occur and will cause skidding. There is at present no mandatory minimum surface texture requirement for new or in-service road surfacings in Malaysia. A review of the subject is being undertaken by IKRAM whereby an interim specification will be prepared. Surface texture can be measured conventionally using the Sand Patch method (Plate 3.8 or the more advanced TRRL Minitexture meter (Plate 2.9). The sand patch is cheaper, easily available and simple to use. The texture measurements define indirectly the probability of the removal of bulk water trapped between the tyres for safe high speed driving under wet condition. There are circumstance where the water film thickness under the Malaysian condition can reach a level where even the best surface texture will still be flooded with water. Heavy rainfall would normally lead to this phenomenon. Direct skidding test simulating this condition at high speed may be required. The Friction Tester is an example of such equipment that can measure skid resistance under such conditions (Plate Figure 3.11 Micro and macro-texture Skid resistance 3.10). IKRAM will be equiped with this equipment in the near future which can measure the Cawangan Jalan, Ibu Pejabat JKR, K.L

slipperiness of both highways and airport runways (10). 3.3.6 Other key factors to consider during pavement evaluation Moisture variation; drainage and shoulder, rainfall intensity, seasonal variation Pavement cross section should be design to eliminate water from entering the component pavement layers at any time. In Malaysia, new road pavement would normally have these features. However, for old pavement, this seldom happens and consideration of moisture variation in the pavement layers during the evaluation period should be noted. Seasonal variation plays a major part in the estimation and prediction of performance. Investigation measurements have to be corrected for seasonal variations. Environmental effects; rainfall, temperature, humidity The main environmental elements perculiar to each country that can affect pavement performance are temperature, rainfall and humidity. Bituminous material is known to be sensitive to temperature and other environmental factors. Most laboratory standards of testing for this material are at 25°C depicting moderate service Page 45

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Plate 3.7 The Griptester

Plate 3.8 Sand Patch Test

Plate 3.9 TRRL Minitexture Meter Cawangan Jalan, Ibu Pejabat JKR, K.L

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Plate 3.10 The Friction Tester

temperature conditions. This should have been 35°C or 40°C that realistically depicts local conditions. Research findings by TRRL have shown that there is a significant increase in the rate of pavement deterioration during the summer period. However there is insufficient recorded experience in field performance prediction above 35°C, covering the Malaysian range of pavement service temperature. With this difficulty in hand the use of the simplified approach must be carefully reviewed with experience in the field. The average yearly rainfall in Malaysia is 2000 millimetres, higher than any other country known to have full research in pavement performance. Within the country itself there are differences in rainfall intensity. Hilly areas and the eastern region of the country are known to have high rainfall especially in the monsoon. Due recognition of this must be made. Accelerated deterioration of the surfacing in these areas can be expected with the presence of more water. The rate of change of deterioration is also expected to be faster especially those related to cracking. Little is known of the effect of humidity on pavement performance. However it is predicted that the effect of heavy rainfall and temperature are more to performance rather than humidity. Ultra Violet (UV) radiation is an additional factor contributing to pavement deterioration. UV radiation is thought to accelerate the rate of Cawangan Jalan, Ibu Pejabat JKR, K.L

bitumen hardening at the surface. Research is still in progress to understand and quantify its role. However, at this juncture the combined effect of environment in relation to ageing is the best and most practical to consider. Hardening by oxidation plays a more critical role in the ageing process. 3.3.7 Detailed Material Investigation General Direct material assessment is only necessary if the non-destructive approaches fail to provide sufficient information that confidently guides treatment selection. This scope of works falls under the category of detail material investigation that usually arise from premature pavement failures or very serious failures. The usual approach to this is to dig a test pit in the pavement at selected locations determined from results of the initial assessment. The materials are sampled for laboratory testing. Insitu tests that could indicate actual material condition on site can also be carried out. The JKR Standard Specifications for pavement material govern the suitability criteria of existing material. Detailed requirements of material standard should also follow this specification. Surfacing The strength and weakness of bituminous surPage 47

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Interim Guide To Evaluation And Rehabilitation Of Flexible Road Pavements.

facing are its behaviour sensitivity with temperature. The bitumen used in the mix is the main controlling factor that determine the properties of the mix. The primary functions of the bitumen are : i) ii) iii) iv)

Binding agent Waterproofing Stable Durability and oxidation resistance

The condition of the existing mix may indicate deficiency of some of the above requirements. Bitumen penetration grade 80/100 is normally specified for use in JKR road pavements. Laboratory tests can be carried out to investigate the condition of the bitumen in the existing mix. The viscosity and the penetration value of the bitumen can provide sufficient information on the condition of existing asphalt. Apart from bitumen, the aggregates used in the surfacing mix should be sufficiently strong to withstand traffic loading and construction operations. It should also have adequate polishing resistance. Requirements of the Standard Specifications should be met. In summary, the key information related to the surfacing that may be required during evaluation are: -

spreading the traffic load. It must be strong and sufficiently thick. Unbound crushed stone, drybound macadam and wet-bound macadam have been the major types of granular road base materials used in Malaysia. The specifications and requirements for strength have been described fully in the standard specifications. The thickness of the road-base layer is the most important information that must be known in pavernent evaluation. It is mandatory if a mechanistic analysis is used. Granite and limestone has been the major type of aggregates used for road construction in Malaysia. There has been no experimental evidence stating the better types for use as a roadbase. Compliance to the requirements laid down in the Standard Specifications is sufficient to judge the suitability of the material. During the evaluation, investigation of the density and aggregate grading of the material may be sufficient to check the quality of the roadbase material used. In-situ density test can be carried out to measure the field density of the road base layer. Adequate samples should be taken for laboratory CBR test to check the material properties. DCP tests provide a simpler and cheaper alternative to estimate the in-situ bearing capacity of the road-base. Sub-hase

i) ii) iii) iv) v)

Type and composition of mix Thicknesses of each layer Properties and percentage of bitumen Temperature adjustment conditions Fatigue or deformation relationship with repeated loading vi) Hardening characteristics of the mix vii) Aggregate grading, properties and pol ishing resistance

The condition of the existing pavement and the choice of evaluation techniques govern the necessity of the above information. Road base The primary function of the road base is for Cawangan Jalan, Ibu Pejabat JKR, K.L

As a secondary load-spreading layer, thickness is important, apart from other requirements given in the standard specifications. In-situ CBR Of the sub-base can provide an accurate indication of its existing strength. Laboratory tests could indicate its properties and suitability as a sub-base material. DCP tests can also be used to estimate the bearing capacity of the sub base layer. Subgrade The subgrade material that mainly consists of compacted soil is best studied using conventional soil testing procedures. In-situ tests such as density determination, CBR and the DCP Page 48

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test may not be sufficient to asses the quality of the soil. Laboratory compaction test, moisture content, soil classification and CBR provide a clearer indication of the soil compliance to requirements in the Standard Specification. Samples for moisture determination can be taken at various depths below the formation level to check for the existence of any moisture gradient. Bulk samples can be taken for laboratory tests. The testing procedure and the quality requirements are stated in the JKR Standard Specifications. In-situ measurements hi-situ density of the soil indicates the field condition of the compacted soil. The field density can be compared to the maximum density achieved in the laboratory. Poorly compacted soil can be found by this method. Soil density measurement by the sand replacement method is normally used.

neering judgement is required before digging a trial pit which is normally not recommended. Localised reconstruction area could be identified from experience and historical evidence. Rutting and cracking intensities are best used as a guiding criteria. This will be explained further in Chapter 5. 3.4 REFERENCES 1. M.S HOFFMAN, M.R THOMPSON. Mechanistic interpretation of nondestructive pavement testing deflections. Transportation Engineering Series No. 32. Illinois Cooperative Highway and Transportation. Illinois 1982. 2. N.W LISTER, The transient and long term performance of pavements in relation to temperature, Proceeding of the 3rd Int. Conference on the Structural Design of Asphalt Pavements, Vol. 1, London, 1972.

In-situ CBR is slow an expensive. The DCP can be used to measure the penetration resistance of the subgrade. The CBR values can be estimated using established DCP in-situ/CBR relationship.

3. OVERSEAS UNIT. Deflection mesurements and road strengthening. Department of Transport, Overseas Unit Information Note. Crowthorne 1986. (Overseas Unit TRRL)

Laboratory measurements

4. G.WJAMESON, K.G.SHARP, N.J. VERTESY, R. YEO. The fatigue perform ance of asphalt and cement treated crushed rock under accelerated loading. Proceedin,, 16th ARRB Conference, (Part 2). Australia 1992.

Undisturbed samples can be taken to the laboratory for density tests or the CBR tests. Disturbed sample should undergo compaction and the CBR test for better representation of the soil condition. Determination of the Atterberg's limit will further reveal the true properties of the existing soil. These properties will indicate the current condition of the soil. Selection of appropriate remedial action should consider the condition of the existing soils. Full reconstruction normally requires justification to proof that existing soil is unacceptable and needs replacement.

5. HASNUR I. The Deterioration of Bituminous Binders. M. Phil Thesis, University of Birmingham. 1990. 6. SABRI M., ZAIN A., SHAFII M. Quick in-situ CBR for Road engineering from Insitu-CBR/DCP relationship developed in Malaysia. Proceeding 6th REAAA Conference, Kuala Lumpur 1990.

Summary Detailed material investigation is only necessary when NDT has failed to provide answers to remedy the ailing pavement. Sufficient engiCawangan Jalan, Ibu Pejabat JKR, K.L

7. FAUZI A, SHABRI S, DCP/CBR Relationship for soft soils in Malaysia. Proceeding, 7th REAAA Conference, Singapore 1992. Page 49

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Interim Guide To Evaluation And Rehabilitation Of Flexible Road Pavements.

8. ROAD RESEARCH LABORATORY. Instructions for using the portable skid resistance tester. Ministry of Transport, Road Research Laboratory, Road Note 27, London 1969 (H.M.S.O). 9. SABRI M. Skid Resistance and Surface Texture of Wearing Courses. MSc. Thesis, University of Birmingham 1991 (unpublished). 10. SAAB Friction Tester, Workshop Manual. SAAB Car Division. S-61181 Nykoping. 1993. BIBLIOGRAPHY 1. DAVID CRONEY, The Design and Performance of Road Pavements, Department of Environment, Department of Transport, Transport and Road Research Laboratory. HMSO, London 1977. 2. YODER E.J., WITCZAK M.W. Principles of Pavement Design. 1975. 3. THE SIIEL1, BITUMEN HANDBOOK, Shell Bitumen U.K.1990. CHAPTER 4 : TRAFFIC LOADING ASSESSMENT 4.1 GENERAL The assessment of pavement performance and maintenance needs requires the use of traffic information. Pavement behaviour and performance are dependent on repeated axle loadings that can be derived from traffic and axle load information. It is most desirable to have both current and historical traffic data. This manual covers structural and surface evaluation aspects, therefore the main focus will be given to heavy vehicle traffic. The magnitude and number of individual wheel load passes both cause deterioration to the road pavement. Research elsewhere has found that light vehicles weighing less than 1500 kg Cawangan Jalan, Ibu Pejabat JKR, K.L

(gross weight) will not cause any significant damage to the road pavement. Heavier vehicles normally fitted with large axles will cause the damage. The weight of an individual axle is called an axle load. A standard axle has been defined as having an axle load of 8 160 kg (8.16 Tonne). The repetition of this standard axle is used as the quantitative measure of damaging effect to the road pavement. The extent of the final rehabilitation measures recommended depends on the expected usage of the improvement. Accurate traffic assessment is needed to study and forecast the impact resulting from the road improvement. The changes in traffic movements will determine the future life of the pavement. Effects of traffic volume and loading to the pavement service life have been established since the AASHO road test. It was shown that the pavement life is dependent substantially on the amount of heavy axle load passes. Prediction of the accumulated standard axle load requires high degree of accuracy. The number of axle loads depends on the commercial vehicle activities and types of goods transported along the road. 4.2 TRAFFIC CATEGORIES It is highly likely that due to change in land use and other factors, the traffic using the road will change once the pavement is upgraded. Origindestination surveys coupled with axle load surveys are the best methods that can be used to predict the traffic volume and type and also the axle load spectrum within the study area. Although it is expensive and time consuming to perform this task, it is necessary to achieve an accurate prediction of future pavement service life and performance. It should be carried out if resources are available. Apart from normal traffic using die road, there will also be generated and diverted traffic. Normal traffic can be counted by traffic survey. Origin destination surveys can be used to estimate the amount of generated and diverted traffic.

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4.2.1 Normal traffic This category of traffic will pass along existing road even if no improvement is carried out. The existing traffic count by the Highway Planning Unit (HPU) consists primarily of this category of traffic. 4.2.2 Generated traffic Road improvement will increase the efficiency in transportation and would result in additional traffic. This category of traffic is difficult to forecast accurately. It will only be significant if the reduction in transport cost is high. In many cases, generated traffic on the existing Federal road networks can be ignored. 4.2.3 Diverted traffic When the pavement condition has improved, there will be traffic diverted from another route (or mode of transport) preferring to use the improved facility. This is- an important consideration in the design. Most traffic survey would not only measure normal traffic, it includes the amount of possible deviated traffic. In this case, it is necessary to carry out origindestination surveys that could provide data on the traffic diversions likely to take place. This survey should be carried out for projects with large sums of money allocated for improvements. Assumptions can be made that all vehicles will divert to the improved facility if time or money can be saved, otherwise they will remain using the same route or mode. In Malaysia, changing modes of transport as a result of road improvement is negligible since the choice of other modes of transport is limited. It can be significant if other main transportation modes, especially railways, are improved. Rail services have the capacity to carry heavy loads and possibly reduced pavement loadings. However, in view of the higher quality of service provided by road, only small allowance can be made. 4.2.4 Special traffic In Malaysia, there has been cases where new economic development has introduced extra Cawangan Jalan, Ibu Pejabat JKR, K.L

road transportation activities. Heavy materials or goods in transit have significantly increased the damaging effect to the pavement. If the development can be forecast or known earlier, it is best to include some of this future effects in the design. In certain cases, a specific direction of travel has a very large difference in damaging effect compared to the other direction. Rehabilitation design must consider this phenomenon especially if the probable damaging effect is very significant. 4.3 TRAFFIC AND AXLE LOAD SURVEYS The Highway Planning Unit (HPU) carries out two traffic counts yearly at designated road links throughout the whole country in the months of April and October. Results of the counts can be obtained in the following year. However, axle loading and origin-destination information are not included. For immediate and effective traffic information for pavement evaluation, specific surveys need to be carried out. These specific surveys may include origindestination surveys and axle weighing. However, if generated or deviated traffic is predicted to be small, the origin-destination survey can be ignored. 4.3.1 Specific survey methods To reduce errors in estimating traffic and axle loading, it is recommended that for specific surveys, consecutive seven-day counts or weighing during normal period be carried out. The 24-hour count is preferred since heavy vehicles are more active after dusk. If this is too difficult or costly, a 16-hour count or weighing can be carried out coupled with at least a full 24-hour count or weighing so that adjustments can be made to gross up the 16hour values. More accurate results can be obtained if this procedure is repeated several times during the analysis year. A representative daily traffic volume or loading can be calculated from this method of sampling. For specific surveys, traffic counts can be car

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Plate 4.1 Axle load weighing 16 HOUR TRAFFIC COMPOSITION BY VEHICLE TYPE OCTOBER 1990

Section No. (Old) (New)

16-IIr Peak Hr Trailic Traffic

Percentage Vehicle Compositions (Period) Cars & S. Vans & Medium Heavy Buses M'cycles Heavy Trucks Utilities Lorries Lorries Vehicles

DISTRICT BATU PAHAT OS29 (JR105) 9630 845 (1700 - 1800) 18.3 S28R (JR107) 18121 1703 (1300 - 1400) 38.4 OS29 (JR105) 11510 1381 (0700 - 0800) 45.3

13.3 14.2 11.3

15.0 10.0 12.8

6.2 4.0 6.1

3.1 6.5 3.5

14.1 26.8 21.0

24.3 20.5 22.4

10.4 12.7 8.5

16.8 8.4 19.7

14.8 5.0 17.2

3.5 2.9 4.0

12.0 26.8 7.1

35.1 16.3 40.9

(1800 - 1900) 51.3 (1700 - 1800) 50.4 (1500 - 1600) 39.6

9.8 9.8 8.7

12.0 12.7 23.8

6.0 2.5 7.6

3.0 2.8 3.1

17.9 21.8 17.3

21.0 18.0 34.5

(1400 (1700 (1400 (1900

12.9 15.4 11.8 12.5

10.9 11.2 10.2 9.2

12.3 12.9 18.3 4.7

2.1 2.0 1.6 1.5

DISTRICT KELUANG 0042 (JR305) 12100 1024 (1800 - 1900) 42.6 F54R (JR306) 26695 2111 (1700 - 1800) 44.2 0043 (JR304) 1164 7878 (1700-1800) 43.5 DISTRICT MUAR F42R (JR61 I) 6016 452 OF-41 (JR601) 10596 881 S26R (JR609) 5055 410 DISTRICT SEGAMAT 0038 (JR801) 6444 0052 (JR802) 5614 0039 (JR803) 6583 OS22 (JR804) 4444

488 442 556 416

- 1500) - 1800) - 1500) - 2000)

40.3 43.4 44.7 42.3

21.6 25.3

15.0 26.1 13.4 30.1 29.8 15.4

Table 4.1 Typical HPU Traffic Sutiey results Cawangan Jalan, Ibu Pejabat JKR, K.L

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ried out manually using hand-held traffic counters. The counting operation can be divided into a few groups to count specific vehicle types in both directions of travel.

equivalence single axle load factor for each axle weighed is calculated using the relationship : EF = (N/8.16)4.55

Portable axle weighing devices can be used to weigh the axle loads of heavy vehicles Plate 4.1 Weigh-in-motion technique is also available and this could be a better choice since full sampling of heavy vehicles can be made. Both types of equipment normally measure the wheel load of each axle. The axle load will be twice the wheel load. 4.4 FORECASTING FUTURE TRAFFIC 4.4.1 Base data The base data for forecasting future traffic can be taken from the specific traffic and axle load survey results. If this is not available, traffic information from the HPU can be used (Table 4.1) 4.4.2 Methods of Predicting growth and Compounding The year of survey is normally taken as the base year. Refering to past historical traffic data, the growth rate of normal traffic can be estimated. The baseline traffic can be calculated after making allowances for possible generated and diverted components. From the baseline traffic, future traffic can be accumulated over the design period using the standard compounding formula. CESA = YESA x {( 1 + r )" - 1 }/r Where CESA = Cumulative equivalent stan dard axles YESA = Equivalent standard axle of base year r = Growth rate n = Design life 4.4.3. Estimating Damaging Effect (Load equivalent factor) The axle load survey data is used to estimate the damaging effect of heavy vehicles. The Cawangan Jalan, Ibu Pejabat JKR, K.L

Where : N = Axle load (in Tonnes) EF = Equivalent factor of the damaging effect 4.55 is the load equivalency exponent 8.16 is the standard axle load in Tonnes The axle equivalency exponent of 4.5 can be used as an interim value. This value was recommended for use in Malaysia based on overseas experience (2). It is sufficient to use this value to assess the damaging effect. If axle load surveys are not possible, estimates of the damaging effect can be chosen from past studies of similar survey. The estimates can also be made using procedures given in Arahan Teknik (Jalan) on pavement design. 4.4.4 Sensitivity and Accuracy The errors in traffic estimation for pavement evaluation will come from areas described below. To reduce these errors some guidelines are provided: i). Traffic counts If the method of counting as described in para 4.3.1 is used, then error in obtaining representative daily traffic volume can be minimized especially if it is repeated a few times. A specific survey is better than relying on periodic count. ii) Axle weighing and estimation The accuracy in weighing will depend on the type of equipment used. Static weighing is more accurate but slow and only small samples can be obtained. The weigh-pad must be made level with the surrounding test area otherwise a small tilt of the vehicle could introduce large errors. Weigh-inmotion techniques could Page 53

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be faster and produced more samples but it may not be accurate. Thus, it requires skillful calibration. Any weigh ing method can be used provided the above considerations with respect to accuracy are carefully noted. iii). Conversion to damaging effect The equivalency formula given in para 4.4.3 is subject to changes when more local research results are available. This is the best available estimate of damaging effect being used by many countries. Each axle weight should be converted individually using the relationship and totalled for a specific class of vehicles. The mean equivalent factor for each vehicle class can then be determined by dividing the total equivalent factor by the total number of vehicle in that class.

need to be made for these cases. Using the results from the heavily loaded lane only, can sometimes be adopted. Due consideration must be made if it is too excessive and becomes uneconomical. Staged rehabilitation may be more appropriate in such cases where the risk can be reduced. 6. Seasonal variation Traffic flow and transportation of goods in Malaysia in general have very small seasonal effect. The majority of the national agricultural and industrial products are available throughout the year. In most evaluation cases, error with respect to this can be considered insignificant and ignored. However, in certain regions of the country seasonal variation due to the rice harvest may be significant. 7. Abnormal cases

iv). Estimating growth Estimating the growth rate of heavy vehicles can be the most difficult part and could change the overall estimate drastically. Some economic knowledge of the country is thus helpful. Advice and discussions with economists are invaluable. The growth rate of heavy vehicles is dependent on economic activities and transportation of goods especially for semi-agricultural country like Malaysia. As a broad estimate an assumption can be made that the growth rate is similar or twice the growth in Gross National Product (GNP). v). Directional difference On certain roads. traffic flow or damaging effect due to heavy vehicles travelling in one direction can be very different to that of the opposite direction. Lorries using roads connecting logging areas, quarries. docks, steel factories, etc., are heavily loaded when they leaves these areas but are mostly empty when coming in. Special allowances Cawangan Jalan, Ibu Pejabat JKR, K.L

Malaysia being a multiracial nation has many festive seasons the dates of which change yearly. Care must be taken not to cam, out any stirvev at this time. othenvise, the result will not be representative. Small allowances can be made to adjust these effects. There are cases when upgrading are needed for specific activities such as the construction of huge projects that requires transportation of heavy materials at using identified routes within specific or non-specific periods of time. Information on the quantity of materials to be transported and the type of vehicles to transport the materials will enable estimates of the increase in damaging effect to be made. A typical case is shown in Problem 2 of the following examples. 4.5. EXAMPLES Problem 1 In the year 1989, a road stretch from Muar town to Tangkak leading to the North-South Expressway was to be upgraded. The Expressway terminated at the Tangkak interPage 54

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change and vehicles travelling southbound would exit there. The next portion of the Expressway, southbound, was projected to be completed in late 1992 where 50 per cent of southbound heavy vehicles using the road was expected to divert to that part of the NorthSouth Expressway. The expected increase in northbound heavy vehicle traffic was 20 % due to increase activity towards the highway. Estimate the damaging effect for rehabilitation design for ten years for each direction taking the diversion into consideration and compare the average loading if the diversion was ignored.

Heavy Vehicle Group

(sum) Equivalent Factor

(sum) Vehicle

Mean E.F.

A

7.38

225

3.28

B

1000

350

2.86

C

270

125

2.16

D

200

450

1.33

Solution 1:

Table 4.2

A specific 24 hour classified axle load survey was carried out where all the heavy vehicles were weighed. The results obtained were as shown in Table 4.2 and 4.3.

Heavy Vehicle Group

(sum) Equivalent Factor

(sum) Vehicle

Mean E.F.

A

124.32

112

1.11

B

116.10

135

0.86

C

40

80

0.50

D

26.25

75

0.35

Seven consecutive 24-hours count was carried out and the summary of heavy vehicles are shown in Table 4.4. In 1989, the yearly damaging effect of the southbound direction was 429,717 standard axles, 257 °" higher than the northbound traffic. The above table shows that the vehicle loading is critical in producing the difference in damaging effect. In this case commercial vehicles travelling southbound were more heavily loaded. It is highly likely that these vehicles contained raw products that are normally heavier than processed products. A similar trend of loading and damaging effect is assumed in the 10 years' design period. The expected growth rate is 5 per cent throughout the design period. To calculate the cumulative loading for that period, the relationship in para. 4.4.2 can be used. However, the calculations shown below are for each year. to sho,,N the effect of diversion. This method of calculation is also suitable for estimating past traffic when each yearly damaging effect will be known more accurately. If the diversions were not considered the fol Cawangan Jalan, Ibu Pejabat JKR, K.L

Table 4.3

Axle load survey results for direction 1, Southbound.

Axle load survey results for direction 2, Northbound.

lowing traffic will be estimated :Southbound : CESA = 429,717 x { (1 + .05)'° - 1}/0.05 = 429,717 x 12.5778 = 5,404,934 = 5.4 million standard axles (msa) Northbound : CESA = 120,337 x 12.5778 = 1,513,586 = 1.5 msa.

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E HEAVY VEHICLES GROUP A Directions

GROUP B

GROUP C

GROUP D

South Bound

North bound

South Bound

North bound

South Bound

North bound

South Bound

North bound

1

125

112

212

202

95

76

45

41

2

186

156

255

215

72

82

56

51

3

172

190

189

172

88

98

62

64

4

144

124

156

144

86

66

52

59

5

131

123

178

128

67

67

55

57

6

122

132

119

111

66

56

49

42

7

91

77

120

122

30

43

12

5

131

176

156

72

68

47

46

1.11

2.86

0.86

2.16

0.50

1.33

0.35

53075

183726

48968

56765

12410

22816

5877

Day

AVERAGE 139 VEHICLES STANDARD AXLE PER COMMERCIAL 3.28 VEHICLE (SA/CV) CUMULATIVE YEAR166410 LY S. AXLE

Total yearly Southbond cumulative standard axles = 429.717 Total yearly Northbond cumulative standard axles = 120,337 Table 4.4. Traffic Count Results For direction 1, Southbond

YEAR

COMMERCIAL VEHICLE Southbond

Northbond

1989

429,717

120,337

1990

451,202

126,354

1991

473,762

132,671

1992

497,451

139,305

1993

261,162

175,552

1994

274,220

184,300

1995

287,931

193,516

1996

302,328

203,191

1997

317,444

213,351

1998

333,316

224,018

1999

349,982

235,219

TOTAL

3,548,798

1,827,477

COMMENTS Base year

North-south Expressway (Completed)

End of analysis period

Average cumulative yearly standard axles (CESA) = 2.69 msa Table 4.5. Distribution Of Yearly Damaging Effect Cawangan Jalan, Ibu Pejabat JKR, K.L

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Survey Date

Total Daily Commercial Vehicles

percentage Commercial Vehicles

Estimated equivalent Factor (Table 3.2)

Damaging Effect

April

442

23 %

3.0

1326

Table 4.6. Summary Of Traffic Counts Results Obtained From HPU

Average CESA = 3.45 msa The average design accumulated loading is nearly 30% higher if the diversion is ignored. Solution 2 : Without specific traffic or axle load survey results From the HPU traffic survey results in 1988, the traffic results as shown in Table 4.8 were obtained from a recent count in April. If similar count is available in October, the average values should be used. The yearly damaging effect = 1326 x 365 = 483,990 standard axles. This will be the base year traffic. Accumulation procedure can be done similarly as shown in the previous solution

activity, several assumptions were made, as listed below :i.

The distribution of load in the trailer is uni form and distributed within the trailer length with no overhang.

ii. The distribution ratio of axle loading on the five wheel arrangement is 0.14:0.20:0.20:0.23:0.23 and remains similar for lower or higher gross load. iii. Only trucks with minimum of five axles will be used and trucks returning are ennpty resulting in negligible damaging effect. iv. The damaging criteria considered was based on phenomenological theory of cumulative axle load damage only using equation given in para. 4.4.3.

Problem 2: Abnormal traffic Solution : A road is to be upgraded to transport 900,000 tonnes of goods yearly, from one end to the other. The estimated maximum gross weight per vehicle that will be used is 45 tonne. The specification and dimension of the vehicle are available. The vehicle type is a five axle trailer. The distribution ratio of axle loading on the five wheel arrangement is 0.14:0.20:0.20:0.23:0.23 on the five axles and remains similar for lower or higher gross loads. This additional commercial activity will increase the damaging effect to the existing pavement. Estimate the increase in damaging effect on the pavement. The damaging effect will depend on the configuration of the vehicles and the load that they will carry. For the purpose of estimating the damaging effect of this additional commercial Cawangan Jalan, Ibu Pejabat JKR, K.L

The gross weight of each vehicle was found to be 45 tonnes with maximum axle loads of more than 10 tonnes, the loading that may be used. Amount of goods to be transported yearly is 900,000 tonnes. Gross weight of each vehicle = 45 tonnes pay load = 37 tonnes Maximum axle load will be 10.35 tonnes. Therefore number of vehicle trips per year = 900,000/(37) = 24,324 The vehicle type is a five axle trailer that will have an estimated axle load distribution ratio of 0.14:0.20:0.20:0.23:0.23 on the five axles. It is

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assumed that the distribution of goods in the lorry is uniform and distributed over the full length of the trailer, otherwise this figure may change significantly. For gross weight of 45 tonnes , the damaging effect that this lorry would provide is 9.33 times standard axle weight of 8.16 tons or the nunnber of equivalent standard axles per lorry is 9.33. The accumulate yearly standard axle is therefore : 24,324 x 9.33 = 226,943 or 0.227 million standard axles (msa). For each year, the additional number of axle loading that will be experienced by the pavement is 0.227 msa. This additional loading will increase the rate of deterioration to the pavement. Other factors controlling the rate of damage will depend on the current structural condition of the pavement and distribution of the goods in the trailer. The existing condition of the pavement could be evaluated by proper pavement evaluation if deemed necessary (Chapter 3). Existing pavements which have high traffic loading inay not experience significant increase in axle loading or the damaging effect resulting from the values calculated above. The normal traffic using the route is already high, therefore the percentage increase would be small. However for an existing pavement with low traffic loading and weaker pavement, an increase in the axle loading with the above magnitude will accelerate the rate of deterioration. This is not favourable and due consideration must be made if the abhormal traffic is to utilise such roads. 4.6 REFERENCES 1. The AASHO Road Test Report, Highway Research Board. Report 5: Pavement Research.Special Report 61E. Washington, D.C., 1962 (National Academy of Science, National Research Council), Publication No. 954. AASHO

loads in developing countries using a portable weighbridge. TRRL Road Note No 40. Her Majesty's Stationery Office, London. 3. ZAIN ARIFFIN, YOJIRO MIYAOKA, Axle load survey at Jalan Vantooren, Port Kelang, Selangor. Cawangan Jalan Ibu Pejabat JKR, Kuala Lumpur 1983. CHAPTER 5 : METHODS OF REHABILITATION 5.1

SELECTION PROCEDURE

In the previous chapters, the sources of pavement problems, their failure modes and performance forecasting have been described. In this chapter, the results of the evaluation carried out on the pavement are used to establish the most appropriate method of rehabilitation. The selection procedure depends heavily on engineering judgement but other factors such as costs, construction feasibility, effects on the gradeline and the road user should be considered as well. The general process of selecting an appropriate treatment is as shown in Figure 5.1. Stage l: Identifying Prohlein As a first step, the mode of failure of the existing pavement needs to be identified. At this point, constraints on the projects such as the design life of the rehabilitated section should be identified. Stage 2: Identifying Prohahle Alternaties Based on the results of pavement evaluation. a number of alternative methods of rehabilitation should be selected. These are tested against the feasibility of design, construction constraints, and requirement of service life. Stage 3: Selecting the Preferred Solution

2. Transport and Road Research Laboratory (1978) Guide to the measurement of axle Cawangan Jalan, Ibu Pejabat JKR, K.L

Those alternatives which pass these criteria are Page 58

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Stage 1

IDENTIFICATION OF PROBLEMS

* Conduct pavement evaluation * Identify constraints

Stage 1

IDENTIFICATION OF PROBLEM ALTERNATIVES

* Select possible rehabilitation treatmrnts * Chock design and constuction constraints

Stage 1 * * * * *

SELECTION OF PREFERRED SOLUTION Cost analysis Other constuctions Select preferred solution Detailed design Construction Figure 5.1. General process For Selecting Appropriate Rehabilitation Alternatives

Figure 5.2. The Spectrum Of Pavement Rehabilitation Alternatives

further analysed by considering their life-cycle costs and other non-monetary constraints. Finally, the preferred rehabilitation alternative is selected for detailed design. The engineer should not rule out using different techniques on one project. It may be more cost effective to do this than select a common method of reha Cawangan Jalan, Ibu Pejabat JKR, K.L

bilitation for the whole project. Each alternative technique is evaluated first on the merit of its design and construction feasibility. Consideration should be given to the problems of construction during monsoon periods, for instance. Care must be taken where roads Page 59

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pass under bridges. For traffic and safety purposes, the vertical clearance underneath a bridge should be maintained and this will limit the allowable overlay thickness. Other factors to consider include traffic control requirements, disturbance to the public, the need for staged construction, and the availability of plants and materials.

i) ii) iii) iv) v) vi)

5.2

rejuvenating the aged surface using chemicals scaling the cracks blinding polished and flushed surfaces with hot aggregates applying thin bituminous overlays cutting affected areas and patching with new bituminous mixes recycling the affected surface

REHABILITATIION OPTIONS

The rehabilitation of flexible pavements encompasses a broad range of activities which could be grouped into three categories namely: i) Restoration ii) Resurfacing (strucl.ural) iii) Reconstruction The choice of any specific rehabilitation technique depends on the condition of the existing pavement. The conditions which apply for one project may be different from another. For this reason, rehabilitation techniques will change from one project to another or within one single project. Although other factors are involved, theperformance and cost-effectiveness of each type of rehabilitation technique will depends primarily on the existing pavement condition. As a general guide, the different pavement rehabilitation options can be summarised as shown in Figure 5.2 where they are related to the life of the road. In the first phase of the pavement's life, its condition is good and its rate of deterioration is normally low. At this stage, routine maintenance should be considered as it may be more cost-effective than carrying out major maintenance later in the life of the pavement.

The surface recycling and cut and patch alternatives should be considered especially when the deterioration of the pavement is more advanced but has not reached the stage where a structural overlay is necessary. Successful restoration work achieves one or more of the following; it repairs the existing distress, decreases the rate of increase of roughness, and slows down the subsequent pavement deterioration by arresting the mechanism causing the distress. For example crack sealing will preN ent water from entering the pavement thus preventing failure in the lower layers. Resurfacing (Structural) As the cumulative traffic load increases the fatigue life of the surfacing is exceeded, which eventually manifests itself in the form of cracking in the wheel path (crocodile cracking). When the pavement has suffered severe and extensive structural damage, restoration works may not be cost-effective. Structural improvement would then become a costeffective option. It is therefore important to determine when a pavement requires structural improvements as opposed to restorative work. This can be done by carrying out a pavement evaluation excercise to determine the structural integrity of the pavement.

Restoration As the pavement condition deteriorates further, particularly when distress such as cracking and polishing of the aggregate become apparent, the restoration rehabilitation option is warranted. Some techniques that maintain the serviceability of the pavement include :

Cawangan Jalan, Ibu Pejabat JKR, K.L

Resurfacing is currently the most popular method of rehabilitating distressed pavements in Malaysia. It involves the placement of fresh material on the existing surfacing which improves riding quality and provides additional structural strength. It is necessary to design the overlay thickness in order to achieve the desired design life. Page 60

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Figure 5.3. Replacement Of Loss Chemical Constituents By Rejuvenation

The most commonly used resurfacing materials are: i) thick asphalt overlays ii) granular overlays Resurfacing cm be applied to all types of distressed surfacing, but pre-treatment is sometimes necessary before resurfacing is actually carried out. Reconstruction A pavement that is allowed to deteriorate further will eventually reach a state where the deterioration is so advanced that even a thick overlay would be less cost effective than the reconstruction option. Reconstruction of the pavement layers will be necessary when any of the layers has deteriorated beyond economical repair. Depending on the layers needing repair, reconstruction can be categorised into full or partial reconstruction. Full reconstruction is needed when the existing subgrade has deteriorated and become unstable. Partial reconstruction is carried out when only the road base or the subbase layers have deteriorated. In order to determine the extent of reconstruction required, the pavement structure will have to be examined by carrying out an evaluation Cawangan Jalan, Ibu Pejabat JKR, K.L

of the existing pavement condition. This can be done using non-destructive methods or by digging trial pits to carry out a more direct examination of the conditions of the lower pavement layers. However, digging trial pits should be avoided as much as possible because the reinstatement works usually do not bring back the pavement to existing conditions. This will result in a depression on the road surface. When the failure of the road base is very extensive, the road base can be recycled along with asphalt surfacing either by adding additional aggregate or cement to stabilise the new road base material. The construction of recycled stabilised road bases requires specialised machinery. Standard plant are not not suitable for this type of construction. 5.3 RESTORATION Restoration is designed to restore the surface to a suitable condition for placement of an additional stage of construction or otherwise to perform satisfactorily for a substantial period of time. These techniques include rejuvenation. patching, cold milling, crack sealing and surface recycling. Page 61

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The restoration option is suitable for pavements with good structural integrity of standard deflection lower than l).5 mm. It is best applied to pavanents with distress limited to the surfacing. Block cracking, stripping, cracks, ravelling, polishing, bleeding and aged surfacing are the typical types of failure suitable for restoration techniques.

should be compared to the increased life of pavement to establish its cost effectiveness. Construction : The application of the rejuvenating chemicals is simple to carry out. There is no special equipment needed for this work. On a larger size job, it may be economical to use a mechanical sprayer (Plate 5.1)

5.3.1 Rejuvenating Description: Hardened or aged bituminous surfacing can be restored by spraying a laver of bitumen or polymer modified bitumen to improve its existing condition. Rejuvenating agents have been introduced as an alternative as they can restore the original properties of the bitumen. Figure 5.3 shows the constituents of the bitumen in the bitumen suffering from hardening and the effects of adding lost constituents. The effect of rejuvenating agents has not been studied in the Malavsian environment. Currently the available products claimed that the rejuvenating agents could replace the polymeric constituents lost as a result of oxidation and loss of volatiles. Howevcr the correct choice of rejuvenating agent depends on careful study on the bitumen condition in the existing surface as it will dictate the type and amount of rejuvenating chemicals to be used. Conditions of use : AgeHardening had been described earlier as a major cootributary factor to deterioration of bituminous surfacings.

Since the chemicals used tend to-leave a layer of residual oils on the road surface, slowing down the traffic during the initial period is very important. Cost : Currently, in Malaysia there are not many rejuvenating chemicals being marketed. The price range for a rejuvenating job is about RM 2.00 to RM 4.00 per square metre depending upon the area to be rejuvenated. Reliability : The performance of the rejuvenating chemicals depends upon how deep the chemicals are drawn down into the bituminous layer. This is dependent on the density of the surfacing. A dense mix such as the Asphaltic Concrete Wearing Course will experience little draw down. Rejuvenating chemicals are useful when used with other methods such as the surface recycling, where the chemicals are used to replenish the lost chemical constituents in the asphalt. 5.3.2 Crack Sealing

The top few millimeters of the surfacing suffer the most severe hardening. Thin surfacings which suffer from this effect will look dry. For thick asphalt, cracks may occur from the top where rejuvenating chemicals can be applied. Laboratory tests are needed to identify the degree of improvement and thus the most correct use of rejuvenating chemicals. Excess introduction of polymeric constituents may effect the bitumen properties. As such, precautions should be taken to eliminate the possible introduction of other problems such as bleeding, a slippery surface and weakening of existing asphalt. The cost of rejuvenating agents Cawangan Jalan, Ibu Pejabat JKR, K.L

Description: Crack sealing is a cheap restoration alternative which would seal the cracks from ingress of water. Small or fine cracks (< 3mm wide) may be filled with crack fillers. In addition, fine sand or fine aggregates may be added to fill up larger cracks. The major benefit to be gained from proper sealing is that it reduces water infiltration into the cracks. Conditions of use : Crack sealing is normally carried out for environmentally induced block cracks where environment is the major controlling factor of Page 62

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Plate 5.1. Rejuvenating Aged Asphalt Surfacings in progress

such failures. Fatigue related cracks which are sealed only provide short term benefits. The performance of crack sealants will depend on the age of the pavements and traffic loading. It is also best done where the road is structurally strong. There are several different types of crack sealants, and each has its own unique properties. Hot or cold bituminous products are generally used. Sealant materials available include rubber asphalt, low modulus silicone and petroleumbase sealants. Each of these materials has different durability, bonding, extensibility and other properties. Only the best available sealant should be used for long lasting performance. Crack sealing should be carried out as a means of deterring ingress of water into the pavement layers. Construction:Before cracks are sealed it is better to remove dirt and loose materials from the cracks. These are done using air compressors. Care must be taken to ensure safety of vehicles before opening to traffic. Any loose material must be swept away. If sand is used as additional filler, allowing slow moving traffic can help the embedment of the small particles into the cracks. Excess filler material must be removed since this could reduce the skid resistance of the surface (Plate Cawangan Jalan, Ibu Pejabat JKR, K.L

Cost : The cost of sealing cracks depend on the type of sealants used and the size of the job. The cost can range from as low as RM 0.50 to about RM 3.50 per square metre. Reliability : Crack sealants will not completely fill the full depth of the cracks. Only the top few millimetres are filled. Because of this, the use of crack seals is limited to those cracks which have not propogated completely through the surfacing. 5.3.3 Cutting and Patching Description : Cutting and patching is the replacement of deteriorated asphalt surfacing with suitable bituminous mix, placed and compacted to similar level to adjacent undeteriorated asphalt. There are two types of bituminous patching materials which are commonly used : i) hot-mix asphalt ii) cold mix asphalt These mixtures vary widely in quality, composition and cost. Bituminous patching mixtures must have suffi Page 63

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Plate 5.2. Crack Sealing

ciently good properties. The required properties are : i) Stability - to resist shoving and rutting ii) Cohesiveness - should stick to host material iii) Resistance to water - impermeable iv) Durable - resist wear v) Workability - easily handled and constructed vi) Storageability - can be stored xvithout deteriorating for immediate works The performance of a bituminous patch depends on quality of the materials and construction techniques. Conditions of use : For pavements with localised surface failures, cutting out the failed areas and patching it with new bituminous mix should restore the pavement. The 'cut and patch' method is also a means of pre-treating the existing pavements before a resurfacing work. It is designed to remove the existing cracks and thereby eliminate reflection cracks. However, the cracks have to be removed totally as cracks in the lower layers will eventually cause reflection cracks on the new layer. For pavements with rutting caused by the instability of the wearing course mix, the 'cut and patch' alternative is also suitable. This type of Cawangan Jalan, Ibu Pejabat JKR, K.L

failure is mostly found on climbing lanes and at junctions. The unstable layer must be removed prior to being replaced with a stiffer mix. Construction : Even though the construction of patching does not require special equipment, proper construction technique is still important. On many ocassions, the construction is not carried out properly causing the patched area to fail early. The correct construction method is described below. See also Figure -5.4. Marking The boundaries identified to be patched should be marked. Straight line markings are prefered. All deteriorated areas should be included with allowance for joints. These boundaries can be changed during cutting to allow for initially undetected damage. Cutting The area marked for patching should be neatly cut and removed using a proper asphalt cutting tools. A vertical unbroken cut will enhance adhesion and promote efficient compaction. Cleaning and drying The surface under the new patch must be clean, dry and free from loose material. Air blowing followed by vacuum cleaning is recommended for efficient cleaning and drying. Page 64

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Figure 5.4. Proper Methods For Cutting and Fatching

Tack Coating A thin bituminous layer is normally sprayed uniformly on the prepared surface prior to patching hot-mix to promote adhesion between the new layer and the cut surface. For small jobs, low pressure hand sprayer can be used, whereas a bitumen sprayer is suitable for large areas. Tack coat materials available include : i) cut-back bitumen ii) bitumen emulsion iii) synthetic resin

Compaction Vibratory rolling is the best method for compacting patched area. By rolling the edges first the filling will pinch into the hole. The centre of the patch is rolled first, moving outwards towards the edges with each succeeding passes. This will tighten the adhesion around the edges. The roller should rest completely on the patched area and not partly on the old pavement. Cleaning up and checking joints

Tack coating should not be applied if cold-mix asphalt is used, unless the patch surface is made of concrete. The tack coat can soften the coldmix and promote shoving and stripping. Filling The material can be placed in several lifts. A single lift should not exceed 100 min thick. Filling is normally carried out manually. Shovels should be used and raking is not advisable to reduce segregation. Hand tamping at edges and corners can also be carried out with a hand rammer. The surrounding surface must be kept clean from spilled filling material. Cawangan Jalan, Ibu Pejabat JKR, K.L

Cleaning up is essential for a comprehensive patching ,job. Checking the finished product especially the joints should be carried out. The edge or joints of the patch should be sealed using bituminous material similar to crack sealants described earlier. The life of the patch is often dependent on how well the joints are made. Cold Milling If extensive patching is required or if the proposed patches are too close to each other, then cold milling can be considered as an option. A Page 65

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Interim Guide To Evaluation And Rehabilitation Of Flexible Road Pavements. 5.3.4 Thin Bituminous Overlays Thin bituminous overlays provide a feasible alternative for low cost pavement surface restoration. It improves the surface riding condition and can extend the service life of a pavement. It can also be used as a short term measure to address specific distress condition. Most commonly used thin asphalt overlays are : i) Surface Dressings ii) Slurry Seals (Thin seal mixtures) iii) Thin Hot Mix Overlays. Surface Dressings Description

Plate 5.3.Cutting And Patching

milling machine is required for this work. This machine can cut the deteriorated surfacing to the depth and width as required. The maximum depth and width depends on the machine type and specifications. The milled material can be salvage or recycled. Patching should then be carried out using an asphalt paver. Cost : The cost of cutting and patching pavements is noNN- competitive. The cost ranges between RM 8.00 to RM 10.00 per square metre. Reliability : The performance of a patched area depends heavily on the type of mix used and the construction standard. If constructed properly, this alternative would be able to last the life of the untreated sections. But if poorly constructed, this alternative can increase the roughness of the road section.

Cawangan Jalan, Ibu Pejabat JKR, K.L

:

A surface dressing is an application of bitumen followed with an aggregate cover in a single or multiple application. In double surface dressings the larger sized stones are place in the first application with the smaller sized stones in the second application to fill in the voids in the first layer. The aggregates used have to be cleaned and free from dust. This will facilitate cohesion between the aggregates and the bitumen. If dusty aggregates are used, then pre-coating them first is more suitable. Conditions of use : Surface dressing has been commonly used as a wearing course on low volume roads. It has also been used as a resurfacing technique to treat surface failure on these types of roads. The potential use of the surface dressings to restore distressed bituminous pavement has not been fully demonstrated in Malaysia, even though it is greatly used in Australia and the United Kingdom. Apart from being able to restore the riding quality of the road surface, it has other advantages. The high bitumen content of a surface dressings layer means thicker bitumen film will be coating the aggregates. This will improve resistance to ageing making the surfacing more durable. At present, limited local experience in the use of surface dressings on asphaltic concrete surfaces restricts its application on high volume roads because of the Page 66

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Plate 5.4. Cold Milling

worry that loose stones may pose hazards to the traffic. Furthermore, the long construction period may cause traffic distruption. As such it is proposed that the use of surface dressings on asphaltic concrete surfaces be limited to low volume roads with Average Daily Traffic (ADT) < 5000. When using surface dressings on asphaltic concrete surfaces, a proper design needs to be carried out. The design guideline from the Transport Research Laboratory Overseas Road Note 3 specifies the rate of spray of the binder and the aggregates as important to the performance of the surface dressings. The hardness of the existing asphaltic concrete surface and the flakiness of the aggregates are important considerations too. The hard surface will not allow any penetration of the aggregates for embedment and because of this, a suitable binder is needed to ensure the stones are not whipped off by traffic. The use of modified bitumen, fibres or special aggregate may improve the construction procedure and. enhance the performance of surface dressing. This improved performance will increase its applicability on high volume roads. Construction : The construction of the surface dressings Cawangan Jalan, Ibu Pejabat JKR, K.L

requires the binder to be sprayed using a mechanical sprayer and the aggregates to be spread by a specially designed chipping spreader. These are inexpensive and are easily available locally. Traffic control immediately after the surface dressings have been applied, is important. This is due to the loose chippings which still need kneading by the traffic tyres. During this period, at least 2 hours after application for normal bitumen, the speed of the traffic have to be low. This period may be reduced if modified binders are used. Cost : The cost of construction of surface dressings on laterite surfaces (usually in the rural areas) is less than half that for Asphaltic Concrete. But to construct it on existing bituminous pavements may cost more since the binders are different and the traffic control is more elaborate. At present, the cost ranges from RM 3.00 to RM 8.00 per square metre. Reliability : If the surface dressings is constructed on a road that is structurally sound, it will last a long time. The thicker bitumen film thickness ensures the flexibility of the layer and would reduce age hardening. Because Page 67

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of this, the use of surface dressings as a restoration alternative should be encouraged. In Malaysia where the intense sunlight does create problems with the rate of ageing, the surface dressings wearing course may last longer than a thin asphaltic concrete layer.

It has potential for both corrective and preventive maintenance of asphalt surfacings. However, it is not a structural layer. Application of slurry seal is known to retard the hardening process of the top portion of asphaltic concrete surfacing.

Slurry Seals

There are three types of slurry seals, namely. Type 1, 11 and III as specified by the international Slurry Seal Association (ISSA).

Description: Slurry seals are a mixture of aggregates, water and filler (usually cement) bound with bitumen emulsion, and mixed insitu prior to laying using specialized equipment.

The aggregate size, filler and the residual bitumen from the emulsion govern the classifica-

Plate 5.5. Surface Dressing

Plate 5.6. Slarry Seal

Cawangan Jalan, Ibu Pejabat JKR, K.L

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tions. Nominal 4.75 mm aggregate size is specified for Type I whilst size 9.5 mm for Type 11 and 111. The emulsion specified should be checked for compatibility with the aggregate and the desired setting time. Slow setting cationic emulsion is normally used. Conditions of use : The nature of the existing surfacing and the expected traffic level govern the appropriate use of slurry seals. It is not suitable for shape correction or for use at heavily loaded pavements with interconnected cracks or more advanced cracks. Slurry seal should not be applied on structurally, weak areas. Conventional slurry seals using slow setting emulsion need a long curing time, therefore application is not advisable when rain is expected. Rain water can wash away the emulsion, breaking aggregate bondage and destroying the slurry. Localized pavement defects such as cracks, nits, humps, low pavement edges must be repaired before applying the slurry seals. Modified emulsion, fibres or special aggregates can improve the properties and performance of slurry seals. Their conditions of use is similar to the surface dressings described above and may be extended to higher class of roads. Construction : Constriction of the slurry seals require a special paving equipment. A more powerful and faster mixer is required if the modified emulsions are used. It is also desirable to have experienced contractors to do the job. The long curing tirrnc of about 3 to 4 hours for the normal slurry seal makes it necessary for the provision of proper traffic control. This is especially difficult to carry out in built-up areas. Usaull_v, sand is used to blind the areas where traffic may be travelling over the wet slurry. The inclusion of modifiers to the emulsion usually shortens the curing time to about 30 minutes. Cost : The normal slurry seals costs about RM 2.00 to Cawangan Jalan, Ibu Pejabat JKR, K.L

RM 4.00 per square metre, whereas the modified slurry seal costs about RM 4.00 to RM 8.00 per square meter depending on the size of the job. Reliability : Slurry Seals are effective in areas where the primary problem is excessive oxidation and hardening of the existing surface. They may also be used to improve the friction characteristics of polished surfaces at low traffic levels. However, when used in areas where the pavement deflections are high and the surface is suffering from cracks (block and crocodile cracks), the slurry seal will crack very quickly and should not be used. Thin Hot Mix Description : Thin hot mix asphalt is an asphalt mix which is normally less than 40 mm thick. Any type of hot asphalt mix or modified mix can be used. The thin asphalt layer is mainly to correct surface deficiencies and will not add much structural strength to the road. Apart from the normal asphalt concrete, fibrereinforced ultra-thin mix and the porous asphalt mix fall into this category. The fibrereinforced ultra-thin mix is popularly used in Europe with success. The introduction of the fibres increases the fines in the mix, thereby allowing more binder to be added. This additional binder in the mix will help in preventing ageing of the binder. The porous asphalt mix is also popular in Europe. This mix is designed with high void contents to allow for free draining of surface water. The high voids are also able to absorb traffic tyre noise which makes it popular in built-up areas. To ensure stability of the mix, the use of modified binders may be ncccssan-. Conditions of use. Thin hot mixes can be applied at areas subjected to low deflection. It is not meant to correct structural failures and severe rutting. Surfacing that suffer from polishing, stripping, bleeding Page 69

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Figure 5.5. Surfacing Recycle Using Hot Milling Method

can be overlaid with thin hot mixes. Suitable tack coats must be used prior to laying the thin overlays. Strong adhesion with the existing surface is necessary, otherwise delamination and flaking can occur. The present practice of providing a thin overlay (up to 40 mm overlay) without giving due consideration to the structural needs is not a good practice. If laid on top of the existing asphalt layer without prior treatment to the cracked surface, the cracks reflect through the new layer as early as within 3 months depending on the deflection and the traffic intensity of the road. It is therefore very important that cracked surfaces must be treated before overlay. The fibre-reinforced ultra thin mix and the porous asphalt mix are applicable on road surfaces with good structural intensity. These mixes are usually used to enhance the surface properties of the pavement. In addition, the porous asphalt mix can drain surface water fast. Construction : No special equipment other than that used in the construction of normal hot mixes is necessary. Traffic can run on the mix as soon as the rolling is completed. But in the case of the porous asphalt, it is necessary to leave the mix Cawangan Jalan, Ibu Pejabat JKR, K.L

for a couple of hours before opening to traffic. Cost : The cost of constructing the thin hot mix vary according to the types and mix design. For the normal asphaltic concrete thin mix, it cost about RM 5.00 to RM 8.00 per square metre. Tlie fibre-reinforced ultra thin mix costs about RM 6.00 to RM 8.00 per square metre. But for the porous asphalt mix the use of polymer modified binders can increase the cost to about RM 10.00 to RM 18.00 per square metre. Reliability : The aggregate gradings and bitumen type and amount used in this mix will affect the performance of the layer. Because of its thin nature, bigger sized aggregates would be crushed by the steel roller resulting in loose aggregates. Apart from that, the bitumen film thickness will influence the life of the layer. In Malaysia pavement constructed with porous asphalt have performed very well. Its reliability depends on the design of the mix and the type of binder used. The clogging of this type of mix with time may reduce its ability to drain water. 5.3.5. Surface Recycling Page 70

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Description: Pavement surface recycling is the reworking of the pavement surface to improve its performance and correct surface failures particularly surface cracking. It is a growing field in pavement rehabilitation but must be used with care. Suitability of its application will depend primarily on the structural conditions of the existing pavement. Normally it can be applied only when the pavement is structurally sound and the mode of failure is corned to the top of the surfacing. In this method, the surfacing material is scarified or pulverized by using a hot milling (heater-planer or heater-scarifier) or coldmilling device. The scarified materials are mixed and relaid in a number of ways, either in a continuous single pass or in separate operations (Figure 5.5). In using the hot milling method, two types of heating devices are available ie. the open flame heating or the radiant heating. Various manufacturers have developed equipment for the above processes, some of which are used as a heating unit on its own, while the more sophisticed ones can carry out the heating, remixing and laying in a single pass. The benefit from the use of the equipment is subject to field investigations of their actual pavement performance. Another method of recycling the pavement surface is termed as cold recycling. Cold recycling is the reworking of a pavement surface by pulverising the top layer using a milling machine followed by reshaping and compaction. The reshaping and mixing can be done in the Field or at a central plant. Stabilisers and additional materials can be included. The top 25 mm is normally recycled. This is the critical portion where surface failures such as ravelling, bleeding, polishing and weathering occurs. This method is only suitable for correcting surface distress. The structure of the pavement must be intact and capable of accepting an overlay with a standard life expectancy. Conditions of use : Surface Recycling can be applied for all types Cawangan Jalan, Ibu Pejabat JKR, K.L

of surface failures provided the causes and extent are known. Effectiveness of its application is highly dependent on the accuracy of the pavement evaluation . Surface recycling does not provide a substantial increase in the structural strength of the pavement. It is a method for treating the surface distresses. It is a known fact that heating of fresh bitumen during manufacture of the asphalt causes age hardening, and re-heating it during hot milling will induce further hardening. Recycling the pavement surface using the hot milling method with the heat application being higher than 200 deg C, will cause the condition of the bitumen in the asphalt to deteriorate further. To counter this, it is advisable to add rejuvenating chemicals to the remixed layer apart from the addition of bitumen. Available equipment in the market today is only capable of heating and softening the top few centimetres, which restrict the depth of cut for a single pass. The usual depth per pass is approximately 25 mm. With this limitation, the method would be able to eliminate cracks which are of the top-down nature and have progressed to a depth of 50 mm. If the cracks have gone down through the full depth of the surfacing layer, and these are not removed, then there is a possibility the remaining cracks will reflect upwards through the new layer. Construction : Specialized equipment is necessary for the recycling of the pavement surface. The size and cost of this equipment depend on the nature of the operations it can carry out. The most expensive would be the plant which is capable of carrying out the recycling, re-laving and addition of fresh mixes in a single pass. The use of gases to heat the pavement surface and the intense heat generated during the operation may pose a hazardous situation to the road users. Thus proper traffic control is needed during construction. Care should be taken to ensure that no pedestrians are allowed to come near the heating equipment. The operators of the equipment need to be specially trained. Page 71

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Cost : The cost of recycling the pavement surface depends on the type of equipment used and the extent of work involved. It ranges between RM 6.00 to RM 13.00 per square metre. Reliability : Surface recycling is a rehabilitation alternative suitable for restoring pavement surface distresses only. If used on full-depth cracked pavements and with pavement deflections in excess of 0.5 mm. there is a possibility, of the crack reflecting early.

ble of carrying increased traffic. It also improves riding quality. The thickness of the asphalt resurfacing depends on the strength of the existing pavement and the expected traffic. It is necessary to carry out a proper design to establish the thickness of the surfacing.

5.4 RESURFACING

There are two methods of resurfacing popularly used in Malaysia, namely, thick asphalt overlays with or without a prior granular overlay. The foriuer involves the construction of a crushed aggregate layer on the existing pavement before laying the asphalt layer. The use of granular overlays reduces the need for pretreatment works.

Description : Resurfacing is the placement of fresh material on an existing surfacing to enhance its structural strength. Asphalt resufacing is the most popular method of pavement rehabilitation in Malaysia. When done properly, this method is appropriate since the addition of new layers strengthens the road pavement making it capa

Conditions of use : Resurfacing without a prior granular overlay can be applied to rectify many types of pavement failures. However, pre-treatment works such as patching and reconstruction should be carried out at localised failed areas prior to resurfacing. Resurfacing can be applied on surfacings that are cracked, rutted, polished,

Figure 5.6. Methods Of Reducing Reflection Cracks Using Interlayers Cawangan Jalan, Ibu Pejabat JKR, K.L

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raelled, and those that are bleeding. Proper evaluation of the existing pavement condition is neccessary to determine the extent of pretreatment required. The following paragraphs describe some of the aspects that should be considered prior to resurfacing. Resurfacing on Cracked Surfaces Cracks occur frequently on roads in Malaysia. These cracks should be treated early to stop ingress of water into the road base layer thereby weakening it. The common practice of overlaying the cracked pavements without prior treatment to the cracked surface. causes the cracks to reflect through the new layer as early as within 3 months depending on the deflection of the road section and the traffic level. It is therefore very important that cracked surfaces must be treated before overlay. Alternatively, more expensive techniques such as using interlayers to absorb the stresses and strains of the crack tips can be used. One common pre-treatment method is to 'cut and patch' before overlay. This results not only in delaying reflective cracking but it also gives a slight increase in the strengnh of the pavement. The rate of progression of the cracks reflecting through the new asphaltic layer depends on the structural strength of the pavements. Pavements with higher deflection. causing higher crack movements, tend to be the first to crack. Another method of reducing reflection cracks is by introducing a separating layer (Figure 5.6) to absorb the stresses from the crack movements. An example of this stress-absorbing layer is the geosynthetic material. There are many types of geosynthetic materials available, and most of them claimed to be effective in mitigating reflection cracks. However, the construction procedures have to be properly looked into to ensure that the geosynthetic materials are laid in accordance to the manufacturer's specifications. There are basically two types of geosynthetic Cawangan Jalan, Ibu Pejabat JKR, K.L

materials available in the market, the grid and the non-woven geotextiles. When using the grid, care should be taken to reduce the possibility of the picking up or stretching the grid by lorry tyres. When this happens, the grids will warp and the resultant displacement of the grids will lead to poor compaction of the asphalt layer. This leads to cracking. On the other hand, if the non-woven materials are used, care should be taken on the amount and type of tack coat used. If used in excess, the nonwoven material will become saturated and will lead to bleeding. If the bitumen tack coat is too soft the material can slide at the exsiting road/material interface. Other types of Stress Absorbing Membrane Interlayers (SAMI) are also available. These can be in the forms of aggregate interlayers (e.g. surface dressings) or modified bitumen with or without chippings. At 1KRAM studies are being carried out on the use of some of these interlayers. Laboratory experiments are also being carried out on the manufacture of SAMIs using natural rubber blended into bitumen. Crushed aggregates have also been used as an interlayer. This method has perform positively even with crack movements of l.5mm. In one of the trials constricted by IKRAM, the crushed aggregates were laid on top of segmented concrete pavement where the movements at the joints were substantial. Previously, asphalt overlays without prior treatment Nvould only last about 2 months. But with this method, the cracks from the concrete.joints have vet to come through after a couple of years. Resurfacing on Rutted Surfaces Resurfacing ou existing pavements with surface nits require special considerations. Dense bituminous surfacings nit when it loses its stability properties. These usually occur in areas where there are prolonged loading periods of slow moving or stopped heavy vehicles, namely at climbing lanes and at intersections. The high stresses imposed on the asphalt layer causes it to densify and with the reduction in Page 73

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Interim Guide To Evaluation And Rehabilitation Of Flexible Road Pavements. If the existing pavement surface which needs strengthening is suffering from bleeding, it is advisable to consider the possibility of the excess bitumen migrating into the new layer. The application of hot sand should be considered. Resurfacing on Corrugated Surface If corrugations are the result of unstable surfacing materials, it should be replace before resurfacing. If it is due to unstable granular pavement layers then partial reconstruction will be a better solution. Resurfacing on Ravelling or Weathered Surfaces If the existing surface is experiencing ravelling and loss of aggregates, no pre-treatment is necessary.

voids in the mix, the mix becomes unstable. This layer must be removed by milling prior to overlaying it with a fresh asphalt layer. Bituminous mixes designed by the Marshall method have been shown to perform poorly in high stress areas. To counter this, polymer modified bitumen can be used in asphaltic concrete on climbing lanes and junctions. The rate of rutting of these mixes are slower than the normal asphaltic nixes. However, the use of the polymer modified bitumen can increase the cost of the asphalt to double its normal cost. In an effort to find a cheaper solution to the above problem, IKRAM has introduced a new mix for the surfacing, called the HCM Bituminous Surfacing. The mix was tried in a trial at the Bukit Tinggi climbing lanes along the Kuala Lumpur - Karak Highway. In the same trial, other mixes using polymers and additives were also tried. After nearly 3 years in service, the HCM Bituminous Surfacing has performed on par to the more expensive polymer modified wearing courses. Resurfacing on Bleeding Surface

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Cost : A major portion of the cost in carrying out a structural resurfacing job goes to the pretreatment works. The cost of the asphaltic concrete itself is around RM 10.00 per square metre, whilst the costs of pre-treatment such as the use of grid geosynthetic materials may push the cost up by between RM 8.00 to RM 20.00 per square metre. The use of fabric geosynthetic materials would reduce the total construction cost as the fabrics may add about 30-40% more to the cost. Reliabilitv : Structural resurfacing can last the design life if proper pre-treament work is carried out. Most of the resurfacing works which show early signs of distress are due to improper pre-treatment works. 5.5 RECONSTRUCTION Description: Reconstruction is the removal and rebuilding of all (including subgrade) or part of the road pavement using fresh material and new construction specifications. Pavements that have failed Beverly are usually those where deterioration has been allowed to occur without maintenance. The condition of thee Page 74

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Plate 5.8. Reconstruction Works

Plate 5.9. Recycling For Base

lower granular layers of the pavement is best determined by destructive testing. There are two types of reconstruction, namely, full reconstruction and partial reconstruction. Full reconstruction is needed when the subgrade layer as well as the pavement layers has deteriorated beyond repair. In full reconstruction, the rebuilding includes the subgrade. Partial reconstruction is needed when the road base has been contaminated and it has lost its inherent stability. In this case the rebuilding does not include the subgrade. In the case where the failure of the road base is extensive and conventional partial reconstruc Cawangan Jalan, Ibu Pejabat JKR, K.L

tion method is uneconomical, it is advisable to carry out recycling. Recycling of the road base is a partial reconstruction alternative where the existing surfacing and/or part of the road base is pulverised, and replaced as a new road base layer. The process breaks up the existing asphalt layer into small pieces thereby removing existing cracks and at the same time allowing addition of road base thickness. It therefore can be used to eliminate reflective cracking problems and correct thickness deficiencies. Base recycling is suitable where the deterioration of the surfacing has become so extensive that partial reconstruction option will not be economical. The deterioration can be due to a Page 75

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poor road base layer or insufficient base thickness. Additional aggregates and stabilisers can be included in the mix to improve its performance. Among the common stabilisers suitable for base recyling are :

areas: Identifying full reconstruction Full reconstruction may be needed for the following combination of failures. i)

i) cut-back bitumen ii) cement iii) bitumen emulsion The correct choice of stabilisers will depend on the existing pavement material type, its condition and compositions. Condition or Use : Identifying areas needing reconstruction requires evaluation of the pavement conditions. However, experience has shown that the following rule-of-thumb to be reasonably acceptable in identifying localised reconstruction

Pavement surface which suffer from crocodile cracks with rut depths of more than 25 mm, without shoving. ii) Pavement surface which suffers crack ing with rut depth of more than 15 mm and deep shoving. Identifying partial and base reconstruction Partial reconstruction may be needed for the following failures or combination of failures. i)

Spalling and crocodile cracking with rut depth of less than 15 mm. ii) Shoving with rut depth less than 15 mm.

Figure 5.7. Full Reconstruction

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iii) Crocodile cracking with block size less than 100 mm with shoving.

able and can be expensive. The works involved in base recycling are:

Confirmatory test using the Dynamic Cone Penetrometer (DCP)

Pulverisation or ripping

If the site engineer is not certain of the extent of reconstruction required, the DCP can be used to estimate the pavement layer strength and thus identify which materials needs to be removed. Partial reconstruction can be carried out if it is not necessary to replace the subgrade or the sub-base.

Mechanical pulverisors can break up any of the the pavement layer and reduce it to uniform sizes. The pulverised materials should be inspected where all large pavement chunks and organic substances should be removed. Addition of stabilisers may_ be introduced at this stage. Stabiliser distribution

Construction : Reconstruction requires more lane closure time than resurfacing, since the work includes breaking up the pavement, removal and rebuilding of existing layers. The time taken for a partial reconstruction is less than that for the full reconstruction. Allowances should be made for the possibility of secondary compaction of the reconstructed areas by opening them to traffic for a period of time before applying the final overlay. Particular attention should be given to the provision of adequate drainage when reconstructing roads with high water table. Marking the areas to be reconstructed Marking of the areas to be reconstructed is best done a few days before construction. Temporary marking can be used if contruction is to follow immediately otherwise permanent marking can be carried out. It is advisable to extend the area needing reconstruction beyond the area over which it occurs. Marking is best carried out by experienced personnel in identifying serious pavement defects. This task is critical in optimising the probability of success of the rehabilitation job. Construction of Base Recycling

Cement stabilisers can be spread by a bulk spreader or manually depending on the job size. The spread rate, water content and mixing process is critical for efficient stabilisation. Bituminous stabilisers are mechanically spread and are seldom used for base recycling. Compaction Compaction can be carried out using normal vibratory rollers. The number of roller passes is critical, as over-compacting cement stabilised base may overstress the surface. Bitumen stabilised road base do not have this problem.

Cost : Reconstruction is an expensive option and should be considered only if the pavement has suffered beyond economic repair. Partial reconstruction can cost between RM 35.00 to RM 45.00. Full reconstruction is more costly. It can range between RM 40.00 to RM 50.00. Reliability : Reconstruction work done to a high construction standard will have a life surpassing all other rehabilitation options. In fact, it can be designed to any desired performance period. However, it is expensive and should only be carried out where necessary.

The construction ol` recycled stabilised base normally requires specialised machinery. Standard construction method may not be suitCawangan Jalan, Ibu Pejabat JKR, K.L

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