AP-T249-13 Enrobes a Module Eleves

AP-T249-13

AUSTROADS TECHNICAL REPORT

EME Technology Transfer to Australia: An Explorative Study


Published October 2013

© Austroads Ltd 2013

This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without the prior written permission of Austroads.

ISBN 978-1-925037-23-4

Austroads Project No. TT1353

Austroads Publication No. AP-T249-13

Project Manager Paul Morassut

Roads and Maritime Services NSW

Prepared by Dr Laszlo Petho and Dr Erik Denneman

ARRB Group

Acknowledgements Thanks to Melissa Dias, Robert Urquhart, Shannon Malone, Shannon Lourensz

and Elizabeth Woodall of ARRB Group for their assistance with the experimental work and helpful discussions during the project. The authors wish to acknowledge the

assistance of members of the Asphalt Research Working Group (ARWG) that readily shared their expertise and contributed in many other ways.

Published by Austroads Ltd Level 9, Robell House 287 Elizabeth Street

Sydney NSW 2000 Australia Phone: +61 2 9264 7088

Fax: +61 2 9264 1657 Email: [email protected]

www.austroads.com.au

Austroads believes this publication to be correct at the time of printing and does not accept responsibility for any consequences arising from the use of information herein. Readers should

rely on their own skill and judgement to apply information to particular issues.

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Sydney 2013

About Austroads Austroads’ purpose is to:

promote improved Australian and New Zealand transport outcomes

provide expert technical input to national policy development on road and road transport issues

promote improved practice and capability by road agencies.

promote consistency in road and road agency operations. Austroads membership comprises the six state and two territory road transport and traffic authorities, the Commonwealth Department of Infrastructure and Regional Development, the Australian Local Government Association, and NZ Transport Agency. Austroads is governed by a Board consisting of the chief executive officer (or an alternative senior executive officer) of each of its eleven member organisations:

Roads and Maritime Services New South Wales

Roads Corporation Victoria

Department of Transport and Main Roads Queensland

Main Roads Western Australia

Department of Planning, Transport and Infrastructure South Australia

Department of Infrastructure, Energy and Resources Tasmania

Department of Transport Northern Territory

Territory and Municipal Services Directorate Australian Capital Territory

Commonwealth Department of Infrastructure and Regional Development

Australian Local Government Association

New Zealand Transport Agency.

The success of Austroads is derived from the collaboration of member organisations and others in the road industry. It aims to be the Australasian leader in providing high quality information, advice and fostering research in the road transport sector.


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SUMMARY

Road agencies and the road construction industry face the challenge of designing and delivering high performance asphalt materials to meet the demands of increasing traffic intensity and axle loadings. This study focuses on EME (enrobés à module élevé) mix technology, which was developed in the mid-seventies in France and provides a high performance asphalt material for use in heavy duty pavements, specifically suitable in the following situations:

pavements carrying large volumes of heavy vehicles and requiring strengthening to protect underlying layers

where there are constraints to the allowable pavement thickness, especially in urban areas or motorways, where geometric constraints persist

heavily trafficked areas, such as slow lanes, climbing lanes, bus lanes and airport pavements, where there is a need for increased resistance to permanent deformation.

EME has a very good resistance to permanent deformation combined with a very high stiffness, well in excess of that of standard mixes used in base layers, especially at elevated temperatures. EME mixes also have a good resistance to fatigue due to the high binder content of the mix.

Based on an international literature review, the historical development and performance of EME was examined. With the co-operation of the asphalt industry, the availability in Australia of the required materials, such as suitable aggregates and hard penetration grade bitumen, was investigated. By using locally available constituent materials, a laboratory-based demonstration project was undertaken to provide insight and guidance for EME mix design. The mix design of EME differs from mix design approaches typically used in Australia in that it is strictly based on performance-related testing. The explorative laboratory testing performed as part of this study provides an understanding of the complex nature and requirements of the EME mix design process.

The laboratory program carried out in the work included the characterisation of EME trial mix designs with respect to the following performance-related parameters:

workability with hard grade binders

moisture sensitivity (durability)

rutting resistance

stiffness properties

fatigue resistance, derived from three different strain levels to characterise the slope of the fatigue curve.

In France, EME is designed and tested according to the European test series EN 12697, and specification requirements are set according to these test methods. The need to identify specification limits based on locally available test methods is highlighted in the work. If EME is to be successfully introduced into Australia, the development of local specifications will need to be addressed in future research. The benefits of high modulus asphalt application can be shown by means of pavement response analysis; this issue is also highlighted in the report.


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CONTENTS 1 INTRODUCTION ................................................................................................................... 1 1.1 Objectives .............................................................................................................................. 1 1.2 Structure of the Report ........................................................................................................... 2

2 HEAVY DUTY ASPHALT IN AUSTRALIA ............................................................................ 3

3 DEVELOPMENT OF HIGH MODULUS ASPHALT CONCRETE IN FRANCE ...................... 6 3.1 Development of Testing Methodology in France .................................................................... 7 3.2 Pavement Design Considerations .......................................................................................... 8 3.3 Manufacturing of EME and Practical Considerations for Construction in France .................... 9 3.4 A Case Study from France ................................................................................................... 10 3.5 Design Properties of EME in France .................................................................................... 14

3.5.1 Binder Content and Richness Modulus ..................................................................... 14 3.6 Performance-based Mix Design of EME .............................................................................. 15

3.6.1 Level 1 Testing ......................................................................................................... 15 3.6.2 Level 2 Testing ......................................................................................................... 16 3.6.3 Level 3 and Level 4 Testing ...................................................................................... 16

3.7 Requirements for Constituent Materials ............................................................................... 17 3.7.1 Binder Types used in EME ....................................................................................... 17 3.7.2 Aggregate Grading of the EME ................................................................................. 18 3.7.3 Aggregate Requirements .......................................................................................... 21 3.7.4 Richness Modulus .................................................................................................... 23

4 OTHER INTERNATIONAL APPLICATION OF EME MIXES ............................................... 25 4.1 Experience in the United Kingdom ....................................................................................... 25 4.2 South Africa ......................................................................................................................... 26

5 EXPERIMENTAL PROGRAM – EME MIX DESIGN ............................................................ 28 5.1 Binder Test Results.............................................................................................................. 28

5.1.1 Brookfield Test ......................................................................................................... 28 5.1.2 Determination of Binder Viscosity Ranges for Mixing and Compaction ..................... 30 5.1.3 Preliminary DSR Test – Strain Sweep Test .............................................................. 30 5.1.4 DSR Test – Temperature-Frequency Sweep Test .................................................... 32

5.2 Aggregate Test Results ....................................................................................................... 36 5.2.1 Test Methods ............................................................................................................ 36 5.2.2 Test Results ............................................................................................................. 36

5.3 Mix Design Procedure – Trial Mixes ..................................................................................... 37 5.4 Mix Design Procedure – Performance of the Trial Mixes ...................................................... 39

5.4.1 Rut Resistance ......................................................................................................... 39 5.4.2 Flexural Modulus ...................................................................................................... 39 5.4.3 Fatigue Resistance ................................................................................................... 39 5.4.4 Moisture Sensitivity................................................................................................... 41 5.4.5 Test Results Summary ............................................................................................. 42

6 SUMMARY AND CONCLUSIONS ...................................................................................... 49 6.1 Summary ............................................................................................................................. 49 6.2 Conclusions ......................................................................................................................... 51

REFERENCES ............................................................................................................................. 52 APPENDIX A APPEARANCE OF THE SURFACES – MOISTURE SENSITIVITY

TEST SAMPLES ................................................................................................. 55


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TABLES Table 2.1: Heavy duty asphalt specification, VicRoads ............................................................. 3 Table 2.2: Heavy duty asphalt specification, TMR ..................................................................... 4 Table 2.3: Heavy duty asphalt specification, RMS .................................................................... 5 Table 3.1: Properties of as constructed EME with hard grade bitumen ..................................... 9 Table 3.2: Geotechnical characteristics of the aggregates ...................................................... 10 Table 3.3: Binder test results .................................................................................................. 11 Table 3.4: Results of the gyratory test ..................................................................................... 12 Table 3.5: Complex modulus and fatigue test results, the effect of aggregates ....................... 13 Table 3.6: Requirements for richness modulus for AC-EME ................................................... 14 Table 3.7: Testing levels and requirements for AC-EME ......................................................... 15 Table 3.8: Level 1 requirements for AC-EME .......................................................................... 16 Table 3.9: Level 3 and level 4 requirements for AC-EME ........................................................ 16 Table 3.10: The requirements of hard penetration grade binders .............................................. 17 Table 3.11: Overall limits of target composition – basic sieve set plus set 2 .............................. 18 Table 3.12: Grading control points for AC20-EME .................................................................... 19 Table 3.13: Grading control points for AC14-EME .................................................................... 19 Table 3.14: Grading control points for AC10-EME .................................................................... 19 Table 3.15: Requirements for fillers .......................................................................................... 21 Table 3.16: Requirements for aggregates ................................................................................. 22 Table 3.17: Input values into the calculation of K for AC20-EME, AC14-EME and

AC10-EME ............................................................................................................. 23 Table 3.18: Typical binder contents for EME application at different aggregate

densities and richness factors ................................................................................ 24 Table 4.1: Interim performance specifications for EME Class 1 and 2 basecourses

in South Africa ........................................................................................................ 26 Table 5.1: Brookfield viscosity results for EME binders ........................................................... 28 Table 5.2: Specifications for hard paving grade bitumens according to EN 13924-2006 ......... 29 Table 5.3: Calculated temperature values based on viscosity requirements ........................... 30 Table 5.4: Aggregate grading and density information ............................................................ 36 Table 5.5: Components of aggregate blends .......................................................................... 38 Table 5.6: Combined grading trial blends ................................................................................ 38 Table 5.7: Trial binder contents ............................................................................................... 39 Table 5.8: Comparison of EN 12697-24, method A and AGPT/T233 for performing

fatigue characterisation test.................................................................................... 40 Table 5.9: Comparison of EN 12697-12 and AGPT/T232 for performing moisture

sensitivity test ......................................................................................................... 41 Table 5.10: Performance testing ............................................................................................... 42 Table 5.11: Performance test results ........................................................................................ 43 Table 5.12: Volumetric properties ............................................................................................. 44 Table 5.13: Test results of fatigue testing (18 beams) ............................................................... 46 Table 5.14: Stripping potential according to AGPT/T232 ........................................................... 48 Table 5.15: Water sensitivity according to EN 12697-12 and EN 12697-23 .............................. 48


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FIGURES

Figure 3.1: Selected grading curve ........................................................................................... 11 Figure 3.2: Wheel-tracking test results ..................................................................................... 13 Figure 3.3: Visualisation of hard penetration grade binder requirements .................................. 17 Figure 3.4: Grading control points for AC20-EME .................................................................... 20 Figure 3.5: Grading control points for AC14-EME .................................................................... 20 Figure 3.6: Grading control points for AC10-EME .................................................................... 21 Figure 5.1: Brookfield viscosity results for different binder types .............................................. 30 Figure 5.2: G* ratio, strain sweep B1973 binder, 35 °C ............................................................ 31 Figure 5.3: G* ratio, strain sweep B2316 binder, 35 °C ............................................................ 31 Figure 5.4: G* ratio, strain sweep B1973 binder, 60 °C ............................................................ 31 Figure 5.5: G* ratio, strain sweep B2316 binder, 60 °C ............................................................ 31 Figure 5.6: Frequency-temperature sweep of B1973 – set 1 .................................................... 32 Figure 5.7: Frequency-temperature of B1973 – set 2 ............................................................... 33 Figure 5.8: B1973, set 1 and set 2 test results correlation ........................................................ 33 Figure 5.9: Frequency-temperature sweep of B2316 – set 1 .................................................... 34 Figure 5.10: Frequency-temperature sweep of B2316 – set 2 .................................................... 34 Figure 5.11: B2316, set 1 and set 2 test results correlation ........................................................ 35 Figure 5.12: Master curve of different binders at 45 °C .............................................................. 35 Figure 5.13: Trial grading curves ................................................................................................ 38 Figure 5.14: Flexural modulus frequency sweep results ............................................................. 44 Figure 5.15: Wheel-tracker results ............................................................................................. 45 Figure 5.16: Preliminary fatigue results, mix design, trial phase ................................................. 45 Figure 5.17: Fatigue line of the EME mix.................................................................................... 47


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1 INTRODUCTION With the ever increasing traffic intensity and axle loadings, the state road agencies and the road construction industry face the challenge of designing and delivering high performance asphalt materials to meet these increasing demands. As part of Austroads project TT1353 Asphalt properties and mix design procedures a demonstration study was conducted in 2012–13 to investigate the potential transfer of French high modulus hot mix asphalt technology, known as enrobés à module élevé (EME) to Australia. EME was developed in the mid-seventies in France and provides a high performance asphalt material for use in heavy duty pavements, specifically suitable in the following situations:

pavements carrying large volumes of heavy vehicles and requiring strengthening to protect underlying layers

where there are constraints to the allowable pavement thickness, especially in urban areas or motorways, where geometric constraints persist


The EME technology is predominantly used for structural asphalt layers, i.e. base and intermediate layers, which are referred to as foundation and base layer in the French terminology.

1.1 Objectives This work is an initial exploration study and the main objective is to provide insight and guidance for EME mix design, which is different to mix design approaches widely used in Australia. Project TT1353 is a six-year program, with 2012–13 being the final year; therefore, any work required for a complete technology transfer will be covered by other research projects.

The objectives of this study can be summarised as follows:

investigate the design methodology of EME asphalt mix, based on available international literature

investigate requirements and availability of aggregate type, aggregate grading, and hard penetration grade binder

provide input for implementation of the EME technology in Australia

provide a comprehensive characterisation of EME mix using Australian test methods, including workability, moisture sensitivity, rutting resistance, stiffness and fatigue resistance.

The following topics are out of scope for this study:

investigate the application of highly modified asphalt, which is produced with modified binder containing a high percentage of polymer

develop specification limits; they should be developed and verified under field conditions in future validation trials

provide comprehensive pavement design considerations; this work would require performance monitoring of trial sections, which is out of scope for the current study.

The information collected and provided in this study will form the basis of the complete technology transfer conducted in subsequent years.


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1.2 Structure of the Report In Section 2 the Australian heavy duty asphalt applications are discussed in the context of volumetric and performance requirements. Section 3 provides a summary of the historical development and performance requirements of EME in France, including design methodology, specification requirements and test methods. A review of other international experiences and successful technology transfers are discussed in Section 4. An experimental laboratory program is provided in Section 5, where the complex nature of the EME mix design is discussed; Section 5 also provides a comparison of relevant European and Australian test methods. Section 6 contains the summary and provides conclusions for further work required for a complete and successful technology transfer.


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2 HEAVY DUTY ASPHALT IN AUSTRALIA In Australia, several jurisdictions have specifications for heavy duty asphalt. Some of these specifications require testing of empirical properties, some of them require performance-based testing, but none of them are fully performance based. A summary of the heavy duty asphalt applications is provided in Table 2.1 for VicRoads, in Table 2.2 for TMR and in Table 2.3 for RMS. Currently, none of the jurisdictions have a specification for high modulus asphalt.

Table 2.1: Heavy duty asphalt specification, VicRoads

Property SI 14 mm SI 20 mm SF 20 mm SP 20 mm SG 20 mm SS 20 mm Lower limit

Upper limit

Lower limit

Upper limit

Lower limit

Upper limit

Lower limit

Upper limit

Lower limit

Upper limit

Lower limit

Upper limit

Grading 26.5

100

100

100

100

100

AS sieve (mm)

19

100 90 100 90 100 90 100 90 100 90 100 13.2 85 100 75 88 75 88 75 88 75 88 75 88 9.5 70 84 61 75 61 75 61 75 61 75 61 75 6.7 59 73 49 64 49 64 49 64 49 64 49 64 4.75 48 65 41 55 41 55 41 55 41 55 41 55 2.36 32 48 27 41 27 41 27 41 27 41 27 41 1.18 22 37 18 33 18 33 18 33 18 33 18 33 0.6 18 28 12 25 12 25 12 25 12 25 12 25 0.3 10 22 8 19 8 19 8 19 8 19 8 19 0.15 6 14 5 13 5 13 5 13 5 13 5 13 0.075 4 7 3 6 3 6 3 6 3 6 3 6

Binder type C320 C320 C320 A10E M600/170 C600

Air voids range (%) 4.9 to 5.3 4.9 to 5.3 4.9 to 5.3 4.9 to 5.3 4.9 to 5.3 4.9 to 5.3

Stability, minimum (kN) 6.5 6.5 6.5 6.5 6.5 6.5 Flow (mm) 1.5 to 3.5 1.5 to 3.5 1.5 to 3.5 1.5 to 3.5 1.5 to 3.5 1.5 to 3.5

Voids in the mineral aggregate (VMA) (%) 16 15 15 15 15 15

Sensitivity to water, minimum (%) N/A 80 N/A N/A N/A 80

Indirect tensile resilient modulus (MPa) 3500 to 7000 3500 to 7000 3000 to 7000 N/A 3500 to 7000 3500 to 7000

Dynamic creep (2% strain) (pulses) N/A 50 N/A 3 30 30

Gyratory compaction curve – Air voids at 250 cycles (%)

2.5 2.5 N/A 1.5 2.5 2.5

Wheel tracking, final rut depth, maximum (mm) N/A 9 N/A 5 6 6

Source: VicRoads (2012).


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Table 2.2: Heavy duty asphalt specification, TMR

Property DG14HS DG14HP DG20HM Lower limit Upper limit Lower limit Upper limit Lower limit Upper limit

Grading 26.5

100 100

AS sieve (mm)

19 100 100 100 100 90 100 13.2 90 100 90 100 72 86 9.5 68 82 68 82 60 76 6.7

4.75 42 58 42 58 41 58 2.36 28 42 28 42 28 42 1.18 19 31 19 31 19 31 0.6 13 23 13 23 13 23 0.3 9 17 9 17 9 17 0.15 6 11 6 11 6 11 0.075 4 7 4 7 4 7

Minimum effective binder volume (%) 10 10 9

Maximum effective binder volume (%) 11.5 11.5 –

Free binder volume (%) min. 5.5 5.5 5.0 to 7.0

Permeability (μm/s) ≤ 15 ≤ 15 ≤ 15

Texture depth (mm) 0.4 0.4 N/A

Binder type A5S A5S Class 600

Air voids in the compacted mix (design mix) (%) 4.5 to 5.5 4.0 to 5.0 4.1 to 5.1

Stability, minimum (kN) 7.5 7.5 7.5

Flow, minimum (mm) 2.0 2.0 2.0

Stiffness, minimum (kN/mm) 2.0 2.0 2.0

Voids in the mineral aggregate (VMA) (%) 13.5 to 17.5 13.0 to 17.0 12.5 to 16.5

Voids filled with binder (VFB) (%) TBR TBR 58 to 78

Air voids in the compacted mix (%) 3.0 to 7.0 2.5 to 6.5 TBR

Maximum density (t/m³) TBR TBR TBR

Sensitivity to water, minimum (%) 8 80 80

Indirect tensile resilient modulus (MPa) TBR TBR 5000

Dynamic creep (2% strain), minimum (pulses) TBR TBR TBR

Gyratory compaction curve – air voids at 250 cycles (%) 2 TBR TBR

Rut rate (maximum) (mm/kcycle) 0.3 0.3 0.3

Final rut depth (mm) 4.0 4.0 4.0

Minimum air voids of production mix (%) 3.0 2.5 2.6

Source: Department of Transport and Main Roads (2011).


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Table 2.3: Heavy duty asphalt specification, RMS

Property AC14 AC20 AC28 Lower limit Upper limit Lower limit Upper limit Lower limit Upper limit

Grading 37.5 100 100

AS sieve (mm)

26.5 100 100 80 98 19 100 100 80 98

13.2 80 98 65 93 50 80 9.5

6.7 55 80 45 70 35 60 4.75 2.36 25 45 20 40 15 40 1.18 0.6 10 30 5 25 5 25 0.3 0.15 0.075 2 8 2 8 2 7

Binder content (% by mass of total mix) 4.8 to 6.2 4.6 to 6.1 4.0 to 5.8

Voids in the mineral aggregate (VMA) (%) ≥ 15 ≥ 14 ≥ 13

Sensitivity to water (%) ≥ 80 ≥ 80 ≥ 80

Indirect tensile resilient modulus (MPa) TBR TBR TBR

Wheel tracking, final rut depth (mm) TBR TBR TBR

Source: Roads and Maritime Services (2012).


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3 DEVELOPMENT OF HIGH MODULUS ASPHALT CONCRETE IN FRANCE

The first high modulus hot mix asphalt appeared in France in the mid-seventies, and was called enrobés à module élevé (EME), which translates to high modulus asphalt. The first mixes were based on the association of coal tar and polyvinylchloride; they are not used any longer. Although these mixes gave good performance, in the early eighties the second generation high modulus asphalt, using hard grade bitumen or additives, was introduced and the amount of such material laid in the road pavements is considerable. There are three main areas where the construction of high modulus asphalt is considered in France:

pavements carrying very heavy traffic and requiring strengthening

where there was a need for reduction in pavement thickness, especially in urban areas or motorways, where geometric constraints existed; it has successfully applied on slow lanes, climbing lanes, bus lanes and other heavy trafficked areas

where there is a need for high resistance to permanent deformation.

It should be noted that according to the French legislation the maximum axle load is 130 kN (Serfass, Bense & Pellevoisin 1997).

In France, the minimum binder content was based on the concept of richness factor, which relates to the thickness of the bitumen film (see Section 3.5.1). During the early development stages, the French practice already distinguished between two categories on the basis of their richness factor:

Richness factor > 3.2 (rich mix), thus a high binder content; mixes of this category exhibit not only high moduli, but also good resistance to fatigue.

Richness factor between 2.5 and 3.2 (lean mix), thus a low binder content; mixes of this category show high moduli, but their resistance to fatigue is limited (Serfass, Bauduin, & Garnier 1992).

The minimum richness of 3.2 for rich mixes was used in the early development phase and it is today accepted as a minimum of 3.4 (Delorme, Roche & Wendling 2007). The EME mix has the following properties:

The resistance to permanent deformation is high, far beyond that of standard mixes used in base layers.

High dynamic modulus; when tested at 10 Hz, 15 °C, a minimum dynamic modulus 14 000 MPa must be achieved, when using the two-point bending test method (EN 12697-26, Annex A).

At rapid cooling and/or low temperatures, thermal cracking is a possible failure of the EME mix due to the high modulus. Early experiences showed that no thermal cracking occurred, if the EME mix was covered with an asphalt wearing course, even if this layer was very thin. It should also be noted that the French climate is considered temperate, therefore this issue should always be locally addressed based on local weather information.

EME mixes are considered to have fairly good resistance to fatigue, with allowable strain at one million load applications ranging from 120 to 150 microstrain, tested according to EN 12697-24, Annex A (two-point bending test on trapezoidal shaped specimens). These values are significantly higher than the requirements for standard road base mix at 90 microstrain. The good fatigue response can be explained by the high binder content adopted for the mix (Serfass, Bauduin & Garnier 1992). Note that it is not possible to make a direct comparison to Australian four-point bending test results.


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High modulus asphalt could be designed and constructed for basecourse, binder course and wearing course applications; however, this report investigates only the basecourse application, and findings from the report cannot be directly translated into binder course and wearing course applications due to the complex requirements of pavement layers.

In the early stages SBS, modified binders were also considered in EME applications (Serfass, Bauduin & Garnier 1992). According to the latest version of available literature in 2012, the applied binder is predominantly hard grade binder; however, polymer modification can also be considered to increase the fatigue resistance (Delorme, Roche & Wendling 2007).

3.1 Development of Testing Methodology in France According to the early French method as described by Serfass, Bense and Pellevoisin (1997), preliminary mix design consists of evaluating the mix compactibility, using the gyratory compacting machine and determining the unconfined compressive tensile strength. During this first step, several parameters may vary (grading curve, binder content, etc.).

At the end of the first step, one or more pre-optimised mix formulas are selected. A rutting resistance test is then performed on these mixes; based on the results, adjustments are made to the mix composition. In this early development stage, unconfined compressive stress (UCS) was also measured at different temperatures; however, this type of test is not in use anymore.

As a final step, the complex moduli and fatigue resistance of the optimised mix are performed through dynamic bending tests (Serfass, Bauduin & Garnier 1992). Section 5 provides more details about the mix design procedure of EME mixes.

Based on French experience, the binder content of EME mixes typically ranges between:

5.5 and 6.2 mass per cent by weight of mineral aggregate for richness factor higher than 3.2

4.0 and 5.4 mass per cent by weight of mineral aggregate for richness factor between 2.5 and 3.2 (Serfass, Bense & Pellevoisin 1997).

Water sensitivity was not considered in the early stages according to Serfass, Bauduin and Garnier (1992); evaluation of water sensitivity (the Duriez-LCPC method) was introduced at a later stage, as reported by Serfass, Bense and Pellevoisin (1997). As expected, it was found that rich mixes are much less sensitive to water treatment than lean mixes.

The results of the wheel-tracking test showed that the resistance of EME mixes to plastic deformation was extremely high. It was also found that the rutting resistance varied only slightly with the richness factor, i.e. the bitumen content did not have a significant impact on this property (Serfass, Bense & Pellevoisin 1997). In this respect EME significantly differs from classical hot mix asphalt mixes (HMA).

The type of grading curve and the binder characteristics and content will depend on:

the design thickness of the layer

the properties of the aggregate (shape, angularity, internal friction)

the design requirements for the road pavement (stiffness, fatigue).

It is important to achieve a high voids in mineral aggregate (VMA) in the mix to accommodate high binder content.


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3.2 Pavement Design Considerations The approach to pavement structural design applied by French road agencies in the 1970s was to provide a catalogue system, in order to establish a uniform strategy on the national level, while sparing labour-intensive calculations for design engineers. This solution did not provide the complex explanations of the rules followed in the pavement design and the catalogues provided only the input data. However, in the 1990s the need arose to provide a document which explained the mechanistic pavement design approach; the development of the document was initiated by the following considerations:

ensuring diversification of performance classes

provide a single approach to the technical questions, in order to preserve the unity of the concepts applied in France and provide a common tool that would allow an objective assessment of the solution proposed by supervisors and contractors

enable innovation; maintaining a list of acceptable technical solutions would make it impossible to take advantage of innovations

the computing power needed for the application of a rational pavement design method became available everywhere.

The gradually developed French rational approach was published in the French design manual for pavement structures (Laboratoire Central des Ponts et Chausees 1997) and it communicates the fundamentals of the French approach. However, the guide does not provide instructions for the selection of the basic parameters; it is the responsibility of the road agency to choose appropriate values in line with the asset management strategy.

According to the French design manual, the working stress values in the pavement layers are determined from material fatigue behaviour characteristics, cumulative traffic and calculated risk. The variability of the mechanical characteristics of the pavement material is considered to be maintained within relatively narrow limits, when the material is manufactured and laid in compliance with the standards and directives. Risks are determined in accordance with fatigue behaviour and thickness variability. In the design system the lack of uniformity of the supporting layers is also considered through the application of factors; the reliability factors are introduced as a function of the bearing capacity of the subgrade.

The pavement design system and the material characterisation requirements in the standards and directives cannot be separated in France; the advantage of EME application can be realised through a general mechanistic pavement design (GMP) approach. In Australia, a GMP is widely accepted and utilised (Austroads 2012), therefore an important key for a successful technology implementation is provided. However, the transfer functions and risk assessment techniques are different in the Australian and French methodology; it is crucial to develop locally valid transfer functions for EME applications. This would require performance monitoring of trial sections, which is out of scope for the current study. This systematic approach is necessary for a successful technology transfer to Australia.


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3.3 Manufacturing of EME and Practical Considerations for Construction in France

Manufacturing EME with hard grade binder simply requires higher temperatures than classical mixes due to the higher viscosities of the binder. According to early experience, the laying of EME is not considered difficult, provided that temperature requirements are complied with. However, compaction of EME is a key issue, as a high degree of compaction is necessary to achieve the design properties of the mix. Heavy rollers have to be employed; according to the experience both pneumatic-tyred and vibratory steel wheeled rollers are considered suitable (Serfass, Bauduin & Garnier 1992).

According to Serfass, Bense and Pellevoisin (1997), EME manufactured with very hard grade bitumen reached the degree of compaction as summarised in Table 3.1.

Table 3.1: Properties of as constructed EME with hard grade bitumen

Location Thickness (mm)

Degree of compaction C (%)

East-West Highway Pau (Pyrénées Atlantiques) 120 97.7–98.5

RN83 - Besancon (Doubs) 90 95.2–97.6

RD700 - S Brieuc (Cotes d'Armor) 160 97.7–99.0

Source: Serfass, Bauduin and Garnier (1992). The values outlined in Table 3.1 are significantly higher compared to conventional dense graded asphalt mixes. According to the French practice the degree of compaction of a mix is defined according to Equation 1:

𝐶(%) = 100𝐷𝑐𝐷𝑚

1

where

𝐷𝑐 = the actual bulk density of compacted mix

𝐷𝑚 = the theoretical maximum density of the mix (no air voids)

Care should be exercised while designing and placing thin layers of EME on top of unbound base layers, where low modulus can be expected. Low bearing capacity in the lower layers may result in high strains in the EME layers, which leads to early fatigue failure (Serfass, Bauduin & Garnier 1992). Also, without sufficient support from the lower layers it is not possible to achieve an adequate level of compaction of the EME layer, which leads to a situation where the target mechanical properties cannot be achieved (Serfass, Bense & Pellevoisin 1997). Also, improper bonding between asphalt layers can lead to premature distress through increased strains in the structural asphalt layer.

To provide a good support, a very rigid sub-base layer seems to be practical. However, care should be taken when placing EME directly on top of rigid cement treated layers as shrinkage cracks tend to reflect rapidly in the EME layers. A minimum thickness of asphalt layers should be selected in order to avoid reflective cracking; the thickness should be defined on local experiences. If cement treated sub-base is not used, it is crucial that the pavement layers are carefully selected to ensure a balanced pavement structure which provides sufficient support for EME layers.


A u s t r o a d s 2 0 1 3

— 10 —

Very heavy pneumatic-tyre rollers that weigh up to 45 tonnes are often used to compact EME to a level where it cannot be further compacted and is therefore resistant to rutting by traffic (Sanders & Nunn 2005). It can be seen that this approach does not allow any post-compaction after trafficking.

The selection between rich and lean EME is based on the consideration of the situation of the pavement structure. If the existing pavement, which requires strengthening, has lower deflections, or the base layers of the newly constructed pavement are able to provide adequate support (consequently lower induced strains) it is not necessary to aim for a rich EME with a higher fatigue resistance. These considerations should certainly be based on pavement design and economic considerations; however, it is envisaged that lean EME mixes would provide similar performance to heavy duty mixes already used in Australia.

EME with a richness factor above 3.2 is easier to compact and lower air voids can be obtained than for mixes with a richness factor between 2.5 and 3.2.

Serfass, Bense and Pellevoisin (1997) reported that observations between 1992 and 1997 confirmed the satisfactory performance of the EME mixes in terms of stiffness, high resistance to plastic deformation and absence of low temperature cracking in the Western European climate.

3.4 A Case Study from France The use of EME mixes enables the layer thicknesses usually employed with classic gravel-sand mixtures, the modulus of which, at approximately 9000 MPa, is markedly lower, to be reduced. In order to best manage the composition of EME mixes, the nature of the aggregates and binders based on their physical and mechanical performance must be specified. A major exploratory study was undertaken by two road construction companies and an oil company and the results obtained concerning three hard binders and four different aggregates were presented by Bauer et al. (1996). The selected aggregates were representative of the various petrographic natures and production methods encountered in France. Three massive rocks (coded as Q, D, C), and one alluvial silica-limestone (coded as SC) were studied; the added filler was of limestone origin. The geotechnical characteristics of the aggregates are summarised in Table 3.2.

Table 3.2: Geotechnical characteristics of the aggregates

Unit D Q C SC

Los Angeles % 11 18 20 22 Micro Deval % 10 8 19 4 Density of the aggregate g/cm3 2.86 2.65 2.67 2.53 Flakiness % 11 9.6 26 16

Source: Bauer et al. (1996). From various binders available at the time of the study, two types of penetration grade 10/20 bitumen, and a grade 15/25 bitumen were selected from the market. Their characterisation, obtained through classic tests and rheological tests, was carried out before and after rolling thin film oven test (RTFOT). This enabled their respective changes with regard to ageing to be assessed, but above all allowed them to be compared in a state identical to that in which they appear in the mix. The results are summarised Table 3.3.


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Table 3.3: Binder test results

Unit 10/20 (1) 10/20 (2) 15/25

Pre RTFOT Post RTFOT Pre RTFOT Post RTFOT Pre RTFOT Post RTFOT Penetration (25 °C) 1/10mm 15 10 13 10 21 13 Softening point (ring and ball) °C 68 73.5 69 75 62 72 Modulus (60 °C, 5 Hz) MPa 0.18 0.37 0.23 0.34 0.05 0.14 Modulus (15 °C, 10 Hz) MPa 88 107 88 93.3 48.7 64

Source: Bauer et al. (1996). The classic tests highlight the difference in the characteristics of 15/25 bitumen; however, after RTFOT, as its ageing is greater than that of 10/20 bitumen types, the results obtained from the three binders are very similar. The rheological analyses had two main objectives as follows:

to assess the effect of the modulus of a binder on a mix, through the use of measurements taken in stress conditions that are identical with regard to frequency and temperature

to compare the characteristics of the binder at a high temperature with the behaviour of the mix with regard to rutting.

It was noted in the study that the ageing indices are always higher for 15/25 bitumen, but this change affects the measured parameters differently. However, even after ageing, the level of the moduli remains very different between the 10/20 class and the 15/25 class at high (60 °C) and medium temperatures (15 °C).

In the study by Bauer et al. a classic 0/14 continuous graded composition was selected and the same grading curve was used throughout the study (Figure 3.1). In order to comply with the specifications of the then current standard NFP 98-140, a richness modulus of 3.65 was selected for all the mixes. Taking into account the different densities of the aggregates, the binder contents ranged between 5.7 and 6.2 mass per cent. These mixes correspond to EME Class 2 as defined in the standards.

Source: Bauer et al. (1996).

Figure 3.1: Selected grading curve

5.4

25.0

40.0

50.0

90.0

100.0

7.7

38.0

60.0

70.0

100.0 100.0

9 10 11 12

1822

24

2932

42

5357

66

79

90

100

0

10

20

30

40

50

60

70

80

90

100

% o

f tot

al p

assi

ng

Sieve size (mm)

AC14-EME lower

AC14-EME upper

Selected grading

0.063 0.150 0.6000.300 1.18 2 4 6.3 14 20 31.52.36 10


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The mixes were assessed using classic composition studies (gyratory and wheel-tracking) on the one hand, and then supplemented with mechanical testing such as modulus and fatigue tests as the requirements of the current mix design procedure. The principle of the gyratory test is to measure the change in the void content in a mix sample subjected to isothermal compaction obtained through the combination of a gyratory shear. The change of the void percentage (%V) according to the number of gyrations (N) is expressed by the linear relationship in Equation 2:

𝑉(%) = 𝑉(1) − 𝐾 × ln𝑁 2

where

𝑉(%) = the void content for a number of gyrations N, (%)

𝑉(1) = the calculated void content for one gyration (%)

𝐾 = the compactibility (using gyratory compaction)

𝑁 = the number of gyrations

Table 3.4 summarises the results of the gyratory compaction; the magnitudes V1 and V100 represent the void percentage at one and one hundred gyrations respectively.

Table 3.4: Results of the gyratory test

Property D Q C SC 10/20

(1) 10/20

(2) 15/25 10/20

(1) 10/20

(2) 15/25 10/20

(1) 10/20

(2) 15/25 10/20

(1) 10/20

(2) 15/25

K value (compactibility)

3.68 3.69 3.57 3.37 3.48 3.46 4.05 4.21 4.10 3.24 3.43 3.14

V1 (volume %) 22.0 21.9 21.9 20.6 21.2 21.4 23.2 24.2 24.2 18.7 20.3 19.3 V100 (volume %) 4.9 4.8 5.3 5.0 5.1 5.3 4.4 4.7 5.2 3.6 4.4 4.7 Source: Bauer et al. (1996). With a constant grading curve and richness modulus, the influence of the binder has no noticeable effect on the void percentages obtained for a given compaction energy. At 100 gyrations, the void percentage is clearly identical, whatever the mix composition. Therefore, for all of the mechanical tests, the same void content was required in that study.

Figure 3.2 summarises the rut depths at 30 000 cycles for the EME mixes. Based on the test results the following can be concluded:

With a given aggregate, the rut depths are almost identical, at the precision of this test, whichever binder is used. This is to be expected, as the characteristics of the three types of bitumen after RTFOT and for conditions similar to the rutting test only differ slightly.

With a given type of bitumen, the rut depths are identical for the mixes composed of crushed rock aggregates. However, the rutting is markedly greater with silica-limestone materials. This result, though surprising with hard binders, can probably be explained by the crushing ratio of the aggregates leading to a low coefficient of internal friction in the mix.

For the crushed rock materials investigated in the case study the level of rutting is extremely low.


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— 13 —

Source: Based on Bauer et al. (1996).

Figure 3.2: Wheel-tracking test results

Complex modulus testing is carried out on a trapezoidal test sample to which a sinusoidal stress is applied at given temperatures and frequencies. Table 3.5 provides a comparison of the moduli at 15 °C and 10 Hz; it should be noted that the minimum threshold of the French specification is 14 000 MPa.

In the fatigue test, a trapezoidal test sample is subjected to stress by a continuous sinusoidal wave packet of a given amplitude until conventional cracking occurs. The test allows a fatigue curve to be determined, characterised by its slope and the deformation corresponding to cracking at 106 cycles. Table 3.5 also provides the fatigue test results obtained from various mixes, using one of the 10/20 bitumen; unfortunately, there are no results reported for mixes using the 15/25 bitumen. Taking into account the uncertainty of the measurement, the fatigue test results are considered to be similar.

Table 3.5: Complex modulus and fatigue test results, the effect of aggregates

Unit D – 10/20 (1) Q – 10/20 (1) C – 10/20 (1) SC – 10/20 (1) Modulus (15 °C, 10 Hz) MPa 17 800 15 600 15 100 15 500 Fatigue (10 °C, 25 Hz) Microstrain 132 123 135 128 Slope N/A –0.174 –0.192 –0.215 –0.162

Source: Bauer et al. (1996). This study highlighted the effect of the binder component and the mineral component on the mechanical behaviour of the EME. Thus, it appears that the nature of the aggregate does not have an effect on the fatigue resistance of mixes. Semi-crushed materials, however, diminish the resistance to rutting; this remained in the referenced study, in any event, above that of the specification. It could also be seen that the moduli of the mixes clearly vary with the petrographic nature and, probably, with the rigidity of the aggregates. With a constant granular skeleton, the various types of bitumen used provide similar rutting levels, and yet it is noted that their characteristics at high temperatures are almost identical after RTFOT.

0.0

2.0

4.0

6.0

8.0

10/2

0 (1

)10

/20

(2)

15/2

5

10/2

0 (1

)

10/2

0 (2

)

15/2

5

10/2

0 (1

)

10/2

0 (2

)

15/2

5

10/2

0 (1

)

10/2

0 (2

)

15/2

5

DQ

CSC

Whe

el-tr

acki

ng (3

0 00

0 cy

cles

), %


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— 14 —

3.5 Design Properties of EME in France The French guidelines and specifications determine two types of EME, which are referred to as AC-EME in line with the European specifications. The two types of EME are AC-EME Class 1 and AC-EME Class 2 (National foreword, NF EN 13108-1-2007). Before the introduction of NF EN 13108-1-2007, EME was specified in NFP 98-140-1992, Enrobés hydrocarbons, Couches d`assises: Enrobés à Module Élevé, October 1992 (Asphalt – Road basecourses: road base high modulus asphalt concrete). Due to the introduction of NF EN 13108-1-2007, the standard NFP 98-140-1992 had to be withdrawn; however, since it aggregates the development and requirements of EME, this report will refer to NFP 98-140 frequently.

3.5.1 Binder Content and Richness Modulus In the former EME standard NFP 98-140, the binder content was based on the concept of richness modulus, also referred to as richness factor, which is a bitumen film type approach and the binder content heavily depends on the combined aggregate grading curve of the mixture. In order to conform to the EN 13108 series which does not acknowledge this concept, the requirements for richness modulus were transformed to binder content requirements. In the new system, a minimum of 3.0% is determined as the empirical requirement for both AC-EME Class 1 and AC-EME Class 2. The requirements for richness modulus are summarised in Table 3.6.

Table 3.6: Requirements for richness modulus for AC-EME

Asphalt mix Minimum richness modulus K (-)

AC-EME Class 1 2.5

AC-EME Class 2 3.4 Source: Delorme, Roche and Wendling (2007). The richness modulus should be calculated according to Equation 3:

𝐾 =

� 100𝐵100 − 𝐵�

𝛼√Σ5 3

where

𝐵 = ratio of the binder mass to the total asphalt mix mass, according to Equation 4 (mass %); in the French terminology 𝐵 is also referred to as internal percentage of binder content. It is usually referred to as tlint

𝛼 = correction coefficient relative to the density of the aggregates, according to Equation 5 (-)

Σ = the specific surface area, according to Equation 6 (m2/kg)

𝐵 = 100𝑏𝑖𝑡𝑢𝑚𝑒𝑛 𝑚𝑎𝑠𝑠

𝑑𝑟𝑦 𝑎𝑔𝑔𝑟𝑒𝑔𝑎𝑡𝑒 𝑚𝑎𝑠𝑠 + 𝑏𝑖𝑡𝑢𝑚𝑒𝑛 𝑚𝑎𝑠𝑠 4


A u s t r o a d s 2 0 1 3

— 15 —

𝛼 =2.65𝜌𝐺

5

where

𝜌𝐺 = the maximum density of aggregate (g/cm3)

100Σ = 0.25𝐺 + 2.3𝑆 + 12𝑠 + 150𝑓 6

where

𝐺 = the proportion of aggregate particles greater than 6.3 mm

𝑆 = the proportion of aggregate particles between 6.3 mm and 0.250 mm

𝑠 = the proportion of aggregate particles between 0.250 mm and 0.063 mm

𝑓 = the proportion of aggregate particles less than 0.063 mm

The French mix design approach utilises various steps in general asphalt mix design. For AC-EME it requires the utilisation of all four steps, where the next following step should always be conducted, once the previous step has been met or finished. Testing levels and associated requirements are listed in Table 3.7.

Table 3.7: Testing levels and requirements for AC-EME

Step Test method Test type Reference standard

Requirement

0 Grading and binder content (only for non-trafficked areas)

General + empirical En 12697-2 EN 12697-1 or EN 12697-39

1 Gyratory compaction General + empirical EN 12697-31 Gyratory compactor, % void at different gyrations Void content General + empirical EN 12697-6 Specifications on the percentage of voids based on the

gyratory compactor test (direct height-based measurement) For cores EN 12697-6, C method (bulk density – sealed specimen)

Water resistance General + empirical EN 12697-12 2 Wheel tracking General + empirical EN 12697-22 Wheel tracking, large device (for asphalt mixes designed for

axle loads greater than 13 tonnes), 30 000 cycles, 60 °C 3 Stiffness modulus General + fundamental EN 12697-26 Two-point bending test, complex modulus, 15 °C, 10 Hz 4 Fatigue General + fundamental EN 12697-24 Two-point bending test, 10 °C, 25 Hz

Source: Delorme, Roche and Wendling (2007) and the cited EN standards.

3.6 Performance-based Mix Design of EME 3.6.1 Level 1 Testing In the European product standards over specification is not allowed, i.e. to set multiple requirements for the same property. Therefore, for rut resistance, it is only the wheel-tracking test which should be conducted, and there is no requirement for void content at 10 gyrations.


A u s t r o a d s 2 0 1 3

— 16 —

Level 1 testing requirements for void content control are listed in Table 3.8. The maximum void content after a specified number of gyrations is required to ensure workability of the material. In this case the air void content should be determined according to EN 12697-31; this test standard includes a determination of the void percentage based on measurement of the specimen height.

For all AC-EME, the water sensitivity is required to be at least ITSR70, tested according to EN 12697-12.

Table 3.8: Level 1 requirements for AC-EME

Asphalt mix Gyratory compactor specifications after n gyrations Number of gyrations (n) Void percentage (%), EN 12697-31

AC10-EME Class 1 80 < 10 Vmax10 AC10-EME Class 2 80 < 6 Vmax6 AC14-EME Class 1 100 < 10 Vmax10 AC14-EME Class 2 100 < 6 Vmax6 AC20-EME Class 1 120 < 10 Vmax10 AC20-EME Class 2 120 < 6 Vmax6

Source: Delorme, Roche and Wendling (2007) and NF EN 13108-1.

3.6.2 Level 2 Testing Level 2 testing requires the wheel-tracking test according to EN 12697-22, using the large device, which is related to asphalt mixes designed for axle loads greater than 13 tonnes. The test should be carried out at 60 °C and terminated at 30 000 cycles. Percentage in rutting should be less than 7.5%, where the result should be calculated as the rut depth divided by the slab thickness. This means the standard requires relative and not absolute rut depth.

3.6.3 Level 3 and Level 4 Testing Level 3 testing requires testing of the stiffness modulus at 15 °C and 10 Hz according to EN 12697-26, method A, which refers to the two-point bending test on trapezoidal specimens.

Level 4 testing requires testing of the fatigue resistance at 10 °C and 25 Hz according to EN 12697-24, method A, which refers to the two-point bending test on trapezoidal specimens (Delorme, Roche & Wendling 2007 and NF EN 13108-1). Testing requirements are summarised in Table 3.9.

Table 3.9: Level 3 and level 4 requirements for AC-EME

Asphalt mix Minimum stiffness modulus at 15 °C and 10 Hz (MPa)

Fatigue resistance at 10 °C, 25 Hz (microstrain)

AC-EME Class 1 14 000 100 AC-EME Class 2 14 000 130

Source: Delorme, Roche and Wendling (2007) and NF EN 13108-1.


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3.7 Requirements for Constituent Materials 3.7.1 Binder Types used in EME Although NF EN 13108-1 does not provide guidance about the binder type in EME mixes, useful information can be found in Delorme, Roche and Wendling (2007). It is suggested that the binder should be 15/25 or 10/20 hard penetration grade binder according to EN 13924-2006, Bitumen and bituminous binders, specifications for hard paving grade bitumens. The requirements of the binder are summarised in Table 3.10.

Table 3.10: The requirements of hard penetration grade binders

Requirement Property Standard Unit Penetration grade 15/25 10/20

Consistency at mid-temperatures

Penetration at 25 °C EN 1426 0.1 mm 15 to 25 10 to 20

Consistency at high temperatures

Softening point EN 1427 °C 55 to 71 58 to 78 Dynamic viscosity at 60 °C EN 12596 Pa.s ≥ 550 ≥ 700

Long-term performance (resistance to hardening)

Mass change EN 12607-1 or -3 % ≤ 0.5

Retained penetration EN 1426 % ≥ 55 Softening point after hardening EN 1427 °C ≥ original

minimum +2

Increase in softening point EN 1427 °C ≤ 8 ≤ 10 Other properties Kinematic viscosity at 135 °C EN 12595 mm2/s ≥ 600 ≥ 700

Source: EN 13924. Figure 3.3 visualises the requirements of 10/20 and 15/25 hard penetration grade binders. For comparison, the requirements of a Pen 40/60 bitumen are also provided, based on the data taken from the Shell handbook (Read & Whiteoak 2003).

Source: Based on Read and Whiteoak (2003) and EN 13924.

Figure 3.3: Visualisation of hard penetration grade binder requirements


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— 18 —

3.7.2 Aggregate Grading of the EME Particle size distributions are considered to be continuous for AC-EME mixes; however, utilisation of discontinuities into the grading curve is allowed. It was found that discontinuities have little impact on the material characteristics.

According to EN 130108-1 Bituminous mixtures, material specifications, part 1: asphalt concrete the requirements for the grading shall be expressed in terms of maximum and minimum values by selection for the percentages passing the sieves of:

1.4 D (where D is the nominal size of the aggregate in the mixture, in millimetres)

D (where D is the nominal size of the aggregate in the mixture, in millimetres)

a characteristic coarse sieve

2 mm

0.063 mm.

Also, a combination of sieve sizes from Set 1 and Set 2 is not permissible. In addition, the requirements for the grading envelope may include the percentages passing one optional sieve between D and 2 mm and one optional fine sieve between 2 mm and 0.063 mm. D and the sieves between D and 2 mm shall be selected from the following sieves, belonging either to the basic sieve set plus Set 1 or the basic sieve set plus Set 2, according to EN 13043:

basic sieve set plus Set 1: 4 mm; 5.6 mm; 8 mm; 11.2 mm; 16 mm; 22.4 mm

basic sieve set plus Set 2: 4 mm; 6.3 mm; 8 mm; 10 mm; 12.5 mm; 14 mm; 16 mm; 20 mm

where the basic set consists of 1 mm; 2 mm; 4 mm; 8 mm; 16 mm; 31.5 mm and 63 mm. The optional fine sieve shall be selected from the following sieves: 1 mm; 0.5 mm; 0.25 mm and 0.125 mm.

In France the basic sieve series plus Set 2 is used for asphalt applications (Delorme, Roche & Wendling 2007), therefore for French bituminous mixtures the 1 mm; 2 mm; 4 mm; 6.3 mm; 8 mm; 10 mm; 12.5 mm; 14 mm; 16 mm; 20 mm; 31.5 mm; 40 mm and 63 mm sieve series should be used.

Table 2 of NF EN 13108-1 provides overall limits of target composition for the basic sieve set plus Set 2 (Table 3.11). Combining the suggested grading control points by Delorme, Roche and Wendling (2007) with the overall limits of NF EN 13108-1, the overall control points for AC20-EME, AC14-EME and AC10-EME are summarised in Table 3.12, Table 3.13 and Table 3.14, respectively. The grading control point and the target grading suggested by Delorme, Roche and Wendling (2007) are visualised in Figure 3.4 to Figure 3.6.

Table 3.11: Overall limits of target composition – basic sieve set plus set 2

D 10 14 20 Sieve (mm) Passing sieve (% by mass)

1.4D 100 100 100 D 90 to 100 90 to 100 90 to 100 2 10 to 60 10 to 50 10 to 50

0.063 2.0 to 12.0 0 to 12.0 0 to 11.0 Source: Table 2 of NF EN 13108-1.


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— 19 —

Table 3.12: Grading control points for AC20-EME

Sieve (mm)

Target (%)

Minimum (%)

Maximum (%)

0.063 6.7 5.4 7.7

2 33.0 25.0 38.0

4 47.0 40.0 60.0

6.3 53.0 45.0 65.0

20 90 100.0

31.5 100 100 100 Source: Based on Delorme, Roche and Wendling (2007) and NF EN 13108-1.


Sieve (mm)

Target (%)

Minimum (%)

Maximum (%)

0.063 6.7 5.4 7.7

2 33.0 25.0 38.0

4 47.0 40.0 60.0

6.3 53.0 50.0 70.0

14 90 100.0

20 100 100 100 Source: Based on Delorme, Roche and Wendling (2007) and NF EN 13108-1.


Sieve (mm)

Target (%)

Minimum (%)

Maximum (%)

0.063 6.7 6.3 7.2

2 33.0 28.0 38.0

4 52.0

6.3 55.0 45.0 65.0

10 90 100.0

14 100 100 100 Source: Based on Delorme, Roche and Wendling (2007) and NF EN 13108-1.


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— 20 —

Source: Based on Delorme, Roche and Wendling (2007) and NF EN 13108-1.

Figure 3.4: Grading control points for AC20-EME



5.4

25.0

40.045.0

90.0

100.0

7.7

38.0

60.065.0

100.0 100.0

6.7

33

4753

0

10

20

30

40

50

60

70

80

90

100%

of t

otal

pas

sing

Sieve size (mm)

AC20-EME lower

AC20-EME upper

target

0.063 0.150 0.6000.300 1.18 2 4 6.3 14 20 31.52.36 10

5.4

25.0

40.0

50.0

90.0

100.0

7.7

38.0

60.0

70.0

100.0100.0

6.7

33.0

47.053.0

0

10

20

30

40

50

60

70

80

90

100

% o

f tot

al p

assi

ng

Sieve size (mm)

AC14-EME lower

AC14-EME upper

target

0.063 0.150 0.6000.300 1.18 2 4 6.3 14 20 31.52.36 10


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— 21 —



3.7.3 Aggregate Requirements Fillers and aggregates of the EME mix should conform to the requirements in Table 3.15 and Table 3.16 according to the French specifications. The relevant AS test methods are also summarised in the table, with the current requirements; however, these requirements may not be directly translated into the requirements of the EN specifications.

Table 3.15: Requirements for fillers

Requirements for fillers

EN test method NF EN asphalt specification and EME requirement

AS test method AS and AGPT Part 4B requirements

Particle size distribution (PSD)

EN 13043:2002, Aggregates for bituminous mixtures and surface treatments for roads, airfields and

other trafficked areas

2 mm passing > 100% 0.125 mm passing 85

to 100% 0.063 mm passing 70

to 100%

AS 1141.11.1-2009 Methods for sampling and

testing aggregates: particle size distribution:

sieving method

Requirements according to AGPT Part 4B

0.600 mm passing > 100% 0.300 mm passing 95 to

100% 0.075 mm passing 75 to

100% Apparent particle density measurement

EN 1097-7:2008, Tests for mechanical and physical properties of aggregates, part 7: determination

of the particle density of filler - pycnometer method

TBC AS 1141.7-1995 Methods for sampling and

testing aggregates: apparent particle density

of filler

TBC

Rigden voids EN 1097-4:1999, Tests for mechanical and physical properties of aggregates: part 4: determination of the voids of dry compacted filler

28 to 38 (V28/38) AS 1141.17-1995 Methods for sampling and testing aggregates: voids

in dry compacted filler

Requirements according to AGPT Part 4B Minimum 38%

6.3

28.0

45.0

90.0

100.0

7.2

38.0

65.0

100.0100.0

6.7

33

55

0

10

20

30

40

50

60

70

80

90

100%

of t

otal

pas

sing

Sieve size (mm)

AC10-EME lower

AC10-EME upper

target

0.063 0.150 0.6000.300 1.18 2 4 6.3 14 20 31.52.36 10


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— 22 —

Requirements for fillers

EN test method NF EN asphalt specification and EME requirement


Harmful fines, methylene blue test (MBF)

EN 933-9:2009, Tests for geometrical properties of aggregates, part 9: assessment of fines – methylene

blue test

≤ 10 (MBF10) AS 1141.66-2012 Methods for sampling and

testing aggregates – Methylene blue adsorption

value of fine aggregate and mineral fillers

No reference in AGPT Part 4B

Delta ring and ball test

EN 13179-1:2000, Tests for filler aggregate used in bituminous

mixtures: part 1: delta ring and ball test

EN 1427:2007, Bitumen and bituminous binders: determination of

the softening point: ring and ball method

8 to 16 (DR&B8/16)

Hydrated lime content of the filler should not

exceed 1%

N/A

Only softening point test, which differs to the EN

standard. AS 2341.18-1992 Methods of testing

bitumen and related road making products: method

18: determination of softening point (ring and

ball method)

No reference in AGPT Part 4B

Table 3.16: Requirements for aggregates

Requirements for aggregates

EN test method NF EN asphalt specification and EME

requirement


Particle size distribution (PSD)

EN 13043:2002, Aggregates for bituminous mixtures and surface treatments for roads, airfields and

other trafficked areas


testing aggregates: particle size distribution:

sieving method

Crushed particles EN 933, Tests for geometrical properties of aggregates, Part 5: Determination of percentage of crushed and broken surfaces in

coarse aggregate particles Note: performed on 10/14 mm

fraction

100% (C100/0) AS 1141.18-1996 Methods for sampling and

testing aggregates – Crushed particles in

coarse aggregate derived from gravel

Not specified

Flakiness index EN 933, Tests for geometrical properties of aggregates, Part 3: Determination of particle shape.

Flakiness index

Maximum 25 (FI25) AS 1141.15-1999 Methods for sampling and

testing aggregates – Flakiness index

Requirements according to AGPT Part 4B

Maximum 25 for heavy duty application

Impact value EN 1097-2, Part 2: Methods for the determination of resistance to

fragmentation Note: performed on 8/12.5 mm

fraction

SZ18 AS 1141.21-1997 Methods for sampling and

testing aggregates – Aggregate crushing value

Q205, Determination of the ten per cent fines

value (wet)

Min. 150 kN according to TMR standard for dense graded asphalt (175 kN for OGA)


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Requirements for aggregates

EN test method NF EN asphalt specification and EME

requirement


Los Angeles coefficient

EN 1097-2, Part 2: Methods for the determination of resistance to

fragmentation

Not specified, usually LA20 for heavy duty asphalt applications


testing aggregates – Degradation factor – Coarse aggregate

AS 1141.23-2009

Methods for sampling and testing aggregates – Los

Angeles value

Indicative value according to AGPT Part 4B (no

requirement) for heavy duty application, LA maximum 25

Flow coefficient, fine aggregate fully crushed

EN 933-6, Part 6: Assessment of surface characteristics – flow

coefficient of aggregates

Only for surface courses Ecs35-38

for basecourses not specified

N/A N/A

3.7.4 Richness Modulus Based on the aggregate grading outlined in Section 3.7.2 and Equation 3, the range of related binder content (based on minimum richness modulus parameters) was calculated for different scenarios. The specific surface area results are shown in Table 3.17; Table 3.18 shows the resulting minimum binder contents for a given aggregate density of 2.65 or 2.75 g/cm3. Based on the values provided in Table 3.18, it can be seen that EME requires relatively high minimum binder content.

Table 3.17: Input values into the calculation of K for AC20-EME, AC14-EME and AC10-EME

Asphalt type AC20-EME AC14-EME AC10-EME Grading control point Target Minimum Maximum Target Minimum Maximum Target Minimum Maximum

G (the proportion of aggregate particles greater than 6.3 mm)

47.0 55.0 35.0 47.0 50.0 30.0 45.0 55.0 35.0

S (the proportion of aggregate particles included between 6.3 mm and 0.250 mm)

43.8 37.7 54.4 43.8 42.7 59.4 45.8 36.6 54.8

s (the proportion of aggregate particles between 0.250 mm and 0.063 mm)

2.5 1.9 2.9 2.5 1.9 2.9 2.5 2.1 3.0

f (the proportion of aggregate particles less than 0.063 mm)

6.7 5.4 7.7 6.7 5.4 7.7 6.7 6.3 7.2

100Σ 1148 933 1324 1148 943 1334 1152 1068 1251 Source: Based on Delorme, Roche and Wendling (2007).


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Table 3.18: Typical binder contents for EME application at different aggregate densities and richness factors

Asphalt type ρG (g/cm3)

Richness factor K (-)

AC20-EME

AC20-EME

AC20-EME

AC14-EME

AC14-EME

AC14-EME

AC10-EME

AC10-EME

AC10-EME

Binder content (ratio of the binder mass to the total asphalt mix mass) Asphalt type/grading control point (target, minimum and maximum)

Target Min. Max. Target Min. Max. Target Min. Max. EME Class 1 2.65 2.5

(minimum) 3.9 3.8 4.0 3.9 3.8 4.0 3.9 3.9 4.0

EME Class 1 2.65 3.4 (maximum)

5.2 5.0 5.4 5.2 5.1 5.4 5.3 5.2 5.3

EME Class 2 2.65 3.4 (minimum)

5.2 5.0 5.4 5.2 5.1 5.4 5.3 5.2 5.3


3.8 3.6 3.9 3.8 3.6 3.9 3.8 3.7 3.8

EME Class 1 2.75 3.4 (maximum)

5.1 4.9 5.2 5.1 4.9 5.2 5.1 5.0 5.2


5.1 4.9 5.2 5.1 4.9 5.2 5.1 5.0 5.2

Source: Based on Delorme, Roche and Wendling (2007).


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4 OTHER INTERNATIONAL APPLICATION OF EME MIXES

4.1 Experience in the United Kingdom EME was introduced in the UK to address shortcomings of conventional binder courses. It was found in the UK, while shifting from hot rolled asphalt (HRA) to thin surfacing wearing courses that thin applications were more permeable than previously built HRA. This new type of application needed a layer immediately beneath the thin wearing course to be as impermeable as possible to prevent moisture-induced problems in the lower layers.

It was found in the UK that another prevailing problem is the construction of longitudinal joints in all pavement layers, where longitudinal cracks and other forms of deterioration can develop. It was also found that the use of materials with higher binder contents and a finer aggregate grading, than had been traditionally used in binder course materials in the UK, would help to improve the quality of the material close to longitudinal joints.

A suitable binder course material to fulfil this role was found to be the high modulus asphalt material conforming to the French EME, which is designed to have a good load-spreading ability, good resistance to deformation and cracking. Due to its high binder content, in France it is considered virtually impermeable, when well compacted. Sanders and Nunn (2005) therefore examined the performance of an EME binder course in conjunction with a full-scale accelerated pavement test. A longitudinal section from the pavement was milled out in the wheel track and high modulus asphalt conforming to the French standard was inlaid. The performance of this pavement was compared with a control pavement constructed using a traditional heavy duty macadam (HDM). The authors of this study aimed to design and test Class 2 EME, targeting a superior fatigue resistance. The results can be summarised as follows:

Density measurement showed that EME Class 2 material can be very well compacted in the trench inlay using conventional equipment.

The thick binder film and impermeability of EME helped to ensure that the pavement is waterproof; consequently, the risk of any problems caused by the ingress of water is lower. It should be noted that this is not a requirement according to the French design guidelines.

The mix tested in this study showed superior resistance to water sensitivity and plastic deformation and had very good fatigue resistance.

A thickness reduction can be achieved by the use of EME compared to a conventional HDM application.

Appendix B of the report by Sanders and Nunn provides a specification for EME mixtures. The specification is intended to be used on pilot contracts on the trunk road network and would be subject to ongoing amendment to reflect French practice. The specification in Appendix B of the report is based on the then current French EME specification NFP 98-140 and therefore it is considered identical. Consequently, the specifications from the UK will not be referenced in this report.

Findings in the study by Nunn and Sanders are related to a specific problem and the results discussed in their report cannot therefore be directly applied in base layer applications; as discussed earlier, their report focused on binder (intermediate) layer applications. The prime function of the binder course is to reduce the stresses and strains in the base to an acceptable level and keep water out of the lower layers.


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4.2 South Africa In South Africa, economic development has led to increased volumes of heavy vehicles on the road network, at the same time, more sustainable use of finite road building materials is becoming increasingly important. South African pavements, much like their Australian counterparts, are operating under relatively high pavement temperatures, which made EME an attractive option due to its high stiffness and rut resistance at elevated temperatures.

A technology transfer (T2) project was undertaken to facilitate the introduction of EME, which is referred to as high modulus asphalt (HiMA) in South Africa. The T2 project started with a study tour to Europe in 2008 and ended in 2011 with the successful implementation of an EME trial section on an access road to Durban harbour carrying extremely large volumes of heavy vehicles. The T2 project was funded by the Southern African Bitumen Association (Sabita) and CSIR and the process followed for the project is described by Denneman (2012). Interim guidelines for the design of EME mixes and pavements in South Africa were released in 2011 (Denneman & Nkgapele 2011).

The methodology followed for the South African EME T2 project can be summarised as follows:

South African mix components, i.e. aggregate and a hard 20/30 Pen grade bitumen were sent to laboratories in France. EME mix designs were performed at these laboratories using the French design method and test equipment.

The French mix design information was then used to produce EME mix in a laboratory in South Africa and the performance properties of the EME were characterised using local equivalent performance-related test methods.

Based on the comparative testing using French and South African test methods, tentative performance specifications were set for the design of EME in South Africa. The design of EME is strictly performance based. Specifications were set for workability, durability, stiffness, permanent deformation resistance and fatigue resistance. The interim performance specifications are shown in Table 4.1.

Since there were no local specifications available for the hard bitumen classes used in EME, the EN 13924 and EN 12591 are applied as is in South Africa.

South African equivalents for each of the French aggregate requirements were selected as well for inclusion in the interim specifications.

Once the interim guidelines were completed, local mix designs were developed for an installation trial, eventually resulting in the construction of a test section on a road in Durban harbour. The performance of this trial section will be monitored as part of an ongoing project.

Table 4.1: Interim performance specifications for EME Class 1 and 2 basecourses in South Africa

Property Test Method Performance requirements Class 1 Class 2

Workability Gyratory compactor, air voids after 45 gyrations ASTM D6926 ≤ 10% ≤ 6%

Moisture sensitivity Modified Lottman ASTM D4867 Dependent on climate and mix permeability

Permanent deformation

Repeated simple shear test at constant height, 55 °C, 5000 repetitions

AASHTO T 320 ≤ 1.1% strain ≤ 1.1% strain

Dynamic modulus Dynamic modulus test at 10 Hz, 15 °C AASHTO TP 62 ≥ 14 GPa ≥ 14 GPa

Fatigue Beam fatigue test at 10 Hz, 10 °C, to 50% stiffness reduction AASHTO T 321 ≥ 106 reps @ 300 με ≥ 106 reps @ 390 με Source: Denneman and Nkgapele (2011).


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One of the major challenges faced during the T2 project was that the designers in France had not been able to produce a mix design that met the fatigue requirements for EME Class 2 using the materials sent from South Africa. Many design iterations were performed at CSIR to develop a mix with improved fatigue performance. It was found that although the fatigue performance could be improved, it was impossible to meet the interim fatigue requirement. It was concluded that a harder, proper 10/20 Pen binder would be required to be able to increase the binder content to meet the fatigue performance, while maintaining the rutting performance. Nonetheless, even if the EME did not meet the fatigue requirements for an EME Class 2, the performance of the mix was deemed a significant improvement compared to conventional asphalt mixes used for base layers in South Africa.


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5 EXPERIMENTAL PROGRAM – EME MIX DESIGN

5.1 Binder Test Results A number of major Australian bitumen suppliers were approached during September and October 2012, to find out whether they would be able to supply hard paving grade binder (10/20 Pen or 15/25 Pen), with properties within or close to the requirements of EN 13924:2006. Two suppliers responded that their product would be able to fulfil the above requirements and binder samples were supplied for laboratory testing and subsequent EME mix design; the test results of the binders are summarised in Table 5.2.

In this study only binder B1973 was used for subsequent mix design, due to the time and constraints; however, for completeness, all test results are reported for binder B2316 as well.

5.1.1 Brookfield Test Brookfield tests were performed according to AGPT/T111 Handling viscosity of polymer modified binders, Brookfield thermosel (Austroads 2006a). In this study a Brookfield DV–II+PRO viscometer was used. In order to determine mixing and compaction temperature ranges, the Brookfield test was conducted at 135–150–165–180 °C. In this test series the spindle was not changed; spindle S31 was used throughout the test series. The test results are summarised in Table 5.1.

Table 5.1: Brookfield viscosity results for EME binders

Code Temperature (°C)

Brookfield viscosity (Pa.s) Series 1 Series 2 Series 3 Average

B1973

135 1.33 1.33 1.33 1.33 150 0.61 0.61 0.61 0.61 165 0.31 0.31 0.31 0.31 180 0.17 0.17 0.17 0.17

B2316

135 2.26 2.27 2.27 2.26 150 0.90 0.90 0.90 0.90 165 0.44 0.44 0.44 0.44 180 0.24 0.24 0.24 0.24

The viscosity-temperature chart is a convenient means of plotting the viscosity data for estimating the viscosity of bituminous binders at any temperature within a limited range. It is also a convenient means to estimate the temperature at which a desired viscosity is attained. Above 60 °C two viscosity-temperature points should be plotted and a straight line should be drawn through the points. Some asphalt has viscosity-temperature relationships too complex to be represented by only two or three points; in this case the viscosity at sufficient temperatures should be determined to produce an adequate curve. It should be noted that such a chart does not reflect the shear rate at which the viscosities were determined. Viscosity-temperature charts in this study are produced according to ASTM D2493/D2493M–09, Standard viscosity-temperature chart for asphalts. Based on the test results in Table 5.1, the temperature-viscosity chart is in Figure 5.1. For comparison, a conforming C320 binder and an A15E binder are also presented on the graph.


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Table 5.2: Specifications for hard paving grade bitumens according to EN 13924-2006

Specifications Surrogate characteristic

Test methods Unit Classes(3) Australian test method B1973 B2316 2 3

Consistency at intermediate service temperature

Penetration at 25 °C EN 1426 0.1 mm 15 to 25 10 to 20 Penetration at 25 °C (pu) AS 2341.12 19.7 20.1

Consistency at elevated service temperature

Softening point EN 1427 °C 55 to 71 58 to 78 Softening point (°C) AGPT/T131 64.5 63.0(2)

70.8 69.3(2)

Dynamic viscosity at 60 °C

EN 12596 Pa.s ≥ 550 ≥ 700 Viscosity at 60 °C (Pa.s) AS 2341.2 2 776 10 200 Viscosity at 60 °C (shear rate) 0.60 0.16

Durability, resistance to hardening at 163 °C (EN 12607-1)

Change of mass EN 12607-1 or -3 % ≤ 0.5 N/A Loss of heating (%) AGPT/T103 0.02 0.02 Retained penetration EN 1426 % ≥ 55 N/A Penetration at 25 °C after RTFO (pu) AGPT/T103

AS 2341.12 13.7 (retained

penetration 70%) 16.2 (retained

penetration 74%) Softening point after hardening

EN 1427 °C ≥ orig. min. +2

N/A Softening point after RTFO (°C) AGPT/T103 AGPT/T131

70.4 68.9(2)

81.0 79.5(2)

Increase in softening point

EN 1427 °C ≤ 8 ≤ 10 Increase in softening point 5.9 °C

Increase in softening point 10.2 °C

Increase in softening point & penetration index before test

EN 1427 Ip(1)

°C ≤ 10 from –1.5

to +0.7

≤ 10 ≤ –1.5

PI on original bitumen –0.1; –0.4 considering

shift factor(2)

PI on original bitumen +1.1; +0.8 considering

shift factor(2) Other properties Kinematic viscosity at

135 °C EN 12595 mm2/s ≥ 600 ≥ 700 Brookfield viscosity at 135 °C (Pa.s) AGPT/T111 1.329

(1 290 mm2/s) 2.264 Pa.s

(2 198 mm2/s) Fraas breaking point EN 12593 °C ≤ 0 ≤ 3 Not tested Not tested Not tested Not tested Flash point EN ISO 2592 °C ≥ 235 ≥ 245 Not tested Not tested Not tested Not tested Solubility EN 12592 % mass

fraction ≥ 99.0 N/A Matter insoluble in toluene (% mass) AS 2341.8 0.03 0.11

Tested for Australian specification (not required in EN standard)

N/A Viscosity at 60 °C after RTFO (Pa.s) AGPT/T103 AS 2341.2

6 992 54 428 N/A Viscosity at 60 °C after RTFO (shear rate) 0.40 0.18 N/A Per cent increase in viscosity at 60 °C after

RTFO test (%) N/A 252 534

1 Ip calculation according to Annex A of EN 13924-2006. 2 Considering shift factor; the ASTM and AS results are generally 1.5 °C higher than for the EN method (Read & Whiteoak 2003). 3 Classes are defined according to EN 13924-2006.


A u s t r o a d s 2 0 1 3

— 30 —

Figure 5.1: Brookfield viscosity results for different binder types

5.1.2 Determination of Binder Viscosity Ranges for Mixing and Compaction The Asphalt Institute mix design manual (Asphalt Institute 1984) introduced viscosity requirements for the determination of mixing and compaction temperatures. According to the manual, the asphalt should be heated to 0.17 ± 0.02 Pa.s for mixing and to 0.28 ± 0.03 Pa.s for compaction.

The required temperature values were calculated for the binders, based on viscosity testing performed as part of the project. The results are shown in Table 5.3; based on the results a mixing temperature of 180 °C and a compaction temperature of 170 °C were selected for the production of laboratory specimens using binder B1973.

Table 5.3: Calculated temperature values based on viscosity requirements

Binder type viscosity-temperature

relationship

Mixing and compaction 'level'

Viscosity (Pa.s)

Temperature (°C)

B1973 y = 558.1e-0.045x

Mixing 0.17 180 Compaction 0.28 169

B2316 y = 1734.3e-0.05x

Mixing 0.17 185 Compaction 0.28 175

The French standard NFP 98 150-1 provides manufacturing temperatures for asphalt production; for hard grade bitumen (20/30, 15/25 and 10/20) this temperature ranges from 160 to 180 °C. It should be noted that there is no specific temperature requirement for manufacturing and mixing asphalt mixes containing hard penetration grade binders in the laboratory (NFP 98 150-2010).

5.1.3 Preliminary DSR Test – Strain Sweep Test DSR tests were performed according to the AASHTO standard, Standard method of test for determining the rheological properties of asphalt binder using a dynamic shear rheometer (DSR), T 315–10 (AASHTO 2012).

y = 68.404e-0.037x

R² = 0.9894

y = 531.9e-0.04x

R² = 0.992

y = 558.1e-0.045x

R² = 0.9945

y = 1734.3e-0.05x

R² = 0.99190.0

0.1

1.0

10.0

130 135 140 145 150 155 160 165 170 175 180 185

Visc

osity

(Pa.

s)

Temperature (°C)

C320 - B1909

A15E - B1910

B1973

B2316


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— 31 —

An important step required for the temperature/frequency sweep test was the determination of the strain amplitude. The strain sweep test was conducted at 35 and 60 °C as follows:

Strain sweep for temperature between 50–70 °C:

frequency of 3 rad/s

larger diameter sample of 25 mm

gap (i.e. sample thickness) 1.0 mm; trimming gap at 1.05 mm to achieve 1.0 mm gap

strain range from 0.00 to 0.20%.

Strain sweep for temperature between 20–50 °C:

frequency of 3 rad/s

small diameter sample of 8 mm

gap (i.e. sample thickness) 2.0 mm; trimming gap at 2.1 mm to achieve 2.0 mm gap

strain range from 0.00 to 0.20%.

The results of the strain sweep tests are summarised in Figure 5.2 to Figure 5.5. It was decided to use 5% strain in the temperature-frequency sweep test for both binders.

Figure 5.2: G* ratio, strain sweep B1973 binder, 35 °C




0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20

|G*|

ratio

Strain (%)

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20

|G*|

ratio

Strain (%)

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20

|G*|

ratio

Strain (%)

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

1.05

1.10

0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20

|G*|

ratio

Strain (%)


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— 32 —

5.1.4 DSR Test – Temperature-Frequency Sweep Test Temperature-frequency sweep was performed between 20 and 70 °C as follows:

Temperature-frequency sweep for temperature between 50–70 °C

— 5% (0.05) strain

— frequency sweep at 50–55–60–65–70 °C

— 15 different frequency values between 0.1–0.1585–0.2512–0.3981–0.631–1.0–1.585–2.512–3.981–6.31–10.0–15.85–25.12–39.81–62.83 rad/s

— larger diameter sample of 25 mm

— gap (i.e. sample thickness) 1.0 mm; trimming gap at 1.05 mm to achieve 1.0 mm gap.

Temperature-frequency sweep for temperature between 20–50 °C

— 5% (0.05) strain

— frequency sweep at 20–25–30–35–40–45–50 °C

— 15 different frequency values between 0.1–0.1585–0.2512–0.3981–0.631–1.0–1.585–2.512–3.981–6.31–10.0–15.85–25.12–39.81–62.83 rad/s

— small diameter sample of 8 mm

— gap (i.e. sample thickness) 2.0 mm; trimming gap at 2.1 mm to achieve 2.0 mm gap.

Two sets of the frequency-temperature sweep were completed to be able to assess variability in the test data. The results are summarised in Figure 5.7 to Figure 5.8 for B1973 and in Figure 5.9 to Figure 5.11 for B2316.

Figure 5.6: Frequency-temperature sweep of B1973 – set 1

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1.0E-04 1.0E-03 1.0E-02 1.0E-01 1.0E+00 1.0E+01 1.0E+02 1.0E+03 1.0E+04 1.0E+05

G* [

Pa]

Reduced frequency [rad/s]

7065605550454035302520MC-EME 1973-set1


A u s t r o a d s 2 0 1 3

— 33 —

Figure 5.7: Frequency-temperature of B1973 – set 2

Figure 5.8: B1973, set 1 and set 2 test results correlation

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1.0E-04 1.0E-03 1.0E-02 1.0E-01 1.0E+00 1.0E+01 1.0E+02 1.0E+03 1.0E+04 1.0E+05

G* [

Pa]


7065605550454035302520MC-EME 1973-set2

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08

B197

3 D

SR d

ata

-set

2 (P

a)

B1973 DSR data - set1 (Pa)

line of equality


A u s t r o a d s 2 0 1 3

— 34 —



1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1.0E-04 1.0E-03 1.0E-02 1.0E-01 1.0E+00 1.0E+01 1.0E+02 1.0E+03 1.0E+04 1.0E+05

G* [

Pa]


7065605550454035302520MC-EME 2316-set1

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1.0E-04 1.0E-03 1.0E-02 1.0E-01 1.0E+00 1.0E+01 1.0E+02 1.0E+03 1.0E+04 1.0E+05

G* [

Pa]


7065605550454035302520MC-EME 2316-set2


A u s t r o a d s 2 0 1 3

— 35 —

Figure 5.11: B2316, set 1 and set 2 test results correlation

The master curve (at 45 °C) of the two EME binders is presented in Figure 5.12, a conforming C320 binder and an A15E are also presented for comparison.

Figure 5.12: Master curve of different binders at 45 °C

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08

B231

6 D

SR d

ata

-set

3 (P

a)

B2316 DSR data - set1 (Pa)

line of equality

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E-02 1.0E-01 1.0E+00 1.0E+01 1.0E+02 1.0E+03

G* [

Pa]


MC-C320-1909-set2

MC-A15E-1910-set2

MC-EME 1973-set2

MC-EME 2316-set2


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5.2 Aggregate Test Results It was envisaged during the project development that a road trial would be set up to evaluate in-place performance of the EME mix. Evaluation of the EME mix requires very heavy traffic loading and at the time of aggregate sourcing it was envisaged that a suitable construction site could be selected in the Sydney region. Therefore all aggregates were sourced for the mix design from Sydney.

5.2.1 Test Methods The properties of the aggregate were characterised using the following tests:

aggregate grading in accordance with AS 1141.11.1-2009

particle density on a dry basis (ρbd ) using AS 1141.5-2000 for fine aggregate and AS 1141.6.1-2000 for coarse aggregate

compacted bulk density, or rodded unit weight (RUW) in accordance with AS 1141.4-2000

uncompacted bulk density, or loose unit weight (LUW), also in accordance with AS 1141.4-2000.

5.2.2 Test Results Table 5.4 shows the grading results for the aggregates. The 14 mm, 10 mm, 7 mm and 5 mm aggregates are basalts, the dust is a blend of natural sand and crusher dust, the sand is natural sand. Baghouse fines were used as filler for the mix designs; some mix designs also included one or two per cent of hydrated lime.

The results in Table 5.4 further show the particle density of the aggregates on a dry basis (ρbd). To be able to optimise the volumetrics of the mix design using the Bailey method (Vavrik et al. 2002), LUW and RUW parameters were determined. The mix design was to be created is an EME with a 14 mm nominal maximum aggregate size (NMAS). For a 14 mm NMAS mix, the Bailey method primary control sieve (PCS) is the 2.36 mm sieve. Any aggregate with more than 50% of particles retained above the PCS is a coarse aggregate according to the Bailey method principles, any aggregate with more than 50% passing the PCS is a fine aggregate. For a dense graded mix, LUW tests are performed on the coarse aggregates and RUW tests are performed on fine aggregates. LUW tests were therefore performed on the 14 mm, 10 mm, 7 mm and 5 mm aggregates. RUW tests were performed on the dust and the sand; on the fillers no tests are required. The LUW and RUW information can be used to assess the volume of coarse and fine aggregate in the mix and optimise the aggregate packing. The volume of voids in coarse aggregate in the LUW condition is 1–LUW / ρbd; voids left by the coarse aggregate are filled by the volume of fine aggregate which is equal to RUW / ρbd.

Table 5.4: Aggregate grading and density information

Sample ID 2134 2133 2131 2130 2135 2127 2136 1342 Product 14 mm 10 mm 7 mm 5 mm Dust Sand Baghouse fines Hydrated lime

26.50 mm 100 100 100 100 100 100 100 100 19.00 mm 100 100 100 100 100 100 100 100 13.20 mm 76 100 100 100 100 100 100 100 9.50 mm 12 83 100 100 100 100 100 100 6.70 mm 2 28 76 100 100 100 100 100 4.75 mm 2 10 27 87 100 100 100 100 2.36 mm 2 2 3 18 89 96 100 100


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Sample ID 2134 2133 2131 2130 2135 2127 2136 1342 Product 14 mm 10 mm 7 mm 5 mm Dust Sand Baghouse fines Hydrated lime 1.18 mm 1 1 1 3 67 88 100 100 600 μm 1 1 1 2 46 68 100 100 300 μm 1 1 1 2 26 24 100 100 150 μm 1 1 1 2 14 6 100 100 75 μm 0.8 0.8 1 1.5 8.4 2.1 94 100

ρbd (g/cm3) 2.630 2.650 2.641 2.610 2.438 2.531 2.498 2.517 LUW (g/cm3) 1.439 1.400 1.368 1.381 N/A N/A N/A N/A RUW (g/cm3) N/A N/A N/A N/A 1.510 1.557 N/A N/A

Loose voids (%) 45.3 47.2 48.2 47.1 N/A N/A N/A N/A Rodded voids (%) N/A N/A N/A N/A 38.1 38.5 N/A N/A

5.3 Mix Design Procedure – Trial Mixes The mix design of EME is an iterative process. Mixes are produced using trial aggregate grading curves and binder contents and submitted to the performance-based tests shown in Table 3.7. Based on the results of the tests, changes are made to optimise the design and improve the performance against one or more parameters in Table 3.7.

As part of the mix design process, the performance of four different trial gradings was assessed. The grading curves are shown in Figure 5.13. To provide an appreciation of the density of the gradation, the results are plotted using the so called ‘Fuller’ gradation with the sieve size raised to the power of 0.45. This allows the plotting of the maximum density line, i.e. the grading that theoretically would result in the highest possible density.

The first grading was designed to match the target grading for 14 mm EME as shown in Table 3.13. The subsequent trial gradings were created using Bailey method principles. The constituents of the different trial aggregate blends are shown in Table 5.5; the table also shows the Bailey method coarse chosen unit weight (CA CUW) condition. The CA CUW for the French EME target grading was back-calculated. It is 95% of the coarse aggregate LUW condition; this indicates that this is a coarse graded mix. Coarse graded mixes typically have a CA CUW of 95% to 105% of the CA LUW. Trial grading 2 was designed to be a fine graded mix with a CA CUW of 70% of the CA LUW condition. Trial grading 3 is a very coarse graded mix with a CA CUW of 105% of the CA LUW. Trial grading 4 is a design grading that was optimised using the Bailey method to have maximum voids in mineral aggregate (VMA). The aim was to create an aggregate skeleton that would allow the inclusion of a high binder content without compromising the air void content and permanent deformation performance. The CA CUW condition of Trial 4 is 100% of the CA LUW. The grading of the combined aggregate blends is shown in Table 5.6. A variation on Trial grading 3, containing 2.0% of hydrated lime was tested as well.


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Note: Sieve sizes indicated in red background are the French standard sieves.

Figure 5.13: Trial grading curves

Table 5.5: Components of aggregate blends

Trial % of product added CA CUW 14 mm 10 mm 7 mm 5 mm Dust Sand Baghouse

fines Hydrated

lime

1 32.6 19.6 0 11.4 32.6 0 3.8 0 95

2 24.4 14.3 0 9.7 49.4 0 2.2 0 70

3a 20.6 26.7 9.9 11.5 27.4 0 3.9 0 105

3b 20.6 26.7 9.9 11.5 27.4 0 1.9 2.0 105

4 19.8 25.6 9.5 11.1 30.4 0 2.6 1.0 100

Table 5.6: Combined grading trial blends

Sieve size Trial 1 Trial 2 Trial 3 Trial 4 26.50 mm 100 100 100 100 19.00 mm 100 100 100 100 13.20 mm 92 94 95 95 9.50 mm 68 76 77 78 6.70 mm 54 66 58 60 4.75 mm 49 62 47 49 2.36 mm 36 49 32 34 1.18 mm 27 36 23 25 600 μm 20 26 17 18

0

10

20

30

40

50

60

70

80

90

100

Perc

ent p

assi

ng (%

)

Sieve size (mm)

Trial 1

Trial 2

Trial 3

Trial 4

Max density

EME14-French control point (lower)

EME14-French control point (upper)

0.075 6.700.150 0.60.3 1.18 2.36 4.75 9.5 13.2 19.02.0 14.06.34.00.063 20.0


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Sieve size Trial 1 Trial 2 Trial 3 Trial 4 300 μm 13 16 12 12 150 μm 9 10 9 9 75 μm 6.9 6.7 6.6 6.6

ρg [g/cm3] 2.551 2.539 2.563 2.564 The trial binder contents are shown in Table 5.7. As in any other asphalt mix design, the binder content is a key to meet fatigue performance and permanent deformation criteria in the mix design process. The initial binder content was set to 5.8% by mass of total mix. This results in a richness modulus K that is slightly higher than the minimum of 3.4 for 14 mm EME2 mixes. The intention of selecting this binder content was to assess the mixes at this initial binder content and then improving the fatigue or rutting performance of the mix where required by either increasing or decreasing the binder content. The aggregate packing of trial 4 was optimised to maximise VMA and as such, it was decided to initially test it at higher binder content (Trial 4a). A second set of tests was performed on Trial 4 for with the intention of maximising the rut resistance and therefore the binder content was reduced to the minimum K value of 3.4 (Trial 4b).

Table 5.7: Trial binder contents

Property Trial 1 Trial 2 Trial 3a Trial 3b Trial 4a Trial 4b

Binder content by mass of total mix (%) 5.8 5.8 5.8 5.8 6.3 5.5

Richness modulus K (-) 3.6 3.6 3.7 3.7 4.0 3.4

5.4 Mix Design Procedure – Performance of the Trial Mixes The performance of the trial mixes was assessed against the performance parameters in Table 3.7. For each of the French performance tests, an Australian equivalent test method was selected; the test methods are shown in Table 5.10. The Servopac gyratory compactor equipment was used to provide a measure of the workability of the mix. To allow for an easier comparison of the results to the French EME specification, the settings of the Servopac equipment were changed to match the specifications of the French gyratory compactors. The compaction pressure was set to 600 kPa, the angle of gyration to 0.82 degrees and the speed of compaction to 30 cycles per minute (EN 12697-31).

5.4.1 Rut Resistance The rut resistance of the mix was assessed using the wheel-tracking test in accordance with Austroads method AGPT/T231 (Austroads 2006b), instead of the large wheel-tracking device as required for EME in France. The test results are provided in Section 5.4.5.

5.4.2 Flexural Modulus For the determination of the flexural modulus of the material, the four-point bending test on beam specimens was selected as an equivalent to the French two-point bending tests on trapezoidal specimens. The flexural modulus test was run in accordance with EN 12697-26. The modulus of the material was assessed at the same conditions as used in the French specifications i.e. at 10 Hz and 15 °C. The test results are discussed in Section 5.4.5.

5.4.3 Fatigue Resistance The French specifications require performing the fatigue testing according to EN 12697-24, by using the two-point bending testing on trapezoidal specimens (method A). Due to the lack of equipment in Australia, fatigue testing was performed using the four-point bending test (Austroads 2006c) instead of the French two-point bending test. Tests were performed at 20 °C, initially at


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400 microstrain, with the intention of running additional tests at three different strain levels to complete the full fatigue factorial on 18 specimens required in the European specification (EN 12697-24). Requirements for fatigue testing significantly differ from the Australian test method as outlined in Table 5.8.

Table 5.8: Comparison of EN 12697-24, method A and AGPT/T233 for performing fatigue characterisation test

Procedure EN 12697-24, method A (two-point bending test on trapezoidal specimens)

AGPT/T233, four-point bending

Conventional criteria of failure

Number of load applications, when the complex stiffness modulus has decreased to half its initial value.

Defined to be when the flexural stiffness has decreased to 50% of its initial value or one million loading cycles have been applied, whichever occurs first.

Sample preparation, storage and curing

Prior to starting of testing, specimens shall be stored on a flat surface at a temperature of not more than 20 °C for between 14 days and 42 days from the time of manufacture. The cutting shall be performed no more than eight days after compaction and gluing shall be performed at least two weeks after cutting. The time of manufacture for these samples is the time when they are cut.

Specimens and the slabs from which they are to be prepared shall be stored in an environment where the temperature will not exceed 30 °C. Wherever practicable, tests should be performed within 30 days of the date of compaction for laboratory-prepared slabs or the date of removing slabs from field pavements. During this storage period the specimens should be placed on a flat stiff surface. Air void content of fatigue beams required is 5 ± 0.5%.

Replicates and strain levels

The test loads (strain levels) shall be selected so that the results are calculated by interpolation and not by extrapolation. Utilise a minimum of three strain levels so that one-third of the element test (one single test) will provide results less than 10E+6 cycles and at least one-third of the element tests provide results greater than 10E+6 cycles. At least 18 element tests shall be used to determine the result.

Utilise one strain level at 400 ± 10 microstrain. Use three replicate specimens. Note: for full characterisation of the asphalt, testing at three strain levels is recommended as a minimum. This will require a minimum of nine beams.

Fatigue line The fatigue line of the mixture should be determined at the different displacement amplitude levels (strain levels). The fatigue line shall be estimated in a bi-logarithmic system as a linear regression of fatigue life versus amplitude levels. Using these results, the strain corresponding to an average of 10E+6 cycles (ε6) and the slope of the fatigue line 1/b shall be determined.

Not required.

Loading and test set-up

Controlled displacement, sinusoidal loading. Fatigue resistance determined at 10 °C, 25 Hz.

Controlled displacement, haversine loading. Fatigue resistance determined at 20 ± 0.5 °C, 10 ± 0.1 Hz.

Precision Repeatability, standard deviation, σr = 1.43 µstrain. Repeatability, limit 95%, r = 4.2 µstrain. Reproducibility, standard deviation, σR = 1.43 µstrain.

Not determined.

Fatigue characterisation was performed according to AGPT/T233, with the following exceptions:

three strain levels were applied, in line with EN 12697-24; strain levels were selected in such a way that the strain level to 1 000 000 load repetitions could be determined through interpolation

at least one-third of the element tests provided results less than 10E+6 cycles and at least one-third of the element tests provided results greater than 10E+6 cycles

at least 18 element tests were performed to determine the results.

The results of the complex fatigue characterisation of the EME mix are discussed in Section 5.4.5.


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5.4.4 Moisture Sensitivity For the moisture sensitivity, the standard AGPT/T232 (Austroads 2007b) modified Lotmann test and the standard European test method (EN 12697-12) were performed. Although the French methodology identifies moisture sensitivity as step two in the design process, in this study this test was performed at the final stage, in order to avoid extensive and unnecessary testing with failing trials.

The European standard includes different procedures to determine the moisture sensitivity (also referred to as water sensitivity), the indirect tensile test (method A) and direct compression test (method B) derived from the Duriez test. These two procedures give equivalent results, however, the repeatability and reproducibility of the direct compression test (Duriez test) is considered better (Delorme, Roche & Wendling 2007). Since equipment and experience are readily available in Australia with the indirect tensile test, this test method was performed according to the EN standard and the Austroads test methods respectively.

According to method A as outlined in EN 12697-12, a set of cylindrical test specimens is divided into two equally sized subsets and conditioned. One subset is maintained dry at room temperature while the other subset is saturated and stored in water at an elevated conditioning temperature. After conditioning, the indirect tensile strength of each of the two subsets is determined in accordance with EN 12697-23 at the specified test temperature. The ratio of the indirect tensile strength of the water conditioned subset compared to that of the dry subset is determined and expressed in per cent form. At least six cylindrical specimens shall be prepared for each sample. The test specimens shall be compacted by using 50 gyratory cycles, according to EN 12697-31. A comparison of the EN and Australian test methods is provided in Table 5.9.

Table 5.9: Comparison of EN 12697-12 and AGPT/T232 for performing moisture sensitivity test

Process EN 12697-12 (including EN 12697-23) AGPT/T232

Sample preparation

Test method EN 12697-31 AS 2891.2.2

Compaction Compacted using Servopac, 600 kPa, 0.82°, 30 gyrations/minute.

50 gyratory cycles, 6 specimens minimum.

Compacted using Gyropac, 240 kPa, 2°, 60 gyrations/minute.

targeting 8 ± 1% air void content, 6 + 2 specimens.

Dimension 100 mm diameter specimens were used in this test series.

100 mm diameter specimens were used in this test series.

Conditioning Dry specimens storage

Flat surface in the laboratory within 20 ± 5 °C. N/A In this study the best practice for storage of all

compacted asphalt samples was used, i.e. samples were stored on a flat surface within the laboratory at ambient room temperature. This

temperature falls within 20 ± 5 °C.

Wet specimens Place in vacuum container with distilled water at 20 ± 5 °C temperature; 3 specimens.

Saturate specimens partially, between 55% and 80%; apply initially a water temperature in

desiccator at 50 ± 5 °C and a vacuum pressure of 600 ± 25 mmHg for 10 minutes. If partial saturation

cannot be achieve vary pressure, water temperature and vacuuming time; three

specimens.

Vacuum Residual pressure 6.7 ± 0.3 kPa within 10 ± 1 minute; maintain the vacuum for 30 ± 5

minutes and leave the specimens submerged in water for another 30 ± 5 minutes.

Reject any specimen which has increased by more than 2% in volume.

Storage Place the wet subset of specimens in a water bath at 40 ± 1 °C for a period of 68 to 72 hours.

Condition the partially saturated specimens for 24 ± 1 hour in a water bath at 60 ± 1 °C.


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Process EN 12697-12 (including EN 12697-23) AGPT/T232

Conditioning for indirect tensile test (ITS)

Dry subset Place the dry subset of specimens into a water bath, protecting the specimen from the water by a soft plastic bag or in a thermostatically controlled air chamber; the test temperature is suggested to

be 25 ± 2 °C.

Condition the three specimens of the dry subset in a temperature controlled environment maintained

at 25 ± 1 °C for 2 hours ± 5 minutes.

Wet subset Bring the wet subset of specimens to the test temperature of 25 ± 2 °C by placing them directly

in the water bath.

Place the wet subset into a water bath held at a temperature of 25 ± 1 °C for 2 hours ± 5 minutes.

Storage Store the specimens for at least two hours in the water bath or air chamber for specimens with

diameter less than 150 mm.

Performing the indirect tensile test (ITS)

Test Determine the indirect tensile strength on the test specimens in accordance with the procedure in EN 12697-23. The indirect tensile strength test shall be performed within one minute after the

specimen has been taken out of the conditioning water.

Calculate the indirect tensile strength ratio (ITSR).

Determine the tensile strength on the test specimens in accordance with the procedure in

AGPT/T232.

Calculate the tensile strength ratio (TSR).

The results of the moisture sensitivity tests are discussed in Section 5.4.5.

5.4.5 Test Results Summary General discussion of the trialling phase

To set design criteria for EME1 and EME2, comparative testing would be required using French and Australian test equipment. This does not form part of the scope for the project for the current year. However, for the current project, indicative criteria were set, shown in the last column of Table 5.10. Since the Servopac settings were configured in accordance with the French test method, the indicative workability requirement is equal to the French specification for EME2. The flexural modulus requirement was also kept the same as the French criterion for EME2. The permanent deformation requirement was set based on the criterion for superior rutting performance in Part 4B of the Austroads Guide to Pavement Technology (Austroads 2007a). The indicative fatigue criteria were set based on the criterion for lightly modified PMB asphalt and superior conventional bitumen asphalt in Part 4B.

Table 5.10: Performance testing

Property Test method Settings Indicative criteria(1)

Workability Servopac compaction 100 gyrations, compaction pressure 600 kPa, angle of gyration 0.82°, 30 gyrations/minute

Air voids < 6%

Modulus Four-point bending (EN 12697-26) 10 Hz, 15 °C > 14 GPa

Permanent deformation Wheel tracker (AGPT T231) 60 °C to 10 000/30 000 load repetitions < 3.5 mm

Fatigue Four-point bending (AGPT/T233) At 20 °C, initially at 400με and other two strain levels

Nf50 1 x 10^5-10^6

Moisture sensitivity AGPT/T232 – EN 12697-12 Standard N/A

1 Indicative criteria are provided in order to assess performance based on existing Australian experiences. The criteria listed here are not considered as tentative specification limits; these limits should be developed in subsequent projects.


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The results of the performance tests for the different trials are summarised in Table 5.11. Note that not all performance tests were run for each of the trial designs. During the mix design iterations, there is little benefit in performing all tests on each new trial design if that trial did not yield enough of an improved performance against the targeted parameter for that trial.

Table 5.11: Performance test results

Trial ID 1 CV(1) 2 CV(1) 3a CV(1) 3b CV(1) 4a CV(1) 4b CV(1)

Workability: air voids (%)

0.7 N/A 1.9 N/A 2.0 N/A 3.9 N/A

Modulus [MPa] (mean)

13 596 4.3% 12 020 3.8% 12 684 3.8% 11 092 4.3% 13 461 3.2%

Fatigue (mean) Nf50

209 720 21.2% 260 420 33.1% 151 680 20.31% 243 950 31.0% 115 870 27.6%

Wheel tracking Rut depth 10k (mm)

3.8 3.2 N/A 3.7 N/A 3.1 N/A 2.7 N/A

Wheel tracking Rut depth 30k (mm)

4.1 N/A 4.7 N/A 4.3 N/A 3.1

1 Coefficient of variation (CV) is the ratio of the standard deviation to the mean. It shows the extent of variability in the test results relative to the mean value. The initial trial mixes – Trial 1, 2 and 3a – were designed at the same time. Wheel-tracker slabs were compacted for these mixes and it was found that only Trial 2 met the indicative criterion of < 3.5 mm. The wheel-tracker results are shown in Figure 5.15; tests were run up to 30 000 cycles as required for the large wheel-tracker according to the European specifications, but using the small wheel-tracker equipment. Rut depths at 10 000 and 30 000 cycles are reported in Table 5.11. Only one specimen was tested per trial, as the intention during the design process is to make significant improvements in each iteration. Only the final mix design is subjected to the full set of tests.

Slabs for modulus and fatigue testing were compacted for Trial 1 and 2. The average flexural modulus results for the different trials are shown in Figure 5.14; four beams were tested for each design. Frequency sweep tests were performed to characterise the modulus at different loading times. Note that the frequency at which the mixes are assessed against the 14 GPa criterion is 10 Hz. After it became clear that the trial mixes 1 and 3 did not meet the modulus criterion, it was decided not to compact a slab for fatigue beams for Trial 2. Instead, a mix was designed containing 2% hydrated lime in an attempt to increase the modulus – this is Trial 3b. Unfortunately, this did not have the desired effect on the modulus.

Another concern from the first design iterations was the low void content in the workability tests. Although there is only a maximum requirement for air voids, it was feared that very low void contents may be related to reduce permanent deformation resistance. An attempt was made to optimise the aggregate packing for VMA using the Bailey method. The results were Trial 4b, which has an increased VMA compared to the earlier iterations as shown in Table 5.12. Trial 4a does not have a higher void content in the workability test; this is because the binder content was also increased to optimise fatigue performance.


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Table 5.12: Volumetric properties

Property T1 T2 T4a T4b Max. density (t/m3) 2.437 2.429 2.426 2.449 Bulk density (t/m3) 2.419 2.383 2.377 2.353 Air voids (%) 0.7 1.9 2.0 3.9 VMA (%) 10.7 11.6 13.1 14.3

The results of the initial fatigue tests at 400 microstrain are shown in Figure 5.16. The results show considerable scatter, which is characteristic for fatigue test results. It is impossible to statistically rank the mix designs, even though four beams were tested per mix instead of the set of three specimens commonly tested in Australia.

With the intention to optimise rutting performance, specimens with the Trial 4 grading were also prepared at the minimum binder content that still yielded a satisfactory richness modulus K – this is Trial 4b.

Figure 5.14: Flexural modulus frequency sweep results

4 000

6 000

8 000

10 000

12 000

14 000

16 000

0.0 0.1 1.0 10.0 100.0

E* (M

Pa)

Frequency (Hz)

Trial 1

Trial 3a

Trial 3b

Trial 4a

Trial 4b

Target


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Figure 5.15: Wheel-tracker results

Figure 5.16: Preliminary fatigue results, mix design, trial phase

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

0 5000 10000 15000 20000 25000 30000

Perm

anen

t def

orm

atio

n (m

m)

Load cycles

Trial 1

Trial 2

Trial 3

Trial 4a

Trial 4b

50 000

100 000

150 000

200 000

250 000

300 000

350 000

400 000

Nf 5

0

Trial

dataMean

1 3a 3b 4a 4b


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Fatigue characterisation

As discussed in Section 5.4.3, in order to determine the fatigue line and characterise the fatigue property of the EME mix in this way requires extensive laboratory testing. The results of the complete fatigue test, outlined in Table 5.13, required all together 247 hours to complete; given at 10 Hz frequency, 36 000 cycles can be applied in an hour. Although a full characterisation requires extensive and time consuming testing, it is considered the only feasible way to gain reliable results.

Table 5.13: Test results of fatigue testing (18 beams)

Strain level (microstrain)

Loading cycles Specimen 1 Specimen 2 Specimen 3 Specimen 4 Specimen 5 Specimen 6 Specimen 7

400 194 680 164 230 310 200 306 690 312 500 115 980 236 800 550 21 910 42 740 40 780 61 990 38 490 47 540 N/A 310 1 208 680 761 280 1 461 460 1 374 770 1 119 670 1 060 510 N/A

According to EN 12697-24, Appendix A, the general from of the fatigue line is provided in Equation 7. Based on the results in Table 5.13, the fatigue line is shown in Figure 5.17, which can be expressed as outlined in Equation 8:

lg(𝑁) = 𝑎 + �1𝑏� ∗ lg (𝜀) 7

lg(𝑁) = 21.36 + �1

−0.163� ∗ lg (𝜀) 8

where

𝑁 = number of load cycles

𝑎 = constant

𝑏 = slope of fatigue line

𝜀 = strain (microstrain)

The calculated strain is ε6 = 319 µstrain (at one million cycles), and the slope of the fatigue line is b = –0.163.


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Figure 5.17: Fatigue line of the EME mix

The level 4 requirement for EME Class 2 according to the French specification is 130 µstrain at 10 °C, 25 Hz, in accordance to EN 12697-24, method A (Delorme, Roche & Wendling 2007 and NF EN 13108-1). The test results of this study (Figure 5.17) cannot be directly related to the French specification limits as the test set-up and circumstances are different to the Australian test method as outlined in Table 5.8. Establishing specification limits for confirming EME mixes under Australian test conditions will require extensive inter-laboratory testing and this work will be carried out in subsequent years and follow-up research projects.

Moisture sensitivity

According to the test parameters outlined in Section 5.4.4, the moisture sensitivity test results are summarised in Table 5.14 and Table 5.15. The saturation requirements and conditioning framework are different in AGPT/T232 and EN 12697-12. Although the samples had a higher swell than 2% following the vacuum procedure, the test was performed on these samples. It is thought that the high swell value was a combined result of the low air void content, high negative pressure and long vacuum conditioning. More experience is needed with how to apply and build up the pressure since the EN standard sets out the requirements (timeframe and target) but does not provide practical guidelines for the procedure. Also, in the test series according to AGPT/T232 it is required that a vacuum is maintained for 10 minutes in the saturation procedure; this requirement was not fulfilled as the samples became saturated in a much shorter timeframe. Appendix A shows examples of the surface texture and broken surface of the specimens used in the moisture sensitivity tests.

The minimum requirement of indirect tensile strain ratio (ITSR) is 70% according to the French specifications; the EME mix (Trial 4a) fulfilled this requirement with a TSR value of 94.0%, according to AGPT/T232 and an ITSR value of 94.6% according to EN 12697-12.

y = 3036.4x-0.163

R² = 0.948

100

1000

1.E+04 1.E+05 1.E+06 1.E+07

Stra

in le

vel (

mic

rost

rain

)

Loading cycles

ε6=319 µstrain


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Table 5.14: Stripping potential according to AGPT/T232

Subset Property Series 1 Series 2 Series 3 Average Wet Number of gyratory cycles 10 10 10 N/A

Air voids (%) 7.0 7.0 7.5 7.2 Degree of saturation (Sp) (%) 57.1 58.0 62.7 59.3 Swell (Vs nearest 0.1%) 0.6 0.3 0.1 0.3 Force (P nearest 0.1 kN) 12.5 12.3 12.6 12.5 Tensile strength (kPa) 1138.7 1127.0 1150.6 1138.8 Type of failure (EN 12697-23) C C C N/A

Dry Number of gyratory cycles 10 10 10 N/A Air voids (%) 7.0 7.0 7.6 7.2 Force (P nearest 0.1 kN) 13.5 13.7 12.1 13.1 Tensile strength (kPa) 1263.2 1274.3 1096.7 1211.4 Type of failure (EN 12697-23) A A A N/A

Tensile strength ratio (TSR) 94.0

Table 5.15: Water sensitivity according to EN 12697-12 and EN 12697-23

Subset Subset type Series 1 Series 2 Series 3 Average

Wet Number of gyratory cycles 50 50 50 N/A Air voids (%) 4.1 4.5 3.9 4.2 AGPT/T232 degree of saturation (Sp) (%) 65.6 63.2 70.9 66.6 EN 12697-6 (volume change after vacuum (%)) 2.2 2.3 2.5 2.3 EN 12697-6 (volume change after conditioning (%)) 2.9 2.8 2.9 2.9 AGPT/T232 degree of saturation (Sp) (%) 81.7 76.6 81.9 80.1 Force (P nearest 0.01 kN) 17.5 17.7 16.8 17.3 Tensile strength (GPa) 0.00158 0.00163 0.00157 0.00159 Type of failure (EN 12697-23) C C C N/A

Dry Number of Marshall blows or gyratory cycles 50 50 50 N/A Air voids (%) 3.5 3.3 3.5 3.4 Force (P nearest 0.01 kN) 18.0 17.5 18.6 18.0 Tensile strength (GPa) 0.00166 0.00166 0.00173 0.00168 Type of failure (EN 12697-23) A A A N/A

Indirect tensile strength ratio (ITSR) 94.6


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6 SUMMARY AND CONCLUSIONS The primary focus of this study was to investigate the potential introduction of the French high modulus asphalt technology, called enrobés à module élevé (EME) to Australia. The EME mix technology provides a high performing asphalt material for use in heavy duty pavements, specifically suitable in the following situations:

the pavement carries large volumes of heavy vehicles and requires strengthening

there are geometric constraints, such as height restrictions, to apply the required thickness of the overlay


Due to the elevated pavement temperatures in Australia, the EME application may provide a cost-effective solution for heavy duty pavements.

6.1 Summary As part of this study, a review of the types of heavy duty asphalt available in Australian specifications was undertaken. The survey revealed that heavy duty applications tend to move into performance-related and performance-based testing; however, these requirements are mainly related to moisture sensitivity and wheel-tracking. Some jurisdictions specify stiffness (indirect tensile resilient modulus) with specification limits; however, some jurisdictions requires this to be recorded, and do not require specification limits yet. It was found that to determine the fatigue characteristics is not required, except in Victoria, for any Australian heavy duty asphalt applications. It is not required to record fatigue property either.

A comprehensive literature survey was conducted to provide information on the development of EME; this is considered important as the design approach of the EME mix differs from mix design approaches typically used in Australia in that it strictly applies performance-based and performance-related testing. Guidance on selecting appropriate aggregate grading and binder content for the trial mixes is discussed in detail. Also, case studies were referenced to provide insight into the mix design process and the achieved performance assessment.

According to the French requirements, 15/25 and 10/20 hard penetration grade binders can be used for EME mixes. At the time of the laboratory program development (September 2012) only one bitumen supplier could deliver bitumen samples in Australia for designing EME mix. The binder fulfilled the requirements of a 15/25 penetration grade binder according to the European specifications. It was found that Australian specifications can be used to characterise the binder and assess whether it meets the European specification requirements. Only little differences could be identified when testing the softening point, since the ASTM and AS test results are generally 1.5 °C higher than for the EN method.

It was found that requirements cannot be directly translated for fillers and aggregates; some test methods, such as delta ring and ball test for fillers, or flow coefficient of the fine aggregate, are not available in Australia. Some other test methods are similar, such as determining the Rigden voids; however, there are some differences in the test method itself. It would require more detailed work to select relevant Australian standards and develop specification limits for aggregates for future EME applications.

The mix design procedure is summarised in Section 5. The iterative nature of the laboratory testing reported in the study also provides a good understanding for practitioners with respect to the complexity and requirements of an EME mix design. Aggregate grading was selected to meet


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the initial grading control points provided by the French guidelines and meet the minimum richness factor, which relates to the required binder content; the lowest selected binder content in the trials was 5.8%. The laboratory program carried out in the work includes the comprehensive characterisation of the EME mix on the performance-related parameters as summarised below.

Workability with hard grade binders

By utilising hard penetration grade binder the workability of the mix and the predicted air void content in the finished mix is very important. It is required that the mix has a certain air void content at a pre-defined gyratory cycle; for AC14-EME Class 2 material, the required maximum air void content at 100 gyrations is 6%, which was met for all trial mixes.

Gyratory compaction parameters in France significantly differ to the Australian standard requirements in terms of pressure, angle and speed of gyration. Also, gyratory cycles are selected according to the mix type and it is not related to traffic loading as it is in the US or, to some extent, in Australia.

Moisture sensitivity (durability)

The saturation requirements and conditioning framework for moisture/water sensitivity are different in AGPT/T232 and EN 12697-12. The minimum requirement of ITSR is 70% according to the French specifications; the EME mix fulfilled this requirement with a TSR value of 94.0%, according to AGPT/T232 and an ITSR value of 94.6% according to EN 12697-12.

Rutting resistance

The rutting performance of the trial mixes fulfilled the requirements of the Australian heavy duty asphalt applications; however, Australian specifications provide guidelines for maximum rut depth. The French specification set a maximum relative rut depth, where the slab thickness is also considered. Also, in France the test is performed by using the large wheel-tracker and it is not possible to directly relate the test results obtained from the small wheel-tracker, which was used in this study.

In order to set Australian specifications for wheel-tracking, more work and international comparison is required.

Stiffness properties

The minimum stiffness requirement of 14 000 MPa could not be met in the mix design process. It should be noted that the test was performed using the four-point bending test according to EN 12697-26. In the French mix design procedure it is required to use the two-point bending test (EN 12697-26); however, such equipment is not available in Australia. Correlation between the results obtained from these two equipment types is not clearly defined; however, based on the authors’ experience it is expected that the stiffness value, if tested with the two-point bending equipment, is higher compared to the four-point bending equipment. The offset depends on the asphalt and binder type, the temperature and frequency.

It is envisaged that the design stiffness could be increased with the application of fully crushed (manufactured) sand and harder bitumen, conforming to the requirements of the 10/20 penetration grade bitumen.

Fatigue resistance

The fatigue property of the mix is usually determined once the performance criteria of workability, rutting resistance and stiffness are fulfilled. However, due to the limited time and material availability, further optimisation of the trial mixes was not possible. In order to provide a full mix


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design procedure the fatigue performance (according to EN 12697-24) of a selected trial mix was tested.

To be able to rank fatigue performance of the trail mixes, the fatigue test was performed at 400 microstrain using four beams. This provided indicative figures; however, it should be noted that such a ranking may be misleading, as the EN standard requires testing of six beams at three different strain levels.

Although the Trial 4a mix had the lowest stiffness value, this mix was selected to perform fatigue testing according to EN 12697-24. This decision was made on the basis that none of the trials met the minimum 14 000 MPa requirement, but this mix had the second best initial fatigue properties, the best rutting performance and acceptable air void content.

Based on the fatigue test results of 19 beams, the fatigue line was constructed and the calculated strain returned ε6 = 319 µstrain (at one million cycles); the slope of the fatigue line was 1/b = –0.16. Although a full characterisation requires extensive and time consuming testing, it is considered the only feasible way to obtain results of suitable reliability. The level 4 requirement to EME Class 2 according to the French specification is 130 µstrain at 10 °C, 25 Hz, in accordance to EN 12697-24, method A. However, the test results of this study cannot be directly related to the French specification limits as the test set-up and circumstances are different to the Australian test method. Establishing specification limits for confirming EME mixes under Australian test conditions will require inter-laboratory testing and this work will be carried out in subsequent years and follow-up research projects.

6.2 Conclusions The explorative study provides an insight into the complexity of the design of EME mixes. The trial mixes tested in this study did not fully conform to the French specifications; it is believed that the application of fully crushed sand and potentially harder bitumen would increase the design properties.

Also, this demonstration study highlighted that for a successful technology transfer it is important to select corresponding Australian standardised test methods to measure the performance of the design mix. This would also be the basis of setting correct performance limits in specifications; the complexity of this issue was discussed in the study. Test methods for the binder are readily available; however, test methods for fillers, aggregates and for the EME mix would require more work in subsequent projects.

It is unlikely that the mix designs developed as part of the study would meet the French specifications at this stage. More work would be required to develop mixes with all characteristics of an EME Class 2. However, the study did provide an indication of the properties of EME mixes compared to conventional Australian mix types.

Stiffness and fatigue properties are input values into the mechanistic pavement design. It is important to highlight that fatigue properties obtained from the mix design cannot be directly translated into transfer functions, which are used in the pavement design procedure. Transfer functions used in Australia today are not considered suitable to use for EME mixes; the currently used transfer functions were developed for mixes which are completely different to EME mixes and the utilisation of these functions would introduce a disconnection between mix performance in the laboratory and field. The correlation between fatigue properties obtained from the laboratory mix design procedure and transfer functions require long-term performance observations and performance monitoring. Therefore it is important to continue the work in this area in subsequent projects.


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REFERENCES AASHTO 2012, Standard method of test for determining the rheological properties of asphalt binder using a

dynamic shear rheometer (DSR), T 315–10, AASHTO, Washington, DC, USA.

Asphalt Institute 1984, Mix design methods for asphalt concrete and other hot mix types, manual series MS-2, The Asphalt Institute, Maryland, USA.

Austroads 2006a, Handling viscosity of polymer modified binders, Brookfield thermosel, test method, AGPT/T111, Austroads, Sydney, NSW.

Austroads 2006b, Deformation resistance of asphalt mixtures by the wheel tracking test, test method, AGPT/T231, Austroads, Sydney, NSW.

Austroads 2006c, Fatigue life of compacted bituminous mixes subject to repeated flexural bending, test method, AGPT/T233, Austroads, Sydney, NSW.

Austroads 2007a, Guide to pavement technology: part 4b: asphalt, AGPT04B/07, Austroads, Sydney, NSW.

Austroads 2007b, Stripping potential of asphalt: tensile strength ratio, test method, AGPT/T232, Austroads, Sydney, NSW.

Austroads 2012, Guide to pavement technology: part 2: pavement structural design, 3rd edn, AGPT02/12, Austroads, Sydney, NSW.

Bauer, P, Glita, S, Chaverot, P, Michou, J, Perdereau, P & Vincent, Y 1996, ‘Influence of the nature of aggregates and the rheology of hard bitumen on the mechanical properties of hot mixes used in foundations and road bases’, [in French], Proceedings of the Eurasphalt and Eurobitume Congress, Strasbourg, Foundation Eurasphalt, Paris, France.

Delorme, J, Roche, C & Wendling, L 2007, LPC bituminous mixtures design guide, Laboratoire Central des Ponts et Chaussees, Paris, France.

Denneman, E 2012, ‘High modulus asphalt technology transfer successfully completed’, Sabita Digest 2011, pp. 142-150.

Denneman, E & Nkgapele, M 2011, Interim guide for the design of high modulus asphalt mixes and pavements in South Africa, SABITA, Pinelands, South Africa.

Department of Transport and Main Roads 2011, Heavy duty asphalt, technical standard MRTS31, TMR, Brisbane, Queensland.

Laboratoire Central des Ponts et Chausees 1997, French design manual for pavement structures, LCPC, Paris, France.

Read, J & Whiteoak, D 2003, The shell bitumen handbook, 5th edn, Shell Bitumen, UK.

Roads and Maritime Services 2012, Heavy duty dense graded asphalt, specification R116, RMS, Sydney, NSW.

Sanders, P & Nunn, M 2005, The application of Enrobe a Module Eleve in flexible pavements, TRL report 636, Transport Research Laboratory, Crowthorne, UK.

Serfass, J, Bauduin, A & Garnier, J 1992, ‘High modulus asphalt mixes: laboratory evaluation, practical aspects and structural design’, International conference on asphalt pavements, 7th, 1992, Nottingham, United Kingdom, ISAP, Austin, Texas, USA, pp. 275-88.


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Serfass, J, Bense, P & Pellevoisin, P 1997, ‘Properties and new developments of high modulus asphalt concrete’, International conference on asphalt pavements, 8th, 1997, Seattle, Washington, University of Washington, Seattle, WA, USA, pp. 325-33.

Vavrik, W, Huber, G, Pine, W, Carpenter, S & Bailey, R 2002, Bailey method for gradation selection in hot-mix asphalt mixture design, transportation research circular E-C044, TRB, Washington, DC, USA.

VicRoads 2012, Registration of bituminous mix designs, code of practice RC 500.01, VicRoads, Kew, Vic.

Standards Australia

AS 1141.4-2000, Methods for sampling and testing aggregates: bulk density of aggregate.

AS 1141.5-2000, Methods for sampling and testing aggregates: particle density and water absorption of fine aggregate.

AS 1141.6.1-2000, Methods for sampling and testing aggregates: particle density and water absorption of coarse aggregate: weighing-in-water method.

AS 1141.11.1-2009, Methods for sampling and testing aggregates: particle size distribution: sieving method.

AS 2341.12-1993, Methods for testing bitumen and related road making products: method 12: determination of penetration.

AS 2341.18-1992, Methods of testing bitumen and related road making products: method 18: determination of softening point (ring and ball method).

AS 2341.2-1993, Methods of testing bitumen and related roadmaking products: determination of dynamic (coefficient of shear) viscosity by flow through a capillary tube.

AS 2341.4-1994, Methods of testing bitumen and related roadmaking products: determination of dynamic viscosity by rotational viscometer.

AS 2891.2.2-1995, Methods of sampling and testing asphalt: sample preparation: compaction of asphalt test specimens using a gyratory compactor.

ASTM International

ASTM D2493/D2493M–09, Standard viscosity-temperature chart for asphalts.


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European Committee for Standardization (CEN)

EN 12591: 2000, Bitumen and bituminous binders: specifications for paving grade bitumens.

EN 12697-1:2012, Bituminous mixtures: test methods for hot mix asphalt: part 1: soluble binder content.

EN 12697-2:2002, Bituminous mixtures: test method for hot mix asphalt: part 2: determination of particle size distribution.

EN 12697-6:2012, Bituminous mixtures: test methods for hot mix asphalt: part 6: determination of bulk density of bituminous specimens.

EN 12697-12:2008, Bituminous mixtures: test methods for hot mix asphalt: part 12: determination of the water sensitivity of bituminous specimens.

EN 12697-22:2003, Bituminous mixtures: test methods for hot mix asphalt: part 22: wheel tracking.

EN 12697-23:2003, Bituminous mixtures: test methods for hot mix asphalt: part 23: determination of the indirect tensile strength of bituminous specimens.

EN 12697-24:2012, Bituminous mixtures: test methods for hot mix asphalt: part 24: resistance to fatigue.

EN 12697-26:2012, Bituminous mixtures: test methods for hot mix asphalt: part 26: stiffness.

EN 12697-312007, Bituminous mixtures: test methods for hot mix asphalt: specimen preparation by gyratory compactor.

EN 12697-39:2012, Bituminous mixtures: test methods for hot mix asphalt: part 39: binder content by ignition.

EN 13043:2002, Aggregates for bituminous mixtures and surface treatments for roads, airfields and other trafficked areas.

EN 13108-1:2006, Bituminous mixtures: material specifications: part 1: asphalt concrete.

EN 13924:2006, Bitumen and bituminous binders: specifications for hard paving grade bitumens.

Association Francaise de Normalisation (AFNOR)

NF EN 13108-1:2007, Bituminous mixtures: material specifications: part 1: asphalt concrete.

NFP 98 150:2010, Bituminous asphalts: laying of pavement bases, binder and wearing courses: part 1: hot-mix asphalts: constituents, formulation, fabrication, transport, laying and site inspection [French language].


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APPENDIX A APPEARANCE OF THE SURFACES – MOISTURE SENSITIVITY TEST SAMPLES

Figure A 1 to Figure A 8 show examples of the surface texture and appearance of the broken surfaces of the moisture sensitivity samples.

A.1 Tested According to AGPT/T232

Figure A 1: Wet subset, surface texture

Figure A 2: Wet subset, broken surface

Figure A 3: Dry subset, surface texture

Figure A 4: Dry subset, broken surface


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A.2 Tested According to EN 12697-12 (EN 12697-23)

Figure A 5: Wet subset, surface texture

Figure A 6: Wet subset, broken surface

Figure A 7: Dry subset, surface texture

Figure A 8: Dry subset, broken surface

INFORMATION RETRIEVAL

Austroads, 2013, EME Technology Transfer to Australia: An Explorative Study, Sydney, A4, pp.60. AP-T249-13.

Keywords:

EME, high modulus asphalt, technology transfer, asphalt mix design, performance based testing, performance related testing

Abstract:

This study investigated the potential introduction of the French high modulus hot mix asphalt technology, called enrobés à module élevé (EME) to Australia. The EME mix technology provides a high performing asphalt material for use in heavy duty pavements, where the pavement carries large volumes of heavy vehicles, there are potential height constraints, or the traffic loading is considered extreme, such as slow lanes, climbing lanes, bus lanes and airport pavements.

Based on an international literature review, the historical development and performance of EME was investigated. In co-operation with the asphalt industry, the availability of the required materials such as suitable aggregates and hard penetration grade bitumen was also investigated. By using locally available constituent materials, a laboratory-based demonstration project was undertaken to provide insight and guidance for EME mix design. The mix design of EME differs from mix design approaches typically used in Australia in that it is strictly based on performance-related testing. The trial and error approach of the laboratory testing reported in the study also provides a good understanding for practitioners about the complex nature and requirements of an EME mix design.

AP-T249-13 Enrobes a Module Eleves

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