review of overseas trials of warm mix asphalt pavements and current usage by austroads members

AP-T215-12

Review of Overseas Trials of Warm Mix Asphalt Pavements and Current Usage by

Austroads Members

AUSTROADS TECHNICAL REPORT

Review of Overseas Trials of Warm Mix Asphalt Pavements and Current Usage by Austroads Members


Published November 2012

© Austroads Ltd 2012

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 978-1-921991-57-8

Austroads Project No. TT1454

Austroads Publication No. AP–T215-12

Project Manager Andrew Papacostas - VicRoads

Prepared by Binh Vuong, Kieran Sharp, John Rebbechi and Susannah Boer

ARRB Group

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.

mailto:[email protected]


Sydney 2012

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 Transport, 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

Department of Territory and Municipal Services Australian Capital Territory

Commonwealth Department of Infrastructure and Transport

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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CONTENTS 1 INTRODUCTION ................................................................................................................... 1

1.1 Austroads Project TT1454 ..................................................................................................... 2

2 WARM MIX ASPHALT .......................................................................................................... 3

2.1 General .................................................................................................................................. 3 2.2 Commercially-available WMA Technologies .......................................................................... 3 2.3 Categories of WMA Technologies .......................................................................................... 4

2.3.1 Sequential Aggregate Coating and Binder Foaming Technology .............................. 5 2.3.2 Binder Foaming Technology Using Water Based Mechanical Systems .................... 6 2.3.3 Binder Foaming Technology Using Water Bearing Additives .................................... 7 2.3.4 Chemical Additives ................................................................................................... 7 2.3.5 Organic Additives ..................................................................................................... 8 2.3.6 Combined Chemical and Organic Additives ............................................................. 9

3 FIELD TRIALS OF WMA TECHNOLOGIES ........................................................................ 10

3.1 Introduction .......................................................................................................................... 10 3.2 Stages of Field Trials ........................................................................................................... 10

3.2.1 Development Trials ................................................................................................ 10 3.2.2 Production/Demonstration Trials ............................................................................ 12 3.2.3 Validation/Implementation Trials ............................................................................ 13

3.3 Draft WMA Protocols ........................................................................................................... 14 3.3.1 Australia ................................................................................................................. 14 3.3.2 South Africa ........................................................................................................... 14

4 FIELD TRIALS OF FOAMING TECHNOLOGIES USING SEQUENTIAL AGGREGATE COATING AND BINDER FOAMING ................................................................................... 16

4.1 WAM-foam® ........................................................................................................................ 16 4.1.1 Background ............................................................................................................ 16 4.1.2 Development Trials ................................................................................................ 16 4.1.3 Demonstration Trials .............................................................................................. 17 4.1.4 Implementation/Validation Trials ............................................................................ 18

4.2 Low Energy Asphalt (LEA1) ................................................................................................. 18 4.2.1 Background ............................................................................................................ 18 4.2.2 Development Trials ................................................................................................ 18 4.2.3 Demonstration Trials .............................................................................................. 19 4.2.4 Implementation/Validation Trials ............................................................................ 19

4.3 Low Emission Asphalt (LEA2) .............................................................................................. 19 4.3.1 Background ............................................................................................................ 19 4.3.2 Development Trials ................................................................................................ 19 4.3.3 Demonstration Trials .............................................................................................. 19 4.3.4 Implementation/Validation Trials ............................................................................ 20

5 FIELD TRIALS OF FOAMING TECHNOLOGIES USING WATER-BASED MECHANICAL SYSTEMS ................................................................................................... 21

5.1 Double Barrel® Green ......................................................................................................... 21 5.1.1 Background ............................................................................................................ 21 5.1.2 Development Trials ................................................................................................ 21 5.1.3 Demonstration Trials .............................................................................................. 21 5.1.4 Implementation/Validation Trials ............................................................................ 22


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5.2 Ultrafoam GX® System ........................................................................................................ 22 5.2.1 Background ............................................................................................................ 22 5.2.2 Development Trials ................................................................................................ 22 5.2.3 Demonstration Trials .............................................................................................. 23 5.2.4 Implementation/Validation Trials ............................................................................ 23

5.3 Other Mechanical Injection Systems .................................................................................... 24

6 FIELD TRIALS OF FOAMING TECHNOLOGIES USING WATER-BEARING ADDITIVES ......................................................................................................................... 25

6.1 Aspha-Min® ......................................................................................................................... 25 6.1.1 Background ............................................................................................................ 25 6.1.2 Development Trials ................................................................................................ 25 6.1.3 Demonstration Trials .............................................................................................. 25 6.1.4 Implementation/Validation Trials ............................................................................ 26

6.2 Advera®............................................................................................................................... 26 6.2.1 Background ............................................................................................................ 26 6.2.2 Development Trials ................................................................................................ 26 6.2.3 Demonstration Trials .............................................................................................. 26 6.2.4 Implementation/Validation Trials ............................................................................ 27

7 FIELD TRIALS OF CHEMICAL ADDITIVE TECHNOLOGIES ............................................ 29

7.1 Evotherm® ........................................................................................................................... 29 7.1.1 Background ............................................................................................................ 29 7.1.2 Development Trials ................................................................................................ 29 7.1.3 Demonstration Trials .............................................................................................. 30 7.1.4 Implementation/Validation Trials ............................................................................ 31

7.2 HyperTherm® ...................................................................................................................... 33 7.2.1 Background ............................................................................................................ 33 7.2.2 Development Trials ................................................................................................ 33 7.2.3 Demonstration Trials .............................................................................................. 34 7.2.4 Implementation/Validation Trials ............................................................................ 34

7.3 Rediset® WMX .................................................................................................................... 35 7.3.1 Background ............................................................................................................ 35 7.3.2 Development Trials ................................................................................................ 35 7.3.3 Demonstration Trials .............................................................................................. 35 7.3.4 Implementation/Validation Trials ............................................................................ 35

7.4 CECABASE RT® ................................................................................................................. 36 7.4.1 Background ............................................................................................................ 36 7.4.2 Development Trials ................................................................................................ 36 7.4.3 Demonstration Trials .............................................................................................. 36 7.4.4 Implementation/Validation Trials ............................................................................ 37

7.5 Sasobit® .............................................................................................................................. 37 7.5.1 Background ............................................................................................................ 37 7.5.2 Development Trials ................................................................................................ 37 7.5.3 Demonstration Trials .............................................................................................. 39 7.5.4 Implementation/Validation Trials ............................................................................ 39

7.6 Asphaltan B ......................................................................................................................... 41 7.6.1 Background ............................................................................................................ 41 7.6.2 Development and Demonstration Trials ................................................................. 41 7.6.3 Implementation/Validation Trials ............................................................................ 41

7.7 LEADCAP® ......................................................................................................................... 41


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8 FIELD TRIALS OF COMBINED BINDER MODIFIER-ORGANIC ADDITIVE TECHNOLOGIES ................................................................................................................ 43

8.1 Shell Thiopave® .................................................................................................................. 43 8.1.1 Background ............................................................................................................ 43 8.1.2 Development Trials ................................................................................................ 43 8.1.3 Demonstration Trials .............................................................................................. 44 8.1.4 Implementation/Validation Trials ............................................................................ 44

9 FIELD TRIALS IN AUSTRALIA AND NEW ZEALAND ....................................................... 46

9.1 Australia ............................................................................................................................... 46 9.1.1 Brisbane City Council ............................................................................................. 46 9.1.2 Department of Transport and Main Roads (TMR) Queensland ............................... 46 9.1.3 Roads and Maritime Services (RMS) NSW ............................................................ 47 9.1.4 Department of Planning, Transport and Infrastructure (DPTI), South Australia ....... 48 9.1.5 VicRoads ................................................................................................................ 48 9.1.6 Main Roads Western Australia (MRWA)................................................................. 49 9.1.7 Northern Territory Department of Transport (DOT) ................................................. 50 9.1.8 Department of Infrastructure, Energy and Resources (DIER) Tasmania................. 50 9.1.9 Department of Territory and Municipal Services (TAMS) ACT ................................ 50 9.1.10 Industry .................................................................................................................. 50

9.2 New Zealand........................................................................................................................ 50 9.2.1 Hayward and Pidwerbesky ..................................................................................... 50 9.2.2 Ball ......................................................................................................................... 52

10 ON-GOING STUDIES AND IMPLEMENTATION OF WMA PRACTICES ........................... 53

10.1 On-going Studies and Implementation of WMA Practices in USA ........................................ 53 10.1.1 Laboratory and Field Trials of WMA Technologies ................................................. 53 10.1.2 National Studies of WMA Technologies ................................................................. 54 10.1.3 Implementation of WMA Practice in the USA ......................................................... 56

10.2 On-going Studies and Implementation Practices in Europe .................................................. 57 10.3 On-going Studies and Implementation Practices in Asia ...................................................... 57

10.3.1 Korea: Development of WMA Production and Construction Methods ..................... 57 10.4 Implementation of WMA Practices in Australia ..................................................................... 58

10.4.1 Proposed Further Studies to Implement WMA Practices in Australia ...................... 58 10.4.2 Revisions to WMA Protocol .................................................................................... 58

11 CONCLUSIONS .................................................................................................................. 59

REFERENCES ............................................................................................................................. 62


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TABLES Table 2.1: Commercially available WMA technologies .............................................................. 4 Table 2.2: WMA technologies using sequential mixing stages of aggregate coating

and binder foaming .................................................................................................. 5 Table 2.3: WMA foaming technologies using water-based mechanical system ......................... 6 Table 2.4: WMA foaming technologies using water-bearing additives ....................................... 7 Table 2.5: WMA technologies using chemical additives ............................................................ 8 Table 2.6: WMA technologies using organic additives .............................................................. 9 Table 2.7: WMA technologies using combined chemical and organic additives ........................ 9 Table 3.1: Laboratory assessment methods used in asphalt mix design in different

countries ................................................................................................................ 11 Table 8.1: Composition of Shell Thiopave® asphalt test sections at NCAT test track.............. 45


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SUMMARY The Australia Government has set a target of reducing greenhouse gas (GHG) emissions by 25% by 2020 compared with 2000 levels assuming there is global agreement to an ambitious program to stabilise the levels of GHGs in the atmosphere. Australia has undertaken to unconditionally reduce its emissions by 5% compared with 2000 levels by 2020 and by up to 15% by 2020 if the global agreement falls short of securing atmospheric stabilisation at 450 ppm carbon dioxide equivalent (CO2-eq). The aim in the longer-term is, by 2050, to reduce GHG emissions in Australia by 80% compared with the 2000 levels.

The asphalt industry, like any other, wants to manage and use resources efficiently and continually improve their environmental performance. Reducing greenhouse gas emissions that contribute to global warming is of increasing interest and concern to the industry. Industry across all sectors can achieve a significant reduction in CO2-eq emissions by improving energy efficiency in their manufacturing processes. Unlike other pavement construction processes, asphalt requires that the aggregates and bituminous binders be heated and dried in its production process. This is an energy intensive production process.

Although construction sector emissions represented only about 1.5% of overall greenhouse emissions in Australia in 1997–98, this sector is showing a willingness to adopt strategies that will lead to the use of energy more efficiently and respond to the challenge of meeting emissions targets to avoid dangerous climate change. In a practical sense this means more sustainable and less carbon intensive products and processes, which are recognised within procurement policies and valued by infrastructure construction and maintenance practitioners.

On behalf of its members Austroads sponsored a project (TT1454: Performance of Warm Mix Asphalt Pavements) to evaluate WMA technologies for Australian road conditions. A major element of the project was the planning and conduct of a comprehensive field validation assessment of a range of WMA and hotmix asphalt (HMA) surfacings in order that their performance could be compared and a draft WMA Evaluation Protocol for the conduct of validation trials assessed and appropriate changes made. An extensive laboratory testing program was also conducted to support the validation trial.

This report presents a review of field trials of WMA technologies conducted in various countries in the world, with the emphasis on performance differences between WMA and conventional HMA and the identification of field performance data that could be used to complement the Austroads WMA evaluation field trials for Australian road conditions.

A large number of demonstration or validation trials of WMA technologies have been established in the USA to demonstrate the benefits of WMA technology compared to HMA, and to improve the quality and efficiency of construction (i.e. improved workability, improved compaction and more consistent field density). These trials have demonstrated that most WMA technologies associated with chemical and organic additives can be successfully implemented with minor modifications to the asphalt plant and, in the case of several products, successful paving could still occur at low temperatures.

The amount of published material relating to demonstration or validation trials in Australia is extremely limited. Despite this, however, the use of some WMA technologies is now being accepted by many road agencies.


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1 INTRODUCTION The Australia Government has set a target of reducing greenhouse gas (GHG) emissions by 25% by 2020 compared with 2000 levels assuming there is global agreement to an ambitious program to stabilise the levels of GHGs in the atmosphere. Australia has undertaken to unconditionally reduce its emissions by 5% compared with 2000 levels by 2020 and by up to 15% by 2020 if the global agreement falls short of securing atmospheric stabilisation at 450 ppm carbon dioxide equivalent1 (CO2-eq). The aim in the longer-term is, by 2050, to reduce GHG emissions in Australia by 80% compared with the 2000 levels.

Emissions in Australia are projected to average about 580 Mt CO2-eq per year from 2008 to 2012, or 106% of the 1990 levels. Without further policy action, Australia's emissions are projected to continue to increase. By 2020, emissions are projected to reach 686 Mt CO2-eq, or 24% above the 2000 levels. Australia's unconditional target of 5% represents a 23% decline below ‘business as usual’ (Department of Climate Change and Energy Efficiency 2010).

The Australian Government has introduced a carbon pricing scheme that takes effect from 1 July 2012. The Clean Energy Bill 2011 was passed in the Lower House in October 2011. The carbon price will commence at $23 per tonne and be fixed for the first three years. On 1 July 2015 the carbon price will transition to a fully-flexible price under an emissions trading scheme where the carbon price will be determined by the market. Under the scheme, about 500 of Australia’s largest emitters will be required to buy permits for each tonne emitted.

The asphalt industry worldwide is committed to reducing the impacts of its operations on global warming and there are many global agreements and national and state legislative requirements which industry is obliged to meet. For example, the European Union (EU) is committed to reducing greenhouse gases under the terms of the Kyoto Agreement. There are also potentially attractive competitive advantages if lower-cost, reliable technologies can be developed and implemented.

The Australian asphalt industry wants to manage and use resources efficiently and to continually improve its environmental performance. Reducing greenhouse gas emissions that contribute to global warming is of increasing interest and concern to the industry. Industry across all sectors can achieve a significant reduction in CO2-eq emissions by improving energy efficiency in their manufacturing processes. The main source of emissions in the asphalt sector arises from the heating and drying of aggregates.

Although construction sector emissions represented only about 1.5% of overall greenhouse emissions in Australia in 1997–982, this sector is showing a willingness to adopt strategies that will lead to using energy more efficiently and to respond to the challenge of meeting emissions targets to avoid climate change. In a practical sense, this refers to the use of more sustainable and less carbon-intensive products and processes, which are recognised within procurement policies and valued by infrastructure construction and maintenance practitioners.

There are several products comprising warm mix asphalt (WMA) being used in Australia and overseas. From an Austroads Member Authority perspective these need to be better understood in terms of their relative environmental benefits and performance, including structural performance. All the issues associated with the adoption of WMA also need to be fully explored and understood. 1 Carbon dioxide equivalent (CO2-eq) is a way of converting all greenhouse gases to a single value for ease of

comparison. It is calculated by multiplying the mass of a gas by its global warming potential. 2 Based on 1997–98 figures, the direct greenhouse gas emissions generated by the construction industry comprised

1.46% of the national emissions (Trewin 2003, p. 644).


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1.1 Austroads Project TT1454 Austroads sponsored a project (TT1454: Performance of Warm Mix Asphalt Pavements) to evaluate WMA technologies for Australian road conditions. The project involved the following components:

1. The development of a WMA Evaluation Protocol, the purpose of which is to provide a guide to the evaluation of specific WMA technologies and processes such as additives, surfactants and foamed bitumen. The Protocol sets out the conduct of appropriate laboratory tests and field validation projects in order that the performance of WMA and conventional HMA can be compared. The Protocol is an evaluation tool only; it is not a specification. One of the main outputs of this project is the final version of the Protocol.

2. A literature review of existing CO2 emission calculators with a view to recommending a system for inclusion into the WMA Evaluation Protocol. These include tools to determine the carbon footprint of road infrastructure and life cycle analysis methodologies to assist with materials and technologies selection. This will facilitate a more consistent approach to the calculation of carbon footprints.

It was concluded that, in the absence of sufficient Australian-based emissions factors, it was premature to recommend a carbon calculation system for inclusion in the Austroads WMA Evaluation Protocol. However, the recent work of the Transport Authorities Greenhouse Group (TAGG) in coordinating the development of a greenhouse workbook and calculator, and the recommendation that it be adopted as a national standard, means that any further work would need to be in line with this recommendation.

3. A review of field trials of WMA technologies conducted in various countries in the world, with the emphasis on field performance data that could be used to complement the Austroads WMA evaluation field trial.

4. The planning and conduct of a comprehensive field assessment of a range of WMA and HMA surfacings in order that their performance can be compared and the draft Evaluation Protocol for the conduct of validation trials assessed and appropriate changes made. An extensive laboratory testing program was also conducted.

This report addresses Task 3 of this project. It is an update of an earlier report which was endorsed for publication by Austroads in December 2011. However, it was agreed that a review of relevant material presented at the 2nd International Conference on Warm Mix Asphalt Pavements, held in St Louis in October 2011, should be added to that report before it was published. More than 40 papers were presented at that conference. They provided a comprehensive overview of the latest developments and implementation of WMA technology in the USA, Canada, Europe, Asia and South Africa. In his opening remarks, Greg Nadeau, Deputy Administrator, Federal Highway Administration (FHWA), reported that more than 40 million tons of WMA was produced in the USA in 2010, with market share reaching double digits (Nadeau 2012). At the time of the conference 41 State Departments of Transportation had specifications or contract language that allowed WMA, with a further six States indicating that they would be adopting specifications by December 2011.

The project was strongly supported by the Australian Asphalt Pavement Association (AAPA), members of which made extensive in-kind contributions to the laboratory and field testing elements of the project. The project was also strongly supported by VicRoads who also made a substantial in-kind contribution to the trial.


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2 WARM MIX ASPHALT 2.1 General Warm mix asphalt (WMA) technologies involve additives and/or production processes which allow the temperature at which asphalt mixes can be produced and placed to be reduced – typically by 20–50 °C below that of hotmix asphalt (HMA). The reduction in energy associated with asphalt production at a lower temperature results in a reduction in greenhouse gas emissions. For example, D'Angelo et al. (2008) reported that the reductions in plant stack emissions from WMA production were very significant: 20–40% reduction in carbon dioxide (CO2), 20–35% reduction in sulphur dioxide (SO2), 10–30% reduction in carbon monoxide (CO), up to 50% reduction of volatile organic compounds (VOC) and 60–70% reduction in nitrous oxides (NOx). In terms of laboratory studies, Mallick, Bergendahl and Pakula (2009) reported a 32% reduction in CO2 when the WMA mixing temperature was lowered by 20 °C.

In Australia, about 390 000 tonnes of CO2 are generated annually from the eight million tonnes of asphalt produced (Jenny 2009). A reduction in production temperature through the use of WMA technologies would roughly translate to a reduction of more than 120 000 tonnes of CO2 per annum. This is a potentially significant impact on the Australian CO2 balance.

As WMA technologies (new additives and/or production processes) can have similar transport and workability characteristics as HMA, they can be used as a compaction aid for stiff mixes. Other advantages associated with a reduction in asphalt production and compaction temperatures include: improved conditions for operators (less fumes), reduced binder aging during production, improved operational efficiency (earlier trafficking), extended paving seasons (paving in cool weather and/or at night) and the potential to increase haulage distances if the temperature of production is not lowered.

The concept of WMA originated in Europe in the early 1990s and, since then, a variety of technologies have emerged. Over the last five years, several new WMA technologies have been developed in the USA. Currently, WMA is being evaluated, and increasingly used, as a replacement for traditional HMA in many countries. Several WMA technologies have already been introduced into Australia.

It is important that the widespread and successful adoption of this technology in Australia is supported by a thorough understanding of overseas experience and the review of the performance of WMA under Australian conditions. Differences between current HMA practices (associated with material selection, material characterisation (specification requirements and performance-related laboratory testing), mix design, construction processes and standards and pavement design methodologies used in Australia, Europe and the USA might affect the approach to the implementation of WMA technologies in Australia.

2.2 Commercially-available WMA Technologies The various commercially-available WMA technologies examined in this review are presented in Table 2.1. More details of each WMA technology can be found in the websites provided by the manufacturers (as listed in the Table). Most of the technologies were assessed in terms of laboratory and field validation trials reported as being satisfactory and replicating the relevant HMA specification requirements and early life performance characteristics.


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There are now at least 21 registered WMA technologies in the USA (compared to only three in 2005) and 45 States are currently conducting demonstration trials of WMA technologies (compared to 15 States in 2007).

Table 2.1: Commercially available WMA technologies

Category Product / process Supplier Web address Availability of

laboratory / field validation trials

Sequential aggregate coating and binder foaming (Section 2.3.1)

Low energy asphalt (LEA1) LEA-CO (France) www.lea-co.com Yes

Low emission asphalt (LEA2)

Suit-Kote (McConnaughay) Corporation (USA

www.lowemissionasphalt.com Yes

WAM-foam® Shell International (UK) / Kolo-Veidekke (Norway)

www.shell.com/bitumen Yes

Water-based binder foaming (Section 2.3.2)

AQUABlack® Maxam Equipment, Inc. (USA) www.maxamequipment.com Not reported herein Double Barrel® Green Astec Industries (USA) www.astecindustries.com Yes

Terex® WMA Terex® Corporation (USA) www.Terex®rb.com Not reported herein Ultrafoam GX® Gencor Industries, Inc. (USA) www.gencorgreenmachine.com Yes

Binder foaming with water-bearing additive (Section 2.3.3)

Advera® WMA PQ Corporation (USA) www.Advera®wma.com Yes Aspha-Min® Eurovia Services GmbH

(Germany) www.Aspha-Min®.com Yes

Chemical additive (surfactants / emulsions) (Section 2.3.4)

CECABASE RT® Arkema Group (France) www.cecachemicals.com Yes Evotherm®

Evotherm® 3G Evotherm® DAT

MeadWestvaco Asphalt Innovations (USA)

www.evotherm.com Yes

HyperTherm® Coco Paving Inc. (Canada) www.cocoasphaltengineering.com Yes Rediset® WMX Akzo Nobel NV

(The Netherlands) www.surfactants.akzonobel.com Yes

Organic additives (Section 2.3.5)

Asphaltan B Romonta GmbH (Germany) www.romonta.de Yes Sasobit® Sasol Wax (South Africa) www.sasobit.com Yes

LEADCAP® Kumho Petrochemical (Korea) www.leadcapwma.com Yes Combined binder modifier / and organic additives (Section 2.3.6)

Shell Thiopave® Shell www.shell.com Yes

TLA-X® Trinidad and Tobago Ltd www.trinidadlakeasphalt.com Not reported herein

2.3 Categories of WMA Technologies The various commercial WMA technologies (Table 2.1) that are readily available can be grouped into six main categories:

sequential aggregate coating and binder foaming techniques

binder foaming using water-based mechanical systems

binder foaming using water-bearing additives

chemical additives

organic additives

combined chemical-organic additives.

http://www.leadcapwma.com/


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They use different additive contents (which may affect the WMA mechanical properties), different aggregate drying temperatures (which may affect bitumen-aggregate bonding and moisture susceptibility), different maximum bitumen temperatures (which may affect long-term asphalt durability and performance) and different requirements in terms of plant modifications (which may affect cost, production efficiency and product consistency). It should be noted that other cold mix and half-WMA technologies, which use a low binder temperature below 100 °C in production (e.g. WMA-emulsion which uses bitumen emulsion at 85 °C for the hard binder component (Preston 2007), are not considered as WMA technologies in this report.

2.3.1 Sequential Aggregate Coating and Binder Foaming Technology WMA technologies that involve sequential mixing stages of aggregate coating and binder foaming are presented in Table 2.2. This category includes some early foaming technologies developed in Europe (WAM-foam®, low energy asphalt, low emission asphalt). They employ different mixing stages of aggregate coating and binder foaming. In these technologies, the effective coating of the aggregates is considered critical in order to prevent water (which is added to produce foamed asphalt) from reaching a poor binder-aggregate interface (which could lead to moisture sensitive issues for the asphalt mixes).

Table 2.2: WMA technologies using sequential mixing stages of aggregate coating and binder foaming

Technology Manufacturer Description Plant modification

Additive dosage

Production / compaction temperature

Reported use

Low energy asphalt (LEA1)

LEACO, Fairco, and EIFFAGE

Travaux Publics and Appia (France), Advanced Concept

Engineering (US)

Sequential coating process where coarse aggregate is coated

with hot binder, followed by addition of

cold wet fine aggregate to create

foaming action developed in 2005

Significant plant modification for

adding and foaming processes

(US$75 000– $100 000)*

Water (13 kg/tonne); coating and

adhesion agent (0.2–0.5% by

weight of binder)

Tprod = 90 °C Tcomp = 60–90 °C

France, Spain, Italy,

USA (> 90 road

trials > 125 000

tonnes)

Low emission asphalt (LEA2)

McConnaughay Technologies

(USA)

As in LEA with chemical additive added to the hot

coarse aggregates As above

Water and adhesion agent

(assumed similar to LEA1)

Tprod = 90–95 °C Tcomp = 60 °C

Canada, USA,

New Zealand

WAM-foam®

Kolo Veidekke, Shell Bitumen (patent rights

worldwide, except USA)**

BP (patent rights USA)

Two-stage process where softer binder

(for aggregate coating) and harder foamed binder are mixed separately

Significant plant modification for

adding and foaming processes

(US$60 000– $85 000)

Water (2–5% by mass of hard

bitumen fraction, about

0.7 kg/tonne); surfactant and

an anti-stripping agent may be

added

Tprod = 100–120 °C Tcomp = 80–100 °C

France, Norway, Italy, Luxembourg, Netherlands,

Sweden, Switzerland, UK, Canada,

USA

* Currently (June 2012), the value of the US$ and A$ is approximately the same. ** WAM-foam® (Shell) is available from Citywide in Melbourne. It is marketed as GreenPave®. For example, the WAM-foam® technology employs a two-stage mixing process: in the first stage, the coarse aggregates are heated at a low temperature (110 °C) and pre-coated using a hot, soft binder (with or without adhesion additive); the second mixing stage includes a hot hard binder in foamed form. In the foaming action, the water turns to steam, thus increasing the volume of the bitumen and reducing its viscosity for a short period until the temperature of the material drops below 100 °C, i.e. where the stream condenses to water. This improves mix workability and allows for improved compaction at a lower temperature.


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The LEA techniques also employ sequential mixing stages. In the first stage the coarse aggregates are heated (at a temperature of 120–150 °C) and pre-coated using a hot hard binder with liquid chemical coating/adhesion additive. The second mixing stage includes an additional wet fine sand (with high water content) to foam the pre-coated hard binder. This foaming technology uses a high water dosage (e.g. LEA uses up to 13 kg water per tonne of mix) for the foaming action at production temperatures below 100 °C. As the large dose of water added in this process could negatively influence the moisture susceptibility of mixes, coating/adhesion and anti-stripping agent are often added to reduce stripping potential. Most existing HMA plants require some modifications to allow for the sequential mixing stages of aggregate coating and binder foaming.

2.3.2 Binder Foaming Technology Using Water Based Mechanical Systems Examples of binder foaming using water-based mechanical systems are presented in Table 2.3. This category includes various technologies (Double Barrel® Green, Ultrafoam GX®, AQUABlack® foam and Terex® Warm Mix Asphalt System) which employ mechanical techniques to introduce small amounts of free water (or steam) into the hot bitumen to produce foamed asphalt suitable for a medium production temperature (say between 120–140 °C). For example, Double Barrel® Green involves the use of a mechanical nozzle to inject water into a much smaller dose (at a rate of 1 kg of water per tonne of mix) into the hot binder stream for foaming action at a medium temperature range (120–140 °C). The aggregates are heated to a nominal 130–135 °C and the binder is added at a nominal 160 °C, resulting in WMA at 135 °C. As the water content added is very low, no additional chemical coating/adhesive additive is required to promote coating. However, an adhesion agent may be added to improve adhesion.

Table 2.3: WMA foaming technologies using water-based mechanical system


Additive dosage


Reported use

Double Barrel® Green

Astec Industries (USA)

A nozzle to inject a small amount of water into the

hot binder stream to create foaming action

Significant (installation of mechanical pumps and nozzles and

control system)

Water (1 kg/tonne)

Tprod = 120–140 °C Tcomp = 115 °C

USA Developed in

2007

Greenmachine Ultrafoam GX®2

GenCorp Industries (USA)

Pumps to supply the bitumen; steam is injected

into the center of the bitumen flow to create

foaming action

Water (1.25–2% by weight of total

bitumen) NA USA

AQUABlack® WMA

Maxam Equipment

(USA)

High-pressure foaming gun (7000 kPa) using

MicroBubble™ technology

Water (1/4 cup of water per

tonne) NA USA

Warm Mix Asphalt System

Terex® Roadbuilding

(USA)

Foamed asphalt produced outside of drum &

immediately injected into drum's mixing chamber

NA Up to 30 °C below HMA USA

These processes may have less negative influence on the moisture susceptibility of mixes compared with low-temperature aggregate drying and foaming technologies using a high water dosage. The foamed asphalt also has greater workability and allows for improved compaction at temperatures above 100 °C. Most existing HMA plants require significant modifications to add the water into the system for the foaming process. They therefore incur the highest initial modification costs but the lowest costs for additives compared to other WMA technologies.


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2.3.3 Binder Foaming Technology Using Water Bearing Additives Technology involving binder foaming using water-bearing additives is shown in Table 2.4. This category includes two technologies (Advera® and Aspha-Min®) which involve the addition of zeolite (containing about 20% water of crystallisation) to the mix at the same time as the binder. At a mix temperature of about 130–135 °C, zeolite slowly releases water to create foamed asphalt and, hence, provides greater workability. As the amount of zeolite water added into the system is very small (about 0.65 kg of water per tonne of mix), the WMA products may have less negative influence on the moisture susceptibility of mixes compared with low-temperature foaming technologies which involve the use of a high water dosage. However, an adhesion agent may be added to improve adhesion. During the foaming step, the zeolite can generally be added to the mix at the same time as the binder through a spare filler silo (if available). Otherwise, some minor modifications may be required.

Table 2.4: WMA foaming technologies using water-bearing additives

Technology Manufacturer Description Plant modification Additive dosage Production / compaction temperature

Reported use

Advera® PQ Corporation (USA)

Manufactured Zeolite which

releases water during production, creating foaming

action

Some (to add the material to the mix at the same time as

the binder and include foaming

steps) US$5 000–$40 000

Water (0.7 kg/tonne) from Zeolite

(0.25% by total weight of mix) US$1.35/kg

Tprod = 140–150 °C Tcomp = 120 °C

(10–20 °C below HMA)

USA

Aspha-Min® Eurovia Services GmbH

Synthetic Zeolite powder which releases water

during production, creating foaming

action

Water (0.7 kg/tonne) from Zeolite

(0.3% of total mix by mass)

US$0.60/lb (US$0.27/kg)

Tprod = 125–150 °C Tcomp = 100–130 °C (30 °C below HMA)

France, Germany,

USA

2.3.4 Chemical Additives This category includes various technologies (Evotherm®, Evotherm® 3G, HyperTherm®, Rediset®, CECABASE, SonneWarmixTM) which use chemical additives (Table 2.5).

The chemical additives do not change the bitumen viscosity, but act as surfactants to regulate and reduce the frictional forces at the microscopic interface of the aggregates and the bitumen at a range of temperatures, typically between 85 °C and 140 °C.

It is therefore possible to mix the bitumen and aggregates, and to compact the mix, at lower temperatures (about 20–30 °C) than those associated with HMA. Depending on the product, the chemical additives can be added directly to the binder or the hot bitumen emulsion or mixed with water to form a liquid so that it can be injected into the stream just before the mixing chamber. The way the additive is added is specific to each product, e.g. Evotherm® 3G is added to the binder.


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Table 2.5: WMA technologies using chemical additives

Technology Manufacturer Description Plant modification Additive dosage


Reported use

Evotherm® MeadWestvaco

Asphalt innovation

Chemical package of emulsification agents

and anti-stripping agents

Minor (applied along with emulsion over 100 °C) (US$1000–

$5000)

Large amount of water in emulsion (25 kg/tonne) and

chemical (not known) (7–10%

higher than conventional

binder)

Tprod = 100–130 °C Tcomp = 60–115 °C (50–75 °C below

HMA)

France also Canada, China, South

Africa and USA

Evotherm® DAT®

MeadWestvaco Asphalt

innovation

Chemical package of surfactants and

anti-stripping agents diluted with small amounts of water

Minor (injected to binder line)

0.3–0.5% surfactants, 0.3–0.5%

anti-stripping agents and 5%

w/w asphalt

Tprod = 115–120 °C Tcomp = 100–105 °C

Canada, USA

Evotherm® 3G MeadWestvaco

Asphalt innovation


anti-stripping agents; does not contain

water

Minor (added to binder at terminal)

Nominal 0.5%

Tprod = 135–140 °C Tcomp = 115–120 °C

Canada, USA

HyperTherm® Coco Paving Inc.


anti-stripping agents; does not contain

water

Minor (injected to binder line)

0.2% by mass of binder

Tprod = 130 °C Tcomp = 110 °C

Canada, also USA

(QualiTherm)

Rediset® Akzo Nobel Chemical additives in pellet form; does not

contain water

Minor (added to the

binder) 1.5–2% by mass

of binder

Tprod = 120 °C (22–33 °C below

HMA) Tcomp = 120 °C

(40–75 °C below HMA)

USA

CECABASE Arkema Group (France)

Additive containing surface active agents composed of at least 50% renewable raw materials (chemical

additives in wax-based liquid form)

Minor (added to the

binder) 2–4% by mass of

binder


(50 °C below HMA)

Developed in 2003

80 ktonne in Europe in

2006

SonneWarmixTM Sonneborn (USA)

Additive containing paraffinic hydrocarbon

Minor (added to the

binder) Typically 1–1.5% by mass of binder

Tprod = 125–135 °C Tcomp= 110–120 °C

USA (previously AD-RAP)

2.3.5 Organic Additives This category includes several technologies (Sasobit®, Asphaltan B) which involve the addition of organic additives to the binder to lower the viscosity of the binder (bitumen) at compaction temperatures, thus increasing the workability of the compacted mix (Table 2.6). The type of additive must be selected carefully in order that its melting point is higher than the expected in-service temperatures (otherwise permanent deformation may occur) and to minimise embrittlement of the asphalt at low temperatures. The organic additives, usually waxes or fatty acid amides, are in granular form and can be added either to the mixture or to the bitumen. However, they are more effective when dispersed in the binder prior to manufacturing the WMA. No water is required in this process.


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LEADCAP®, produced by Kumho Petrochemical in Korea, is a relatively new product. Trials have commenced in the USA and Asia as discussed in Section 7.7.

Table 2.6: WMA technologies using organic additives


Additive dosage and

cost


Reported use

Sasobit® Sasol Wax (Germany)

Synthetic wax produced from

coal gasification using the FT

process

Minor (pre-blended with

the binder, or added dry to the

mix)

No water; wax (0.8~3% of

binder by mass)* 2000 €/tonne**

Tprod = 115–130 °C Tcomp = 80 °C

Germany and 20 other countries

worldwide, including Australia*

Asphaltan B Romonta

GmbH (Germany)

Wax extracted from coal

No water, wax (2~4% of

binder by mass) Germany

LEADCAP® Kumho Petrochemical

Pellets in paper bag or jumbo

bag No 1.5~2% into

binder

Tprod = 120~130 °C Tcomp = 60–115 °C (30~40 °C below

HMA)

USA, Japan, Portugal, Italy,

Thailand, China and Korea

* Generally 1.0–1.5% is used. ** €1 ≈ A$1.25 (June 2012).

2.3.6 Combined Chemical and Organic Additives This category includes several technologies (Thiopave®, TLA-X®) which add both chemical and organic additives to the binder (Table 2.7). The chemical additive (e.g. sulphur) will improve the performance of the binder, whereas the organic additives will lower the viscosity of the binder (bitumen) at compacting temperatures and hence increase workability. The type of combined additives, and their proportions in the mix, must be selected carefully to achieve optimum levels of improved asphalt performance and improved workability at lower compaction temperatures.

Table 2.7: WMA technologies using combined chemical and organic additives

Technology Manufacturer Description Plant modification Additive dosage


Reported use

Shell Thiopave® Shell

Combination of sculpture, plasticiser and other additives

Minor (for use in most batch and drum

mix plants)

Up to 25% by mass of bitumen


150 ktonne in 2010, USA

TLA-X® Trinidad and Tobago Ltd

Uncoated and coated pellets with binder stiffening additive*

Minor NA NA USA

* The combined chemical and Torganic additives are usually incorporated in pellet form and can be added either to the mixture or to the bitumen.


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3 FIELD TRIALS OF WMA TECHNOLOGIES

3.1 Introduction Over the last ten years, there have been a large number of field validation trials of WMA technologies established all over the world by private industry (manufacturers or contractors who now own the patent rights to use those WMA technologies) and road agencies. At the time of completing this report (May 2012), more than 160 documents had been identified in a literature search of WMA technologies reporting field trials of some form or another in the USA, Canada, Europe, Asia, South Africa and Australasia.

Of the approximately 160 references sourced, only about 20% provided sufficient information for them to be classed as validation/implementation trials. Most were development or demonstration trials established to evaluate a product or process in general terms only. Emphasis in this report is placed on the validation/implementation trials. Other sources claimed to be validation or implementation trials but insufficient detail was provided to justify this definition. In other cases, the trials are just commencing and no performance data has yet been published.

In this report, the WMA technologies are grouped into the six different categories listed in Section 2.3 . Each category has similar features in terms of the additives/processes used to manufacture the mix and plant modifications required for incorporating the WMA technologies concerned. This should facilitate discussion on the framework adopted in field trials of WMA technologies and the reporting of the WMA field trials in the following sections.

3.2 Stages of Field Trials It was clear from the review that field trials of various WMA technologies have progressed through three stages in an attempt to gain acceptance by the road industry: development trial, production/demonstration trial, and validation/implementation trial. Each type of trial can have a different framework (scope, investigative method, verification criteria, etc.) depending on the technologies developed (i.e. additives/processes used to manufacture the mix and plant modification s required for these technologies), the asphalt producer’s marketing strategy and the road agency’s implementation strategy.

Some common frameworks applied in these three stages are now briefly described to facilitate the reporting of previous field trials of WMA technologies.

3.2.1 Development Trials The main aim of a development trial is to meet a manufacturer’s desire to obtain supporting evidences of material workability and performance for the purposes of developing the additives, processes and equipment prototypes used to produce a product (in this case WMA mixes).

The investigative works used during this stage include low-cost laboratory studies to assess workability and performance. In case where replicated samples can easily be produced in the laboratory (e.g. technologies using chemical and organic additives), the laboratory-prepared samples are often used in the laboratory testing program. However, if replicated samples cannot be manufactured in the laboratory without expensive equipment (e.g. foaming technologies), full-scale mixing plants and road trials are also used to produce production and field samples for laboratory testing.


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The laboratory assessment methods used in conventional HMA mix design, and their acceptance performance criteria, can also be used to assess the performance of WMA mixes. The laboratory assessment methods used in for the design of conventional HMA mixes vary between countries. The most common laboratory test methods used in different countries is presented in Table 3.1.

Table 3.1: Laboratory assessment methods used in asphalt mix design in different countries

Purpose Parameter Europe USA (SHRP/AASHTO) Australia

Mix design using Marshall procedure

Air voids, bulk density Stability Dynamic creep test Marshall stability and flow Marshall stability and flow

Workability Superpave gyratory compaction Gyratory compaction

Recovered asphalt binder Rolling Thin Film Oven

AASHTO T179–05 (2005)

Durability Californian abrasion test Particle coating Particle coating AASHTO T195–67 (2005)

Asphalt binder assessment

Rotational viscosity, Dynamic Shear

Rheometer, creep, stiffness

AASHTO M320–10 (2010) Effective and free binder

volume, fixed binder fraction, voids filled with

binder

Performance assessment

Deformation (rutting) Nottingham Asphalt Tester Hamburg Wheel Tracking

Device (HWTD)

Asphalt Pavement Analyser

AASHTO T324–04 (2004) Wheel tracking

Stiffness

AASHTO TP31–96 (1996) resilient modulus

AASHTO TP62–03 (2005) dynamic modulus

Resilient modulus (indirect tension)

Moisture susceptibility/stripping

potential Duriez test AASHTO T283 (2007) RMS/RTA T649

Cracking (fatigue) Asphalt Pavement

Analyser AASHTO T321–07 (2007)

Beam fatigue

In the USA for example, laboratory assessments of WMA are based on the Superpave and/or the AASHTO SHRP laboratory testing protocols used for HMA mix design. A series of samples are produced under different compaction temperatures so that the effect on volumetric properties can be assessed. A series of performance tests are then conducted. In Europe, laboratory assessments of WMA generally also include the determination of workability/compactability (using the gyratory compaction test), mix stability (using the dynamic creep test), abrasion resistance (using the Californian abrasion test) and resistance to permanent deformation (using the Nottingham Asphalt Tester (NAT)).

There is always some concern that some laboratory performance tests do not truly represent field performance. Therefore, a common strategy when testing both WMA and HMA samples is to use the same equipment, with samples prepared and tested by the same operators, to allow direct comparison between the results.

Most asphalt producers will generally proceed to the next demonstration (commercial) stage if the laboratory results obtained in the development trial show that:

The WMA has equal or better workability (at low temperatures) than conventional HMA (at high temperatures)


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when WMA and HMA have similar volumetric properties, the mechanical properties of WMA are similar to those of HMA, e.g. the modulus of WMA could be lower than the modulus of HMA and this will also impact on fatigue life.

It is also assumed that the asphalt producer will conduct the investigative works and control the reporting of the works. However, for reasons of commercial patents and confidentiality, the manufacturers often provide limited information externally. This may not allow a thorough analysis of the trials and the purchaser may be required to take claims of success at face value.

3.2.2 Production/Demonstration Trials The aim of a production/demonstration trial is to meet a road agency’s desire to obtain supporting field evidence of the production and placement of a specific WMA product for the purposes of quality control and assurance (in terms of day-to-day production from mixing plants, contractor laying experience, product consistency, material quality, etc.).

The works during this stage include field studies using full-scale mixing plants of reasonable size to allow a full run of plant-production (to achieve a commercial production rate), and a road trial of reasonable length (to enable an assessment of workability and field performance immediately after compaction).

Over the last few years, many demonstration trials of WMA technologies have been established in the USA (and other developed countries) to demonstrate the benefits of WMA technology compared to HMA, and to improve the quality and efficiency of construction (i.e. improved workability, improved compaction and more consistent field density). Demonstration trials are particularly popular for road applications involving overlays using high RAP content mixes and severe construction conditions (e.g. cold/wet environments). There have also been further developments and improvements in WMA technologies using water (e.g. foam technologies using water injection nozzles) and emulsions to reduce the amount of water added to the system.

The laboratory assessment methods used in the development trial stage (Section 3.2.1) are also used in the demonstration stage. In addition, and as just discussed, field testing is also carried out to validate the material quality and consistency (quality control) and assess short-term performance. It should be noted that different road agencies may require different evidence of production and placement and performance criteria in the field. Generally, the asphalt producer would conduct the field trials whilst both the asphalt producer and the road agency would conduct performance measurements.

A common strategy in the promotion of a new product is to include a ‘control’ HMA section in the demonstration trial which has the same specified asphalt mix and is placed under the same conditions (pavement, climate). This allows a direct comparison between workability and field performance of the WMA and HMA mixes.

Most road agencies would proceed to the next (validation/implementation) stage if the field results at the demonstration stage show that:

the field compaction of the WMA is equal to or better than the conventional HMA

in the case when field WMA and HMA samples have similar volumetric properties, the short-term field performance (observed after compaction) of the WMA is at least equal to that of the HMA.


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3.2.3 Validation/Implementation Trials The purpose of a validation/implementation trial is to address a road agency’s desire to obtain information regarding material workability and field performance (including both short-term performance after compaction and long-term performance over the design period) for the purposes of developing/validating mix designs (material specifications), construction standards and pavement design procedures. This stage may include a large number of field trials involving various asphalt mixes (binders, aggregate types, recycled asphalt pavement (RAP), etc.) and applications (pavement structure, traffic and environmental conditions, etc.).

A common strategy for reducing the number of required implementation field trials is to examine studies of previous, or existing, field trials in terms of their relevance to the issues being addressed. An example is the 2007 International Technology Scanning Program, in which a team of technologists from the USA examined WMA technologies currently in place in Europe (D’Angelo et al. 2008).

Many evaluation field trials of WMA technologies have been established in the USA to address various concerns regarding its use, including incomplete drying of the aggregate (especially with absorptive limestones), the potential for increased moisture susceptibility when utilising WMA processes that involve the use of water, the effects of chemical additives on the long term performance of the binder, the ability of WMA to provide enough radiant energy to heat the reclaimed asphalt component in mixes containing RAP, and the general lack of information regarding the long term performance of new asphalt mix designs (e.g. with high RAP content or rubber asphalt).

Examples of recent studies include Alossta et al. (2011), Barros (2009), Barros, Bressette and Johnson (2008), Barros, Jones and Peterson (2011), Bernier et al. (2011), Brown, Kvasnak and Neitzke (2008), Copeland, Gibson and Corrigan (2011), Diefenderfer and Hearon (2010), Reinke et al. (2011), Tabib, Raymond and Le (2011) and Willis et al. (2011).

In addition, several asphalt producers and road agencies have collaboratively conducted accelerated loading studies of the comparative performance of WMA and HMA technologies under heavy loading. Examples include the work at the National Center for Asphalt Technology (NCAT) in Auburn, Alabama (Prowell, Hurley & Crews 2007; Vargas-Nordcbeck & Timm 2011), and the work at the University of California Pavement Research Center (UCPRC) using the Heavy Vehicle Simulator (HVS) (Jones et al. 2008 & 2011; Jones, Wu & Barros 2010). These trials have involved the production of the mixes, the construction of test pavements, and the monitoring of field performance, including detailed (within-pavement) response-to-load data. In addition, extensive laboratory studies of both field and laboratory samples were carried out in order that the relative performance of WMA with HMA could be compared with recommendations made regarding the implementation of WMA in the current HMA mix design procedures.

Implementation field trials are the most expensive of the three options. As a result, evaluation protocols of WMA technologies involving the use of field trials have been established to maximise the benefits of these trials. For example, Newcomb and Corrigan (2006) developed a Material Test Framework for WMA Trials which was adopted by the US National Asphalt Pavement Association (NAPA) and the Federal Highway Administration (FHWA). An emissions testing framework and draft WMA construction specification has also been up-loaded onto this site.

The FHWA and NAPA are currently updating all three documents following consensus being recently agreed regarding test procedures, evaluation protocols and test section requirements. The emissions testing framework updates are based on the recently completed emissions and fuel


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measurement work conducted as part of the NCHRP Project 9-47A. The construction specification needs updates are based on the recently-completed WMA mix design recommendations work conducted as part of the NCHRP Project 9-43 project3. Brief details of these two projects, and NCHRP Project 9-49, are presented in Section 10.4.1.

A summary of recent field trials of various WMA technologies is presented in Section 4 to Section 8 of this report.

3.3 Draft WMA Protocols 3.3.1 Australia An evaluation protocol was drafted for adoption in Australia in 2010. The purpose of this protocol is to provide a guide to the evaluation of specific WMA technologies and processes such as additives, surfactants and foamed bitumen. The protocol sets out the conduct of appropriate laboratory tests and field validation projects in order that the performance of WMA and conventional HMA can be compared. The protocol is an evaluation tool only; it is not a specification.

The protocol is written in such a way that, as a type of WMA is evaluated, the results can be distributed and discussed across Australian States and New Zealand through the Austroads framework. It is expected that the use of this protocol will assist road agencies in the acceptance of the use of WMA without the need for additional testing and trials.

Whilst the protocol could be applied to any asphalt mix, including mixes containing RAP, the scope of the protocol is confined to wearing courses consisting of dense-graded asphalt and conventional binders.

The protocol addresses:

the testing of asphalt containing additives and surfactants, both in the laboratory and during production

the testing of asphalt containing foamed bitumen: during production only

desirable site conditions for a field validation site

the timeframe for the evaluation

data and information exchange.

It is assumed that the asphalt suppliers have conducted their own trials at the plant to ensure that the additives can be incorporated into the asphalt in a consistent manner and also to demonstrate that they are able to manufacture WMA at a specific plant.

3.3.2 South Africa A Best Practice Guideline for Warm Mix Asphalt has recently been issued in South Africa (Naidoo et al. 2011; South African Bitumen Association (SABITA) 2011a). The purpose of this guideline is to impart best practice in the design, manufacture and placement of WMA, based on local experience, as well as that gained from other countries where this process is used.

3 Details of all nine NCHRP projects are listed at http://www.trb.org/NCHRP/Public/NCHRPProjects.aspx.

http://www.trb.org/NCHRP/Public/NCHRPProjects.aspx


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It is a substantial document. Topics include:

Benefits of WMA – environmental, health and engineering and economic benefits.

Overview of the main categories of WMA.

Classification of WMA technologies, including a more detailed description of some of the technologies that are available in each of the categories, how they function and how they are utilised.

Considerations regarding HSE – similar precautions and procedures to those for HMA are recommended.

Handling and quality assurance of mix components including the milling, stockpiling, and preparation of reclaimed asphalt, as well as the handling of the various categories of WMA technologies.

Quality assurance of mix components including lists of appropriate tests to be undertaken on aggregates and fillers, reclaimed asphalt and binders.

The mix approval process, which comprises four distinct steps including laboratory mix design, full-scale plant mix design, and final approval based on consideration of all the results.

Manufacturing requirements for both batch and continuous drum mixer plants including binder storage facilities, a WMA technology addition system, and monitoring and control systems.

Quality assurance during the manufacturing process, including recommendations for the range of tests to be carried out on mixes sampled at the mixing plant.

Paving and compaction, including recommendations for equipment, preparation work and minimum paving conditions based on ambient air temperature, substrate temperature and wind speed.

Quality assurance at the paving site.

Protocol for introducing new WMA technologies. WMA technologies that have already been tested and thoroughly assessed by the Warm Mix Asphalt Interest Group are listed. The following three-phase approach to approving other new WMA technologies is recommended:

— Phase 1 – the WMA technology supplier provides full information on their product, including recommended usage, effect of varying dosage rates, materials safety data sheets, documentation of previous field applications, and temperature ranges for mixing and compaction.

— Phase 2 – carry out the four-step mix design approval process.

— Phase 3 – approval may be given by the Warm Mix Asphalt Interest Group after assessment of all the available information.

An interim WMA specification has been included as an annexure to the Guideline. The interim specification will be updated following the practical experience gained in its implementation.


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4 FIELD TRIALS OF FOAMING TECHNOLOGIES USING SEQUENTIAL AGGREGATE COATING AND BINDER FOAMING

4.1 WAM-foam® 4.1.1 Background The WAM concept of blending hard and soft binder components to reduce production temperature was developed by Shell Bitumen in 1996. Collaboration with Kolo-Veidekke in Norway led this work in a new direction when the hard bitumen component was added as foam. This led to the development of the WAM-foam® process, which is now patented and marketed worldwide (except in the USA) by Shell Bitumen (BP has patent rights for the technology in the USA).

In the WAM-foam® process, the coarse aggregates are heated to 110 °C and coated with about 20% of the total mass of hot, soft binder. The grade of the soft binder is selected to be applicable at this mixing temperature (as low as a viscosity of 1.5 Pa.s). Anti-stripping agents can also be added to the binder. The hard bitumen (approximately 70/100 pen PG 58/64-22 or Australian Class 170) is then foamed into the mix by adding water at ambient temperature at a rate of 2–5% by mass of the hard bitumen fraction (about 726 grams of water per tonne of mix) to the binder (at about 175–180 °C). As the steam expands (by a factor of about 1600), the resulting binder-water combination also expands (by a factor of about 15 times its original volume). The resulting mix temperature is between 100 and 120 °C and the foamed mix can be compacted at a temperature between 80 and 100 °C.

Both existing batch plants and drum plants need to be retrofitted to produce WAM-foam®. For a batch plant, the soft binder is added using the plant’s existing binder line and binder weight bucket. A foaming nozzle with an expansion chamber is added above the pugmill. A separate line is added to the plant to supply the hard binder. A mass flow meter controls the rate of addition for the hard binder. Since a batch plant is not a continuous process, it is important to clean the nozzle and expansion chamber with compressed air after each introduction of foam.

4.1.2 Development Trials As reported in Koenders et al. (2002), in the early developmental stage, dense WAM-foam® asphalt mixes were prepared in the laboratory to determine general workability/compactability (using gyratory compaction), mix stability (using the dynamic creep test), abrasion resistance (using the Californian abrasion test) and the resistance of the mix to permanent deformation (using the NAT). A comparison is always made with samples prepared using conventional processes. Koenders et al. found that, overall, the performance (stability and adhesion) of the WAM-foam® mixes manufactured in the laboratory was equal to that of the mixes manufactured using the traditional HMA procedures.

The first development field trial of WAM-foam®, involving the modification of an existing paver (Midland MixPaver) was conducted in May 1999. In this trial, bitumen foam was produced on the paver (bitumen and water tanks available), mixed with the aggregate and then laid on the road. Even though this trial was carried out under extremely adverse weather conditions (even some snowfall), the entire paving operation was carried out with satisfactory results (Koenders et al. 2002). In a second trial in May 2000, the asphalt was produced in a batch plant; foaming equipment built into the plant enabled the foamed bitumen to be introduced directly into the pugmill (Koenders et al. 2002).


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4.1.3 Demonstration Trials Larsen et al. (2004) reported that several demonstration field trials involving commercial production rates were conducted in Norway, Sweden and the UK during 2000–2004. An early WAM-foam® demonstration trial in Norway conducted in September 2000 included a section on a main road. A production trial of WAM-foam® in Norway in 2001 involved the use of a batch mixing plant and a continuous drum mixing plant for normal (commercial) paving works. It was noted that, compared to the few hours production during the previous field trials, the day-to-day production could provide more information on plant operational issues, particularly when operating at lower temperatures. Since then, many demonstrations have been established in Norway and other European countries as a means of checking production data.

In December 2007, a portion of State Route 11 in Deland, Florida, was milled and repaved with 45% reclaimed asphalt pavement (RAP). These high RAP mixes were produced at lower than normal hotmix temperatures using foamed WMA technology (Copeland et al. 2011). This project was the first large production in which the Florida Department of Transportation allowed the use of high RAP in combination with WMA. The FHWA, in cooperation with Florida DOT and NCAT, was on site for production and placement of the high RAP-WMA.

Plant-produced mix was collected by FHWA for performance testing evaluation. Two mixes were produced: a high RAP-HMA control and a high RAP-WMA. Performance tests conducted by the FHWA included performance grade (PG) determination of binders, dynamic modulus and flow number. The PG results indicated that the high RAP-WMA mix was softer than the high RAP-HMA control mix. This was further confirmed by flow number results, where the high RAP-WMA had a lower flow number than the high RAP-HMA control. The dynamic modulus results indicated that the high RAP-WMA was slightly softer than the high RAP-HMA, especially at intermediate temperatures. Copeland et al. (2011) reported that a comparison of the measured dynamic modulus results with modelling confirmed that, whilst complete blending occurred in the high RAP-HMA control mix, incomplete mixing of RAP and virgin binders may have occurred in the high RAP-WMA mix.

Johnston et al. (2007) reported a field trial of ‘warm-foam’ in Calgary, Canada, in 2005. In this trial, a similar concept to the WAM-foam® process (i.e. two-stage mixing of soft and hard binder) was adopted; however, production details (e.g. soft and hard binder components, mixing ratio, aggregate composition, etc.) appear to be different. The control mix was a Marshall 50 – blow designed HMA, using 150/200A penetration grade binder. Both the WMA and HMA mixes had similar characteristics in terms of aggregate composition, binder properties, volumetric properties, and in-place air voids. Various laboratory performance tests (rutting (Asphalt Pavement Analyzer), fatigue (AASHTO T321-07, 2007), repeated flexural bending, resilient modulus (AASHTO T283, 2007), resistance to moisture-induced damage, permeability) were conducted on the HMA and WMA samples. The testing showed that the rutting susceptibility and resilient modulus properties of the control mix were marginally superior to the warm-foam mix, whereas the fatigue properties of the warm-foam product were significantly greater than those of the control mix. It was also found that the warm-foam mix was more susceptible to moisture damage; as a result, moisture susceptibility could be an issue.


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4.1.4 Implementation/Validation Trials By 2007, there were 28 WAM-foam® trial sections in Norway, representing 17 800 tonnes of asphalt. However, as reported by D’Angelo et al. (2008) (who participated in the 2007 International Technology Scanning Program to survey WMA technologies in European countries), they only visited six sites in Norway with average daily traffic volumes ranging from 3500 to 25 000 vehicles. Of the sites visited, four were composed of dense-graded asphalt and two were SMA. All six sites included HMA control sections. It was reported in D’Angelo et al. (2008) that the Norway Public Roads Administration was conducting condition testing on all the WMA sites including roughness, texture, profile and rutting. Although poor performance was observed in limited WMA sections, it was not directly attributed to the use of WMA; where the performance of the WMA was poor, the performance of the HMA was also poor. It was also noted that the use of studded tyres caused significant wear to the pavement, manifesting itself in the form of rutting in both the HMA and WMA sections. It was therefore concluded that, overall, it appeared that the performance of the WAM-foam® sections was similar to the HMA sections.

4.2 Low Energy Asphalt (LEA1) 4.2.1 Background Low energy asphalt (LEA1) is a road building process that was developed by the French Company LEA-CO in 2000. It has been in use in France and much of the European Union since 2003. Two patented sequential mixing processes (enrobé à basse energize (EBE) and enrobé basse temperature (EBT)) were developed by Fairco and EIFF AGE Travaux Publics, respectively, to produce WMA. These two companies are cooperating in a joint venture, LEA-CO, to promote and market LEA1 in Europe, North America, and some other countries.

In one of the LEA1 processes, the coarse aggregate is dried and heated at a temperature of about 150–160 °C and coated with hot bitumen. Wet sand (as high as 40% of the total mix or 13 kg of water per tonne of mix) is then introduced into the mix. A coating and adhesion agent (0.2–0.5% by weight of binder) is also added. The moisture in the sand foams the bitumen, allowing the sand to be coated. The resulting mix temperature can be less than 100 °C and the foamed mix can be compacted at a temperature between 60 and 90 °C.

Existing HMA plants require significant modifications to produce LEA1 mixes. Advanced Concepts Engineering Co. (LEA-CO) has listed several examples showing how common HMA plants (continuous mixing plants, batch mixing plants, continuous plants with continuous pugmill mixer and continuous plants with drum dryer mixer) can be transformed and adapted to LEA1 production.

By 2007, the annual total production for WMA in France was reported as being about 500 ktonne (European Asphalt Pavement Association (EAPA) 2007).

4.2.2 Development Trials It is suspected that LEA-CO conducted some development trials of laboratory compactability/workability and performance trials of LEA-WMA during 2000–2003. However, the results have not been made public.


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4.2.3 Demonstration Trials A series of demonstration field trials of LEA1 was carried out in the Rhone-Alpes region in France in November 2003 (Romier et al. 2004). A total of 150 tonnes of LEA1 mix was manufactured and applied. Observations indicated that the LEA1 mixes were homogenous and reproducible and that the workability, at an application temperature between 60 °C and 80 °C, was similar to that of conventional HMA at high temperatures. It was also reported that the LEA1 mix had a surface appearance comparable to that of the HMA, including at joint locations.

4.2.4 Implementation/Validation Trials Olard et al. (2008) reported field trials of typical LEA1 mixes in Episy in 2005 (using 430T 0/14 Class-3 asphalt road base and Class-2 semi-granular asphalt with 35/50 binder), on Highway RD1 towards Saint-Etienne d'Issansac (using 0/10 type A asphalt) and on the Saint-Hilaire Freeway A26 (using very thin asphalt). To date, the performance at all sites has been satisfactory.

Laboratory mix design studies were also conducted on LEA1 mixes from these field trials, including compactability (gyratory compaction), moisture sensitivity (Duriez test), rutting resistance (wheel tracker), modulus (indirect tensile) and fatigue resistance (fatigue beam) and the same performance requirements as conventional HMA. The results obtained with mixes produced according to the LEA® process compared with HMA mixes were of the same order and judged to be satisfactory. Those laboratory mix design results are now appearing in the catalogue of licensed LEA® mixing stations.

4.3 Low Emission Asphalt (LEA2) 4.3.1 Background In 2006, whilst implementing the LEA1 technology in the USA, McConnaughay Technologies improved the chemical additives being added to the hot coarse aggregates (coated with hot binder, followed by the introduction of wet sand which created a foaming action). As a result, they changed the name to low emission asphalt (LEA2). The manufacturer claims that the chemical additives being added in the LEA2 process produce more stable WMA mixes at low compaction temperatures (60 °C). However, details of these chemical additives are not in the public domain.

4.3.2 Development Trials No development trials were reported by McConnaughay Technologies.

4.3.3 Demonstration Trials Harder (2007a) reported two demonstration trials of LEA2 conducted by McConnaughay Technologies in New York in 2006. The first trial involved the use of 300 tonnes of 9.5 mm mix, 25 mm thick, on a driveway of the company’s bitumen terminal. The initial compaction and the field performance after the first 20 000 passes of trucks were reported to be satisfactory.

The second demonstration trial involved the placement of 1000 tonnes of 9.5 mm mix and a control HMA section on Route 11 to a compacted depth of 37.5 mm. The sites were laid during heavy rainfall. A site inspection conducted about six months after construction showed that the HMA control section exhibited approximately seven times the amount of cracking as that of the LEA section. Based on this limited amount of production, the reduction in energy consumption was measured to be 47%.


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4.3.4 Implementation/Validation Trials USA

By 2007, McConnaughay Technologies had conducted 11 implementation trials involving the use of 34 000 tonnes of 9.5 mm mix on various routes in New York (Harder 2007b). Laboratory mix design studies conducted on both the LEA2 and the HMA were also reported. LEA and HMA samples (both unconditioned and conditioned (aged in an oven of 95 °C for two hours) were tested for compatibility (gyratory shear test), moisture sensitivity (Tensile Strength Retained (TSR) test) and modulus NCHRP simple performance test). The results were both mixes were of the same order and judged to be satisfactory.

New Zealand

Hayward and Pidwerbesky (2009) reported the results of trials of an LEA1 product (CoolPave), conducted in New Zealand. The results are discussed in Section 9.2.1.


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5 FIELD TRIALS OF FOAMING TECHNOLOGIES USING WATER-BASED MECHANICAL SYSTEMS

5.1 Double Barrel® Green 5.1.1 Background Double Barrel® Green (DBG) is a system developed by Astec Industries in 2007. In this process, approximately 0.5 kg of water per tonne of mix is introduced through nozzles, causing the hot binder to expand by about 18 times. The resultant production temperatures are typically 120-135 °C with the mix being placed at temperatures as low as 115 °C.

The system requires an Astec Double Barrel® drum asphalt plant and a multi-nozzle foaming device used to microscopically foam a standard grade binder with water. In order to implement the process on a Double Barrel® drum asphalt plant, the only plant modification necessary involves the installation of the foaming manifold over the existing binder injection system on the outer drum of the plant and the installation of corresponding binder and water feed lines into the manifold. An upgrade of the plant software control system is also required.

5.1.2 Development Trials The DBG foaming system is considered to be an improvement over previous foaming technologies in terms of cost reduction (i.e. low initial installation cost and no chemical additives) and low water additive. Astec Industries also claim that the use of a low water dosage added for the foaming action and high mixing temperatures (120–135 °C) does not negatively influence the moisture susceptibility of mixes compared to conventional HMA.

5.1.3 Demonstration Trials Middleton and Forfylow (2009) reported a demonstration trial of DBG using a 2007 Double Barrel® Drum Asphalt Plant (400 ton/hour) in Vancouver, British Columbia. Four WMA mixes were produced, including a virgin mix, a mix with 15% RAP, a mix with 15% RAP and 5% modified shingle mix (MSM), and a mix with 50% RAP. The laboratory testing of the HMA and WMA production samples included workability (gyratory compactor), recovered binder characteristics (Rolling Thin Film Oven), rutting susceptibility (Asphalt Pavement Analyser), stiffness (indirect tension) and moisture sensitivity (TSR). It was concluded that the DBG process produced mixes having similar binder and mix properties to HMA, satisfactory rutting resistance and adequate stiffness.

Kvasnak (2007) reported two demonstration trials of the Astec DBG technology with asphalt mixes having 30% and 50% RAP in Chattanooga, Tennessee. The trials were conducted on the Astec parking lot (30% RAP) and on North Terrace Rd (50% RAP) respectively. It was reported that all mixes were workable with no compaction issues. Laboratory TSR testing for moisture sensitivity was carried out on DBG-RAP and DBG-virgin samples collected during construction. The results showed that the TSR value for the DBG-virgin samples was greater than 0.9, whilst the values for the DBG 30% and 50% RAP mixes were 0.58 to 0.8 respectively. The results of Asphalt Pavement Analyser and Hamburg Wheel Tracking Device (HWTD) testing showed that the DBG-RAP mixes performed better than the virgin mixes. It was concluded that the Double Barrel® Green process did not negatively influence the moisture susceptibility of mixes. The use of RAP and MSM in conjunction with the DBG process did not significantly influence mix properties and performance based on laboratory testing.


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5.1.4 Implementation/Validation Trials Kvasnak (2007) also reported four field trials established to compare different WMA technologies in Nashville, Tennessee. Each trial involved the use of about 700–1150 tonnes of WMA. One trial section used the Astec DBG system whilst Evotherm® DAT, Advera® and Sasobit® were used in the other trials. Two control HMA sections (with PG 64-22) were also included for comparison purposes. All trials showed good workability with no compaction issues. Kvasnak reported that laboratory TSR testing conducted on samples collected during construction indicated that the mixes produced by the Astec DBG system passed the moisture susceptibility testing, whereas the other mixes (Evotherm® DAT, Advera® and Sasobit®) failed the moisture susceptibility test.

Barros (2009) reported a series of six field trials of WMA technologies involving the use of asphalt rubber mixes (RMA) which have been investigated by the California Department of Transportation (Caltrans) since 2008. One trial involved the use of rubber WMA mixes produced by the DBG process in 2008, while the other trials involve the use of rubber WMA mixes (produced with Evotherm®, Advera® and Sasobit®) in 2009. The rubber HMA mixes were also included in four trial sections for comparison with other WMA technologies. It was reported that, as the temperatures on the coastal highway in California during the summer are generally cool, WMA offered an excellent pavement alternative.

An update of the field trials was reported by Barros et al. (2011). Visual observations of open-graded asphalt (OGA) showed that the WMA mixes were performing equally as well as the conventional hotmix OGA. The performance of the rubber WMA OGA appeared to suggest a longer service life than the conventional rubber OGA with a subsequent recommendation to adopt WMA for all rubber OGA.

5.2 Ultrafoam GX® System 5.2.1 Background The Ultrafoam GX® system was developed by Gencor Industries, Inc. (USA). It involves the use of a special foaming generator (dubbed the Green Machine) that can be easily connected to an existing binder injection line leading to a drum mixer. The binder and water are mixed together in a proportionate and continuous fashion and small, evenly sized bubbles are generated, which result in consistent foaming at all production rates.

5.2.2 Development Trials No development trials have been reported by Gencor Industries. However, Gencor has contracted NCAT to conduct an intensive laboratory testing program, including moisture susceptibility (AASHTO T283, 2007), HWTD (AASHTO T324-04, 2004), dynamic modulus (AASHTO TP62-03, 2005), beam fatigue (AASHTO T321-07, 2007), and repeated simple shear and shear frequency sweep testing (AASHTO T320-10, 2010) to assess the laboratory performance of WMA products produced by Ultrafoam GX® and HMA.

The results of the laboratory testing are reported in Kvasnak et al. (2010). The moisture susceptibility test results generally suggested that the WMA products were more susceptible to moisture damage than the HMA, possibly due to the incomplete drying of the aggregate and softer binder at lower WMA production temperatures. Whilst the laboratory performance of the WMA mix (rutting, stiffness and fatigue) was inferior to that of the HMA mix, the performance of the WMA exceeded the minimum laboratory performance thresholds in most cases.


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Tensile strength testing on aged WMA samples (AASHTO R30-02, 2002) was also conducted to determine changes in tensile strength with aging. It was noted that the aged WMA samples (with different levels of aging) had higher resistance to moisture damage, that performance improved as the samples aged, and the performance of the aged WMA samples was similar to the HMA. These results suggested that any study of the moisture susceptibility of WMA and HMA mixes should consider binder aging effects.

However, as already stated, no studies have been reported relating the findings of the laboratory testing to observed field performance.

5.2.3 Demonstration Trials At the time of writing of this report, no demonstration trials of Ultrafoam GX® (laboratory or field) had been reported.

5.2.4 Implementation/Validation Trials Implementation of the Ultrafoam GX® system was included in the Caltrans study reported by Jones et al. (2011) as well as a comparative study of three WMA technologies in the City of Calgary reported by Forfylow and Reyes (2011).

The Caltrans study was undertaken in three phases. The first phase involved laboratory and accelerated load testing of three WAM technologies: Advera®, Evotherm® DAT®, and Sasobit®. The second phase extended the study to include moisture sensitivity. The third phase was a laboratory and accelerated loading test of seven different WMAs – Advera®, Astec Double-Barrel Green®, Cecabase®, Evotherm®DAT, Gencor Ultrafoam®, Rediset® WMX, and Sasobit® against two hotmix controls in a gap-graded rubberized asphalt mix. A new test track was built for the study. Paving emissions were also measured. Laboratory testing protocols were the same as those followed in Phase 1. The early rutting performance of Cecabase®, Evotherm®DAT and Gencor Ultrafoam® was found to be slightly superior to that of the control.

The City of Calgary conducted road trials using a residential surface mix design containing 15% RAP produced as conventional HMA and as WMA utilising three WMA technologies: two WMA water-foaming processes, ASTEC’s Double Barrel® Green and GENCOR’s Ultrafoam GX® processes, and a WMA chemical additive, GENCOR’s HyperTherm®. Laboratory evaluation was undertaken for moisture susceptibility (AASHTO T283-2007), rutting and fatigue (Asphalt Pavement Analyzer), low temperature cracking (Thermal Stress Restrained Specimen Test), tensile strength and resilient modulus (AASHTO TP31-96) workability (Superpave gyratory) and a rheological evaluation of recovered binders.

The laboratory evaluation showed that the WMA mixes had similar rutting and fatigue resistance, better low temperature behaviour, slightly lower mix stiffness at high temperature, higher laboratory workability, and similar stripping susceptibility, than the conventional HMA. In addition, the use of lower plant production temperatures was reflected in the rheology of the recovered binders. The testing of the recovered binders from the three WMA mixes indicated slightly lower stiffnesses at high and low temperatures than the recovered binder from the conventional mix. The road performance data showed that, after one year of service, the performance of the three WMA mixes was similar to the conventional HMA mix.


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5.3 Other Mechanical Injection Systems AQUABlack® WMA and Terex® WMA also involve the use of a mechanical system to inject water or steam into a binder stream.

AQUABlack® is described as a simple foaming device that is easy to install and operate on an existing asphalt plant. This device costs considerably less than many other plant foaming technologies, and the manufacturer claims that its efficient design will require minimal maintenance over time. At least three asphalt mix producers have purchased the AQUABlack® foaming device and installed it on at least six plants around Minnesota (Clyne, Johnson & Garrity 2011).

The Terex® WMA system was developed by the Terex® Roadbuilding Division of the Terex® Corporation in 1998. The system uses a single expansion chamber, which ensures a consistent binder/water mix at any production rate. The foamed asphalt is produced outside of the drum mixer and immediately injected into the mixing chamber to provide an even coating of the aggregate. The Terex® system can be easily adapted to most existing drum mix plants. Terex® claims mix production temperatures can be reduced by up to 32 °C without the use of additives.

No development, demonstration or implementation trials of these systems have been reported.


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6 FIELD TRIALS OF FOAMING TECHNOLOGIES USING WATER-BEARING ADDITIVES

6.1 Aspha-Min® 6.1.1 Background Aspha-Min® is a synthetic zeolite composed of alumino-silicates of alkali metals. It was developed by Eurovia Services GmbH (Germany). The Zeolite is produced in granular form. The product contains about 20% water of crystallisation, which is released as the temperature increases. Typically 0.3% zeolite by weight is slowly added to the mix shortly before, or at the same time as, the binder. The zeolite releases a very small amount of water at temperatures in the range of 100-200 °C, causing the binder to foam slowly while mixing with the aggregate. The foamed asphalt has greater workability and allows for improved compaction and coating of the aggregate particles. Typically, the mixing temperatures are approximately 120–135 °C with the mixture being placed as low as 115 °C.

6.1.2 Development Trials The manufacturers recommend that, by adding Zeolite at 0.25% by weight of a parent HMA mix, it is easier to place the mix at a lower temperature and offers benefits in base, binder and wearing courses. However, they do not report on the performance of the WMA mixes or the relative performance of Aspha-Min® compared with HMA.

Work to evaluate the workability and performance of Zeolite mixes compared with HMA has been conducted by Hurley and Prowell (2005a) and Wu et al. (2010). Hurley and Prowell (2005a) measured Marshall stability, rutting resistance (wheel-tracking), stiffness (indirect tensile) and fatigue (three point bending, trapezoidal specimens). They reported that no extended curing time had been observed and improvements in compaction levels and a higher degree of rutting resistance had been obtained with a reduced void content. Wu et al. (2010) measured fatigue cracking and wheel tracking properties of Aspha-Min® and HMA. They reported that the moisture sensitivity and low temperature properties of the Aspha-Min® were slightly inferior to those of the HMA.

6.1.3 Demonstration Trials Prowell and Hurley (2007) reported a trial conducted by the Virginia Department of Transportation in 2004 at the Hubbard equipment yard in Orlando, Florida. The trial involved the use of 0.3% Aspha-Min® Zeolite by weight added to a 12.5 mm Superpave mix (contained 20% RAP). A control HMA section was also included. The density of the WMA and HMA sections (using the Nuclear Density Gauge and density testing on field cores) was similar. Resistance to moisture damage (AASHTO T283, 2007) was also similar.

Davidson (2007) reported five demonstration field trials of Aspha-Min® conducted on various routes in Montréal, Canada, during 2005–2006, each involving up to 500 tonnes of asphalt. Five different binders were used in these trials: PG 64-28, PG 70-28, PG 64-34, PG 70-28 and PG 58-28. The trials also included control HMA sections. For the first three trials, a special batch plant, which had been modified with a rotary mixer into a continuous type plant, was used. For the other two trials, a hotmix drum plant was used. It was reported by the contractor that all the sites performed well and that there were no issues with temperature in terms of achieving the required compaction, even during the late season construction. Overall, the addition of the zeolite in the HMA (same mixing temperature) resulted in improved workability (easier to compact) compared to the same mix without zeolite.


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6.1.4 Implementation/Validation Trials As zeolite-WMA can be produced and placed using similar HMA construction procedures with only minor modifications to the asphalt plant, many road agencies are now considering implementing zeolite-WMA in applications where the construction of HMA is difficult (e.g. low construction temperatures).

D’Angelo et al. (2008) reported several validation trials of Aspha-Min® in France and Germany in 2007. They observed that the WMA sections performed as well as, or better than, the control HMA sections.

Various universities and transportation agencies in the USA have reported evaluation field trials to compare the performance of zeolite-WMA mixes against other types of WMA mixes and HMA.

For example, Brown et al. (2008) reported several validation trials of Aspha-Min® WMA, Advera®-WMA and other WMA technologies such as Evotherm® and Sasobit® in Orlando (Florida), Yellowstone National Park (Wyoming), Nashville (Tennessee) and Watsonsville (California). In most cases, the density of the WMA was very similar to, or higher than, the HMA. No evidence has been reported to date regarding any negative influences of the zeolite WMA technology on short-term performance compared with HMA. Accelerated pavement testing, using the HVS, was also conducted on a test track in Watsonsville (California). The results have yet to be published.

A field trial of Aspha-Min®, Sasobit® and Evotherm® in Kimbolton, Ohio, has been monitored since its construction in September 2006 (Hurley, Prowell & Kvasnak 2009a). According to this report, observations taken 18 months after construction showed that each WMA section was showing various stages of ravelling. It was suggested that this ravelling could possibly be a sign of moisture damage in the pavement or related to handwork conducted during the paving process.

Brief details of a trial conducted by Brisbane City Council are presented in Section 9.1.1.

6.2 Advera® 6.2.1 Background Advera® is a synthetic Zeolite produced by PQ Corporation (USA). It is similar to Aspha-Min® but has a finer gradation than Aspha-Min®, with 100% passing the 0.075 mm sieve. It is also claimed by the manufacturer that the mix is effective with all grades of asphalt, including polymer modified and rubber mixes.

6.2.2 Development Trials The manufacturer recommended that, by adding Zeolite at 0.25% by weight of a parent HMA mix, it is easier to place the mix at a lower temperature and offers benefits in base, binder and wearing courses. However, no performance data has been reported. PQ Corporation is working on a process to blend Advera® with the binder as it is being introduced into a plant instead of simply blowing it into the mixing chamber like a fibre. The blending process is also claimed to provide a more consistent WMA.

6.2.3 Demonstration Trials At the time of writing of this report, no demonstration trials of Advera® (laboratory or field) had been reported.


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6.2.4 Implementation/Validation Trials Various universities and transportation agencies in the USA have reported evaluation field trials comparing the performance of Advera®.

WMA mixes against other types of WMA mixes and HMA. A summary follows. (Note that the work conducted by Barros (2009) has already been reported in Section 5.1.4).

Kvasnak

Kvasnak (2007) reported an evaluation trial of Advera® (and Evotherm® DAT and Sasobit®) at a mountainous location in Silverthorne, Colorado. All trials showed good workability with no compaction issues.

Colorado Department of Transportation (CDOT)

The Colorado Department of Transportation (2009) reported the results of a field trial of WMA overlays of Highway I-70 (30 000 AADT), east of Eisenhower tunnel, Colorado. It included a control HMA section and three WMA sections (Advera® with 58-28 binder, Evotherm® 64-22 binder and Sasobit® with 64-22 binder). Each section was 1 mile (1.6 km) long with 1000 tonnes (1016 t) of WMA used. Construction was conducted at a high elevation and during cold winter temperatures. The air voids of the WMA cores were compared to the HMA cores, indicating a higher level of compaction of the WMA mixes. There has been no evidence to date of any negative influence of the zeolite-WMA technology in terms of both short-term and long-term performance compared to HMA. All sections performed well after the first year of trafficking. However, laboratory deformation testing (using the HWTD) performed on slabs compacted with a linear kneading compactor indicated that the performance of the Sasobit® WMA mix was superior to that of the HMA, whilst the Advera®-WMA and Evotherm®-WMA rutted at a higher rate than the HMA.

University of California Pavement Research Center

Jones et al. (2010 & 2011) reported an evaluation trial conducted by the University of California Pavement Research Center to compare the workability and performance of three WMA products (Advera®, Evotherm® and Sasobit®) and a control HMA. In this trial, the HVS, with wheel loads varying between 40 kN and 90 kN, was used to assess the rutting performance of the WMA and HMA at various pavement moisture conditions, viz. equilibrium moisture and pre-soaked with water for a period of 14 days prior to testing.

The results indicated that, at both the equilibrium and pre-soaked moisture conditions, there was no significant difference in rutting behaviour between the two HMA sections and the Advera® WMA. Top-down cracking was noted on all sections, with no significant difference in the crack patterns, crack length, or crack density. Cracks did not appear to penetrate below the top lift of asphalt on any of the sections.

Laboratory compaction testing conducted on the Advera® WMA and HMA mixes immediately after production indicated that the WMA mixes had lower specific gravities and higher air-void contents compared to the HMA control. However, these results were not representative of measurements after construction of the test track. Laboratory performance tests (shear and fatigue beam testing) indicated that the WMA technologies assessed did not influence rutting or fatigue cracking performance. Laboratory moisture sensitivity testing (using the HWTD and the TSR test) indicated that all the WMA mixes (including the control) were potentially susceptible to moisture damage. There was, however, no significant difference in the level of moisture sensitivity between the control mix and the mixes with additives.


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Montana Department of Transport

Perkin (2009) reported two field trials involving Advera® and Sasobit® at East Entrance Road, West of Cody, Yellowstone National Park and South of Gardiner, Montana. The sites have been monitored by the Montana Department of Transportation (MDT) since 2007. The first trial - 11.2 km long and involving the use of 28 000 tons of asphalt – consists of a control HMA mix, and two WMA mixes produced using Advera® and Sasobit®. The second trial has one section of HMA and one section of Advera® WMA. Perkin (2009) reported that the air voids of field WMA cores were lower than those of the HMA cores, indicating a higher degree of compaction of the WMA mixes. No evidence has been reported to date of any negative influences of the Advera® WMA technology on both the short-term and long-term performance compared to HMA. However, laboratory performance testing (using the HWTD) on slabs (compacted with a linear kneading compactor) indicated that the Advera® slab rutted at a faster rate and did not pass the MDT specification of < 13 mm of rutting. Whilst the Sasobit® slab passed the rutting specification, its performance was still inferior to that of the HMA slabs.


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7 FIELD TRIALS OF CHEMICAL ADDITIVE TECHNOLOGIES 7.1 Evotherm® 7.1.1 Background Evotherm®™ is a process developed by Asphalt Innovations, a MEADWESTVACO business, in the USA in 2003. In the original Evotherm® process called emulsion technology (Evotherm®-ET), a bitumen emulsion is produced using a package of chemical additives designed to enhance coating, adhesion, workability and moisture resistance. The emulsion is then mixed with hot aggregates (at a rate of 25 kg of emulsion per tonne); a mix temperature between 85 and 115 °C results. The majority of the water in the emulsion flashes off as steam when the emulsion is mixed with the aggregates. Evotherm® ET requires no plant modifications and simply replaces the binder in a conventional HMA design. The initial rolling temperature of Evotherm® ET-WMA is between 85 and 90 °C, which is much lower than the initial rolling temperature for HMA (between 135 and 140 °C).

In 2006, MeadWestvaco also developed a new Evotherm® process called Dispersed Asphalt Technology (DAT), in which a concentrated solution of Evotherm® additives (using the same chemical package diluted with a small amount of water) is injected into the line (5% w/w bitumen4) just before the mixing chamber to produce a resulting mix temperature between 115 and 120 °C. Evotherm® DAT reduces the water in the mix and eliminates the cost of processing and transporting the emulsion. It requires minor plant modification for injecting Evotherm® additives into the system. The initial rolling temperature of Evotherm® DAT-WMA is between 100 and 105 °C.

A new process called Evotherm® 3G (Third Generation) has also been developed in partnership with Paragon Technical Services and Mathy Technology & Engineering. This process is water-free and is suitable for introduction at the mix plant or bitumen terminal. The resulting mix temperature is between 135 and 140 °C. It is anticipated that Evotherm® 3G will replace previous Evotherm®-ET and Evotherm® DAT processes. The initial rolling temperature of Evotherm® 3G-WMA is between 115 and 120 °C.

7.1.2 Development Trials MeadWestvaco does not disclose the additive contents of the Evotherm® chemical package or any details of internal development trials showing the impacts of the chemical additives on workability and performance. Nevertheless, external laboratories (including universities, transportation agencies, and other research organisations in USA and elsewhere) have conducted studies comparing the workability and performance of Evotherm® mixes with equivalent HMA mixes.

Hurley and Prowell (2006) used two aggregate types (granite and limestone) and two binders (PG 64-22 and PG 76-22) when they compared the workability and performance of mixes manufactured with different Evotherm® emulsions and two control binders. They confirmed the improved compactability of Evotherm® mixes at temperatures as low as 88 °C. Test results produced using the Asphalt Pavement Analyzer also showed that the addition of Evotherm® additives did not negatively affect the resilient modulus and the rutting potential of an asphalt mix. There was no evidence of any difference in indirect tensile strength gain with time for the mixes containing Evotherm® additives compared to the control mixes. However, Hurley and Prowell (2006) reported that the rutting potential increased with decreasing mixing and compaction

4 weight/weight, e.g. for 5 kg of bitumen in 95 kg of solution, % bitumen = 5/(95+5) x 100 = 5% w/w.


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temperatures; this may be related to the decreased aging of the binder resulting from the lower mixing and compaction temperatures.

Liva and McBroom (2009) conducted HWTD testing on a HMA control mix and six different WMA technologies (Sasobit®, Evotherm® 3G, Evotherm® DAT, Rediset® WMX, Advera® WMA, and Aspha Min). They found that the HMA control, the Evotherm® DAT modified, the Evotherm® 3G and the Sasobit® modified samples all demonstrated good rut resistance and moisture induced damage resistance and did not strip. However, the other synthetic zeolite products (Aspha-Min® and Advera® WMA) and Rediset® WMX did not demonstrate favorable rut resistance and showed signs of stripping.

Hu, Wan and Ma (2010) conducted various laboratory performance tests on laboratory-compacted specimens (TSR, stability, low temperature bending strain, dynamic stability, drainage, Cantabro, HWTD rutting) and found that most tests showed similar test results between the HMA and WMA SMA10. However, the performance of the WMA SMA10 with Evotherm® added was superior to the HMA SMA-10 in terms of water sensitivity and reduced rutting.

Xiao, Amirkhanian and Shen (2010) conducted a laboratory experimental study to evaluate the moisture susceptibility of WMA mixes containing three WMA additives (Aspha-Min®, Sasobit®, and Evotherm®), a control HMA (binder grade PG 64-22), and two aggregate sources. Laboratory testing (viscosity, dynamic shear rheometer, beam bending rheometer, indirect tensile strength, TSR, and flow of WMA mixes) was performed on all the mixes. The results indicated that the addition of the WMA could lead to a slight decrease in viscosity and an increase in failure temperature. In addition, the moisture susceptibility results illustrated that the mixes containing WMA additives generally had slightly lower TSR values than the conventional HMA mixes.

7.1.3 Demonstration Trials Davidson (2005 and 2006) reported three demonstration trials of Evotherm® ET involving approximately 1700 tonnes of WMA and conducted in Canada in 2005. All three trials used bitumen grade PG 58-28. It was reported that there were no problems during the production of the WMA in batch plants in all three trials.

Davidson (2006) also reported another demonstration trial of Evotherm® ET conducted in 2006 involving the use of 1250 tonnes of base mix (PG 58-28) and surface mix, both containing 15% RAP. A control HMA section was also included. It was reported that there were no problems during the mixing process in the plant or with the handling of the Evotherm® emulsion and there did not seem to be any difference in compacting the HMA mix at 140 °C compared to compacting the Evotherm® mixes at 80 °C.

Production samples and field cores obtained from the Evotherm® ET trials were tested using the SHRP testing protocol for HMA mix design (residual binder content, moisture content in mix, bulk re-compacted density, maximum theoretical density, air voids, film thickness, Marshall stability, flow index, TSR, and penetration on the recovered binder). The results were also compared with the results of equivalent HMA mixes. There did not appear to be any differences between the Evotherm® mixes and conventional HMA. Davidson (2007) also reported various demonstration trials of Evotherm® DAT undertaken in Canada, the USA and France. It was reported that the DAT system was very easy to use and tied into the existing system.


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McKenzie (2006) reported that there were 10 to 12 Evotherm® projects around the world which demonstrated the successful application of the product with a wide range of aggregates, binders and production equipment. The mixes have been manufactured to both Superpave and Marshall designs. McKenzie also reported a project in the USA where WMA mixes were produced by Milestone Contractors LP using Evotherm®. Triangle Asphalt paved 660 tons of the mix on a country road in Indianapolis. The mix was produced at 149 °C at the plant and laid at 99 °C and emissions were significantly reduced. McKenzie also reported that the presence of water in the Evotherm® mix caused no issues in the baghouse.

Liping et al. (2010) reported trial sections of Evotherm® WMA technology which were constructed on the Zhubi Expressway in Henan, China, in September 2007. Prior to the trial, three mixes, namely SFA (Evotherm®), SA1 (Sasobit®) and SA2 (a WMA organic wax additive were evaluated in the laboratory). Based on laboratory results, SFA (Evotherm®) was selected for the field trial because fatigue performance at low temperatures is the major performance criterion.

Liping et al. (2010) reported that the control mix was an AC-13C (coarse aggregate, limestone as fine aggregates) whilst the target air voids content was 4%. The length of the trial was 543 metres. The WMA was placed in both the upper and lower layers: AC-13C in the upper layer with an optimum binder content 4.6% and AC-20C in the lower layer with an optimum binder content of 4.3%. Testing included skid resistance, permeability and density. After one year of trafficking (volume of trafficking level not reported) the performance of all sections was reported as being satisfactory. The authors concluded that successful installation of the SFA mix on the Zhubi Expressway indicated that WMA could achieve the same compaction and performance as HMA.

7.1.4 Implementation/Validation Trials It was reported by MeadWestvaco that, by 2008, more than 150 projects involving WMA had been successfully completed throughout the world (USA, Canada, Mexico, China and Europe), involving more than 400 000 tons of mix. The problem, however, is that no details of these trials are presented.

MeadWestvaco (2009a) reported two evaluation trials of Evotherm® 3G in Crow Wing County, Minnesota. Evotherm® 3G WMA was used as a means to reduce the occurrence of thermal cracking in dense-graded HMA mixes. The first trial was conducted in 2008 using approximately 2000 tonnes of material (PG 58-28 surface mix). After the first winter (2008–2009), the average number of cracks in the Evotherm® WMA pavement (PG 58-28 binder) was comparable to the average number exhibited by the HMA control pavement (PG 58-34 binder).

The second trial was conducted in 2009. It involved the use of over 20 000 tons of material (PG 58-28 of 12.5 mm NMAS Superpave). Based on previous experience, when the HMA mix contained 30% RAP, it yielded high binder modulus, leading to early low-temperature thermal cracking. Therefore, a HMA control mix containing 20% RAP and Evotherm® WMA (contained 30% RAP) were used in this trial as a means of reducing the occurrence of thermal cracks. They were placed in two lifts approximately 125–150 mm thick. It was reported that the early performance of both pavements was equal. Since the Evotherm® WMA was produced at approximately 40 °C lower mix temperature, less binder oxidation occurred, thus allowing the use of the higher RAP content. The use of a higher RAP content in the Evotherm® WMA (30% RAP) also provided another cost-savings benefit.


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MeadWestvaco (2009b) also reported a trial of Evotherm® 3G at the Ted Stevens Anchorage International Airport. A HMA control mix (with polymer-modified PG 64-34 binder) and Evotherm® 3G WMA (with PG 58-28 binder) were used in the re-cconstruction of the taxiways in September 2009. It was found that the Evotherm® WMA was more workable and easier to compact than the HMA at a low working temperature (below 11 °C). The density of the Evotherm® WMA was also higher than the HMA control mix. The modulus of the Evotherm® WMA pavement (based on deflection data collected using the FWD) exceeded the stiffness values of the HMA control mix.

Delfosse et al. (2011) reported cooperation between EUROVIA and MeadWestvaco in the development and promotion of WMA resulting in some 1 million tonnes of WMA being manufactured and applied since 2006. Specific reference is made to the placement of 14 000 tonnes of WMA basecourse on a new highway near Strasbourg in France. The 0/14 Grave Bitume mix design incorporated 10% RAP and 4.1% 35/50 pen bitumen binder. A laboratory study of the production asphalt showed similar performance between the WMA and HMA ‘control’ mix in terms of rutting resistance, stiffness modulus and fatigue. There was also very little difference in the rheological properties of the recovered binder. A slight reduction in moisture sensitivity performance of the WMA was still within specification limits.

Various universities, transportation agencies, and other research organisations in the USA have also conducted evaluation field trials to compare the performance of various WMA mixes (including that produced by the Evotherm® DAT process) and HMA. Some details follow.

Kvasnak

As discussed in Section 6.2.4, Kvasnak (2007) reported an evaluation trial of Advera® (and Evotherm® DAT and Sasobit®) at a mountainous location in Silverthorne, Colorado. All trials showed good workability with no compaction issues.

In another trial the performance of Evotherm® DAT and HMA was compared, involving approximately 2050 tons of material (asphalt mix with 15% RAP with a PG 67-22 binder) placed on the State Rd 79 in Birmingham, Alabama (Kvasnak & West 2009). All trials showed good workability with no compaction issues. Kvasnak (2007) also reported a series of four field trials comparing Evotherm® DAT and other WMA technologies (Astec DBG, Advera® and Sasobit®) and HMA in Nashville, Tennessee. Each of these trials used about 700–1150 tonnes WMA mix. Two control HMA sections (with PG 64-22) were also included in the trial. Whilst all trials showed good workability and no compaction issues, laboratory TSR testing indicated that only the WMA mix produced by the Astec DBG system passed the moisture susceptibility testing; the Evotherm® DAT-WMA and the other WMA mixes (Advera® and Sasobit®) failed the moisture susceptibility test.

Virginia Department of Transportation

Diefenderfer, McGhee and Donaldson (2007) reported a series of field trials of WMA and HMA conducted by the Virginia Department of Transportation over a two-year period. Evotherm® was used in one trial section, while the other trial sections used Sasobit® mixes. The control mix for the Evotherm® trial was manufactured using the same grade binder (PG 70-22) as the base binder of the Evotherm® emulsion. Both the control and Evotherm® mixes contained 20% RAP. Various laboratory tests for workability and performance were performed using samples of Evotherm® and control mixes collected at the plant. It was found that the air voids contents of the Evotherm® specimens were slightly higher than those of the control specimens, although the difference was not statistically significant. TSR values for the Evotherm® specimens were lower than those for


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the control specimens. Rut resistance testing showed relatively poorer results for the Evotherm® specimens compared to the control.

National Center for Asphalt Technology (NCAT)

Prowell, Hurley and Crews (2007) reported the results of field testing of Evotherm® mixes at the NCAT Pavement Test Track at Auburn University. Evotherm® is being tested on two test sites, each of which is about 70 m long. Laboratory testing (including volumetrics and Asphalt Pavement Analyzer and TSR testing) was conducted on samples prepared using materials collected in the field. The results did not show any negative influence of the Evotherm® on performance. Density testing performed on cores indicated that the addition of the WMA improved compaction, even at lower temperatures (i.e. up to 3.1% higher than HMA). Tensile strength ratio testing carried out on field specimens also indicated that field WMA and HMA samples produced similar TSR values.

The two sections of Evotherm® pavement have been trafficked since 2005. After being subjected to more than 10 million equivalent single axle loads (ESAL), the level of surface rutting is less than 3 mm on both sections.


The work conducted by the California Department of Transportation and the University of California Pavement Research Center to compare the workability and performance of three WMA products Advera®, Evotherm® and Sasobit®) and a control HMA is reported in Section 6.2.4 (Jones et al. 2010 and 2011).

7.2 HyperTherm® 7.2.1 Background HyperTherm®, a non-aqueous liquid warm mix additive, was developed by Lafarge in Canada. Lafarge does not disclose the additive contents of the HyperTherm® chemical package. The additive is either pre-dosed or added in-line into the hot binder.

It is claimed by the manufacturer that HyperTherm® improves workability in the mix by allowing it to be produced and placed at lower than conventional hotmix temperatures (i.e. produced at the plant at about 120 °C and compacted at between 75 °C and 90 °C) while the physical properties of the binder remain substantially unchanged. It is also claimed that HyperTherm® can also improve coating and adhesion properties.

7.2.2 Development Trials Prior to conducting demonstration trials, Lafarge conducted laboratory tests (viscosity and other performance graded (PG) asphalt binder properties using M320-10 specifications) on a control HMA PG 58-28 asphalt mix and a PG 58-28 modified with 0.2% HyperTherm® by weight of binder to demonstrate the effects of the warm mix additive on the binder (or impacts of the chemical additives on workability and performance of the mixes). It was found that the viscosity and other PG properties were only marginally affected by the addition of the HyperTherm®. It was inferred that HyperTherm® improved workability in the mix via a mechanism other than by reducing the viscosity of the binder. Both the PG 58-28 control and the PG 58-28 HyperTherm® met the required AASHTO M320-10 specifications for PG 58-28 binder.


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Testing of extracted and recovered binder samples was performed with Rolling Thin Film Oven (RTFO) residues and then aged in the Pressure Aging Vessel prior to being tested with the Bending Beam Rheometer. It was found that the recovered binder from both the HMA and WMA samples had different PG properties than had been obtained when the original binder had been aged in the RTFO oven. In terms of relative properties, the WMA had a high temperature performance grade that was about 1 °C lower than the HMA, while its low temperature performance grade was about 2 °C higher than the HMA.

In order to rule out the possibility that residual solvent was affecting the results obtained on the binders recovered from the mixes, a sample of PG 58-28 was tested after being recovered with the rotary evaporator. The results obtained on the recovered PG 58-28 were very close to that of the control. From these results it was inferred that residual solvent was not affecting the results obtained on the binders recovered from the mixes.

7.2.3 Demonstration Trials A demonstration trial was conducted in Canada in 2007 to examine whether a binder modified with HyperTherm® could be used to extend the paving season by facilitating paving in cold weather (Manolis et al. 2008). The trial was conducted during an overlay project in the City of Ottawa. The job involved the City of Ottawa’s new 4.75 mm mix intended for a traffic level of 3–10 million ESAL placed to a nominal thickness of 25 mm. PG 58-28 modified with HyperTherm® was used as the binder. The WMA was produced at about 120 °C at the plant and compacted at between 75 °C and 90 °C. This corresponded to reductions in mixing and compaction temperatures compared to conventional HMA using the same grade of bitumen.

7.2.4 Implementation/Validation Trials A trial involving HyperTherm® to extend the paving season in a cold weather application was conducted on Oxford Road 4 in the County of Oxford, Ontario (Manolis et al. 2008). The road was paved with PG 58-28 modified with HyperTherm® during the month of December, when the temperature was so cold that paving with the HMA PG 58-28 was not possible. By producing the mix at conventional HMA temperatures, compaction targets were achieved despite the low ambient air temperature and frozen granular grade. The improved workability imparted by the warm mix additive counteracted the cold weather conditions.

Compliance testing against the Ontario Provincial Standard Specification 1150 was performed in the laboratory on field samples taken from the job site. Some of the results for the 16.0 mm sieve were outside the limits of the specification. This was attributed to the difficulty in maintaining consistent material flow due to the freezing weather conditions. Field testing with a nuclear density gauge showed that compaction levels ranged between 92% and 97%.

A site visit was made in April 2008 after the road had been in service for four months over the winter. The pavement had held up well given the deficiencies in the granular base on which it was paved. Sections of the road had a rippled appearance. The two lanes that were paved have been providing access to this section of the road as well as to the truck entrance for the Toyota manufacturing facility in Oxford County since December 2007. The road was scheduled to be overlaid with a surface course during the 2008 season.


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A WMA paving project utilising HyperTherm® WMA technology was completed on Highway 10 in Ontario with a 2500 tonne HMA control section using Superpave 12.5 mm FC2 mixes composed of PG 64-28 binder (Lavarato et al. 2011). Plant-produced samples of HMA and WMA achieved acceptable rutting results, with the HMA achieving nominally better results when tested with the Asphalt Pavement Analyzer. Acceptable moisture sensitivity results were obtained for both the HMA and the WMA. Fatigue cracking properties measured with the Four Point Bending Beam Fatigue Test, and low temperature cracking properties tested with the Thermal Stress Restrained Specimen Test and Bending Beam Rheometer, were significantly improved in the WMA compared to the HMA. Samples were long-term oven aged to simulate field aging. The WMA had lower dynamic modulus values than the HMA which was in agreement with the trends identified during rutting and fatigue cracking tests.

7.3 Rediset® WMX 7.3.1 Background Rediset® WMX is a product developed by Akzo Nobel NV in the Netherlands. It is described as a chemical modifier formulated with a blend of surfactants and anti-stripping agents. Rediset® WMX comes in a pastille (i.e. bead) form that can be added to the binder or directly to the mixing unit at a rate of 1.5–2% by mass of binder. It is claimed that the use of the system results in mix production temperatures being reduced by 22–33 °C and paving temperatures reduced by 39–78 °C. The adhesive properties of Rediset® WMX may eliminate the need for separate treatments of liquid anti-strip or lime. It does not change the PG grade of the binder.

7.3.2 Development Trials Akzo Nobel NV has reported that mixes containing its product have rutting resistance (HWTD) comparable to mixes treated with hydrated lime.

7.3.3 Demonstration Trials At the time of writing of this report, no demonstration trials of Rediset® WMX (laboratory or field) had been reported.

7.3.4 Implementation/Validation Trials Needham (2009) reported an implementation field trial to compare the quality and performance characteristics of Rediset® WMX-WMA with conventional HMA. The Rediset® WMX was used in a surfacing mix and in combination with a plastomer modified binder (EVA) in two base mixes for overlays of two-lane carriageways of Durban’s Higginson Highway. An aggregate (consisting of 1% hydrated lime) and a RAP (with an average 4.4% and 5.6% binder content on the coarser and fine fractions, 5–6 pen, and softening points of approximately 84 °C) was used in all the mixes, including WMA and HMS control mixes, in both the base and surfacing. Follow-up work is discussed in Section 7.5.4.

The HMA used in the base was 40/50 penetration grade bitumen for 0–10% RAP and 80/100 pen for 40% RAP to achieve acceptable recovered binder properties. The WMA was 60/70 pen for 10% RAP and 80/100 pen for 40% RAP. For the surfacing, the HMA and WMA were 60/70 penetration grade bitumen for 10% RAP and 80/100 pen for 40% RAP mixes. Construction of the trial sections was conducted in October–December 2010. All the Rediset® WMX test sections (including the mixes containing 40% RAP) were successfully paved at approximately 35 °C below the average HMA manufacturing temperature, and about 25 °C below the average HMA compaction temperature.


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All WMA and HMA sections achieved field compaction in the range of 94–97%, which exceeded the target minimum limit of 92%. Laboratory performance tests (resilient modulus, dynamic creep, indirect tensile strength and rutting (MMLS)) were also performed on field samples. Some early laboratory performance test results (modulus and rutting) indicated that all the WMA mixes had a lower modulus and similar rutting than the control HMA mixes. However, the WMA mixes exceeded the target modulus and rutting limits. Early field performance data also indicated that all the WMA mixes have performed well against the fundamental requirement of performance being at least as equivalent as conventional HMA.

Zaumanis, Olesen and Haritonovs (2011) compared the laboratory performance of Rediset® WMX with Sasobit® and HMA in SMA. They found that compaction temperatures could be reduced by around 30 °C for both WMA technologies without compromising mechanical properties. At in-service temperatures, Sasobit® provided higher resistance to deformation and improved elasticity of bitumen. The use of the Rediset® WMX, however, had only a minor effect on the binder properties, suggesting that the additive changes the interaction between the bitumen and the aggregates rather than the bitumen itself.

7.4 CECABASE RT® 7.4.1 Background CECABASE RT® was developed, in the form of additives for warm coated materials, in the Arkema Rhône-Alpes Research Centre (CRRA) in 2003. It has been marketed, in the form of the CECABASE RT® product line, since 2006.

The additive contains surface active agents composed of at least 50% renewable raw materials. When mixed with asphalt, the application temperature on the road surface can be reduced by about 50 °C with no effect on material performance. Compared to the classical paving process, the use of these additives reduces energy consumption by 20–50%, depending on the process. CRRA also claim that dust emission is also considerably reduced.

CRRA maintains that the incorporation of CECA into the bitumen (2–4 kg per tonne of asphalt) enables the application temperature to be reduced to 120 °C, at the same time retaining the same properties as paving produced at 160–180 °C.

When designing the CECABASE RT® line, CECA paid special attention to avoiding reducing construction productivity. The products use the same technology as conventional paving. These additives are very easy to use since the process simply involves their addition to the bitumen.

7.4.2 Development Trials At the time of writing of this report, no development trials of CECABASE RT® had been reported.

7.4.3 Demonstration Trials González-León, Grampré and Barreto (2009) reported a field trial conducted in France in 2005 to compare the field performance of three WMA products using low dosage of chemical additives (0.3–0.5% CECABASE RT®, 0.5% CECA and 2.5% paraffin wax) with HMA. Performance grade 70–22 bitumen was used in both the control and WMA mixes. A total asphalt production of 300 tonnes (305 tonnes) was used to place a 50 mm thick base in four lanes (including one control and three WMA mixes). It was reported that the porosity of the WMA without additive was higher than the control, but that the porosity of the WMA with CECABASE RT® was only slightly higher than the control. Paraffin was found to be detrimental to porosity. The trial demonstrated that, at


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low percentages, the CECABASE RT® additive improved workability and rheological characteristics.

It was also reported by the manufacturer that, in 2006, about ten road paving preparation units had successfully used these products and that 80 000 tonnes of warm paving materials had been produced using these additives.

7.4.4 Implementation/Validation Trials Evaluation of CECABASE RT® is included in Phase 3 of the comprehensive Caltrans field and laboratory study already referred to in Section 5.2.4 (Jones et al. 2011). An initial assessment of rutting performance showed little difference in performance between all of the WMA technologies and the HMA control.

7.5 Sasobit® 7.5.1 Background Sasobit® is a product of Sasol Wax (formerly Schümann Sasol), South Africa. It is a Fischer-Tropsch paraffin wax, which is produced by treating hot coal with steam in the presence of a catalyst (Damm et al. 2002). Fischer-Tropsch waxes are long-chain aliphatic hydrocarbon waxes with a melting point of more than 98 °C. They may be used to modify a binder or added directly to the mix. They solidify in asphalt between 65 °C and 115 °C into regularly distributed, microscopic, stick-shaped particles and are completely soluble in the binder at temperatures higher than 116 °C. The liquid form of Sasobit® reduces the binder viscosity, thus enabling production temperatures to be reduced by ~10–30 °C.

The manufacturer recommends adding Sasobit® up to 3% by weight of the binder. Adding more than 4% is not recommended due to the possible impact on the binder's low temperature properties. The manufacturer also suggests blending Sasobit® into hot binder, rather than directly adding the material into the mixing chamber of an asphalt plant, due to concerns related to homogeneous distribution in the mix. Nevertheless, in many commercial applications in Europe, South Africa and Asia, Sasobit® has been added directly onto the aggregate as solid grains or molten liquid (Hurley & Prowell 2005a).

7.5.2 Development Trials Brits (2004) performed Marshall testing on mixes produced by adding Sasobit® directly onto the aggregate mix as solid prills or as molten liquid via a dosing meter. The test results indicated no difference in stability or flow compared to premixing with the binder.

Laboratory evaluations of mixes produced in commercial applications have also been carried out in various countries throughout the world.

USA: laboratory evaluation

Hurley and Prowell (2005a) carried out binder tests (using test protocol AASHTO MP1 2004) on various Sasobit®-modified binders and two control binders (PG 64-22 and PG 58-28). The results of dynamic shear rheometer testing before and after RTFO ageing indicated that the addition of Sasobit® reduced the ageing effect of heat and air on the binder. This confirmed that Sasobit®-modified binders produced a lower viscosity in the production temperature range (> 110 °C), while having similar (or slightly higher) viscosity at the in-service pavement temperature range (< 80 °C).


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A summary of the Superpave performance grade binder specification is presented in Appendix A. (Kennedy et al. 1994).

Compaction tests (using the Superpave gyratory compactor and the vibratory compactor) performed on mixes using the above binders, under different compaction temperatures (88–149 °C) also indicated that, under the same compaction temperatures, the addition of Sasobit® generally lowered the air voids in compacted samples, compared with the corresponding control mixes. Several laboratory performance tests were also conducted to assess mix stiffness, rutting potential and moisture sensitivity. It was found that the resilient moduli of the Sasobit® mixes were not significantly different to the mixes with the same performance grade (PG) binder. The addition of Sasobit® generally improved the rut resistance of the mixes. Reduced tensile strength and increased visual stripping were observed in both the control and Sasobit® mixes produced at 121 °C. The HWTD tests indicated good performance of Sasobit® mixes in terms of moisture sensitivity.

Thailand: laboratory evaluation

Kanitpong et al. (2008) reported the results of an evaluation of the fundamental properties of bitumen modified with Sasobit®. The properties evaluated included viscosity, rheological properties, rutting and fatigue resistance. The compactability of the mixes was also evaluated to determine whether they could reach the desired density at lower temperatures. It was found that the modification improved the workability and the fundamental properties in terms of improved rutting and fatigue resistance and higher complex shear modulus.

The measurement of the compactability showed that less energy was required to compact the modified mixes to the desired density, even at 20–40 °C below the compaction temperature. The fact that the modified mixes had a greater potential to resist permanent deformation suggested that they would also have a greater resistance to densification under traffic. No field trials were conducted, however.

The addition of the Sasobit® had no effect on the resistance of the asphalt mixes to moisture damage. However, it was suggested the reduction in the mixing and compaction temperatures could have a detrimental effect on the moisture sensitivity of the mixes.

China: laboratory evaluation

Liping et al. (2010) reported the results of a laboratory evaluation of three WMA technologies, and an HMA control mix, in terms of their possible application in road construction in China:

Evotherm® surfactant (SFA) a product developed by MeadWestvaco, USA

SA1 (Sasobit®), a synthetic zeolite made from fly ash and manufactured through a series of procedures which mainly involve hydro-thermal synthesis at a rate of 0.3% by mass of the mix (SA1)

SA2 (a WMA organic wax additive) produced by Shanghai Chenghong Road New Material Co. Ltd.

Liping et al. (2010) reported that:

The softening point and ductility of the SFA mix at 10 °C was lower but the penetration and viscosity values were similar to the HMA control. The softening points in the SA1 and SA2 mixes were significantly higher, but the penetration, ductility and viscosity were lower. (This latter finding is perhaps counter-intuitive.)


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There was up to a 1.5% difference in the air void content of Marshall and gyratory compaction testing. The air void contents of the mixes were notably different, with the HMA control having a significantly lower air-void content (4% from Marshall) than the WMA mixes (4.5–4.6%).

There was no significant difference in rut resistance (HWTD) between the control and WMA mixes and all exceeded HMA requirements.

There was no significant difference in the TSR of the control mix and the WMA mixes and all exceeded HMA requirements.

The SFA (Evotherm®) mix had the highest fatigue life compared with the other mixes at the same stress level at 20 °C.

It was concluded that the addition of the Sasobit® and Evotherm® slightly affected the resistance to moisture, the low temperature properties, fatigue cracking and wheel tracking properties compared with the conventional HMA; however, they still met HMA specification requirements. It was also concluded that the use of the WMA resulted in a decrease in the mixing and compaction temperatures of about 20 °C without affecting performance. As a result, the SFA (Evotherm®) mix was selected for the field trial.

7.5.3 Demonstration Trials The South African company, Sasol Wax, reported in 2005 that, since 1997, over 142 projects, involving over more than 2 200 000 m2 of pavement, had been constructed throughout the world (South Africa, Europe, the United States, Asia and Australasia) using Sasobit®. The projects included a wide range of aggregate types and mix types, including: dense-graded mixes, SMA and Gussaphalt. Sasobit® addition rates ranged from 0.8–4% by mass of binder.

In Europe, D’Angelo et al. (2008) reported a demonstration trial of Sasobit® WMA in Germany in 2007. They observed that the WMA sections had performed as well as, or better than, the control HMA sections.

7.5.4 Implementation/Validation Trials South Africa

As discussed in Section 7.3.4, South African Bitumen Association (SABITA 2011b) also reported an implementation field trial to compare the quality and performance characteristics of Sasobit® WMA with conventional HMA, where the Sasobit® was introduced into the existing HMA design for the overlays of two lanes of carriageway of Durban’s Higginson Highway, a distance of approximately 3.5 km. This report was a follow-up to that prepared by Needham (2009).

Several new WMA products were also tested in this trial, including SasolWax™ Exp 1655 (a WMA-high performance modifier designed for high RAP applications(Sasolwax 2005)), Rediset® WMX in a surfacing mix and in combination with a plastomer modified binder (EVA) in two base mixes, SasolWax Flex™ (a WMA-elastomer technology) in both the surfacing and base mixes, and NA Foamtec™ (a foamed bitumen technology developed locally by National Asphalt) in a surfacing mix and in combination with EVA modified binder in a base mix. An aggregate (consisting of 1% hydrated lime) and a RAP (with an average 4.4% and 5.6% binder content on the coarser and fine fractions, 5–6 pen, and R&B softening points of approximately 84 °C) was used in all the mixes, including WMA and HMA control mixes, for both the base and surfacing.


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The HMA used in the base was 40/50 penetration grade bitumen for 0–10% RAP and 80/100 pen for 40% RAP mixes to achieve acceptable recovered binder properties. The binder used in the WMA was 60/70 pen for 10% RAP and 80/100 pen for 40% RAP. The HMA and WMA used in the surfacing was 60/70 penetration grade bitumen for the 10% RAP and 80/100 pen for the 40% RAP. A total of approximately 15 000 tons (15 240 tonnes) of WMA and HMA was used to pave a 25–30 mm thick asphalt levelling course, an 80 mm thick asphalt base and a 50 mm thick asphalt surfacing.

Construction of the trial sections took place in October–December 2010. All the WMA test sections (including the mixes containing 40% RAP) were successfully paved at approximately 35 °C below the average control HMA manufacturing temperature, and about 25 °C below the average control HMA compaction temperature. All the WMA and HMA sections achieved field compaction in the range of 94–97%, which exceeded the target limit of 92% minimum.

Laboratory performance tests (resilient modulus, dynamic creep, indirect tensile strength, and MMLS rutting) were also performed on field samples. Some early laboratory performance test results (modulus and rutting) indicated that all WMA mixes produced lower modulus and similar rutting than the HMA mixes. However, they exceeded the target modulus and rutting limits. Early field performance data also indicated that all the WMA mixes in these trials have performed well in terms of the fundamental requirement of performance being at least as equivalent as conventional HMA.

Hurley et al.

Hurley, Prowell and Kvasnak (2009b) reported a field evaluation of the performance of Sasobit® in a cold weather environment, where the average temperature was below 4.4 °C for five months of the year. The Sasobit® was introduced into the existing HMA design with no modifications to the mix design for the widening of the north-bound lane of State Highway 95 (M95) in Iron Mountain, Michigan. The job mix formula used was a 9.5 mm nominal maximum aggregate size Superpave mix, designed with a compactive effort of 86 gyrations. A basalt aggregate source was used in the mix design. An unmodified PG 58-34 binder was used in the virgin mix. The WMA was used as an overlay for the top 38 mm (1.5 inches, compacted) of the surface course in the passing lane. The control section was placed in the newly-constructed adjacent travel lane.

The Sasobit® was added at a target rate of 1.5% by total weight of binder. Construction of the test sections took place in September 2006. The WMA test section was successfully placed at a compaction temperature 30 °C lower than the control HMA test section. Laboratory rutting susceptibility tests indicated that the rutting in the Sasobit® section was not statistically different from that in the control. Laboratory moisture susceptibility testing also indicated similar performance to the control. The measured tensile strengths were higher in the Sasobit® mix. The dynamic modulus of the Sasobit® was statistically the same as the control. However, the results of HWTD testing suggested that both the control and the Sasobit® test sections had the potential for both permanent deformation and moisture damage.

Field evaluation of the Sasobit® and control sections two years after construction indicated that neither permanent deformation nor moisture damage appeared to be an issue for either mix. Early performance indicated that the Sasobit® WMA could be successfully used in cold weather climates.


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As already discussed, Jones et al. (2010 and 2011) reported an evaluation field trial conducted by the California Department of Transportation and the University of California Pavement Research Center to compare workability and performance of three WMA products (produced by Advera®, Evotherm® and Sasobit®) and a control HMA.

In terms of the Sasobit®, the field results indicated that, at equilibrium moisture condition, the rutting resistance in the Sasobit® was higher than that in the HMA, given that the binder content of this mix was significantly lower. However, under the pre-soaked condition, there was a distinct difference in rutting performance of the Sasobit® compared to the HMA, in that the HMA control rutted at a notably faster rate than the Sasobit® section. Top-down cracking was noted on all sections, with no significant difference in the crack patterns, crack length, or crack density between the sections. Cracks did not appear to penetrate below the top lift of asphalt on any of the sections.

As already discussed, laboratory performance tests (shear and fatigue beam testing) indicated that the WMA technologies assessed would not influence rutting or fatigue cracking performance. Laboratory moisture sensitivity testing indicated that there was no significant difference in the level of moisture sensitivity between the HMA control and the mixes with additives.

The laboratory, accelerated load, and full-scale field testing conducted in this extensive study has provided no results to date to suggest that the Sasobit® technology cannot be used in California or elsewhere in the USA with similar climatic conditions.

7.6 Asphaltan B 7.6.1 Background Asphaltan B was developed by Romonta GmbH, Amsdorf, Germany. The manufacturer describes the product as a mixture of substances based on Montan wax constituents and higher molecular weight hydrocarbons. The manufacturer recommends adding Asphaltan B at 2 to 4% by weight of binder. It can be added to the asphalt mixing plant or directly by the binder producer; it can also be added to polymer-modified binders. The function and expected performance improvements (e.g. compactability, rut resistance) of Asphaltan B appeared to be similar to that of Sasobit®.

7.6.2 Development and Demonstration Trials At the time of writing of this report, no development or demonstration trials of Asphaltan B had been reported.

7.6.3 Implementation/Validation Trials D’Angelo et al. (2008) reported that Asphaltan B had been successfully trialled in Germany. Two trials were conducted on the highly-trafficked Autobahn between Cologne and Frankfurt, using two mixes incorporating 50/70 pen and Asphaltan B. Both field and laboratory tests for the Asphaltan B-WMA mixes showed similar or better performance than the conventional HMA mixes. No further details are available.

7.7 LEADCAP® LEADCAP®, produced by Kumho Petrochemical in Korea, is a relatively new product. It comprises a wax-based composition including crystal controller and adhesion promoter that adjusts the wax crystallisation and improve the low temperature properties of the binder.


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Lee et al. (2011) report a laboratory study of a reference HMA mixture and WMA mixtures modified by two different wax type LEADCAP® additives, KW3 (powder) and KW6 (chip). The performance characteristics investigated include rutting, fatigue cracking, and moisture susceptibility. Rutting performance was evaluated by the triaxial repeated load permanent deformation (TRLPD) test and the Asphalt Pavement Analyzer (APA) test. Both the TRLPD and APA test results show that the KW3 and KW6 mixtures exhibit more resistance to rutting than the HMA mixture. In addition, the HMA and KW6 mixtures exhibit approximately the same fatigue resistance, whereas the KW3 mixture’s fatigue performance is worse than that of the HMA and KW6 mixtures. However, the moisture susceptibility results indicate that the KW6 mixture is more susceptible to moisture damage than the HMA mixture. This increased moisture susceptibility in the KW6 mixture is currently being addressed by modifying the KW6 additive.

Oliviera et al. (2011) report a trial study of laboratory and field performance conducted in Portugal. Laboratory results showed improved rutting resistance and similar fatigue and stiffness modulus properties. Testing of field samples showed inferior performance to that of the laboratory results but that is attributed to high field air voids as a consequence of variation in grading of aggregates used in manufacture having a similar effect on both HMA and WMA mixes.

The report also refers to other trials in Korea, Japan, Italy, the USA and Thailand but no other details are available at this stage.


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8 FIELD TRIALS OF COMBINED BINDER MODIFIER-ORGANIC ADDITIVE TECHNOLOGIES

8.1 Shell Thiopave® 8.1.1 Background Thiopave® is a sulphur-based product that includes patented additive technologies developed by Shell. Sulphur has been used to improve asphalt performance since the 1970s. However, it is difficult to transport, store and use safely. The development of solid sulphur pellets in the late 1990s began to overcome problems with hot liquid sulphur5 (Strickland et al. 2008). In 2002, Shell purchased the original patent of the sulphur-extended asphalt product (known as ‘SEAM’ patented by Rock Binders, Inc.) and used SEAM in various road projects in Canada and the USA. In 2008, Shell incorporated the solid sulphur pellet technology known as Shell Thiopave®, which can be added together with a workability agent (organic wax) to the asphalt mix during the mixing process to lower the mixing temperature of the sulphur-modified mix so that it can be produced as WMA.

The Thiopave® modified sulphur pellets can be added to the mixing chamber at ambient temperature (in most batch and drum mix plants). They melt rapidly on contact with the heated mix (at a melting temperature of 116 °C) and are dispersed throughout the asphalt mix by aggregate shear during mixing (Deme & Kennedy 2004). They release the sulphur to combine chemically with the bitumen with the remainder (crystallising) acting as a structuring agent in the asphalt mix. It is noted that, if mixing occurs above 140 °C, there is a significant risk of hydrogen sulphide being emitted from the mix. The target mixing temperature for asphalt containing Shell Thiopave® (combined with a workability agent) is 130 °C (a reduction of 20–40 °C compared to conventional HMA). It is compacted in the same manner as conventional mixes at an initial temperature of > 110 °C. This process can also reduce odours and fumes during production and placement.

Shell recommends that Thiopave® (combined with a workability agent) can be used to reduce the amount of bitumen needed for road construction, by replacing a proportion of the bitumen in the asphalt mix by up to 25% by mass of the bitumen. Nevertheless, previous trials have been successfully conducted using 30–40% Thiopave® (Nicholls 2009). However, Shell does not recommend using Thiopave® when a plant foaming attachment is active or a warm mix additive containing water is used. Laboratory testing should also identify if there is a need for any type of anti-stripping additive. Shell also advises that Shell Thiopave® should not be used in mixes where a pre-blended PMB is present.

Asphalt mixes using Shell Thiopave® can be placed using conventional paving equipment. However, paving crews are advised to wear personal protection equipment as the amount of sulphur vapour can vary during production and paving, depending on the temperature and atmospheric conditions. Hydrogen sulphide emissions from the asphalt mix can also occur if the mix is heated to temperatures above 140 °C.

8.1.2 Development Trials The potential for sulphur to improve asphalt performance has long been recognised (Beatty et al. 1987). Recently, Shell reported that laboratory results have shown significant performance improvement when Shell Thiopave® was used with PMBs. Subsequently, Shell has sponsored a field trial at the NCAT Test Track to provide field performance data for the WMA-PMB mix (Powell & Taylor 2011).

5 US references use the term ‘sulfur’.


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8.1.3 Demonstration Trials Nicholls (2009) reviewed test and performance data from projects where SEAM/Shell Thiopave® had been used around the world. It was concluded that ‘the primary advantages of Shell Thiopave® modified asphalt are an increase of strength, stability and, possibly, durability’. However, it takes some time (generally weeks) for the sulphur to crystallise and improve asphalt performance. It was also noted that these modifications may ‘allow reduced pavement thicknesses, particularly at higher traffic designed pavements’. A reduction in pavement thickness would only be possible using a mechanistic-based pavement thickness design method that would allow the increased stiffness of the mix at high service temperatures to be accounted for. This would result in reduced pavement deflection and thus reduced pavement damage caused by heavy axle load applications during warm conditions or under slow-moving traffic.

8.1.4 Implementation/Validation Trials As discussed in the previous section, since the introduction of Shell Thiopave® into the USA, Shell has sponsored a series of pavement testing at the NCAT Test Track to address the need to: (i) document field performance of this product, and (ii) use field performance test results to perform mechanistic pavement structural designs for various pavement structures.

The composition of the Shell Thiopave® test sections at the NCAT test track is shown in Table 8.1. Section N5 was designed to demonstrate the performance of Shell Thiopave® as a ‘perpetual’ pavement, whilst the purpose of Section N6 was to compare the performance of Shell Thiopave® performance to various other material sections of the same thickness, including sections incorporating warm mix additives and PMB in the binder course. These two sections were constructed in July 2009 and traffic loading commenced in August 2009.

The other three sections (E9, W2 and W7) are thin wearing course mill and inlay sections constructed over an existing standard binder and base layer. Section E9 was designed to evaluate Shell Thiopave® against the standards of the WMA certification program which NCAT has developed. NCAT selected the granite aggregate from Lithia Springs, Georgia, because it is very prone to stripping. This therefore represents a severe test of the performance of all the WMA mixes. Sections W2 and W7 were designed to test Shell Thiopave® in conjunction with a polymer.

These three sections were constructed in May 2009 and were opened to accelerated traffic without any initial curing period to allow the sulphur to crystallise. All three sections were constructed on super-elevated curves, meaning that the mixes will be exposed to high lateral shear stresses in addition to the normal vertical axle loading stresses. This is a severe field performance test for a thin surface lift.

Timm et al. (2009) and Tran, Taylor and May (2010) performed laboratory performance evaluation studies (moisture susceptibility, mix stiffness, rutting and fatigue cracking) of sulphur-modified WMA mixes relative to the performance of a control HMA mixture prior to the field evaluation of the mixes at the NCAT Test Track. The performance of the sulphur-modified WMA mixes (e.g. 30% sulphur-modified WMA with a design air void content of 2%, and 40% sulphur-modified WMA with a design air void content of 3.5%) was superior to that of the control HMA mix, which was designed to have 4% design air voids.


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Table 8.1: Composition of Shell Thiopave® asphalt test sections at NCAT test track

Section Wearing course Binder course Basecourse Anti-strip (all layers)

N5 32 mm – 4% air void design (PG 76-22)

121 mm – 3.5% air void design

40% Shell Thiopave® mix (PG 67-22)

76 mm – 2% air void design, 30% Shell Thiopave® mix

(PG 67-22) ARMAZ LOF, 6500 liquid

N6 32 mm – 4% air void design (PG 76-22)

70 mm – 3.5% air void design

40% Shell Thiopave® mix (PG 67-22)

76 mm – 2% air void design 30% Shell Thiopave® mix

(PG 67-22) ARMAZ LOF, 6500 liquid

E9 38 mm – 3.5% air void

design, 30% Shell Thiopave® mix

(PG 67-22)

63 mm remaining of existing experimental surface mix

152 mm of upper base (PG 76-22)

228 mm lower base (PG 67-22)

Akzo Nobel Redicote E-6 liquid

W2

38 mm – 3.5% air void design, 30% Shell

Thiopave® mix + 0.75% polymer

(PG 67-22)





W7 38 mm – 2% air void design 40% Shell Thiopave® mix +

0.75% polymer (PG 67-22)





Powell and Taylor (2011) reported the following conclusions from the study comparing mix produced using Thiopave® WMA technology to a conventional HMA control mix:

No significant problems were encountered producing either mix; a rich spot near the end of the HMA section was an indication that the design gradation was subject to segregation during placement. High densities were measured in both experimental pavements.

Although slightly more rutting was observed in the WMA certification section, the rutting in both mixes was less than 6 mm. The opposite trend was observed in the laboratory.

The surface roughness increased more in the HMA control section that it did in the WMA certification section.

Change in surface macrotexture as a function of traffic was virtually identical for both mixes. This was indicative of no differences in durability, which was supported by inspection of the field cores.

The HMA control section exhibited minor longitudinal cracking after approximately 2.9 million ESALs. No cracking was observed in the WMA section.

Although brittleness and crack susceptibility testing created some concern over how the WMA certification mix would perform, the HMA control section was the only one that actually cracked.

Based on a comprehensive assessment of construction, laboratory performance and field performance, acceptance of Thiopave® as an alternative WMA technology in the manner in which it was used at the NCAT Pavement Test Track was recommended.


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9 FIELD TRIALS IN AUSTRALIA AND NEW ZEALAND At the commencement of the project, road agencies and industry were asked to submit details of any trials (development, demonstration, validation/implementation as defined in Section 3.2).

A small number of demonstration trials of WMA technologies have been established in Australia since 2000. Typical trials are the CECABASE and Aspha-Min® trials in Brisbane, Queensland, by Brisbane City Council in 2008, Sasobit® trials in the Gold Coast by the Department of Transport and Main Roads (TMR) in 2006 and Sasobit® trials in Sydney by the then Roads and Traffic Authority, (RTA)6 (Figueroa, Hennessy & Hiley 2007).

9.1 Australia 9.1.1 Brisbane City Council Brisbane City Council reported that two sections of WMA (one with Aspha-Min® and the other with CECABASE RT®) were laid at Park Avenue, Clayfield, Brisbane in 2008. This was an example of the use of a foaming technology using water-bearing additives (Section 6.1).

Each site was 100 m long and involved 100 tonnes of asphalt. The mix was Council Type 3 (DG18) with multigrade binder and CECABASE RT® and Aspha-Min® additives. A control section of conventional HMA was also constructed. Apparent viscosity testing was conducted on cores extracted in November 2008. The results showed that the binder was aged more by the HMA process than the WMA process. Various laboratory tests (resilient modulus 32 °C, 120 Gyratory cycles, Marshall, indirect tensile modulus) were performed on the WMA. The results of the resilient modulus testing suggested that there was little difference between the HMA and the WMA. It was concluded that the Aspha-Min® WMA technology could be successfully implemented with minor modifications to the asphalt plant.

9.1.2 Department of Transport and Main Roads (TMR) Queensland It was reported in a series of personal communications (including a PowerPoint presentation to the AAPA/TMR Strategic Alliance Reference Group in May 2010), that a demonstration trial of the Astec Double Barrel® Green (water-based foaming) WMA technology was being conducted as part of TMR’s $1.95B upgrade of the Ipswich Motorway between Dinmore and Goodna.

Four trial sites, each 200 m long, were constructed using various combinations of WMA and RAP (0% and 15%) and an HMA control section (50 mm polymer modified binder surfacing DG14HS and 270 mm Class 600 bitumen base DG 20HM). Technical issues addressed included:

compaction temperature and mix volumetrics

in situ compacted density

resilient modulus

rut resistance.

It was found that adequate compaction could be achieved with WMA produced at 140 °C using the Astec Double Barrel® Green technology. Unfortunately, however, some of the trial sections were affected by the Queensland floods in early 2011. These sites will be overlaid with another layer of dense-graded asphalt prior to the completion of the project in 2012. The current performance of the pavements has yet to be reported. 6 The Roads and Traffic Authority became Roads and Maritime Services (RMS) during the course of this project.


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TMR has also undertaken a number of demonstration trials using Sasobit® since 2006, including one at Hope Island Road. Both the WMA and HMA control sections exhibited similar performance.

TMR has made provision for the permissive use of WMA under its technical standard for dense-graded and open-graded asphalt (Department of Transport and Main Roads 2009). The mix design registration process requires the contractor to nominate all constituents (including additives such as WMA additives) as part of their mix design submission. Where an additive is proposed, and the influence of the additive on asphalt mix performance is not known to TMR, typically the contractor and TMR would undertake an evaluation of the mix properties and field performance as part of the registration process. For example, Sasobit® is now included in a significant number of registered mix designs. TMR will continue to collaborate with asphalt suppliers to trial other WMA technologies as opportunities arise under a permissive arrangement (i.e. as a competitive alternative to HMA).

9.1.3 Roads and Maritime Services (RMS) NSW Figueroa, Hennessy and Hiley (2007)

Figueroa, Hennessy and Hiley (2007) reported a deep patch trial using Sasobit® conducted in August 2006 at Woodville Road (between Oxford and Guildford Roads). The main objective of the trial was to lay four layers of asphalt, each 63 m long (two AC20 60 mm thick layers and two AC14 45 mm thick layers), in one shift without running the risk of rutting in the wearing surface. The total amount of asphalt laid was approximately 100 tonnes.

The Sasobit® was added via the RAP belt using a modified hopper at a rate of 2 kg of per minute, giving an end Sasobit® content of approximately 1.5% in Class 450 binder. The AC20 and AC14 asphalt mixes were manufactured and maintained at 130 °C and 140 °C respectively. The temperature of the mixes upon arrival at the site varied between 127 °C and 137 °C. Thermocouples were inserted into the various layers of asphalt by the RMS to measure temperature profiles. Cores were taken from each layer immediately before the next layer was paved.

It was found that:

compaction was achieved in all layers despite the very low temperatures on one of the levels

the manufacture of the asphalt was achieved at the right temperatures and delivered on site with no problems

there were no problems with the workability of the asphalt despite the low temperatures

the temperatures of the asphalt as-placed were kept to a minimum.

Current situation

Since the trial reported in Figueroa, Hennessy and Hiley (2007), warm mix additives have been used in many asphalt patching and overlay works on the RMS road network. It should be noted that these mixes were not produced as WMA; rather, they were produced at conventional asphalt mix temperature with the warm mix additives. Warm mix additives were used in certain situations because of the need to increase workability and when long haulage distances were involved, etc.


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The RMS has no preference for a particular WMA. Relevant clauses in their specifications are:

WMA additive – the proportion of additive is limited to:

— for wax, the maximum percentage by mass of binder must not exceed 2.0%

— for surfactants, nominate the maximum percentage by mass of binder

— for water (either directly added or added in the form of water containing crystals), the maximum percentage by mass of the total mix must not exceed 0.06%.

9.1.4 Department of Planning, Transport and Infrastructure (DPTI), South Australia A 500 m long WMA trial was undertaken by Boral Asphalt on Gallipoli Drive. The road was newly constructed and the pavement was not trafficked immediately upon completion. All the asphalt layers, including AC10, AC14 and AC20, were manufactured and placed at lower temperatures using the foaming technology method. The asphalt was manufactured at a batch plant using an Astec foaming module attached to the bitumen line. Numerous other projects have been constructed using Sasobit® to achieve the lower production and/or placement temperatures under a variety of traffic conditions.

In terms of DPTI specifications:

any additive to be used has to be approved by the superintendent

the design of mixes with an additive must obtain the target air voids as specified by DPTI

the placement temperature is lower than that required by AS2150.

DPTI assume that the performance of WMA is equivalent to that of HMA.

9.1.5 VicRoads Surfacing WMA trials Trial 1

This was the first detailed formal field trial of WMA technology in Victoria. Laboratory testing of the WMA mix had been undertaken some years earlier to demonstrate that the laboratory properties of HMA and WAM foam asphalt were comparable. Further details are as follows:

location of project – Western Freeway/Deer Park Bypass, Caroline Springs

date of placement – February 2009

type of WMA (no RAP) – WAM-foam® method

site allows for direct comparison of HMA and WMA

testing undertaken is similar to that outlined in the draft WMA protocol

additional field samples have been taken after two years of service

data is not currently available.


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Trial 2

General details are as follows:

location of project – Princess Hwy East, Mulgrave

date of placement – March 2009

type of WMA with 20% RAP – water foaming method


testing undertaken is similar to that outlined in the draft WMA protocol

additional field samples have been taken after two years of service

data is not currently available.

Deep strength WMA trials Trial 3

location of project – M80, Western Ring Rd

date of completion – June 2012

WMA used in all asphalt layers including open-graded asphalt surface


testing undertaken is similar to that outlined in the draft WMA protocol.

Trial 4

location of project – Nagambie Bypass, Nagambie

date of completion – December 2012

WMA used in all asphalt layers at the intersection and thin WMA layer used over a granular pavement


testing includes modulus, fatigue and field performance (roughness, rutting, pavement strength and skid resistance (SCRIM)).

In addition, between February 2008 and June 2011 Citywide, which uses the Shell WAM-foam® technology, placed 16 000 tonnes of WMA foam for various municipalities in the Melbourne metropolitan area, including the City of Melbourne.

9.1.6 Main Roads Western Australia (MRWA) There has been limited use of Sasobit® over the last seven or eight years. As well as the environmental issues, its engineering properties are being taken advantage of. The use of Sasobit® by MRWA is twofold:

Initially dosing at 1.5% (the standard rate for dense-graded asphalt) at hot temperatures to achieve better compaction outcomes for the wearing course when the mix is transported large distances (up to and exceeding 600 km) and then doubled handled from a road train to a small truck for paving. The double handling results in a significant loss in temperature. Anecdotal reports are that conforming levels of compaction can be achieved that were not previously achieved without Sasobit.


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Dosing Intermediate course mix for mill and fill works where 250 mm and more of asphalt is placed in one shift and then opened to traffic. This has successfully been achieved using PMB and Sasobit.

Industry has also used Sasobit® in open-graded asphalt during the construction of a full depth asphalt pavement during the winter for an alliance contract. MRWA were not involved in this contract. Local government use has been limited to date; however, some field trials are planned.

MRWA has published specifications for the use of Sasobit®-WMA as wearing and intermediate courses. Some field trials of full depth foamed WMA (including RAP) are planned for 2012. MRWA’s main concerns with the product are the security of supply of Sasobit®, and the use of Sasobit® in other than a batch plant. Moisture sensitivity in Sasobit®-WMA can be an issue if plant operators rush the drying of aggregates, especially in drum plants.

9.1.7 Northern Territory Department of Transport (DOT) Currently the NT DOT are not conducting any WMA projects or trials, but may in the future when more is learnt about the process and products. One company currently uses Sasobit® (generally 1.5–2%) in their HMA mixes to ensure they meet DCI voids requirements of 7% (larger window for compaction) and to ensure that good wheel tracking results are met. DCI have not conducted any studies but visual inspection definitely suggests ‘harder’ asphalt on the ground.

9.1.8 Department of Infrastructure, Energy and Resources (DIER) Tasmania Whilst it is possible that WMA is being used in applications in Tasmania, DIER is not aware of any applications or have any involvement.

9.1.9 Department of Territory and Municipal Services (TAMS) ACT There was some use of Sasobit® several winters ago on minor residential roads but without any reduction in mix temperature. Performance was similar to HMA. TAMS has not encouraged or allowed the use of these types of additives on more heavily-trafficked roads.

One company is currently commissioning a new asphalt plant which will allow the production of WMA by foaming the bitumen in the plant. TAMS has encouraged this innovation and amended its specification to accommodate this technology.

9.1.10 Industry In addition to the cooperative trials reported in the previous sub-sections, industry has conducted a large number of development and demonstration trials, particularly in Victoria and NSW. Details of these trials are, however, not available.

9.2 New Zealand 9.2.1 Hayward and Pidwerbesky Hayward and Pidwerbesky (2009) reported that, in 2005, Fulton Hogan began assessing warm mix and half-warm mix technologies available around the world, and after an international fact-finding tour, selected the low emissions asphalt (LEA1) process to implement in the company’s New Zealand asphalt plants. The product has been placed on arterial and minor roads and also on airport taxiways in New Zealand.


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The temperature differential compared to traditional HMA resulted in measured fuel reductions of up to 45%, making it a highly energy efficient asphalt. In addition to the reduction in fuel, Hayward and Pidwerbesky (2009) reported that the product had a range of other benefits compared to HMA including:

more than 50% reduction in production emissions and more than 90% reduction in smoking and fuming during application with minimal to no odour

the mix could be placed in colder temperatures and carted further

improved longitudinal joints and surface appearance

the potential to extend pavement life due to reduced thin film heating of the binder and oxidation during the manufacturing process.

Following laboratory development and early pilot trials, the following implementation sites were commissioned:

Buckley’s Road, Christchurch, December 2007 (Christchurch City Council)

Montreal Street, Christchurch, March/April 2008; (Christchurch City Council)

Christchurch International Airport Taxiway, February 2008 (CIAL).

The Montreal Street site was constructed in two sections: an AC14 mix manufactured using the conventional HMA process, and the same mix design but manufactured using the LEA process (called CoolPave with LEA in New Zealand).

Cores were taken in August 2008 (four months after construction), and subjected to laboratory wheel tracking testing. It was found that the AC14 HMA initially had a higher rate of rut development compared with the CoolPave, but after 10 000 passes the rut depths were similar. Performance to that time (2009) had been satisfactory.

It was reported that, to that time, Fulton Hogan had produced CoolPave in five of its 14 fixed plants, all of which were continuous drum plants. Typical production temperatures are 95 °C for plants with RAP rings (where a portion of the aggregate stream is added in a damp state through the RAP ring). Plants without RAP rings produce CoolPave at about 105 °C, although plants with baghouse extraction systems often need to be mixed at 115 °C to ensure that there is no moisture in the exhaust gases. Fuel savings of 44% were measured when producing at 95 °C compared to the traditional HMA produced at 165 °C at the same plant.

Christchurch International Airport (CIAL) has a rolling 20-year program which makes it possible to consider paving opportunities that take advantage of opportunities to trial innovations. One of the innovations submitted to CIAL for approval was a trial of CoolPave on the airfield taxiway. Fulton Hogan laid 141 tonnes (598 m2) to a depth of 110 mm on one taxiway in February 2008. Subsequent testing and inspections of the trial showed that the mix was as stable and as strong as the standard HMA used normally on the airfield.

As a result, a larger trial, involving an overlay of another taxiway commenced in February 2009. For this trial, 515 tonnes (2745 m2) was laid. At that stage (2009), the performance was consistent with the first trial. Handling the CoolPave was easier and much safer for the paving team than the standard HMA product with no blue smoke and much lower temperatures.

A smaller trial involving 38 tonnes of CoolPave with 30% RAP was also conducted on Taxiway F. The use of RAP reduces the amount of virgin binder required, resulting in less cost and less fuel being used. The results of this trial were being assessed at the time the paper was published.


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9.2.2 Ball Ball (2010) provided details of four WMA technologies, and typical values calculated for the energy needed to produce a tonne of mix. No field trials were reported. Published results for fuel and electricity consumption of the HMA process indicated that the energy expended in heating the aggregate and bitumen (approximately 277 MJ/tonne of mix) was about 44% of the total energy involved in production, transport, laying and rolling of asphalt. This placed an upper limit on the proportion of energy expended that can be saved by adopting a WMA manufacturing process.

As measured data were not available for all processes, it was necessary to use calculated figures. These indicated that many processes had the potential to give heating energy savings of the order of 20%; the surfactant and wax technologies may produce somewhat better savings than this, while the LEA could give around double this figure. The situation with the hot emulsion-based process was not clear, but it was likely that the energy savings at reduced temperatures were negated by the energy expended in manufacturing the emulsion.

It was also suggested that the lower manufacturing temperatures would result in reduced emissions of CO2 and other organic gases. A typical WMA process would, if universally adopted throughout New Zealand, result in an annual reduction of CO2 equivalent emissions of approximately 4700 tonnes. The low energy asphalt (LEA) process would roughly double this, but adoption of this process may not be financially justifiable for some asphalt producers, because of the costs associated with the necessary plant refurbishments.

It was concluded that, at that stage in the development of the WMA technologies none appeared to be especially suited to New Zealand conditions. The environmental advantages due to reduced fuel consumption would need to be balanced against the costs of the additives and modifying the plant and the varying maturity of the different technologies. Consequently no recommendation covering all cases could be made.


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10 ON-GOING STUDIES AND IMPLEMENTATION OF WMA PRACTICES

10.1 On-going Studies and Implementation of WMA Practices in USA As described in Section 3 to Section 9, there are now at least 21 registered WMA technologies in the USA compared to only three in 2005. Demonstration trials of WMA technologies are now being conducted in 45 States, compared to 15 States in 2007. At the same time, 41 State Departments of Transportation have developed their own permissive specifications that allow contractors to substitute WMA for HMA on state road projects.

10.1.1 Laboratory and Field Trials of WMA Technologies As discussed in Section 3 to Section 9, WMA mixes incorporating wax, chemical and mineral additives have been successfully produced in the laboratory. However, there is concern that some WMA technologies (such as foam-WAM) are difficult to re-create in the laboratory. Some laboratories in the USA have produced foamed asphalt mixes in the laboratory that mirror conditions in the field prior to large-scale production and construction.

Typical laboratory assessments of various WMA technologies (Aspha-Min®, Sasobit®, Evotherm® and Utrafoam GX®), and a comparison with HMA, have been successfully conducted using the AASHTO laboratory testing protocols for HMA at NCAT (Hurley & Prowell 2005a and b; Kvasnak et al. 2010). These laboratory studies have generally shown that the WMA can be more susceptible to moisture damage than the HMA, possibly due to the incomplete drying of the aggregate and the lower binder grade at lower WMA production temperatures. Whilst some cases of laboratory performance (e.g. rutting, stiffness) of a WMA mix were found to be inferior to that of the HMA mix, in most cases the performance of the WMA exceeded the minimum laboratory performance thresholds and at times was equal or superior to that of HMA. It was also noted that the WMA mixes had a higher resistance to moisture damage with aging (using test protocol AASHTO R30-02, 2002) and that the aged WMA had similar properties to an HMA. Consequently, laboratory testing of conditioned/aged WMA samples has been adopted for determining binder aging effects, particularly when comparing the laboratory performance of WMA and HMA.

As described in Section 3 to Section 9, a large amount of demonstration and validation trials of WMA technologies have been established in the USA, particularly for WMA technologies involving the use of chemical and organic additives that can be easily replicated in laboratory and easily incorporated in field construction with minor plant modification. They have been used in road trials involving overlays with high RAP content mixes and severe construction conditions (construction in cold/wet environments).

For the foam-WMA technology, it was noted that some binders foamed readily while others did not foam much at all. Subsequently, previous demonstration and validation trials of foam-WMA technologies have been limited to specific binders that are known to foam well. Most of the trials of WMA technologies conducted in the USA appeared to show improvements in quality and efficiency of construction (i.e. improved workability, improved compaction and more consistent field density). Studies have also indicated that the short-term field performance of WMA mixes has been comparable to HMA mixes. However, moisture susceptibility and rutting resistance testing conducted in the laboratory (obtained from field production) indicated that some WMA technologies have similar rutting properties to HMA but a higher moisture susceptibility than HMA. Subsequently, many demonstration and validation trials in the USA will be monitored over the longer term in order that concerns regarding moisture susceptibility, rut resistance and durability of WMA products can be more adequately addressed.


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There have also been several full-scale accelerated pavement trials to compare field performance of WMA with HMA. For example, heavy vehicles were used on the NCAT test track to test several sections, including Evotherm®, to validate laboratory characterisation methods for WMA mixes for design purposes (Prowell et al. 2007). NCAT has also established a national WMA Certification Program consisting of both field and laboratory performance evaluations to assist with the WMA evaluation and approval process (Section 10.1.2).

Caltrans and UCPRC have also used the HVS to traffic a dense-graded HMA control and three WMA technologies (Advera® WMA, Evotherm® and Sasobit®), to assess rutting, fatigue performance, and moisture sensitivity (Jones et al. 2008). A similar HVS testing program is planned for the Davis test track at UCPRC, including two rubberised gap graded (RHMA-G) control sections and seven WMA technologies (Advera® WMA, Double Barrel® Green, CECABASE RT®, Evotherm®, Ultrafoam GX®, Rediset® WMX, and Sasobit®) (Jones et al. 2010 and 2011). Those studies will also include laboratory testing of specimens removed from the test pavements, and the monitoring of pavements constructed with a range of different mixes on State highways (Jones et al. 2008; Jones et al. 2010).

It is also noted that the FHWA Office of Pavement Technology has activated a Mobile Asphalt Mixture Testing Laboratory (MAT) to advance WMA research and validation through material sampling and performance testing. The MAT has been on site at many of the WMA projects across the country.

10.1.2 National Studies of WMA Technologies NCHRP projects

Currently, there are several NCHRP on-going projects that are expected to impact on the future direction of the use of WMA in the USA. They include the following.

NCHRP Project 9-43 – Phase II (Mix Design Practices for Warm Mix Asphalt). The objectives of this project are to: (1) recommend modifications to the preliminary WMA mix design and analysis procedure under development, (2) develop a protocol for the laboratory evaluation of WMA performance, (3) develop guidelines for WMA production and construction, and (4) prepare an updated emissions measurement protocol. NCHRP Project is now complete with the publication of NCHRP Report No 691 (Bonaquist 2011a and b).

NCHRP 09-47A – Phase II (Properties and Performance of Warm Mix Asphalt Technologies. The objectives of this project are to: (1) develop relationships between the engineering properties of WMA binders and mixes and field performance, (2) determine relative measures of the performance between WMA and HMA pavements, (3) compare production and laydown practices and costs between WMA and HMA pavements (including necessary plant adjustments to optimise plant operations when producing WMA), and (4) provide relative emissions measurement of WMA technologies compared to conventional HMA technologies.

NCHRP 09-49 – Performance of WMA Technologies: Stage I – Moisture Susceptibility. The objectives of this research are to: (1) assess whether WMA technologies adversely affect the moisture susceptibility of flexible pavements, and (2) develop guidelines for identifying and limiting moisture susceptibility in WMA pavements.


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NCAT warm mix asphalt certification program

Based on the results of a national survey, the NCAT established a national WMA Certification Program at its Pavement Test Track in 2010 (National Center for Asphalt Technology 2010). It consists of both field and laboratory performance evaluations to assist States with the WMA evaluation and approval process.

As susceptibility to moisture damage ranks high on the list of States’ concerns with WMA technology evaluation, a Superpave mix design is being used for the Certification Program using an aggregate with a history of stripping. Following a rigorous laboratory design and verification process, surface mix will be produced and placed on the NCAT Pavement Test Track and on test sections supported by robust perpetual foundations to ensure that the observed distress is not the result of structural inadequacies. Trucks will be used to apply five million ESAL in one year.

Performance under traffic and over time (e.g. rutting, roughness, ravelling, cracking, etc.) will be monitored; laboratory tests will be conducted on plant-produced material to evaluate the mixes for moisture susceptibility, rutting potential, cracking resistance, stiffness, and bond strength in accordance with the priorities indicated by the States in the national survey. Testing will also be conducted on HMA control sections in order that laboratory and field performance can be compared. NCAT will certify a WMA technology if its overall results are at least as good as the control HMA. If the WMA technology does not perform as well as the HMA control, then NCAT will recommend modifications to improve the performance of the WMA technology.

The evaluation will span 18 months. The first three months will consist of the development of a mix design with the WMA technology, obtaining materials, and constructing test sections. During the next 12 months, the section will be trafficked and the laboratory testing will be conducted. The last three months of the project will consist of final pavement evaluations and the preparation of a final report. In addition to informal quarterly progress reports, an interim report will be submitted to the WMA technology provider within the first nine months of project initiation summarising the mix design program, test section construction, and the laboratory performance of the WMA versus the control HMA. The final report will include pavement performance information, laboratory test results, and comparisons of both the laboratory and field performance of the WMA versus the control HMA. Favourable comparisons will result in the issuing of an acknowledgment certificate and the addition of the WMA technology to a certified list that will be maintained on the NCAT website.

The WMA Certification Program has been carefully designed to provide States with an assurance that questionable technologies will not earn certification without the risk of demonstration projects on the open infrastructure. Improved competition from newly-approved WMA technologies can only serve to drive down the cost of pavement construction and maintenance using a mechanism that is leveraged by States’ support of the NCAT Pavement Test Track but funded by the private sector. Concurrently, it will provide WMA technology providers with an assurance of a fair evaluation without the risk of poor construction quality, which can result when a WMA technology is not a good match for the selected project or the contractor views the demonstration as more of an inconvenience than an opportunity. The national scope of the NCAT WMA Certification Program also means that technology providers no longer have to support a new demonstration project in every State market.


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10.1.3 Implementation of WMA Practice in the USA Given that there are still lingering questions that are focused primarily on the compatibility of WMA technologies with different binder types, and their long-term properties associated with moisture damage susceptibility, rut resistance and durability, different States in the USA have taken different approaches to the implementation of WMA technologies in terms of current HMA practices.

A growing number of State DOTs have adopted permissive specifications that allow contractors to substitute WMA for HMA. These agencies do not necessarily evaluate the WMA mixtures in the laboratory but, rather, they evaluate the contractor’s submitted HMA mixture at hot temperatures. This is carried out without introducing WMA additives or simulating any WMA process modifications such as foaming. The binder content is selected and rut resistance and moisture damage susceptibility evaluated at standard elevated temperatures without the WMA. The contractor is then allowed to switch on the water-injection system, introduce additives and lower plant temperatures to produce WMA for the job.

In terms of specific guidance, it is stated in AASHTO R 26-01 (2005) that ‘if any modification…is made at the HMA plant, the HMA producer shall be the supplier and must provide the certification’. This has led some binder suppliers being concerned about their ‘downstream liability’ with respect to certificates of compliance and modifications at the plant with WMA additives or foaming processes.

Florida DOT, for example, had placed 300 000+ tons of WMA on 26 projects by July 2010. Florida’s permissive specification allows WMA to be used at the contractor’s option after normal HMA mix design and evaluation. Florida DOT is monitoring the properties of the WMA mixes produced and placed on their projects; they expect to use a ‘data driven’ approach to making future decisions about the use of WMA in the State.

Texas DOT allowed more than 1 million tons of WMA to be placed in 2010. Current HMA practices adopted by the Texas DOT include: (i) laboratory evaluation of a traditional HMA mix during the mix design phase, (ii) routine evaluation of rutting and moisture susceptibility of all HMA mixes using the HWTD – a minimum of three times over the course of a project, and (iii) contractor’s requirement to produce a 50-ton trial batch, which is sampled and tested at the start of the project. These requirements allow the exact HMA mix to be produced during the project to be evaluated. After an evaluation of the mix properties and performance (HWTD), DOT approves the project to move on to full production. During full production, the HMA is sampled again and tested using the HWTD (at least once). By applying the identical procedures for HMA mixes to WMA mixes, Texas DOT can fully evaluate mixes prior to and during production.

New York State DOT (NYSDOT) is embarking on a large-scale WMA evaluation program involving 24 experimental projects over the next two years. Each project will include an HMA test section (minimum 1000 tons) to allow comparison with the WMA. Contractors will be allowed to select from a list of DOT-approved WMA technologies. Prior to production, both the HMA and WMA mixes must be tested for rut resistance and moisture sensitivity and the results submitted to NYSDOT. WMA test specimens must be made from plant-produced mix if the laboratory preparation process does not simulate the production process.

NYSDOT has recently developed a WMA evaluation protocol which has been adopted by the entire north-east region of the USA (approximately 12 states). This protocol will be discussed in a future report when recommendations are made regarding required amendments to the current draft protocol adopted in Australia.


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It is also noted that a National WMA Technical Working Group has been formed by NAPA and FHWA. Its mission is to evaluate and validate WMA technologies and to implement WMA policies, practices, and procedures to contribute to a high quality, cost-effective asphalt pavement system.

Parallel to the growth in the use of WMA is utilisation of reclaimed asphalt pavement (RAP) in road construction. Research conducted at the Pennsylvania Transportation Institute for Pennsylvania DOT has been used to develop guidelines for using high percentages of RAP in WMA (Solaimanian et al. 2011). The laboratory work was focused on three WMA technologies: water foaming, a chemical additive (Evotherm®), and an organic additive (Sasobit™®). This research indicated that it was possible to produce WMA with high RAP having sufficient moisture damage and rutting but that particular attention needed to be paid to those aspects in the mix design.

10.2 On-going Studies and Implementation Practices in Europe After a number of minor trials, a major trial of the Astec Double Barrel® Green WMA was placed in Sweden in 2010 and 2011 (Ulmgren, Lundberg & Lundqvist 2011). On-going field performance will be monitored by annual inspection over a period of five years.

WMA or rather ‘viscosity reduced mixes’ are being used in Germany (Damm 2011). Their share of the total market is relatively small (estimated at 5–8%) but steadily growing. Wax based modifiers are mainly used. The main trigger to the adoption of such products is enhanced deformation resistance and workability, especially in adverse weather conditions. Other technologies such as zeolites, chemical packs or foamed asphalt have so far not gained significant market share as they do not appear to offer adequate economic benefit.

10.3 On-going Studies and Implementation Practices in Asia 10.3.1 Korea: Development of WMA Production and Construction Methods National research into the performance of asphalt pavements in Korea commenced in April, 1999. However, at that time, research into asphalt pavements had a very low priority compared to other fields of civil engineering. However, the failure of several pavements, an increase in traffic volumes and the need to develop a low-carbon policy highlighted the need for an urgent review of the design, materials and construction technology associated with asphalt pavements (Park 2012).

Three major research projects are currently being conducted in Korea. One of these projects ‘development of materials/design and construction technology-sustainable and environmental pavement’ commenced in 2005. The main aim is to develop environmentally friendly road pavements, high-technology pavement construction and control technology. The budget for the project, being conducted over five years, is US$17.3M, of which the Government (Ministry of Land and Transportation (MLTA) and the Korea National Highway Corporation) is providing US$9.9m and private industry US$7.4m. The research is being led by the Korea Institute of Construction Technology (KICT); however, 13 private companies and 13 universities are also involved.

In terms of the WMA component of the program, the main objectives are to:

implement WMA into road technology in Korea following an evaluation of its properties

develop practical processes through field trials

develop production and placement processes of foamed WMA pavements

develop a standard specification for WMA pavements.


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Jeong et al. (2010) have recently reported the second part of the project, the aim of which was to evaluate the production and placement of WMA mixes developed during the first part of the project. In this study, validation sites were constructed and opened to traffic. The results have yet to be reported.

10.4 Implementation of WMA Practices in Australia The successful outcome of a large number of field trials of WMA technologies throughout the world suggests that WMA may eventually be considered as a standard specified option for all pavement classes once contractors and asset owners gain confidence with the long term performance of WMA. In the USA, the list of approved WMA technologies has been growing quite rapidly over the last three years based on laboratory performance testing, validation trials and observed field performance. However, most DOTs undertook initial trialling of WMA on low-trafficked roads before trialling the technology on roads subject to higher traffic volumes. It would be anticipated that many SRAs in Australia would adopt a similar approach.

It is anticipated that the validation study being conducted in Melbourne as part of this project will demonstrate that the performance of WMA is at least equivalent to that of HMA and that the use of WMA technologies will grow quite rapidly as a result. It is likely that specific WMA technologies will be driven by the asphalt contracting sector under a permissive specification arrangement.

One issue that may need to be addressed is the possible impact of the introduction of a carbon tax on the widespread use of WMA in Australia.

10.4.1 Proposed Further Studies to Implement WMA Practices in Australia The successful outcomes of a large number of field trials of WMA technologies throughout the world suggest that WMA should be considered as a standard specified option for all pavement classes. In the USA, the list of approved WMA technologies has been growing quite rapidly over the last three years based on laboratory performance testing and supported by validation trials. However, not all US States work with ‘approved lists’, i.e. some simply approve the contractor to use the WMA technology.

There are several NCHRP projects (e.g. NCHRP Project 9-47 and NCHRP Project 9-49) that are on-going and expected to impact the future direction of WMA use in the USA. It is recommended that current NCHRP projects be monitored and their outputs examined in terms of any possible application to practice in Australia. Emphasis should be placed on projects concerned with the relationship between long-term field performance and moisture susceptibility.

10.4.2 Revisions to WMA Protocol As already discussed, one of the major tasks being undertaken during this project is the conduct of a validation trial of a range of WMA and HMA pavements in order that their performance can be compared, including an extensive laboratory testing program.

The need for any revisions to the draft WMA Evaluation Protocol will be discussed in the reports on the field trial and the associated laboratory testing. However, in terms of the conduct of field trials, following this review it appears that little or no revision is needed to the current draft Protocol.

As discussed in Section 3.2, three stages of field trials of various WMA technologies have been reported in the literature: development trial, demonstration trial, and validation/implementation trial. The revised Protocol will recommend what laboratory testing should be conducted depending on the complexity, and aims, of a particular field trial.


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11 CONCLUSIONS This report presents a review of field trials of WMA technologies conducted in various countries in the world, with the emphasis on performance differences between WMA and conventional HMA and the identification of field performance data that could be used to complement the Austroads WMA evaluation field trials for Australian road conditions.

Commercially-available WMA technologies were identified and grouped into six main categories:

— sequential aggregate coating and binder foaming techniques

— binder foaming using water-based mechanical systems

— binder foaming using water-bearing additives

— chemical additives

— organic additives

— combined chemical-organic additives.

They use different additive contents (which may affect the WMA mechanical properties), different aggregate drying temperatures (which may affect bitumen-aggregate bonding and moisture susceptibility), different maximum bitumen temperatures (which may affect long-term asphalt durability and performance) and different requirements in terms of plant modifications (which may affect cost, production efficiency and product consistency).

The review identified three types of field trials of a WMA technology: development, demonstration and validation/implementation. The scope, investigative method, verification criteria, etc. for each trial will depend on the technologies developed (i.e. additives/processes used to manufacture the mix and plant modifications required for these technologies), the asphalt producer’s marketing strategy and the road agency’s implementation strategy.

At the time of completing this report (May 2012), more than 160 documents had been identified in a literature search of WMA technologies reporting field trials of some form or another in the USA, Canada, Europe, Asia, South Africa, New Zealand and Australia. However, of these, only about 30% of the documents sourced provided sufficient information to allow a meaningful review to be conducted. Many of the documents sourced presented details of what were clearly ‘development’ trials, where there was either no control HMA section involved and/or a lack of data relating to mix type, pavement structure, climate, applied traffic, performance data, etc.

A large number of demonstration or validation trials of WMA technologies have been established in the USA to demonstrate the benefits of WMA technology compared to HMA, and to improve the quality and efficiency of construction (i.e. improved workability, improved compaction and more consistent field density). The major application has been overlays using high RAP content mixes and severe construction conditions (e.g. construction in cold/wet environments). There have also been further developments and improvements in the WMA technologies using water (e.g. foam technologies using water injection nozzles) and emulsion to reduce the amount of water added to the system in order to address the concern of moisture susceptibility issues associated with the use of the water-based WMA products.

There are now 23 registered WMA technologies in the USA (as compared to only three in 2005) and 45 States are conducting demonstration trials of WMA technologies (compared to 15 States in 2007).


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It also appears that WMA technologies associated with water-bearing, chemical and organic additives have received more consideration compared to WMA technologies using water-based mechanical systems.

These trials have demonstrated that most WMA technologies associated with chemical and organic additives can successfully be implemented with minor modifications to the asphalt plant and, in the case of Sasobit®, successful paving could still occur at low temperatures.

Some of the trials also address various concerns regarding the use of WMA, including incomplete drying of the aggregate (especially with absorptive limestones), the potential for increased moisture susceptibility when utilising WMA processes that involve the use of water, the effects of chemical additives on the long term performance of the binder, the ability of WMA to provide enough radiant energy to heat the reclaimed asphalt component in mixes containing RAP, and the general lack of information regarding the long term performance of new asphalt mix designs (e.g. with high RAP content or rubber asphalt).

Several asphalt producers and road agencies have collaboratively conducted accelerated loading studies of the comparative performance of WMA and HMA technologies under accelerated heavy loading. Examples include the work at the National Center for Asphalt Technology (NCAT) in Auburn, Alabama, and the work at the University of California Pavement Research Center (UCPRC) using the Heavy Vehicle Simulator (HVS). These trials have involved the production of the mixes, the construction of test pavements, and the monitoring of field performance, including detailed (within-pavement) response-to-load data. Extensive laboratory studies of both field and laboratory samples were also carried out in order that the relative performance of WMA with HMA could be compared with recommendations made regarding the implementation of WMA into current HMA mix design procedures.

In view of this, there is no immediate need for an accelerated pavement test in Australia; the work being conducted at NCAT and UCPRC has suggested that the performance of WMA pavements is at least equivalent to that of HMA. It is noted, however, that UCPRC is planning a follow-up test program of rubberised gap graded control sections and seven WMA technologies (Advera® WMA, Double Barrel® Green, CECABASE RT®, Evotherm®, Ultrafoam GX®, Rediset® WMX, and Sasobit®). Those studies will also include laboratory testing of specimens removed from the test pavements, and the monitoring of pavements constructed with a range of different mixes on State highways.

Despite the successful outcomes of the large number of field trials in the USA, there is still some concern regarding long-term performance (e.g. moisture susceptibility, rut resistance and durability) associated with lowering WMA production temperatures (including higher moisture sensitivity due to aggregates that are not adequately dried) and altering of the binder performance grade (when chemical and organic additives are used to produce WMA mixes). Future laboratory studies, if deemed necessary, should focus on moisture susceptibility, rut resistance and durability.

The amount of published material relating to demonstration or validation trials in Australia is extremely limited. The only two SRAs that appear to have been involved in WMA trials, in terms of published outputs, are TMR and RMS, NSW, although other SRAs such as VicRoads are cooperating in trials being conducted by industry. Similarly, whilst it is clear that industry has established a large number of trials, presumably mainly for local government applications, details of these trials are often sketchy and little or no material has been published.

Despite the lack of published information, however, the use of some WMA technologies has already been accepted by some Australian road agencies.


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Valuation protocols of WMA technologies involving the use of field trials have been established in the USA to maximise the benefits of validation trials; for example, a Material Test Framework for WMA Trials has been adopted by the US National Asphalt Pavement Association (NAPA) and the FHWA (Prowell, Hurley & Frank 2012). An emissions testing framework and draft WMA construction specification has also been uploaded onto this site. NYSDOT has also recently developed a WMA evaluation protocol which has been adopted by the entire north-east region of the USA (approximately 12 states).

The FHWA and NAPA are currently updating the first three documents following consensus being recently agreed regarding test procedures, evaluation protocols and test section requirements. The emissions testing framework updates are based on the recently completed emissions and fuel measurement work conducted as part of the NCHRP Project 9-47A. The recommended construction specification updates are based on the recently-completed WMA mix design work conducted as part of NCHRP Project 9-43.

In terms of the draft WMA Evaluation Protocol, following the review of other field trials it appears that no revisions are needed to the current draft protocol in terms of the conduct of field/validation trials. However, it is clear that the current provisions for the laboratory testing program in the draft protocol are too demanding, if for no other reason that it is impossible to conduct the amount of testing demanded in the draft protocol in the time available. The revised protocol will need to address what laboratory testing should be conducted depending on the complexity, and aims, of a particular field trial.

One issue that may need to be addressed is the possible impact of the introduction of a carbon tax on the widespread use of WMA in Australia.


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Harder, GA 2007a, LEA half warm mix paving report: 2007 projects for NYSDOT, McConnaughay Technologies, Cortland, NY, USA, viewed 25 May 2011, <http://www.mcconnaughay.com/admin/uploads/NYSDOT2007FinalReport.pdf>.

Harder, GA 2007b, Low energy asphalt: a cooler mix asphalt, Warm Mix Asphalt Technical Working Group (WMA TWG), Maryland & McConnaughay Technologies, Cortland, NY, USA, 27 ppt. slides, viewed 25 May 2011, <http://www.warmmixasphalt.com/submissions/52_20080101_Greg%20Harder%20-%20LEA.pdf>.

Hayward, BJ & Pidwerbesky, B 2009, ‘CoolPave with LEA® : low energy asphalt, the future of asphalt paving’, NZTA & NZIHT annual conference, 10th, 2009, Rotorua, New Zealand, New Zealand Transit Authority, Wellington, NZ.

Hu, Z, Wan, L & Ma, S 2010, ‘The technology of warm mix asphalt for use in the pavement structure of undersea tunnel, International conference on asphalt pavements, 11th, 2010, Nagoya, Japan, International Society of Asphalt Pavements (ISAP), White Bear Lake, MN, USA, 10 pp.

Hurley, GC & Prowell, BD 2005a, Evaluation of Sasobit for use in warm mix asphalt, report no. 05/06, National Center for Asphalt Technology (NCAT), Auburn University, Auburn, AL, USA.

Hurley, GC & Prowell, BD 2005b, Evaluation of Aspha-Min zeolite for use in warm mix asphalt, report no. 05-04, National Center for Asphalt Technology (NCAT), Auburn University, Auburn, AL, USA.

Hurley, GC & Prowell, BD 2006, Evaluation of Evotherm for use in warm mix asphalt, report no. 06-02, National Center for Asphalt Technology (NCAT), Auburn University, Auburn, AL, USA.

Hurley, GC, Prowell, BD & Kvasnak, A 2009a, Michigan field trial of warm mix asphalt technologies (Sasobit): construction summary, report no. 09-10, National Center for Asphalt Technology (NCAT), Auburn University, Auburn, AL, USA.

Hurley, GC, Prowell, BD & Kvasnak, AN 2009b, Ohio field trial of warm mix asphalt technologies: construction summary, report no. 09-04, National Center for Asphalt Technology (NCAT), Auburn University, Auburn, AL, USA.

Jenny, R 2009, ‘CO2 reduction on asphalt mixing plants potential and practical solutions’, AAPA international flexible pavements conference, 13th, 2009, Surfers Paradise, Queensland, Hallmark Conference and Events, Brighton, Vic, 21 pp.

Jeong, K, Kim, Y-J, Kim, Y-M, Yang, S-L & Kim, K-H 2010, Development of warm-mix asphalt production and construction technology for practice, report KICT 2010-160, (in Korean), Korea Institute of Construction Technology (KICT), Ilsan-Gu, Goyang-Si, Gyeonggi-Do, Korea.

Johnston, A, Yeung K, Bird, J & Forfylow, B 2007, ‘Initial Canadian experience with warm mix asphalt in Calgary, Alberta’, Asphalt Review, vol. 26, no. 2, pp. 45-9.

Jones D, Wu R & Barros C 2010, ‘Interim results from the California warm-mix asphalt study’, ARRB conference, 24th, 2010, Melbourne, Victoria, ARRB Group, Vermont South, Vic, 19 pp.

Jones, D, Wu, R, Tsai, B-W, Barros, CB & Peterson, PD 2011, ‘Key results from a comprehensive accelerated loading, laboratory, and field testing study on warm-mix asphalt in California’, International conference on warm-mix asphalt, 2nd, 2011,St. Louis, MO, USA.


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Jones, D, Wu, R, Tsai, B-W, Lu, Q & Harvey, JT 2008, Warm-mix asphalt study: test track construction and first-level analysis of phase 1 HVS and laboratory testing, report UCPRC-RR-2008-11, University of California Pavement Research Center, Richmond, CA, USA.

Kanitpong, K, Nam, K, Martono, W & Bahia, H 2008, ‘Evaluation of warm-mix asphalt additive’, Proceedings Institution of Civil Engineers-Construction Materials, vol. 161, no. CM1, pp. 1-8.

Kennedy, TW, Huber, GA, Harrigan, ET, Cominsky, RJ, Hughes, CS, von Quintus, H & Moulthrop, JS 1994, Superior performing asphalt pavements (Superpave): the product of the SHRP asphalt research program, SHRP-A-410, Strategic Highway Research Program, Washington, DC, USA.

Koenders, BG, Stoker, DA, Robertus, C, Larsen, O & Johansen, J 2002, ‘WAM-Foam, asphalt production at lower operating temperatures’, International Society for Asphalt Pavements conference, 9th, 2002, Copenhagen, Denmark, Danish Road Directorate, Copenhagen, Denmark, 12 pp.

Kvasnak, A 2007, NCAT WMA research, National Center for Asphalt Technology (NCAT), Auburn University, Auburn, AL, USA, 22 ppt. slides.

Kvasnak A, Taylor A, Signore JM & Bukhari, SA 2010, Evaluation of Gencor green machine Ultrafoam GX: final report, report 10-03, National Center for Asphalt Technology (NCAT), Auburn University, Auburn, AL, USA.

Kvasnak, A & West, R 2009, ‘Case study of warm mix asphalt moisture susceptibility in Birmingham, Alabama’, paper no. 09-3703, Annual meeting of the Transportation Research Board, 88th, Washington DC, TRB, Washington DC, USA, 13 pp.

Larsen, OR, Moen, Ø, Robertus, C & Koenders, BG 2004, ‘Warm foam asphalt production at lower operating temperatures as an environmental friendly alternative to HMA’, Eurasphalt & Eurobitume congress, 3rd, 2004, Vienna, Austria, Congress Secretariat, Brussels, Belgium, pp. 641-50.

Lavarato, S, Manolis, S, Pahalan, A & Reid, R 2011, ‘Asphalt mix performance testing for warm mix asphalt field project on Ministry of Transportation Ontario Highway’, International conference on warm-mix asphalt, 2nd, 2011,St. Louis, MO, USA.

Lee, J, Kim, YR, Lee, J-J, Kwan, S-A, & Yang, S-C 2011, ‘Comprehensive laboratory performance evaluation of WMA with LEADCAP additives’, International conference on warm-mix asphalt, 2nd, 2011,St. Louis, MO, USA.

Liping, L, Xiaofei, G, Zhen, Z, Feifei, X, Guoqiang, C & Lijun, S 2010, ‘Evaluation of three warm mix asphalt technologies’, International conference on asphalt pavements, 11th, Nagoya, Japan, International Society of Asphalt Pavements (ISAP), White Bear Lake, MN, USA, 10 pp.

Liva, GW & McBroom, DG 2009, ‘Warm mix asphalt’, internal research report, Montana Department of Transportation, Helena, MT, USA.

Mallick, RB, Bergendahl, J & Pakula, M 2009, ‘A laboratory study on CO2 emission reductions through the use of warm mix asphalt’, paper no. 09-1951, Annual meeting of the Transportation Research Board, 88th, Washington, DC, TRB, Washington, DC, USA, 18 pp.

Manolis, S, Decoo, T, Lum, P & Greco, M 2008, ‘Cold weather paving using warm mix asphalt technology’, Annual conference of the Transportation Association of Canada, 2008, Toronto, Ontario, TAC, Toronto, ON, Canada, 15 pp.

McKenzie, P 2006, ‘Taking a closer look at warm mix’, Better Roads, vol. 76, no. 6, June, pp. 64-9.


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MeadWestvaco Asphalt Innovations 2009a, Evotherm warm mix asphalt in Crow Wing County, Minnesota: eliminating thermal cracking at reduced cost, MeadWestvaco Asphalt Innovations, North Charleston, SC, USA.

MeadWestvaco Asphalt Innovations 2009b, Evotherm warm mix asphalt: construction of new taxiways for remote overnight parking area at the Ted Stevens Anchorage International Airport, largest cargo airport in the United States of America, MeadWestvaco Asphalt Innovations, North Charleston, SC, USA.

Middleton, B & Forfylow, RW 2009, ‘Evaluation of warm-mix asphalt produced with the Double Barrel Green process’, Transportation Research Record, no. 2126, pp. 19-26.

Nadeau, G 2012, Warm mix and the ‘Every Day Counts’ initiative, Asphalt Pavement Magazine, January February 2012, pp. 16-19.

Naidoo, K, Marais, H, Nortje, W, Rocher, K & Lewis, AJN 2011, ‘Getting started with warm mix asphalt in South Africa’, International conference on warm-mix asphalt, 2nd, 2011,St. Louis, MO, USA.

National Center for Asphalt Technology 2010, NCAT warm mix asphalt certification program, NCAT, Auburn University, Auburn, AL, USA, viewed 25 May 2011, <http://warmmixasphaltcertification.com/whitepaper.pdf>.

Needham, D 2009, Warm mix trials with eThekwini (Durban) Municipality, May 2009: “Leicester road trial”, field service report, AkzoNobel Surface Chemistry AB, South Africa.

Newcomb, D & Corrigan, M 2006, Material test framework for warm mix asphalt trials, National Asphalt Pavement Association, Warm Mix Asphalt Technical Working Group (WMA TWG), Lanham, MD, USA, viewed 25 May 2011, <http://www.warmmixasphalt.com/Publications-Guidelines.aspx>.

Nicholls, JC 2009, Review of Shell Thiopave sulphur-extended asphalt modifier, report no. TRL672, Transport Research Laboratory, Crowthorne, UK.

Olard, F, Noan, CL, Beduneau, E & Romier, A 2008, ‘Low energy asphalts for sustainable road construction’, Eurasphalt & Eurobitume congress, 4th, 2008, Copenhagen, Denmark, Eurasphalt & Eurobitume congress secretariat, Brussels, Belgium, 12 pp.

Oliviera, JRM, Silva, HMRD, Fonseca, B, Kim, Y, Hwang, S, Pyun, J, & Lee, HD 2011, ‘Laboratory and field study of a WMA mixture produced with a new temperature reduction additive’, International conference on warm-mix asphalt, 2nd, 2011,St. Louis, MO, USA.

Park, T-S 2012, ‘Innovative research programs of asphalt pavement in Korea’, REAAA Journal, vol. 17.

Perkin, SW 2009, Synthesis of warm mix asphalt paving strategies for use in Montana highway construction, MT-09-009/8117-38, Montana Department of Transportation, Helena, MT, USA.

Powell, RB & Taylor, A 2011 ‘Design, construction and performance of sulfur-modified mix in the WMA certification program at the NCAT pavement test track’, International conference on warm-mix asphalt, 2nd, 2011,St. Louis, MO, USA.

Preston, N 2007, ‘WAM: low temperature, low energy asphalt production’, AAPA pavements industry conference, 2007, Sydney, New South Wales, Australian Asphalt Pavements Association, Kew, Vic, 11 pp.


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Prowell, B & Hurley, G 2007, Evaluation of warm mix asphalt technologies, National Center for Asphalt Technology (NCAT), Auburn University, Auburn, AL, USA, 57 ppt. slides.

Prowell, BD, Hurley, GC & Crews, E 2007, ‘Field performance of warm-mix asphalt at National Center for Asphalt Technology Test Track’, Transportation Research Record, no. 1998, pp. 96-102.

Prowell, BD, Hurley, GC & Frank, B 2012 Warm-mix asphalt: best practices, 3rd edn, National Asphalt Pavement Association, Lanham, MD, USA.

Reinke, G, Engber, S, Glidden, S, Herlitzka, D & Veglahn, S 2011 ‘Evaluation of warm mix asphalt performance 2007 to present based on field performance and laboratory investigation’, International conference on warm-mix asphalt, 2nd, 2011,St. Louis, MO, USA.

Romier, A, Audeon, M, David, J & Martineau, Y 2004, ‘Low-energy asphalt (LEA) with the performance of hot-mix asphalt (HMA’), European Roads Review, special issue RGRA2, pp. 20-9.

Sasolwax 2005, Roads and trials with SASOBIT, Sasolwax, viewed 8 June 2012, <http://www.sasolwax.com/sasolwaxmedia/Downloads/Bitumen+Modification/Roads+and+trials.pdf>.

Solaimanian, M, Milander, S, Boz, I &Stoffels, S 2011, ‘Development of guidelines for usage of high percent rap in warm-mix asphalt pavements’, The Pennsylvania Department of Transportation Bureau of Planning and Research, Harrisburg, PA, USA.

South African Bitumen Association 2011a, Best practice guideline for warm mix asphalt, manual 32, SABITA, Howard Place, South Africa.

South African Bitumen Association 2011b, ‘Culmination of South Africa’s warm mix asphalt trials a huge success’, Asphalt News, vol. 25, no. 1, April.

Strickland, D, Colange, J, Martin, M & Deme, I 2008, ‘Performance properties of paving mixtures made with modified sulphur pellets’, International ISAP symposium on asphalt pavements and environment, 2008, Zurich, Switzerland, International Society of Asphalt Pavements (ISAP), White Bear Lake, MN, USA.

Tabib, S, Raymond, C & Le, L 2011 ‘Ontario’s experience with warm mix asphalt’, International conference on warm-mix asphalt, 2nd, 2011,St. Louis, MO, USA.

Timm, D, Tran, N, Taylor, A, Robbins, M & Powell, B 2009, Evaluation of mixture performance and structural capacity of pavements using Shell Thiopave, phase 1: mix design, laboratory performance evaluation and structural pavement analysis and design, report no. 09-05, National Center for Asphalt Technology (NCAT), Auburn University, Auburn, AL, USA.

Tran, N, Taylor, A & May, R 2010, ‘Laboratory performance assessment of sulfur-modified warm mixes’, International conference on asphalt pavements, 11th, Nagoya, Japan, International Society of Asphalt Pavements (ISAP), White Bear Lake, MN, USA, 10 pp.

Trewin, D 2003, Year book Australia 2003, no. 1301.0, Australian Bureau of Statistics (ABS), Canberra, ACT.

Ulmgren, N, Lundberg, R & Lundqvist, L 2011, ‘Low temperature asphalt (WMA) in Sweden’, International conference on warm-mix asphalt, 2nd, 2011,St. Louis, MO, USA.

Vargas-Nordcbeck, A & Timm, DH 2011 ‘Evaluation of pavement responses of warm mix asphalt sections at the NCAT Test Track’, International conference on warm-mix asphalt, 2nd, 2011,St. Louis, MO, USA.


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Willis, JR, West, R, Neslon, J, Taylor, A & Leatherman, K 2011 ‘Combining warm mix asphalt technologies with mixtures containing reclaimed asphalt pavement’, International conference on warm-mix asphalt, 2nd, 2011,St. Louis, MO, USA.

Wu, S, Han, J, Wen, J & Liu, Z 2010, ‘Laboratory evaluation of warm mix asphalt mixture’, International conference on asphalt pavements, 11th, 2010, Nagoya, Japan, International Society of Asphalt Pavements (ISAP), White Bear Lake, MN, USA, 10 pp.

Xiao, F, Amirkhanian, SN & Shen, J 2010, ‘Laboratory investigation of rheological and moisture susceptibility of WMA mixtures’, International conference on asphalt pavements, 11th, 2010, Nagoya, Japan, International Society of Asphalt Pavements (ISAP), White Bear Lake, MN, USA, 8 pp.

Zaumanis, M, Olesen, E & Haritonovs, V 2011 ‘Laboratory testing of organic and chemical warm mix asphalt technologies’, International conference on warm-mix asphalt, 2nd, 2011,St. Louis, MO, USA.

AASHTO Test Methods and Specifications

AASHTO M320-10–2010, Standard specification for performance-graded asphalt binder.

AASHTO MP-1–2004, Specification for performance graded asphalt binder.

AASHTO R26-01–2005, Standard recommended practice for certifying suppliers of performance-graded asphalt binders.

AASHTO R30-02–2002, Standard practice for mixture conditioning of hot-mix asphalt (HMA).

AASHTO T179-05–2005, Standard method of test for effect of heat and air on asphalt materials (Thin-Film Oven test) (ASTM Designation: D 1754).

AASHTO T195-67–2005, Standard method of test for determining degree of particle coating of bituminous-aggregate mixtures.

AASHTO T283–2007, Standard method of test for resistance of compacted hot mix asphalt (HMA) to moisture-induced damage.

AASHTO T320-10–2010, Standard method of test for determining the permanent shear strain and stiffness of asphalt mixtures using the Superpave shear tester (SST).

AASHTO T321-07–2007, Standard method of test for determining the fatigue life of compacted hot-mix asphalt (HMA) subjected to repeated flexural bending.

AASHTO T324-04–2004, Standard method of test for Hamburg wheel-track testing of compacted hot-mix asphalt (HMA).

AASHTO TP31-96–1996, Standard test method for determining the resilient modulus of bituminous mixtures by indirect tension.

AASHTO TP62-03–2005, Standard method of test for determining dynamic modulus of hot-mix asphalt concrete mixtures.


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European Standards

NF EN 13036-1:2010, Road and airfield surface characteristics: test methods: part 1: measurement of pavement surface macrotexture depth using a volumetric patch technique.

NF EN 13036-5:2006, Road and airfield surface characteristics: test methods: part 5: determination of longitudinal unevenness indices.


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APPENDIX A SUPERPAVE PERFORMANCE GRADE ASPHALT BINDER SPECIFICATION: SUMMARY

The table below is the standard summary table presented in the AASHTO MP 1 specification for performance graded asphalt binder. The following items may help to decipher this table:

The top several rows (all the rows above the ‘original binder’ row) are used to designate the desired PG grade. For instance, if the average 7-day maximum pavement design temperature is greater than 52 °C but less than 58 °C then you should use the ‘< 58’ column. The temperatures directly under the ‘< 58’ cell are selected based on the minimum pavement design temperature in °C.

No matter what the desired PG binder specification, the same tests are run. The PG specification (e.g. PG 58-22) just determines the temperature at which the tests are run.

Tests are run on the original binder (no simulated aging), RTFO residue (simulated short-term aging) and PAV residue (simulated long-term aging) in order to fully characterize the asphalt binder throughout its life. Notice that often the same test is run on different simulated binder ages. For instance, the dynamic shear test is run on all three simulated binder ages.

Table A 1: Performance graded asphalt binder specifications

34 40 46 10 16 22 28 34 40 46 16 22 28 34 40 10 16 22 28 34 40Average 7-day Maximum Pavement Design Temperature, oCa

Minimum Pavement Design Temperature, oCa -34 -40 -46 -10 -16 -22 -28 -34 -40 -46 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -40

Flash Point Temp, T 48, Minimum (oC) Viscosity, ASTM D 4402:b

Maximum, 3 Pa*s, Test Temp, oCDynamic Shear, TP 5:c

G*/sinδf, Minimum, 1.00 kPa Test Temp @ 10 rad/s, oC

Mass Loss, Maximum, percentDynamic Shear, TP 5:


PAV Aging Temperature, oCd

Dynamic Shear, TP 5:

G*/sinδf, Maximum, 5000 kPa Test Temp @ 10 rad/s, oCPhysical Hardeninge

Creep Stiffness, TP 1Determine the critical cracking temperature as described in PP 42Direct Tension, TP 3Determine the critical cracking temperature as described in PP 42

Performance Grade

-12 -18 -24 -30-24 -30 0 -6-36 -6 -12 -18

-30

-24 -30 -36 0 -6 -12 -18 -24 -30

-6 -12 -18 -24-18 -24 -30 0-30 -36 -6 -12-6 -12 -18 -24-24 -30 -36 0

22 19 16

Report

13 31 28 2525 22 19 1616 13 10 722 19

90 90

10 7 4 25

100 100

ROLLING THIN FILM OVEN RESIDUE (T 240)

1.00

46 52 58 64

ORIGINAL BINDER

230

135

PRESSURE AGING VESSEL RESIDUE (PP 1)

46 52 58 64

< 46 < 52 < 58 < 64

PG 46 PG 52 PG 58 PG 64

http://training.ce.washington.edu/WSDOT/Modules/03_materials/03-3_body.htm#performance_grade

http://training.ce.washington.edu/WSDOT/Modules/03_materials/03-3_body.htm#rtfo

http://training.ce.washington.edu/WSDOT/Modules/03_materials/03-3_body.htm#pav


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a Pavement temperatures are estimated from air temperatures using an algorithm contained in the LTPP Bind program, may be provided by the specifying agency, or by following the procedures as outlined in MP 2 and PP 28.

b This requirement may be waived at the discretion of the specifying agency if the supplier warrants that the asphalt binder can be adequately pumped and mixed at temperatures that meet all applicable safety standards.

c For quality control of unmodified asphalt binder production, measurement of the viscosity of the original asphalt binder may be used to supplement dynamic shear measurements of G*/sinδ at test temperatures where the asphalt is a Newtonian fluid.

d The PAV aging temperature is based on simulated climatic conditions and is one of three temperatures 90 °C, 90 °C or 110 °C. The PAV aging temperature is 100 °C for PG 58- and above, except in desert climates, where it is 110 °C.

e Physical hardening – TP 1 is performed on a set of asphalt beams according to Section 12, except the conditioning time is extended to 24 hours ± 10 minutes at 10 °C above the minimum performance temperature. The 24-hour stiffness and m – value are reported for information purposes only.

f G*/sinδ = high temperature stiffness and G*/sinδ = intermediate temperature stiffness. Source: Kennedy et al. (1994).

The tests run on the binder are listed in the left-hand column. They are not necessarily listed by their common names but the applicable AASHTO test procedure is listed. For instance, ‘Flash Point Temp. T 487, Minimum (°C)’ means that the flash point is measured according to AASHTO T 48-06 and that the value in the adjacent column represents the minimum allowable in degrees Centigrade.

7 AASHTO T48-06–2006, Standard method of test for flash and fire points by Cleveland open cup.

10 16 22 28 34 40 10 16 22 28 34 10 16 22 28 34Average 7-day Maximum Pavement Design Temperature, oCa

Minimum Pavement Design Temperature, oCa -10 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -10 -16 -22 -28 -34

Flash Point Temp, T 48, Minimum (oC) Viscosity, ASTM D 4402:b

Maximum, 3 Pa*s, Test Temp, oCDynamic Shear, TP 5:c


Mass Loss, Maximum, percentDynamic Shear, TP 5:


PAV Aging Temperature, oCd

Dynamic Shear, TP 5:

G*sinδf, Maximum, 5000 kPa Test Temp @ 10 rad/s, oCPhysical Hardeninge

Creep Stiffness, TP 1Determine the critical cracking temperature as described in PP 42Direct Tension, TP 3Determine the critical cracking temperature as described in PP 42

ORIGINAL BINDER

230

135

Performance Grade PG 70 PG 76 PG 82

1.00

70 76 82

PRESSURE AGING VESSEL RESIDUE (PP 1)

100 (110) 100 (110) 100 (110)

37 34 31 28

0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12 -18 -24

0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12 -18 -24

Report

70 76 82

ROLLING THIN FILM OVEN RESIDUE (T 240)

31 2819 37 34 25 4022

< 70 < 76 < 82

34 31 28 25

INFORMATION RETRIEVAL

Austroads, 2012, Review of Overseas Trials of Warm Mix Asphalt Pavements and Current Usage by Austroads Members, Sydney, A4, 76. AP-T215-12

Keywords: warm mix asphalt, state-of-the-art review, laboratory, hotmix asphalt, development trial, demonstration trial, validation/implementation trial

Abstract: This report presents a review of field trials of WMA technologies conducted in various countries in the world, with the emphasis on performance differences between WMA and conventional HMA and the identification of field performance data that could be used to complement the Austroads WMA evaluation field trials for Australian road conditions. A number of recommendations are made as a result of the review.

review of overseas trials of warm mix asphalt pavements and current usage by austroads members

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