pavimentazioni ap t270 14 post ageing characterisation of sprayed sealing binders

Technical Report AP-T270-14

Post-ageing Characterisation of Sprayed Sealing Binders

A Laboratory Study

Post-ageing Characterisation of Sprayed Sealing Binders: A Laboratory Study

Prepared By

Dr Young Choi and Dr Robert Urquhart

Publisher Austroads Ltd. Level 9, 287 Elizabeth Street Sydney NSW 2000 Australia Phone: +61 2 9264 7088 [email protected] www.austroads.com.au

Project Manager

John Esnouf

Abstract

This report presents the results of a laboratory study that was conducted as part of the development of a new-long term ageing (durability) test for bituminous binders used in sprayed seals in Australia.

Among the number of test methods reviewed and assessed in earlier studies, a test method known as the dynamic shear rheometer (DSR) flow test was found to be the most appropriate and was used to characterise binders that were ageing treated using a pressurised ageing vessel (PAV). Chemical analysis tests known as Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) were also conducted to provide information about the chemical processes that occurred during PAV ageing treatment.

The results obtained during this study will provide an important database for a field performance correlation study (using a field trial site where the tested binders have been placed), which is scheduled for 2014-15.

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: • 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 State Growth Tasmania • Department of Transport Northern Territory • Department of Territory and Municipal Services

Australian Capital Territory • Commonwealth Department of Infrastructure

and Regional Development • Australian Local Government Association • New Zealand Transport Agency.

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

Keywords ageing, binder, durability, sprayed seal, temperature, test method, DSR test, CTOD test, extensiometer test

Published August 2014 Pages 58

ISBN 978-1-925037-75-3

Austroads Project No. TT1818

Austroads Publication No. AP-T270-14

© Austroads Ltd 2014

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.

Acknowledgements Thanks to Shannon Malone, Elizabeth Woodall and Khar Yean Khoo of ARRB Group for their assistance with the experimental work and helpful discussions during the project. Thanks also to Dr Alex Duan of the University of Melbourne for helpful discussions and supervision of the gel permeation chromatography (GPC) measurements which are included in this report.

This report has been prepared for Austroads as part of its work to promote improved Australian and New Zealand transport outcomes by providing expert technical input on road and road transport issues.

Individual road agencies will determine their response to this report following consideration of their legislative or administrative arrangements, available funding, as well as local circumstances and priorities.

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.

.


Summary

The use of durable binders in road construction is a means by which long-lasting surfacings can be produced. The durability performance of bitumen binders in sprayed seals has traditionally been assessed in Australia (for over 40 years) using an established laboratory test method known as the durability test (AS 2341.13-1997). The durability test method, however, has a number of issues (e.g. test equipment sustainability) and Australian practitioners identified an urgent need for a more robust test method that could replace the current test method, while maintaining the important functions of the method.

This report presents the research outcomes of the second year of work on the three-year Austroads project TT1818 (Development and Validation of a New Long-term Ageing Test for Bitumens and PMBs). The main goal of the project is to develop a new durability test method that satisfies Australian needs; i.e. can be used to assess the durability of both bitumen and polymer modified binders (PMBs). This report supplements Austroads reports AP-T225-13: Development of Long-term Ageing Test Method for Sprayed Sealing Binders (Austroads 2013a) and AP-T244-13: Investigation of Long-term Ageing Characterisation Test Methods for Sprayed Sealing Binders (Austroads 2013b).

The second year of work initially focused on assessing the effectiveness of two post-pressure ageing vessel (PAV) characterisation test methods that were selected during the first year of the study (Austroads 2013a) based on literature evidence that these tests could be used to predict the low temperature cracking performance of binders. The two test methods were the dynamic shear rheometer (DSR) flow test and the extensiometer crack tip opening displacement (CTOD) test. A test temperature of 15 °C was used to conduct both tests, as previous studies indicated it was difficult to determine the properties of the binders at lower temperatures (e.g. 10 °C).

In addition to rheological characterisation experiments, the chemical properties of the binders were determined using Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The main aim of these experiments was to observe the chemical changes that occurred when binders were subjected to PAV ageing treatment.

A range of bitumens and PMBs were subjected to PAV ageing for different periods of time (i.e. 0, 30 and 72 hours) and their properties were characterised using the tests mentioned above. The results of DSR flow tests indicated that changes in binder properties depended on the type of binder studied and the PAV ageing time. The changes in binder properties were found to increase as the PAV ageing time was increased. Two test parameters derived from DSR flow tests have been determined for the range of binders studied. The extensiometer CTOD test in its current form could not be effectively used to characterise the properties of PAV aged binders.

Chemical characterisation experiments indicated that PAV ageing increased the number of oxygen-containing chemical groups in the binders (i.e. oxidised the binders) and increased the number of aromatic carbon groups. The polymer in each of the PMBs studied appeared to break into small fragments when samples were PAV aged.

The laboratory test results obtained during the second year of work will be used to complement a field validation study, which is proposed in the third year of the project (2014–15). Many of the binders characterised in the second year of the project were used in a sprayed sealing trial site at Coober Pedy in South Australia, which was constructed in November 2011. The proposed field validation study will compare the properties and performance of binders after field ageing with their properties after laboratory PAV ageing tests.

Austroads 2014 | page i


Contents

1. Introduction ............................................................................................................................................. 1 1.1 Ageing of Binder and Durability Test Method ........................................................................................... 1 1.2 Australian Durability Test Method: Problem Statement ........................................................................... 1 1.3 Development of New Durability Test Method: Stage 1 ............................................................................ 2 1.4 Development of New Durability Test Method: Stage 2 ............................................................................ 2

1.4.1 Year 2 of Stage 2: About This Report ........................................................................................ 3

2. Background Information ........................................................................................................................ 4 2.1 Definition of Low Temperature Characterisation Tests ............................................................................ 4 2.2 Dynamic Shear Rheometer ...................................................................................................................... 4 2.3 DSR Flow Test ......................................................................................................................................... 4 2.4 Critical Tip Opening Displacement (CTOD) Test ..................................................................................... 5 2.5 CTOD Test and Australian Extensiometer ............................................................................................... 6 2.6 Selection of Candidate Test Methods ...................................................................................................... 7 2.7 Determination of Test Temperature ......................................................................................................... 8

3. Materials ................................................................................................................................................ 10

4. PAV Ageing Treatment Method ........................................................................................................... 12 4.1 PAV Ageing Regime for the New Durability Test ................................................................................... 12 4.2 Shorter-term PAV Ageing Regime ......................................................................................................... 13

5. DSR Flow Tests: Test Procedure and Derived Test Parameters ..................................................... 16 5.1 Preparation of Samples for DSR testing ................................................................................................ 16 5.2 DSR Test Conditions .............................................................................................................................. 16 5.3 Test Parameters Obtained from DSR Flow Tests .................................................................................. 17

5.3.1 Yield Energy ............................................................................................................................. 17 5.3.2 Stress Ratio .............................................................................................................................. 19

6. DSR Flow Mode Tests: Results and Analysis ................................................................................... 22 6.1 Yield Energy Values ............................................................................................................................... 22 6.2 Stress Ratio Results ............................................................................................................................... 24 6.3 Summary ................................................................................................................................................ 25

7. Extensiometer CTOD Tests: Test Procedure and Issues ................................................................. 26 7.1 Sample Preparation ................................................................................................................................ 26 7.2 Test Procedure and Data Interpretation ................................................................................................. 27 7.3 Extensiometer CTOD Test: Issues and Limitations ............................................................................... 29

8. Chemical Property Investigations ...................................................................................................... 31 8.1 Introduction ............................................................................................................................................. 31

8.1.1 Fourier Transform Infrared (FTIR) Spectroscopy ..................................................................... 31 8.1.2 Gel Permeation Chromatography (GPC) ................................................................................. 31

8.2 Test Procedures ..................................................................................................................................... 32 8.2.1 FTIR Spectroscopy ................................................................................................................... 32 8.2.2 Gel Permeation Chromatography (GPC) ................................................................................. 32

9. FTIR and GPC: Test Results and Analysis ........................................................................................ 33 9.1 FTIR Spectroscopy Test Results and Analysis ...................................................................................... 33

9.1.1 Spectral Changes on PAV Ageing ........................................................................................... 33 9.1.2 Quantitative Analysis of Spectral Changes .............................................................................. 36

9.2 GPC Test Results and Analysis ............................................................................................................. 38

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10. Summary and Conclusions ................................................................................................................. 41

References ...................................................................................................................................................... 42 Appendix A DSR Flow Test Results ........................................................................................................... 44 Appendix B FTIR Chemical Assignments .................................................................................................. 50 Appendix C Other FTIR Spectroscopy Results ......................................................................................... 51 Appendix D Other GPC Test Results .......................................................................................................... 55

Tables Table 2.1: Evaluation of low temperature characterisation tests for binders .................................................. 8 Table 2.2: Road surface temperature distribution in different Australian cities ............................................... 9 Table 3.1: Description of binders .................................................................................................................. 10 Table 4.1: Parameters used for simulation of the hardening of C170 bitumen placed at the

Coober Pedy site .......................................................................................................................... 14 Table 5.1: Sample mounting temperature used for DSR flow tests .............................................................. 16 Table 6.1: Yield energy values ...................................................................................................................... 22 Table 6.2: Stress ratio results ....................................................................................................................... 24 Table 9.1: Quantitative changes in FTIR spectral peaks during PAV ageing ............................................... 37

Figures Figure 2.1: Schematic diagram of dynamic shear rheometer (DSR) and a typical material response ............ 5 Figure 2.2: CTOD test specimens (a set of three with varying notch sizes) .................................................... 6 Figure 2.3: Schematic diagram of the extensiometer ....................................................................................... 7 Figure 4.1: Schematic of the PAV test system ............................................................................................... 12 Figure 4.2: Simulated binder hardening of the C170 bitumen in the Coober Pedy site ................................. 14 Figure 4.3: Binder hardening of C170 bitumen during laboratory PAV treatment (up to 96 hours) ............... 15 Figure 5.1: Typical appearance of a distressed sample after a DSR flow test .............................................. 17 Figure 5.2: Example of a yield energy calculation obtained from a DSR flow test result (72 hours

PAV aged Coober Pedy C170 bitumen) ...................................................................................... 18 Figure 5.3: Example of a yield energy calculation of a binder that did not show a distinct

maximum in the stress-strain curve ............................................................................................. 18 Figure 5.4: Typical extensiometer force-displacement curves ....................................................................... 19 Figure 5.5: Example of stress ratio calculation from a DSR flow test result (72 hours PAV aged

Coober Pedy C170 bitumen) ........................................................................................................ 20 Figure 5.6: Example of stress ratio calculation from a DSR flow test result where a stress peak

towards small strains is not evident (unaged S20E) .................................................................... 21 Figure 6.1: Varying yield energy values (at 2 strain) against varying PAV ageing time ................................ 23 Figure 6.2: Changes in stress ratio results (at 2 strain) with PAV ageing time .............................................. 25 Figure 7.1: Photos of extensiometer CTOD specimen moulds and a notched specimen ready

for testing ...................................................................................................................................... 26 Figure 7.2: Example of a set of extensiometer CTOD specimens after testing (72 hours PAV

aged S20E) .................................................................................................................................. 27 Figure 7.3: Different force-displacement curves representing a set of three specimens of

varying ligament size (72 hours PAV aged S20E) ....................................................................... 28 Figure 7.4: Extrapolation to determine the essential work of fracture (EWF) using the specific

work of fracture data obtained for a particular sample (72 hours PAV aged S20E) .................... 29 Figure 7.5: Example of test data that provides a negative EWF value (30 hours PAV aged

SAMI S20E SS ‘as delivered’)...................................................................................................... 30 Figure 9.1: FTIR spectra obtained for a sample of Coober Pedy C170 bitumen after different

periods of PAV ageing ................................................................................................................. 33 Figure 9.2: FTIR spectra obtained for the S20E binder after different periods of PAV ageing ...................... 34 Figure 9.3: FTIR spectra obtained for the S35E binder after different periods of PAV ageing ...................... 36 Figure 9.4: GPC results obtained for samples of neat SBS polymer and the Coober Pedy C170

bitumen after different periods of PAV ageing ............................................................................. 38 Figure 9.5: GPC results obtained for the S20E binder after different periods of PAV ageing ....................... 39

Austroads 2014 | page iii


1. Introduction

1.1 Ageing of Binder and Durability Test Method Binders in road surfacings experience gradual changes in their rheological (e.g. viscosity), cohesion and adhesion properties during their service lives. The hardening of binders with time (i.e. increase in viscosity) is mainly due to binder oxidation, although other factors (e.g. evaporative hardening) can also be involved (Read & Whiteoak 2003). For this reason, durability test methods (also often referred to as ‘ageing resistance tests’) in use worldwide typically aim to assess the resistance of binders to oxidative hardening (Airey 2003, Choi 2005). This report focuses on issues related to long-term ageing only, since short-term ageing (i.e. rapid hardening of binder that occurs during the construction stage) is not a critical performance issue for the binders used in sprayed seals, which are the subject of this study.

A durability test method essentially involves two elements: an ageing conditioning step and a binder characterisation step. During the ageing conditioning step, the binder is subjected to accelerated ageing so that many years of binder ageing in the field (often more than 10 years) can be simulated in the laboratory within a short testing time (e.g. a week). A characterisation step is then used to assess the properties of the laboratory aged binder. The ageing resistance of a binder can be assessed in a number of ways, such as by comparing a post-ageing property to the same property measured before it was treated (this is typically expressed as a ratio), or by observing whether a post-ageing property displays a higher/lower value than that of other binders. All the approaches are based on the principle that a durable binder will show a lower rate of property change than a less durable binder when both samples are subjected to the same ageing conditions.

1.2 Australian Durability Test Method: Problem Statement The principle described above is used in the Australian durability test (AS 2341.13-1997) as binders are initially aged in a rolling thin film oven (RTFO) at an elevated temperature for an extended period. The post-ageing property that is determined after ageing is binder viscosity. This is determined in the durability test using the ‘Shell sliding plate micro-viscometer’ (AS 2341.5-1997). The ageing resistance of different binders is assessed by comparing the time taken by each binder to reach a specified viscosity value (i.e. a durable binder will take a longer time for its viscosity to increase).

The method has been widely used in Australia for over 40 years and is one of the important criteria used to select quality binders. However, a number of issues have been identified with the durability test over the years. These include:

The equipment required for the method (i.e. ageing oven and viscosity measuring device) are Australian-specific and supplied/maintained on an ‘as needed’ basis only. The number of users in Australia is small and procuring of the necessary equipment (or equipment components when the devices need to be repaired) is not sustainable due to the lack of commercial interest.

The test procedure is rather complex and, more importantly, takes a long time to perform (over two weeks depending on how durable the binder is). A laboratory may have to have additional ageing ovens so that other tests that use the same equipment (e.g. the RTFO test (AS 2341.10-1994)) can be conducted while durability test(s) are performed. If bitumen is imported rather than manufactured locally, testing time and equipment availability may also cause logistical problems to overseas suppliers. In the next few years, it is expected that only a small proportion of the bitumen used in Australia will be manufactured locally.

The method was originally developed for the testing of bitumens only. It is therefore considered inappropriate for testing of other binders, particularly polymer modified binders (PMBs). Due to increasing traffic loads, the use of these high-performance binders in sprayed seals is now a common practice.

Austroads 2014 | page 1


The durability test parameter is currently determined using binder viscosity results, which are obtained at

a temperature of 45 °C. The reduction in the effectiveness of binders after they have aged on the road, however, is generally a result of their increased susceptibility to cracking at lower temperatures. Therefore, the current viscosity test conditions used in the durability test may not be optimized to assess the low temperature performance of binders.

Consequently, the Australian highway engineering community identified an urgent need for a more robust durability test method. Austroads therefore commissioned ARRB Group to conduct research into the development of a new durability test method. This task is being carried out under the guidance of the Austroads Bituminous Surfacings Working Group (BSWG).

1.3 Development of New Durability Test Method: Stage 1 The most urgent issue associated with the Australian durability test was considered to be that of equipment sustainability. It was believed that this issue could be resolved if the current Australian-specific devices were replaced with internationally used ones, as internationally used devices would not be expected to have the same procurement and maintenance issues. Research conducted during Austroads project TT1354 Optimising Binder Performance (Austroads 2013a), showed that the pressure ageing vessel (PAV, an ageing device widely used in the USA and Europe) and the dynamic shear rheometer (DSR, a binder property testing device widely used overseas) could be used as effective replacements for the RTFO treatment step and the Shell sliding plate micro-viscometer measurements conducted during the current Australian durability test, respectively.

One of the main intentions of this ‘equipment replacement task’ was to ensure that the essence of the current durability test method was maintained. A number of Australian states and territories include binder durability in their specifications for bitumen, so it was desired that any test outputs obtained with the new devices be related to durability test results obtained by the current method. During studies conducted to evaluate the new devices, it was found that there was a direct correlation between DSR results obtained after PAV ageing of the binders (referred to as ‘post-PAV viscosities’) and durability test results obtained by the current method (Austroads 2013a). This correlation will allow currently specified durability limits to be translated into equivalent post-PAV viscosity limits.

Work conducted during the equipment replacement task also indicated that binders could be aged in the PAV to a similar level as that used in the durability test but in a much shorter time period than by RTFO treatment. Thus, use of the PAV to age binders also addressed testing duration issues associated with the current durability test as described above. The results obtained during Stage 1 of the development work are reported in detail in Austroads (2013a).

1.4 Development of New Durability Test Method: Stage 2 With the two urgent, practical issues (i.e. equipment sustainability and testing time) resolved in the first stage of work, the remaining issues listed in Section 1.2 could be addressed in the second stage of work. These issues are of a more fundamental nature than those addressed in the Stage 1 work and will require more extensive studies to resolve. One of the reasons is that the new durability method should be able to assess the ageing performance of PMBs. PMBs tend to exhibit complex visco-elastic properties and so the properties of aged PMBs cannot be determined by a simple viscosity measurement. Another reason is that concerns about aged/hardened binders are generally related to their resistance to cracking at low temperatures, whereas the current post ageing test is conducted at 45 °C. If these issues are to be addressed, fundamental changes to the post-ageing binder characterization test method and testing conditions are required.



Consequently, a three-year research project (2012–15) to conduct the second stage of work has been established: Austroads TT1818 Development and Validation of a New Long-term Ageing Test for Bitumens and PMBs. The work in each of the project years is briefly described as follows:

Year 1: literature review and selection of candidate test methods for a more in-depth experimental study in the following years (completed in 2012–13).

Year 2: experimental study of different binders using the identified test methods (the work presented in this report).

Year 3: assessment of the correlation between results obtained by the identified test methods and binder field properties/performance (to be conducted during 2014–15).

The first step in the second stage of work was to review possible test methods that could be used to characterise the low temperature properties of binders after long-term ageing. An extensive review of candidate test methods and preliminary experiments conducted during 2012–13 (Austroads 2013b) indicated that the dynamic shear rheometer (DSR) flow test and the extensiometer cracking tip opening displacement (CTOD) test were the most promising tests for further study.

Year 2 of Stage 2: About This Report 1.4.1It is envisaged that the new durability test protocol will only require one test method for the post-ageing characterisation step. It was nonetheless agreed to start the second year of work using the two most promising test methods identified during Stage 1, in case one of the methods was not suitable for characterising the properties of Australian PAV aged binders. Studies were also performed using two test methods for the reasons listed below:

One of the important requirements considered during the selection of candidate test methods (Austroads 2013b) was that the test equipment needed to be locally available. The extensiometer is an Australian device, so a CTOD test utilising this device was considered worth exploring. The DSR is not widely used for bituminous binder testing in Australia, but is a very common binder testing device overseas. DSRs can be readily purchased in Australia from overseas manufacturers.

The extensiometer and the DSR subject binders to very different types of loading. The extensiometer subjects binders to tension, while the DSR subjects binders to shear. Use of both test methods was therefore anticipated to give information about binder properties when materials were subjected to different types of loading.

In addition to the rheological studies described above, the chemical properties of the binders studied were determined in this investigation using Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The main aim of these experiments was to observe the chemical changes that occurred when binders were subjected to PAV ageing treatment. These experiments were expected to complement the results of rheological studies, and provide more fundamental information about the changes that occur when binders are PAV aged.

During the current study, a range of bitumens and PMBs were subjected to PAV ageing for different periods of time (i.e. 0, 30 and 72 hours) and their properties were characterised using the tests mentioned above. Many of the binders studied were materials used for a recent Austroads sprayed sealing trial site which was constructed in Coober Pedy in South Australia in November 2011 (Austroads 2013c). The results presented and discussed in this report are expected to provide an important database for a field validation study scheduled for 2014–15. It is anticipated that the field performance study will compare the properties and performance of binders after field ageing at the Coober Pedy trial site, with their properties after laboratory PAV ageing tests.

This report supplements the Austroads reports AP-T225-13: Development of Long-term Ageing Test Method for Sprayed Sealing Binders (Austroads 2013a) and AP-T244-13: Investigation of Long-term Ageing Characterisation Test Methods for Sprayed Sealing Binders (Austroads 2013b).



2. Background Information

Based on the review of candidate test methods for the post-ageing characterisation step of the new durability test protocol (Austroads 2013b), the DSR flow test and the extensiometer CTOD tests were used to characterise the properties of PAV aged binders during this study. Some of the details from the test method review (Austroads 2013b) have been reproduced below (with additional information included where applicable) to provide further background to the current work.

2.1 Definition of Low Temperature Characterisation Tests During the test method review (Austroads 2013b), it was noted that temperatures considered to be low pavement temperatures in Australia differ considerably from those considered to be ‘low temperatures’ overseas. This is due to the generally mild climate in Australia, where temperatures above freezing are considered to represent low pavement temperatures. In many overseas regions, such as in North America or Northern Europe, pavements are subjected to much lower temperatures (e.g. –20 °C) during winter.

Due to these climatic differences, it appears that test methods that are referred to overseas as being conducted at ‘intermediate temperatures’ are better candidates for a low temperature test for application in Australia. Many test methods that are used to determine ‘low temperature’ performance overseas are not suitable for use in Australia as they use very low test temperatures. Use of these low temperatures will likely cause the binders to fail by a different distress mode than that occurs with binders used under Australian conditions.

2.2 Dynamic Shear Rheometer The DSR is a binder test device used widely in many parts of the world. The device was developed from several different research tools that measured the flow and deformation characteristics of a wide range of materials. In the early 1990s, the US Strategic Highway Research Program (SHRP) adopted the DSR as the basis for a new national specification for binders used in pavement applications. The device is currently a key instrument for binder characterization tests in Europe (EN 14770:2012) and the USA (AASHTO T315-12:2012, ASTM D7175-08:2008).

The DSR test on bituminous binders is performed using thin, circular samples, which are sandwiched between two metal discs. By oscillating one of the discs (normally the top disc is in motion while the bottom one is fixed), the binder sample is sheared clockwise and anti-clockwise to a pre-defined strain at a pre-defined oscillation frequency. The test is typically conducted over a range of temperatures and oscillation frequencies so that visco-elastic properties of a binder can be assessed under varying test conditions. A typical visco-elastic material response under the DSR oscillation test is illustrated in Figure 2.1. From the applied torque and resultant angular strain (both are recorded as a function of time), the visco-elastic parameters, namely G* (complex shear modulus) and δ (phase angle), can be calculated.

2.3 DSR Flow Test The DSR can also be operated in a non-oscillation mode. One such case is the DSR flow test as used by Johnson, Wen and Bahia (2009). This test involves subjecting binder specimens to shear loading using a constant shear rate. The area under the stress-strain curve (up to the maximum stress/peak point on the curve) is then used to calculate a ‘yield energy’ test parameter (refer to Section 5.3.1).



Figure 2.1: Schematic diagram of dynamic shear rheometer (DSR) and a typical material response

Source: Austroads (2013b).

Johnson, Wen and Bahia (2009) subjected five binders to DSR flow tests and compared the yield energy results obtained with the fatigue resistance of pavements that were assessed using a full-scale accelerated loading facility (ALF) tester (i.e. cumulative crack length data). They found an excellent correlation between yield energy and ALF cracking length (R2 = 0.99) when the yield energy results obtained at a shear rate of 0.0075 s-1 were used. The loading time during the experiments was about 15 minutes at the given shear rate. They also analysed the data in a more fundamental manner using the visco-elastic continuum damage (VECD) theory, but found difficulties in applying the theory to PMBs due to the non-linear behaviour of some of the binders.

2.4 Critical Tip Opening Displacement (CTOD) Test The critical tip opening displacement (CTOD) test was developed in the USA. The test has a very similar operational principle to the force ductilometer test (AASHTO T300-11:2011) and is indeed conducted using the same device. The specimen, however, has a different shape (i.e. a double notched specimen as shown in Figure 2.2) to that used in the force ductilometer test. Three specimens (with varying notch sizes) are needed to conduct a test. These specimens are fabricated using a specially designed sample mould. At a designated test temperature (typically 15 °C), the specimens are elongated at a constant speed of 50 mm/min (i.e. 0.83 mm/s). Another difference to the force ductilometer test is that the specimens are elongated until a distinctive failure point is recorded. For example, the test is normally conducted at 15 °C but needs to be re-tested at a lower temperature (e.g. 4 °C) if any of the specimens do not fail at the initial temperature. The force-displacement curves obtained from the three specimens are used to calculate essential work of fracture (EWF) and the CTOD parameter (in mm) as the test results.

Gibson et al. (2012) reported on a pooled fund study initiated by the Federal Highway Administration (FHWA) which aimed to find a better binder fatigue resistance parameter than the current DSR parameter (i.e. G*∙sin δ) that is utilised in the USA. A full-scale pavement test was conducted at the FHWA pavement test facility, where test sections were constructed using 12 binders (including PMBs). Each of these 12 binders were characterised with nine different tests, such as DSR G*∙sin δ, DSR fatigue test in various modes, direct tension tester (DTT), bending beam rheometer (BBR), and the CTOD test. Comparisons were made between laboratory test results and the crack resistance of pavements as assessed in the FHWA test facility. The significance of each binder test parameter was assessed using a statistical method (i.e. composite statistical score). The results from the CTOD tests showed the best correlation with pavement crack resistance.

Instrument records data as a time series of torque (stress) and angular position (strain) measurements

25 mm diameter rotor with 1 mm thick sample oscillating with constant amplitude angular motion (sinusoidal motion)

Angular displacement (strain)

Torque (stress) Time >

Phase lag



Figure 2.2: CTOD test specimens (a set of three with varying notch sizes)

Source: Andriescu and Hesp (2009).

A potential issue in using the CTOD test method as a post-ageing characterisation tool is the relatively large amount of sample required. Since a single test run requires a set of three specimens, about 80 g of treated binder is required (i.e. 160 g for duplicate tests). Producing such a large quantity of aged binder sample may be problematic due to the limited amount of aged binder typically available from one round of PAV treatment (refer to Table 2.1).

2.5 CTOD Test and Australian Extensiometer In Australia, a test device known as the extensiometer (Austroads AGPT/T124) has been used to assess binder properties (particularly for PMBs) at low service temperatures (Figure 2.3).

The device was developed during the 1990s and was based on the principle of the force ductilometer test (AASHTO T300-11:2011). At the time of development, an Australian binder test device known as the elastometer (Austroads AGPT/T121) was already in use to characterise the properties of PMBs at high service temperatures (e.g. 60 °C). It was envisaged that the force ductility test function could be incorporated into the existing elastometer by re-designing the test frame (e.g. extending the test frame to allow samples to be stretched a greater distance than the elastometer). Modifications to the elastometer were expected to allow the device to determine both the high and low temperature properties of binders, without the need for a separate test frame. The low temperature force ductilometer function of the elastometer was referred to as the ‘extensiometer’ mode of the elastometer. Even though the extensiometer differs from a force ductilometer in terms of specimen shape and displacement range, the operational principle of both devices is the same.



Figure 2.3: Schematic diagram of the extensiometer

Source: Modified from Austroads (AGPT/T124).

The extensiometer test in its standard form was not chosen for further use due to a number of testing issues observed during the preliminary investigation (Austroads 2013b). It was nonetheless found from the investigation that this device could instead be used to conduct the CTOD test described in the previous section. This new method was referred to as the ‘extensiometer CTOD’ test and is reported in detail in Section 7.

2.6 Selection of Candidate Test Methods Table 2.1 provides a summary of evaluations made for the test methods described above, which are based on the conclusions described in Austroads (2013b).

A number of factors were considered during the selection process for the rheological characterisation tests that were conducted during the previous study (Austroads 2013b). The factors are listed in the table in terms of perceived importance, where the most important factors are toward the left-hand side of the table. Equipment sustainability (as it applies in Australia) was considered very important, since a test method relying on unsustainable equipment would not be able to be used in the future even if the method was very effective. This was followed by ‘how appropriate is the test for the new Australian durability test?’ when it was assessed from operational (i.e. is the test easy to perform?) and fundamental perspectives (i.e. would the test be able to correctly evaluate binders?).



The DSR flow and the extensiometer CTOD tests were selected for further investigation based on the evaluations made in Table 2.1, followed by some preliminary experiments as reported in Austroads (2013b).

Table 2.1: Evaluation of low temperature characterisation tests for binders

Test method Equipment issue Appropriateness as the post-ageing test for the new Australian durability test

Note

Available in Australia?

Would it be sustainable?

Operational issues Fundamental issues

DSR flow test Available Sustainable: the DSR is one of the most widely used devices around the world.

Appropriate: one specimen requires less than 2 g of binder. Multiple specimens can be prepared from one PAV sample dish.

Appropriate: satisfactory correlations to fatigue crack resistance at intermediate temperatures have been observed in overseas studies.

The device is also used overseas for binder testing at high service temperatures (e.g. 60 °C). The test procedure for fatigue resistance assessment has not been formally accepted in the USA yet.

CTOD test The test uses the force ductilometer tester, but requires a special sample mould.

A set of three specimens is needed for a single test run and this requires about 80 g of binder (i.e. 160 g for duplicate tests)*.

Appropriate: very satisfactory correlations to fatigue crack resistance at intermediate temperatures were observed from a full-scale pavement study in the USA.

The test requires a fairly large amount of aged sample (more than that produced easily by the PAV ageing process). The test method has not been formally accepted in the US yet.

Extensiometer CTOD test

Available May experience sustainability issues due to limited demands (used only in Australia).

Appropriate: one specimen requires about 3 g of binder. Multiple specimens can be prepared from one PAV sample dish*.

Appropriate: very satisfactory correlations to fatigue crack resistance at intermediate temperatures were observed for the original CTOD test.

Extensiometer can be used to conduct the CTOD test (refer to Section 7).

* Note: the PAV ageing process of the new Australian durability test can produce about 10 g of aged binder per sample dish (10 dishes per one round of test).

2.7 Determination of Test Temperature Based on a preliminary assessment of the candidate test methods (Austroads 2013b), it appeared that neither the DSR flow or extensiometer CTOD tests could be used to effectively assess the properties of PAV treated binders at 10 °C. Testing issues associated with characterising binders at 10 °C included specimen failure during handling and the strength of the materials exceeding the measurable limits of the test equipment. These issues appeared to be related to the very stiff and brittle nature of PAV aged binders at low temperatures. As preliminary tests (Austroads 2013b) indicated that these testing issues could be overcome if a slightly higher test temperature (15 °C) was used to characterise the properties of PAV aged binders, DSR flow and extensiometer CTOD tests were conducted in this study using a test temperature of 15 °C.

An issue considered during the selection of a test temperature was whether a temperature of 15 °C would be representative of low road surface temperatures in Australia. This was evaluated using the road surface temperature distribution data reported by Dickinson (1981), as presented in Table 2.2.



Table 2.2: Road surface temperature distribution in different Australian cities

Region % of days below 15 °C during a year

Target test temperature

% of days above 15 °C during a year

Canberra 40

15 °C

60

Melbourne 46 54

Sydney 16.5 83.5

Perth 17 83

Brisbane 4 96

Darwin 0.1 99.9

Average 20.6 79.4 Source: Based on Dickinson (1981).

Table 2.2 provides information on the number of days in each year that the road surface temperature is both below and above 15 °C for each of the major Australian cities (in terms of the percentage of days during a year). For example, in Sydney, the road surface temperature is above 15 °C on 305 days of the year (i.e. 83.5% of 365 days). The percentage of days above 15 °C varies according to the climate in each city (where cities that have warmer climates have a higher percentage of days with road temperatures greater than 15 °C).

From Table 2.2, a temperature of 15 °C appears to be a reasonable temperature for representing the lower range of road surface temperatures in Australian cities, if the results in the table are considered as a whole (i.e. the average percentage periods below/above 15 °C are 20.6% and 79.4%, respectively).

Shortcomings of using this testing temperature would be that:

Some of the cities that have colder climates (e.g. Melbourne) may be over-represented (e.g. a test temperature of 9 °C may be a better representation for this region). This could also be the case for some high mountain areas or inland areas, where road surface temperatures could be lower than those recorded in cities near the sea.

A test temperature of 15 °C may not be low enough to represent the ‘lowest road surface temperatures’ that can be recorded in different areas of Australia. Testing of binders at the lowest recorded road surface temperature would be a ‘worst-case scenario’, which may be able to provide more useful information in terms of binder crack resistance.

A test temperature of 15 °C was selected for use in this study as DSR flow and extensiometer CTOD tests could not be effectively performed on PAV treated binders at lower temperatures. A test temperature of 15 °C also appeared to be a reasonable representation of low road surface temperatures in the major Australian cities. While the use of lower testing temperatures (e.g. 10 °C or 4 °C) may be preferred from a fundamental perspective, this was not pursued as it was not possible to effectively perform DSR flow and extensiometer CTOD tests on PAV treated binders at these temperatures.



3. Materials

It was noted in Section 1.4 that it is proposed in the third year of this project to investigate the relationship between the results obtained for binders after PAV ageing, and binder field properties and performance (i.e. conduct a field validation trial). In order to achieve this objective, it was decided to predominantly use binders in the current year of the project that were used to construct an Austroads PMB trial site in Coober Pedy in South Australia. Use of these types of binders is expected to allow the relationship between binder properties after PAV ageing and differences in road field performance to be investigated, as the results obtained after PAV ageing will be able to be directly compared with the performance/properties of the same binders at the Coober Pedy trial site.

The Coober Pedy trial site was constructed in November 2011 as part of a comprehensive field trial study that was performed to validate and rank the performance (e.g. crack resistance) of PMB sprayed seal binders. Details of the field trial study have been reported in Austroads (2013c).

The binders used in the Coober Pedy trial were all commercial products manufactured according to normal practices of each supplier. The binders included Austroads grade PMBs (Austroads AGPT/T190) and some proprietary PMB products. A Class 170 (C170) bitumen was included in the trial as the control. Table 3.1 provides brief descriptions of these binders.

Binder samples were obtained during the Coober Pedy trial at two stages of product delivery in order to determine if PMB properties changed during transport to the trial site (Austroads 2013c). Samples were collected from supplier’s tanks after PMB manufacture (‘as manufactured’ samples) as well as from delivery bulkers when they arrived at the trial sites (‘as delivered’ samples). Unless otherwise noted, the Coober Pedy trial binders used in this study were obtained at the ‘as delivered’ stage. These types of binders were selected as it was thought that these would better represent the binders that were sprayed on the road. Use of these types of binders would be expected to allow better comparisons to be made between binder properties after PAV ageing and field performance in the third year of the project.

It is noted that Table 3.1 includes other binders that were not used for the Coober Pedy PMB trial. These are explained below.

Table 3.1: Description of binders

Binder reference Description

Coober Pedy C170 bitumen Class 170 bitumen (according to AS 2008-2013) used in the Coober Pedy trial

Cooma C170 bitumen Class 170 bitumen (according to AS 2008-2013) used in the Cooma trial

S10E Sealing grade binders used in the Coober Pedy trial Classified according to the Austroads PMB specification (Austroads AGPT/T190) S15E

S20E

S35E

S45R

Shell S5E Proprietary binder used in the Coober Pedy trial

SAMI S20E SS as delivered Proprietary binder used in the Coober Pedy trial (sample collected at the site during construction)

SAMI S20E SS as manufactured Proprietary binder used in the Coober Pedy trial (sample collected from the supplier’s tank after manufacture)

ARRB 6% SBS PMB containing 6% SBS (styrene-butadiene-styrene) polymer manufactured at the ARRB laboratory



The sample of Cooma C170 bitumen that was tested in this study was used in another sprayed sealing trial (at Cooma in New South Wales) that was constructed as part of the same Austroads PMB trial project (Austroads 2013c). The sample was obtained at the ‘as delivered’ stage. This bitumen sample had a much lower durability test result (6.8 days) than the sample of Coober Pedy C170 bitumen (12.5 days) (Austroads 2013c). Testing of two bitumen of very different durability (in terms of the existing durability test) using the new durability test (the subject of this report) was considered worthwhile as it would determine whether the samples would be ranked similarly/differently by the two tests.

The ‘ARRB 6% SBS’ sample was manufactured at the ARRB laboratory by blending a mixture containing 85% w/w C170 bitumen, 6% w/w SBS polymer and 9% w/w of a commercial polymer combining oil at 185 ± 5 °C using a Silverson high shear laboratory mixer. This binder was not used for any of the trial sites, but was included in this study to investigate the property changes that occurred when a very high polymer content elastomeric PMB was PAV aged. As the polymer type and content of commercial PMBs listed in Table 3.1 were unknown, it was thought useful to include a binder sample with known polymer type and content as a reference.

It is noted in Table 3.1 that SAMI S20E SS binder has two types of samples (i.e. denoted as ‘as delivered’ and ‘as manufactured’). As noted above, samples were obtained during the Coober Pedy trial at two stages of product delivery in order to determine if PMB properties changed during transport to the trial site. ‘As manufactured’ and ‘as delivered’ samples of the SAMI S20E SS binder were subjected to PAV ageing in this study in order to observe whether changes in PMB properties during transport affected binder properties on PAV ageing.

The binder samples listed in Table 3.1 were subjected to the two different PAV ageing regimes as introduced in the next section, so that each binder type would have a set of three differently treated samples (i.e. 0 hours (unaged samples), 30 hours and 72 hours of PAV ageing), respectively. These binder samples were then characterised by rheological tests (i.e. DSR and extensiometer CTOD tests) and chemical tests (i.e. Fourier transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC) tests) so that the changes in binder properties on PAV ageing could be investigated. The results obtained during these studies are described in the following sections.



4. PAV Ageing Treatment Method

4.1 PAV Ageing Regime for the New Durability Test The PAV test was developed during the Strategic Highway Research Program (SHRP) to simulate long-term, oxidative ageing of bituminous binders in the field (Kennedy & Harrigan 1990). The SHRP PAV procedure (AASHTO R28-12:2012) entails ageing 50 g of bitumen in a 140 mm diameter pan (to give a binder film thickness of 3.2 mm) in a heated vessel (Figure 4.1), which is pressurised with air to 2.1 MPa. Binder samples are heated to between 90 and 110 °C for 20 hours during the treatment.

Figure 4.1: Schematic of the PAV test system

Source: AASHTO R28-12:2012.

The PAV test procedure adopted for the new durability test was based on the SHRP PAV procedure but with some variations made, as follows:

binder film thickness = 1 mm

ageing temperature = 100 °C

ageing duration = 72 hours

RTFO ageing regime is not applied to binder samples prior to the PAV ageing treatment.



These variations were made during Stage 1 of the work associated with this project (refer to Section 1.3), which investigated the PAV treatment conditions that would produce an ageing level similar to what the Australian durability test (AS 2341.13-1997) would produce. It was found during Stage 1 of work that the SHRP PAV ageing procedure was not severe enough to age binders to the same level as the Australian durability test and, therefore, the above variations (e.g. longer treatment duration and thinner film thickness) were made to increase the level of binder ageing (Austroads 2013a).

4.2 Shorter-term PAV Ageing Regime As part of the post-ageing characterisation study conducted during the current year of the project, a shorter period PAV ageing treatment was used in addition to the full 72 hours ageing regime described in the previous section. Including this extra ageing regime in the experimental program was needed for the following reasons:

Testing of binders when untreated (i.e. 0 hours of ageing), short-term treated (e.g. 30 hours of ageing) and then fully treated (i.e. 72 hours of ageing) provides information about how binders age with PAV treatment time.

For the field validation study proposed in the third year of the project, binders need to be aged in the laboratory to a level similar to the ageing level of the binders placed at the Coober Pedy trial site.

The Coober Pedy trial site that will be used for field validation purposes in the third year of the project was constructed in November 2011 (refer to Section 3). It is expected that the binders placed at the trial site will have been in service for about three years when the field validation study is conducted during 2014–15 (refer to Section 1.4.1). The full PAV treatment duration of 72 hours in the laboratory is equivalent to about 9 to 10 years of ageing in the field (depending on the binder durability and the location of the road). This is a much larger degree of binder ageing than would be expected at the Coober Pedy trial site after three years of service. It was therefore considered sensible to include a ‘shorter-term’ PAV regime in the experimental program in order to address the two issues discussed above.

The shorter-term PAV treatment time was determined using a seal-life prediction model described in Austroads (2005). This model was developed based on a comprehensive series of nationwide field experiments carried out in Australia in the 1980s (Oliver 1984). The model consists of two parts: one part determines the rate of hardening of binder in a sprayed seal based on the location the seal was placed (i.e. the viscosity of the binder as a function of the time since the seal was constructed), while the other part determines the viscosity of the binder when the seal will fail. The two parts of the model are then combined to predict the life expectancy of a seal surfacing.

Only the first part of the model was needed for the calculation of a shorter PAV ageing time, which would show a similar degree of ageing to three years of service on the road. The results obtained for the sample of C170 bitumen, which was studied during the previous year of the project (Austroads 2013a), were used as inputs into the model.

The first step in the determination of the shorter-term PAV treatment time was to construct a binder hardening curve using the model to determine how a C170 bitumen would be expected to harden over time at the Coober Pedy trial site. Table 4.1 presents the parameters used in the model to simulate the expected degree of binder hardening at Coober Pedy. The binder hardening curve is presented in Figure 4.2.



Table 4.1: Parameters used for simulation of the hardening of C170 bitumen placed at the Coober Pedy site

Model parameter Values Reference

Durability of bitumen (days) 9 Austroads (2013a)

Annual mean maximum temperature (Tmax) in Coober Pedy (°C) 27.8 Bureau of Meteorology (2014)

Annual mean minimum temperature (Tmin) in Coober Pedy (°C) 13.7

Seal size used in the Coober Pedy trial site (mm) 14 Austroads (2013c)

Figure 4.2: Simulated binder hardening of the C170 bitumen in the Coober Pedy site

Figure 4.2 demonstrates that a C170 binder placed at the Coober Pedy site would be expected to have a viscosity of about 4.9 log Pa.s (when measured using the Shell sliding plate micro viscometer at 45 °C according to AS 2341.5-1997 (after three years of service).

The next step in the determination of the shorter-term PAV treatment time was to construct a binder hardening curve, which related the viscosity of a binder at 45 °C to the time of PAV treatment. Studies of a sample of C170 bitumen during the previous year of the project (Austroads 2013a) investigated the effects of PAV treatment time on the viscosity at 45 °C of the binder (as measured using the Shell sliding plate viscometer). The results obtained for this binder are shown in Figure 4.3.

Figure 4.3 shows that a viscosity of 4.9 log Pa.s (which corresponds to that expected after three years of service (Figure 4.2)) would be equivalent to about 32 hours of ageing in the PAV. This was rounded down to 30 hours and was used as the treatment duration of the shorter-term PAV ageing regime. Other PAV testing conditions remained identical to the full 72 hours PAV ageing regime.

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

0 1 2 3 4 5 6 7 8 9 10

Bin

der v

isco

sity

(log

Pa.

s at

45 °C

)

Years since construction

Simulated hardening curve for C170 bitumen (durability 9 days) using the binder hardening model.

A viscosity of 4.9 log Pa.s is expected after 3 years in service (according to the binder hardening model)



Figure 4.3: Binder hardening of C170 bitumen during laboratory PAV treatment (up to 96 hours)

Source: Based on Austroads (2013a).

y = -0.0001x2 + 0.0444x + 3.6116R² = 0.9958

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

0 10 20 30 40 50 60 70 80 90 100

Visc

osity

at 4

5 °C

(log

Pa.

s)

PAV ageing time (hours)

Hardening of C170 bitumen (durability 9 days) measured during PAV treatment.

PAV ageing of 32 hours yielded a binder viscosity at 45 °C of 4.9 log Pa.s.This is equivelent to 3 years of service on the road in service (according to the binder hardening model).



5. DSR Flow Tests: Test Procedure and Derived Test Parameters

5.1 Preparation of Samples for DSR testing Binder samples obtained after different periods of PAV treatment were prepared for characterisation by DSR using a method that was based on the procedure described in AASHTO T315-12:2012. This procedure is not particularly more complex or time-consuming than other binder tests currently used in Australia. The mass of sample required for a test was no more than 2 g.

AASHTO T315-12:2012 specifies DSR spindle pre-heating temperatures between 34 to 46 °C for sample mounting. Due to the relative hardness of the aged binders tested, higher sample mounting temperatures were used depending on the type of material tested. Table 5.1 lists the temperatures used in this study for different types of binders.

Table 5.1: Sample mounting temperature used for DSR flow tests

Binder sample type Mounting temperature (°C)

72 hours PAV aged bitumens and PMBs 70

Unaged or 30 hours PAV aged PMBs 60

30 hours PAV aged bitumens 50

Unaged bitumens 45

5.2 DSR Test Conditions Binder samples were tested using the DSR in flow mode, using the following conditions:

binder film thickness = 3 mm

binder sample diameter = 8 mm

test temperature = 15 °C

target shear rate = 0.0075 s-1

maximum shear strain = 10.

All binder samples in this study were subjected to at least duplicate DSR flow tests. Appendix A includes information about the number of times each specific binder sample was tested.

DSR samples are normally prepared so that there is a slight bulge in the middle section of a sample. This method of sample mounting is not desired during DSR flow tests as it results in slightly higher stresses in the top and bottom sections of a sample than in the middle section of a sample. This variation in stress is the result of differences in the cross-sectional area of the sample at different points. Samples subjected to DSR flow tests were prepared so that they did not have a bulge; therefore, the cross-sectional area in all parts of each sample was nominally the same.

The typical appearance of a distressed binder sample after a DSR flow test is shown in Figure 5.1. As can be seen from the figure, binder samples were severely sheared during testing.



Figure 5.1: Typical appearance of a distressed sample after a DSR flow test

5.3 Test Parameters Obtained from DSR Flow Tests DSR flow tests yield a stress-strain curve for each tested binder. A number of parameters derived from the stress-strain curve were considered as promising parameters to rank the low temperature cracking resistance of the binders studied. These are discussed below.

Yield Energy 5.3.1As noted in Section 2.3, Johnson, Wen and Bahia (2009) compared the results of DSR flow tests with cumulative crack data obtained in a full-scale ALF tester and found an excellent correlation between the yield energy values determined from DSR flow tests and ALF cracking length. These researchers calculated yield energy values by determining the area under the DSR flow test stress-strain curve, from zero strain up to the strain where maximum stress was observed. An illustration of how Johnson, Wen and Bahia (2009) calculated yield stress values is shown in Figure 5.2. In the case of the binder shown in Figure 5.2 (72 hours PAV aged Coober Pedy C170 bitumen), the yield energy value was calculated to be 773 kPa. This result corresponds to the area under the curve, up to a strain of 1.47.

Determination of yield energy values by the method of Johnson, Wen and Bahia (2009), however, requires that a binder shows a distinct maximum in its stress-strain curve, which did not occur for the majority of binders tested during this study. Figure 5.3 shows an example of one binder where a maximum in the stress-strain curve did not occur. As many of the binders studied did not show distinct maxima in their stress-strain curves, yield energy values were also calculated up to binder strains of 1, 2, 3 and 10 strain. Figure 5.3 shows an example of how the yield energy value was calculated using the results obtained, up to a binder strain of two. Studies by Johnson, Wen and Bahia (2009) and Jimenez, Recasens and Aldape (2003) have indicated that the area under the stress-strain curve (up to strains beyond the maximum stress peak) may also be useful in ranking the crack resistance of binders at low temperatures.



Figure 5.2: Example of a yield energy calculation obtained from a DSR flow test result (72 hours PAV aged Coober Pedy C170 bitumen)

Figure 5.3: Example of a yield energy calculation of a binder that did not show a distinct maximum in the stress-strain curve

0

100

200

300

400

500

600

700

0 1 2 3 4 5 6 7 8 9 10

Shea

r str

ess (

kPa)

Shear strain

Yield energy: area under the stress-strain curve up to the strain at the peak stress

0

10

20

30

40

50

60

70

80

0 1 2 3 4 5 6 7 8 9 10

Shea

r str

ess (

kPa)

Shear strain

Yield energy calculated up to a defined strain of 2, since peak stress is not evident for this binder sample.



Stress Ratio 5.3.2From the stress-strain curve obtained by conducting a DSR flow test, it was also thought that the stress ratio between the stress value recorded at small strains (e.g. strain of 1) and the stress value recorded at larger strains (e.g. strain of 10) could provide useful information in terms of binder crack resistance. This proposal was made based on the studies conducted using conventional extensiometer tests, which were reported previously (Austroads 2013b). This is briefly discussed below.

Typical extensiometer test results for PMB and bitumen samples are presented in Figure 5.4.

Figure 5.4: Typical extensiometer force-displacement curves

Note: C600 = Class 600 bitumen, PBDA = PMB containing polybutadiene, 6% SBS = PMB containing 6% styrene butadiene styrene polymer, EMA = PMB containing ethylene methacrylate copolymer. Source: Oliver (2000).

Among a number of parameters that can be calculated from conventional extensiometer force-displacement curves (e.g. toughness, peak force), the force-ratio between a force value recorded at small displacements (e.g. at the leftmost peak on a force-displacement curve) and another force value recorded towards large displacements (e.g. at the rightmost peak on the same force-displacement curve) was found to be related to binder crack resistance in a number of Australian studies conducted in the laboratory (Oliver 2000, Tredrea 2006, Wilson et al. 2009), as well as in the field (Austroads 2013b). Specific calculation procedures adopted in each of these studies were slightly different, but the principle was essentially the same in that the force values recorded at both ends of a force-displacement curve (when the binder sample was subjected to small and large elongations, respectively) were the main factors used in force-ratio calculations.

The DSR flow test is different to the extensiometer test, as the binder sample is sheared rather than elongated, but both tests commonly subject binder samples to a large strain (e.g. a strain of 10) under a monotonic mode of loading and record the resistant force/stress of the binder sample during loading. It was thought that the force-ratio calculation methodology used for the extensiometer test (which showed promising results in the laboratory and in the field) could be adopted in terms of the analysis of DSR flow test results, but using the shear stress values (instead of force values) and shear strain values (instead of displacement values).

0

50

100

150

0 50 100 150 200 250

Displacement (mm)

Forc

e (N

) 6%SBS

PBDA

EMA

C600



The stress ratio of the DSR flow test was calculated by dividing the stress value recorded at the maximum strain of 10, by a peak stress value recorded towards small strains (if a binder sample presented a maximum peak in the stress-strain curve, such as in Figure 5.5). For the case of the binder sample presented in the graph (72 hours PAV aged Coober Pedy C170 bitumen), the stress ratio was calculated to be 0.78.

Figure 5.5: Example of stress ratio calculation from a DSR flow test result (72 hours PAV aged Coober Pedy C170 bitumen)

As in the case of yield energy calculations (Section 5.3.1), most of the DSR flow test data did not show a distinct maximum peak at small strains, as shown in Figure 5.6. In such cases, stress ratio values were calculated at a number of defined small strains (i.e. strains of 1, 2 or 3) instead of the strain at the peak stress value. In the case of the binder sample shown in Figure 5.6 (unaged S20E), the stress ratio calculated using the stress at a strain of two was calculated to be 1.48.

Stress ratio results were determined for all binders studied using strains of 1, 2 and 3 strain. Stress ratio results were also calculated using the stress observed at the peak of the stress-strain curve in the cases where binders showed a distinct maximum towards lower strains in their stress-strain curves.

0

100

200

300

400

500

600

700

0 1 2 3 4 5 6 7 8 9 10

Shea

r str

ess (

kPa)

Shear strain

Peak stress

Stress at the maximum strain of 10

Stress ratio = 0.78according to the two stress values(= 510 kPa / 650 kPa).



Figure 5.6: Example of stress ratio calculation from a DSR flow test result where a stress peak towards small strains is not evident (unaged S20E)

0

10

20

30

40

50

60

70

80

0 1 2 3 4 5 6 7 8 9 10

Shea

r str

ess (

kPa)

Shear strain

Stress at a defined strain of 2, since peak stress is not evident for this binder sample.

Stress at the maximum strain of 10

Stress ratio = 1.48according to the two stress values(= 68 kPa / 46 kPa)



6. DSR Flow Mode Tests: Results and Analysis

The binder samples listed in Table 3.1 were assessed using the DSR flow test after they had been PAV aged for various periods of time. Each sample was subjected to at least duplicate DSR flow tests. Test results obtained during individual DSR flow tests and information on test variability (i.e. standard deviation and the coefficient of variance) are provided in Appendix A. Only the average values of yield energy and stress ratio obtained in repeated DSR flow tests have been included in Table 6.1 and Table 6.2, respectively, so that the trends in test properties with PAV ageing time can be easily observed.

6.1 Yield Energy Values Table 6.1 shows the yield energy values that were calculated for each of the binders studied after different periods of PAV ageing. The yield energy values were calculated by determining the area under the stress-strain curve between zero strain and various different strain levels (i.e. 1, 2, 3, and 10 strain). In the case of binders that showed a distinct maximum peak in their stress-strain curves, the yield energy values calculated using the method of Johnson, Wen and Bahia (2009) have been shown in Table 6.1. For all binders studied, the yield energy values determined at each set strain level increased as the PAV ageing time was increased.

Table 6.1: Yield energy values

Binder PAV ageing time

(hours)

Yield energy (kPa) 1 strain 2 strain 3 strain 10 strain Strain at

peak

Coober Pedy C170 bitumen

0 17 36 55 179 –

30 283 651 1020 3357 –

72 516 1155 1782 5643 840

Cooma C170 bitumen

0 23 48 73 243 –

30 363 820 1272 4095 677

72 661 1437 2180 6681 723

S10E

0 9 21 34 163 –

30 138 335 555 2394 –

72 331 764 1206 4047 –

S15E

0 17 21 24 49 –

30 226 276 304 294 –

72 709 741 718 555 –

S20E 0 33 77 125 521 –

30 300 660 1017 3846 –

72 491 1043 1589 5480 –

S35E

0 7 16 25 96 –

30 87 207 338 1406 –

72 238 551 867 2918 –

S45R

0 15 36 59 286 –

30 129 299 481 1976 –

72 242 551 862 2870 –

Shell S5E

0 20 43 68 250 –

30 243 545 848 3047 –

72 421 933 1440 4856 –



Binder PAV ageing time

(hours)

Yield energy (kPa) 1 strain 2 strain 3 strain 10 strain Strain at

peak

SAMI S20E SS as delivered

0 17 41 67 333 –

30 149 354 583 2673 –

72 320 723 1126 3624 –

SAMI S20E SS as manufactured

0 20 47 76 363 –

30 165 383 618 2699 –

72 361 789 1211 3785 –

ARRB 6% SBS

0 15 37 62 349 –

30 129 297 466 1598 –

72 324 703 1078 3144 –

Figure 6.1 shows plots of the yield energy values determined for strains up to two strain that were obtained for the two samples of C170 bitumen and samples of S10E, S20E and S35E grade PMBs. These results are representative of those observed when different strain levels were used to calculate yield energy values. The results obtained for the other PMBs studied have not been shown in the figure for clarity. The results for the PMBs that are not shown in the figure were found to lie between the curves obtained for S35E and S10E.

Figure 6.1: Varying yield energy values (at 2 strain) against varying PAV ageing time

The results shown in Figure 6.1 illustrate that all yield energy values increased as the PAV ageing time was increased. The two bitumen samples (Coober Pedy C170 bitumen and Cooma C170 bitumen) had higher rates of increase than the PMB samples. The sample of C170 bitumen, which had a lower durability test result (Cooma C170 bitumen), showed a greater increase in yield energy values with PAV ageing time than the bitumen sample which displayed a high durability test result (Coober Pedy C170 bitumen). Among the PMB samples, the S35E binder showed the lowest rate of yield energy increase with PAV ageing time, while the S20E binder displayed the highest rate of yield energy increase with PAV ageing time. Even though all binders showed an increase in yield energy values with PAV ageing time, it is not currently known whether these changes reflect differences in the low temperature cracking performance of the binders.

0

200

400

600

800

1000

1200

1400

1600

0 10 20 30 40 50 60 70 80

Yiel

d en

ergy

(kPa

)



Cooma C170 bitumen

S10E

S20E

S35E



6.2 Stress Ratio Results Table 6.2 shows the stress ratio results that were calculated for each of the binders studied after different periods of PAV ageing. Stress ratio results were predominantly determined by dividing the stress observed for each binder at 10 strain by the stress observed for the same binder at various different strain values (i.e. 1, 2 and 3 strain). In the cases where binders showed a distinct maximum peak in the stress-strain curve obtained from DSR flow tests, stress ratio results were also calculated by dividing the stress obtained at 10 strain by the stress recorded at the maximum peak of the stress-strain curve. For all binders studied, the stress ratio results determined using set strain values decreased as the PAV ageing time was increased.

Table 6.2: Stress ratio results

Binder PAV ageing time (hours)

Stress ratio 1 strain 2 strain 3 strain Strain at peak

Coober Pedy C170 bitumen 0 0.93 0.90 0.92 – 30 0.88 0.85 0.91 – 72 0.81 0.80 0.83 0.81

Cooma C170 bitumen 0 0.94 0.92 0.93 – 30 0.85 0.83 0.86 0.82 72 0.77 0.78 0.83 0.77

S10E 0 2.13 1.87 1.69 – 30 1.51 1.30 1.19 – 72 0.90 0.84 0.85 –

S15E 0 2.81 2.37 2.07 – 30 1.30 1.06 0.97 – 72 0.78 0.75 0.77 –

S20E 0 1.68 1.50 1.42 – 30 1.32 1.31 1.31 – 72 1.01 1.02 1.03 –

S35E 0 1.30 1.18 1.14 – 30 1.47 1.30 1.21 – 72 0.92 0.86 0.87 –

S45R 0 2.10 1.80 1.62 – 30 1.46 1.31 1.25 – 72 0.89 0.85 0.86 –

Shell S5E 0 1.21 1.13 1.11 – 30 1.10 1.10 1.10 – 72 0.90 0.91 0.91 –

SAMI S20E SS as delivered 0 2.42 2.10 1.94 – 30 1.78 1.54 1.41 – 72 0.83 0.80 0.82 –

SAMI S20E SS as manufactured 0 2.19 1.91 1.78 – 30 1.66 1.49 1.40 – 72 0.77 0.77 0.80 –

ARRB 6% SBS 0 2.82 2.27 1.95 – 30 1.05 0.99 1.02 – 72 0.52 0.52 0.53 –



Figure 6.2 shows plots of the stress ratio results which were determined using the stress values at 2 strain for the two samples of C170 bitumen and three representative PMBs. The results shown in the figure are representative of those observed when the stress at different set strain levels was used to calculate stress ratio results. The results for the PMBs that are not shown in the figure were found to generally lie between the curves obtained for the two samples of C170 bitumen and the curve obtained for the SAMI S20E SS ‘as delivered’ binder.

Figure 6.2: Changes in stress ratio results (at 2 strain) with PAV ageing time

It is evident from Figure 6.2 that all stress ratio results decreased as the PAV ageing time was increased. It is also noted that the two bitumen samples (Coober Pedy C170 bitumen and Cooma C170 bitumen) did not show marked changes in stress ratio results with PAV ageing time compared with the changes observed for the PMB samples. The ARRB 6% SBS binder showed the highest rate of stress ratio reduction with PAV ageing time and had the lowest stress ratio result of all the binders studied after 72 hours of PAV ageing.

It is currently not known whether these changes reflect differences in the low temperature cracking performance of the binders, but an assumption could be made according to the studies that investigated the extensiometer force-ratio parameter (Austroads 2013b, Oliver 2000, Tredrea 2006, Wilson et al. 2009). These studies found that binders with high force-ratio values were more crack resistant. If the DSR stress ratio parameter trialled in this study would be able to rank binders in the same way as the extensiometer force-ratio parameter, it is likely that crack-resistance of binders would be decreased on PAV ageing, since all binders showed a decrease in stress ratio results with increased ageing time (as seen in Figure 6.2).

6.3 Summary The results of the DSR flow tests indicated that the yield energy values obtained for the binders increased, and the stress ratio results decreased, with increased PAV ageing time. The changes in these test parameters with PAV ageing time appeared to be dependent on the type of binder studied. It is uncertain at this stage as to whether yield energy values or stress ratio results are more appropriate for characterising the properties of PAV aged binders. The results obtained from DSR flow tests, however, will provide a database of results that can be used in the field validation study, which is proposed in the third year of this project.

0.5

1.0

1.5

2.0

2.5

0 10 20 30 40 50 60 70 80

Stre

ss ra

tio



Cooma C170 bitumen

S15E


ARRB 6% SBS



7. Extensiometer CTOD Tests: Test Procedure and Issues

The CTOD test method was briefly introduced in Section 2.4 and was found to be promising for predicting the fatigue performance of binders in the field. However, this force ductilometer-based method was not selected during the test method review conducted during 2012–13 (Austroads 2013b) as this test requires a relatively large amount of sample compared with the amount that can be produced during a PAV treatment. Preliminary experiments conducted during 2012–13 indicated that CTOD type tests could be performed using the Australian extensiometer. Use of the extensiometer to conduct CTOD tests involved modifying the specimen geometry of the extensiometer test so that samples could be produced with various sized notches. The main advantages of using the extensiometer to conduct CTOD tests is that the equipment is available in Australia and tests only require a relatively small amount of sample (about 3 g per specimen).

7.1 Sample Preparation Standard extensiometer sample moulds (which are used to fabricate rectangular beam specimens in the conventional procedure, refer to Figure 2.3) were modified as shown in Figure 7.1. The CTOD test method (Ministry of Transportation 2001) requires a set of three specimens with varying ligament sizes. The extensiometer moulds were manufactured with nominal ligament sizes (i.e. gaps between the two notches in each mould) of 3, 5 and 7 mm, respectively. After manufacture, the actual ligament sizes in the moulds were measured to be 3.2, 4.6 and 6.5 mm. These measured ligament sizes were used during the data analysis associated with extensiometer CTOD tests.

Figure 7.1: Photos of extensiometer CTOD specimen moulds and a notched specimen ready for testing

Source: Austroads (2013b).

Notched specimens were fabricated by pouring hot binders into each of the moulds, allowing the binders to cool, and then mounting the binder specimens in the extensiometer test frame (Figure 7.1). The specimen fabrication process was identical to that used during conventional extensiometer tests (Austroads AGPT/T124), except that an SBS solution was applied to the metal supports for better adhesion, as described in Austroads (2013b). The sample preparation method was not particularly more difficult than the conventional method, but more careful handling of the specimens was required (particularly when mounting the specimens on the test frame) since the notched area of the specimens was fragile.



7.2 Test Procedure and Data Interpretation Extensiometer CTOD testing was conducted using the following conditions:

test temperature of 15 °C

displacement rate of 0.1 mm/s.

These test conditions were determined based on preliminary experiments reported in Austroads (2013b).

Figure 7.2 shows a photograph of the typical appearance of a set of three CTOD specimens (which had various ligament sizes) after testing. In order for CTOD tests to be performed effectively, each of the three specimens needs to break at the ligament during a test.

All extensiometer CTOD tests conducted in this study were performed in duplicate (i.e. two specimens of each ligament size were tested, giving a total of six individual tests for each binder sample).

Figure 7.2: Example of a set of extensiometer CTOD specimens after testing (72 hours PAV aged S20E)

Figure 7.3 shows a typical set of extensiometer CTOD test force-displacement curves which were obtained using specimens of the same binder that had three different ligament sizes. In each case, the force recorded from the binder initially increased at small sample displacements, and then decreased to zero (which corresponded to the point when each of the specimens broke). Specimens with smaller ligament sizes generally showed lower peak maxima in their force-displacement curves and broke at smaller displacements compared with specimens produced with larger ligament sizes.



Figure 7.3: Different force-displacement curves representing a set of three specimens of varying ligament size (72 hours PAV aged S20E)

CTOD test parameters were calculated using the method described in the conventional CTOD test method (Ministry of Transportation 2001). A description of the method is described below:

1. Individual force-displacement curves were initially used to calculate the work of fracture (i.e. the area under the curve divided by the ligament cross-sectional area of the specimen) in units of kJ/m2.

2. The individual work of fracture values were then plotted against the corresponding ligament lengths for the three tested ligament sizes (i.e. 3.2, 4.6 and 6.5 mm), as shown in Figure 7.4.

3. All data points obtained for a particular sample were then fitted to a linear function. The intercept of the linear fit was taken to be the ‘essential work of fracture’ (EWF) (Figure 7.4).

The CTOD parameter was then calculated by dividing the EWF value by the average stress recorded for the smallest ligament specimens (i.e. the specimens with a 3.2 mm ligament). The stress was calculated from the peak force divided by the ligament cross-sectional area.

0

5

10

15

20

25

30

35

40

0 10 20 30 40 50 60

Forc

e (N

)

Displacement (mm)

6.5 mm ligament specimen





Figure 7.4: Extrapolation to determine the essential work of fracture (EWF) using the specific work of fracture data obtained for a particular sample (72 hours PAV aged S20E)

In the case of the 72 hours PAV aged S20E binder shown in Figure 7.4, the CTOD parameter was calculated to be 1.49 mm.

7.3 Extensiometer CTOD Test: Issues and Limitations While conducting the extensiometer CTOD test to assess PAV aged binder samples, it was noted that some binders yielded negative EWF values (and therefore negative CTOD parameters) when the test data was analysed according to the procedure described above. An example of a binder that displayed this behaviour (SAMI S20E SS ‘as delivered’ after 30 hours of PAV treatment) is shown in Figure 7.5. This binder had an EWF value of –2.382 and a CTOD parameter of –9.89 mm.

EWF and CTOD by definition (i.e. energy and length) cannot theoretically be negative numbers. This suggested that there were issues with the analysis.

The most likely reason for binders showing negative EWF values and CTOD parameters is due to the extrapolation process is used to calculate EWF values (i.e. Step 3 in the CTOD calculation procedure described above). From Figure 7.5, it is clear that the EWF value (which is the intercept of the linear fit) is determined based on the line of best fit between data points obtained at ligament lengths between 3.2 and 6.5 mm. Any experimental variation in the experimental data points could markedly change the slope, and so the intercept, of the linear fit. It is therefore likely that the negative EWF values and CTOD parameters observed for some binders are the result of linear fitting issues associated with conducting experiments at ligament lengths between 3.2 and 6.5 mm.

y = 2.324x + 1.520R² = 0.956

0

2

4

6

8

10

12

14

16

18

20

0 1 2 3 4 5 6 7

Spec

ific

wor

k of

frac

ture

(kJ/

m2 )

Ligament length (mm)

Essential work of fracture



Figure 7.5: Example of test data that provides a negative EWF value (30 hours PAV aged SAMI S20E SS ‘as delivered’)

The main way to improve the extrapolation process involved in extensiometer CTOD tests would be to conduct experiments using specimens with smaller minimum ligament sizes (e.g. 1 mm, instead of 3.2 mm), as this would reduce the amount of extrapolation required during the analysis stage of the tests. As specimens with ligament sizes of 3.2 mm were found to be quite fragile during normal laboratory handling, it is unlikely that specimens with smaller ligament sizes could be effectively produced and tested (as they would be more inclined to break during preparation or mounting in the extensiometer). Another method that could be used to improve the extrapolation process would be to use a function other than a linear function to fit the experimental data. The best function to use is currently not known, and the EWF values and CTOD parameters obtained from extensiometer CTOD tests would be very dependent on the type of function selected.

Extensiometer CTOD tests were only performed on a limited number of binders due to the issues with negative EWF values and CTOD parameters, which are described above. Due to the issues with the calculation of CTOD parameters, the extensiometer CTOD test in its current form does not appear to be able to effectively characterise the properties of PAV treated binders.

It was agreed by Austroads BSWG (during the meeting in February 2014) that the resources initially allocated for extensiometer CTOD tests would be used to conduct the chemical property investigations, which are described in Section 8 and Section 9.

y = 2.940x - 2.328R² = 0.978

-4

-2

0

2

4

6

8

10

12

14

16

18

20

0 1 2 3 4 5 6 7

Spec

ific

wor

k of

frac

ture

(kJ/

m2 )

Ligament length (mm)

EWF = − 2.328



8. Chemical Property Investigations

8.1 Introduction Chemical property investigations were conducted during this study in order to obtain some fundamental information about the chemical processes that occurred when the binders were PAV aged. Each of the binders studied were characterised by Fourier transform spectroscopy (FTIR) and gel permeation chromatography (GPC) in order to obtain information about the changes in binder chemical composition (via FTIR), and changes in the size of the chemical components in the binders (via GPC), which occurred when the materials were PAV aged. It was also thought that the results of chemical characterisation tests could be used during the field validation study (which is proposed in the third year of the project) by comparing the chemical changes that occurred when binders were PAV aged with those that occurred when the same binders were aged on the road.

Fourier Transform Infrared (FTIR) Spectroscopy 8.1.1FTIR spectroscopy is a technique which can be used to obtain information about the chemical composition of a material, as it provides data on the type and number of chemical groups that are present in a sample (Silverstein, Bassler & Morrill 1981). FTIR measurements give information about the chemical species present in a sample because different chemical groups absorb different wavelengths (equivalent to colours) of infrared light. When a chemical group absorbs infrared light, the chemical bonds in the group will vibrate in a specific way. Due to this, the different spectral peaks in an FTIR spectrum are referred as chemical group stretches, bends and wags.

An FTIR measurement involves shining infrared light through a sample and monitoring the changes in light intensity as a function of the wavelength (colour) of the light. If a particular chemical species is present in a sample, then the intensity of infrared light will be reduced at the wavelength at which the chemical group absorbs. The amount of light absorbed by the sample is generally expressed in terms of the absorbance of the material. Measurement of absorbance is used as the infrared absorbance of a chemical species and is proportional to its concentration in the material (Günzler & Gremlich 2002). The absorbance of a material at a particular wavelength is calculated using Equation 1 (Stuart 2004):

A = –log10(I/I0) 1

where

A = Absorbance of the material

I = Intensity of light when the sample is present

I0 = Intensity of light when the sample is absent

FTIR spectra are typically plotted with absorbance on the y-axis, and wavenumber (i.e. the number of wavelengths of infrared light that would fit into 1 cm (in cm-1)) on the x-axis.

Gel Permeation Chromatography (GPC) 8.1.2GPC is an experimental technique that is used to separate the chemical components in a material based on molecular size. During a GPC experiment, a sample of material is initially dissolved in a solvent to produce a solution. This solution is then injected into a flowing stream of the same solvent (the mobile phase), which passes through one or more columns that each contain a packed bed of porous polymer beads which contain pores of various sizes.



Small molecules take longer to pass through a bed of polymer beads, as they can travel through the pores in the beads and so traverse a greater distance before they emerge from a column. Large molecules take a shorter time to pass through a bed of polymer beads, as they cannot travel through the pores in the beads and so they traverse a shorter distance before they emerge from a column. A detector (such as a refractive index detector) is used to monitor the molecules that pass through the GPC column(s) at different times. The results are typically presented as plots of solution refractive index changes (due to the presence of different chemical species) versus the time the mobile phase had passed through the system (i.e. the retention time which is related to the size of the molecules).

8.2 Test Procedures

FTIR Spectroscopy 8.2.1FTIR spectroscopy measurements were conducted by initially heating binder samples in an oven until they were fluid enough to stir and pour. Once the binders were sufficiently fluid, they were stirred thoroughly with a spatula and a small drop was applied to a piece of paper. After the binders had cooled, each sample was analysed using a Perkin Elmer Frontier FTIR spectrometer that included a universal attenuated total reflectance (ATR) sampling accessory. The measurement process involved placing the paper so that the drop of each binder was in contact with the reflective surface of a 1 mm diameter zinc selenide crystal, which was part of the sampling accessory. After samples were positioned, an FTIR spectrum was obtained. The FTIR spectra shown in this report were obtained by averaging the results of 10 spectral scans on each sample using an instrument resolution of 4 cm-1.

Gel Permeation Chromatography (GPC) 8.2.2Gel permeation chromatography (GPC) measurements were performed by the Surface and Chemical Analysis Network (SCAN) laboratory at the University of Melbourne using a Shimadzu GPC system fitted with a Wyatt Optilab EOS interferometric refractometer, which measured the change in refractive index of the sample using red (690 nm) light. The GPC system contained three Phenomenex phenogel columns, which had effective pore sizes of 0.05, 1 and 100 µm. The solvent tetrahydrofuran (THF) was used as the mobile phase during the experiments. The column temperature was 30 °C, and the mobile phase passed through the GPC system at a flow rate of 1 millilitre per minute.

GPC measurements were conducted by initially dissolving samples in THF at a concentration of 10 g/litre. Experiments were conducted by injecting 50 µL of each of the prepared solutions into the GPC system.

The raw results obtained from GPC measurements give plots of changes in refractive index due to the presence of different chemical components, against the retention time (i.e. the time the mobile phase has flowed through the system). The GPC measurements, which are included in this report, were conducted over a number of days. A polystyrene standard (from Agilent Technologies Australia Pty Ltd.), which contained a mixture of polystyrene polymers of known molecular weights (770, 5900, 51 100, and 371 000 g/mol), was run on each day of testing in order to account for experimental/column variations that occurred when samples were run on different days. The retention times shown in this report have been corrected using the retention time results obtained for the polystyrene standard on each day of testing, so that GPC results obtained on different days can be directly compared.



9. FTIR and GPC: Test Results and Analysis

9.1 FTIR Spectroscopy Test Results and Analysis

Spectral Changes on PAV Ageing 9.1.1Figure 9.1 shows the FTIR spectra obtained for the sample of Coober Pedy C170 bitumen after it was subjected to different periods of PAV ageing, as well as assignments for the different chemical species that are responsible for main peaks in the FTIR spectra. Further information about the chemical assignments is included in Appendix B. The spectral assignments included in this report were determined using previously published data for materials, which included general hydrocarbons (Silverstein, Bassler & Morrill 1981), SBS polymers (Munteanu & Vasile 2005) and bitumen samples (Huang 1997).

Figure 9.1: FTIR spectra obtained for a sample of Coober Pedy C170 bitumen after different periods of PAV ageing

The FTIR spectrum obtained for the unaged Coober Pedy C170 bitumen sample (i.e. after 0 hours of PAV treatment) showed peaks associated with saturated hydrocarbons (denoted by the peaks labelled as CH2 stretches; CH3, CH2 bends, CH3 bend and CH2 rock in the figure), aromatic hydrocarbons (denoted by the peak labelled as aromatic C=C stretch in the figure), and oxidised sulphur (i.e. sulphoxide) chemical groups (denoted by the peak labelled as S=O in the figure). On PAV ageing, the intensities of the peaks associated with the sulphoxide chemical groups (at 1031 cm-1) and aromatic carbon chemical groups (at 1600 cm-1) increased. A new peak at 1697 cm-1 also appeared which was due to the presence of oxidised carbon (i.e. carbonyl) groups in the material. The intensity of this peak increased as the PAV treatment time increased. The intensity of infrared light absorption also increased with PAV treatment time in the spectral region between about 1370 and 1050 cm-1. This increase is due to the formation of higher oxidised forms of sulphur, such as sulphonates (i.e. materials with SO3 chemical groups) and sulphates (i.e. materials with SO4 chemical groups) in the material (Huang 1997).



The increases in the carbonyl and oxidised sulphur related peaks in the FTIR spectrum indicate that PAV ageing increased the concentration and types of oxygen-containing chemical groups in the binder. As the intensities of these peaks showed an overall increase with increased PAV ageing time, further PAV ageing appeared to increase the concentration of oxygen-containing chemical groups in the material.

The FTIR spectrum of an unaged sample of Cooma C170 bitumen showed the same series of peaks as those shown in Figure 9.1. The changes in the FTIR spectra observed on PAV ageing also showed the same trends as those observed for the Coober Pedy C170 bitumen sample. The FTIR spectra obtained for the Cooma C170 bitumen sample after different periods of PAV ageing are included in Appendix B. Based on these results, it appears that the chemical changes that occurred in the Cooma C170 bitumen sample on PAV ageing were similar to those which occurred in the Coober Pedy C170 bitumen sample.

Figure 9.2 shows the FTIR spectra obtained for the S20E binder after different periods of PAV ageing, as well as the assignments for the peaks, which are related to the polymer in the PMB and those which changed during PAV ageing. The unaged S20E binder (i.e. after 0 hours of PAV treatment) showed two peaks at wavenumbers of 966 cm-1 and 699 cm-1, in addition to the same series of peaks observed for both C170 bitumen samples prior to PAV ageing. These additional peaks (labelled as PBD C-H wag and PS C-H wag in the figure) are associated with infrared light absorption by the chemical components in the polybutadiene (PBD) and polystyrene (PS) segments of a styrene-butadiene-styrene (SBS) polymer, respectively. The presence of these peaks indicates that the S20E binder contains a type of SBS polymer.

Figure 9.2: FTIR spectra obtained for the S20E binder after different periods of PAV ageing

The changes in the FTIR spectra of the S20E binder on PAV ageing showed similar trends as those observed for the two samples of C170 bitumen studied. PAV ageing again caused an increase in the peaks associated with aromatic carbon and sulphoxide chemical groups. A new peak due to the presence of carbonyl chemical groups also appeared on PAV ageing, which increased when the PAV ageing time was increased. There was also an increase in infrared light absorption in the spectral region between 1370 and 1050 cm-1 on PAV ageing, which can be attributed to the formation of higher oxidised forms of sulphur in the



material. Based on these results, it appeared that the chemical changes that occurred in the S20E binder on PAV ageing were similar to those observed for the two samples of C170 bitumen.

There were no marked changes in the intensities of the two polymer-related peaks in the FTIR spectrum of the S20E binder on PAV ageing. Even though the peak associated with the PBD segments of an SBS polymer (at 966 cm-1 in Figure 9.2) initially appeared to increase with increased PAV treatment time, spectral analysis indicated that this increase was due to changes to the spectral baseline, which were mostly related to changes due to overlap with the nearby sulphoxide group peak at 1031 cm-1 in the graph. If the changes in the spectral baseline were taken into account, there did not appear to be a marked change in the intensity of the PBD-related peak on PAV treatment.

FTIR tests were conducted on all PMBs included in this investigation (Table 3.1), except for samples that contained the S45R binder. FTIR tests were not conducted using samples of the S45R binder, as it was thought that the rubber particles in the crumb rubber binder would be too large to obtain a representative spectrum of the binder using the FTIR spectrometer used in the experiments (which had a spectral measurement window with a diameter of 1 mm).

Of the remaining seven PMBs that were studied by FTIR, all binders, except for the S35E binder, showed the same series of FTIR peaks as shown in Figure 9.2 prior to being aged in the PAV. As these six binders all showed FTIR peaks due to the presence of PBD and PS related chemical components, it appears that each of these materials contain a type of SBS polymer.

All binders that appeared to contain SBS polymers also showed the same overall trends in terms of changes to FTIR spectra on PAV ageing. Based on these results, it appears that similar types of chemical changes were occurring in all PMBs that appeared to contain SBS polymers on PAV ageing. As these binders showed similar behaviour, the results obtained for these materials have not been included in the body of this report. The FTIR spectra obtained for these binders after different periods of PAV ageing are included in Appendix C.

Figure 9.3 shows the FTIR spectra obtained for a sample of S35E binder after different periods of PAV ageing, as well as the assignments for the peaks, which are related to the polymer in the PMB and those which changed during PAV ageing. The FTIR results obtained for the S35E binder have been discussed separately from the other PMBs that were subjected to FTIR tests, as the supplier of this material indicated that it contained a PBD, rather than an SBS polymer (Austroads 2013c). The FTIR spectrum of the S35E binder prior to PAV ageing showed the same series of peaks as shown in Figure 9.2, except that the PS chemical group related peak at 699 cm-1 (i.e. the P-S CH wag peak shown in Figure 9.2) was absent. The peak would be expected to be absent if a PMB contained a PBD polymer.

The changes in the FTIR spectra of the S35E binder after different periods of PAV treatment showed the same trends as those observed for the other binders studied by FTIR. Like the other samples studied, there were increases in the peaks associated with aromatic carbon and sulphoxide chemical groups on PAV ageing. A new peak due to the presence of carbonyl chemical groups also appeared on PAV ageing, and there was an increase in the infrared light absorption in the spectral region between about 1370 and 1050 cm-1, which can be attributed to the presence of higher oxidised forms of sulphur in the material. The intensities of both of these spectral features increased with increasing PAV ageing time. The PBD associated polymer peak at 966 cm-1 also did not appear to change markedly with PAV ageing time when changes in the spectral baseline were taken into account.

Based on the results obtained during FTIR studies, it appears that similar chemical processes occurred in all binders during PAV ageing. PAV ageing caused the appearance of carbonyl group-containing chemical species in the binders and increased the number of sulphur-containing chemical groups which were oxidised to various degrees. PAV ageing also appeared to increase the number of aromatic carbon groups in each of the materials.



Figure 9.3: FTIR spectra obtained for the S35E binder after different periods of PAV ageing

As PAV ageing did not appear to have a marked effect on the FTIR peaks associated with the polymer in the PMBs studied, it did not appear to have a large effect on the types and numbers of polymer-related chemical groups in the PMBs. Since this is the case, and the chemical changes that occurred for the PMBs were similar to those obtained for samples of C170 bitumen, it appears likely that the chemical changes observed for the PMBs during FTIR measurements were predominantly due to changes to the non-polymer components (e.g. the bitumen) in the PMBs.

Quantitative Analysis of Spectral Changes 9.1.2Even though the results described in Section 9.1.1 indicated that similar chemical processes were occurring in all binders studied during PAV ageing, the three spectral peaks which showed the most marked changes during the experiments were analysed in a quantitative way in order to see if there was a variation in the rates of chemical change observed for each of the binders. It was also thought that the results of this quantitative analysis could be used during the field validation study (which is proposed in the third year of the project), as the quantitative changes in specific spectral peaks after different periods of PAV ageing could be compared those to observed for the same binders after approximately three years of binder ageing on the road. This data would provide information about the relationship between the binder ageing time used in laboratory PAV tests and the time a binder used in a sprayed seal has aged on the road.

The changes in the contributions of the spectral peaks with PAV ageing time were quantitatively assessed by comparing the integrated areas under each of the peaks using the software supplied with the FTIR spectrometer. The integrated area of each peak was initially determined by using the software to draw a linear baseline, which joined the points of lowest absorbance of the peak. The area between the peak and the linear baseline was then calculated by the spectrometer software. The integrated area gives a more accurate assessment of the contribution of an FTIR peak than a measurement of the height of the peak at the peak maximum (i.e. at a single wavenumber), as it includes contributions from all parts of the peak rather than just the contribution at a single data point.



Table 9.1 summarises the quantitative contributions of the FTIR peaks associated with carbonyl (C=O), aromatic carbon (C=C) and sulphoxide (S=O) chemical groups for each of the binders studied by FTIR after various periods of PAV ageing. For each chemical group, the contribution of each peak is directly proportional to the concentration of the chemical species in the binder. The constant of proportionality between the integrated area obtained from FTIR measurements and the concentration of the chemical species, however, depends on the specific peak analysed (Stuart 2004).

Table 9.1: Quantitative changes in FTIR spectral peaks during PAV ageing

Binder PAV ageing time (hours)

Integrated area of FTIR peak (arbitrary units) Carbonyl (C=O)

stretch Aromatic (C=C)

stretch Sulfoxide (S=O)

stretch


0 – 0.84 0.40

30 0.33 0.96 1.02

72 0.57 1.04 1.01

Cooma C170 bitumen

0 – 0.78 0.34

30 0.34 0.92 0.92

72 0.57 0.99 0.77

S10E

0 – 0.82 0.29

30 0.28 0.87 0.84

72 0.53 0.95 0.79

S15E

0 – 0.65 0.19

30 0.27 0.82 0.78

72 0.57 0.91 0.69

S20E 0 – 0.75 0.28

30 0.26 0.92 0.79

72 0.47 1.01 0.74

S35E

0 – 0.74 0.25

30 0.32 0.88 0.85

72 0.53 0.98 0.81

Shell S5E

0 – 0.74 0.29

30 0.25 0.91 0.90

72 0.51 1.02 0.79


0 – 0.69 0.28

30 0.31 0.83 0.74

72 0.56 0.91 0.65

SAMI S20E SS as manufactured

0 – 0.75 0.43

30 0.27 0.79 0.70

72 0.55 0.93 0.77

ARRB 6% SBS

0 – 0.73 0.26

30 0.26 0.70 0.84

72 0.54 0.78 0.71



The results shown in Table 9.1 indicate that the rate of increase in carbonyl-containing chemical species with PAV exposure time was essentially the same for all binders subjected to FTIR tests, as the integrated areas of this spectral peak were all within the ranges of 0.30 ± 0.05 and 0.54 ± 0.07 after PAV treatment of 30 and 72 hours, respectively. The rate of increase in aromatic carbon-containing species with PAV treatment time appeared to be dependent on the type of binder studied. If results after PAV exposure times of 0 hours and 72 hours are compared, the ARRB 6% SBS binder showed the lowest rate of increase in aromatic carbon-containing chemical groups with PAV exposure time. The Shell S5E binder showed the highest rate of increase in aromatic carbon-containing chemical groups with PAV exposure time.

Inspection of the results shown in Table 9.1 indicates that there was an increase in the concentration of sulphoxide chemical groups in all binders between PAV treatment times of 0 and 30 hours. The concentration of sulphoxide chemical groups either did not change, or reduced, between PAV treatment times of 30 and 72 hours. It was noted in Section 9.1.1 that PAV ageing increased the concentration of chemical groups in the binders containing higher oxidised forms of sulphur (e.g. sulphonates and sulphates). As this occurred concurrently with the reduction in the number of sulphoxide chemical groups in many of the binders studied, these results suggest that the sulphoxide chemical groups in the binders were converted to higher oxidised forms of sulphur (e.g. sulphonates and sulphates) as the PAV treatment time was increased.

9.2 GPC Test Results and Analysis Figure 9.4 shows the GPC results obtained for a sample of neat SBS polymer (Kraton D1101) and a sample of Coober Pedy C170 bitumen after different periods of PAV ageing. All GPC results shown in this report have been normalised to a maximum differential refractive index value of one, at the highest point of the maximum GPC peak so that the changes in the profiles of the different GPC peaks can be easily compared.

The results obtained for the neat sample of SBS polymer indicated that the material showed two strong GPC peaks at retention times of 19.0 and 19.8 minutes, and a significant shoulder peak at a retention time of 18.2 minutes. The unaged Coober Pedy C170 bitumen sample showed a main GPC peak at a retention time of 25.3 minutes, and significant shoulder peak at a retention time of 22.6 minutes. As noted in Section 8.1.2, GPC measurements separate molecules based on molecular size, with larger molecules being detected at shorter retention times and smaller molecules being detected at longer retention times. The differences in peak retention times observed for the neat SBS polymer and the C170 bitumen in Figure 9.4 are consistent with the components of the polymer having higher molecular weights/sizes than the chemical components in bitumen.

Figure 9.4: GPC results obtained for samples of neat SBS polymer and the Coober Pedy C170 bitumen after different periods of PAV ageing

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

17 19 21 23 25 27

Diffe

rent

ial r

efra

ctiv

e in

dex

Retention time (minutes)

Coober Pedy C170 bitumen: 0 hours PAV treatment



SBS polymer



The GPC results obtained for the Coober Pedy C170 bitumen sample indicated that there was a significant increase in the contribution of the main shoulder peak at a retention time of 22.6 minutes as the PAV treatment time was increased. This result indicates that PAV ageing resulted in an increase in the number of larger-sized molecules in the bitumen. The proportion of larger-sized molecules in the bitumen increased as the PAV treatment time was increased.

The GPC results obtained for the Cooma C170 bitumen sample showed essentially the same trends as described above, in that the unaged bitumen sample showed a main GPC peak at a retention time of 22.5 minutes, and a significant shoulder peak at a retention time of 22.6 minutes. The contribution of the significant shoulder peak at a retention time of 22.6 minutes also increased with PAV ageing. Based on these results, PAV treatment appeared to increase the proportion of larger-sized molecules in both bitumen samples studied. The GPC results obtained for the Cooma C170 bitumen sample after different periods of PAV treatment are included in Appendix D.

GPC tests were conducted on all PMB samples included in this investigation (Table 3.1), except for samples which contained the S45R binder. Tests were not performed on S45R binder samples, as the rubber particles in crumb rubber binders are not readily soluble in organic solvents such as tetrahydrofuran (THF) which was used as the mobile phase in the GPC experiments. It was therefore thought that GPC tests on the S45R binders would not yield representative results that were indicative of the whole binder.

PMB samples that were analysed by GPC all showed similar overall trends as a function of PAV ageing time. Figure 9.5 shows the GPC results obtained for the S20E binder, which is representative of the results obtained for the PMBs studied. The GPC results obtained for the other PMBs investigated during this study are included in Appendix D.

Figure 9.5: GPC results obtained for the S20E binder after different periods of PAV ageing

All PMB samples showed the presence of one to three relatively small polymer-related GPC peaks, with peak maxima at retention times in the range between 17.4 and 20.6 minutes, as well as a much larger structured GPC peaks at higher retention times, prior to PAV ageing. The larger GPC peaks all included a main peak at a retention time of 25.4 ± 0.2 minutes, and a significant shoulder peak at 22.5 ± 0.1 minutes. Based on the GPC results obtained for the samples of C170 bitumen in this study, the large GPC peak observed in the case of the PMB samples can be associated with the non-polymer components (e.g. bitumen) in the PMBs.

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

17 19 21 23 25 27

Diffe

rent

ial r

efra

ctiv

e in

dex

Retention time (minutes)

S20E: 0 hours PAV treatment





Inspection of Figure 9.5 indicates that the S20E binder had polymer-associated GPC peaks with maxima at retention times of 18.2 and 19.1 minutes, and much larger structured GPC peaks at higher retention times due to the presence of the non-polymer components in the PMB, prior to PAV ageing. The much larger GPC peak had a peak maximum at a retention time of 25.3 minutes, and a significant shoulder peak at a retention time of 22.6 minutes.

On PAV ageing, all PMBs showed a reduction in the intensity of at least one of the GPC peaks associated with the polymer components in the PMBs. At the same time that this occurred, there was a general increase in the GPC signal for retention times between that observed of the polymer components in the PMBs and a retention time of the order of 21 minutes. In addition, the significant GPC shoulder peak at 22.5 ± 0.1 minutes (associated with the non-polymer components in the PMBs) increased for all PMBs studied on PAV ageing.

In the case of the results obtained for the S20E binder (Figure 9.5), PAV treatment caused a reduction in the intensity of the polymer-associated GPC peak at a retention time of 18.2 minutes. At the same time this occurred, there was an increase in the GPC signal for retention times of between about 18.5 and 21 minutes, as well as an increase in the intensity of the significant shoulder peak associated with the non-polymer components in the PMB at retention times between about 21 and 25 minutes. These two increases appeared to become more predominant as the PAV treatment time increased.

As smaller molecules display higher retention times in GPC experiments, the reductions in the intensities of the polymer-related peaks, combined with the increases in the GPC signal between the polymer-related peaks and a retention time of the order of 21 minutes, suggests that there was a reduction in the size of the polymer molecules in each of the PMBs when they were subjected to PAV ageing. This reduction in polymer molecular size implies that PAV treatment was causing the polymers in the PMBs to degrade by chain scission (i.e. the original polymer molecules in the PMBs were breaking into smaller fragments on PAV ageing).

All PMBs studied showed an increase in the significant shoulder peak at a retention time of 22.5 ± 0.1 minutes on PAV aging. This result implies that the PAV ageing caused an increase in the molecular size of some of the non-polymer components (e.g. bitumen) in the PMBs.

Based on the results of GPC measurements, PAV ageing appeared to increase the molecular size/weight of some of the chemical components in the two samples of C170 bitumen studied. In terms of the PMBs studied, PAV ageing appeared to cause an increase in the molecular weight/size of some of the non-polymer components in the PMBs, and broke the polymer molecules in the PMBs into smaller fragments. The chemical changes that occurred to the polymer in the PMBs during PAV ageing, however, were not sufficient to be detected during FTIR measurements (refer to Section 9.1).



10. Summary and Conclusions

A new long-term ageing test method for sprayed sealing binders is under development in Australia. As part of the development work, a laboratory study to characterise binders after different periods of PAV ageing was conducted using selected test methods. A range of bitumens and PMBs, the majority of which were used in a sprayed sealing trial in Coober Pedy in South Australia, were subjected to PAV ageing times of 0, 30 and 72 hours.

The work conducted during the second year of this project initially focused on assessing the effectiveness of two post-PAV ageing characterisation test methods (i.e. the DSR flow test and the extensiometer CTOD test), which were selected based on a literature review and preliminary experiments conducted during the first year of the study. The chemical properties of the binders studied were also investigated by Fourier transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC) as a function of PAV ageing time.

Conclusions that can be drawn based on the test results are as follows:

The yield energy values calculated from DSR flow test results increased for all binders studied as the PAV ageing time was increased. The two bitumen samples (Coober Pedy C170 bitumen and Cooma C170 bitumen) generally had higher rates of yield energy increase on PAV ageing than the PMB samples studied.

The stress ratio results (which were also calculated from DSR flow test results) decreased for all binders studied as the PAV ageing time was increased. The two bitumen samples studied did not show marked changes in stress ratio results when they were PAV aged. PMB samples generally displayed higher stress ratio values when unaged, but these values decreased rapidly on PAV ageing.

It is uncertain at this stage as to whether yield energy values or stress ratio results are more appropriate for characterising the properties of PAV aged binders in terms of ranking their resistance to low temperature cracking on the road. The results obtained from DSR flow tests will provide a database of results that can be used in the field validation study, which is proposed in the third year of this project (2014–15).

A number of the binders studied yielded negative values of the CTOD parameter when they were subjected to extensiometer CTOD tests. As negative values of the CTOD parameter are not theoretically possible, extensiometer CTOD tests were only performed on a limited number of binders. The negative results appear to be related to issues with the linear extrapolation process required to calculate the CTOD parameter. Extensiometer CTOD tests, in their current form, do not appear to be able to effectively characterise the properties of PAV treated binders.

The results of FTIR tests indicated that PAV ageing caused an increase in the number of oxygen-containing chemical groups in all binders studied (e.g. carbonyl group-containing chemical species and different oxidised forms of sulphur). The numbers of oxygen-containing groups in the binder samples increased as the PAV ageing time was increased. PAV ageing also appeared to increase the number of aromatic carbon groups in the each of binders. The quantitative changes in several FTIR spectral peaks with PAV ageing time were determined. These results will provide a database of results that can be used in the field validation study, which is proposed in the third year of this project.

GPC experiments indicated that PAV ageing increased the molecular size/weight of the chemical components in the two bitumen samples studied. In terms of the PMBs studied, PAV ageing appeared to cause an increase in the molecular weight/size of the non-polymer components in the PMBs, and broke the polymer molecules in the PMBs into smaller fragments. The chemical changes that occurred to the polymer in the PMBs during PAV ageing, however, were not sufficient to be detected during FTIR measurements.



References

Airey, GD 2003, ‘State of the art report on ageing test methods for bituminous pavement materials’, International Journal of Pavement Engineering, vol. 4, no. 3, pp. 165-76.

Andriescu, A & Hesp, SAM 2009, 'Time-temperature superposition in rheology and ductile failure of asphalt binders', International Journal of Pavement Engineering, 10:4, pp. 229-40.

Austroads 2005, Development of an aggregate size term for a reseal intervention model, AP-R271-05, Austroads, Sydney, NSW.

Austroads 2013a, Development of long-term ageing test method for sprayed sealing binders, AP-T225-13, Austroads, Sydney, NSW.

Austroads 2013b, Investigation of long-term ageing characterisation test methods for sprayed sealing binders, AP-T244-13, Austroads, Sydney, NSW.

Austroads 2013c, PMB sprayed seal trials: 12 month summary report, AP-T253-13, Austroads, Sydney, NSW.

Bureau of Meteorology 2014, Climate statistics for Australian locations: monthly climate statistics: summary statistics: Coober Pedy, BoM, Canberra, ACT, viewed 12 March 2014, <http://www.bom.gov.au/climate/averages/tables/cw_016007.shtml>.

Choi, YK 2005, ‘Development of the saturation ageing tensile stiffness (SATS) test for high modulus base materials’, PhD thesis, University of Nottingham, UK.

Dickinson, EJ 1981, Pavement temperature regimes in Australia: their effect on the performance of bituminous constructions and their relationship with average climate indicators, special report no. 23, Australian Road Research Board, Vermont South, Vic.

Gibson, N, Qi, X, Andriescu, A & Copeland, A 2012, ‘Recommended asphalt binder fatigue performance specification from full-scale accelerated pavement tests considering aging effects’, in Jones, D, Harvey, J, Mateos, A & Al-Qadi, I (eds), Advances in pavement design through full-scale accelerated pavement testing: proceedings of the 4th international conference on accelerated pavement testing, Davis, California, USA, 19-21 September, 2012, CRC Press, The Netherlands, pp. 433-41.

Günzler, H & Gremlich, HU 2002, IR spectroscopy: an introduction, Wiley-VCH, Weinheim, Germany.

Huang, J 1997, ‘Oxidation of asphalt fractions’, in Usmani, AM (ed), Asphalt science and technology, Marcel Dekker, New York, USA, pp. 119-134.

Jimenez, FP, Recasens, RM & Aldape, JC 2003, ‘Analysis of fatigue performance of asphalt mixtures: relationship between toughness and fatigue resistance’, International RILEM symposium, 6th, 2003, Zurich, Switzerland, RILEM Publications, Bagneux, France, pp. 372-9.

Johnson, CM, Wen, H & Bahia, HU 2009, ‘Practical application of viscoelastic continuum damage theory to asphalt binder fatigue characterization’, Journal of the Association of Asphalt Paving Technologists, vol. 78, pp. 597-638.

Kennedy, TW & Harrigan ET 1990, ‘SHRP asphalt research program products’, Journal of the Association of Asphalt Paving Technologists, vol. 59, pp. 610-20.

Ministry of Transportation 2001, Method of test for the determination of asphalt cement’s resistance to ductile failure using double edge notched tension test (DENT), laboratory testing manual, test method LS-299, Ministry of Transportation, Toronto, Ontario, Canada.

Munteanu, SB & Vasile, C 2005, ‘Spectral and thermal characterization of styrene-butadiene copolymers with different architectures’, Journal of Optoelectronics and Advanced Materials, vol. 7, no. 6, pp 3135-48.

Oliver, JWH 1984, ‘An interim model for predicting bitumen hardening in Australian sprayed seals’, Australian Road Research Board conference, 12th, 1984, Hobart, Tasmania, Australian Road Research Board, Vermont South, Vic, vol. 12, no. 2, pp. 112-20.



Oliver, JWH 2000, ‘Asphalt fatigue and low temperature binder properties’, contract report RC91101, ARRB

Transport Research, Vermont South, Vic.

Read, JM & Whiteoak, CD 2003, The Shell bitumen handbook, 5th edn, Thomas Telford Ltd, London, UK.

Silverstein, RM, Bassler, GC & Morrill, TC 1981, Spectrometric identification of organic compounds, 4th edn, John Wiley & Sons, New York, USA.

Stuart, BH 2004, Infrared spectroscopy: fundamentals and applications, John Wiley & Sons, Chichester, UK.

Tredrea, PF 2006, ‘Low temperature binder property contributing to asphalt fatigue performance’, ARRB conference, 22nd, 2006, Canberra, ACT, ARRB Group, Vermont South, Vic, 11 pp.

Wilson, G, Fernando, T, Budija, M & Urquhart, R 2009, ‘Crack reflection in sprayed seals: the search for a binder test’, AAPA international flexible pavements conference, 13th, Surfers Paradise, Queensland, Australia, Hallmark Conference and Events, Brighton, Vic, 7 pp.

Austroads Test Methods

AGPT/T121, Shear properties of polymer modified binders (ARRB elastometer).

AGPT/T124, Toughness of polymer modified binders (ARRB extensiometer).

AGPT/T190, Specification framework for polymer modified binders.

Standards Australia

AS 2008-2013, Bitumen for pavements.

AS 2341.5-1997, Methods of testing bitumen and related roadmaking products: method 5: determination of apparent viscosity by ‘Shell’ sliding plate micro-viscometer.

AS 2341.10-1994, Methods for testing bitumen and related roadmaking products: method 10: determination of the effect of heat and air on a moving film of bitumen (rolling thin film oven (RTFO) test).

AS 2341.13-1997, Methods for testing bitumen and related roadmaking products: method 13: long-term exposure to heat and air.

AASHTO Standards

AASHTO R28-12:2012, Standard practice for accelerated aging of asphalt binder using a pressurized aging vessel (PAV).

AASHTO T300-11:2011, Standard method of test for force ductility test of asphalt materials.

AASHTO T315-12:2012, Standard method of test for determining the rheological properties of asphalt binder using a dynamic shear rheometer (DSR).

ASTM International

ASTM D7175-08:2008, Standard test method for determining the rheological properties of asphalt binder using a dynamic shear rheometer.

European Committee for Standardization (CEN)

EN 14770:2012, Bitumen and bituminous binders: determination of complex shear modulus and phase angle: dynamic shear rheometer (DSR).



Appendix A DSR Flow Test Results Stress ratio and yield energy results that were obtained from the DSR flow test are presented in the following tables for each of the 11 binders subjected to PAV ageing. The tables also include the average values obtained for each material and a simple statistical analysis of the data (i.e. the standard deviation (Std. Dev.) and coefficient of variance (CoV) of the experimental results). Some of the terms used in the table headings are described below for ease of interpretation:

‘Test no.’ is the number of the replicate test that was performed on a binder sample. Tests were conducted at least in duplicate.

‘Strain @ peak’ indicates the strain value at the stress peak on the stress-strain curve (refer to Figure 5.5 for an example). Results are only shown if there was a distinct peak in the stress-strain curve.

‘Stress ratios at varying strain’ were calculated by dividing the stress value recorded at 10 strain by the stress value recorded at defined strains (e.g. at 1 strain). Stress ratios presented in the ‘peak column’ are only shown if there was a distinct peak in the stress-strain curve.

‘Yield energy values at varying strain’ indicate the values calculated up to each of the defined strains (i.e. 1 strain to the maximum strain of 10). The values presented in the ‘peak column’ are only shown if there was a distinct peak in the stress-strain curve.

Table A 1: Coober Pedy C170 bitumen

PAV (hrs)

Test no. Strain @ peak

Stress ratio Yield energy (kPa) 1 strain 2 strain 3 strain Peak 1 strain 2 strain 3 strain 10 strain Peak

0

1 0.97 0.96 1.00 18 37 56 187 2 0.94 0.87 0.88 16 36 55 175 3 0.89 0.87 0.88 17 36 55 175

Average 0.93 0.90 0.92 17 36 55 179 Std. Dev. 0.04 0.05 0.07 0.7 0.5 0.8 6.7 CoV (%) 4.29 5.57 7.44 4.2 1.5 1.5 3.7

30

1

0.84 0.86 1.00 287 657 1028 3392 2 0.90 0.85 0.86 269 622 977 3250 3 0.88 0.83 0.86 295 673 1055 3431


72

1 1.43 0.80 0.79 0.82 0.78 490 1095 1689 5300 749 2 1.51 0.80 0.79 0.83 0.80 537 1201 1851 5814 874 3 1.59 0.83 0.81 0.85 0.83 520 1170 1806 5815 898

Average 0.81 0.80 0.83 0.81 516 1155 1782 5643 840 Std. Dev. 0.01 0.01 0.01 0.02 23.9 54.4 83.5 297.1 80.3 CoV (%) 1.83 1.84 1.42 2.73 4.6 4.7 4.7 5.3 9.6



Table A 2: Cooma C170 bitumen

PAV (hrs)



0

1 0.98 0.95 0.96 21 46 70 235 2 0.91 0.88 0.90 24 50 76 250


30

1 1.57 0.84 0.82 0.84 0.81 346 785 1217 3896 592 2 1.81 0.86 0.84 0.87 0.83 380 855 1327 4293 762


72

1 1.06 0.77 0.78 0.83 0.77 652 1419 2155 6609 701 2 1.10 0.77 0.79 0.83 0.77 671 1456 2204 6754 745


Table A 3: S10E

PAV (hrs)



0

1 2.13 1.86 1.70 10 22 35 168 2 2.14 1.89 1.68 9 20 33 158


30

1 1.51 1.29 1.19 137 333 550 2366 2 1.52 1.30 1.19 139 338 561 2423


72

1 0.90 0.85 0.86 329 757 1194 4008 2 0.89 0.83 0.83 332 771 1219 4085




Table A 4: S15E

PAV (hrs)



0

1 2.82 2.37 2.08 17 21 23 48 2 2.81 2.37 2.07 18 21 24 50


30

1 1.30 1.07 0.97 214 260 287 278 2 1.30 1.06 0.97 239 292 321 310


72

1 0.80 0.76 0.79 703 734 712 539 2 0.77 0.73 0.76 715 747 724 572


Table A 5: S20E

PAV (hrs)



0

1 1.70 1.52 1.41 33 75 123 518 2 1.66 1.48 1.42 34 78 127 523


30

1 1.33 1.31 1.31 297 653 1007 3822 2 1.31 1.30 1.30 303 667 1027 3867


72

1 0.99 1.01 1.02 486 1032 1571 5407 2 1.02 1.03 1.04 496 1053 1606 5553




Table A 6: S35E

PAV (hrs)



0

1 1.30 1.20 1.16 7 16 25 95 2 1.30 1.16 1.12 7 16 25 96


30

1 1.48 1.30 1.22 90 214 350 1455 2 1.46 1.29 1.21 85 201 327 1357


72

1 0.91 0.86 0.87 231 535 842 2830 2 0.92 0.87 0.87 244 566 892 3006


Table A 7: S45R

PAV (hrs)



0

1 2.15 1.82 1.63 15 36 59 293 2 2.06 1.78 1.62 15 35 58 279


30

1 1.49 1.33 1.28 137 317 510 2119 2 1.41 1.28 1.23 125 289 464 1867 3 1.47 1.31 1.24 124 290 469 1941


72

1 0.89 0.85 0.86 237 540 846 2812 2 0.90 0.86 0.86 246 561 878 2929




Table A 8: Shell 5E

PAV (hrs)



0

1 1.24 1.17 1.14 20 44 68 255 2 1.17 1.09 1.07 20 43 67 245


30

1 1.10 1.06 1.07 240 539 840 3006 2 1.14 1.10 1.11 271 609 946 3393 3 1.14 1.09 1.10 217 486 758 2743


72

1 0.92 0.93 0.93 412 911 1406 4740 2 0.88 0.89 0.89 430 956 1475 4972


Table A 9: SAMI S20E SS as delivered

PAV (hrs)



0

1 2.46 2.13 1.96 17 40 66 331 2 2.38 2.06 1.92 18 41 68 335


30

1 1.75 1.52 1.40 152 360 589 2671 2 1.79 1.55 1.42 141 334 550 2517 3 1.81 1.56 1.41 154 370 610 2831


72

1 0.83 0.80 0.82 318 720 1120 3598 2 0.83 0.80 0.82 322 727 1132 3650




Table A 10: SAMI S20E SS as manufactured

PAV (hrs)



0

1 2.15 1.88 1.76 20 48 78 371 2 2.24 1.94 1.80 19 45 74 355


30

1 1.65 1.49 1.40 161 374 603 2614 2 1.62 1.45 1.35 170 394 638 2783 3 1.70 1.53 1.44 163 380 614 2699


72

1 0.81 0.81 0.84 345 764 1174 3705 2 0.81 0.81 0.84 370 821 1263 4015 3 0.68 0.68 0.71 370 782 1197 3635


Table A 11: ARRB 6% SBS

PAV (hrs)



0

1 2.78 2.23 1.94 15 36 61 338 2 2.87 2.31 1.96 15 37 64 360


30

1 1.03 0.98 1.02 134 308 481 1628 2 1.06 0.99 1.03 121 281 442 1519 3 1.06 1.00 1.03 131 303 475 1648


72

1 0.56 0.56 0.57 323 701 1078 3138 2 0.48 0.48 0.49 326 705 1078 3150




Appendix B FTIR Chemical Assignments Chemical group designation in report figures

Peak wavenumber (cm-1)

Peak chemical assignment

CH2 stretch 2920 Symmetric stretch of saturated methylene (CH2) groups

CH2 stretch 2851 Asymmetric stretch of saturated methylene (CH2) groups

C=O stretch 1697 Carbonyl (C=O) stretch

Aromatic C=C stretch 1600 Aromatic vinyl (C=C) stretch

CH3, CH2 bends 1456 Symmetric bend of saturated methylene (CH2) groups and asymmetric bend of methyl (CH3) groups

CH3 bend 1376 Symmetric bend of methyl (CH3) groups

S=O stretch 1031 Sulphoxide (S=O) stretch

PBD C-H wag 966 Out-of-plane wagging vibration of the CH groups near the double bond in trans-polybutadiene segments

CH2 rock 721 Rocking vibration of a methylene (CH2) group

PS C-H wag 699 Out-of-plane wagging vibration of the CH groups in a styrene aromatic ring, where all five hydrogens oscillate in phase

Source: Huang (1997), Munteanu and Vasile (2005), Silverstein, Bassler and Morrill (1981).



Appendix C Other FTIR Spectroscopy Results Figure C 1: FTIR spectra obtained for a sample of Cooma C170 bitumen after different periods of PAV ageing

Figure C 2: FTIR spectra obtained for the S10E binder after different periods of PAV ageing



Figure C 3: FTIR spectra obtained for the S15E binder after different periods of PAV ageing

Figure C 4: FTIR spectra obtained for the Shell S5E binder after different periods of PAV ageing



Figure C 5: FTIR spectra obtained for the SAMI S20E SS as delivered binder after different periods of PAV ageing

Figure C 6: FTIR spectra obtained for the SAMI S20E SS as manufactured binder after different periods of PAV ageing



Figure C 7: FTIR spectra obtained for the ARRB 6% SBS binder after different periods of PAV ageing



Appendix D Other GPC Test Results Figure D 1: GPC results obtained for the sample of Cooma C170 bitumen after different periods of PAV ageing

Figure D 2: GPC results obtained for the S10E binder after different periods of PAV ageing




Figure D 6: GPC results obtained for the SAMI S20E SS as delivered binder after different periods of PAV ageing



Figure D 7: GPC results obtained for the SAMI S20E SS as manufactured binder after different periods of PAV ageing

Figure D 8: GPC results obtained for the ARRB 6% SBS binder after different periods of PAV ageing


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