Design and Performance of Foamed Bitumen Stabilised Pavements - Progress Report 1

AP-T247-13

AUSTROADS TECHNICAL REPORT

Design and Performance of Foamed Bitumen Stabilised Pavements:

Progress Report One

Design and Performance of Foamed Bitumen Stabilised Pavements: Progress Report One


Published September 2013

© Austroads Ltd 2013

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

ISBN 978-1-925037-20-3

Austroads Project No. TT1825

Austroads Publication No. AP-T247-13

Project Manager David Hazell

Roads and Maritime Services NSW

Prepared by Geoff Jameson ARRB Group

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

Sydney NSW 2000 Australia Phone: +61 2 9264 7088

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

www.austroads.com.au

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

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

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mailto:[email protected]


Sydney 2013

About Austroads Austroads’ purpose is to:

promote improved Australian and New Zealand transport outcomes

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

promote improved practice and capability by road agencies.

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

Roads and Maritime Services New South Wales

Roads Corporation Victoria

Department of Transport and Main Roads Queensland

Main Roads Western Australia

Department of Planning, Transport and Infrastructure South Australia

Department of Infrastructure, Energy and Resources Tasmania

Department of Transport Northern Territory

Territory and Municipal Services Directorate Australian Capital Territory

Commonwealth Department of Infrastructure and Regional Development

Australian Local Government Association

New Zealand Transport Agency.

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


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SUMMARY

In July 2012 Austroads commissioned ARRB to conduct a four-year research project TT1825 Mix design and field evaluation of foamed bitumen stabilised pavements. The objectives of this project are to:

improve the Austroads procedures for the structural design of foamed bitumen stabilised materials for new pavements and structural rehabilitation treatments

identify distress modes of bitumen stabilised pavements from a series of trial sites

improve and harmonise national mix design procedures for bitumen stabilised materials.

This progress report summarises the test methods drafted to date and details the results of monitoring foamed bitumen stabilised pavement trial sites on:

the Calder Freeway at Woodend, Victoria which was constructed specifically for this project in 2013

Port Wakefield Road in Virginia, South Australia constructed in 2011 and which experienced fatigue cracking within two years of opening to traffic

Kewdale Road in Canning, Western Australia constructed in 2011 and which experiences shear stresses due to braking and acceleration of heavy vehicles

the Kwinana Freeway in Perth, Western Australia constructed in 2010, and

the New England Highway south of Toowoomba, Queensland constructed in 2009.

The report also identifies the mix design and structural design project tasks for 2013–14.


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CONTENTS

1 INTRODUCTION ................................................................................................................... 1

2 MIX DESIGN PROCEDURES ................................................................................................ 2 2.1 Introduction ............................................................................................................................ 2 2.2 Key Mix Design Characteristics.............................................................................................. 2

2.2.1 Review of Austroads Guide Part 4D Framework ........................................................... 2 2.3 Proposed Mix Design Framework .......................................................................................... 5 2.4 Progress on Test Method Development ................................................................................. 6 2.5 Verification of Mix Properties during Construction .................................................................. 7

3 CALDER FREEWAY WOODEND ......................................................................................... 8 3.1 Introduction ............................................................................................................................ 8 3.2 Site Investigation Prior to Stabilisation ................................................................................... 9 3.3 Properties of the Untreated Crushed Rock Base .................................................................... 9 3.4 Mix Design ........................................................................................................................... 10

3.4.1 Downer Infrastructure Testing ..................................................................................... 10 3.4.2 Department of Transport and Main Roads, Queensland Testing ................................. 11 3.4.3 Adopted Mix Design .................................................................................................... 12

3.5 Thickness Design ................................................................................................................ 12 3.6 Construction and Testing of the Foamed Bitumen Stabilised Trial Section ........................... 13

3.6.1 Construction of the FBS Pavement ............................................................................. 13 3.6.2 Surface Prior to Sealing .............................................................................................. 14 3.6.3 Two-coat Primerseal ................................................................................................... 15 3.6.4 Field Density Testing .................................................................................................. 16 3.6.5 Laboratory Testing of Field Samples ........................................................................... 17

3.7 Construction of Asphalt Section ........................................................................................... 17 3.8 Early-life Characteristics ...................................................................................................... 18

3.8.1 Surface Deflections ..................................................................................................... 18 3.8.2 Field Core Moduli ........................................................................................................ 22 3.8.3 Rutting and Roughness .............................................................................................. 24

3.9 Effect of Temperature on Moduli .......................................................................................... 25 3.10 Effect of Laboratory Compaction Method on Modulus .......................................................... 27 3.11 Traffic Monitoring ................................................................................................................. 28 3.12 Performance Prediction ....................................................................................................... 29

4 PORT WAKEFIELD ROAD VIRGINIA ................................................................................. 30 4.1 Introduction .......................................................................................................................... 30 4.2 Site Investigation Prior to Stabilisation ................................................................................. 31 4.3 Mix Design ........................................................................................................................... 31 4.4 Thickness Design ................................................................................................................ 32 4.5 Pavement Construction ........................................................................................................ 33

4.5.1 Foamed Bitumen Stabilised Sections .......................................................................... 33 4.5.2 Asphalt Section ........................................................................................................... 34

4.6 Visual Condition Monitoring ................................................................................................. 35 4.7 Pavement Investigation ........................................................................................................ 36

4.7.1 Asphalt Section ........................................................................................................... 36 4.7.2 FBS Sections .............................................................................................................. 39

4.8 Pavement Deflections .......................................................................................................... 44 4.9 Rutting and Roughness ....................................................................................................... 46 4.10 Traffic Monitoring ................................................................................................................. 48 4.11 Comparison of Observed and Predicted Performance ......................................................... 48


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5 KEWDALE ROAD WELSHPOOL ....................................................................................... 49 5.1 Introduction .......................................................................................................................... 49 5.2 Site Investigation Prior to Stabilisation ................................................................................. 50 5.3 Mix Design ........................................................................................................................... 51 5.4 Thickness Design ................................................................................................................ 52 5.5 Pavement Construction ........................................................................................................ 54 5.6 Pavement Condition Monitoring ........................................................................................... 55 5.7 Traffic Monitoring ................................................................................................................. 57 5.8 Comparison of Observed and Predicted Performance ......................................................... 57

6 KWINANA FREEWAY PERTH ............................................................................................ 58 6.1 Introduction .......................................................................................................................... 58 6.2 Site Investigation Prior to Stabilisation ................................................................................. 59 6.3 Mix Design ........................................................................................................................... 59 6.4 Thickness Design ................................................................................................................ 60 6.5 Pavement Construction ........................................................................................................ 61 6.6 Condition Monitoring ............................................................................................................ 61 6.7 Traffic Monitoring ................................................................................................................. 63 6.8 Performance Review ............................................................................................................ 64

7 NEW ENGLAND HIGHWAY QUEENSLAND ...................................................................... 65 7.1 Brief Description .................................................................................................................. 65 7.2 Site Investigation Prior to Stabilisation ................................................................................. 66 7.3 Mix Design ........................................................................................................................... 66 7.4 Thickness Design ................................................................................................................ 67 7.5 Pavement Construction ........................................................................................................ 67 7.6 Pavement Coring ................................................................................................................. 68 7.7 Pavement Maintenance ....................................................................................................... 69 7.8 Performance Monitoring ....................................................................................................... 71

7.8.1 Visual Inspections ....................................................................................................... 71 7.8.2 2012 Roughness and Rutting Data ............................................................................. 72

7.9 Traffic Monitoring ................................................................................................................. 74 7.10 Performance Prediction ....................................................................................................... 74 7.11 Comparison of Observed and Predicted Performance ......................................................... 75

8 PROPOSED 2013–14 RESEARCH ..................................................................................... 76 8.1 Introduction .......................................................................................................................... 76 8.2 Mix Design ........................................................................................................................... 76

8.2.1 Test Methods .............................................................................................................. 76 8.2.2 Laboratory Testing ...................................................................................................... 76

8.3 Structural Design ................................................................................................................. 77 8.3.1 Calder Freeway Woodend .......................................................................................... 77 8.3.2 Port Wakefield Road Virginia ...................................................................................... 77 8.3.3 Kewdale Road Welshpool ........................................................................................... 77 8.3.4 Kwinana Freeway Perth .............................................................................................. 77 8.3.5 New England Highway Queensland ............................................................................ 77 8.3.6 Review Other Monitoring Sites .................................................................................... 78 8.3.7 Additional Sites ........................................................................................................... 79

9 SUMMARY .......................................................................................................................... 80 9.1 Mix Design ........................................................................................................................... 80 9.2 Thickness Design ................................................................................................................ 80

REFERENCES ............................................................................................................................. 83 APPENDIX A FIELD PERFORMANCE MONITORING PROCEDURES FOR LTPP SITES ...... 85


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TABLES Table 2.1: Selecting mix components ....................................................................................... 5 Table 2.2: Selecting compactive effort to relative to field density .............................................. 6 Table 2.3: Determination of design bitumen content ................................................................. 6 Table 2.4: Test methods under development ............................................................................ 7 Table 3.1: Description of the Calder Freeway FBS pavement ................................................... 8 Table 3.2: Downer Infrastructure mix design results................................................................ 11 Table 3.3: TMR mix design testing .......................................................................................... 11 Table 3.4: Data used to predict fatigue life of the Calder Freeway pavement .......................... 13 Table 3.5: FBS field wet densities, moisture contents and dry densities .................................. 16 Table 3.6: Modulus and density of early-life field cores ........................................................... 23 Table 3.7: Effect of compaction method on modulus ............................................................... 28 Table 3.8: Traffic volume for the Calder Freeway northbound carriageway ............................. 28 Table 3.9: Results of average ESA per heavy vehicle Calder Freeway northbound

carriageway ............................................................................................................ 29 Table 4.1: Description of the Port Wakefield Road FBS pavements ........................................ 30 Table 4.2: Data used to predict the FBS fatigue life of Port Wakefield Road sections ............. 32 Table 4.3: Field dry densities and laboratory maximum dry densities ...................................... 34 Table 4.4: Estimated in situ subgrade CBR ............................................................................. 37 Table 4.5: Laboratory test results of Port Wakefield cores ...................................................... 38 Table 4.6: Particle size distribution and bitumen content of field cores obtained in

nominal 150 mm thick FBS section ........................................................................ 40 Table 4.7: Particle size distribution and bitumen content of field cores obtained in

nominal 200 mm thick FBS section ........................................................................ 42 Table 4.8: Traffic data on Port Wakefield Road 1.7 km south of Angle Vale Road .................. 48 Table 5.1: Description of Kewdale Road FBS pavement ......................................................... 49 Table 5.2: Results of coring and DCP testing on Kewdale Road FBS pavement

prior to stabilisation ................................................................................................ 50 Table 5.3: Results of particle size distribution and PI for the untreated materials in

Kewdale Road FBS pavement (prior to stabilisation) .............................................. 51 Table 5.4: Data used to predict FBS fatigue lives of Kewdale Road FBS trial

pavements ............................................................................................................. 53 Table 5.5: Traffic data for Kewdale Road ................................................................................ 57 Table 6.1: Description of Kwinana Freeway FBS pavement .................................................... 58 Table 6.2: Particle size distribution of the host material Kwinana Freeway FBS

pavement ............................................................................................................... 60 Table 6.3: Data used to predict FBS life of the under-designed Kwinana Freeway

pavement ............................................................................................................... 60 Table 6.4: QA testing for pavement thickness and density after construction .......................... 61 Table 6.5: Kwinana Freeway northbound carriageway daily heavy vehicle volumes ............... 63 Table 6.6: Kwinana Freeway average ESA per heavy vehicle type ......................................... 63 Table 7.1: Job description of New England Highway FBS pavement ...................................... 65 Table 7.2: Results of New England Highway cores extracted April 2000 ................................. 68 Table 7.3: New England Highway maintenance ...................................................................... 69 Table 7.4: Estimated 2012 traffic loading ................................................................................ 74 Table 7.5: Data for predicting allowable traffic loading of New England Highway

FBS pavement ....................................................................................................... 75 Table 8.1: Test methods under development .......................................................................... 76


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FIGURES

Figure 2.1: Suitable particle size distribution granular material stabilisation with bitumen binders (Zone A) ......................................................................................... 3

Figure 3.1: Calder Freeway FBS site during construction ........................................................... 9 Figure 3.2: Particle size distribution of the untreated crushed rock base .................................. 10 Figure 3.3: Calder Freeway pavement design .......................................................................... 12 Figure 3.4: Foamed bitumen stabilisation of the Calder Freeway, Woodend ............................ 14 Figure 3.5: Finished unsealed surface prior to trafficking overnight .......................................... 14 Figure 3.6: Condition after trafficking overnight ........................................................................ 15 Figure 3.7: Primersealing ......................................................................................................... 15 Figure 3.8: Nuclear gauge direct transmission field density measurements ............................. 16 Figure 3.9: Asphalt section of the Calder Freeway, Woodend .................................................. 18 Figure 3.10: Calder Freeway Woodend FBS early-life maximum deflections ............................. 19 Figure 3.11: Calder Freeway Woodend FBS early-life curvatures .............................................. 20 Figure 3.12: Calder Freeway Woodend asphalt section ............................................................. 21 Figure 3.13: FWD deflection testing and coring at Calder Freeway site eight days

after construction .................................................................................................... 22 Figure 3.14: Variation in field core modulus with density ............................................................ 23 Figure 3.15: Effect of laboratory drying and soaking on one month field core moduli ................. 24 Figure 3.16: Rutting five weeks after construction of the FBS pavement .................................... 25 Figure 3.17: Modulus variation with temperature ........................................................................ 26 Figure 3.18: Correction of WMAPT to measured temperature ratios .......................................... 26 Figure 3.19: Modulus variation with compaction method ............................................................ 27 Figure 4.1: Port Wakefield Road FBS site before stabilisation .................................................. 31 Figure 4.2: Stabilisation equipment used at the Port Wakefield Road FBS site ........................ 33 Figure 4.3: Compaction equipment used at the Port Wakefield Road FBS site ........................ 33 Figure 4.4: 100 mm thick dense graded asphalt inlay ............................................................... 35 Figure 4.5: Rutting due to foamed bitumen stabilisation of an old asphalt patch ....................... 35 Figure 4.6: Example of cracking observed in FBS section, after about 18 months of

trafficking ................................................................................................................ 36 Figure 4.7: Port Wakefield Road asphalt coring ....................................................................... 37 Figure 4.8: Cores obtained from the nominal 150 mm thick FBS section .................................. 39 Figure 4.9: Measured bitumen contents of nominal 150 mm FBS cores compared to

design application rates .......................................................................................... 40 Figure 4.10: Variation in field core moduli with density ............................................................... 41 Figure 4.11: BH11 core, FBS of an asphalt patch together with underlying asphalt

patching material .................................................................................................... 41 Figure 4.12: Relationship between indirect tensile strength and modulus................................... 42 Figure 4.13: Measured bitumen contents of nominal 200 mm FBS cores compared to

design application rate ........................................................................................... 43 Figure 4.14: Cores extracted from the nominal 200 mm thick FBS section ................................. 44 Figure 4.15: Port Wakefield Road measured surface deflections ............................................... 45 Figure 4.16: Pavement surface temperatures during FWD measurements ................................ 46 Figure 4.17: Port Wakefield Road rut depth measurements May 2013 ....................................... 47 Figure 4.18: Port Wakefield Road roughness measurements May 2013 .................................... 47 Figure 5.1: Kewdale Road looking towards intersection with Dowd Street ................................ 50 Figure 5.2: Crushed granite base resheet of Section 2 before stabilisation .............................. 51 Figure 5.3: Particle size distribution of untreated materials in Kewdale Road FBS

pavement ............................................................................................................... 52 Figure 5.4: Kewdale Road pavement structures ....................................................................... 53 Figure 5.5: Kewdale Road FBS site during stabilisation ........................................................... 54


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Figure 5.6: Ravelling of Section 1 due to trafficking before the asphalt surfacing was placed .................................................................................................................... 55

Figure 5.7: Kewdale Road measured surface deflections ......................................................... 56 Figure 6.1: Kwinana Freeway FBS site .................................................................................... 58 Figure 6.2: FWD testing results for Kwinana Freeway FBS site ............................................... 62 Figure 6.3: Predicted cumulative traffic loading ........................................................................ 64 Figure 7.1: New England Highway FBS pavement, near Nobby Connection Road

intersection (34.5 km) ............................................................................................. 65 Figure 7.2: Results of cured wet modulus for various FBS mixes for New England

Highway FBS pavement ......................................................................................... 67 Figure 7.3: Cracking at chainage 47.5 km in November 2009, 12 months before

geotextile seal was placed ..................................................................................... 70 Figure 7.4: Cracking at chainage 37.8 km in November 2009, 12 months before

geotextile seal was placed ..................................................................................... 70 Figure 7.5: Flushed binder on the surface suggests transverse cracking under the

PMB seal, chainage 46.7 km .................................................................................. 71 Figure 7.6: Transverse fatigue cracking in New England Highway FBS pavement,

chainage 53.6 km ................................................................................................... 72 Figure 7.7: Severe cracking in southbound lane near chainage 54.8 km .................................. 72 Figure 7.8: 2012 rutting and roughness for New England Highway FBS pavement .................. 73


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1 INTRODUCTION The Guide to Pavement Technology Part 5 Pavement Evaluation and Treatment Design includes an interim procedure for the thickness design of foamed bitumen stabilised (FBS) pavements (Austroads 2011a). However, there has been a concern that the interim FBS design procedure is not as well founded as those for conventional treatments due to lack of performance data. The design method needs to be verified/modified with field performance to provide a more accurate performance prediction method for foamed bitumen stabilised pavements.

In 2012 Austroads commissioned ARRB Group to undertake a research project TT1825 Mix design and field evaluation of foamed bitumen stabilised pavements. The objectives of this project are to:

improve the Austroads procedures for the design of foamed bitumen stabilised materials for new pavements and structural rehabilitation treatments

identify distress modes of bitumen stabilised pavements from the trial sites

improve and harmonise national mix design procedures for bitumen stabilised materials.

In the first year (2012–13) of the project, the following two issues were addressed regarding mix design procedures:

development of various draft test methods

performance monitoring and analysis of foamed bitumen stabilised pavements.

This report is a progress report on the developments and findings to date. Section 2 summarises the test methods drafted to date and those planned for 2013–14. Section 3 describes the construction and early-life monitoring of the Calder Freeway Woodend trial section. Section 4 to Section 7 detail monitoring and testing of the other trial sections. Section 8 is the proposed scope of the research for 2013–14.

To guide the project, a project Working Group (WG) has been formed with representative from road agencies, industry and ARRB, convened by Austroads Project Manager, David Hazell of Roads and Maritime Services.


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2 MIX DESIGN PROCEDURES

2.1 Introduction The Guide to Pavement Technology Part 4D Stabilised Materials (Austroads 2006) provides broad mix design guidance for foamed bitumen stabilised materials. The indirect tensile modulus values (initial, cured and soaked) are key characteristics in mix design. Leek and Jameson (Austroads 2011d) provide additional information on the mix design methods in use.

Although Part 4D provides the framework for the mix design procedures, there is a need to harmonise mix design test methods which have been developed by road agencies in the absence of Austroads methods. Harmonisation will enable improved understanding of the characteristics of foamed bitumen stabilised materials by pooling national expertise.

One key area where harmonisation would be of national benefit is the method used to compact FBS test cylinders for modulus testing. Part 4D describes two approaches:

gyratory compaction

Marshall drop hammer.

Measured moduli have been found to vary markedly with the compaction method used (Section 3.4).

2.2 Key Mix Design Characteristics 2.2.1 Review of Austroads Guide Part 4D Framework Properties of the untreated materials

The Guide to Pavement Technology Part 4D Stabilised Materials provides guidance on the types of granular materials suitable for stabilisation with bitumen. Materials usually suitable for bitumen stabilisation have a plasticity index (PI) not exceeding 10, although materials with PI up to 20 have been used by pre-treating with lime.

Figure 2.1 shows the recommended particle size distribution of materials suitable for bitumen stabilisation.

It is not envisaged that the project will need to review this guidance on materials selection, other than to consider the inclusion of a grading envelope for size 20 material.


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Source: Austroads (2006).

Figure 2.1: Suitable particle size distribution granular material stabilisation with bitumen binders (Zone A)

Maximum dry density and optimum moisture content

Part 4D describes the need to determine the maximum dry density (MDD) and optimum moisture content (OMC) of the host material to be stabilised in order to:

provide guidance on the mixing moisture content and density of laboratory test specimens

provide a reference density to assess achieved field densities against specified relative density values.

The project WG has confirmed the need to determine MDD and OMC and that improved guidance is required on how to select the mixing moisture content for preparation of test specimens from the laboratory compaction curve.

Note that Section 6.2.1 of Part 4D mentions MDD determination using gyratory compaction (80 cycles) and Marshall drop hammer compaction. Such MDD would only be useful to assess field relative density if the reference MDD relate to these laboratory compaction methods. Currently, reference MDD values are determined using either Standard or Modified drop hammer compaction test methods rather than gyratory compaction or Marshall hammer.

Bitumen foaming characteristics

Part 4D describes the use of laboratory foaming apparatus to determine the foaming characteristics of bitumen. The expansion ratio (increase in volume due to foaming) and the half-life (time for the expanded volume to collapse to half the maximum expansion volume) are the


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currently measured characteristics. It is not envisaged that the project will need to review the suitability of these characteristics, however there is a need to develop an Austroads test method.

Preparation of modulus test specimens

Part 4D mentions that for materials stabilised with bitumen binders, gyratory compaction (80 cycles) or Marshall drop hammer (50 blows per end) is generally adopted. Where the untreated materials include those over 20 mm in size, it is recommended that a 150 mm diameter mould and, by implication, an associated modified compaction foot be used.

There are two key issues of concern with this practice:

the known variation in the modulus values measured on specimens being compacted using these two compaction methods

the relationship between the modulus test specimen density and the specified field densities (commonly expressed in terms of standard or modified MDD) is not apparent.

There would be benefit in the project addressing these concerns. TMR experience is that laboratory cured samples compacted using 50 blow Marshall hammer achieve similar modulus values to the upper half of field cores after 12–24 months field curing (Austroads 2011d).

Modulus test specimens

The Part 4D design procedure provides the following indirect tensile modulus testing based in part on Main Roads Queensland practice in 2006:

initial modulus testing (uncured, unsoaked)

the specimens are dried for three days at 60 °C and the dry modulus determined

the specimens are then either soaked for 24 hours or soaked in a vacuum chamber for 10 minutes at 95 kPa and the wet modulus determined.

The uncured modulus should exceed 500–700 MPa, depending traffic loading, as a measure of the pavement’s ability to withstand trafficking when opened to traffic on the day of construction.

The design bitumen content is that which results in the optimum modulus.

Leek and Jameson (Austroads 2011d) describe more recent details of the Transport and Main Roads (TMR) Queensland method:

initial modulus testing is conducted after three hours curing at 25 °C

specimens are dried for three days at 40 °C and the dry cured modulus measured

specimens are then soaked in water in a vacuum chamber at a pressure not exceeding 95 kPa for 10 minutes and the wet cured modulus measured.

TMR also considers the ratio of the wet to dry cured moduli in selecting the bitumen content.

The change in curing temperature from 60 °C to 40 °C was implemented due to concerns that it 60 °C was above the softening point of the bituminous binder which allows its mobilisation and possible absorption into the aggregate. This was seen as a fundamental change to the materials property and therefore not representative.


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2.3 Proposed Mix Design Framework Key anticipated outcomes of the project are:

revised guidance for mix design for inclusion in Part 4D

the associated test methods.

As mentioned above no changes are proposed in relation to the material properties suitable for foamed bitumen stabilisation or the evaluation of the bitumen foaming characteristics, other than providing the test method.

In relation to performance-related tests, the first meeting of the project WG held in September 2012 confirmed that modulus should continue to be used in the Austroads mix design process based on the TMR experience over the last 10–15 years. At this stage it is proposed that the following key properties used to select the bitumen content follow the TMR practice:

the initial modulus

cured dry modulus

cured wet modulus

ratio of wet to dry moduli.

At the second meeting of the WG the issue of whether for heavily trafficked roads the modulus testing needed to be supplemented by deformation testing using the small wheel-tracking test (Austroads 2006) was discussed. It was agreed that this was not necessary at this stage. The principal performance test related to early-life rut-resistance would be initial modulus, with optional use of the wheel-tracking test method.

The steps in the proposed mix design procedure are described in Table 2.1 to Table 2.3. The process assumes that:

reference density used to assess field densities will continue to be based on maximum dry density measured in Standard or Modified drop hammer tests of the stabilised material

modulus test specimens will continue to be compacted using either Marshall drop hammer or gyratory (Servopac) compaction.

As such there is a need to establish the link between the density of the specimens tested for modulus and the field densities as described in Table 2.2.

Table 2.1: Selecting mix components

Step Activity

1 Obtain a representative sample of the untreated material to be stabilised, including any recycled surfacings materials.

2 Measure particle size distribution and assess whether it is necessary to improve the gradings by adding other granular materials.

3 Measure liquid limit, plastic limit and plasticity index and assess whether the material needs to be pre-treated.

4 Obtain a representative sample of Class 170 bitumen and determine the expansion ratio and half-life on samples with 2%, 3% and 4% water content.

5 Compare measured expansion ratio and half-life against limits. If the limits cannot be achieved at any moisture, assess whether a foaming agent or another bitumen is needed and repeat step 4. Otherwise select the moisture content for foaming and proceed to step 6.

6 Select whether the secondary binder is lime or cement and obtain a representative sample and check for compliance.


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Table 2.2: Selecting compactive effort to relative to field density

Step Activity

7 From the specification for construction, determine the whether Standard or Modified maximum dry density (MDD) will be used in assessing field compaction and determine the minimum acceptable percentage of the MDD used in the works.

8 Select the mostly likely design bitumen content and secondary binder content.

9 Mix the granular materials, foamed bitumen and secondary binders over a range of moisture contents, including the likely field moisture content at which the material will be stabilised.

10 Determine Standard or Modified laboratory compaction curve as appropriate.

11 Using steps 7 and 10, determine the minimum acceptable field dry density.

12 Select whether the modulus test specimens will be compacted using gyratory compaction (Servopac) or Marshall hammer.

13 Mix the granular materials, foamed bitumen and secondary binders using the likely field moisture content (e.g. 60–80% Standard or Modified optimum moisture content).

14 Compact the mixture and assess the compactive effect to achieve the minimum acceptable field dry density (step 12). In the case of the Servopac, the compactive effort is the number of cycles and for the Marshall hammer the number of blows per face.

Table 2.3: Determination of design bitumen content

Step Activity

15 Mix the granular materials, foamed bitumen and secondary binders using the step 13 moisture content. Initially the binder contents in step 8 shall be used.

16 Compact the three cylinders of the mixture using the compactive effort from step 14.

17 Cure the specimens for three hours at 25 °C and measure the initial indirect tensile modulus – Mi.

18 Dry the specimens for three days at 40 °C and measure the dry indirect tensile modulus – Md.

19 Soak the specimens in a vacuum chamber for 10 minutes at 95 kPa and measure the wet indirect tensile modulus – Mw.

20 Calculate the ratio of the wet to dry modulus.

21 Compare the measured results of steps 17–20 with the specified values. If the results are below requirements, increase the bitumen content and/or secondary binder and repeat steps 15–20. If the results are above requirements, decrease the bitumen content and repeat steps 15–20.

22 Plot the moduli and modulus ratio against bitumen content and select the design bitumen content. The specified bitumen content may need to be adjusted for construction tolerance.

23 If the mix design is significantly different from that used in step 10, it may be necessary to repeat step 10 to provide appropriate values for field compaction assessment.

2.4 Progress on Test Method Development Table 2.4 lists the test methods that have been identified for drafting. The initial draft of test methods T301, T305, T310 and T311 have been revised in light of WG comments and utilising the following TMR test methods:

Q138 Preparation and Testing of Foamed Bitumen Materials, draft October 2012

Q139 Resilient Modulus of Stabilised Materials (indirect tensile method), draft October 2012.

It is anticipated these methods may need to be revised in 2013–14 following trial use and feedback from users.


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Table 2.4: Test methods under development

Number Title Status

T301 Determination of Foaming Properties of Bitumen Drafted

T305 Mixing of Foamed Bitumen Stabilised Materials (includes method of establishing mixing moisture content) Drafted

T310 Compaction of Test Cylinders of Foamed Bitumen Stabilised Mixtures: Part 1 Dynamic Compaction Using Marshall Drop Hammer

Drafted

T311 Compaction of Test Cylinders of Foamed Bitumen Stabilised Mixtures: Part 2 Gyratory Compaction Drafted

T313 Compaction of Test Slabs of Foamed Bitumen Stabilised Mixtures To be drafted in 2013–14

T320 Curing of Test Cylinders of Foamed Bitumen Stabilised Mixtures To be drafted in 2013–14

T321 Curing of Test Slabs of Foamed Bitumen Stabilised Mixtures To be drafted in 2013–14

T330 Resilient Modulus of Foamed Bitumen Stabilised Mixtures To be drafted in 2013–14

T340 Deformation Resistance of Foamed Bitumen Stabilised Mixtures by the Wheel-tracking Test To be drafted in 2013–14

2.5 Verification of Mix Properties during Construction In addition to the laboratory mix design process, WG members have raised the need to provide a process to compact modulus specimens of uncompacted stabilised materials sampled from the roadbed during construction. This testing is required to verify the mix properties during construction.

Accordingly, it is anticipated that during the four-year project, testing will be undertaken to assess the suitability of various field compaction and curing test methods.


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3 CALDER FREEWAY WOODEND

3.1 Introduction One of the key objectives of this project is to improve the Austroads interim procedures for the structural design of foamed bitumen stabilised materials for new pavements and structural rehabilitation treatments (Austroads 2011a). To address this need the performances of a number of pavements are being monitored.

In March 2013, VicRoads and the stabilisation industry agreed to support the Austroads project by constructing an under-designed FBS pavement on the existing Calder Freeway, Woodend, Victoria. That is, the section was designed with a reasonable likelihood of distress within the period of the research project.

Details of locality and job statistics (job size, FBS specification and construction method) of the Calder Freeway FBS pavement are given in Table 3.1.

Table 3.1: Description of the Calder Freeway FBS pavement

Location Calder Freeway bypass of Woodend 69.3 to 69.5 km Job size Length 100 m

Number of lanes 1 Lane width 4.8 m (3.5 m slow lane and 1.3 m shoulder) Total area 480 m2

Stabilisation depth Nominal 150 mm FBS base Wearing course Size 14/7 primerseal, includes 10 parts rubber

Foamed stabilisation specification

Mix design Undertaken by Downer Infrastructure and Department of Transport and Main Roads Queensland

Host materials VicRoads Class 1 crushed rock (size 20 mm), plasticity index 2 to 6 Supplementary binder 1.5% quick lime Bitumen 3.5% class 170 bitumen Foaming agent 0.6% Terec 311

Construction method Work specifications and QA testing

VicRoads specifications

Construction date Foamed bitumen stabilisation, 4 March 2013 Two-coat primerseal of FBS, 5 March 2013 Asphalt section, 21 March 2013

Figure 3.1 shows a view of the trial site. Prior to stabilisation the pavement was a granular pavement with a sprayed seal surface, originally constructed in 2001 as part of the bypass of Woodend. Recently increasing pothole patching within the top 100 mm of the base has been required in the outer wheelpath. This patching material and the existing seal were mixed with the crushed rock base during the foamed bitumen stabilisation.


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Source: Photograph taken by VicRoads staff (2013).

Figure 3.1: Calder Freeway FBS site during construction

3.2 Site Investigation Prior to Stabilisation The Calder Freeway bypass of Woodend was designed and constructed using a design traffic loading of 1.1 x 107 ESA over a 30 year period. The bypass was opened to traffic in December 2001. The pavement structure prior to stabilisation comprised:

a prime and double/double size 14/7 seal

200 mm Class 1 (size 20 mm crushed rock) base

150 mm Class 3 (size 20 mm crushed rock) upper subbase

150 mm Class 4 (size 40 mm crushed rock) lower subbase

300 mm Type A capping layer

subgrade clay (laboratory soaked design CBR 2%).

3.3 Properties of the Untreated Crushed Rock Base The crushed rock base was a nominal VicRoads Class 1 crushed rock base of low plasticity and a particle size distribution as given in Figure 3.2. The sample taken from the road bed in March 2013, was taken after the mixing pass and before addition of the lime and bitumen.


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Figure 3.2: Particle size distribution of the untreated crushed rock base

3.4 Mix Design Prior to construction, samples of the crushed rock base were obtained from the pavement for the mix design. The designs were undertaken by two experienced laboratories: Downer Infrastructure (contractor for the Calder Freeway trial) and the Department of Transport and Main Roads (TMR) Queensland.

3.4.1 Downer Infrastructure Testing In February–April 2012, mix design testing was undertaken by Downer Infrastructure at the request of ARRB. The untreated crushed rock base was non-plastic (unexpected as specified to have a plasticity index in the range 2–4) with a particle size distribution shown in Figure 3.2. The Modified compaction maximum dry density of the untreated material was 2.25 t/m3 and the optimum moisture content (OMC) was 4.8%. By comparison, in subsequent testing of stabilised materials retrieved during construction the maximum dry density was 2.17 t/m3 and the optimum moisture content was 4.5% (Section 3.6.5).

To prepare the test specimens, the untreated base was mixed at the bitumen, quicklime and moisture contents shown in Table 3.2. The mixing moisture content was about 85% of Modified OMC of the untreated material and about 92% of the Modified OMC of the stabilised material.

Modulus test specimens (150 mm diameter) were then compacted using a Servopac gyratory compactor and then tested for indirect tensile modulus. The results are given in Table 3.2.

0

10

20

30

40

50

60

70

80

90

100

0.01 0.1 1 10

Percentage passing

Sieve size (mm)

Lower limit Zone A Austroads 2006

Upper limit Zone A, Austroads 2006

Feb 2012 sample from road bed, tested by Downer

Oct 2012 sample from road bed, tested by TMR

March 2013 sample from road bed during construction


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Table 3.2: Downer Infrastructure mix design results

Bitumen content

(%)

Quicklime content

(%)

Moisture content

(%)

Mean dry density (t/m3)

Mean indirect tensile modulus (MPa) at 25 °C % wet/dry modulus Initial

modulus(1) Cured dry modulus(2)

Cured wet modulus(3)

3.0 1 3.9 2.14 463 2220 1180 53 3.5 1 4.2 2.19 411 2680 1030 37 4.0 1 4.3 2.19 522 4530 1970 44

1 Cured unsealed for three hours at 25 °C. 2 Cured unsealed for three days at 40 °C. 3 Soaked in water under vacuum of 95 kPa for 10 minutes at 25 °C.

3.4.2 Department of Transport and Main Roads, Queensland Testing In December 2012 prior to construction, another sample of the crushed rock base was excavated from the pavement to enable mix design testing by the Department of Transport and Main Roads (TMR). Following TMR practice, the modulus test specimens were compacted using a modified Marshall hammer in a 150 mm diameter mould by applying 50 hammer blows to each end of the specimen.

The particle size distribution of this sample had significantly less fines than the material used in the Downer testing (Figure 3.2). In addition, a plasticity index of 4–5 was measured by TMR whereas the earlier Downer material was measured to be non-plastic. Downer advise a possible reason for this difference in plasticity index as follows:

This may be due to allowance in the AS method in line with most international methods to classify material not able to be rolled to an initial 3 mm thread as non-plastic. The TMR test method varies from this and states that at any point if it cannot be rolled to a 3 mm thread that should be taken as its plastic limit. This needs reviewing as it will affect classifications on marginal materials.

For the TMR mix the Standard compaction curve was measured: the Standard maximum dry density was 2.22 t /m3 and OMC was 6.6%.

The FBS mixes were all mixed at a target moisture content of 70% Standard OMC of the untreated material, that is 4.6%. As the Modified OMC of the stabilised material recovered from the roadbed (Section 3.6.5) was 4.5%, the TMR mix design moisture contents were close to the Modified OMC of the stabilised material. The modulus, bitumen, hydrated lime and moisture contents are shown in Table 3.3. Note that the densities of the test specimens were not measured.

Table 3.3: TMR mix design testing

Bitumen content (%)

Hydrated lime content

(%)

Moisture content (%)

Mean indirect tensile modulus (MPa) at 25 °C % wet/dry modulus Initial



2 2 4.6 1 400 12 980 5 970 46 3 2 4.5 1 460 10 050 5 510 55 4 2 4.6 1 380 7 600 4 780 63

TMR minimum requirements for base with > 1000 ESA/day 700 4 000 2 000 50 1 Cured unsealed for three hours at 25 °C. 2 Cured unsealed for three days at 40 °C. 3 Soaked in water under vacuum of 95 kPa for 10 minutes at 25 °C. Source: Personal communication TMR (2012).

Note that the TMR moduli are significantly higher than the Downer values (Table 3.2). Later testing of material retrieved from the roadbed (Section 3.10) suggested that this is in part due to use of different methods used to compact the test specimens.


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3.4.3 Adopted Mix Design As shown in Table 3.3, TMR testing indicated that the crushed rock base stabilised with 3% bitumen and 2% hydrated lime met all TMR minimum mix design requirements for basecourses on heavily trafficked roads. Given that most FBS in Australia to date have been constructed using design bitumen contents in excess of 3%, it was decided to adopt the following design binder contents:

3.5% bitumen

1.5% quicklime (equivalent to about 2% hydrated lime).

3.5 Thickness Design The objective of the project is to obtain pavement performance data with up to three years of trafficking. Accordingly, the Calder Freeway pavement was designed with a reasonable likelihood of distress occurring within the project period. A nominal FBS thickness of 150 mm was agreed (Figure 3.3), this being the minimum practical thickness based on industry advice.

Sprayed bituminous seal

150 mm foamed bitumen stabilised crushed rock base

50 mm Class 2 crushed rock base

150 mm Class 3 crushed rock subbase

150 mm Class 4 crushed rock subbase

300 mm capping layer

Subgrade design CBR = 2%

Figure 3.3: Calder Freeway pavement design

Using the interim thickness design method, a preliminary estimate has been made of the predicted life of the nominal 150 mm thickness stabilisation treatment. In the interim method, the FBS design modulus is determined from indirect tensile moduli measured on laboratory-manufactured specimens cured for three days at 40 °C and then soaked in water under vacuum of 95 kPa for 10 minutes. This method was based on TMR comparison of cured wet indirect tensile moduli with in situ values back-calculated from surface deflections on pavements stabilised to depths of 250 mm to 300 mm.

However, from Calder Freeway trial cured wet moduli are overly conservative moduli compared to the field cores (Section 3.8.2). Consequently, at this stage in the project, it is suggested the FBS design moduli be determined from the cured dry moduli of laboratory-manufactured specimens compacted using the gyratory method. This will be investigated further as part of the project.

Using the gyratory compacted specimens, the mean cured dry modulus was 2680 MPa, at a temperature of 25 °C, a dry density of 2.19 t/m3. The average density of the field cores extracted to date is 2.08 t/m3, about 5% lower than the density of the mix design specimens. Currently the interim process does not provide a procedure to adjust modulus for variation in density. Based on the data in Figure 3.14 it is estimated that a reduction in density of 5% leads to a reduction in modulus of about 30%. Correcting the cured dry modulus to the in situ density, a Weighted Mean Annual Pavement Temperature (WMAPT) of 24 °C and a design traffic speed of 80 km/h, a FBS design modulus of 1800 MPa was calculated.

The fatigue life of the FBS layer was predicted using the Austroads interim design method and the input data given in Table 3.4.


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Table 3.4: Data used to predict fatigue life of the Calder Freeway pavement

Pavement component Design parameter Available data Technical basis for data selection Subgrade Subgrade type clay Presumptive laboratory soaked CBR of 2% for basaltic clay

Design modulus 20 MPa Subbase Subbase thickness 350 mm Assume high standard base material from Table 6.5 of GPT Part 2

(Austroads 2012) Design modulus 390 MPa (top layer) FBS base FBS thickness 130 mm Design 150 mm design thickness less 20 mm construction tolerance

Design modulus 1800 MPa Derived from the mix design measured dry cured moduli (Section 3.4) FBS volume of binder 7% Assumed

Wearing course Thickness n.a. 14/7 mm double primerseal Design modulus n.a.

Using the interim design method, the 150 mm thick FBS pavement the predicted FBS fatigue life is 6.6 x 105 ESA at 50% design reliability. As discussed in Section 3.10 the estimated annual traffic loading is about 9 x 105 ESA. Consequently, the design model predicts there is a 50% chance of observing FBS fatigue cracking within 12 months.

3.6 Construction and Testing of the Foamed Bitumen Stabilised Trial Section

3.6.1 Construction of the FBS Pavement The FBS pavement was constructed on 4 March 2013 and the unsealed surface was opened to traffic the same day. The following day the surface was sealed using a size 14/7 primerseal and opened to traffic again.

The project was undertaken by VicRoads, Downer Infrastructure Pty Ltd and Stabilised Pavements Australia Pty Ltd as a contribution to this national research project.

The pavement section was 100 m in length and 4.8 m in width covering the slow lane and part of the sealed shoulder. The fast lane was not treated.

The construction sequence was as follows (Figure 3.4):

First mixing pass with Wirtgen Stabiliser WR2400 in two 2.4 m widths, this mixed the sprayed seal through crushed rock base to a nominal depth of 150 mm.

The mixed material was then reshaped with the grader.

Quicklime was then spread at an average rate of 4.49 kg/m2, about 10% less than the target of 4.8 kg/m2 (assuming mean compaction to 98% Modified maximum dry density). The lime was then slaked.

The slaked lime was mixed through crushed rock base to a nominal depth of 150 mm.

The surface was then shaped and lightly compacted with a 12 t vibrating smooth drum roller.

The lime reacted with the crushed rock base for about two hours while the bitumen heated to 170 °C in the tanker.

The foaming agent (0.6% Terec 311, about 70 litres) was added to the bitumen in the tanker and then connected to the stabiliser.

With the tanker and the stabiliser connected, the foamed bitumen was then mixed through the lime-treated crushed rock base. The average bitumen application rate was 11.65 kg/m2. This equates to about 3.6% bitumen content, close to the target of 3.5%.


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The FBS crushed rock base was then shaped with a grader and compacted using (a) a 12 tonne vibrating smooth drum roller and (b) a 16 tonne multi-tyre roller (Figure 3.4).

Source: Photographs taken by ARRB and VicRoads staff.

Figure 3.4: Foamed bitumen stabilisation of the Calder Freeway, Woodend

Figure 3.5 shows the compacted unsealed surface prior to opening to traffic the same day.

Figure 3.5: Finished unsealed surface prior to trafficking overnight

3.6.2 Surface Prior to Sealing Prior to construction there was discussion between VicRoads and the contractor as to whether the stabilised pavement should be cured overnight and sealed the next day before opening to highway traffic. On this heavily trafficked road, VicRoads required the road be opened to traffic immediately following construction.


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When the unsealed pavement was inspected the day after construction, the unsealed surface had ravelled under the heavy traffic loading as shown in Figure 3.6. In addition, there was a significant amount of deformation of the FBS layer, also shown in Figure 3.6 (refer to Section 3.8.3). The rutting over about a 10 m length at the start of the works was excessive; this area was subsequently milled and patched with a 100 mm thickness of asphalt during the construction of the asphalt control section (Section 3.7).

Widespread ravelling overnight of the unsealed surface Deformation of the FBS material near start of the trial section

Figure 3.6: Condition after trafficking overnight

3.6.3 Two-coat Primerseal A size 14/7 primerseal was placed on 5 March 2013, the day following the FBS construction. The total binder application rate was 1.8 l/m2 (1.2 l/m2 and 0.6 l/m2). The sprayed binder includes 8 parts cutter and 10 parts rubber; the addition of the rubber was not planned but occurred due to the sealing contractor using this binder for another VicRoads job in the area that day.

Figure 3.7: Primersealing


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3.6.4 Field Density Testing The field densities were measured at six sites in the slow lane after the completion of initial rolling (Figure 3.8). At each test site a sample of FBS material was excavated for determination of oven-dried moisture content. The wet density, moisture contents and dry densities are given in Table 3.5. The mean field moisture content was 3.9% and the mean dry density 2.13 t/m3. As described in Section 3.6.5, the Modified maximum dry density (MDD) of the foamed stabilised base was 2.17 t/m3. Accordingly, the mean field density equated to 98% Modified MDD. The measured mean field moisture content of 3.9% was about 87% of the Modified OMC (Section 3.6.5).

Figure 3.8: Nuclear gauge direct transmission field density measurements

Table 3.5: FBS field wet densities, moisture contents and dry densities

Project chainage Wet density (t/m3)

Moisture content (%)

Dry density (t/m3)

Relative density (%)

10 2.18 3.8 2.10 96.8

20 2.22 3.9 2.13 98.2

30 2.22 3.6 2.14 98.6

40 2.22 4.1 2.13 98.2

50 2.21 3.8 2.13 98.2

60 2.24 4.2 2.15 99.1

Mean 2.22 3.9 2.13 98.2 Following these field density measurements, the surface was reworked to provide a tighter surface by lightly watering and re-rolling. A repeat series of measurements indicated no significant change in the mean wet densities following this rework.


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3.6.5 Laboratory Testing of Field Samples Materials were sampled from the roadbed during construction for laboratory testing.

The untreated crushed rock was tested for particle size distribution (Figure 3.2). The material varied from the TMR mix design material but was similar to the Downer mix design material. The material was non-plastic again consistent with the Downer mix design material but different from the plasticity index of 4–5 measured by TMR in its mix design (Section 1).

The untreated crushed rock was compacted in a150 mm mould to determine the Modified compaction curve. The Modified maximum dry density (MDD) was 2.25 t/m3 and the optimum moisture content (OMC) was 5.3%. These values are similar to those measured by Downer during the mix design (Section 3.4.1).

Samples of the lime-treated crushed rock were obtained from the roadbed and tested for lime content and active lime content (CaO) in accordance with test method ASTM D25C-2006. The quicklime contents were 1.8% and 1.2% compared to the design value of 1.5%. The active lime contents were 1.07% and 0.71%. Note that the design value of 1.5% quicklime results in 4.8 kg/m2 for a 150 mm depth. The contractor advised the actual spread rate was 4.5 kg/m2, slightly less than the design value.

Uncompacted lime-treated and foamed bitumen stabilised material was sampled from the roadbed during construction to determine the Modified compaction curve. The MDD was 2.17 t/m3 and the OMC was 4.5%.

The 3.5% design bitumen content equated to an application rate of 11.2 kg/m2 for 150 mm stabilisation depth. The contractor advised the actual application rate was greater, 11.65 kg/m2. Samples of the loose foamed stabilised crushed rock from the roadbed during construction were tested using the Austroads ignition furnace method, AS 2891.3.3 pressure filter solvent washing method and the TMR solvent extraction method. The measured binder contents were 3.4%, 3.7% and 2.9% respectively. In addition, a bitumen content of 3.4% was obtained by ignition oven testing of a field core taken eight days after construction. Note that these measured bitumen contents included asphalt pot hole patching material and the pulverised bituminous sprayed seal surfacing.

3.7 Construction of Asphalt Section On 21 March 2013, a 100 mm thick inlay of size 20 mm dense graded asphalt was placed over 100 m section abutting the northern end of the FBS section to compare performance with the 150 mm thick FBS section.

The existing seal and top 100 mm of crushed rock base were milled from the pavement, the milled surface broomed, a bitumen emulsion tack coat was applied to the edges and then the asphalt was placed and compacted in a single layer (Figure 3.9). The underlying crushed rock base was very firm and tight and did not require compaction prior to asphalt placement.

As discussed in Section 3.6.2, a 10 m section at the southern end of the FBS pavement was milled and inlaid with asphalt as part of the works as it rutted in the first 24 hours of trafficking.


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Figure 3.9: Asphalt section of the Calder Freeway, Woodend

3.8 Early-life Characteristics 3.8.1 Surface Deflections Falling weight deflectometer (FWD) deflection testing of the FBS crushed rock base was undertaken eight days and one month after construction. Measurements were taken:

on the edge line

in the outer wheelpath

between the wheelpaths.

The measured maximum deflections (D0) and curvatures (D0–D200) were normalised to a plate contact stress of 566 kPa. The maximum deflections and curvature were corrected from the pavement temperature at the time of measurement to the Weighted Mean Annual Pavement Temperature (WMAPT) of 24 °C using the interim deflection-temperature method developed in Section 3.9.

The maximum deflections and curvatures are shown Figure 3.10 and Figure 3.11.


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Figure 3.10: Calder Freeway Woodend FBS early-life maximum deflections

0.00

0.10

0.20

0.30

0.40

0.50

0 10 20 30 40 50 60 70 80 90 100

Maximumdeflection at 566 kPa

(mm)

Chainage (m)

Calder Freeway Woodend foamed bitumen stabilised material 8 days post-construction

corrected from measurement temperature of 29°C to WMAPT =24°C

Outer wheelpath

Between wheelpaths

0.00

0.10

0.20

0.30

0.40

0.50

0 10 20 30 40 50 60 70 80 90 100


(mm)

Chainage (m)

Calder Freeway Woodend foamed bitumen stabilised material 1 month post-construction

corrected from measurement temperature of 12°C to WMAPT of 24°C

Outer wheelpath

Between wheelpaths


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Figure 3.11: Calder Freeway Woodend FBS early-life curvatures

Surface deflections were also measured on the 100 mm thick asphalt section two weeks after construction. The maximum deflections and curvatures normalised to 566 kPa and adjusted from the pavement temperature during measurement to the WMAPT of 24 °C are shown Figure 3.12.

0.00

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0.07

0.08

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0.10

0 10 20 30 40 50 60 70 80 90 100

Curvatures(D0-D200) at 566 kPa

(mm)

Chainage (m)

Calder Freeway Woodend foamed bitumen stabilised material 8 days post-construction

corrected from measurement temperature of 29°C to WMAPT = 24°C

Outer wheelpath

Between wheelpaths

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

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0 10 20 30 40 50 60 70 80 90 100


(mm)

Chainage (m)

Calder Freeway Woodend foamed bitumen stabilised materials 1 month post-construction


Outer wheelpath

Between wheelpaths


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FBS cores taken along the edge line (Figure 3.13) indicated an FBS layer thickness of 200 mm or more. In future monitoring, in situ layer moduli will be estimated by back-calculation of the measured bowls using FBS layer thicknesses estimated from cores in the trafficked area.

Figure 3.12: Calder Freeway Woodend asphalt section

0.00

0.10

0.20

0.30

0.40

0.50

0.60

100 110 120 130 140 150 160 170 180 190 200


(mm)

Chainage (m)

Calder Freeway Woodend dense graded asphalt 2 weeks post-construction


Outer wheelpath

Between wheelpaths

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

100 110 120 130 140 150 160 170 180 190 200


(mm)

Chainage (m)

Calder Freeway Woodend dense graded asphalt 2 weeks post-construction


Outer wheelpath

Between wheelpaths


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3.8.2 Field Core Moduli As a contribution to this national research project, Stabilised Pavements of Australia Pty Ltd took cores of FBS material eight days and one month after construction along the edge line at chainages identified by ARRB. Surface deflections were measured at these locations prior to coring.

At eight days some of the cores could not be fully extracted as the upper and lower portions sheared apart in the coring process. However, all four cores were extracted intact one month after construction. Figure 3.13 shows an example taken on the edge line at chainage 40 m.

The cores were transported to Downer Infrastructure’s laboratory in Somerton, Victoria for testing. Each core was sawn into upper and lower portions and the bulk dry density and resilient modulus measured. The results are summarised in Table 3.6.

Figure 3.13: FWD deflection testing and coring at Calder Freeway site eight days after construction

The density of the bottom portion of the field cores was 3–6% lower than the upper portion. This was a significant factor in the modulus decrease with depth. Figure 3.16 shows the variation in modulus with density and time. The moduli of cores obtained at eight days and one month were reasonably similar for a given density. The next pavement coring is planned 12 months after construction (March 2014).

Note that the modulus of cores tested as received from the field appears in closer agreement to the Downer mix design cured dry moduli (Table 3.2) than the TMR values (Table 3.3).

As shown in Figure 3.15, the moduli of the one month old field cores roughly doubled after drying for three days at 40 °C and then reduced roughly by half after soaking in water.

Note that all the full-length cores obtained to date along the outer edge line indicate an FBS thickness in excess of the 150 mm design thickness (Figure 3.13). There is a need for additional coring in the traffic lane to confirm the constructed thickness.

200 mm


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Table 3.6: Modulus and density of early-life field cores

Date of coring Chainage Offset Upper or lower

portion

Bulk dry density (t/m3)

Indirect tensile modulus (MPa) at 25 °C As

received from

roadbed

Cured dry modulus(1)


% wet/dry modulus

12 March 2013 Eight days after construction

15 Outer edge line Upper 2.15 2540 4920 3470 70 15 Outer edge line Lower 2.04 1910 4060 2540 63 35 Outer edge line Upper 2.06 3690 6510 4560 70 35 Outer edge line Lower 1.99 1700 3670 2130 58 55 Outer edge line Upper 2.15 3170 6930 1960 28 75 Outer edge line Lower 2.16 4470 7540 3940 52 75 Outer edge line Upper 2.03 1750 4060 1900 47 95 Outer edge line Upper 2.22 4190 9360 3490 37

3 April 2013 One month after construction

20 Outer edge line Upper 2.13 2540 5980 4300 72 20 Outer edge line Lower 1.99 1910 4130 2820 68 40 Outer edge line Upper 2.11 3690 8520 4310 51 40 Outer edge line Lower 2.01 1700 2920 2620 90 60 Outer edge line Upper 2.13 3170 5300 2770 52 60 Outer edge line Lower 2.02 – 1830 1890 103 80 Outer edge line Upper 2.06 4470 3530 2590 73 80 Outer edge line Lower 1.98 1750 1790 1700 95

1 Dried for three days at 40 °C before modulus testing at 25 °C. 2 After drying for three days at 40 °C, cores were soaked in water for 10 minutes under vacuum of 95 kPa then tested for modulus at 25 °C.

Figure 3.14: Variation in field core modulus with density

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

1.98 2.00 2.02 2.04 2.06 2.08 2.10 2.12 2.14 2.16 2.18 2.20 2.22 2.24

Indirecttensile

modulus (MPa)

Dry density (t/m3)

Field cores 8 days

field core 1 month

Downer mix design - initial

TMR mix design(density unknown)cured: 8800 MPasoaked: 5100 MPa

Servopac compactedlab specimencured 3 days at 40°C

Servopac compactedlab specimencured 3 days at 40°C then soaked


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Figure 3.15: Effect of laboratory drying and soaking on one month field core moduli

3.8.3 Rutting and Roughness On 10 April 2013, about five weeks after construction of the FBS crushed rock base, the rutting and roughness of the two sections were measured with a laser profiler.

The rutting results are shown in Figure 3.16. As mentioned in Section 3.6.1, the pavement ravelled and rutted when trafficked overnight prior to sealing. Note particularly the high rutting of the inner wheelpath. During construction, considerable effort was applied to the inner wheelpath to achieve a tight FBS base surface suitable for bituminous sealing. This reworking of the base may have led to an excess of fines on the surface or higher moisture contents resulting in early-life ravelling and rutting. By comparison, the area in the vicinity of the outer wheelpath did not require the same effort to prepare and showed significantly lower ravelling and rutting.

Note this rutting occurred despite the mix design indicating the initial modulus of Marshall compacted specimens (Table 3.7) achieving the minimum 700 MPa required by the TMR mix design method. TMR have advised this is contrary to their experience.

The roughness results were as follows:

FBS section: lane IRI of 2.1 m/km

asphalt section: lane IRI of 3.6 m/km.

Note, however, the roughness results only apply to short (< 100 m) sections, are influenced by construction joints and as such are not a reliable indicator of performance.

y = 2.267x - 513

y = 0.655 + 1625

1000

2000

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5000

6000

7000

8000

9000

10000

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

1000 1500 2000 2500 3000 3500 4000 4500 5000

Modulus after

curing(MPa)

Modulus as received from field (MPa)

After 3 days curing at 40C, dry modulus

After 3 days curing at 40C then soaking, wet modulus


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Figure 3.16: Rutting five weeks after construction of the FBS pavement

3.9 Effect of Temperature on Moduli In the research project, surface deflections are being monitored on various projects to evaluate the extent to which the modulus changes with time and traffic loading. As the FBS material can differ in temperature between deflection measurements, a procedure is required to adjust the measured deflections from the pavement temperature at the time of deflection measurement to the WMAPT. A procedure similar to the adjustments currently in use for asphalt (Austroads 2011a) would be appropriate.

To assist in this regard, after three days drying at 40 °C, the one month field cores were tested for indirect tensile modulus over a range of temperatures. The results are plotted in Figure 3.17. The modulus variation is consistent with the FBS modulus variation given in the Guide to Pavement Technology Part 5 Pavement Evaluation and Treatment Design (Austroads 2011a).

The variation of modulus with temperature appears to be about 1/3rd the asphalt modulus variation provided in the Guide to Pavement Technology Part 2 Pavement Structural Design (Austroads 2012).

As an interim measure pending further research, it is proposed that the asphalt deflection and curvature adjustment factor in Part 5 (Austroads 2011a) be used for FBS pavements but with the ratio of WMAPT to the measured temperature (Tmeas) adjusted to reflect the lower temperature dependency. The adjusted WMAPT/Tmeas ratios are shown in Figure 3.18.

In the case of pavements with asphalt surfacing on the FBS layer, the adjustment varies according to the ratio of FBS layer thickness to the total thickness of the asphalt and FBS layers. In using the charts in Part 5, the total thickness of asphalt and FBS layers is used with the adjusted WMAPT/Tmeas ratio.

0

2

4

6

8

10

12

14

16

18

20

22

0 20 40 60 80 100 120 140 160 180 200

Rut depth(mm)

Chainage (m)

Inner wheel path

Outer wheel path

Foamed bitumen stabilised crushed rock base Dense graded asphalt


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Figure 3.17: Modulus variation with temperature

Figure 3.18: Correction of WMAPT to measured temperature ratios

0

2000

4000

6000

8000

10000

12000

10 12 14 16 18 20 22 24 26 28 30

Indirect tensile

modulus(MPa)

Temperature (°C)

20m top portion

20 m bottom portion

40 m top portion

40 m bottom portion

60 m top portion

60 m bottom portion

80 m top portion

80 m bottom portion

Mean

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6

WMAPT/Tmeas for use in

deflection/curvatureadjustment

WMAPT/Tmeas at time of deflection measurements

FBS with sprayed seal surface

FBS thickness 90% of total thickness





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3.10 Effect of Laboratory Compaction Method on Modulus As described in Section 3.4, two experienced laboratories measured very different moduli in the mix designs prior to construction. It was of interest to evaluate the extent to which this was due to the specimen compaction method, namely:

Downer Infrastructure mix design specimens were compacted using gyratory (Servopac) compaction in 150 mm diameter moulds.

TMR mix design specimens were compacted in 150 mm diameter moulds using a 9.9 kg Marshall hammer with a modified compaction foot.

Samples of the foamed stabilised crushed rock base were obtained from the roadbed prior to field compaction. They were quickly transported to Downer’s laboratory and the following specimens prepared:

four specimens compacted in a 100 mm diameter mould using 50 blows of a 4.5 kg Marshall hammer each end

four specimens compacted in a 100 mm diameter mould using gyratory (Servopac) compaction to a target wet density of 2.26 t/m3

six specimens compacted in a 150 mm diameter mould using gyratory (Servopac) compaction to a target wet density of 2.26 t/m3.

The measured initial, cured dry and cured wet moduli are given in Table 3.7. The cured dry moduli are plotted in Figure 3.19.

Clearly, most of the difference in mix design moduli between the two laboratories appears to be due to the method of compacting test specimens. This reinforces the need to harmonise test methods nationally.

Figure 3.19: Modulus variation with compaction method

1000

2000

3000

4000

5000

6000

7000

8000

2.14 2.15 2.16 2.17 2.18 2.19 2.2 2.21 2.22 2.23 2.24 2.25 2.26 2.27

Indirect tensile modulus

(MPa)

Dry density (t/m3)

101 mm mould, Marshall hammer

100 mm mould, Servopac

150 mm mould, Servopac


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Table 3.7: Effect of compaction method on modulus

Compaction method Sample number

Bulk dry density (t/m3)

Indirect tensile modulus (MPa) at 25 °C Initial



% wet/dry modulus

100 mm diameter mould, Marshall hammer

M1 2.15 1090 6410 2740 43

M2 2.16 1070 6800 2780 41

M3 2.18 – 6980 3160 45

M4 2.15 – 6900 3280 48

100 mm diameter mould, gyratory compaction to a target wet density

S1 2.17 700 3260 1660 51

S2 2.19 510 2360 1230 52

S3 2.19 – 2660 1670 63

S4 2.20 – 2770 1730 62

150 mm diameter mould, gyratory compaction to a target wet density

1 2.26 700 5900 3240 55

2 2.23 640 5740 3040 53

3 2.23 610 5710 2930 51

4 2.23 – 5620 3130 56

5 2.23 – 5380 2920 54

6 2.23 – 5290 2910 55

1 Cured unsealed for three hours at 25 °C. 2 Cured unsealed for three days at 40 °C. 3 Soaked in water under vacuum of 95 kPa for 10 minutes at 25 °C.

3.11 Traffic Monitoring VicRoads provided the current design values of AADT and %HV for the Woodend section of Calder Freeway as given in Table 3.8.

Table 3.8: Traffic volume for the Calder Freeway northbound carriageway

Year Total heavy vehicles(1) Number of survey days Estimated annual number of heavy vehicles

Annual ESA

2011 3.5 x 105 343 3.7 x 105 8.3 x 105 2012 3.8 x 105 343 4.0 x 105 9.0 x 105

1 Total heavy vehicles assumes all ‘rejected’ and ‘unknown vehicles are heavy vehicles. Source: Gisborne Culway site data supplied by VicRoads. Table 3.9 lists the average Equivalent Standard Axles (ESA) per heavy vehicle derived from the weigh-in-motion (WIM) site on Calder Freeway northbound carriageway near Gisborne (which is 14 km from the Woodend trial section). Based on this data, an average of 2.5 ESA per heavy vehicle was assumed. Assuming 90% of the heavy vehicles travel in the slow lane, the estimated annual traffic loading is 9.0 x 105 ESA.


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Table 3.9: Results of average ESA per heavy vehicle Calder Freeway northbound carriageway

Survey period Average ESA per HV July 2012–December 2012 2.52 January 2012–June 2012 2.38

July 2011–December 2011 2.44 January 2011–June 2011 2.48

Source: Gisborne Culway site data supplied by VicRoads.

3.12 Performance Prediction A key objective of the project is to improve the Austroads interim thickness design procedure (Austroads 2011a).

As described in Section 3.5, a preliminary prediction has been made of the allowable traffic loading using the interim method: for a 150 mm thick FBS the predicted fatigue life of the FBS is 6.6 x 105 ESA at 50% design reliability. As discussed in Section 3.10, the estimated annual traffic loading is about 9 x 105 ESA. Consequently, the design model predicts there is a 50% chance of observing FBS fatigue cracking within 12 months.

Note that cores taken along the outer edge line indicated FBS thicknesses of 200 mm or more, well above the 150 mm design thickness. If the FBS fatigue life is predicted for 200 mm thickness of FBS and the in situ subgrade modulus of 50 MPa rather than 20 MPa, the predicted fatigue life increases to 2.3 x 106 ESA at 50% design reliability. In this case the design model predicts there is a 50% chance of observing FBS fatigue cracking after about 2–3 years of trafficking.

Clearly before the end of the project the constructed FBS thickness in the wheelpaths will need to be measured to provide feedback on the structural design method. To provide a better understanding of an appropriate design modulus for the subgrade, in the future layer moduli will be back-calculated from FWD surface deflections.

It is planned to monitor this pavement section over the next three years to provide detailed data on pavement performance (surface defects, cracking, rutting, roughness, deflection). In March 2014, 12 months after construction, FWD testing and coring between the wheelpaths will also be undertaken to evaluate FBS thickness and modulus development. Coring in the wheelpaths will be delayed until 2014–15 to limit the influence of coring on the pavement performance.


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4 PORT WAKEFIELD ROAD VIRGINIA

4.1 Introduction About 1 km length of the northbound carriageway slow lane of Port Wakefield Road, Virginia, South Australia was foamed bitumen stabilised in April 2011. The project comprises the following three pavement sections:

a control asphalt section (75 m long between chainages 0–75 m) comprising 100 mm dense graded asphalt on granular base and subbase

an under-designed sub-section (75 m long between chainages 75–150 m) comprising 150 mm thick FBS base with a two-coat seal surfacing

a main section (900 m long between chainages 150–1067 m) constructed with 200 mm thick FBS base with a two-coat seal surfacing.

Details of locality and job statistics (job size, FBS specification and construction method) for the Port Wakefield Road FBS pavement sections are given in Table 4.1.

Table 4.1: Description of the Port Wakefield Road FBS pavements

Location Port Wakefield Road, Virginia, South Australia, between Angle Vale Road and Park Road Job size Length Nominal 150 mm thickness FBS: chainages 75–150 m

Nominal 200 mm thickness FBS: chainages 150–1067 m Number of lanes 1 (northbound outer lane) Lane width 3.5 m (stabilisation width 3.9 m) Stabilisation depth Nominal 150 mm and 200 mm FBS base Wearing course 16/7 mm double seal


Mix design Empirically-based method Host materials Calcrete limestone crushed rock PM1/PM2 Foamed bitumen 3.0% class 170 bitumen Supplementary binder 1% hydrated lime Foaming agent Not recorded

Construction method

Work specifications and QA testing DPTI Specification: Part 224 Foamed Bitumen Pavement (January 2007) Construction date April 2011

Figure 4.1 shows the test site prior to stabilisation. Only the outer lane was stabilised with hydrated lime and foamed bitumen.


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Source: Personal communication Crosley (2012).

Figure 4.1: Port Wakefield Road FBS site before stabilisation

4.2 Site Investigation Prior to Stabilisation Prior to stabilisation, coring and sampling of the pavement and subgrade materials was undertaken at two locations (chainages 100 m and 125 m, and 1.75 m from the outer edge line) and dynamic cone penetrometer (DCP) testing of the subgrade was also performed. The results indicated that the unbound granular pavement was uniform and had a total pavement thickness in the range of 480–500 mm, which included:

14 mm/7 mm sprayed seal

160 mm calcrete limestone crushed rock base

190 mm size 60 mm quartzite sandstone rubble subbase

150 mm size 75 mm calcrete limestone rubble subbase

subgrade clay, estimated in situ CBR in the range 9–20% (Table 4.4).

4.3 Mix Design The material collected from the roadbed was identified as crushed calcrete limestone, with a particle size distribution complying with DPTI requirements for crushed rock base and PI less than 6%. Accordingly, the material was suitable for foamed bitumen stabilisation.

For this job, DPTI specified a 3.0% residual bitumen and 1.0% hydrated lime in the FBS process based on previous experience.

The material has been sent to ARRB for laboratory testing to determine FBS design modulus later in the project.


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4.4 Thickness Design The 200 mm thickness of FBS was used for the main section (900 m long between chainages 150–1067 m), whilst a nominal 150 mm thickness of FBS was used for the 75 m long under-designed section to increase the probability of pavement distress within the next three years.

Table 4.2 shows the pavement structures of the two sections (nominal FBS thicknesses of 150 mm and 200 mm) and the selected design modulus values used to predict the allowable loading using the interim FBS thickness design procedure (Austroads 2011a).

In the interim method, the FBS design modulus is determined from indirect tensile moduli measured on laboratory-manufactured specimens cured for three days at 40 °C and then soaked in water under vacuum of 95 kPa for 10 minutes. These cured wet moduli are overly conservative moduli compared to the field cores as illustrated from the Calder Freeway (Section 3.8.2).

For the Port Wakefield Road project a mix design was not undertaken, so cured dry moduli were not available. It is noted from the Calder Freeway project, that for a given density the cured dry moduli were about half the field core moduli. For the 200 mm thick FBS section, the mean field core modulus was about 5000 MPa at a temperature of 25 °C. Hence the cured dry modulus of laboratory specimens at the field density was estimated to be 2500 MPa at 25 °C. Adjusting this cured dry modulus to a WMAPT of 27 °C and for a design traffic speed of 80 km/h, an FBS design modulus of 2200 MPa was calculated for the 200 mm FBS section. For the 150 mm FBS, a design modulus of 3100 MPa was calculated in the same manner. Later in the project, a mix design will be undertaken to provide a more accurate estimate of the FBS design moduli.

Based on this data set, the following FBS fatigue lives were predicted:

nominal 150 mm thickness: 2.3 x 106 ESA at 50% design reliability

nominal 200 mm thickness: 3.5 x 106 ESA at 50% design reliability.

Table 4.2: Data used to predict the FBS fatigue life of Port Wakefield Road sections

Pavement component

Design parameter

Available data Technical basis for data selection

Subgrade Type Clay, in situ CBR 9% In situ DCP testing Table 4.4 Design modulus 90 MPa

Subbase Thickness Nominal 150 mm FBS: 350 mm Nominal 200 mm FBS: 300 mm

Normal granular base/subbase as per original design

Design modulus of top sublayer

Nominal 150 mm FBS: 240 MPa Nominal 200 mm FBS: 185 MPa

Austroads Guide to Pavement Technology Part 2 Table 6.4 (Austroads 2012)

FBS base Thickness Nominal 150 mm FBS: 130 mm Nominal 200 mm FBS: 170 mm

Field cores (Table 4.5)

Design modulus Nominal 150 mm FBS: 3100 MPa Nominal 200 mm FBS: 2200 MPa

From Calder Freeway results, assumed that dry modulus of laboratory compacted specimens is half the modulus of field cores at the same density

Volume of binder Nominal 150 mm FBS: Vb = 9% Nominal 200 mm FBS: Vb = 7%

Based on the measured bitumen content of cores (Table 4.6 and Table 4.7)

Wearing course Thickness n.a. Double spray seal Design modulus n.a.


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4.5 Pavement Construction 4.5.1 Foamed Bitumen Stabilised Sections The pavements were constructed between 11–15 April 2011 in accordance with the DPTI specification (DPTI 2007). The details of stabilisation and compaction equipment and construction tolerances are as follows:

The Wirtgen WR2000 stabiliser (Figure 4.2) was used and the construction tolerance for the application rate for the binder and supplementary binder was ±10% of the specified values.

The depth of stabilisation was measured to the nearest 5 mm for conformation against the requirements of the DPTI specification (2007). These measurements were taken along the construction joint between the slow and fast lane. As discussed later, this process did not reflect the lower stabilisation thickness subsequently obtained from coring the pavement.


Figure 4.2: Stabilisation equipment used at the Port Wakefield Road FBS site

Compaction equipment included (a) a vibrating padfoot roller of a mass of 12 t; (b) a vibrating smooth drum roller with a mass of 12 t; and (c) a multi-tyre roller with a mass of 15 t (Figure 4.3). The stabilised pavement layers were compacted uniformly to the full depth and over the full width and to the relative density of not less than 98% Modified maximum dry density (MDD) (Table 4.3).


Figure 4.3: Compaction equipment used at the Port Wakefield Road FBS site


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Stabilisation of the nominal 150 mm thick FBS section (chainage 75–150 m) commenced 11 April 2011, the sprayed seal was mixed through the crushed rock base, the hydrated lime was added and then the foamed bitumen. The pavement was subsequently sealed four days later, 15 April 2011.

In terms of the 200 mm thick FBS section between chainage 150–1067 m, the stabiliser could only pulverise, wet mix and lime treat a 425 m long section on 11 April 2011 due to the presence of a pavement patch of what was considered at the time cement treated crushed rock between chainage 509–573 m. This was subsequently found to be an asphalt patch (Section 4.6) and caused excessive wear to the milling teeth. The following day, 12 April 2011, the remaining length (575–1067 m) was pulverised, wet mixed and lime treated, and an asphalt patch was encountered between chainage 780–845 m which again hindered progress.

The hydrated lime spread rate was measured during construction as 2.6 kg/m2 for the nominal 150 mm section compared to the design value of 3.0 kg/m2. For the nominal 200 mm thick FBS section the measured spread rate was 4.0 kg/m2 compared to the design value of 4.1 kg/m2.

On 13 April 2011, the nominal 200 mm thick FBS between chainages 150–1067 m was foamed bitumen stabilised. It is not known whether the delay between lime stabilisation and foamed bitumen stabilisation affected the subsequent performance.

Due to rain on 14 April 2011, the application of the two-coat sprayed seal surface was delayed until 15 April 2011.

After the FBS was compacted, the in situ densities were measured to a depth of 150 mm and material excavated at selected test sites to determine the Modified maximum dry density (MDD) and optimum moisture content (OMC) (Table 4.3). The relative density at each site was calculated by dividing the in situ dry density by the Modified MDD.

Table 4.3: Field dry densities and laboratory maximum dry densities

Chainage (m)

Field dry density (t/m3)

Modified MDD (t/m3)

Modified OMC (%)

Relative density (%)

122 2.04 2.03 7.0 100.0

196 1.98 1.98 9.0 100.0

352 1.98 1.95 9.0 102.0

431 2.01 1.93 9.0 104.0

487 2.06 2.01 6.0 102.5

591 2.02 2.01 8.0 100.5

711 2.02 1.99 8.0 101.0

838 1.98 2.02 7.0 98.5

1007 2.05 2.02 7.5 101.0

4.5.2 Asphalt Section To benchmark the FBS performance, it was decided to construct a 100 mm thick asphalt inlay of a short length of Port Wakefield Road adjacent to the 150 mm thick FBS section.

The 100 mm thick asphalt section was constructed by milling the existing pavement to a depth of 100 mm, spraying a tack coat and placing the asphalt in two layers (40 mm wearing course, 60 mm thick intermediate course) (Figure 4.4). Following common local practice, a tack coat was not placed between the two asphalt layers as both layers were placed on a single day.


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Figure 4.4: 100 mm thick dense graded asphalt inlay

4.6 Visual Condition Monitoring DPTI has inspected the pavement about every two months since construction. In January 2012, the first summer after construction, flushing was observed over a 30 m length of the 200 mm FBS section length, chainage 510 to 575 m. By March 2013 after the second summer and about two years of trafficking, the rutting was up to about 50 mm deep in some areas (Figure 4.5). Coring of the pavement showed that this area of the pavement was an asphalt patch prior to stabilisation. This was thought to be a cement stabilised patch during construction. Foamed bitumen stabilisation of this asphalt patch resulted in a mix with inadequate rut resistance.

Figure 4.5: Rutting due to foamed bitumen stabilisation of an old asphalt patch

On 23 August 2012, fatigue cracking was observed for the first time. Two months later, October 2012, a detailed inspection of the asphalt section, the nominal 150 mm FBS and 200 mm thick FBS sections was undertaken. Fatigue cracking was observed in all three sections.

The cracking of the FBS section starts as fine transverse cracks in the wheel patch and develops into block cracking (Figure 4.6).

Fine transverse cracking was also observed in the 100 mm thick asphalt section (Figure 4.6).


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Example of fine transverse cracking of nominal 150 mm FBS Example of crocodile cracking of nominal 200 mm FBS

Figure 4.6: Example of cracking observed in FBS section, after about 18 months of trafficking

4.7 Pavement Investigation As a result of the premature pavement distress, in October 2012 FBS cores were extracted from the pavement and dynamic cone penetrometer testing of the subgrade was undertaken to estimate in situ Californian Bearing Ratio (CBR) using the Austroads (2012) method. Dynamic cone penetrometer testing was also undertaken during construction in April 2011.

4.7.1 Asphalt Section The asphalt section was cored at chainage 62.6 m in the outer wheelpath and between wheelpaths in an area with fine fatigue cracking (Figure 4.7).

While the core from the unloaded area between wheelpaths was extracted with the upper and lower asphalt layers bonded together, in the outer wheelpath the 40 mm thick wearing course was debonded from the underlying asphalt (Figure 4.7). As the cracking appeared to be confined to the wearing course, the cracking may have been due to inadequate bonding between asphalt layers. The two asphalt layers were placed on the same day and without trafficking of the intermediate course. Following normal local practice, a tack coat was not applied to the surface of the intermediate course prior to the placement of the overlying wearing course.

As shown in Table 4.5 and as expected, the cracked wearing course asphalt from the outer wheelpath was significantly lower in modulus than sound asphalt from the unloaded area between wheelpaths.

As shown in Table 4.4, the subgrade has high strength with an estimated in situ subgrade CBR exceeding 10%.


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Lower portion of delaminated outer wheelpath core Core between wheelpaths, bonding between asphalt layers

Figure 4.7: Port Wakefield Road asphalt coring

Table 4.4: Estimated in situ subgrade CBR

Section Description Chainage (m)

Offset Date Estimated CBR (%) at depths below top of subgrade

0–100 mm

100–200 mm

200–300 mm

300–400 mm

Asphalt BH (during construction) 37.5 April 2011 6 5 5 8

BH1 62.6 BWP October 2012 > 30 11 13 15

FBS nominal 150 mm thick

BH (during construction) 100 April 2011 6 11 14 14

BH2 101 BWP October 2012 11 18 28 30

BH (during construction) 125 April 2011 18 25 6 7

BH4 122 BWP October 2012 > 30 > 30 15 11

BH6 144.5 OWP October 2012 13 30 > 30 n.a


BH8 420 BWP October 2012 11 11 15 n.a

BH11 820 BWP October 2012 11 11 15 n.a

BH12 950 BWP October 2012 7 12 15 n.a


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Table 4.5: Laboratory test results of Port Wakefield cores

Section Description Chainage (m)

Offset Thickness (mm) Underlying asphalt patch

Core diameter

(mm)

Core length (mm)

Bulk density (t/m3)

IT strength (kPa)

IT modulus

(MPa) FBS Asphalt

Asphalt BH1, asphalt wearing course 62.6 OWP – 90 No 99 40 2.23 1 990 1 980

BH1, asphalt intermediate course 62.6 OWP – 90 No 99 40 2.24 1 570 7 750

BH1A, asphalt wearing course 62.6 BWP – 90 No 99 37 2.21 1 830 9 000

BH1A, asphalt intermediate course 62.6 BWP – 90 No 99 35 2.25 2 070 9 160


BH2, top layer 101 BWP 140 – No 142 78 2.10 770 7 550

BH3 112 BWP 130 – No 142 76 2.06 760 6 890

BH4 122 BWP 140 – No 142 76 2.09 920 7 520

BH5 131 BWP 130 – No 142 77 2.07 770 6 250

BH6 144.5 OWP 110 – No 142 70 2.09 720 5 290


BH7 200 BWP 150 – No 142 74 2.02 430 2 760

BH8, top layer 420 BWP 180

– No 142 60 1.97 590 5 190

BH8, bottom layer 420 BWP – No 142 68 1.88 350 2 220

BH9 660 BWP 160 – No 142 83 2.04 980 7 880


– Yes 142 74 2.04 930 11 430

BH10, bottom layer 750 BWP – Yes 142 64 1.94 390 3 250


– Yes 142 78 2.11 810 6 430

BH11, bottom layer 820 BWP – Yes 142 77 2.40 1 300 9 750


– No 142 73 2.09 450 5 560

BH12, bottom layer 950 BWP – No 142 78 1.99 230 1 070


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4.7.2 FBS Sections Nominal 150 mm thick FBS

Four FBS cores were taken from the untrafficked area between wheelpaths and one core was taken in the outer wheelpath. The average FBS thickness was 130 mm, less than the 150 mm design thickness.

The cores were transported to ARRB’s laboratory in Vermont South for testing. About 30 mm was sawn from the top and bottom of each core and the remaining 70–78 mm length was tested from indirect tensile modulus and strength. The moduli were high, the average of the indirect tensile moduli in Table 4.2 was 6700 MPa. Figure 4.8 shows three of the five cores obtained and the pavement condition at time of coring.

BH 3 chainage 111 m BH4 chainage 121 m BH6 chainage 144.5 m

Figure 4.8: Cores obtained from the nominal 150 mm thick FBS section

Following modulus and strength testing, the particle size distribution and the recovered bitumen content of the cores were measured. The bitumen contents were measured using the pressure filter method (AS 2891.3.3) with Solvex MT solvent. The results are given in Table 4.6.

The design bitumen content of 3.0% equates to application rates of 9.1 kg/m2 and 12.2 kg/m2 for stabilisation depths of 150 mm and 200 mm respectively, assuming an in situ dry density of 2.03 t/m3. The average measured bitumen content was 5.1% considerably higher than the design content of 3.0%. The high bitumen contents may have been due to:

the use of the bitumen application calculated for nominal 200 mm FBS depth on the shorter section where the depth was reduced to a nominal 150 mm

the stabilisation depths being below the 150 mm design thickness

the inclusion of the old double seal in the recycled pavement.


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The variation in measured bitumen content with stabilisation depth is illustrated in Figure 4.9. Also shown are the bitumen contents for the design bitumen application rate of 9.1 kg/m2 and for 12.2 kg/m2. Considering the old double seal added an additional 1.5 to 2.0 kg/m2 of bitumen, the measured bitumen contents are consistent with use of an application rate of 12.2 kg/m2 for the nominal 150 mm stabilisation depth. That is, the results suggest the use of the 200 mm thick FBS bitumen application rate on the 150 mm thick FBS section.

The high bitumen content may have contributed to the higher densities for the nominal 150 mm FBS section and hence the higher moduli as shown in Figure 4.10. Even though these high bitumen contents are high, generally the rutting is not yet excessive (Figure 4.17).

Table 4.6: Particle size distribution and bitumen content of field cores obtained in nominal 150 mm thick FBS section

Sieve size % passing sieve BH2 BH3 BH4 BH5 BH6

19.0 mm 100 100 97 98 100

13.2 mm 97 96 95 95 89

9.5 mm 87 85 84 83 74

6.7 mm 74 75 72 73 61

4.75 mm 62 62 60 60 49

2.36 mm 46 46 45 45 35

1.18 mm 35 35 34 34 28

600 µm 28 27 26 27 23

300 µm 22 21 20 22 19

150 µm 16 15 15 17 15

75 µm 11 10 9 12 11

Recovered bitumen content 5.1% 4.4% 5.7% 4.8% 5.7%

Stabilisation depth (mm) 140 130 140 130 110

Chainage (m) 101 112 122 131 144.5

Figure 4.9: Measured bitumen contents of nominal 150 mm FBS cores compared to design application rates

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

100 110 120 130 140 150 160 170 180 190 200

Bitumencontent

(% by mass)

Depth of FBS stabilisation (mm)

Application rate 9.1 kg/m2

Application rate of 12.2 kg/m2

Measured


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Nominal 200 mm thick FBS

Six FBS cores were taken from the untrafficked area between wheelpaths. The average thickness was 179 mm, below the 200 mm design thickness.

The cores were transported to the ARRB laboratory in Vermont South, Melbourne for testing. For cores less than 160 mm in length (BH7, BH9) about 30 mm was sawn from the top and bottom of each core and the remaining 73–84 mm length was tested for indirect tensile modulus and strength testing. Cores from the other sites were cut into top and bottom halves prior to testing for density, modulus and strength testing.

As shown in Figure 4.10, the moduli tended to increase with density and the FBS layer tended to have lower density and moduli in the bottom portion compared with the top portion, consistent with the Calder Freeway findings (Figure 3.14).

Figure 4.10: Variation in field core moduli with density

The very high modulus of cores from BH11 appears to be due to the host material being an old asphalt patch. Note that at BH11, the FBS material was well supported by the underlying old asphalt patching material (Figure 4.11). Due to this support, the density and modulus of the bottom half of the layer was higher than other locations.

Figure 4.11: BH11 core, FBS of an asphalt patch together with underlying asphalt patching material

0

2000

4000

6000

8000

10000

12000

1.86 1.88 1.90 1.92 1.94 1.96 1.98 2.00 2.02 2.04 2.06 2.08 2.10

Indirect tensile modulus

(MPa)

Density (t/m3)

150 mm FBS200 mm FBS bottom200 mm FBS top


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For this material, the measured relationship between indirect tensile modulus of field cores from indirect tensile strength is shown in Figure 4.12. The strength and modulus results were highly correlated.

Figure 4.12: Relationship between indirect tensile strength and modulus

Following modulus and strength testing, the particle size distribution and the recovered bitumen content of the cores were measured. The results are given in Table 4.7.

Table 4.7: Particle size distribution and bitumen content of field cores obtained in nominal 200 mm thick FBS section

Sieve size % passing sieve BH7 BH8

top BH8

bottom BH9 BH10

top BH10

bottom BH11 top

BH11 bottom

BH12 top

BH12 bottom

19.0 mm 95 95 100 99 99 96 100 89 93 100

13.2 mm 86 93 93 93 93 92 99 78 84 91

9.5 mm 67 84 80 81 81 81 93 68 71 78

6.7 mm 57 73 69 67 67 69 84 62 61 67

4.75 mm 48 62 56 55 54 60 72 49 50 57

2.36 mm 36 46 46 40 37 45 55 38 37 44

1.18 mm 29 36 38 30 26 34 43 30 29 32

600 µm 24 29 32 24 20 27 34 24 23 24

300 µm 20 24 27 18 14 21 25 16 19 17

150 µm 16 18 21 13 10 15 16 8 14 12

75 µm 12 12 14 8 5 9 10 5 9 7

Recovered bitumen content 4.4% 5.5% 6.6% 5.3% 3.1% 4.3% 8.1% 3.8% 3.4% 2.8%

Stabilisation depth (mm) 150 180 160 180 175 190

Chainage (m) 200 420 660 750 820 950

y = 8.59xR² = 0.80

0

2000

4000

6000

8000

10000

12000

0 200 400 600 800 1,000 1,200 1,400

Indirecttensile

modulus (MPa)

Indirect tensile strength (kPa)


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The average measured binder content was 5.4%, well above the 3% design content. The recovered binder contents were not highly correlated with the length of the field cores (Figure 4.13). The high bitumen content of core BH11 was due to the stabilisation of an old asphalt patch (Figure 4.11). As the sprayed seal surfacing of the original unbound granular pavements was included in the FBS material, this may also have contributed about an additional 0.5% to the measured bitumen contents. However, the very high bitumen contents at BH8 and BH9 cannot be explained, other than these again being FBS stabilisation of old asphalt patches.

Figure 4.13: Measured bitumen contents of nominal 200 mm FBS cores compared to design application rate

Figure 4.14 shows the very different appearance of the BH8 material from the material at BH12 consistent with the difference in measured bitumen contents. Also shown are the severities of surface cracking at the time of coring. Given that BH10 and BH12 had bitumen contents close to the design value yet had very different severities of cracking, it cannot be concluded that there is a close link between the cracking and the bitumen content being well above the design value.

2.5

3.0

3.5

4.0

4.5

5.0

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6.5

100 110 120 130 140 150 160 170 180 190 200

Bitumencontent

(% by mass)

Depth of FBS stabilisation (mm)

Application rate of 12.2 kg/m2

Application rate of 12.2 kg/m2 plus old seal (1.8 kg/m2)

Measured

BH7

BH8

BH12

BH9

BH11 - asphalt patch

BH10


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BH8 chainage 420 m BH10 chainage 750 m BH12 chainage 950 m

Figure 4.14: Cores extracted from the nominal 200 mm thick FBS section

4.8 Pavement Deflections Surface deflections were measured using a Falling weight deflectometer (FWD) at the following times:

1 March 2012, about 11 months after construction

27 September 2012, about 17 months construction.

The deflection bowls were measured using a contact stress in the range 550–580 kPa then normalised to a stress of 566 kPa.

The maximum deflections (D0) and curvatures (D0–D200) normalised to a stress of 566 kPa are plotted in Figure 4.15.


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Figure 4.15: Port Wakefield Road measured surface deflections

Although the pavement surface temperatures were measured (Figure 4.16), the temperatures at depth are required to correct the deflection measured on FBS from the testing temperature to a representative in-service temperature. Note that the surface temperature increase with chainage measured in September 2012 reflected the surface heating during the morning of testing. Given this variability it was not possible to accurately estimate the mid-layer pavement temperatures from surface temperatures. Accordingly, the process developed in Section 3.9 to correct deflections to the WMAPT was not used.

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0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 100010501100

Maximum deflection at 566 kPa

(mm)

Chainage

Asphalt control March 12150 mm FBS March 12200 mm FBS March 12Asphalt control Sept 12150 mm FBS Sept 12200 mm FBS Sept 12

Previousasphalt patch Previous

asphaltpatch

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Curvature at

566 kPa(mm)

Chainage

Asphalt March 12150 mm FBS March 12200 mm FBS March 12Asphalt control Sept 12150 mm FBS Sept 12200 mm FBS Sept 12

Previous asphalt patch

Previous asphalt patch


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Figure 4.16: Pavement surface temperatures during FWD measurements

In March 2012, no cracking was observed by DPTI staff driving over the site, but six months later distress was apparent in all sections. As seen from Figure 4.15, the deflections and curvatures of the nominal 200 mm thick FBS section generally increased during this six month period, consistent with the onset of cracking. Despite the high strength subgrade and thickness of underlying granular subbase, the curvatures 12 months after construction were high (> 0.1 mm) compared to other sites being monitored. A possible reason for this is fatigue damage to the FBS layers in the first 12 months of trafficking, despite surface cracking not being observed. However, not known is the extent to which the increase in surface temperature between the March and September 2012 deflection measurements resulted in the observed increases in deflections and curvatures.

As part of the 2013–14 project work, consideration will be given to measuring both the pavement temperatures and the surface deflections to evaluate the layer moduli if a section with more commonly used bitumen contents (3–4%) can be identified by pavement coring.

4.9 Rutting and Roughness In May 2013, the rutting and the roughness of the project were measured.

The 1.2 m straight edge rut depths are given in Figure 4.17. The high rutting in the vicinity of chainage 550 m was due the stabilisation of an old asphalt patch (Figure 4.5).

The lane IRI roughness values are plotted in Figure 4.18.

10

15

20

25

30

35

40

45

0 100 200 300 400 500 600 700 800 900 1000 1100

Surface temperature

(°C)

Chainage (m)

Mar-12

Sep-12


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Figure 4.17: Port Wakefield Road rut depth measurements May 2013

Figure 4.18: Port Wakefield Road roughness measurements May 2013

0

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15

20

25

30

35

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1

Rut depth (mm)

Chainage (km)

Outer wheel path

Inner wheel path

asphalt 150 mm FBS

1.6

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Lane IRI

(m/km)

Chainage (km)


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4.10 Traffic Monitoring DPTI provided 7-day vehicle classification count data (two-way) for the Port Wakefield Road (at a traffic count site located 1.7 km south of the Angle Vale Road) for two periods in July 2006 and August 2011 (DPTI 2011). Table 4.8 provides a summary of the daily number of heavy vehicles.

Table 4.8: Traffic data on Port Wakefield Road 1.7 km south of Angle Vale Road

Year Northbound average daily heavy vehicles

Annual ESA

2006 745 9.8 x 105 2011 1240 1.6 x 106

Weigh-in-motion (WIM) axle load data is not available at this site to estimate the number of ESA per heavy vehicle and hence the cumulative traffic loading. However, DPTI suggested an estimated value of the average number of ESA per heavy vehicle of 3.6 for the outer lane of the Port Wakefield Road based on WIM data collected on similar road sites (personal communication Crosley 2012). Hence the current estimated annual traffic loading is 1.6 x 106 ESA assuming all heavy vehicles travel in the slow lane. Over the 16 month period between construction in April 2011 and the first observation of fatigue cracking (August 2012), the cumulative traffic loading is estimated to be 2.1 x 106 ESA.

4.11 Comparison of Observed and Predicted Performance As noted in Section 4.4, the predicted FBS fatigue lives are:

nominal 150 mm thickness: 2.3 x 106 ESA at 50% design reliability

nominal 200 mm thickness: 3.5 x 106 ESA at 50% design reliability.

Therefore the interim design process predicts it would take approximately 18 months of cumulative traffic loading for the 150 mm thick FBS section to fatigue crack and about two years for the 200 mm thick FBS section. Hence the predicted fatigue life is reasonably consistent with the observed cracking of both sections after a traffic loading of 2.1 x 106 ESA.

However, given the high bitumen contents of field cores of the nominal 150 mm thick FBS section there is considerable doubt about the applicability of the findings to more commonly used binder contents. Moreover, for the nominal 200 mm thick FBS about half of the field cores had unexpectedly high measured bitumen contents, possibly due to the inclusion of old asphalt patches in the recycled pavement. Of most use to the project is the performance of pavement areas with more typical binder contents. Further pavement coring is required to clearly identify these areas.


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5 KEWDALE ROAD WELSHPOOL

5.1 Introduction In November 2011, the City of Canning, Western Australia constructed FBS pavement sections on Kewdale Road, Welshpool. Three pavement sections were constructed:

a main section (100 m long and 4 m wide) constructed with 320 mm FBS thickness

under-designed Section 1: 50 m length with 150 mm FBS thickness

under-designed Section 2: 50 m length with 100 mm FBS thickness.

Only the two under-designed sections were selected for performance review in this project as the 320 mm thick section is unlikely to be distressed during the project period.

Details of locality and job statistics (job size, FBS specification and construction method) for the Kewdale Road FBS pavement are given in Table 5.1.

Table 5.1: Description of Kewdale Road FBS pavement

Location Kewdale Road Welshpool, Western Australia (southbound close to Dowd Street intersection) Job size Length 2 sections, each 50 m in length

Number of lanes 1 (slow lane) Lane width 4 m Total area 400 m2

Stabilisation depth Section 1: nominal 150 mm FBS Section 2: nominal 100 mm FBS

Wearing course 30 mm dense graded asphalt Foamed stabilisation specification

Mix design Empirically-based method Host materials 30% recycled asphalt and 70% crushed granite base Supplementary binder 0.8% hydrated lime Bitumen 3.5% class 170 bitumen Foaming agent

Construction method

Work specifications and QA testing Under supervision of City of Canning Construction date 13 November 2011

Source: Personal communication Leek (2012).

Figure 5.1 shows Kewdale Road prior to stabilisation; Section 1 is located 50–100 m from the intersection with Dowd Street and Section 2 is located 0–50 m from the intersection. As such, both sections experience shear stresses due to braking and acceleration of heavy vehicles.


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Figure 5.1: Kewdale Road looking towards intersection with Dowd Street

5.2 Site Investigation Prior to Stabilisation Coring and sampling of the pavement materials was undertaken at eight locations and dynamic cone penetrometer (DCP) testing of the subgrade was also performed prior to stabilisation. The results (Table 5.2) indicated that the existing pavement structure prior to rehabilitation comprised:

45–60 mm dense graded asphalt

140–275 mm thickness of size 20 mm crushed granite base

120–230 mm thickness of size 40 mm gravel or crushed limestone subbase

subgrade sand with in situ CBRs in the range of 15–50%.

Table 5.2: Results of coring and DCP testing on Kewdale Road FBS pavement prior to stabilisation

Chainage (m) Section 1 Section 2 80 110 120 120 20 20 50 70

Offset (m) 2.0 1.0 1.5 2.0 1.5 2.0 1.5 1.5

Asphalt thickness (mm) 50 50 45 55 50 50 60 50 Crushed rock base thickness (mm) 150 140 185 175 220(1) 275(1) 260(1) 220(1) Crushed limestone/gravel subbase thickness (mm) 220 210 230 150 165 185 130 165 Total pavement depth (mm) 420 400 460 380 435 510 450 435 Subgrade CBR (%) NR(2) 35 15 25 30 30 50 15

1 Crushed rock base thickness after 50 mm granular resheet. 2 Not recorded. Source: Personal communication Leek (2012). There were also some areas of asphalt patching in both sections.


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Prior to stabilisation, a 45 mm granular resheet of size 20 mm crushed granite base was placed on Section 2 to raise its pavement profile (Figure 5.2). This allowed the construction of the 100 mm thick FBS layer by firstly stabilising the overlaid pavement to a depth of 150 mm, then trimming the surface by 45 mm to the height of the adjacent traffic lane.


Figure 5.2: Crushed granite base resheet of Section 2 before stabilisation

5.3 Mix Design Samples of materials in Section 1 and Section 2 were collected from the roadbed after pulverising the top 150 mm layer with the stabiliser (Leek 2012). Results of particle size distribution and plasticity index (PI) of these materials are summarised in Table 5.3 and Figure 5.3. The host material lacked fines (for grain size < 0.15 mm) as compared to the Zone A particle size distribution (Austroads 2006).

Table 5.3: Results of particle size distribution and PI for the untreated materials in Kewdale Road FBS pavement (prior to stabilisation)

Size (mm)

Percentage passing PI (%) 19 16 13.2 9.5 6.7 4.75 2.36 1.18 0.6 0.425 0.3 0.15 0.075

Section 1 100 99 97 90 80 71 56 41 28 21 15 7 3 8

Section 2 100 98 91 75 62 52 38 28 20 16 12 6 2 4

Austroads (2006) 73–100 44–75 29–55 23–45 18–38 14–31 10–27 8–24 5–20 Source: Personal communication Leek (2012).

A mix design was not undertaken prior to the works. Based on previous experience in the City of Canning, the host material was stabilised with a target 3.5% residual bitumen and 0.8% hydrated lime.

Laboratory testing to determine FBS design modulus is planned for 2013–14.


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Figure 5.3: Particle size distribution of untreated materials in Kewdale Road FBS pavement

5.4 Thickness Design The structural designs of the two under-designed test sections are shown in Figure 5.4.

The FBS thicknesses were selected as follows to increase the probability of observing fatigue cracking during the research project:

Section 1 has a nominal 150 mm thickness of FBS, which is the minimum allowable FBS thickness (150 mm) when using the normal construction method.

Section 2 has a nominal 100 mm thickness of FBS, which required a special construction method (Section 5.5). The 100 mm depth was achieved by firstly stabilising to a depth of 150 mm layer was then trimming back to the design 100 mm thickness before compaction.

Table 5.4 shows the pavement structures and the selected design moduli used in the Austroads interim FBS thickness design procedure to predict the FBS fatigue lives. Given that there was no laboratory data yet to determine the FBS design modulus, a typical FBS design modulus value of 2500 MPa was assumed.

The following FBS fatigue lives were predicted:

Section 1 (150 mm FBS base): 3.7 x 106 ESA (50% design reliability).


The high moduli of the underlying granular subbase and sand subgrades increase the predicted FBS fatigue lives on Kewdale Road.

0

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80

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100

0.01 0.1 1 10

Percentage passing

Sieve size (mm)

Section 1

Section 2

Lower limit Zone A Austroads 2006

Upper limit Zone A, Austroads 2006


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Section 1 Section 2

30 mm asphalt wearing course

150 mm FBS 100 mm FBS

200 mm crushed granite base

50 mm crushed granite base

200 mm crushed limestone/gravel subbase

150 mm crushed limestone/gravel subbase

Sand subgrade

Figure 5.4: Kewdale Road pavement structures

Table 5.4: Data used to predict FBS fatigue lives of Kewdale Road FBS trial pavements

Pavement component

Design parameter Section 1 Section 2 Technical basis for data selection

Subgrade Subgrade type CBR 12% CBR 12% Presumptive design value for subgrade sand in WA. Subgrade design

modulus 120 MPa 120 MPa

Subbase Subbase thickness 270 mm 370 mm Mixture of crushed granite base and gravel subbase. Design modulus of

subbase Table 6.4 of Austroads

(2012) Table 6.4 of Austroads

(2012) FBS base FBS thickness 130 mm 80 mm Design thickness of 150 mm (Section 1) and

100 mm (Section 2) less 20 mm construction tolerance.

FBS design modulus 2500 MPa 2500 MPa Assumed, will be determined later in the project from laboratory mix design testing.

Wearing course

Thickness 30 mm 30 mm For typical dense graded asphalt (size 10 mm, Class 320) assuming a design speed of 50 km/h and the Weighted Mean Annual Pavement Temperature (WMAPT) of 29 °C for an urban road in Perth.

Design modulus 2600 MPa 2600 MPa


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5.5 Pavement Construction The sections were stabilised on 13 November 2011 and opened to traffic the same day. The preliminary construction report (personal communication Leek 2012) indicated that:

A Wirtgen WR 2500 SK stabiliser was used and the construction tolerance for the application rate for the binder and supplementary binder was ±10% of the specified values. The minimum stabilisation depth of 150 mm was initially constructed for both Section 1 and Section 2. The 150 mm layer in Section 2 was then cut back to the design 100 mm thickness during the compaction and shaping operation.

Compaction equipment included (a) an 18 tonne vibrating padfoot roller (b) a 12 tonne vibrating smooth drum roller; and (c) a 20 tonne multi-tyre roller. The specified minimum field compaction was 98% Modified Maximum Dry Density.


Figure 5.5: Kewdale Road FBS site during stabilisation

The sections were opened to traffic prior to the placement of the 30 mm thick dense graded asphalt surfacing several days later. The unsealed foamed bitumen stabilised surface ravelled under initial trafficking (Figure 5.6) as observed during the Calder Freeway construction (Section 3.6.2).


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Figure 5.6: Ravelling of Section 1 due to trafficking before the asphalt surfacing was placed

5.6 Pavement Condition Monitoring Since construction in November 2011 Curtin University has monitored the pavement condition.

In February 2013, about 15 months after construction the test pavements were inspected and rutting was measured. Rut depths were measured on the 30 mm thick asphalt surfacing every 5 m along the two sections. There was minimal rutting with all measurements less than 3 mm depth.

There was also no cracking in either section and they were in sound condition.

Surface deflections were measured using a falling weight deflectometer (FWD) at the following times:

14 November 2011, the day after construction and prior to placement of the asphalt surfacing

5 January 2012, about seven weeks after stabilisation and after placement of the asphalt surfacing

6 December 2012, 13 months after stabilisation.

The deflection bowls were measured using a contact stress in the range 600–700 kPa then normalised to a 566 kPa. The surface temperatures during the FWD measurements were with 3 °C of the Weighted Mean Annual Pavement Temperature (WMAPT) of 29 °C. As the pavement temperature at mid-depth was not measured, the deflections cannot be reliably temperature corrected.

The maximum deflections (D0) and curvatures (D0–D200) normalised to a stress of 566 kPa are plotted in Figure 5.7. Note that the deflections measured on 14 November 2011 (the day after stabilisation) were measured without the 30 mm thick asphalt surfacing. Had the surfacing been in place it is estimated the maximum deflections would have been about 10% lower and the curvatures about 20% lower.


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Figure 5.7: Kewdale Road measured surface deflections

The results to date suggest that seven weeks after stabilisation the pavements had cured. There is no indication yet that the FBS material is deteriorating structurally in either section.

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Maximum deflection at 566 kPa

(mm)

Chainage

14-Nov-11, 1 day

5-Jan-12, 7 weeks

6-Dec-12, 13 months

Section 1150 mm

Section 2100 mm

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Curvaturesat 566 kPa

(mm)

Chainage

14-Nov-11, 1 day

5-Jan-12, 7 weeks

6-Dec-12, 13 months

Section 1150 mm

Section 2100 mm


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5.7 Traffic Monitoring Annual average daily traffic (AADT) and percentage heavy vehicles data as given in Table 5.5.

Table 5.5: Traffic data for Kewdale Road

Road name Lane Date AADT (slow lane)

Percentage heavy vehicles

(slow lane)

Annual daily heavy vehicles

Annual ESA

Kewdale Road, Welshpool

Southbound May 2010 6000 26 1590 8.7 x 105 July 2012 7300 28 2050 1.1 x 106


The MRWA Engineering Road Note 9 (MRWA 2013) provides a presumptive ESA per heavy vehicle value of 1.5. Using this value the annual ESA of loadings in Table 5.5 were estimated.

5.8 Comparison of Observed and Predicted Performance As discussed in Section 5.4, the predicted FBS fatigue lives are:

Section 1 (150 mm FBS base): 3.7 x 106 ESA (50% design reliability)


Based on the traffic data in Table 5.5, the estimated annual cumulative traffic loading would be about 106 ESA. Consequently:

Section 1 (150 mm FBS base): it would take approximately three years of cumulative traffic loading to reach the predicted fatigue life of 3.7 x 106 ESA (50% design reliability).

Section 2 (100 mm FBS base): it would take approximately one year of cumulative traffic loading to reach the predicted fatigue life of 1.1 x 106 ESA (50% design reliability).

As described in Section 5.6, there are no observable pavement defects after 16 months of cumulative traffic loading since construction in November 2011. In addition, there is no clear evidence at this stage that the foamed bitumen stabilised material is reducing in modulus due to traffic loading.

It is planned to monitor these two FBS pavement sections over the next two years to provide detailed data on pavement performance (surface defects, cracking, rutting, roughness, deflection) for the validation of the Austroads interim FBS thickness design procedure.


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6 KWINANA FREEWAY PERTH

6.1 Introduction In 2010, trial sections of FBS pavements were constructed for Main Roads Western Australia (MRWA) on the Kwinana Freeway Perth. Three pavement sections, each 100 m long and 3.8 m wide, were constructed with different FBS thicknesses (namely 150 mm, 240 mm and 290 mm) and resurfaced with 30 mm dense graded asphalt (DGA) and 30 mm open graded asphalt (OGA). Figure 6.1 shows a view of the test site during construction.

Only the under-designed pavement section with the minimum FBS thickness of 150 mm is considered suitable for inclusion in this project.

Source: Personal communication Kenworthy-Groen (2012).

Figure 6.1: Kwinana Freeway FBS site

Details of locality and job statistics (job size, FBS specification and construction method) for the Kwinana Freeway under-designed FBS pavement section are given in Table 6.1.

Detailed data on mix design, pavement design and construction for this pavement supplied by MRWA (personal communication Kenworthy-Groen 2012) is briefly described below.

Table 6.1: Description of Kwinana Freeway FBS pavement

Location Kwinana Freeway (north of the Mundijong Road between 37.72–37.82 SLK) northbound Job size Length 100 m

Number of lanes 1 (outer lane) Lane width 3.8 m Stabilisation depth 150 mm FBS base Wearing course 30 mm OGA+ geofabric + 30 mm DGA


Mix design by MRWA (empirically-based method) Host materials Mixture of HCTCRB (85%) and crushed limestone subbase (15%) Supplementary binder 0.8% lime Bitumen 3.5% class 170 bitumen Foaming agent

Construction method

Work specifications and QA testing MRWA 2010 Construction Specification Foamed Bitumen Stabilisation Pavement Construction date February 2010



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6.2 Site Investigation Prior to Stabilisation Site investigation prior to stabilisation showed that the existing pavement had the following composition:

30 mm open graded asphalt

30 mm dense graded asphalt

10 mm sprayed seal

125 mm hydrated cement treated crushed rock base (HCTCRB)

225 mm crushed limestone subbase

sand subgrade.

HCTCRB is crushed rock base that has been mixed with water and 2% of cement and then allowed to hydrate in stockpile for extended period of time before wet mixing again, placing and compacting in the road-bed.

Rutting, loss of texture in wheel-tracks and minor shape problems were observed. Subsequently, it was decided to trial the use of FBS as a rehabilitation treatment.

6.3 Mix Design A large bulk sample of each pavement layer was excavated using a 1 m wide profiler from the pavement at the south end of the pavement section at SLK 38.015 prior to stabilisation. The OGA and DGA asphalt layers were removed by the profiler. Laboratory particle size distribution test results for these materials are summarised in Table 6.2.

Table 6.2 also includes the particle size distribution of a sample collected behind the stabiliser after pulverising and mixing. As explained in Section 6.5, as the pavement was initially stabilised to a nominal depth of 210 mm, the host material comprised:

30 mm open graded asphalt

30 mm dense graded asphalt

125 mm HCTCRB

25 mm crushed limestone subbase.

For this under-designed pavement section, MRWA specified a 3.5% residual bitumen and 0.8% hydrated lime in the FBS process. The binder contents were empirically based rather than established through a mix design process.

It is proposed that a mix design be undertaken as part of this research project, provided sufficient amounts of materials recovered from the roadbed are still available.


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Table 6.2: Particle size distribution of the host material Kwinana Freeway FBS pavement

Sieve size (mm)

Percentage passing

75 100 26.5 99 19 99

13.2 94 9.5 85 4.75 62 2.36 44 1.18 34 0.600 26 0.425 21 0.300 17 0.150 11 0.075 7


6.4 Thickness Design The 150 mm FBS thickness was selected to increase the likelihood of observing FBS fatigue in accordance with the project objective.

Table 6.3 shows the final pavement structure and the selected design modulus values used in the Austroads interim FBS thickness design procedure to calculate the allowable traffic loading of the under-designed pavement. Given that laboratory measured moduli are currently not available to determine FBS design modulus, a typical FBS design modulus value of 2500 MPa was assumed.

Based on this data set, the predicted FBS fatigue life is 1.7 x 107 ESA at 50% design reliability.

Table 6.3: Data used to predict FBS life of the under-designed Kwinana Freeway pavement

Pavement component

Design parameter Available data Technical basis for data selection

Subgrade Subgrade type CBR 12% Presumptive design value for subgrade sand in WA Subgrade design modulus 120 MPa

Subbase Subbase thickness 200 mm Normal crushed rock base/subbase as per original design Design modulus of subbase Table 6.4 of Austroads (2012)

FBS base FBS thickness 135 mm Mean thickness of 160 mm and construction tolerance of 20 mm

FBS design modulus 2500 MPa For typical dense FBS base (assuming a design speed of 80 km/h and the WMAPT of 29 °C for a freeway in Perth)

Wearing course

Thickness 70 mm 30 mm OGA + geofabric + 30 mm DGA Design modulus 3600 MPa


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6.5 Pavement Construction The pavement was constructed in February 2010 in accordance with the MRWA Construction Specification Foamed Bitumen Stabilised Trial Kwinana Freeway (MRWA 2010).

In planning Kwinana Freeway trial sections it was proposed to open the unsealed FBS base to traffic to observe the early-life ravelling and rutting prior to reshaping and placement of the asphalt surfacing. Consequently, the initial plan was to prepare the unsealed FBS to the level of the adjacent traffic lane, open it to traffic and several days later to mill the top 60 mm of the FBS to provide for the 60 mm asphalt surfacing. Although this early-life performance evaluation was not implemented, the sequence of the works program aligned with the initial plan:

The 30 mm thick open graded asphalt, 30 mm dense graded asphalt, 125 mm HCTCRB and 25 mm was pulverised, mixed and compacted to provide 210 mm thickness of FBS base. Note that due to concerns about the breakdown of the crushed limestone subbase due to the stabiliser, the lime and bitumen were incorporated into the pavement in the first pass of the stabiliser to minimise the number of mixing passes. Nevertheless a second mixing pass was required due to inadequate depth of mixing in the first pass.

Several days later the top 60 mm of FBS base layer was removed by milling and brooming.

The asphalt surfacing was placed consisting of 30 mm thick open graded asphalt on 30 mm dense graded asphalt.

Detailed specifications of stabiliser and compaction equipment and construction tolerances are given below.

A Wirtgen WR 2000 stabiliser was used and the construction tolerance for the application rate for the binder and supplementary binder was ±10% of the specified values.

Compaction equipment used comprised (a) a vibrating padfoot roller of a minimum mass of 18 t; (b) a vibrating smooth drum roller with a minimum mass of 12 t; and (c) a multi-tyre roller with a minimum mass of 15 t. The stabilised pavement layers were compacted uniformly to the full depth and over the full width and compacted to a characteristic dry density ratio (Rc) of 98% or greater.

QA testing for layer thickness and density was carried out at three locations (chainages 225 m, 250 m, 275 m) and the results of layer thickness and density are given in Table 6.4. The results confirmed that the minimum compaction standard was achieved.

Table 6.4: QA testing for pavement thickness and density after construction

Test location SLK (km)

Thickness (mm) Nuclear density meter testing on the FBS base Wearing course and

FBS base Limestone subbase Dry density ratios

(%)(1) Moisture ratio (%)(1)

37.750 210 210 105.7 55 37.775 240 170 103.3 53 38.000 220 220 105.3 51

Average 223 200 104.8 53

1 Based on Modified MDD = 2.081 t/m3 and Modified OMC = 8.2%.

6.6 Condition Monitoring Since construction, MRWA has regularly inspected the pavement and has reported no surface defects to date.


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MRWA also conducted four FWD surveys about four months, 14 months, 26 months, 33 months and 39 months after construction). The FWD testing results (as shown in Figure 6.2) indicated that pavement deflections significantly reduced in the first 12 months and have become more stable since.

To date there is no evidence that the FBS is deteriorating structurally under traffic loading.

Figure 6.2: FWD testing results for Kwinana Freeway FBS site

0.00

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0.45

0.50

37.725 37.735 37.745 37.755 37.765 37.775 37.785 37.795 37.805 37.815

Normalised maximumdeflection

(mm)

Kwinana Freeway northbound outer lane SLK

Deflection Jun 2010

Deflection April 2011

Deflection April 2012

Deflection Nov 2012

Deflection May 2013

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37.725 37.735 37.745 37.755 37.765 37.775 37.785 37.795 37.805 37.815

Normalised curvature

(mm)

Kwinana Freeway northbound outer lane SLK

Curvature Jun 2010Curvature April 2011Curvature April 2012Curvature Nov 2012Curvature May 2013


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6.7 Traffic Monitoring Weekly traffic data for Kwinana Freeway provided traffic classification counts on the northbound lane of Kwinana Freeway just south of the Mundijong Rd Bridge for the period 2006–11 as given in Table 6.5.

Table 6.5: Kwinana Freeway northbound carriageway daily heavy vehicle volumes

Survey date Austroads vehicle classification 3 4 5 6 7 8 9 10 11 12

07 July–13 July 2006 414 113 59 25 183 40 200 27 38 20

23 June 2010–2 July 2010 1105 142 27 37 58 52 356 94 140 2

10 August 2011–17 August 2011 1541 182 27 82 84 152 259 88 143 5 Source: Personal communication Kenworthy-Groen (2012).

Table 12 of Main Roads Engineering Road Note 9 (MRWA 2013) provides the average ESA of pavement loading for each Austroads vehicle class. Table 6.6 lists the values recommended for use for this project.

Table 6.6: Kwinana Freeway average ESA per heavy vehicle type

Austroads vehicle classification

3 4 5 6 7 8 9 10 11 12

0.49 2.63 2.8 0.68 1.49 3.73 4.69 6.79 8.88 11.54 Source: MRWA (2013), Table 12 Kwinana Freeway (H015) SLK56.84, Mandurah. The annual ESA of loading were calculated based on:

annual heavy vehicle volumes in the slow lane calculated from the average daily values (Table 6.5) and assumed 70% of heavy vehicles travel in the slow lane

the ESA of damage per heavy vehicle type (Table 6.6).

The calculated annual ESA of loading for 2006, 2010 and 2011 were 7.1 x 105 ESA, 1.2 x 106 ESA and 1.3 x 106 ESA.

Based on this data, Figure 6.3 shows the predicted cumulative traffic loading over the 10 year period from pavement construction in 2010 assuming an annual ESA of loading increase of 1.2 x 106 ESA.


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Figure 6.3: Predicted cumulative traffic loading

6.8 Performance Review Based on the traffic data in Section 6.7 it would take about 10 years of cumulative traffic loading to reach the predicted fatigue life of 1.7 x 107 ESA (50% design reliability).

Currently, there is no pavement distress after 3.3 years of cumulative traffic loading. It is planned to monitor the pavement over the next three years to provide detailed data on pavement performance (surface defects, cracking, rutting, roughness, deflection) for the validation of the Austroads interim FBS thickness design procedure.

As it is unlikely that cracking will be observed by the completion of the project (June 2015), reliance will be placed on the change in measured surfaced deflections as an indicator of structural deterioration.

1.0E+06

3.0E+06

5.0E+06

7.0E+06

9.0E+06

1.1E+07

1.3E+07

1.5E+07

1.7E+07

1.9E+07

2010 2011 2012 2013 2014 2015 2016 2017 2018 2019

Cumulative traffic

loading (ESA)

Year


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7 NEW ENGLAND HIGHWAY QUEENSLAND

7.1 Brief Description In March to May 1999, two separate sections (with a total 16.74 km road length) on New England Highway (between Toowoomba Road-Warwick Road) in Queensland were rehabilitated using FBS to correct shape loss and improve strength. The first section was between 34.45–48.25 km (between Toowoomba-Warwick Road) and the second section between 52.75–55.69 km (north of Warwick).

Details of locality and job statistics (job size, FBS specification and construction method) for the New England Highway FBS pavement are given in Table 7.1.

Table 7.1: Job description of New England Highway FBS pavement

Location New England Highway (22B) (Toowoomba–Warwick Road) between 34.45–48.25 km and 52.75–55.69 km Job size Length 16.74 km

Number of lanes 2 Lane width 4 m FBS thickness 200 mm (IWP) and 250 mm (OWP)


Mix design Empirically-based method and new TMR FBS mix design Host material Existing granular base materials (20 mm well graded clayey gravel complied with

MRS11.05 ‘C grading’) Quicklime 2 % hydrated lime Foamed bitumen 3.5% Class 170 bitumen Foaming agent 0.5%

Construction method

Work specifications and QA testing TMR construction specifications MRS 11.07 Construction date 23 March–28 May 1999

Figure 7.1 shows a view of the pavement.

Figure 7.1: New England Highway FBS pavement, near Nobby Connection Road intersection (34.5 km)

The pavements were designed and constructed to TMR standards (Kendall et al. 2001, Ramanujam & Jones 2000, Ramanujam et al. 2009).


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Data on site investigation, mix design, pavement design, construction, maintenance and traffic and field performance for this road gathered from various TMR reports is briefly described below.

7.2 Site Investigation Prior to Stabilisation Prior to stabilisation the pavement was a sprayed seal unbound granular pavement. By 1999 the pavement had a significant amount of rutting of the well graded clayey gravel base over the low strength black soil subgrade. There were also a number of sections of the pavement which had been rehabilitated by cement stabilisation. Consequently TMR decided to rehabilitate the pavement using FBS to correct shape loss and improve strength.

Prior to construction, dynamic cone penetration testing was conducted. This testing confirmed that the subgrade was of CBR 5% or greater (Ramanujam et al. 2009).

7.3 Mix Design The bitumen and lime contents for the works were selected based on TMR experience obtained from previous FBS trials in Queensland and the FBS mix design method under development by TMR at that time (Ramanujam & Jones 2000, Kendall et al. 2001).

For the mix design, samples from the original well graded clayey gravel base were collected in accordance with TMR standard materials sampling procedures. Preliminary assessment testing of the base material was conducted to confirm that the materials met the TMR specifications for stabilisation (in terms of particle size distribution, Atterberg limits and moisture density relationship). It was reported to comply with the MRS11.05 ‘C particle size distribution’ envelopes and had a fines content between 5% and 15% passing the 0.075 mm sieve. The measured Atterberg limits were not reported.

TMR performed a number of laboratory tests to optimise the binder contents and foamed water content. Class 170 bitumen was preferred for foamed bitumen stabilisation. Tests indicated the desirable foaming properties were usually achieved with a water content of 2.5%. A foaming agent (0.5% by mass of the bitumen) was also added to the bitumen to enhance the bitumen foaming properties.

The optimum bitumen content of the FBS mix was also selected on the basis of laboratory modulus and rut resistance. Based on the results of cured wet indirect tensile test (IDT) resilient moduli of mixes with bitumen contents in the range of 2–4% and 1.5% quicklime (Figure 7.2), a mix with 3.5% bitumen and 1.5 % quicklime was selected: this mix had the highest indirect tensile modulus of about 2100 MPa. This mix also met the TMR minimum guidelines for IDT modulus.

Test slabs of the selected mix design were prepared in the laboratory and tested using the wheel-tracker test for rut resistance. It was reported that the rut resistance also met the TMR minimum guidelines for rut resistance.


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Source: Kendall et al. (2001).

Figure 7.2: Results of cured wet modulus for various FBS mixes for New England Highway FBS pavement

7.4 Thickness Design Kendall et al. (2001) reported that the FBS pavement was designed and constructed to have a design life of 20 years. Although there were large variations in pavement thicknesses and subgrade support along the 17 km pavement length of this road section, the selected treatment was as follows:

FBS was carried out to a width of 8 m (i.e. traffic lanes plus 0.5 metre of each shoulder) rather than full width

the FBS depth was 200 mm for the inner wheelpath (IWP) and 250 mm for the outer wheelpath (OWP)

a primer seal was initially applied on the FBS base.

Note that Kendall et al. (2001) advised that the thickness design anticipated that a 75 mm thick asphalt overlay would be required on most sections to achieve the 20 year life. Based on deflection testing after construction it was concluded that this structural overlay was not required.

As discussed in Section 7.10, the Austroads interim thickness design method predicts a fatigue life significantly less than 20 years.

7.5 Pavement Construction The pavement was constructed between March and May 1999 using a new specification developed for the project. This project specification was later modified to produce the Main Roads Standard Specifications MRS 11.07 Specification for In situ Stabilisation. The project specification provided detailed specifications of stabiliser and compaction equipment and construction tolerances as given below:

A 30 t Wirtgen WR 2500 stabiliser was used and the construction tolerance for the application rate for the binder and supplementary binder was ±10% of the specified values. The depths of stabilisation had a construction tolerance of ±15 mm.

1200

1400

1600

1800

2000

2200

2 2.5 3 3.5 4

Bitumen Content (%)

Mod

ulus

(MPa

)


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Compaction equipment included (a) an 18 t vibrating padfoot roller; (b) a 12 t vibrating smooth drum roller; and (c) a 15 t multi-tyre roller. The stabilised pavement layers were required to be compacted to a dry density ratio of not less than 100% Standard Maximum Dry Density.

It was reported (Kendall et al. 2001) that:

most of the recorded lime spread rates and bitumen pumping speeds were within the tolerance of ±5% of the specified lime-spread rate and bitumen-pumping speed

the design FBS depth (200 mm at IWP and 250 mm at OWP) were achieved with a tolerance of ±15 mm

most of the recorded field density results were in the range of 100–110% Standard Maximum Dry Density

compaction moistures of the FBS layers varied over the large range (4–8%) due to different initial in situ moisture contents at different locations.

In a number of locations the granular pavement had been previously rehabilitated using cement stabilisation. These cement stabilised materials were not removed but incorporated in the FBS pavement (Kendall et al. 2001).

7.6 Pavement Coring In April 2000 prior to the application of the final seal, four FBS cores were extracted from the pavement to compare in situ properties with design values (Ramanujam & Jones 2007). They were cored in a staggered pattern 250 m apart (chainages have not been reported).

The results are given in Table 7.2. Although the cured wet moduli were clearly high, the measured bitumen contents of three of the four cores were well below the design values of 3.5%.

Table 7.2: Results of New England Highway cores extracted April 2000

Core Sample Cured dry modulus

(MPa)

Cured wet modulus

(MPa)

Bitumen content (%)

Compacted density (t/m3)

Air voids (%)

Outer wheelpath

Top 6 725 4 139 2.05 2.265 14.0

Middle 1 5 761 3 749 2.10 2.234 15.2

Middle 2 3 180 3 406 2.10 2.137 19.9

Bottom 2 533 1 290 2.40 2.076 21.5

Inner wheelpath

Top 10 907 9 329 2.55 2.326 6.8

Middle 8 468 11 270 2.50 2.303 7.1

Bottom 7 330 5 852 2.85 2.225 11.1

Outer wheelpath

Top 7 200 6 275 3.20 2.173 7.2

Middle 5 743 5 220 2.55 2.174 9.2

Bottom 2 428 2 072 3.20 2.107 13.4

Inner wheelpath

Top 6 000 5 308 4.10 2.232 8.5

Middle 7 831 5 911 3.40 2.295 5.8

Bottom 2 744 1 842 3.75 2.213 10.8


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7.7 Pavement Maintenance The TMR network survey provides maintenance history recorded over the full length of the project since construction in 1999, as summarised in Table 7.3.

Table 7.3: New England Highway maintenance

Section Date Chainage (km)

Length (km)

Treatment

1 April 2000 34.45–48.25 13.8 (full length)

Final seal over the primerseal placed at construction a year after FBS construction

June 2000 47.28–47.68 0.40 80 mm asphalt overlay

November 2002 36.81–43.61 6.80 Geotextile reinforced seal

November 2010 37.60–38.80 1.20 30 mm dense graded asphalt overlay

November 2010 46.87–47.28 0.41 30 mm dense graded asphalt overlay

November 2011 34.45–36.43 1.98 Double application PMB seal


November 2011 38.8–46.89 8.09 Single application PMB seal


2 April 2000 52.75–55.69 2.94 (full length)

Final seal over the primerseal placed at construction

November 2011 52.75–55.69 2.94 (full length)

Single PMB seal

Of particular note was the geotextile reinforced seal placed over about a third of the project length in November 2002 – after about three years trafficking. A section of this (36.43–38.8 km) needed to be re-treated with a geotextile seal in November 2011. By November 2011 about half (8.19 km) of the project length had received a geotextile reinforced seal. Note that 12 months before the geotextile seal was placed, a 30 mm corrector course of asphalt was required at some locations due to the loss of shape after cracking.

Advice from TMR regional staff is that geotextile seals were required because of extensive cracking in the wheelpaths. The cracking was generally longitudinal in the wheelpaths as shown in Figure 7.3. However between chainages 36.43 to 38.8 km in addition to the longitudinal cracking there are some limited areas of severe crocodile fatigue cracking (Figure 7.4).


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Source: Google maps (2013).

Figure 7.3: Cracking at chainage 47.5 km in November 2009, 12 months before geotextile seal was placed

Source: Google maps (2013).

Figure 7.4: Cracking at chainage 37.8 km in November 2009, 12 months before geotextile seal was placed


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7.8 Performance Monitoring 7.8.1 Visual Inspections In May 2013 the pavement was visually inspected. Generally, the southbound lane was in worse condition than the northbound, perhaps due to the southbound vehicles heading from Toowoomba being more heavily laden.

As described in Section 7.7, geotextile seals have been placed over a substantial portion of Section 1 (34.45–48.25 km) which presumably hides much of the cracking. The cracking in these areas is longitudinal cracking both in the loaded areas of the pavements (wheelpaths) and unloaded areas. As such, the longitudinal cracking is unlikely to be related to the fatigue of the FBS base. The most likely source of the longitudinal cracking is changes in moisture content of highly plastic black soil subgrade. Clearly, such cracking has a major influence on the fatigue performance of the FBS material. In addition, TMR advice is the re-stabilisation of previously cement stabilised patches may have contributed to the cracking. TMR advise that re-stabilisation is now not encouraged and replacement of the patch with granular material prior to stabilisation is recommended. These factors limit the usefulness of the site for the Austroads project.

Figure 7.5 shows the pavement condition in the north of the Spring Creek Road intersection, an area that has not been treated with a geotextile seal. Like a number of other areas along the project, the surface condition suggests transverse cracking in the wheelpaths indicative of fatigue cracking.

For the New England Highway performance data to be of use in evaluating the structural design method, pavement sections without longitudinal cracking will need to be identified.

Figure 7.5: Flushed binder on the surface suggests transverse cracking under the PMB seal, chainage 46.7 km

At the time of inspection geotextile seals had not been placed in Section 2 (52.75–55.69 km) and this allowed a better appreciation of the extent of fatigue cracking. Figure 7.6 illustrates the development of transverse fatigue cracking along the inner wheelpath.


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Figure 7.6: Transverse fatigue cracking in New England Highway FBS pavement, chainage 53.6 km

In the vicinity of chainage 54.8 km, there is currently extensive block cracking and rutting as shown in Figure 7.7.

Figure 7.7: Severe cracking in southbound lane near chainage 54.8 km

In 2013–14, pavement investigations will be undertaken at various locations in Section 2 (52.75–55.69 km) to measure pavement deflections, layer thickness and in situ subgrade CBR in areas that have fatigue cracked but do not exhibit longitudinal cracking. A thermal imaging camera may be useful to identify cracks below the geotextile seals.

7.8.2 2012 Roughness and Rutting Data Figure 7.8 shows the data on rutting and roughness for the full length of the New England Highway (22B) as of February 2012.


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It is apparent that despite the fatigue cracking that has occurred, the maintenance treatments (Section 7.7) have resulted in rut depths generally not exceeding 10 mm and the roughness below the level where intervention may be required (IRI = 3.5 m/km). There are however some shorter sections (e.g. 54.65–54.85 km) that require treatment due to extensive cracking and associated rutting.

Figure 7.8: 2012 rutting and roughness for New England Highway FBS pavement

0

2

4

6

8

10

12

14

16

18

20

34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56

Rut depth(mm)

Chainage (km)

OWP

IWP

1

1.5

2

2.5

3

3.5

4

34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56

RoughnessIRI

(m/km)

Chainage (km)


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7.9 Traffic Monitoring Table 7.4 shows the measured truck traffic counts in 2012 provided by TMR from which the 2012 ESA of loading were calculated, based on an assumed average 3 ESA of damage per heavy vehicle from weigh-in-motion data on Gore Highway and Warrego Highway near Toowoomba (Austroads 2012).

Assuming a 4% traffic growth rate, the cumulative traffic loadings after 14 years of trafficking (May 2013) were estimated as shown in Table 7.4.

Table 7.4: Estimated 2012 traffic loading

Chainage (km)

2012 daily heavy vehicles (one-way)

2012 annual heavy vehicles (one-way)

2012 annual ESA

Cumulative ESA at May 2013

34.45–43.73 226 8.2 x 104 3.3 x 105 2.6 x 106 43.73–56.91 269 9.8 x 104 3.9 x 105 3.1 x 106

7.10 Performance Prediction A key objective of the project is to improve the Austroads interim thickness design procedure. It is apparent from the above that the New England Highway will provide valuable information in this regard, provided areas can be identified where FBS fatigue cracking is not affected by the longitudinal cracking of the black soil subgrade.

In the interim method, the FBS design modulus is determined from indirect tensile moduli measured on laboratory-manufactured specimens cured for three days at 40 °C and then soaked in water under vacuum of 95 kPa for 10 minutes. These cured wet moduli are overly conservative moduli compared to the field cores as illustrated from the Calder Freeway trial data (Section 3.8.2). Consequently, at this stage in the project, it is suggested the FBS design moduli be determined from the cured dry moduli of laboratory-manufactured specimens.

In the New England Highway mix design, a soaked indirect tensile modulus of 2100 MPa was reported (Figure 7.2) for a 3.5% bitumen content. However, limited core data (Table 7.2) suggests the mean bitumen content in situ is about 3%. The soaked modulus at this bitumen content is about 1900 MPa.

Cured dry moduli of laboratory-manufactured specimens have not been reported. It is noted the dry moduli of the field cores were about 20% higher than the cured wet moduli (Table 7.2). Using this factor, the dry modulus of laboratory-manufactured specimens at 3% bitumen is estimated to be 2300 MPa at a temperature of 25 °C. Adjusting this dry cured modulus to a WMAPT of 27 °C (Toowoomba) and for a design traffic speed of 80 km/h, a FBS design modulus of 2000 MPa was calculated.

Table 7.5 provides a summary of the currently available data to predict the FBS fatigue life. Referring to Table 7.5:

A subgrade design CBR of 4% was adopted consistent with Ramanujam et al. (2009). Note that most of the pavement lies on the highly plastic black soils of Darling Downs.

The thickness of granular subbase after stabilisation in the 2011 TMR Network Survey is uncertain. However, for pavement with this traffic loading and subgrade design CBR it is considered that the total granular thickness would have been at least 400 mm prior to stabilisation. The remaining granular subbase thicknesses used in the calculation were based on an assumed 400 mm total thickness.


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An analysis was undertaken using the data set as given in Table 7.5. This analysis produced a predicted allowable loading to fatigue of 6.2 x 105 ESA (for the IWP) to 2.4 x 106 ESA (for the OWP) at 50 % design reliability.

Table 7.5: Data for predicting allowable traffic loading of New England Highway FBS pavement

Pavement component

Design parameter Selected data Technical basis for data selection

Subgrade Subgrade support CBR 4% Ramanujam et al. (2009) reported a minimum subgrade support of 4% in fatigued areas.

Subgrade design modulus 40 MPa Based on the relationship of subgrade modulus = 10 CBR (Austroads 2012). Granular subbase

Thickness 225 mm IWP 175 mm OWP

Assumed 400 mm thick granular pavement prior to stabilisation.

Design modulus 5 sub-layers Based on Table 6.4 of Austroads (2012). FBS base Thickness 175 mm (IWP)

225 mm (OWP) Mean thickness of 250 mm (OWP) and 200 mm (IWP) and construction tolerance of ±15 mm as per TMR construction specifications.

Design modulus 2000 MPa Laboratory dry modulus was taken as half the modulus of field cores based on Calder Freeway results. Dry modulus was then adjusted for temperature and loading rate using a Weighted Mean Annual Pavement Temperature = 27 °C and a heavy vehicle design speed = 80 km/h.

Volume of binder 7% Assumed based on bitumen content 3%. Surfacing Thickness n.a. Double spray seal is not considered as a structural component

(Austroads 2012). Design modulus n.a.

7.11 Comparison of Observed and Predicted Performance As the cumulative traffic loading to date exceeds these predicted lives, the Austroads interim design method predicts there is a 50% probability of observing fatigue cracking. As discussed in Section 7.8.1, there has been widespread longitudinal cracking along New England Highway for a number of years. Although the longitudinal cracking is commonly in the wheelpaths there is some doubt about the cause of this cracking. It may relate to the use of different stabilisation depths in the outer and inner wheelpaths or to reactive subgrade soils.

In addition crocodile fatigue cracking has occurred in some areas and these areas are considered as more reliable sources of data to calibrate the design model. Of particular interest is the performance of Section 2 (52.75–55.69 km).

To enable more accurate prediction of allowable loading, it is proposed to obtain the following data by coring/trenching at several sites along the project (subject to TMR approval):

thicknesses of FBS base and underlying granular subbase

in situ subgrade CBR as estimated from dynamic cone penetrometer measurements

binder content of the FBS material.

Nevertheless, the accuracy of the performance prediction will be limited due to the absence of measured cured dry modulus of laboratory-manufactured specimens.

The other complication in utilising the performance data from this site is the unusual pavement design in which the FBS thickness in the outer wheelpath was 50 mm greater than the inner wheelpath. It is not known whether this discontinuity has influenced the FBS fatigue characteristics. In addition, there is a need to discount the influence of longitudinal cracking due to moisture changes in the highly plastic black soil subgrade as mentioned above.


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8 PROPOSED 2013–14 RESEARCH

8.1 Introduction This section describes the proposed scope of research to be undertaken in 2013–14 in consultation with the project Working Group.

8.2 Mix Design Section 2 describes progress in developing the test methods for use in the Austroads mix design procedure.

8.2.1 Test Methods Table 8.1 lists the test methods that have been identified for drafting. The initial drafts of test methods T301, T305, T310 and T311 have been revised in light of the Working Group comments. It is anticipated these methods may need to be revised in 2013–14 following trial use and feedback from users. In addition, the remaining test methods will be drafted.

Table 8.1: Test methods under development

Number Title Status

T301 Determination of Foaming Properties of Bitumen Drafted

T305 Mixing of Foamed Bitumen Stabilised Materials (includes method of establishing mixing moisture content) Drafted

T310 Compaction of Test Cylinders of Foamed Bitumen Stabilised Mixtures: Part 1 Dynamic Compaction Using Marshall Drop Hammer

Drafted

T311 Compaction of Test Cylinders of Foamed Bitumen Stabilised Mixtures: Part 2 Gyratory Compaction Drafted

T313 Compaction of Test Slabs of Foamed Bitumen Stabilised Mixtures To be drafted in 2013–14

T320 Curing of Test Cylinders of Foamed Bitumen Stabilised Mixtures To be drafted in 2013–14

T321 Curing of Test Slabs of Foamed Bitumen Stabilised Mixtures To be drafted in 2013–14

T330 Resilient Modulus of Foamed Bitumen Stabilised Mixtures To be drafted in 2013–14

T340 Deformation Resistance of Foamed Bitumen Stabilised Mixtures by the Wheel-tracking Test To be drafted in 2013–14

8.2.2 Laboratory Testing It is proposed to undertake laboratory testing with the objectives of:

providing improved guidance on how to select the mixing moisture content for preparation of test specimens for modulus testing

quantifying the influence of the laboratory compaction method (100 mm mould Marshall, 150 mm mould Marshall, gyratory and Modified/Standard hammer) on indirect tensile modulus.


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8.3 Structural Design 8.3.1 Calder Freeway Woodend In 2013–14 the following testing is proposed in March 2014, 12 months after construction:

visual inspection

FWD deflection testing to assess whether the FBS modulus has increased or decreased in trafficked and untrafficked areas

coring of the FBS layer between wheelpaths to determine stabilisation depth and laboratory-measured indirect tensile modulus.

In situ layer moduli will be back-calculated from the FWD deflections and layer thicknesses.

Appendix A lists the pavement inspection and testing procedures.

8.3.2 Port Wakefield Road Virginia The pavement is currently distressed and may be resurfaced during 2013–14. This may impact on the proposed testing and monitoring.

The testing to date indicates most of the pavement has very high bitumen contents. A critical issue is to obtain more bitumen content data to possibly identify a section with a more commonly used bitumen content (< 4%).

At this stage it is proposed to visually inspect the pavement and undertake additional coring of the FBS layer to determine thickness, moduli, particle size distributions and bitumen contents.

If a section with more commonly used bitumen content (< 4%) is identified, FWD deflections in and between wheelpaths together with measurements of pavement temperature will be also taken.

8.3.3 Kewdale Road Welshpool To refine the pavement performance predictions, the indirect tensile modulus of laboratory manufactured specimens will be undertaken. In addition the following will be undertaken:

visual inspection

FWD deflection testing to assess whether the FBS modulus has increased or decreased in trafficked and untrafficked areas

coring of the FBS layer in the outer wheelpath and between wheelpaths to determine stabilisation depth and in situ moduli.

8.3.4 Kwinana Freeway Perth The testing will be limited to:

visual inspection

FWD deflection testing to assess whether the FBS modulus has increased or decreased in trafficked and untrafficked areas.

8.3.5 New England Highway Queensland As reported in Section 7, over half of this 17 km long project has now been treated with a geotextile seal, principally to address longitudinal cracking likely to be due to moisture changes in the highly plastic black soil subgrade.


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A detailed investigation of New England Highway is proposed to identify areas that have fatigue cracked without being influenced by this longitudinal cracking.

Another complication in using the data from this site is the variation in FBS thickness occurring across the pavement.

8.3.6 Review Other Monitoring Sites In addition to the monitoring data for five sites reported in Section 3 to Section 7, Austroads project TT1663 (Vuong 2012) recommended some limited monitoring of the following four sites:

Somerton Road, Campbellfield, Victoria

State Highway 26, Kurere Stream, New Zealand

State Highway 1, Cherry Lane, New Zealand

State Highway 3, Te Kuiti, Waikato, New Zealand.

In this progress report it is suggested that these four sites be no longer monitored in the project as the data will not assist in refining the interim thickness design method.

Somerton Road was constructed in 1993 about 20 years ago. As reported by Vuong a substantial length of the project has since been rehabilitated and he concluded:

Only the pavement section on the westbound left lane between chainages 320-1420 m, which had a reseal (with 10 mm spray seal) in 1995 and appeared to show fatigue cracking in 2006, is suitable for the performance review.

A 50 mm asphalt overlay has been applied to this area since 2006, which makes it difficult to assess the extent and timing of the FBS cracking. In addition and most importantly, the pavement was stabilised with 3% cement works flue dust and 3% bitumen. The use of 3% cement works flue dust is likely to have resulted in a more fatigue-susceptible material than is current stabilisation practice. In addition, it will be difficult to estimate the design modulus of the material – a critical parameter in the thickness design method. Given the above, it is considered no further evaluation of Somerton Road pavement is warranted in this project.

At the outset of the Austroads research of foamed bitumen stabilisation commencing with Austroads project TT1663, it was considered desirable to include performance monitoring of New Zealand pavements given the different mix types and FBS thickness used. The above three New Zealand pavements were suggested for inclusion in the Austroads research.

As reported by Vuong (2012) two (Cherry Lane and Te Kuiti) of the three pavements had at least 100 mm granular resheet of size 65 mm granular base (GAP 65 grading) to correct shape. Given the FBS thickness is 175 mm to 200 mm, about half of the host material is size 65 mm granular base. The modulus of FBS materials is a critical input in the Austroads interim thickness design method. In the interim method the design modulus is estimated from the laboratory indirect tensile modulus testing of laboratory manufactured mixes. This characterisation method is applicable to materials with a maximum size of 40 mm. As such, the design modulus of the Cherry Lane and Te Kuiti materials will not be able to be measured. As this significantly impacts on the ability to design the pavements with the Austroads interim method, it is considered no further evaluation of these two pavements is warranted in this project.

It is proposed that State Highway 26 Kurere Stream be retained for evaluation but due to its variable composition including sections with very high contents of recycled asphalt, the evaluation in 2013–14 be limited to a visual condition survey.


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8.3.7 Additional Sites Preliminary discussions have been held with Roads and Maritime Services New South Wales in relation to construction of an under-designed FBS pavement as part of rehabilitation works being undertaken on the heavily trafficked Newell Highway. The above-mentioned 2013–14 project tasks may need to be adjusted if this valuable additional site can be included in the project.


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9 SUMMARY Improvements are required to the current Austroads interim mix design and structural design methods for foamed bitumen stabilised pavements. This report details progress to address this need under Austroads project TT1825 Mix design and field evaluation of foamed bitumen stabilised pavements.

9.1 Mix Design Under the guidance of a project Working Group the mix design framework has been agreed. It has been decided to build on the experience of Department of Transport and Main Roads Queensland and use the indirect tensile modulus as the principal pavement performance measure in the mix design process. To date the following draft test methods have been developed:

T301 Determination of foaming properties of bitumen

T305 Mixing of foamed bitumen stabilised materials

T310 Compaction of test cylinders of foamed bitumen stabilised mixtures: Part 1 Dynamic compaction using Marshall drop hammer

T311 Compaction of test cylinders of foamed bitumen stabilised mixtures: Part 2 Gyratory compaction.

During 2013–14 these draft test methods will finalised based on use and feedback from the Working Group. To assist in this regard, testing will be undertaken to assess the significance of mixing moisture content on measured modulus and also the differences in modulus results between Marshall and gyratory compacted test cylinders. In addition, the following test methods will be drafted:

T313 Compaction of test slabs of foamed bitumen stabilised mixtures

T320 Curing of test cylinders of foamed bitumen stabilised mixtures

T321 Curing of test slabs of foamed bitumen stabilised mixtures

T330 Resilient modulus of foamed bitumen stabilised mixtures

T340 Deformation resistance of foamed bitumen stabilised mixtures by the wheel-tracking test.

9.2 Thickness Design In terms of the structural (thickness) design of FBS pavements, an under-designed FBS pavement was constructed on the Calder Freeway, Woodend, Victoria in March 2013. The trial involved the collaboration of VicRoads, industry and ARRB. The trial section was nominally 150 mm thickness of FBS, stabilised with 3.5% bitumen and 1.5% quicklime with a sprayed seal surfacing. The report describes the mix design, the construction process, testing during construction and the early-life performance monitoring. The findings to date are:

the very different project mix design results produced by two experienced laboratories highlighted the need for this Austroads project

when the FBS pavement was opened to traffic without the sprayed seal surface it ravelled and rutted in the first 24 hours but thereafter achieved a sound, stable basecourse of high modulus and high rut-resistance

eight days after construction, the FBS had cured such that cores were able to be taken from the pavement


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surface deflections taken at eight days and one month after construction were reasonably similar consistent with the view the FBS has quickly cured in the high temperatures in the first week after construction.

It is planned to monitor the performance of this pavement over the next three years.

In March 2011 an under-designed FBS pavement was constructed on Port Wakefield Road, Virginia South Australia. It consisted of a 100 m long section of nominal 150 mm thick FBS and about 900 m length of nominal 200 mm thick FBS. The existing calcrete limestone base was stabilised with nominal 3% bitumen and 1% hydrated lime. The pavement has a sprayed seal surfacing.

About 18 months after construction fatigue cracking was observed, reasonably consistent with the predictions of the Austroads interim structural design method. However, cores recovered from the nominal 150 mm thick section had very high bitumen contents (mean > 5%) possibly due to use of an inappropriate bitumen application rate. Consequently, there is doubt about the usefulness of the performance data of this material. In addition, about half of the cores taken from the nominal 200 mm thick FBS section had measured bitumen contents in excess of 5%, possibly due to the inclusion of asphalt patching materials and old sprayed seals. Again, there is doubt about the usefulness of the performance data at these sites. Further testing is required to clearly identify the pavement areas more typical bitumen contents which can be used to provide feedback on the structural design process.

In November 2011, the City of Canning in Perth, Western Australia constructed two short under-designed FBS sections, with nominal thicknesses of 150 mm (Section 1) and 100 mm (Section 2) on Kewdale Road, Welshpool. The host material was a mixture of crushed granite base and recycled asphalt, with a small quantity of crushed limestone subbase. The material was stabilised with nominal 3.5% bitumen and 0.8% hydrated lime and surfaced with 30 mm of dense graded asphalt.

Like the Calder Freeway trial, the Kewdale Road trial sections ravelled when the unsealed FBS base was opened to traffic on the day of construction. The asphalt surfacing has since covered this ravelling. After 18 months trafficking, the pavement is in good condition, with minimal rutting and no cracking. Surface deflections measured periodically since construction are consistent with that expected of high modulus FBS base. As the deflections measured seven weeks and 13 months after stabilisation were similar, the pavements appear to have fully cured within seven weeks of construction. There is no evidence yet that the FBS layers are deteriorating structurally due to trafficking. In 2013–14, cores will be taken from the pavement to confirm mix properties and layer thicknesses and deflection measurements repeated. Consideration will also be given to undertaking a mix design with the trial materials using the draft test methods.

In February 2010, Main Roads Western Australia constructed an under-designed pavement on Kwinana Freeway, Perth. The nominal 150 mm FBS layer was constructed by stabilising predominately hydrated cement treated crushed rock base (HCTCRB) with 3% bitumen and 0.8% hydrated lime. The surfacing over the FBS base comprised 30 mm open graded asphalt, geotextile reinforced seal and 30 mm dense graded asphalt. As this surfacing will inhibit fatigue cracking of the FBS layer reflecting through the surface, changes in measured surface deflections are being used to assess structural deterioration of the FBS layer.


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After three years of trafficking, the Kwinana Freeway pavement is in sound condition. The deflections indicate the FBS layer has not deteriorated structurally. As the pavement is constructed on a sand subgrade, the Austroads interim design method predicts a fatigue life of about 10 years, that is in 2020. As such, the pavement may not deteriorate structurally by the end of the research project in 2016. In 2013–14, the surface deflection measurements will be repeated.

The longest pavement section being monitored is a 17 km length of New England Highway, Allora, Queensland which was constructed in 1999. It is unusual in that the stabilisation depth was 250 mm in the outer wheelpath and 200 mm in the inner wheelpath. The cumulative traffic loading over the last 14 years has been about 2–3 x 106 ESA. There has been extensive longitudinal cracking along the project that has necessitated the placement of geotextile seals over about half the pavement length. This cracking does not appear to be fatigue cracking, rather cracking due to moisture changes in the highly plastic black soil subgrade. In addition to this longitudinal cracking, there are increasing areas of crocodile fatigue cracking consistent with performance predictions. Pavement coring/trenching and associated materials testing is required to improve the usefulness of the New England Highway data for performance prediction.

Three New Zealand sites were initially included in the monitoring program. Two of these pavements included FBS materials with a maximum particle size of 65 mm. Consequently, it is not possible to prepare laboratory-manufactured mixes to measure indirect tensile modulus and hence determine the FBS design modulus. Accordingly, it is proposed to discontinue monitoring these sites.

Similarly it is proposed to discontinue monitoring Somerton Road, Campbellfield, Victoria. This pavement was constructed in 1993 and has since been partially reconstructed. It also was stabilised with 3% cement works flue dust, not consistent with current practice.

During 2013–14, discussions will be held with road agencies and industry seeking opportunities to include additional under-designed pavement sections in the monitoring program.


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REFERENCES Austroads 2006, Guide to pavement technology: part 4D: stabilised materials, AGPT04D/06, Austroads,

Sydney, NSW.

Austroads 2011a, Guide to pavement technology: part 5: pavement evaluation and treatment design, AGPT05-11, Austroads, Sydney, NSW.

Austroads 2011b, Pavement roughness measurement with an inertial laser profilometer, test method AGAM/T001, Austroads, Sydney, NSW.

Austroads 2011c, Pavement rutting measurement with a multi-laser profilometer, test method AGAM/T009, Austroads, Sydney, NSW.

Austroads 2011d, Review of foamed bitumen stabilisation mix design methods, AP–T178/11, Austroads, Sydney, NSW.

Austroads 2011e, Review of structural design procedures for foamed bitumen pavements, AP–T188/11, Austroads, Sydney, NSW.

Austroads 2012, Guide to pavement technology: part 2: pavement structural design, AGPT02-12, Austroads, Sydney, NSW.

Clayton, B 2000, ‘Guidelines for site establishment and data collection for new long-term pavement performance site’, unpublished contract report, ARRB Transport Research, Vermont South, Vic.

Department of Planning, Transport and Infrastructure 2007, Construction of foamed bitumen stabilised pavement, specification part 224, DPTI, Adelaide, SA.

Department of Planning, Transport and Infrastructure 2011, ‘Traffic counts for Port Augusta: Port Wakefield/Port Wakefield Rd Site 6037 location 1.7 km south of RN 5000 (Angle Vale Rd)’, Spatial Intelligence and Road Assets Section, DPTI, Adelaide, SA.

Kendall, M, Baker, B, Evans, P & Ramanujam, J 2001, ‘Foamed bitumen stabilisation: the Queensland experience’, ARRB Transport Research conference, 20th, 2001, Melbourne, Victoria, ARRB Transport Research Ltd, Vermont South, Vic, 57 pp.

Main Roads Western Australia 2010, ‘Construction specification foamed bitumen stabilised trial Kwinana freeway’, MRWA, Perth, WA.

Main Roads Western Australia 2013, Procedure for the design of road pavements, engineering road note no. 9, MRWA, Perth, WA.

Ramanujam, J & Jones, J 2000, ‘Characterisation of foam bitumen stabilisation’, Road System and Engineering Technology Forum, 2000, Brisbane, Australia, Queensland Department of Main Roads, Brisbane, Queensland, 23 pp.

Ramanujam, J, Jones, J 2007, ‘Characterisation of foamed-bitumen stabilisation.’, International Journal of Pavement Engineering, 8:2, pp111-122.

Ramanujam, J, Jones, J & Janosevic, M 2009, ‘Design, construction and performance of insitu foamed bitumen stabilised pavements’, Queensland Roads, no.7, pp. 56–69.

Standards Australia 1997, Methods of sampling and testing asphalt: bitumen content and aggregate grading: pressure filter method, AS/NZS 2891.3.3:1997, Standards Australia, North Sydney, NSW.


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Strategic Highway Research Program 1989, SHRP LTPP manual for FWD testing: operational field guidelines, version 1, operational guide no. SHRP-LTPP-OG-002, SHRP, Washington DC, USA.


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APPENDIX A FIELD PERFORMANCE MONITORING PROCEDURES FOR LTPP SITES

A.1 Visual Inspection Procedure A.1.1 General The objective of the visual inspection of the LTPP and LTPPM sites was to record pavement surface defects that are not collected through pavement monitoring activities such as deflection testing, transverse (rutting) and longitudinal profile (roughness) measurements. The primary focus of this inspection is to collect cracking information while paying reasonable attention to other defects such as potholes, ravelling, shoving, flushing and patching, etc. The quality of the data collected is limited by the site conditions such as whether the site has traffic control arrangements in place. In most cases, traffic control arrangements are made during deflection testing activities which allow the inspector to walk on the test site and record the defects in detail.

A.1.2 Detailed Procedure With traffic control arrangements

Walk on the pavement and examine if there is any defect. Measure the parameters listed (Table A 1) according to the defect type and draw the defect on the LTPPM survey form. Where appropriate, record joint/crack width and number of potholes beside the sketch. Photographs of defects are also taken and a table recording pavement characteristics is collated.

In the event of inadequate light such as at night, visual inspection should still be carried out with the help of lights. However, safety shall not be compromised in any situation.

Without traffic control arrangements

Wear a safety vest and walk along the left shoulder while maintaining safe distances from the traffic (safety shall not be compromised in any situation) and look for pavement defects on the pavement test sections. Estimate/measure the defect parameters (Table A 1) and draw the defect on the LTPP/M survey form. Record the number of potholes and estimated joint/crack width (if appropriate) beside the sketch. Photographs of defects are also taken and a table recording pavement characteristics is collated.

Table A 1: Defect type and parameters to measure

Defect type Parameters to measure Sketch on the survey form Area

(m2) Length

(m) Joint/crack width (mm)

Number

Cracking: Crocodile Block Crescent Longitudinal Transverse Diagonal Meandering Corner


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Defect type Parameters to measure Sketch on the survey form Area

(m2) Length

(m) Joint/crack width (mm)

Number

Other defects: Potholes Ravelling Shoving Flushing Patching Joint seal defects Spalling

Notes: LTPPM survey form shall be used to record pavement surface defects. Summary of defects shall be reported in the LTPP/M Visual inspection summary form.

Table A 2: LTPP and LTPPM visual inspection (surface condition) summary

Study type: LTPP LTPPM Site ID Road name State Location

Survey date Weather Defect type Defect condition Cracking: Crocodile (area, m2) Block (area, m2) Crescent (area, m2) Longitudinal (length, m and crack width, mm) Transverse (length, m and crack width, mm) Diagonal (length, m and crack width, mm) Meandering (length, m and crack width, mm) Corner (area, m2) Other defects: Potholes (number and area, m2) Ravelling (area, m2) Shoving (area, m2) Flushing (area, m2) Patching (area, m2) Joint seal defects (length, m and crack width, mm) Spalling (length, m and crack width, mm) Texture


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Figure A 1: LTPP and LTPPM visual inspection survey form


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A.2 Rutting and Roughness Testing Procedures A.2.1 General In the Austroads LTPP study, pavement roughness (longitudinal profile) and rutting (transverse profile) are measured using the ARRB multi-laser profiler (MLP). The MLP is a fully integrated vehicle that uses thirteen laser units, two accelerometers and a high accuracy distance transducer to collect both longitudinal profile and transverse profile at highway speeds. The laser units which are mounted on a special assembly across the front of the vehicle are used to monitor several points across the width of the lane. Other lasers point out to the edges of the traffic lane, enabling data to be captured across a wide path. It also provides software to perform the calculation of roughness and rut depth from the measured longitudinal profile and transverse profile and report the test results.

ARRB provides general guidelines on MLP testing for LTPP sites (Clayton 2000). ARRB MLP test methods for measuring lane roughness and rut depth of the individual test sites in this Austroads project are briefly described below.

A.2.2 Roughness Roughness is measured with the MLP using the Austroads Test Method AG:AM/T001: Pavement Roughness Measurement with an Inertial Laser Profilometer (Austroads 2011b).

The measured roughness is expressed in terms of the International Roughness Index (IRI) and can be reported in different ways, as follows:

single track IRI: The IRI based on a quarter car model run over a single wheelpath of longitudinal profile

lLane IRI: This is a composite IRI value representing the roughness of a road lane section. It is determined by averaging two individual single track IRI values obtained separately in each wheel-path of a lane (at 0.75 metres either side of the lane mid-track).

Readings of single track IRI and lane IRI are taken for each 10 m sub-section along the two wheelpaths of each pavement section.

A.2.3 Rutting Rutting is measured with the MLP using the Austroads Test Method AG:AM/T009: Pavement Rutting Measurement with a Multi-laser Profilometer (Austroads 2011c).

It is calculated using the taut wire method (also known as the stringline method) – an imaginary wire is stretched across the transverse profile enveloping the high points and fixed at either end. Rutting is defined as the maximum gap under the string line in each wheelpath. It can be reported in different ways, as follows:

Wheelpath rutting: the maximum rut depth across the transverse profile of each wheelpath

Lane rutting: the maximum rut depth across the entire transverse profile of the lane.

Readings of wheelpath rutting and lane rutting are taken nominally at 10 m intervals along the two wheelpaths of each pavement section.


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A.2.4 Site Establishment For each test site, GPS should be established for the start and end locations of each 100 m test section and these locations should also be marked with road nails for future measurements. Furthermore, it is suggested that each 10 m interval be marked with sprayed paint or survey nails to assist with the acquisition of the monitoring data. A marker post at the site would also assist in site identification.

A site diagram should be prepared to show the following locations:

marker post at the site for identification

start of Section 1 (i.e. at 0 m chainage and 0 m offset)

end of Section 1 or the start of Section 2 (i.e. at 100 m chainage and 0 m offset)

end of Section 2 (i.e. at 200 m chainage and 0 m offset)

MLP test locations for reporting the measured roughness and rutting data.

A.2.5 MLP Testing MLP operators must properly record the GPS of the permanently marked road nails (start and end reference stations of each test section) for future measurements of distances of the MLP test locations (for reporting the measured roughness and rutting data for each section).

All MLP testing is done in the driving lane of the test section by following the marked wheel-path tracks. All testing uses the distance reference at the start reference station of the test section so all MLP test point locations can be located for future reporting. When finished with a particular pass, the MLP returns to the beginning of the section to start another pass.

Five passes through the test section are made to collect five sets of MLP data. The ARRB MLP data collection software will be used to select the three most consistent sets of data for further analysis of mean values of wheelpath rutting, lane rutting, single track IRI and lane IRI for each MLP test location.

A.2.6 Reporting Data The ARRB MLP data collection software will be used to record surface profiles from all 13 laser sensors. Binary MLP data files shall be provided for verification purposes.

For each MLP survey, mean values (from three MLP runs) of wheelpath rutting, lane rutting, single track IRI and lane IRI for each test point (ID, GPS location) shall be reported in ASCII format or Excel spreadsheet for display and verification purposes.

A.3 Falling Weight Deflectometer Testing Procedures A.3.1 General In the Austroads LTPP study, the falling weight deflectometer (FWD) was used to measure the surface deflection of the pavement test sections under a series of applied loads. All testing nominally adhered to the SHRP-LTPP Protocol (SHRP 1989). This protocol is now administered by the Long-Term Pavement Performance (LTPP) Division in the U.S. Department of Transportation Federal Highway Administration (see LTPP Manual for Falling Weight Deflectometer Measurements Operational Field Guidelines Version 3.1 August 2000). Different FWD testing protocols may be assigned to different LTPP pavement test sections in the LTPP program, depending on experiment categories, pavement types and pavement conditions.

This appendix provides guidelines and information specific to FWD testing at individual test sites.


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A.3.2 Detailed Test Plan The following FWD test plan will be used for the test pavement of 100 m long x 3.8 m wide:

1 Lane for each FWD pass at two transverse locations: outer wheelpath (OWP) at 0.76 m ± 0.08 m and mid-lane (ML) at 1.8 m ± 0.15 m for nominal 3.7 m wide lane.

2 Test interval (longitudinal location): begin at station 0 m chainage and continue to station 100 m at 10 m intervals.

3 Deflection sensor spacing: nine deflection sensors placed at radial offsets from the centre of the load plate to define the shape of the deflection basin.

4 Drop sequence (load levels/number of drops): three drop heights are to be used with the target loads of 30 kN, 40 kN and 50 kN. The drop sequence consists of three seating drops of 40 kN and four repeat measurements at each of the specified target loads.

5 Test point ID: tests at ML use the lane name F1 and tests in the OWP using the lane name F3.

The test plan includes 10 FWD tests on each pass down the test section for both the ML and the OWP. Each section has 20 test points. The FWD testing will take about one hour.

Note that two types of deflectometers, namely falling weight deflectometer (FWD) and heavy weight deflectometer (HWD), have been used in the LTPP program. The FWD devices were used until the 1997 data collection and beyond that the HWD device was used. Deflection results are plotted assuming both devices would provide the same values. Currently deflection measurements are conducted primarily using the HWD with the smoothing function on, so that the deflections are similar to those measured with the FWD.

A.3.3 FWD Testing FWD operators must properly record longitudinal distances with the distance measuring instrument relative to the 0+00 station reference for each section, and follow the guidelines for lateral offset for the OWP and ML passes, so all FWD testing can be repeated in the same general location.

All FWD testing is done in the driving lane at two lateral offsets. The two lateral offsets are the ML and OWP. For a given lateral offset, a single pass through the test section is made to collect a particular type of deflection data. When finished with a particular pass, the FWD returns to the beginning of the section to start another pass. All testing uses station 0 m chainage of the test section as the distance reference so FWD test point locations can be located for future testing.

A.3.4 Temperature Gradient Measurements The thermal gradient (temperature versus depth) through the bound pavement surface layer is important for the analysis of deflection data. The automatic temperature sensors on the FWD record air temperature and pavement surface temperature. To provide a direct measure of the temperature gradient through the surface, FWD operators shall measure the temperature of oil placed in holes, drilled to different depths, during deflection testing.

The basic procedure consists of drilling three holes into the bound surface layer, filling each hole with approximately 25 mm of oil, and using a hand-held temperature probe to measure the temperature of the oil at one hour intervals during the conduct of deflection testing.

Temperature measurements are obtained at only one location for each test section. The FWD operator should assess variations in sun exposure and wind conditions to select the most representative location adjacent to the section limits for temperature measurements.


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Temperature readings are obtained at 20 minute intervals, with the first readings prior to starting FWD testing on the section and the last readings after completion of FWD testing at the section.

A.3.5 Crack Widths No crack opening measurements are made; however, FWD operators must record pavement distress at test point locations as described in guidelines for GPS testing using the Comment key.

A.3.6 Calibration As a minimum, any FWD collecting data for the LTPP study is required to undergo a full calibration (including both reference and relative calibration) at least once per year. The calibration of the FWD must strictly follow the SHRP/LTPP FWD Calibration Protocol (March 1994).

A.3.7 Reporting Data The Dynatest FWD data collection software will be used to record deflections from all nine sensors. Deflection data files shall be provided for verification purposes.

Detailed results of the FWD testing (including test point ID, location, FWD load, results of deflections from all nine sensors of the final drop of each target load, air temperature, pavement temperature, date and time) shall be reported in ASCII format or Excel spreadsheet for display and verification purposes.

The last FWD reference calibration results should be given for verification purposes.

INFORMATION RETRIEVAL

Austroads, 2013, Design and Performance of Foamed Bitumen Stabilised Pavements: Progress Report One, Sydney, A4, pp. 98. AP-T247-13.

Keywords: Pavement design, rehabilitation, foamed bitumen, stabilisation, recycling, mix design, construction, field performance, validation.

Abstract: This report is the first progress report of a four year project which aims to improve the Austroads procedures for the mix and structural design of foamed bitumen stabilised materials.

The report summarises the test methods drafted to date and details the results of monitoring foamed bitumen stabilised pavement trial sites on:

the Calder Freeway at Woodend, Victoria which was constructed specifically for this project in 2013

Port Wakefield Road in Virginia, South Australia constructed in 2011 and which experienced fatigue cracking within two years of opening to traffic

Kewdale Road in Canning, Western Australia constructed in 2011 and which experiences shear stresses due to braking and acceleration of heavy vehicles

the Kwinana Freeway in Perth, Western Australia constructed in 2010, and

the New England Highway south of Toowoomba, Queensland constructed in 2009.

The report also identifies the mix design and structural design project tasks for 2013–14.

Documents

Design and Performance of Foamed Bitumen Stabilised Pavements - Progress Report 1