1. Asphalt Pavement Solutions – For Life
ASPHALT MASTER CLASS
NOVEMBER 2012
Update - AAPA Project
Asphalt Pavement Solutions – For Life
Development and calibration of a Long Life Asphalt Pavement design methodology
The Australian asphalt industry – through AAPA - have embarked on a major research project entitled ‘asphalt pavement solutions – for life’
The title reflects industry’s objective to provide asphalt pavement structures with a very long service life – known colloquially as the perpetual pavement.
Ian Rickards
Consultant, AAPA

2. Background
International recognition of long life / perpetual asphalt pavement performance
LLAP’s get stronger with time i.e. deflections reduce
Poor correlation between laboratory / field fatigue performance i.e. basic design criterion dubious
Observed LLAP performance explained by:
Fatigue endurance limit
Healing
AAPA project aims to develop, calibrate and implement a relevant design method

3. National asphalt characterisation study Dynamic modulus E*
ASPHALT MATERIALS PERFORMANCE TESTER (AMPT)
If we are to design asphalt pavements by reference to a limiting cumulative distribution of asphalt strain it is imperative that we know the distribution of asphalt stiffness over the operating temperature spectrum.
Our ability to characterise asphalt properties over the full temperature and load frequency spectrum is enabled by the AMPT. This is an automated cyclical compression test under triaxial stress conditions and at higher temperatures a confining stress is applied replicating field conditions.
Asphalt samples from either the laboratory or manufacturing plant are tested at a range of temperature and load frequency.
Output data is the dynamic modulus i.e. the ratio of the applied stress to the resulting strain, and the phase lag between load application and response from which is calculated the relative elastic and viscous components of the mix which provides an indication of the relative deformation resistance of the material.

4. Master curve for asphalt characterisation
These parameters are derived from laboratory testing, and will be used in modified CIRCLY software to define asphalt properties over the spectrum of pavement temperature and load speed

5. Binder characterisation Complex shear modulus G*
The G* parameter is shown in literature to provide a more accurate prediction of E*

6. Field Strain Studies - NCAT Test Track
The National Centre for Asphalt Technology is among the leaders in long life pavement research. Their resource level and focus on field performance combined with the measurement of critical performance measures is unique.
Their field research involves the physical measurement of the pavement temperature and stress distribution regime under full scale traffic loading
In all the NCAT test track comprises some 44 test sections. Some 26 sections on the straights are primarily for structural performance measures. Each is instrumented to measured temperature and strain parameters to permit evaluation and correlation with observed performance 6

7. APS-FL Project background and motivation
CORRELATION OF STRAIN DISTRIBUTION AND PERFORMACNE
Fatigue
No Fatigue
Analysis of the NCAT research data to 2006 on the 16 sites shown on this plot enables the calculation of the cumulative distribution of asphalt strain repetitions measured over the four seasons. The comparison of the observed performance of each section then enables the extremely valuable correlation between performance and design criteria such as asphalt strain.
The results have led to the extremely promising conclusion that the fatigue endurance limit may be related to the cumulative distribution of strain rather than a single laboratory value. This is considered a more realistic parameter given the anticipated spectrum of pavement temperature and the consequent asphalt stiffness and strain.
In thick asphalt pavement structures the applicability of the classical asphalt fatigue models are now questioned by international agencies.

8. APS-FL Project background and motivation
CORRELATION OF STRAIN DISTRIBUTION AND PERFORMACNE
Fatigue
No Fatigue
The validation phase of the AAPA project involves the analysis of LLAP sections at NCAT and in Europe (primarily UK).
Analysis of the NCAT research data to 2006 on the 16 sites shown on this plot enables the calculation of the cumulative distribution of asphalt strain repetitions measured over the four seasons. The comparison of the observed performance of each section then enables the extremely valuable correlation between performance and design criteria such as asphalt strain.
The results have led to the extremely promising conclusion that the fatigue endurance limit may be related to the cumulative distribution of strain rather than a single laboratory value. This is considered a more realistic parameter given the anticipated spectrum of pavement temperature and the consequent asphalt stiffness and strain.
In thick asphalt pavement structures the applicability of the classical asphalt fatigue models are now questioned by international agencies.

9. APS-FL Project background and motivation
CURRENT AUSTROADS DESIGN METHOD
PROPOSED ASP-FL
LLAP DESIGN METHOD
Asphalt Characterisation
Design Modulus and traffic speed)
Asphalt Characterisation
Dynamic Modulus (Spectrum of temperature & traffic speeds)
Select trial asphalt thickness for analysis
Select trial asphalt thickness for analysis
Design Traffic
Refine design thickness
Refine design thickness
Calculate critical strain using CIRCLY
Calculate cumulative strain distribution using CIRCLY
Examine performance using Shell fatigue criterion
Confirm conformance using LTPP & NCAT field test data

10. MASTER CLASS 2011
Proposed methodology subjected to peer review by local and international expert group post 2011 AAPA Conference.
Preliminary endorsement of the APS-FL concepts
No fundamental flaws identified

11. MASTER CLASS OUTCOMES

12. MASTER CLASS OUTCOMES

13. National asphalt materials characterisation study
Study components
Dynamic modulus E* using AMPT
Binder complex shear modulus G* using DSR
Scope of materials:
Commercial project mixes ex production plant
30 mixes in total: 16 x AC14: 14 x AC20
Binders: C 320; C 450; C 600; A15E; Multigrade

16. National asphalt materials characterisation study
Status – Australian laboratory testing
Local laboratory asphalt testing complete
36 master curves includes repeats
Local laboratory DSR testing complete for each of 5 bitumen types; includes:
As delivered bitumen
Bitumen after RTFO
Mastic – bitumen plus filler
Recovered binder

17. National asphalt materials characterisation study
Status – NCAT laboratory correlation study
Triplicate cylinders of 4 mixes (C 600 to come) testing complete
Uncompacted samples of 2 mixes provided –proceeding
Anticipate completion end November

18. RESULTS OF NCAT LAB CORRELATIONS
4oC
20oC
35oC
50oC

19. RESULTS OF NCAT LAB CORRELATIONS

20. RESULTS OF NCAT LAB CORRELATIONS

21. RESULTS OF NCAT LAB CORRELATIONS

22. LABORATORY MIX PERFORMANCE CHARACTERISTICS COMPARED – NIL CONFINEMENT

23. APS-FL Project background and motivation
CORRELATION OF STRAIN DISTRIBUTION AND PERFORMACNE
Fatigue
No Fatigue
The validation phase of the AAPA project involves the analysis of LLAP sections at NCAT and in Europe (primarily UK).
Analysis of the NCAT research data to 2006 on the 16 sites shown on this plot enables the calculation of the cumulative distribution of asphalt strain repetitions measured over the four seasons. The comparison of the observed performance of each section then enables the extremely valuable correlation between performance and design criteria such as asphalt strain.
The results have led to the extremely promising conclusion that the fatigue endurance limit may be related to the cumulative distribution of strain rather than a single laboratory value. This is considered a more realistic parameter given the anticipated spectrum of pavement temperature and the consequent asphalt stiffness and strain.
In thick asphalt pavement structures the applicability of the classical asphalt fatigue models are now questioned by international agencies.

24. Data base
AAPA acknowledges the work done by Bevan Sullivan in preparation of an Access data base whilst ensuring confidentiality of the data sources
The data base will greatly assist in the data analysis
On finalisation AAPA anticipate the data base will be made available to ARWG members and other researchers to provide a basis for national data collection

25. Binders characterisation – preliminary analysis
Literature indicates E* is a function of G*
Higher G* yields higher E*
Mix E* higher temperature
A15E
C 320
C 600
AR 450 (with 15% RAP)
Multigrade
Preliminary binder G* ranking inconsistent

28. Binders characterisation – preliminary analysis
Preliminary observation is that phase angle is substantially effected by binder type and filler
Models appear inconsistent based only on G*
Perhaps improved relationship comparing Gʹ or Gʺ (PhD topic!)

29. Data analysis for materials modeling
Doctoral candidate Saeed Yousefdoost’s project (supervisor Binh Vuong)
Calibrate predictive models Witczak and Hirsch using local mix volumetrics and binder properties
Review results from the NCAT lab testing of our materials and establish correlation with our test results

30. Field calibration of LLAP design models
A cooperative two-pronged approach
Austroads project to enhance the design of asphalt pavements (Dr Erik Denneman project leader)
Will source data on the performance of UK LLAP sections for ARRB TR and AAPA evaluation
Will explore US NCHRP 9-44a project to introduce fatigue endurance limit and healing
AAPA will liaise with NCAT and access their field trials and data to calibrate laboratory / field E* relationship
A very positive direction that may substantially advance the outcomes and so minimise waste and risk, and enhance the sustainability of asphalt pavements

31. Calibration of materials models - AAPA
With confirmation that our mix characteristics correlate we can utilise NCAT performance data with confidence
Access NCAT full scale pavement trial data
Correlate dynamic modulus estimates from back analysis of deflection data
Request made of NCAT to advise the results of their studies into the laboratory / field estimates of E* relationship
Publication believed to be imminent

32. NCAT DATA Substrate conditions / bearing capacity
Accurate layer dimensions
Load pulse shape and duration
Temperature profile at deflection test
Wheel load and strain response
Combined data will provide unique ability to improve precision in E* estimates
Adequacy of design assumptions endorsed when generated and measured cumulative strain distributions correlate

33. Calibration of materials models - AAPA
NCAT have agreed to work with us in alliance
First approach is a formal follow up on their correlation studies / conclusions
Next issue is the mechanics of how we can access raw data for our analysis and avoid overwhelming
Physical exchange of personnel would seem the optimum solution – candidates?

34. Additional field trials – significant potential
Both U Sunshine Coast and U Curtin have acquired AMPT
Both facilities are working with road agencies to construct and instrument field trials
AAPA has an advisory role to assist the selection and placement of instrumentation to ensure best data for laboratory correlations
The universities offer the very great benefit of an ongoing stream of candidates to ensure the continuity of monitoring and analyses over time

35. Summary and conclusions
The AAPA LLAP design concept has been peer reviewed and has preliminary endorsement
The national asphalt mix characterisation study is near completion with good correlation with NCAT
The critical validation phase is underway and LTPP data is available to calibrate the limiting distribution of strain
LLAP implementation will incorporate thickness design, material design and construction guidelines – the latter is equally or more vital to LLAP

36. Asphalt Pavement Solutions – For Life
ASPHALT MASTER CLASS
NOVEMBER 2012
Update - AAPA Project
Asphalt Pavement Solutions – For Life
Development and calibration of a Long Life Asphalt Pavement design methodology
The Australian asphalt industry – through AAPA - have embarked on a major research project entitled ‘asphalt pavement solutions – for life’
The title reflects industry’s objective to provide asphalt pavement structures with a very long service life – known colloquially as the perpetual pavement.
Ian Rickards
Consultant, AAPA