The following is extracted from the NCHRP report 465.
The Superpave volumetric mix design procedure developed in the Asphalt Research Program (1987–1993) of the Strategic Highway Research Program (SHRP) does not include a simple, mechanical “proof” test analogous to the Marshall stability and flow tests or the Hveem stabilometer method. Instead, the original Superpave method relied on strict conformance to the material specifications and volumetric mix criteria to ensure satisfactory performance of mix designs intended for low-traffic-volume situations (defined as no more than 106 equivalent single axle loads [ESALs] applied over the service life of the pavement). For higher trafficked projects, the original SHRP Superpave mix analysis procedures required a check for tertiary creep
behaviour with the repeated shear at constant stress ratio test (AASHTO TP7) and a rigorous evaluation of the mix design’s potential for permanent deformation, fatigue cracking, and low-temperature cracking using several other complex test methods in AASHTO TP7 and TP9.
User experience with the Superpave mix design and analysis method, combined with the long-standing problems associated with the original SHRP Superpave
performance models supporting what was then termed “Level 2 and 3” analyses, demonstrated the need for such simple performance tests (SPTs). In 1996, work sponsored by FHWA began at the University of Maryland at College Park (UMCP) to identify and validate SPTs for permanent deformation, fatigue cracking, and low-temperature cracking to complement and support the Superpave volumetric mix design method. In 1999, this effort was transferred to Task C of NCHRP Project 9-19,
“Superpave Support and Performance Models Management,” with the major portion of the task conducted by a research team headed by UMCP subcontractor Arizona State University (ASU).
The research team was directed to evaluate as potential SPTs only existing test Methods measuring hot mix asphalt (HMA) response characteristics. The principal evaluation criteria were (1) accuracy (i.e., good correlation of the HMA-response characteristic to actual field performance); (2) reliability (i.e., a minimum number of false negatives and positives); (3) ease of use; and (4) reasonable equipment cost.
The research team conducted a comprehensive laboratory testing program to statistically correlate the actual performance of HMA materials from the MnRoad, Wes-Track, and FHWA Accelerated Loading Facility (ALF) experiments with the measured responses of specimens prepared from original materials for 33 promising test method–test parameter combinations.
88 Appendices
Based on the results of this testing program, the research team recommends three test-parameter combinations for further field validation as an SPT for permanent deformation: (1) the dynamic modulus term, E*/sinφ, (determined from the triaxial dynamic modulus test; (2) the flow time, Ft, determined from the triaxial static creep test; and (3) the flow number, Fn, determined from the triaxial repeated load test. All combinations exhibit a coefficient of determination, R2, of 0.9 or greater for the combined correlation of the laboratory test results with performance in the MnRoad, Wes-Track, and FHWA ALF experiments.
For fatigue cracking, the experimental results are far less conclusive. The research team recommends the dynamic modulus, E*, measured at low test temperatures; the modulus offers a fair correlation with field performance data and provides some consistency with one of the tests recommended for permanent deformation. For low temperature cracking, the team recommends the creep compliance measured by the indirect tensile creep test at long loading times and low temperatures; this
recommendation is based solely on work carried out for SHRP and C-SHRP and recently confirmed in NCHRP Project 1-37A, “Development of the 2002 Guide for the Design of New and Rehabilitated Pavement Structures.”
The NCHRP report 465 includes a detailed description of the experimental program, a discussion of the research results and the basis for selection of the candidate SPTs, a description of the future field validation effort, and five supporting appendixes presenting test methods for the candidate SPTs:
In Australian practice the dynamic modulus E* master curve is developed from testing at 4 temperatures (5o; 20o;35o & 50oC) and 6 load frequencies (0.1; 0.5; 1; 5;
10 & 25 Hz) using time temperature superposition principles. From this testing the response to load performance of candidate asphalt materials can be measured over the extremes of temperature and load duration. This data is then able to be used in HIPAVE to calculate damage over the full temperature spectrum.
The dynamic modulus master curve clearly distinguishes the benefits of modified binders by quantifying the improvement in stiffness and elastic response at high temperature and/or slow loading conditions. This is particularly advantageous because historical modulus measurements at a single temperature (typically 20o or 25oC) often fail to discriminate between conventional and modified binders.
Further research into the effect of confinement in the field is needed. Intuitively the significant increase in dynamic modulus and elasticity (reduction in phase angle) observed in the triaxial cell with confining pressure is likely in the field. Early work by Marchionna et al supports this intuition by the observation that deflections on thick asphalt pavement structures did not appear to increase with temperature.
In applications in the industrial pavement environment the deformation relationships between Dynamic modulus (E*) and elasticity (Sine phase angle) will require
calibration. In the interim the empirical evidence suggest adhering to the
fundamentals will yield good performance i.e. using all crushed aggregate; dense gradation; hard binder grades in hot environs; binder content optimization at appropriate laboratory compaction effort. Wheel-track testing may provide a reasonable ranking of deformation resistance in the laboratory.
development we tend to use the laboratory fatigue test more to verify the predictive fatigue models developed by Shell and implemented by Austroads. As more performance evidence is gained the apparently conservative predictive models will be recalibrated.
Of value is the use of the fatigue test to develop appropriate damage models for innovative materials. Figure 14 below compares the fatigue performance of conventional asphalt against the resin modified asphalt PRS Rigiphalte.
Figure 14: Fatigue performance of conventional asphalt against the resin modified asphalt PRS Rigiphalte.
Comparison of fatigue properties Rigiphalte and AC14 C320 Constant strain; 20oC; 10 Hz
10
The Dynamic Shear Rheometer (DSR) is another laboratory tool to enhance the selection of the best bitumen and filler combination to enhance mix properties. In common with the SPT the DSR provides the material characterisation over the full combination of temperature and loading frequency. The DSR can test bitumen and the bitumen filler mastic to develop complex shear modulus master curves, and to measure the elastic and viscous component of the binder. These latter parameters are considered to be significant in both fatigue and deformation resistance potential.
In application available binders and fillers would first be characterised and then the binder exhibiting the most potential would be incorporated in asphalt samples to determine the (more arduous) dynamic modulus master curve evaluation.
References
ASCE (2001). Soil Behavior and Soft Ground Construction. Geotechnical Special Publication No 119. American Society of Civil Engineers, New York.
Austroads (2004). Pavement Design- A Guide to the Structural Design of Road Pavements. Austroads Publication No. AP-G17/04.
Austroads (2006a). Fatigue Life of Compacted Bituminous Mixes Subject to Repeated Flexural Bending. Test Method AGPT/T233, Austroads.
Austroads (2006b). Guide to Pavement Technology - Part 4D: Stabilised Materials.
Austroads Publication No. AGPT04D/06.
British Ports Association (1986). The Structural Design of Heavy Duty Pavements for Ports and other Industries, 2nd ed., British Ports Federation, London.
British Ports Association/Interpave (1996). The Structural Design of Heavy Duty Pavements for Ports and other Industries, 3rd ed., Interpave, Leicester.
Barker, W. and Brabston, W. (1975). Development of a structural design procedure for flexible airport pavements. Report No. S-75-17. US Army Corps of Engineers, Waterways Experiment Station, Vicksburg, Miss.
Dickinson, E.J. (1981). Pavement Temperature Regimes in Australia: Their Effect on the Performance of Bituminous Constructions and their Relationship with Average Climate Indicators, Special Report 23, Australian Road Research Board, Victoria, Australia.
Shell, 1978, Shell Pavement Design Manual : Asphalt Pavements and Overlays for Road
Haas, R., Hudson, W. R., and Zaniewski, J. P. (1994). Modern Pavement Management. Krieger Publishing Company. Malabar, Florida.
Jacob, A. (2006). Personal Communication.
Jameson. G. W. (1995). Response of Cementitious Pavement Materials to Repeated Loading. ARRB Contract Report RI 949.
Lancaster, J. (2006). Unpublished Report.
NCHRP (2002). Simple performance test for Superpave mix design. Report 465 Washington, D.C.: National Academy Press.
Rickards, I., Gabrawy, T., Sullivan, B. and Tighe, S. (2006) Application of the Simple Performance Test and Complimentary Equipment in Australia. Proc 10th ICAP conference Quebec
Rodway, B. (1995a). Design Of Flexible Pavements For Large Multiwheeled Aircraft.
Int. Conf. on Road & Pavement Technology, Singapore, 27-29 September, 1995.
Rodway, B., Wardle, L.J. and Wickham, G. (1999). Interaction between wheels and wheel groups of new large aircraft. Airport Technology Transfer Conference, Atlantic City, U.S.A., April 1999, Federal Aviation Administration.
Rollings, M.P. and Rollings, R.S. (2005). Geology: Engineer Ignore It at Your Peril.
J. Geotech. and Geoenvir. Engrg., Volume 131, Issue 6, pp. 783-791. American Society of Civil Engineers, New York.
Smallridge, M. and Jacob, A. (2001). The ASCE Port and Intermodal Yard Pavement Design Guide. Ports 2001 Conference: America’s Ports - Gateway to the Global Economy. April 29–May 2, 2001, Norfolk, Virginia, USA (Collins, T. J. – ed.).
Standards Australia (1997). Residual bitumen for pavements. AS 2008-1997, Standards Australia, Sydney, Australia.
Tighe, S., Zhiwei He and Haas R. (2001). Environmental Deterioration Model For Flexible Pavement Design: An Ontario Example, National Academy Press,
92 References
Washington, D.C., Transportation Research Record No. 1755, pp.81-89.
US Department of Army & Air Force Technical Manual (TM 5-825-2-1 and TAFM 88-6) (November 1989). Flexible Pavement Design For Airfields.
Wardle, L. J. (1999a). APSDS 4.0 – Airport Pavement Structural Design System Users’ Manual, Mincad Systems Pty Ltd, Richmond, Vic., Australia.
(www.mincad.com.au)
Wardle, L. J. (1999b). Development of APSDS (Airport Pavement Structural Design System) for Light Commuter Aircraft. Unpublished Report.
Wardle, L. J. (2004). CIRCLY 5.0 Users’ Manual, Mincad Systems Pty Ltd, Richmond, Vic., Australia. (www.mincad.com.au)
Wardle, L. J. (2005). HIPAVE User Manual, Mincad Systems Pty Ltd, Richmond, Vic., Australia. (www.mincad.com.au)
Wardle, L.J. and Rodway, B. (1995). Development and Application of an Improved Airport Pavement Design Method. ASCE Transportation Congress, San Diego, 22-26 October, 1995. (www.mincad.com.au/HIPAVE_Papers.htm)
Wardle, L.J. and Rodway, B. (1998a). Layered Elastic Pavement Design- Recent Developments. Proceedings Transport 98, 19th ARRB Conference, Sydney, Australia, 7-11 December. (www.mincad.com.au/HIPAVE_Papers.htm) Wardle, L.J. and Rodway, B. (1998b). Recent Developments in Flexible Aircraft Pavement Design using the Layered Elastic Method. Third Int. Conf. on Road and Airfield Pavement Technology, Beijing, April 1998.
(www.mincad.com.au/HIPAVE_Papers.htm)
Wardle, L.J., Rodway, B. and Rickards, I. (2001). Calibration of Advanced Flexible Aircraft Pavement Design Method to S77-1 Method. in Advancing Airfield Pavements, American Society of Civil Engineers, 2001 Airfield Pavement Specialty Conference, Chicago, Illinois, 5-8 August 2001 (Buttlar, W.G. and Naughton, J.E, eds.), pp. 192-201. (www.mincad.com.au/HIPAVE_Papers.htm)