United States Department of Transportation
i
Performance testing for superpave and structural validation.
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2012-11-01
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[PDF-5.61 MB]
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Edition:Final report.
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NTL Classification:NTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and Performance
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Abstract:The primary objective of this full-scale accelerated pavement testing was to evaluate the performance of unmodified
and polymer modified asphalt binders and to recommend improved specification tests over existing SUperior
PERforming Asphalt PAVEment (Superpave®) binder performance grading methodologies. Candidate replacement
tests were evaluated via their ability to discern fatigue cracking resistance and rutting. Two fatigue cracking
specification tests were identified as more capable in capturing performance than others: binder yield energy and
critical tip opening displacement. Two rutting specification tests that quantify irrecoverable deformations exhibited
the best strength to capture rutting: multiple stress creep and recovery and oscillatory-based nonrecoverable stiffness.
Based on the full-scale performance and laboratory tests, crumb rubber (recycled tires) modified asphalt (Arizona wet
process) was shown to significantly slow or stop the growth of fatigue cracks in a composite asphalt pavement
structure. A hybrid technique to modify asphalt with a combination of crumb rubber and conventional polymers
(terminally blended) exhibited good fatigue cracking resistance relative to the control binder. Also, a simple
addition of polyester fibers to asphalt mix was shown to have high resistance to fatigue cracking without the use
of polymer modification.
The research study also quantified the capabilities of the National Cooperative Highway Research Program’s
mechanistic-empirical pavement design and analysis methodologies to predict rutting and fatigue cracking of
modified asphalts that were not captured in the calibration data from the Long-Term Pavement Performance program.
Falling weight deflectometer, multidepth deflectometer, and strain gauge instrumentation were used to measure
pavement response. The results illustrated that the nationally calibrated mechanistic-empirical performance models
could differentiate between structural asphalt thickness but had difficulty differentiating modified from unmodified
asphalt binder performance. Nonetheless, the mechanistic-empirical performance ranking and predictions were
enhanced and improved using mixture-specific performance tests currently being implemented using the asphalt
mixture performance tester.
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