United States Department of Transportation
i
HMA shear resistance, permanent deformation, and rutting tests for Texas mixes : final year-2 report.
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2014-11-01
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[PDF-13.92 MB]
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Abstract:Traditionally run at one test temperature (122°F), the Hamburg wheel tracking test (HWTT) has a proven
history of identifying hot mix asphalt (HMA) mixes that are moisture susceptible and/or prone to rutting. However,
with the record summer temperatures of the recent years, several shear and rutting failures have occurred with HMA
mixes that had passed the HWTT in the laboratory. For the most part, failures occurred in high shear locations,
particularly with slow-moving traffic at controlled intersections (accelerating/decelerating), stop-go sections, elevated
temperatures, heavy/high traffic loading, and where lower PG asphalt-binder grades have been used.
This two-year study was undertaken to improve the performance of the existing laboratory rutting-shear tests
including the HWTT in simulating the field rutting conditions of the HMA and exploring new supplementary and/or
surrogate HMA rutting/shear tests. In particular, a potential surrogate test should be able to discriminate HMA mixture
performance for application in high shear stress areas (i.e., intersections) as well as discern temperature thresholds at
which a given HMA mix, with a given PG asphalt-binder grade, becomes unstable and more prone to rutting and/or
shear failure.
In line with these objectives, this final project report documents the research work completed in this study.
Several of the existing HMA rutting-shear tests were comprehensively evaluated with special focus on the HWTT.
Researchers propose several enhancements to the HWTT protocol that are expected to improve its overall performance
in predicting HMA rutting susceptibility. Additionally, a new supplementary HMA shear test, namely the simple
punching shear test (SPST) was developed that showed good potential to be considered as a surrogate to the HWTT.
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