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0-6744-1 Report Abstract

HMA Shear Resistance, Permanent Deformation, and Rutting Tests for Texas Mixes: Year-1 Report

Lubinda F. Walubita, Sang Ick Lee, Jun Zhang, Abu NM Faruk, Stan Nguyen, and Tom Scullion, April, 2014

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; mostly in high shear locations, in particular with slow moving (accelerating/decelerating) traffic at controlled intersections, stop-go sections, in areas of elevated temperatures, heavy/high traffic loading, and/or where lower PG asphalt-binder grades have been used.

As a supplement to the HWTT, this two-year study is being undertaken to develop a simpler and less time consuming shear resistance and permanent deformation (PD)/rutting test that is also cost-effective, repeatable, and produces superior results in terms of correlation with field rutting performance. In particular, such a test should have the potential to discriminate HMA mixes for application in high shear stress areas (i.e., intersections) as well as being an indicator of the critical temperatures 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 interim report documents the research work completed in Year-1 of the study, namely: a) data search and literature review; b) computational modeling and shear stress-strain analysis; c) comparative evaluation of the Asphalt Mixture Performance Tester (AMPT) and the Universal Testing Machine (UTM); d) comparative evaluation of the Flow Number (FN), Dynamic Modulus (DM), and Repeated Load Permanent Deformation (RLPD) tests relative to the HWTT test method.

Keywords: HMA, Rutting, Shear, Permanent Deformation (PD), Stress, Strain, Visco-elastic, Hamburg (HWTT), UTM, AMPT, Flow Number (FN), Dynamic Modulus (DM), Repeated Load Permanent Deformation (RLPD), Finite Element (FE), Shear Strength, Modulus

ENTIRE REPORT (Adobe Acrobat File – 4.9 MB)