Journal Published Online: 29 January 2016
Volume 45, Issue 2

Determining Specimen Geometry of Cylindrical Specimens for Direct Tension Fatigue Testing of Asphalt Concrete



This paper presented a specimen geometry study of cylindrical specimens used in the direct tension cyclic (DTC) fatigue testing of asphalt concrete using an asphalt mixture performance tester. The current specimen geometry for DTC fatigue testing is 100 mm in diameter and 150 mm in height with a linear variable differential transducer (LVDT) gauge length of 70 mm in the middle of the specimen. In order to use the displacement data for mechanistic fatigue performance modeling, specimen failure must occur within the length of the LVDT gauge. However, recent experiments using stiff mixtures have shown that failure often occurs outside the LVDT gauge length. This specimen geometry study was conducted to determine the specimen geometry that enhances the propensity of the failure inside the gauge length without sacrificing the advantage of the DTC testing that provides uniform stresses and strains in the middle of the specimen. Laboratory experiments were performed on cylindrical specimens of different geometries (i.e., different diameters and lengths). Test specimen diameters of 75 mm and 100 mm and specimen heights of 130 mm and 150 mm were used in this study. The specimen geometry effects on damage characteristic curves and failure criteria were identified through ANOVA tests and layered viscoelastic pavement analysis for critical distresses (LVECD) program. Based on analysis results and experimental verification tests, the specimen geometry recommended for the DTC testing is 100 mm in diameter and 130 mm in height with a 70-mm gauge length. The recommended specimen geometry is applicable when the gyratory-compacted specimen geometry is 150 mm in diameter and more than 178 mm in height.

Author Information

Lee, Jong-Sub
Federal Highway Administration at Turner-Fairbank Research Center, McLean, VA, US
Norouzi, Amirhossein
North Carolina State Univ., Raleigh, NC, US
Kim, Y.
North Carolina State Univ., Raleigh, NC, US
Pages: 11
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Stock #: JTE20140357
ISSN: 0090-3973
DOI: 10.1520/JTE20140357