Evaluation of Stripping Tests for Asphalt Mixtures to Replace AASHTO T283 Method in Missouri

Currently, many paving agencies in the U.S. including the Missouri Department of Transportation (MoDOT) use the AASHTO T¬-283 method (Tensile Strength Ratio (TSR) test) to determine the moisture damage susceptibility of asphalt mixtures. However, the TSR test has been shown to have a poor correlation with field results based on a review of literature and based on observations reported by MoDOT. In addition, the TSR test is time consuming and may be redundant in light of current requirements to conduct the Hamburg Wheel Tracking Test (HWTT) as part of balanced mix design. As a result, further research on these test methods was conducted. For this research five asphalt mixtures were investigated. The mixtures were subjected to the TSR test and HWTT. The Stripping Inflection Point (SIP) parameter was computed from HWTT using the Iowa method. The SIP parameter was found to be superior to the TSR test in correlating to field performance. Comparison of the RT-Index results with the SIP parameter suggested that the RT index is likely a weak indicator of moisture damage in asphalt mixtures. Based on the results obtained in this limited study, a framework was proposed to replace the TSR method. The framework is as follows; first, the mixtures are screened for rut depths lower than 4.0 mm at 20,000 passes in the Hamburg test. If the mixture exhibits low rut depths in the Hamburg test (less than or equal to 4 mm), it is highly likely that it is resistant to moisture damage and therefore judged as non-stripping. Second, if the rut depth is greater than 4.0 mm then the slope ratio is computed. If the slope ratio is found to be less than 2.0, then the mixture can be categorized as non-stripping. Finally, if the slope ratio is greater than or equal to 2.0, then the SIP is determined. A minimum threshold of 15,000 passes was chosen as the SIP threshold for initial implementation of the framework. Mixtures possessing SIP values less than 15,000 are scored as failing the stripping requirement.

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Report number: cmr 25-006
Published: May 2025

Project number: TR202306

Authors: William Buttlar, Punyaslok Rath, Jim Meister, and Katie Distelrath 

Performing organization: University of Missouri-Columbia/Missouri Center for Transportation Innovation