(Received 30 October 2000; accepted 30 March 2001)
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The present work provides a standardized method by which various mixtures can be compared and their expected performance can be assessed in a uniform manner using the Superpave shear tester. Based on the present findings, it is evident that complete mixture evaluation can be done through the frequency sweep at constant height (FSCH) data from the Superpave shear tester (SST), without the need to generate the repeated shear at constant height (RSCH) data. This would reduce the experimental time without compromising the information obtained.
FSCH and RSCH data at different temperatures are generated on the SST for a number of aggregate-asphalt mixture combinations. The shear moduli versus frequency data from the FSCH at different temperatures are unified to form a single curve for each mixture so that a specification parameter Ts (°C) can be determined.
Each unified curve is fitted with a constitutive equation from which model parameters are evaluated. The slope B1 in the low frequency region of the unified curve, when normalized with the term (T/Ts), results in a parameter that relates to the permanent strain after 5000 cycles in RSCH at any temperature T. There is a good possibility that the slope B2 in the high frequency region of the unified curve may relate to distresses in the intermediate temperature range, such as fatigue. If this is proven true through future research, then the Superpave shear tester could earn the distinction of being a “simple performance tester.”
Senior research fellow, FHWA-TFHRC-HRDI-11, McLean, VA
Assistant professor, University of Utah, Salt Lake City, UT
Stock #: JTE12277J