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CHAPTER 6
Evaluating the Performance
of Asphalt Concrete Mixtures
This chapter presents an introduction to evaluating the performance of HMA mixtures in
pavement systems. It provides mixture designers with a concise compilation of information
relating HMA properties to the failure mechanisms discussed in Chapter 2:
· Rutting and permanent deformation
· Fatigue cracking
· Low-temperature cracking
· Moisture damage
· Durability
HMA performance is strongly influenced by the composition of the mixture and the in-place
density. The effect of binder properties, aggregate properties, and mixture volumetric properties
on performance, which serves as the basis for the mixture design criteria in Chapters 8 and 10,
are discussed. The important role of field compaction in the performance of dense-graded and
SMA mixtures cannot be over emphasized. Marginally designed mixtures may perform adequately
when properly compacted, but even the best designed mixture will not perform adequately when
poorly compacted.
In recent years there has been a growing interest in using performance testing and performance
prediction models in HMA mixture design and acceptance. For higher traffic level designs,
the three-level Superpave mixture design and analysis system developed during the Strategic
Highway Research Program included a series of performance tests and models to evaluate the
expected performance of an HMA mixture. Unfortunately due to complexity, high equipment
costs, and the lack of field calibration for the models, the mixture analysis portion of this system
was not fully implemented. Over the last 15 years, additional progress in performance testing
has been made, and recently the Mechanistic-Empirical Pavement Design Guide (MEPDG)
has been completed and made available to the profession. The MEPDG includes field-calibrated
performance prediction models for rutting and cracking that can be used to predict the perfor-
mance of an HMA mixture in a particular pavement section.
Although performance is directly addressed by the mixture design processes presented in this
manual through the material selection and volumetric criteria used in design, some agencies and
mixture designers may desire confirmation through performance testing and modeling. This
chapter also discusses various performance tests that can be used to assess HMA mixture per-
formance and presents an introduction to the MEPDG and how this software can be used to
complement the mixture design process.
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