Abstract
This research characterizes the performance of various plant-produced asphalt concrete mixtures by dynamic modulus|E∗|test using asphalt mixture performance tester (AMPT). Marshall designed specimens of seven different mixtures were prepared using the Superpave gyratory compactor and subjected to sinusoidal compressive loading at various temperatures (4.4 to 54.4°C) and loading frequencies (0.1 to 25 Hz). A catalog of default dynamic modulus values for typical asphalt concrete mixtures of Pakistan was established by developing stress-dependent master curves separately, for wearing and base course mixtures. The sensitivity of temperature and loading frequency on determination of dynamic modulus value was observed by typical isothermal and isochronal curves, respectively. Also, the effects of various variables on dynamic modulus were investigated using statistical technique of two-level factorial design of experiment. Furthermore, two dynamic modulus prediction models, namely, Witczak and Hirsch, were evaluated for their regional applicability. Results indicated that both the Witczak and Hirsch models mostly underpredict the value of dynamic modulus for the selected conditions/mixtures. The findings of this study are envisaged to facilitate the implementation of relatively new performance based mechanistic-empirical structural design and analysis approach.
Highlights
Hot-mix asphalt (HMA) consists of the optimum combination of two basic ingredients: aggregate and asphalt binder
Statistical analysis of the results revealed that use of different job mix formulae (JMF) mixes affected the dynamic modulus
For all the tested asphalt concrete mixtures, the dynamic modulus values decreased with an increase in temperature and decrease in the loading frequency
Summary
Hot-mix asphalt (HMA) consists of the optimum combination of two basic ingredients: aggregate and asphalt binder. In order to meet the diverse and often conflicting performance parameters, for example, resistance to fatigue, deformation, cracking, and moisture damage; durability; skid resistance; and workability and economy, the mix designer generally manipulates three variables, namely, aggregates, asphalt binder, and the ratio of asphalt binder to aggregates, and seeks to achieve the aforementioned performance requirements. The phenomenon of premature failure of pavement structures is attributed to the current design procedures based on 1993 AASHTO design guide which are inherently empirical and incapable of providing adequate and reliable designs for heavy axle loads and tyre pressures in diversity of climatic regions and necessitates a more comprehensive design approach which incorporates both mechanistic and empirical aspects of design. The success of the mechanisticempirical structural design approach or framework lies in the accurate material characterization for predicting realistic pavement responses and ultimate performance. The viscoelastic nature of HMA is a challenge to be considered for its accurate characterization by the material properties. Dynamic modulus |E∗| of HMA is one such material property
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