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Material characterization in support of implementation of the mechanistic-empirical pavement design guide

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Item Summary

Title: Material characterization in support of implementation of the mechanistic-empirical pavement design guide
Authors: Rayapeddi Kumar, Jayanth Kumar
Keywords: material characterization
Issue Date: Aug 2012
Publisher: [Honolulu] : [University of Hawaii at Manoa], [August 2012]
Abstract: Use of the Mechanistic-Empirical Pavement Design Guide (MEPDG) and its associated software requires a large number of inputs about traffic loading, environmental conditions, and material characteristics. Except for very important projects, for which many of the material characteristics may be determined directly from laboratory tests, practical implementation of the MEPDG for routine pavement design projects requires the development of a database containing properties for the most commonly used materials within the state.
In the analysis of flexible pavements in the MEPDG, the dynamic modulus (|E*|) and resilient modulus (Mr) are the primary input parameters used to characterize the elastic response of Hot Mix Asphalt (HMA) mixtures and base course (unbound granular) materials, respectively. In addition to the elastic properties of the materials used in the mechanistic analysis of the pavement structures, the MEPDG relies on deterioration model parameters to relate empirically the mechanistic pavement responses (strains) on different points of the pavement structure to distresses such as rutting (permanent deformation), cracking, and roughness.
This study focuses on measuring in the laboratory the resilient moduli of two types of base course materials and the elastic and permanent deformation characteristics of three types of HMA materials.
The continuous demand of aggregates for maintenance and rehabilitation (M&R) of existing pavements and to a lesser degree for construction of new ones as well as the increasing need to reduce the disposal of construction waste is putting pressure on agencies to find ways to increase the recycling of materials such as Recycled Asphalt Pavement (RAP) into the pavement structure. Experiences around the world indicate that Foamed Asphalt (FA) base course mixtures, which are a typically produced by stabilizing Reclaimed Asphalt Pavement (RAP) with foamed (expanded) asphalt, have shown improved performance relative to unbound base materials. Hence in this study, one of the base materials considered is a Foamed Asphalt (FA) base mixture. The other base material studied is a virgin aggregate base course material. The resilient moduli of both materials were studied at different density levels. The results of the study showed that the Mr of FA mixtures is in general between 2.5 and 5 times (corresponding to lowest and highest levels of bulk stress respectively) higher than the Mr of virgin aggregates (Type B) at 98% and 100% of maximum dry density, whereas at 102% of maximum dry density, the Mr of FA mixtures is in general between 2.8 and 1.8 times of maximum dry density (corresponding to lowest and highest levels of bulk stress respectively) higher than the Mr of virgin aggregates. Further, it was observed that the Mr of FA mixtures increased with increases in bulk stress, and the Mr decreased with increases in octahedral shear stress. On the other hand, the Mr of the virgin base course material increase mostly with the octahedral shear stress and to a much lesser degree also increased with the bulk stress.
For HMA, this study focuses on comparing the test results of dynamic modulus and permanent deformation tests performed in the laboratory on unmodified, polymer modified asphalt (PMA) mixes (modified with Elvaloy RET©) , and mixes reinforced with FORTA fibers. The laboratory experiments included testing two replicates of HMA specimens of each type at three target air voids. The results of the tests show that the mixes prepared using the PMA binder show relatively better resistance to rutting at high temperatures and low frequencies. For the mixes prepared using fibers, it was observed that the rate of failure in a permanent deformation test remains relatively constant irrespective of the of air voids of the specimen. The effect of the fibers is to hold the coated particles together under these unfavorable conditions, thus providing a level of safety for mixes compacted with high air voids.
Description: M.S. University of Hawaii at Manoa 2012.
Includes bibliographical references.
Appears in Collections:M.S. - Civil and Environmental Engineering

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