Title page for ETD etd-08292006-121153


Type of Document Dissertation
Author Druta, Cristian
URN etd-08292006-121153
Title A Micromechanical Approach for Predicting the Complex Shear Modulus and Accumulated Shear Strain of Asphalt Mixtures from Binder and Mastics
Degree Doctor of Philosophy (Ph.D.)
Department Engineering Science (Interdepartmental Program)
Advisory Committee
Advisor Name Title
George Z. Voyiadjis Committee Co-Chair
Linbing Wang Committee Co-Chair
Su-Seng Pang Committee Member
Suresh Moorthy Committee Member
Darrell Hanry Dean's Representative
Keywords
  • gyratory compactor
  • superpave
  • performance grading
Date of Defense 2006-06-23
Availability unrestricted
Abstract
Asphalt mixtures are particulate composite materials consisting of uniformly distributed mineral aggregates, asphalt binder and air voids. Mixtures of asphalt binder and filler, also called mastics, are often assumed to behave as simple viscoelastic materials, where the binders are stiffened by the filler. Because the workability and performance of bituminous mixes are known to be affected by the filler-asphalt mixture (or mastic) properties, this study is intended for performing rheological tests on asphalt binder and mastics and use the results in order to estimate performance parameters of asphalt mixture.

The present work uses the PG64-22 asphalt binder test data initially to predict mastics' performance parameters - shear modulus (G*) and accumulated permanent shear strain (γacc) and then same properties for asphalt mixtures, in order to find a correlation between the three materials. Mastics were obtained by mixing the PG64-22 asphalt with three types of filler - donna fill, limestone, and granite - in five different percentages by volume - 5, 10, 15, 20, and 30%. The asphalt mixtures contained granite aggregate, 6% air voids content and five asphalt contents - 3% through 7%. Binder and mastics were tested at three temperatures (46, 55, and 64C) using a dynamic shear rheometer (DSR), while the mixtures were tested at two temperatures (55 and 64C) using the Superpave shear tester.

Newly developed Hirsch model was used for estimating the shear moduli of asphalt mastics and mixtures, while for estimating the accumulated permanent shear strain a semi-empirical equation developed by Shenoy was used. Both estimations have been performed by using the shear modulus of the binder obtained from the DSR. The binder, mastics, and mixtures rheological data were generated using the appropriate equipment for each material, under identical conditions of measurement, thus making it possible to identify a correlation between the materials. There was a good agreement between the measured and estimated values using the two methods (Hirsch and Shenoy), with Pearson correlation parameters (R2) being over 0.90 or better.

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