Workshop: Dynamic Modulus E* Characterization of HMA Mixes for Implementation of PMED
Dr. Rafi Tarefder
Professor
University of New Mexico
Department of Civil Engineering
Wednesday, October 9th
1:00 P.M. - 3:30 P.M. (CT)
On October 9, 2024, Dr. Rafi Tarefder, P.E. delivered a two-and-a-half-hour Webinar on “Dynamic Modulus E* Characterization of HMA Mixes for Implementation of PMED Software”. Dr. Tarefder is a Professor of Civil Engineering at the University of New Mexico (UNM) and has 25 years of expertise in pavement materials characterization and modeling. He has led the development of input models and local calibration of pavement mechanistic empirical pavement design (PMED) guide for implementation in New Mexico. The event was sponsored by the Southern Plains Transportation Center. Forty-six participants attended, representing private, public, and government institutions.
During the first hour of the presentation, Dr. Tarefder defined the dynamic modulus of asphalt concrete based on the speed of the roadway vehicles and the viscoelastic behavior of asphalt concrete, and how it is employed in a multiple linear-elastic or viscoelastic analysis. In the second hour, Dr. Tarefder explained three different levels of E* for PMED analysis. He has also shown an Excel Spreadsheet example analysis of how PMED software generates an E* master curve based on the inputs given at each level. Details of frequency-temperature superposition, master curve development, and sigmoidal function fit were covered. During the last half an hour, he has shown how he has developed a level two E* equation for use in New Mexico, and how it improves and differs from the PMED’s default equation. His talk has also briefly covered some challenges of E* sample preparation in the laboratory and asphalt binders’ dynamic shear modulus (G*).
ABSTRACT
The recently developed Pavement Mechanistic Empirical Design (PMED) software uses the dynamic modulus (E*) of asphalt concrete (AC) as a major input that directly affects the rutting and fatigue model in the PMED software. This talk will cover how to generate this input from the field collected Superpave mixes and use it in the PMED design software efficiently. In essence, this talk will cover mix compaction using a gyratory compactor, cylindrical samples preparation using lab saw and coring, cylinder testing for E* at different temperatures and loading frequencies, and development of E* predictive model/equation to conduct level 2 PMED analysis. In addition, this workshop will cover how this model uses aggregate gradation data as well as asphalt binders’ dynamic shear modulus (G*) obtained in the laboratory. This workshop will also cover how a sigmoidal function is fitted to the laboratory E* data to develop master-curves using regression methods, and how the model fitting parameters are determined, and how the parameters are directly supplied as inputs of PMED software.
BIO
Dr. Rafi Tarefder is a Professor of Civil Engineering and Regents’ Lecturer at the University of New Mexico (UNM). He serves as an Associate Director of Southern Plain Transportation Center (SPTC), and Director of New Mexico Transportation Center. Dr. Tarefder’s research work covers a wide spectrum, from applied and design-focused to theoretical, principally in pavement materials and design. He has published 427 (187J, 240C) peer-reviewed journals and refereed conference articles including two best paper awards. He has authored 1 textbook and 6 book chapters; edited 6 books and journal special issues, published 45 major research reports, and filed 2 patents. Dr. Tarefder is the Chair of the Annual Paving and Transportation conference, which is the biggest in the southwest, having an attendance of more than 700 participants. He is an associate editor of ASCE’s International Journal of Geomechanics. He is a licensed professional engineer in NM and Idaho.
