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Classification of asphalt binder has evolved since the invention of asphalt pavement in 1870. Starting with penetration grading, moving forward to viscosity grading, and now the current system of performance grading (PG). All states in the US now adhere to some form of the PG system. During the last decade, several new modifiers and extenders have been introduced to modify the grade of a straight-run binder to achieve a target PG. In some cases, it has been observed that although a binder may meet the current PG specification, it may result in significantly sub-par performance. This suggests that the current PG specification does not accurately capture the performance characteristics of a binder. The main objective of this study was to use alternative chemical and mechanical tests on a large set of binders to identify differences in binders with a similar PG. This study examined the performance of 34 asphalt binders from 12 different binder sources using standard PG tests following AASHTO M320, as well as tests beyond the PG specification. The tests outside of the PG framework included chemical tests (X-ray fluorescence and spot), as well as other mechanical tests (Multiple Stress and Creep Recovery to measure permanent deformation potential at multiple high temperatures, BBR Pro to measure tensile strength at low temperatures, and poker chip test to measure tensile strength at intermediate temperature). For tests outside the PG specification, outlier criteria were developed based on the results found. Outliers were defined differently for each test and do not represent positive or negative outcomes in terms of expected performance. The tests outside of the PG specification (spot, [Delta] T [subscript c], aging sensitivity, poker chip, and low temperature strength) all produced many outliers, some even extreme outliers for binders with a similar PG. This study highlights the need for additional testing beyond the PG specification to improve binder grading. More performance testing on mixtures is needed to establish if outlier behavior is beneficial or detrimental.
A dozen papers from a December 1993 symposium in Dallas/Fort Worth, Texas. Among the topics are why the new proposed rheological properties of asphalt binders are required and how they compare to conventional properties, the development and use of the SHRP direct tension specification test, oxidatio
Now updated, this volume serves as a single resource to supplement Superpave PG asphalt binder system test methods. This new edition contains a chapter on the direct tension test (DTT), an introduction to the new multi-stress creep-recovery test (MSCR), a troubleshooting section and updated graphics.
This volume gathers the latest advances, innovations, and applications in the field of pavement technology, presented at the 12th International Conference in Road and Airfield Pavement Technology (ICPT), hosted by the University of Moratuwa, Sri Lanka, and held on July 14-16, 2021. It covers topics such as pavement design, evaluation and construction, pavement materials characterization, sustainability in pavement engineering, pavement maintenance and rehabilitation techniques, pavement management systems and financing, transportation safety, law and enforcement related to pavement engineering, pavement drainage and erosion control, GIS applications, quarry material assessment, pavement instrumentation, IT and AI applications in pavement. Featuring peer-reviewed contributions by leading international researchers and engineers, the book is a timely and highly relevant resource for materials scientists and engineers interested in pavement engineering.
This report addresses a shortcoming of the Multiple Stress Creep Recovery (MSCR) test method and specification system for virgin PG 58-XX and blends of PG 58-XX with reclaimed asphalt pavement (RAP) binders. The MSCR specification system limits the non-recoverable compliance, Jnr, to less than 4.5 kPa-1 for standard S-graded binders and disregards binders that do not satisfy this criterion. Also, the MSCR specification does not consider virgin binder grade adjustments when RAP is used. These binders, which are often blended with high percentages of RAP, have positively resulted in mostly a 64 °C high-temperature grade according to LTPPBind, with 98% reliability against rutting in Kansas. This research blended PG 58-28 and PG 58-34 virgin binders with four RAP binders and conducted MSCR tests to investigate this issue. Results showed that the high-temperature grade of PG 58-XX binders increased to 64 °C when they were mixed with RAP binder percentages of 15% or more. Furthermore, MSCR test results showed that the addition of RAP binder decreased the Jnr value to the S criteria when the requirement of Jnr difference percentage was omitted. Results also showed that the RAP binder can be screened using the rotational viscosity test to ensure the blends of PG 58-XX and RAP binders result in high-temperature grade adjustments and satisfy the S grade. A comprehensive set of PG 58-XX, PG 64S-XX, and multiple RAP binders used in Kansas should be tested to develop sound specification criteria based on PG and MSCR grading specifications.