Study of Asphalt Binder Fatigue with a New Dynamic Shear Rheometer Geometry

With the effort to precisely predict the lifetime of asphalt binders and subsequently optimize their utilization in a more economical way, the objective of this study was to introduce a new methodology to improve the fatigue characterization of asphalt binders through a new dynamic shear rheometer (DSR) sample testing geometry. Initially, numerical analyses were performed to study the geometry-related issues of a standard DSR sample on time sweep tests, and to assist in the effort to increase understanding of the DSR damage phenomena of asphalt samples. On the basis of these numerical analyses, a new testing geometry, the parallel hollow plate, was developed and its test results compared with the standard sample testing geometry. A single type of asphalt binder was assessed using amplitude sweep tests. The obtained results demonstrated a significant difference between the fatigue of the two sets of DSR sample geometries. On the basis of these, time sweep tests were conducted for the same sample geometries and the results demonstrated that the new testing geometry yields material response consistency under different loading conditions. The lifetime prediction of the standard parallel plates showed a significant difference with the newly developed DSR sample testing geometry by overestimating the total number of cycles until asphalt binder failure. The new testing geometry allowed the isolation of the damaged area of asphalt binder by localizing the shear stresses in the samples’ periphery.

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Considerations for using the 4 mm Plate Geometry in the Dynamic Shear Rheometer for Low Temperature Evaluation of Asphalt Binders

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198119855332 ◽

2019 ◽

Vol 2673 (11) ◽

pp. 649-659 ◽

Cited By ~ 4

Author(s):

Ramez Hajj ◽

Angelo Filonzi ◽

Syeda Rahman ◽

Amit Bhasin

Keyword(s):

Low Temperature ◽

Asphalt Binder ◽

Asphalt Binders ◽

Asphalt Pavements ◽

Dynamic Shear ◽

Dynamic Shear Rheometer ◽

Reclaimed Asphalt ◽

Load Response ◽

Linear Viscoelastic ◽

Analytical Approaches

The low-temperature properties of asphalt binder have attracted attention in recent years thanks to an increase in the use of reclaimed asphalt pavements (RAP). Traditional methods to evaluate the low-temperature properties of the binder require a large amount of binder that needs to be recovered from RAP samples for testing with a Bending Beam Rheometer (BBR). To economize on sample size for RAP materials and also for emulsion residues, previous researchers have explored the potential of using a 4 mm diameter specimen with a Dynamic Shear Rheometer (DSR) in lieu of the BBR. To compare results from frequency sweep tests conducted using the DSR with results from the BBR, data from the former need to be converted to time domain and subsequently from a shear load response to an axial load response. Previous research studies have developed methods to accomplish these two conversions to compare data from the DSR with data from the BBR. The objective of this study is to examine some of these methods from the literature and elsewhere based on the principles of linear viscoelastic interconversion using a set of 11 different binders. Results using different analytical approaches from this study show that the DSR has good repeatability and verify that it can be used as a surrogate for the BBR to determine low-temperature properties, while exercising some caution with some of the assumptions related to Poisson’s ratio.

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Evaluation of Stiffness, Strength, and Ductility of Asphalt Binders at an Intermediate Temperature

Transportation Research Record Journal of the Transportation Research Board ◽

10.3141/2632-05 ◽

2017 ◽

Vol 2632 (1) ◽

pp. 44-51 ◽

Cited By ~ 2

Author(s):

Ramez Hajj ◽

Rachel Hure ◽

Amit Bhasin

Keyword(s):

Asphalt Binder ◽

Fatigue Cracking ◽

Intermediate Temperature ◽

Asphalt Binders ◽

Dynamic Shear ◽

Dynamic Shear Rheometer ◽

Additional Information ◽

Poker Chip ◽

Strength And Stiffness ◽

Strength And Ductility

The search for a test and parameter that can effectively describe the fatigue cracking resistance of an asphalt binder has led to many approaches. Of these, researchers have used stiffness, strength, and ductility-based criteria to screen binders on the basis of inherent resistance to cracking. In this study, poker chip testing on thin films of asphalt binder was used at intermediate temperatures to obtain both stress and ductility-based properties of eight binders. In addition, a dynamic shear rheometer frequency sweep at an intermediate temperature was conducted to obtain stiffnesses of the binders and a surrogate parameter for ductility. The results showed no relationship between strength and stiffness. In most cases, binders that were rated to have high ductility on the basis of the dynamic shear rheometer parameter also had high toughness on the basis of the poker chip test. However, some binders clearly departed from this trend, with at least one binder exhibiting both ideally desired high stiffness and toughness. Examination of failure surfaces from the poker chip test provided additional information about the mechanisms that drove failure.

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