Modelling the linear viscoelastic rheological properties of bituminous binders

Field aging effect on chemistry and rheology of asphalt binders and rheological predictions for field aging

Defining failure and developing a unified failure criterion for the fatigue testing of asphalt materials remain a challenge. This study seeks to develop a failure criterion for the fatigue testing of asphalt binders under cyclic loading in the dynamic shear rheometer. Newly developed pseudo-strain energy (PSE)-based failure analysis is introduced for both the time sweep fatigue test and the accelerated linear amplitude sweep (LAS) test (AASHTO TP101). The presented methodology builds upon recent advances in the simplified viscoelastic continuum damage (S-VECD) modelling of asphalt mixtures. Trends in stored PSE have been proven to be effective in defining failure for the LAS tests of asphalt binders. This new proposed failure definition is material-dependent and, thus, is effective in capturing the benefits of asphalt modification for binder fatigue resistance. In addition, it is found that a unique relationship that is independent of loading history exists between the PSE release rate and fatigue life. T...

Unified failure criterion for asphalt binder under cyclic fatigue loading

Morphology, thermal analysis and rheology of Sasobit modified warm mix asphalt binders

Mechanical measurements on asphalt binders to determine the performance grade of the low-temperature specification are typically carried out with a bending beam rheometer (BBR). The BBR test requires considerable material to fabricate a specimen (approximately 15 g per beam). The relatively large amount of asphalt binder required for the BBR limits its applications. The BBR is difficult to apply to extracted asphalt binder or to other situations in which there is a limited amount of binder, for example, residue from emulsions. This paper proposes an alternate mechanical test to the BBR to determine low-temperature PG. Only approximately 25 mg of asphalt binder are required to perform a test. The test employs 4-mm-diameter parallel plates on a dynamic shear rheometer (DSR) and includes a correction for machine compliance. This correction allows testing to -40°C. A low-temperature specification from the 4-mm rheometry is suggested by the establishment of a correlation between BBR creep stiffness data and DS...

New Low-Temperature Performance-Grading Method: Using 4-mm Parallel Plates on a Dynamic Shear Rheometer

A new technique, which uses 4-mm parallel plates on a dynamic shear rheometer (DSR) with machine compliance corrections, was developed to measure low-temperature properties of asphalts. Good results have been achieved at test temperatures as low as -40°C. The test method requires only about 25 mg of material instead of 15 g for the bending beam rheometer (BBR). Also, no specimen premolding is needed, and a relatively low temperature (60°C to 70°C) is required to load the samples into the measuring system. The key to the new technique is correction for errors due to machine compliance. Two types of machine compliance correction were applied to the dynamic frequency sweep data in this work. The following areas were investigated: effects of machine compliance on the measured low-temperature properties, reproducibility of data, consistency among data collected on different sizes of plates after machine compliance corrections, and comparison between the corrected data from DSR and converted BBR data. Results s...

New Technique for Measuring Low-Temperature Properties of Asphalt Binders with Small Amounts of Material

This report describes progress towards development of a new thin film (300 μm) short- and long-term aging test suggested as an alternative to the standard rolling thin film oven (RTFO) and pressure aging vessel (PAV) tests. The new test, referred to as the Simple Aging Test (SAT), can be applied to neat and modified bitumens, and emulsion residues. Before the Strategic Highway Research Program, there was considerable interest in static thin film aging. However, the RTFO test was adopted for short term aging because of the large amount of aged asphalt needed for the Bending Beam Rheometer (BBR) test. Since the adoption of the RTFO, it has been found problematic for aging highly modified binders. In the case of warm mix binders, RTFO testing at lower temperature to simulate a “warm” plant may limit rolling needed to uniformly age the material. Recent development of a 4-mm dia. parallel-plate dynamic shear rheometer (DSR) technique allows DSR tests to -40°C, requires only 25 mg of binder, and can estimate BBR m-value and creep stiffness. By combining this new DSR technique with the SAT, the low and intermediate temperature rheology of short and long-term aged bitumens can be determined. Also, there is sufficient aged material to perform high temperature DSR using 25 mm plates. The SAT eliminates the “rolling” issue for polymer modified and warm mix asphalts. The SAT time and temperature equivalent to reach the same aging as the standard RTFO and PAV are reported for several bitumens.

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Thin film oxidative aging and low temperature performance grading using small plate dynamic shear rheometry: an alternative to standard rtfo, pav, and bbr

Changping Sui

Papers

New Low-Temperature Performance-Grading Method: Using 4-mm Parallel Plates on a Dynamic Shear Rheometer

New Technique for Measuring Low-Temperature Properties of Asphalt Binders with Small Amounts of Material

Thin film oxidative aging and low temperature performance grading using small plate dynamic shear rheometry: an alternative to standard rtfo, pav, and bbr