United States Department of Transportation
i
Rapid and simple method for binder oxidation aging
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1999-08-01
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[PDF-267.23 KB]
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TRIS Online Accession Number:00789921
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Edition:Final Report; July 1998 to August 1999
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NTL Classification:NTL-HIGHWAY/ROAD TRANSPORTATION-Materials;NTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and Performance;
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Abstract:The last 10 years have seen an ever-increasing use of microwave radiation (dielectric heating, in-situ heating) especially in organic synthetic research, the undergraduate laboratory, and industrial production. Scientific microwave instruments are now available to allow continuous monitoring of temperature and pressure. These controls are essential for laboratory aging of binders. Laboratory aging of asphalt is central to the performance graded (PG) system. A rapid and simple method for simulating binder aging using microwave radiation is presented. Using the eight Strategic Highway Research Program (SHRP) core asphalts, treating neat asphalt with microwave radiation for 7 hr and 20 min at 143 deg C and 440 psi (3034 kPa) yields a residue equivalent to that of Rolling Thin Film Oven Test plus Pressure Aging Vessel ("RTFOT + PAV"). To test ability of microwave energy (dielectric heating) to simulate "RTFOT + PAV" aging (conductive heating), six different tests were used to compare physical, chemical, and physicochemical changes resulting from the two modes of aging. The six tests are: intermediate-temperature stiffness, low-temperature stiffness, asphaltene content, high-performance size exclusion chromatography (HPSEC), asphalt relative total polarity, and infrared spectroscopy. Conductive heating (PAV, with or without RTFOT) under the conditions of microwave treatment (7 hr and 20 min at 143 deg C and 300 psi (2069 kPa) - for safety, 440 psi (3034 kPa) could not be used with PAV) yields a residue that shows clumping in the pan, and nonhomogeneity that prevented rheological testing. Therefore, conductive heating cannot replace dielectric heating for rapid aging. Alternatively, applying dielectric heating at the Superpave conditions of 20 hr at 100 deg C and 300 psi (2069 kPa), gives rheological changes equivalent to those produced by both the RTFOT plus the 20 hr of PAC at similar conditions. Thus, dielectric heating enhances oxidation even at 100 deg C. The enhancement is more pronounced at higher temperatures (143 deg C) with a 70% saving of time. 3 Figures, 14 tables, references, 38p.
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