首页|Assessment of Aging at FHWA's Pavement Testing Facility
Assessment of Aging at FHWA's Pavement Testing Facility
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Field cores were taken in 1995 and 2002 from eight asphalt pavements constructed in 1993 at FHWA's pavement testing facility to evaluate in situ pavement aging. Dynamic mechanical properties of these cores were evaluated by using the Superpave~® shear tester. The moduli of aged pavements were also predicted from binder, aggregate, and mixture properties with available prediction models, and the aging severity levels of all pavements were compared between the lab-measured and model-predicted. Eight pavements with two polymer-modified and six unmodified binders were evaluated in this study. Polymer-modified asphalt pavements showed comparatively lower aging than unmodified asphalt pavements. For unmodified asphalt pavements, stiffer asphalts tended to have higher aging indices. The binder aging index was found to be inversely proportional to the loading frequency, and differences between the aging indices for different binders were higher at lower frequency. Comparison of lab-measured and model-predicted binder aging indices showed similar rankings for all binders. Low stiffness binders, for example, AC-5, showed higher aging indices than high stiffness binders, for example, Styrelf. Pavement depth significantly affected binder aging. The aging index near the surface (6.35 mm) was found to be about four to five times the aging index at a depth of 139.7 mm in pavement. Comparison of lab-measured and model-predicted mixture aging indices showed large variations, from overpredicted to quite underpredicted, depending on the binder type and nominal maximum aggregate size.
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