Volume 37, Issue 4 (July 2009)
Effects of Various Long-Term Aging Procedures on the Rheological Properties of Laboratory Prepared Rubberized Asphalt Binders
Rubberized asphalt has been used to improve the mechanical characteristics (e.g., rutting resistance, fatigue life, friction, and skid resistance) of hot mix asphalt mixtures. The objective of this research was to investigate the rheological characteristics of the rubberized asphalt binders after various long-term aging procedures, using the penetration index, the dynamic shear rheometer, the bending beam rheometer, and high pressure-gel permeation chromatographic testing. The experimental design included the use of three binder sources, three binder grades (PG 64-22, PG 64-22+10 %-40 ambient rubber, and PG 76-22) and three aging states, i.e., virgin, rolling thin film oven, and pressurized aged vessel [four test temperatures (65, 80, 100, and 110°C) and five aging durations (15, 20, 40, 80, and 144 h) under the pressure of 2070 kPa]. The test results show that, as expected, the use of crumb rubber can effectively improve the PG grade and aging resistance of the virgin asphalt binder. A series of rheological properties (e.g., penetration, stiffness, m-value, and percentages of large and small molecular sizes) illustrate that the PG 64-22 binder, mixed with 10 %-40 ambient rubber, yields similar or improved rheological properties in comparison with PG 76-22 using 3 % styrene-butadiene-styrene polymer after various long-term aging procedures.