Volume 38, Issue 1 (January 2010)
A Comparison of Warm Asphalt Binder Aging with Laboratory Aging Procedures
Warm asphalt has been gaining increasing popularity in recent years; however there are several characteristics about warm asphalt that are still unknown. While several studies have been conducted to study the performance of warm asphalt mixtures, aging characteristics of warm mix asphalt (WMA) binders are not known in great detail. This paper presents the results of a limited study to evaluate the aging characteristics of two WMA binders artificially aged in the rolling thin film oven (RTFO) and the pressure aging vessel and comparing them with binder extracted from freshly prepared and artificially aged warm asphalt mixtures. RTFO aging was performed at 163°C and a lower temperature to simulate warm asphalt aging. Tests on binders aged in the laboratory and binders extracted from freshly mixed and aged mixtures indicated that the WMA binders extracted from WMA mixtures had significantly lower viscosities and G∗/sin δ compared to binders extracted from hot mix asphalt (HMA) and binders aged in the RTFO at 163°C (325°F). This indicates that the lower mixing and compaction temperatures reduce the aging of the warm asphalt binders. Also, binders extracted from WMA had significantly lower creep stiffness values and significantly higher m-values compared to warm asphalt binders aged in the RTFO at 163°C (325°F) and binders extracted from HMA. Binders containing WMA additives did not have higher G∗ sin δ values, indicating that the warm asphalt additives do not negatively affect the fatigue properties of the binders. Gel permeation chromatography analysis indicated that the addition of the warm asphalt additives did not have any significant effect on the %LMS of the binders used in this study.