Simulation of Long-Term Aging of Asphalt Binders for Indian Conditions Using Draft Oven and Pressure Aging Vessel

Abstract

Artificial aging of asphalt binder in the laboratory is critical for studies on reclaimed asphalt pavement materials (RAPM). This study aims to explore the effectiveness of the universal simple aging test (USAT) and pressure aging vessel (PAV) in simulating the long-term aging (7 years) of asphalt binders for Indian conditions. Rheological and chemical characteristics of lab-aged binders were compared with the field-recovered asphalt binders. It was found that there is a need to extend the aging period in the standard test procedures to simulate field long term aging. Aging in PAV at 110°C for 40 h/60 h was found to be appropriate. The extended conditioning period is a function of the type of base binder and the extent of aging required to be simulated. Aging in draft oven (USAT) was found to be inadequate to represent the changes in chemical properties due to aging, as evaluated using the carbonyl and sulfoxide aging indices. The rate of aging in the polymer modified binder was found to be higher than the viscosity graded binder, used in this study. To simulate field long term aging in tropical environment, this study recommends using PAV at 110°C for an extended time period ranging from 20 h to 40 h. The ratio of the stiffness of field-extracted binder and the unaged binder is the key to select the appropriate aging time.