Climate-, Depth-, and Time-Based Laboratory Aging Procedure for Asphalt Mixtures

Abstract

Aging causes asphalt pavement materials to stiffen and embrittle, which leads to a high cracking potential. A practical and accurate laboratory conditioning procedure that can simulate long-term aging of asphalt concrete for performance testing and prediction is required in order to integrate the effects of aging in pavement performance prediction models and other mechanistic design and analysis methods. Recent studies have suggested that loose mix oven aging at 95°C is the most promising long-term aging method to simulate field aging. This study has developed a means to determine laboratory aging durations for asphalt mixtures that best reflect the time, climate, and pavement depth for a given pavement location in the United States. A rigorous kinetics model together with laboratory experimental results demonstrate that the laboratory aging duration that is needed to match a given field condition is independent of material-specific kinetics. Project-specific laboratory aging durations that match field aging at various pavement depths were determined for a broad set of materials. The project-specific aging durations were used to calibrate a kinetics-derived climatic aging index (CAI) that was then used to determine the laboratory aging duration to match field aging at any location of interest. The CAI-determined aging durations at 95°C were used to generate aging duration maps for the United States for three field ages (four years, eight years, and 16 years) to match field aging at three depths (6 mm, 20 mm, and 50 mm).