Representative Long-Term Aging Duration for Asphalt Mixtures from Gate-to-Grave

Abstract

Asphalt mixtures start to age from the moment they are produced, placed, and compacted. This aging process, which continues throughout their service life under ambient conditions, is commonly referred to as long-term aging. This long-term aging significantly affects asphalt mixture performance. While various laboratory methods have been developed to simulate long-term aging for use in balanced mix design (BMD), these existing methods have limitations. Primarily, they focus on representing an asphalt mixture’s aging condition at a specific point in time (e.g., after 8 years of service) and do not account for the cumulative impact of aging over the entire pavement lifespan. There is a need for a simple aging method that considers the aging process from production to the end of the pavement’s life (or “from gate-to-grave”), rather than just a single point in time. This paper presents a representative long-term aging method to address such a need. Firstly, this paper discusses the representative long-term aging duration concept, followed by the laboratory evaluation of such a concept with five asphalt mixtures using the indirect tensile asphalt (IDEAL) cracking test and dynamic modulus test. The representative long-term aging durations are significantly shorter than those based on aging after a specific point in time (or years of service) with respect to either the cracking tolerance index (CT_Index) from the IDEAL cracking test or the dynamic modulus of each mixture. This finding is further validated using 16 CT_Index datasets and 11 dynamic modulus datasets at multiple aging conditions. This paper also discusses how to practically implement the representative long-term aging duration in a BMD framework.