Development of Asphalt Concrete Mixture Long Term Aging Protocol for Extreme Climatic Condition

Abstract: An accelerated laboratory mixture long-term aging protocol is developed for extreme climatic conditions. The protocol aims to simulate eight years of field aging at the pavement surface using the NCHRP 09-54 recommended Climatic Aging Index (CAI) model. A 17-day loose mixture aging at 95°C is initially determined, but an accelerated oven aging temperature of 135°C is selected for practicality, resulting in a 30-hour aging period. The protocol's applicability is investigated using rheological, chemical, and mixture level fracture experiments. Results demonstrate consistency between the proposed LTA protocol and the NCHRP-recommended protocol. The study also addresses the challenge of asphalt pavement aging in Arizona's diverse and extreme climatic conditions, which accelerate the aging process. Loose mixes underwent aging at 135°C for varying durations, and mechanical tests were performed on aged specimens to evaluate and select an optimal aging protocol. The selected protocol maintains specimen integrity for performance testing and prediction while considering efficiency, practicality, and versatility. The developed accelerated long-term aging is further reduced to 8 hours at 135℃ and 15 hours at 135℃ for intermediate and low temperature cracking testing, respectively. Aging protocols are further verified and validated by the plant mix and control field test section. The consistency of the results between the two aging temperatures at the mixture level verifies the feasibility of using 135℃ as part of an LTA protocol in the balanced mix design applications.