Development of a Laboratory Operations-Friendly Long-Term Loose Mix Aging Protocol for New Asphalt Pavements

Abstract

New asphalt pavements are often designed to last 15 to 20 years without a major rehabilitation. However, an asphalt mix gets stiffer and more brittle with pavement service life because of aging. As cracking resistance decreases at higher aging levels, pavement structural design and performance verification need to consider the long-term aging characteristics of asphalt mixes. The research presented in this paper developed long-term loose mix aging protocols that are more friendly to routine laboratory operations. Based on a theoretical aging model and the IDEAL cracking test, two aging protocols are equivalent to the 3- and 6-day loose mix aging durations at 95°C provided by NCHRP 9-54, which are 20 h at 110°C and 20 h at 120°C, respectively. These new long-term aging protocols were then confirmed by the Texas Overlay Test and the Illinois Flexibility Index Test. The integration of these protocols into a comprehensive framework for mix design, pavement performance verification, and production testing is discussed. In brief, these new long-term aging protocols would be employed for evaluating cracking resistance only in the pavement performance verification stage, whereas the short-term aging protocol, namely, 2 h at the compaction temperature, would be applied to Superpave volumetric evaluation, balanced mix design (BMD), and production testing. These two new aging protocols combined with BMD rapid performance tests and performance prediction tests make this comprehensive framework very practical and efficient.