Laboratory evaluation of long-term aging effect on linear viscoelastic and fatigue properties of FAM mixtures

Abstract

Aging is considered as one of the major factor which causes an increase in stiffness and brittleness to asphaltic mixture. This study aimed at evaluating the effect of different aging protocol on viscoelastic and fatigue properties of Fine Aggregate Matrix (FAM) which represents the finer portion (passing 2.36 mm sieve size) of asphalt concrete mixtures. To evaluate the effect of aging on viscoelastic and fatigue properties of FAM mixtures, six different long-term aging levels (6 h at 135 °C, 12 h at 135 °C, 24 h at 135 °C, 5 days at 95 °C, and 12 days at 95 °C aging on FAM loose mixture and 5 days at 85 °C on compacted FAM specimens) were considered. Linear Visco-Elastic (LVE) limit of each FAM mixtures was initially determined by conducting strain sweep test. Viscoelastic properties (|G*| and δ) and master curve shape parameters of FAM mixtures were further determined from temperature and frequency sweep test. Fatigue properties of FAM mixtures at different aging levels were evaluated using strain controlled time sweep test. Irrespective of the aging level applied to the FAM specimen, the LVE limit was found almost constant for all FAM mixtures. Viscoelastic properties (|G*| and δ) for FAM specimen aged for 24 h at 135 °C, and 12 days at 95 °C aged FAM mixtures showed similar results from the master curve plots. The fatigue properties of FAM mixtures decreased as the aging level changed from 5 days at 95 °C to higher level aging of 12 days at 95 °C. Despite of the similar viscoelastic properties, the trend observed between FAM mixtures aged 12 days at 95 °C and 24 h at 135 °C were not found to have similar fatigue properties. Findings of this study on FAM phase can be successfully used to characterize the effect of long-term aging on performance studies of FAM mixtures.