Laboratory fatigue characterization of asphalt mixtures using the flexural bending beam fatigue test
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In this study, the traditional third-point loading and strain-controlled flexural bending beam (BB) fatigue test was utilized to comparatively characterize the fatigue resistance of two hot-mix asphalt concrete (HMAC) mixtures with different mix-designs and material characteristics. The second objective was to investigate the effects of binder oxidative aging on HMAC mixture flexural stiffness and fatigue resistance. To achieve these objectives, compacted HMAC beam specimens were subjected to various accelerated laboratory aging exposure conditions (0, 3, and 6 months at 60C) prior to BB fatigue testing at 20C. Under strain-controlled BB testing, the results indicated that oxidative aging reduces HMAC mixture fatigue resistance and that the rate of Nf decay is mixture dependent. As theoretically expected, the HMAC flexural stiffness increased with aging due to binder oxidation and age-hardening. Overall the study has shown that the BB test protocol can be successfully utilized for laboratory fatigue comparative studies and performance predictions including investigating the effects of aging; however, it may not be very practical for typical routine HMAC pavement design analyses or rapid mix-designs and mixture screening due to its empirical nature and lengthy test-time. 2007 Taylor & Francis Group, London.
