Field aging effects on fatigue of asphalt concrete and asphalt-rubber concrete

A study was undertaken to investigate the influence of field aging on the fatigue performance of asphalt concrete and asphalt-rubber concrete. Two California mixes were investigated: conventional asphalt concrete dense graded (CAC-DG) and asphalt-rubber hot-mix gap graded (ARHM-GG). Laboratory fatigue tests were conducted on beam specimens obtained from a 10-year-old pavement section in southern California. Both stiffness and fatigue were determined using controlled-strain fatigue beam tests performed at 22degreesC and -2degreesC. Results were compared with published data for the original (unaged) materials. Stiffness and fatigue data were also used in pavement analysis to assess the influence of aging on predicted fatigue performance. Results indicate that field aging reduced the beam fatigue resistance of CAC-DG and, to a lesser extent, ARHM-GG. Aging effects on beam fatigue life were more severe at -2degreesC than at 22degreesC. The influence of aging on predicted pavement fatigue life depends not only on the stiffness of the mix and its fatigue properties but also on the stiffness or layer moduli of the pavement components. For new pavement construction and overlaid pavement sections, longer fatigue life predictions were obtained for ARHM-GG than CAC-DG for both aged and unaged conditions. Aging of CAC-DG could be detrimental to pavement fatigue. In comparison, aging of ARHM-GG showed increased fatigue life performance.