Influence of combined aging on the mechanical and physical properties of reclaimed asphalt pavement mixtures blended with rejuvenator agents

Recently, reclaimed asphalt pavement (RAP) with high RAP contents with rejuvenator agents have been implemented in Japan. However, a unified view of the durability of RAP mixtures with rejuvenators has not been established. Therefore, this paper aims to assess the durability of RAP mixtures blended with different types of rejuvenators through combined aging, compared with that of hot mixed asphalt (HMA) mixture. Mechanical and physical properties of RAP mixtures with rejuvenators subjected to a combination of moisture, heat, and oxidation were investigated. Saturation aging tensile stiffness conditioning was used to simulate the combined aging. Four types of RAP mixtures were prepared by employing two types of oil-based rejuvenators with two RAP contents. HMA mixtures were also prepared. The test results demonstrated that the RAP mixtures did not exhibit a reduction in the retained stiffness, whereas the HMA mixtures exhibited a significant drop in stiffness with conditioning. In addition, the RAP mixtures exhibited a longer residual service life than the HMA mixtures after conditioning. Detailed analyses revealed differences in the stiffness and fatigue behaviors of the RAP mixtures with different types of rejuvenators. Finally, certain aspects of the deterioration mechanisms of RAP mixtures with rejuvenators were discussed.

     

Polybrominated diphenyl ethers (PBDEs) and organochlorines in melon-headed whales, Peponocephala electra, mass stranded along the Japanese coasts: maternal transfer and temporal trend

Polybrominated diphenyl ethers (PBDEs) and organochlorine compounds (OCs) were determined in the blubber of 55 melon-headed whales (Peponocephala electra) mass stranded along the Japanese coasts since 1982. DDTs and PCBs were predominant in all the specimens investigated. In whales that died during the latest event in 2006, concentrations of PBDEs (190–510 ng/g lipid wt) were approximately two orders of magnitude lower than DDTs and PCBs, but comparable with HCHs and HCB. Maternal transfer of PBDEs to offspring through the whole reproductive process was estimated to be 85% of the mother's body burden, while that occurring during gestation was much lower (2.6–3.5%). Concentrations of PCBs, DDTs, and HCB were lower in melon-headed whales stranded after the year 2000 than those stranded in 1982, whereas PBDE and CHL levels showed a temporal increase during the past 20 years, suggesting that the peak of their usage and contamination occurred after the year 1982.