| In Japan, recycling of asphalt mixtures has been practiced for more than 40 years. Since the mixing ratio of recycled aggregate is increasing every year, use of asphalt mixtures containing repeatedly recycled aggregate is expected to increase. However, sufficient knowledge regarding the repeated recycling has not been accumulated, and no clear understanding of the changes has been established. In this study, asphalt bitumen was aged in a laboratory and then applied a rejuvenator to restore its penetration in order to understand the property changes occurring in repeatedly aged and recycled asphalt bitumen and asphalt mixtures. This process was repeated multiple times and thereby an understanding of the properties of recycled asphalt materials was gained. In the results, although recy-cled asphalt bitumen recovered its penetration, its softening point shifted to a higher-temperature range in third recycling. Ductility only reached a level less than half of the initial ductility even after the first recycling process. Moreover, it was revealed that ductility exhibited almost no improvement in and after third re-cycling. In the black diagram curves from the DSR test, the phase angle transi-tioned to a smaller value range when asphalt bitumen progressed to recycle three times and five times. |
