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－　　－13Experimental Study to Re-refine Aged Binder Using WaterYosuke KANOIn Japan, most road surfaces are asphalt pavement, and there is more than 40 years of experience in recycling them. In recent years, 99% of asphalt concrete waste has been recycled as reclaimed asphalt pavement (RAP). The RAP content of recycled hot mix asphalt (RHMA) is gradually increasing, reaching 50% nationwide and 65 to 85% in urban areas. The production volume of RHMA accounts for 80% of the total HMA. If the pavements have been in service for 10 to 15 years, the RAP would have already been recycled 3 to 4 times. This means that RHMA in Japan contains a large amount of binder that has been repeatedly aged and rejuvenated. When reusing RAP for RHMA, various rejuvenating agents are added to improve the aged binder’s properties. However, the rejuvenating effect may be inadequate depending on the components and the binder’s aging degree. Some pavements may be short-lived with recycling, as some rejuvenating agents are not sufficiently effective in repeatedly restoring ductility. Therefore, we need to establish a sustainable recycling system and ways to predict and prolong the lifespan of RHMA. Our research team is working on these goals by developing entirely new technologies in addition to improving existing methods. Specifically, its missions are to elucidate the aging and rejuvenation mechanism of bitumen, understand the long-term effects of rejuvenators, separate aggregates and binders from the asphalt concrete waste, and rejuvenate repeatedly recycled binders. With existing methods, prolonging the lifespan of RHMA must rely on the long-term effects of rejuvenators. (Note: Regarding the last two missions, Figure 1 shows the concept of separation recycling technology under development, and Table 1 shows the properties of the binder rejuvenated by that technology. Figure 2 shows the appearance and properties of the aggregate separated from RAP. Through these processes, both used materials can be restored to almost the same quality as the unused ones.)Keywords: reclaimed asphalt pavement, recycled hot mixed asphalt, rejuvenating agent, asphalt binder水を用いた老化アスファルトの若返り技術　近年，アスファルトコンクリート塊の99％がアスファルト混合物再生骨材（以下，再生骨材）としてリサイクルされ，アスファルト混合物全出荷量の80％程度を再生加熱アスファルト混合物（以下，再生混合物）が占めている．さらに，再生混合物に対する再生骨材配合率は増加傾向にあり，全国平均で50％，都市部では65～85％に達している．以上から，アスファルト舗装の供用期間を10～15年とした場合，再生骨材は既に3～4回程度のリサイクルを重ね，老化と若返りを繰り返した旧バインダーが再生混合物を構成している状況が考えられる．再生骨材を再利用する際は，旧バインダーの性状を再生用添加剤（以下，再生剤）により回復させる手法が一般的であるが，再生剤の組成や旧バインダーの老化程度によっては繰り返しの回復効果が十分に得られず，舗装が早期に破損する可能性がある．当研究チームでは現行手法の改良に加え，新技術の開発により持続可能なリサイクルシステムの構築にアプローチしている．具体的には，リサイクルに伴う旧バインダーの老化・若返りメカニズムの解明，再生剤の組成が長期供用性に及ぼす影響の把握，熱水を用いた分別再材料化技術と旧バインダーの性状回復技術の開発である．図1に分別再材料化技術の概念を，表1に本技術により回復させた旧バインダーの性状，図2に舗装廃材から分別回収した骨材の外観および性状を示す． これらのプロセスを経て，アスファルトコンクリート塊が含有する骨材と旧バインダーを概ね未使用の状態に復元できる可能性を確認しており，引き続き共同研究を拡充しながら本技術の実用化を目指したい．キーワード：アスファルト混合物再生骨材，再生加熱アスファルト混合物，再生用添加剤Journal（掲載誌）ISAP (Asphalt Pavement & Environment), Proceedings of the 5th International Symposium, 303-312, Sep. 2019.Published Paper