Hiroyuki Nitta

Smart photonic coating for civil engineering field: for a future inspection technology on concrete bridge

Here we will propose the conceptual new idea of the inspection of concrete bridge using smart materials and mobile IoT system. We apply opal photonic crystal film to detect cracks on concrete infrastructures. High quality opal photonic crystal films were coated on black color PET sheet over 1000 cm2 area. The opal film sheet was cut and adhered to concrete or mortar test pieces by epoxy resin. In the tensile test, the structural color of the opal sheet was changed when the crack was formed. As a demonstration, we have installated the opal film sheet on the wall of the concrete bridge. Our final purpose is the color change will be recorded by portable CCD devices, and send to expert via IoT network.

An Examination of Property Changes of Repeatedly Recycled Asphalt Bitumen Using Rejuvenator with High Aromatic Content

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 recycled 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 recycling. In the black diagram curves from the DSR test, the phase angle transitioned to a smaller value range when asphalt bitumen progressed to recycle three times and five times.

THERMAL PROPERTY AND VISCOELASITC PROPERTY OF THE WARM-MIX ASPHALT BINDER

The warm-mix asphalt technics have been applied to the hot asphalt pavements to improve the quality of constructions and to reduce CO₂ emission. Although many studies have reported that the warm-mix additives affected the physical characteristics of asphalt mixtures, the basic characteristics of the warm-mix asphalt binder has not been revealed. In this investigation, the authors measure the differential scanning calorimetry (DSC) and the viscoelastic property of the warm-mix asphalt binder in a wide range of temperature. Also, they discuss the validity of the thermal analysis to detect the physical change of the asphalt binder. 施工性改善やCO₂排出削減などを目的として，加熱アスファルト舗装に対する中温化技術の開発や利用が進んでいる．これまで，中温化剤の添加によるアスファルト混合物の物理的性状の変化は多く報告されているが，アスファルトバインダの基礎的な物理性状については十分な言及がなされていない．本研究では，中温化剤によるアスファルトバインダの性状変化を把握することを目的として，示差走査熱量測定によりアスファルトや中温化剤の広範囲の温度域での熱特性や，これに対応した粘弾性状を調べた．さらに，熱特性と粘弾性状の関係について検討した．