The asphalt paving industry has been increasing the use of recycled asphalt pavement (RAP). There is a concern about the percentage of aged asphalt binder in the RAP that can actually be blended into the virgin binder and thus become available to coat the aggregate. In this study, a laboratory procedure was proposed for quantifying the mobilization rate of the aged binder using fluorescence microscopy. A new parameter, the mean gray value (MGV), was derived from the fluorescence image and used to differentiate between the recycled and virgin binders as well as their blends. A blending chart was generated according to the MGV for the virgin-aged asphalt blends containing 0–100% RAP binder and was used as a baseline for the quantification. A linear relationship was found between the MGV and the RAP binder content. A laboratory experiment was conducted to validate the proposed method. Glass cullet was added as a special type of aggregate so that it could be retrieved after mixing and tested by fluorescence microscopy. The results showed that the mobilization rate of the RAP binder from the fluorescent method was improved with an extended mixing time and an elevated temperature.

With the continuing increase in the use of recycled asphalt pavement (RAP) and recycled asphalt shingle (RAS) for highway construction, there is a concern over how much of the aged asphalt binder inside RAP/RAS can be blended into virgin asphalt binder. In this study, the RAP/RAS binder mobilization rates of 13 different mixtures produced by three different types of asphalt plants in Tennessee were determined using fluorescence microscopy and gel permeation chromatography (GPC). A multiple regression model was developed to explore the factors critical to enhancing the mobilization rate of the RAP/RAS binder. Results showed that the RAP/RAS binder mobilization rate was significantly lower than 100% for most mixtures, indicating that only part of the RAP/RAS binder was mobilized during the production process. The mixing and delivery temperatures had significant influence on the mobilization rate of RAP/RAS binder. In addition, the aging degree of RAP/RAS binder also significantly affected the mobilization rate.

Nitric oxide (NO) emitted from vehicle exhausts are associated with adverse health effects on the public. This study prepared a graphitic carbon nitride (g-C₃N₄)/TiO₂ composite using melamine and titanium dioxide (TiO₂) and then applied the composite on chip seal for the photocatalytic removal of NO. The g-C₃N₄/TiO₂ composite was synthesised by an ultrasonic-assisted solid-phase synthetic method. The results of X-ray powder diffraction, Fourier-transform infrared spectroscopy, and a scanning electron microscope indicated that g-C₃N₄ and TiO₂ were successfully synthesised and most of the sheet structures of g-C₃N₄ were attached by approximately spherical TiO₂ particles. The UV–Vis and PL characterisation suggested that optical absorption range of TiO₂ was broadened and the separation of electronic-holes was hindered, which contributed significantly to the enhancement of the visible-light photocatalytic activity. The loading capacity of 0.0092 kg/m² g-C₃N₄/TiO₂ composite on chip seal specimens had the highest NO removal efficiency of 31.41% within 30 min.