Utilizing Fluorescence Microscopy for Quantifying Mobilization Rate of Aged Asphalt Binder

Abstract

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.