Evaluation of the blending effectiveness of reclaimed asphalt pavement binder

There is a recent trend of using a higher content of reclaimed asphalt pavement (RAP) in asphalt pavement construction. When evaluating the properties of mixed RAP and virgin binder and selecting a base binder to be mixed with a high-RAP mix using a blending chart, the effect of partial blending is sometimes neglected and total blending is assumed. Such an assumption, however, has been found unreasonable. Based on an experimental gap-graded method, this paper studies blending effectiveness in RAP-binder and virgin-binder systems using both rutting and fatigue parameters and quantified the degree of blending using blending ratios. Furthermore, the blending ratios were applied to predict the properties of the blended RAP and virgin binder as well as to develop a modified blending chart for estimating the performance grade (PG) of the virgin binder when a higher RAP content was used. Results confirmed that partial blending does exist during the blending process. Blending ratios were found to be a function of RAP content, but not sensitive to the specific rutting and fatigue parameters evaluated. For higher RAP content, a modified blending chart is recommended to take partial blending into account. It was also found that the usage of a recycling agent could improve the properties and blending effectiveness of high-RAP binders in terms of both rutting and fatigue properties.