Quantitative assessment of the parameters linked to the blending between reclaimed asphalt binder and recycling agent: A literature review

The lack of understanding the mechanisms governing the interaction between reclaimed asphalt binder (RAb)(1) and recycling agents is one of the technical issues that still need to be resolved when high amount of reclaimed asphalt (RA)(2) is used in a new recycled asphalt mixture (RAM). Due to important role of RAb in that interaction and increased used of RA, it becomes necessary to have a way to classify RA, as any other material used in asphalt mixture production. It is very important to determine how much RAb is active by itself (DoA)(3), but also to determine how much RAb can be considered available for a mix design of RAM (DoAv)(4) when a recycling agent is used. Finally, since that RAM's properties are strongly dependent on the degree of blending between RAb and recycling agent (DoB)(5), it should evaluate to what extent RAb contributes to the final properties of RAM. These blending parameters (DoA, DoAv and DoB) are so crucial that identifying suitable methodologies for their assessment would be extremely important in performing a proper mix design due to dangerous of having a lack of active bitumen in RAM. This paper presents a literature review of methods which have been used for the evaluation and assessment of mentioned parameters, grouped in four macro-areas: mechanical, chemical, visualization and mechanistic approaches. Furthermore, summarized review of used methods was prepared together with their critical review, all with aim to find appropriate methods for determining these parameters.