A practical approach to estimate the degree of binder activity of reclaimed asphalt materials

Using Reclaimed Asphalt (RA) in new asphalt mixtures can reduce the amount of new material required thereby saving money and natural resources. In addition, asphalt mixtures with RA have shown comparable properties and performance to that generally associated with asphalt mixtures made with 100% virgin material. However, RA content in pavement surface layers is still limited due to specification and technical limitations. For higher contents, the aged RA binder must be analysed to accurately determine the requirements for virgin binders and additives while the degree of blending (DOB) between the RA binder and the virgin binder also needs to be quantified. This is not a simple process and generally designers assume one of two opposing theories associated with 100% (full blending) or 0% (“Black Rock”) DOB. This paper proposes a new approach to estimate a unique property of the RA known as the Degree of Binder Activity (DoA) as a function of the processing temperatures of the RA. The study showed positive results and indicated that this DoA approach can be used as a tool to better understand RA in order to improve the binder/blend design for recycled asphalt mixtures

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