Pavement

The use of recycled asphalt pavement (RAP) in asphalt mixes provides a vital basis for sustainable development. Maximising the re-use of RAP in its highest value application, as new asphalt product, has significant economic and environmental benefits.

The overall goal of the study was to provide guidance on the design and specification of RAP mixes and to reduce uncertainty surrounding the performance of asphalt mixes designed and manufactured with RAP. It was found that the binder blend characterisation according to AGPT/T193 is valid for a wide range of asphalt mixes and therefore it can be used with confidence for designing the binder blend in mixes containing RAP. It was also found that the addition of RAP to asphalt mixes, with different percentages of RAP and manufactured in different types of asphalt plants, does not have an adverse impact on the performance. This was assessed by using performance-based tests such as flexural stiffness, wheel-tracking and moisture sensitivity. Test results showed that the addition of 40% RAP, validated on large-scale asphalt production, did not have a negative effect on the in situ workability and thermal segregation.

A feasibility study concluded that the RAP can be subjected to recycling multiple times. A long-term monitoring of RAP sources showed that there is little variation within a stockpile; however, there is significant variation within stockpiles over time. A comprehensive sensitivity study, using the Monte Carlo simulation, was performed as part of the validation process to provide insight into the variability, impact and risk assessment for asphalt mixes containing RAP. Binder blend characterisation should be required for asphalt mixes with RAP content greater than 15%.

The report notes the importance of implementing a RAP management plan and proposes amendments to the Guide to Pavement Technology Part 4B: Asphaltto incorporate the binder blend characterisation for mix designs containing RAP.