Guide to Using Recycled Asphalt Pavement in Asphalt Mixtures

Abstract

Recycled asphalt pavement (RAP) can be used in roadway bituminous mixtures as a cost-effective portioned replacement of virgin aggregate skeleton and asphalt binder. To be successful, mixtures containing RAP should have similar characteristics to mixtures containing 100% virgin materials, and should offer equal or better long-term performance under harsh laboratory or field conditions.

Over the past 40 years, RAP mixtures in North America have performed satisfactorily when properly engineered, produced and placed. Field performance of RAP mixtures has been reported to be comparable or longer-lasting than asphalt mixtures with zero recycled content. However, as RAP use has increased Canadian agencies have observed signs of premature performance issues including cracking in asphalt pavements. This premature distress is particularly prevalent in mixtures with higher amounts of RAP.

A practice-ready technical guideline for the responsible use of RAP would involve the synthesis of a large volume of scattered data produced by academia and industry. It would also:

• Support consistent approaches to using RAP in asphalt mixtures across Canada
• Increase public agencies’ comfort and confidence in the longevity of RAP mixtures as they incorporate RAP into their contracts
• Allow agencies to reap the full range of benefits of using recycled materials in their road networks
• Give agencies an additional tool to achieve carbon emission targets

OBJECTIVES

The project would develop a practice-ready guideline on the use of RAP in asphalt mixtures that can be applied immediately by Canadian transportation agencies. The guideline would be based on effective agency practices and input from industry leaders, and would address material management, mixture design, plant production, and laydown of asphalt mixes produced with RAP to ensure proper performance.

Key project tasks leading to the development of the guideline would include:

• A review of international literature to summarize industry best practices and guidelines for RAP usage, with a focus on countries that have successfully used high recycled content over the last 20 years.
• A summary of findings from a 2021 survey of Canadian agencies on their use of RAP in asphalt mixes, and an update to relevant information.
• A summary of a series on online learning events held by TAC’s RAP Working Group in 2021-22.
• Development of a framework for Canadian agencies to share performance evaluations of RAP mixes.