Availability adjusted mix design method as a tool to mitigate the adverse effects of RAP on the performance of asphalt mixtures

• Published in: Construction & building materials 2024-04, Vol.422, p.135813, Article 135813
• Main Authors: Mocelin, Douglas Martins, Isied, Mayzan Maher, da Costa, Rafaella Fonseca, Castorena, Cassie
• Format: Article
• Language: English
• Subjects: Availability adjusted mix design method; Reclaimed asphalt pavement; Recycled binder availability
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2024.135813

The use of high percentages of reclaimed asphalt pavement (RAP) in asphalt mixtures offers economic and environmental advantages. However, state agencies place limits on RAP usage to avoid its indiscriminate use without a full understanding of its long-term performance implications. To achieve a more informed and rational use of higher RAP contents, it is essential to quantify recycled binder availability (RBA) and incorporate it into asphalt mixture design. The current design methods often assume complete RBA, leading to less durable mixtures. Standardized mixture design methods fail to rigorously account for the effects of RBA on the volumetric composition of asphalt mixture. Recently, the availability adjusted mixture design (AAMD) method was developed to address these issues by explicitly considering partial RBA in the interpretation of mixture volumetric properties and accounting for the role of RAP agglomerations on aggregate structure. This study tests the hypothesis that the AAMD method can mitigate the adverse performance consequences of RAP through the control of ‘available’ volumetric and effective binder properties. This was achieved by comparing virgin and RAP mixtures designed with similar ‘available’ volumetric properties according to the AAMD method. Additionally, control mixtures with RAP contents ranging from 20 to 35 percent were compared to AAMD mixtures with similar ‘available’ volumetric properties designed with the same RAP content and with 50 percent RAP. The collective results demonstrate that the AAMD method effectively mitigates negative performance consequences of RAP by controlling the ‘available’ volumetric and effective binder properties. •The Availability Adjusted Mixture Design (AAMD) method is able to mitigate adverse effects of RAP through the control of ‘available’ volumetric and effective binder properties.•Asphalt mixtures designed through the AAMD method present improved cracking performance as compared to mixtures designed through Superpave method for the same intended volumetric properties.•Mixtures with increased RAP content – up to 50 percent – designed with AAMD method presented a better cracking performance than Superpave designed mixture with lower RAP content.•AAMD method is a rational approach to interpret the impact of recycled asphalt materials in asphalt mixtures and can be used to design RAM mixtures accurately to obtain the desired performance.