Effect of Repeated Use of Substandard Reclaimed Asphalt Pavement on Physical and Chemical Properties of Recycled Asphalt and Its Relationship with Recycled Mixture Performance

With the repeated recycling of hot mix asphalt (HMA) mixtures, an increase in substandard reclaimed asphalt pavement (RAP), in which the penetration of the aged asphalt binder has fallen below the specification limit, is expected. This study investigated the relationship between recycled HMA mixtures subjected to repeated deterioration and recycling using RAP with different degrees of aging and the recycled asphalt binders recovered from these mixtures, with the aim of promoting the effective utilization of substandard RAP in the future. The results indicated that changes in molecular and colloidal structures caused by oxidative aging led to hardening and embrittlement of the asphalt binder, and brought about a decrease in crack resistance of the recycled HMA mixtures. Furthermore, the adhesive strength index termed FD and the carbonyl index of recycled asphalt showed a high correlation with the indirect tensile strength ratio of the recycled HMA mixture. It means that these indices can serve as effective indicators for performance evaluation and deterioration assessment of recycled asphalt binders.