Maximizing the circularity of asphalt pavements by improving the RAP content in recycled asphalt mixtures

To increase the content of reclaimed asphalt pavement (RAP) materials in reconstructed asphalt pavements, this study introduced an enhanced graded recycling (EGR) method, supplemented by the addition of a bio-rejuvenator and basalt fibers to further enhance the performance of recycled asphalt mixtures. The performance of composite recycled asphalt binder was investigated using chemical composition tests, multiple stress creep and recovery tests, and bending beam rheometer (BBR) tests. The morphological characteristics and crushing tests of recycled aggregates were carried out to determine the material proportions of new and waste aggregates. Asphalt mixtures with varying RAP contents (20 %, 40 %, 60 %) were prepared using the EGR method and subjected to low-temperature, high-temperature and water stability tests. It was found that the chemical fractions and rheological properties of aged asphalt binders could be effectively restored using a rejuvenator. The high-temperature and low-temperature performance of the composite recycled binders could be improved by the incorporation of basalt fibers. The mechanical properties and morphological characteristics of recycled aggregates were close to those of new aggregates. The mass ratio of 1:1 between new and recycled aggregates was recommended. The low-temperature performance and water stability of the recycled asphalt mixture prepared using the EGR method could be improved without compromising the high-temperature performance.