Investigation of Recycled Asphalt Pavement Materials Treated by Refined Crushing and Screening Process: Comparison with Conventional Methods

Using recycled asphalt pavement (RAP) materials in the pavement industry is a hot issue now, which can reduce carbon emissions significantly. The agglomeration and variability of the RAP materials treated by a conventional crushing and screening process present a challenge for the gradation design and variability control of the reclaimed asphalt mixture, resulting in a lower RAP content and thus a limited environmental and economic benefit. To address it, a refined crushing and screening process was employed for the RAP material to separate the asphalt mortar and the coarse aggregates in this study. To evaluate its applicability on the RAP material, the basic composition, agglomeration degree, variability, and gradation refinement of the RAP material were discussed. The aggregate dispersion uniformity and road performance of the reclaimed asphalt mixtures made with the obtained RAP materials were further investigated; the correlation between the RAP properties and the road performance of the reclaimed asphalt mixture was explored. The results show that the agglomeration degree and variability of the coarse RAP material are reduced significantly by the refined crushing and screening process. The use of the RAP material treated by the refined crushing and screening process can largely improve the uniformity of aggregate dispersion and conventional road performance compared with the use of the RAP material treated by conventional methods. Pearson correlation analysis demonstrates that the RAP agglomerates increase the variability of 4.75 mm sieve passage rates and the asphalt-aggregate ratio, resulting in an uneven distribution of aggregates in the structural composition, thus reducing the moisture sensitivity and fatigue performance. By utilizing the refined crushing and screening process, the variability of the RAP materials can be considerably reduced, thereby enhancing the RAP content and the key performance of reclaimed asphalt mixture. The popularization of the refined crushing and screening process is an effective approach to promote the high-quality use of the RAP materials.