Design and Performance of High-RAP-Content Asphalt Mixture: A Case Study in Jianghe Expressway

Rapid expansion of global transportation infrastructure leads to the accumulation of vast quantities of reclaimed asphalt pavement (RAP). Recycling RAP is essential for reducing environmental impacts. However, current recycling practices typically limit RAP content to below 30%. Increasing RAP content in asphalt mixtures—especially beyond 50%—offers a more sustainable approach, but also introduces challenges in performance, design, and implementation. This study presents a case in which the hot central plant recycling asphalt mixture containing 50% RAP, enhanced with an active rejuvenating agent, was used for the lower layer of the Jianghe Expressway. The aggregate gradation was designed using the Marshall method, with the optimal asphalt–aggregate ratio determined to be 3%. The average compaction degree was 98.9%, the infiltration coefficient ranged from 6.43 mL/min to 23.77 mL/min, and the standard deviation of flatness did not exceed 1.0. However, material shoving was observed during paving, suggesting that, with appropriate adjustments, the technique can be optimized for large-scale implementation. The gradation of the RAP material showed minimal deviation from the design gradation, remaining within ±5%. The compaction scheme with eight roller passes and a loose paving coefficient of 1.35 yielded superior compaction performance.