Mechanical Properties, CO2 Emissions, and Environmental Impact Assessment of Asphalt Pavement Maintenance Containing High-Content RAP Asphalt Pavements

The global surge in reclaimed asphalt pavement (RAP) generation presents significant sustainability challenges and opportunities for resource conservation in road infrastructure. This study evaluated the feasibility and environmental impact of plant-mixed hot recycling technology using 60% RAP content in surface and intermediate courses based on a pavement maintenance project. Laboratory experiments were performed to evaluate the mechanical properties of stone mastic asphalt-13 (SMA-13), modified asphalt mixture-13 (GAC-13, G stands for Modified in Chinese), and modified asphalt mixture-20 (GAC-20) containing 60% RAP. Field performance was monitored post-construction. A process-based carbon emissions inventory quantified emission across raw material production, transportation, and construction phases. Volatile organic compounds (VOCs) emissions at the mixing plant and paving site were characterized using gas chromatography-mass spectrometry (GC-MS). Results demonstrated that all 60% RAP mixtures met the specification requirements for key mechanical properties and field performance, despite a 9.1% to 20.4% fatigue life reduction and slight decreases in moisture stability. Crucially, incorporating 60% RAP achieved significant carbon emission reductions of 36% to 37.4% compared to virgin mixtures. VOCs emissions were dominated by alkanes and amines, with composition influenced by mixture type and temperature. This study provides robust data supporting the technical viability and substantial environmental benefits of high-content RAP recycling technology, facilitating its wider adoption in sustainable pavement maintenance strategies.