Evaluation of recycled asphalt concrete pavement reinforced with hemp fiber as a sustainable pavement surface

The use of reclaimed asphalt pavement (RAP) and natural fibers in asphalt concrete (AC) has gained increasing attention as a sustainable alternative to conventional mixtures that use virgin materials. However, comprehensive evaluations of laboratory performance, production feasibility, field implementation, and environmental impact remain limited. This study evaluates AC mixtures that incorporate RAP as coarse aggregate with hemp fiber (HF) reinforcement. Mixture design was conducted using the Marshall method in accordance with the Department of Highways, Thailand, specifications, followed by laboratory testing, asphalt plant trials, field construction, carbon footprint, and cost analyses. The RAP-HF mixture, reinforced with 24-mm-long HF at 0.10% by aggregate weight, satisfied all specification requirements and exhibited superior performance to conventional AC, including 36% higher stability, 80% greater indirect tensile strength, and 40% higher indirect tensile resilient modulus. Plant and field trials confirmed production feasibility and consistent performance. Carbon footprint analysis indicated a 13.7% reduction in CO2 emissions per production batch. Meanwhile, cost analysis showed that the total production cost of the RAP-HF mixture was 2.7% lower than that of conventional AC. The combined improvements in mechanical performance, environmental impact, and cost demonstrate the potential of incorporating RAP and HF as a practical and sustainable solution for asphalt pavement construction.