Hemp Fiber-Modified Asphalt Concretes with Reclaimed Asphalt Pavement for Low-Traffic Roads

Reclaimed asphalt pavement (RAP) contributes substantially to the volume of recycled waste in the world. This research aims to evaluate the mechanistic performance of asphalt concrete with 100% RAP (RAP-AC) modified with natural hemp fiber (HF) reinforcement. The effects of HF lengths and HF contents on the mechanistic performance were investigated. The static tests included Marshall stability, strength index (SI), and indirect tensile strength (ITS), whilst the cyclic tests included indirect tensile resilient modulus (IT Mr), indirect tensile fatigue life (ITFL), and rutting resistance tests. The microstructural analysis revealed that HF could absorb more asphalt cement and function as a reinforcement. The 0.05% HF with a 24 mm HF length was suggested as the best ingredient. For various stress levels, the higher resilience properties—due to the addition of HF—contribute to higher levels of ITFL and rutting resistance. Based on a critical analysis of the cyclic test data, the distress model for HF-RAP-AC was developed for mechanistic pavement design. The outcome of this research promotes the usage of HF-RAP-AC as a greener material for low-traffic roads, which account for over 70% of the total roads worldwide.