Moisture and rutting resistance of recycled polypropylene fiber-modified dense bituminous mix

This study evaluated the moisture susceptibility of the polypropylene-modified bituminous mix (PPMBM) by durability index (DI) and rutting depth using recycled polypropylene fiber (RPPF) as a modifier. Varied percentages of RPPF by weight of optimum bitumen content were used to prepare PPMBM by the wet method and tested for various durations of water submersion to determine the DI curve. The moisture susceptibility was evaluated using indirect tensile strength and tensile strength ratio (TSR) tests, as well as the wheel tracking test for rutting. Thermo-gravimetric analysis and differential scanning calorimetry tests demonstrate that recycled polypropylene fiber-modified bitumen (PPMB) has superior thermal performance when compared to virgin bitumen. According to Fourier transform infrared (FTIR) spectroscopy, the modification of virgin bitumen using RPPFs to produce PPMB is a physical process. For all submersion durations, 2% RPPF-enriched PPMBM provided the greatest stability. Retained Marshall stability (RMS) value demonstrated that 2% RPPF-enriched PPMBM exhibited a significant increase in RMS value. At 2% RPPF-enriched PPMBM, the DI value is minimum, the TSR value increases to 93.67%, and the rutting depth is greater compared to other PPMBM under various submerged conditions.