Compatibility assessment and performance evaluation of post-consumer polypropylene-modified viscosity grade bitumen using maleic anhydride

Utilising Polypropylene (PP) in the bitumen modification is one of the promising and sustainable solutions if the phase separation issue is handled carefully. This study investigated the effectiveness of in-situ grafting of maleic anhydride (MAH) as a chemical compatibiliser in reducing phase separation and improving compatibility between PP and bitumen. PP-modified bitumen (PP-MB) shows improved stiffness and thermal stability, while MAH-grafted PP-MB (MAH-PP-MB) further enhances its performance. Rheological improvement was observed in MAH-PP-MB, with an increased percentage recovery from 0.25% to 12.06% and decreased non-recoverable creep compliance from 3.17 to 0.65 kPa−1, indicating enhanced resistance for rutting. Improved fatigue life was also observed at 4% PP with 0.4% MAH dosage. Fourier transform infrared spectroscopy results confirmed additional carbonyl, C–O and O–H interactions. This study further extended to measure mixture-scale properties like rutting tolerance (IDEAL-RT), cracking tolerance (IDEAL-CT) and tensile strength ratio (TSR). The highest RTindex is observed for the MAH-PP-MB as 174.74 with the highest TSR of 94.26%, indicating superior rutting and moisture resistance. The PP-MB mixture reduces the cracking tolerance, while MAH-PP-MB significantly improves the same. Overall, the mixture performance results strongly validate binder-level findings and confirm that in-situ MAH grafting effectively improves rutting, cracking and moisture resistance at the mixture scale.