Chemical pretreatment effects on rubberized asphalt: rutting performance enhancement through potassium permanganate and hydrogen peroxide oxidation

The poor compatibility between crumb rubber (CR) and asphalt binder limits the performance of rubberized asphalt (RA). To address this, CR was pretreated using potassium permanganate (KMnO 4 ) and hydrogen peroxide (H 2 O 2 ) as solution-based oxidizing agents. This study investigated the effects of these pretreatments on rutting resistance. The chemical modifications of CR were characterized using Fourier-transform infrared spectroscopy (FTIR) and thin-layer chromatography with flame ionization detection (TLC-FID). The rheological and mechanical performances were assessed using a dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), and wheel-tracking (WT) tests. Statistical approaches, including principal component analysis (PCA), partial least squares regression (PLSR), response surface methodology (RSM), and Arrhenius-based kinetic modeling, were employed to elucidate chemical-mechanical relationships. The results showed that pretreatment significantly increased the intensities of carbonyl (C=O) and sulfoxide (S=O) groups in CR, leading to a higher asphaltene fraction and enhanced binder stiffness and hardness. Both KMnO 4 and H 2 O 2 pretreatments improved rutting resistance, with KMnO 4 demonstrating superior effectiveness. The aggregate type also played a critical role, with limestone mixtures exhibiting greater relative improvements (up to 46% with KMnO 4 and 23% with H 2 O 2 ) than basalt mixtures (41% and 34%, respectively). While pretreatment enhanced rutting parameters and asphalt–rubber interaction, it also increased recoverable creep compliance, indicating potential trade-offs with elasticity and fatigue performance. These findings highlight that chemical pretreatment of CR is an effective approach to improve rutting resistance but requires careful balance with long-term durability.