Effect of waste tyre rubber size on physical, rheological and UV resistance of high-content rubber-modified bitumen. (18th October 2021) - Jamal, Muhammad
Graphical abstract: Highlights: The effect of crumb rubber particles size is studied in the manufacturing of rubberised bitumen. Coarser crumb rubber particles are found to be thermally stable as compared to finer particles. Rubberised bitumen is less vulnerable to UV deterioration than standard bitumen. Finer crumb rubber particles reduce viscosity of the blend compared to coarser particles. Abstract: This study is focused on the effect of crumb rubber (CR) particle size on the physical, chemo-rheological, UV ageing resistance and storage stability of high-content rubberised bitumen. Two CR gradations, #30 (coarser) and #50 (finer), were selected for this study. The blends were prepared by mixing 22.5% CR (by weight of base bitumen) into 50/70 pen grade bitumen for 60 min at 177 ± 10 °C with a shear mixing speed of 700 rpm. Blends prepared with #30 CR were found to improve the elastic response and storage stability compared to #50 CR modified binder. The presence of a greater number of coarser CR particles – which mostly remained in the swollen-form at the end of the blending process – as compared to finer particles – which instead were depolymerized and released the absorbed oils back into the binder phase – proved to increase the flexibility of the binder and improve its rheological performance. This same factor also reduced the #50 modified binder's UV resistance as the C–C, C–H bonds in the saturates portion of the bitumen have a lower bond energy than the energy produced by the impact of UV rays. Overall, crumb-rubber modified bitumen resists better to ageing produced by UV radiation compared to standard unmodified bitumen. Further reprocessing of waste vehicle tyres into smaller #50 mesh size is deemed not to produce substantial improvements in the final bituminous blend other than the reduced viscosity for the same CR content.