Rubber-Bitumen Interaction of Plant-Blended Rubberized Bitumen Prepared Under Various Blending Conditions

Rubberized bitumen produced from waste tyre rubber has been widely used as a sustainable paving material around the world. However, different production conditions may lead to rubberized bitumens with different performances. This study aims to understand the mechanism of physicochemical interaction between rubber particles and virgin bitumen of plant-blended rubberized bitumen prepared under various blending conditions. To achieve this objective, samples of plant-blended rubberized bitumen prepared under four conditions were first collected, including blending at 170 °C for 1 h, and blending at 170 °C for 1 h followed by blending at 183 °C for 1, 3, and 5 h. Then the microstructure, viscosity, storage stability, and rheological properties of these samples were characterized. Microstructural results indicate main crosslinking structures of rubber particles remain stable and undamaged with the occurrence of chemical reactions including oxidation, decarboxylation, and devulcanization during the whole production period. The storage stability results state the rubberized binder exhibits no obvious phase separation after storage at 163 °C for 48 h, and becomes more stable as the blending time prolongs. The rheological results indicate the rubber-bitumen interaction is mainly composed of early-stage absorption and swelling of rubber particles, continuous emission of volatile bitumen fractions, and late-stage partial degradation of fully swollen rubber particles.