Evaluation of swelling and degradation rates in crumb rubber modified bituminous binders

The mutual interaction between crumb rubber (CR) and base bitumen is crucial for the stability and performance characteristics of crumb rubber-modified (CRM) binders. This study evaluates the swelling and degradation phenomena during the rubber-bitumen blending process, focusing on selecting the appropriate CR type and optimizing CRM binder production. Laboratory experiments assessed the evolution of viscosity over time for various CRM binders with differing CR types and contents. The Swelling and Degradation rates were introduced as key parameters to quantitatively measure interaction kinetics. The results indicated that the maximum swelling rate reached 160 cP/min at a 22 % CR dosage, while the degradation rate was observed at 55 cP/min. The swelling degree, quantified by the peak viscosity of 12,000 cP, was predominantly influenced by CR content. Additionally, CRM binders containing finer CR particles exhibited a faster swelling rate and lower degradation, reducing viscosity by up to 30 % post-peak. The findings of this research demonstrate that CR characteristics, including particle size and surface area, significantly impact the stability and performance of CRM binders, providing valuable insights for optimizing binder formulations.