Influence of the chemical composition and the morphology of crumb rubbers on the rheological and self-healing properties of bitumen

Abstract Three crumb rubbers (CRs) from typical waste tires were used to modify two base bitumens. The chemical compositions and the morphologies of CRs were characterized by the thermogravimetry-mass spectrometer (TG-MS) and the scanning electron microscope (SEM), respectively. The rheological and self-healing properties of CR modified bitumen (CRM binder) were investigated by the Brookfield viscometer, the bending beam rheometer (BBR) and the dynamic shear rheometer (DSR). The results indicated that the styrene butadiene rubber with the benzene ring had a better compatibility with base bitumen and can influence its viscosity and dynamic rheological properties more. The natural rubber with a simpler chemical structure (isoprene) can reserve more flexibility and its CRM binder had a better low-temperature creep performance. The butyl rubber with the granular morphology contributed less to the property change of base bitumen. Due to the re-swelling effect of crumb rubber (especially for the styrene butadiene rubber) during the fatigue, the self-healing properties of the base binder got improved with respect to the recovery of fatigue life and initial complex modulus. The results will helpful to better understand the interaction mechanism between CR and bitumen, as well as to guide the production of the CRM binder with excellent properties in industry.