Rheology investigation of crumb rubber modified asphalt binders

The incorporation of crumb rubber into asphalt pavement mixes is designed to enhance binder properties through reducing the binder’s inherent temperature susceptibility. During the interaction process, crumb rubber particles swell after absorbing a portion of the oils in the binder, resulting in the increase of binder viscosity. In this study, the Crumb Rubber Modified (CRM) asphalt binders were produced using virgin binder of Performance Grade (PG) 64-22 and ambient rubber with various concentrations (10%, 15%, and 20% by weight of virgin binder) in the laboratory. Rheological analyses (flow behavior, elasticity, loading dependence, and temperature dependence) of the control virgin binder and the CRM binders were conducted using a Bohlin Dynamic Shear Rheometer (DSR) II. The results indicated that (1) the use of crumb rubber as a modifier seemed to improve the penetration resistance of the asphalt binder because of the increased viscosity at 60oC, (2) its advantage was more apparent at lower frequencies of loading, and (3) the asphalt binder with higher crumb rubber contents was observed to have better resistance to permanent deformation at higher temperatures and elasticity at lower temperatures.