Surface area of crumb rubber modifier and its influence on high-temperature viscosity of CRM binders

In general, crumb rubber modifier-modified binders (CRM binders) have better performance properties than base binders and thus, are becoming more widely used in pavements in a few states. However, the mechanism by which the interaction between the asphalt base binder and the CRM blends added takes place has not been fully characterised. In this study, the surface areas of CRM were at first measured using the Brunauer, Emmett and Teller (BET) tester. Second, 108 CRM binders were produced using different combinations of CRM blend variables and mixing conditions and consequently tested for their viscosity at 135C. The influence of the surface area and the average size of the CRM blends on the viscosity of the CRM binders was statistically investigated. Results from this study indicated that: (1) the surface area of the ambient CRM is almost twice as large as that of the cryogenic CRM, leading to an increase in the viscosity up to 16-58% over cryogenic CRM binders and (2) the viscosity of the CRM binders has a moderate correlation with both the surface area and the average size of the CRM blends, but is prevailingly influenced by the average size of the CRM blends.