Influence of surface area and size of crumb rubber on high temperature properties of crumb rubber modified binders

There are many variables of crumb rubber modifier (CRM) and asphalt binder, affecting the interaction of the CRM with the binder when crumb rubber modified binder (CRM binder) is produced. In this study, the influence of the surface area of CRM blends on the high temperature properties, i.e., the complex modulus (G∗), the phase angle and high temperature grade of the CRM binders was investigated. To this end, the surface areas of CRM particles were measured using the BET (Brunauer, Emmett and Teller) tester, while weighted average particle size of CRM blends was calculated based on their graduations and then used as a size index. High temperature properties of CRM binders were measured using Dynamic Shear Rheometer (DSR) test. A total of 108 CRM binders were produced using different combinations of these variables. Results observed from this study indicated: (1) the surface area of the ambient CRM was twice as large as that of the cryogenic one, leading to a much higher G∗ and phase angle of the CRM binders; (2) the phase angle and G∗ were affected by both the surface area and average size; however, the average size is the predominating factor; and (3) ambient CRM binders were produced about 3 °C in high temperature grade higher than cryogenic CRM binders.