Volume 40, Issue 5 (September 2012)
High-Temperature Viscosity Performance of Crumb-Rubber-Modified Binder With Warm Mix Asphalt Additives
The application of crumb-rubber modifier (CRM) in asphalt mixtures has been proven to increase the viscosity of CRM binders. In recent years, warm mix asphalt (WMA) additives have been employed to CRM binders to lower their viscosity at high temperatures, allowing a decrease in the mixing and compaction temperatures. The objective of this research is to investigate the viscosity and storage stability of rubberized WMA binders with different tire rubber concentrations and WMA additives. The tire rubber of 40-mesh, with concentrations of 10 %, 15 %, 20 %, and 25 % by weight of a Superpave performance grade (PG) 64-22 asphalt binder, were used in this study along with the WMA additives, such as Sasobit, RH and Advera. Viscosity tests were conducted on the rubberized WMA binders using the rotational viscometer at four temperatures (135, 160, 177, and 190°C). The statistical analysis of variance (ANOVA) was applied to quantify the respective effects of the influencing factors on the CRM binder’s viscosity. The test results indicated that the addition of crumb rubber could greatly increase the viscosity of asphalt binders, which could be improved continuously at increased crumb-rubber concentrations. However, when considering different WMA additives, the crumb rubber showed different effects on the viscosity of the binder. The three WMA additives could all reduce the viscosity of the CRM binder; in addition, RH had the most significant effect on viscosity reduction. It was also found that the CRM binders with WMA additives had good storage stability. For example, the viscosity of the CRM binder with 10 % rubber concentration and RH only increased by 3.8 % after being stored for 4.5 h.