Rheological and environmental characteristics of crumb rubber asphalt binders containing non-foaming warm mix asphalt additives

Abstract

Introducing crumb rubber (CR) into asphalt binder can both provide environmental benefits such as conservation of natural resources and conservation of landfill space and significantly improve rheological and mechanical performance characteristics of asphalt binders. Incorporation of CR into asphalt binder demands some amount of kinematic energy to make modified asphalt binder sufficiently fluid for mixing and compaction purposes that liberates some greenhouse and fume emissions. By taking advantage of warm mix additives (WMA), it is possible to effectively reduce the production temperature of hot-mix asphalt mixtures to mitigate such environmental concerns. This study, Firstly, aims to investigate the CR dosage effect on the properties of asphalt binder containing different non-foaming warm mix additives: Sasobit and Evotherm M1. Secondly, the environmental concerns regarding CR inclusion into asphalt binder are evaluated by implementing gas chromatography-mass spectrometry (GC–MS) test. Rheological and mechanical tests have provided deep insight into the effects of such combinations of WMA and CR in asphalt binders and results indicated that a crumb rubber modified (CRM) asphalt binder with 15–20% CR yielded optimum performance concerning rutting, fatigue, and cracking performance. Furthermore, while both WMA additives can significantly improve the workability and enhance the rutting performance of CRM asphalt binders, they have a slightly negative effect concerning fatigue and cracking performance of CRM asphalt binders. From the environmental aspect, application of WMA additives also could potentially result in a 63–75% reduction in total emission of CRM asphalt mixtures containing 10–25% CR. Relationship between temperature and the total emission of CRM binders is not linear and it is more than likely a second-order polynomial relationship. Moreover, the results of emission analysis showed that CRM binders deliberate some hazardous fumes due to high temperature, which can be alleviated by incorporating WMA additives into the modified blend.