Abstract:
Significant research has demonstrated the potential benefits associated
with crumb rubber modification of bituminous binders for asphalt road surface
production. Most of this previous research has focused on higher (20–30%) dosages
of crumbed rubber and there is now an increased interest in lower (5–15%) dosages
for improved binder and asphalt ageing to extend the time between periodic local
road surfacing. For Marshall designed asphalt mixtures, the volumetric composition
of the mixture is important and isolating the effect of the crumb rubber modification
from the effect of an increased modified binder content is critical to understanding the
economic viability of low dosage crumb rubber as an anti-ageing additive. Testing
of a typical 10 mm dense graded asphalt mixture showed that the rubber is partially
dissolved into the bitumen and both complete dissolution (100%) or no dissolution
(0%) based calculations have a significant effect on Marshall volumetric properties
such as binder film thickness, air voids and voids in the aggregate. Further work is
required to determine a reliable method for determining the degree of crumb rubber
dissolution on a case-by-case basis.
