Retention behavior of crumb rubber as an aggregate in innovative chip seal surfacing

Abstract

Abstract Statistics show that the world's transportation infrastructures are a primary contributor to global greenhouse gas emissions. This paper introduces an innovative chip seal pavement surfacing that uses crumb rubber made from recycled tires as aggregates. A broad investigation on aggregate retention was performed. Eighty chip seal specimens with varied aggregate and binder parameters were examined for aggregate retention under five tests namely, the standard sweep test, a modified sweep test, the Vialit test, a modified Vialit test, and the Pennsylvania test. Four asphalt-based binders were examined including different types of emulsions and asphalt cement. Two mineral aggregates were examined in the tested specimens in addition to the crumb rubber. Results showed that the crumb rubber performed well in terms of aggregate retention. The Vialit and Pennsylvania tests indicated that the crumb rubber chip seal exceeded the performance of the mineral aggregate chip seals in terms of aggregate retention. The enhanced performance was primarily due to the low unit weight of the crumb rubber and its rough surface, that strengthened the adhesion of the crumb rubber to the binder. The sweep test results show that the mineral aggregate in chip seal surfacing can be replaced up to 100% with crumb rubber but it is recommended to increase the curing time before opening the roads for traffic due to the negligible water absorption capacity of crumb rubber.