Implementing Crumb Rubber Gap-Graded and Open Graded Asphalt Technologies—The Australian Experience

Approximately 48 million tyres reach the end of their lives in Australia each year and a substantial proportion of these end up in land fill sites. Although crumbed rubber modified bitumen is used extensively worldwide, the application has been very limited in asphalt mixes in Australia. The paper summarises the performance assessment of the crumb rubber gap-graded asphalt—GGA14(CR)—and open graded asphalt—OGA10(CR) which were trialed in 2018/19. Both asphalt mixes were designed and manufactured with warm mix technology, allowing lower mixing and compaction temperatures, resulting in significant energy saving and emission reduction. The paper discusses the crumb rubber binder blend properties and its storage stability over time. The benchmarking of the rheological properties were carried out by means of the dynamic shear rheometer. Details on the volumetric mix design and performance based mix design such as moisture sensitivity, Hamburg wheel tracking and particle loss tests are provided in the paper for the relevant mix type. The paper also provides details of the manufacturing and construction and field procedures.