The practice of recycling end-of-life tyres for use in road construction has been in place for over 30 years in Western Australia (WA). Crumb rubber modified (CRM) binder technology when applied to asphalts and sprayed bituminous seals provides improved road performance, reduced landfill volumes and preservation of natural resources.
Over 3 stages, the development, implementation and characterisation of a CRM Open Graded Asphalt (OGA) and two CRM Gap Graded Asphalt (GGA) mixes for use in WA was realised through the WARRIP. Together with industry partner Fulton Hogan, these CRM asphalt mixes underwent manufacture and construction trials to evaluate the practicability of the mixes. Laboratory performance testing indicated that both mixes will perform well in the field, providing equal or greater durability when compared to the typical polymer modified binder mixes.
The results informed the development of draft specifications for CRM binder in both OGA and GGA mixes, facilitating use as a standard product in WA. On 16 November 2020, Main Roads WA published the CRM OGA specification. The draft specification for the CRM GGA mix is being finalised with publication anticipated in the third quarter of 2022.
Every year in Australia, millions of tyres reach their functional end-of-life and are commonly disposed in landfill. Crumb rubber derived from waste tyres can be used in bitumen for road construction, providing increased durability and cracking resistance. The use of crumb rubber modified (CRM) binder in open-graded asphalt (OGA) is commonplace internationally, but remains atypical in Australia.
Incorporating crumb rubber into bitumen not only improves performance, but is also a high-value, sustainable alternative utilisation for a waste material. The use of CRM in high-performance sprayed seals has been routine practice in Western Australia (WA) for over 30 years. However, its use in asphalt has not been previously explored. The WARRIP sought to validate CRM technology in OGA for wider use by industry.
ACHIEVED TO DATE
- Successful development of CRM binder conforming to AAPA and draft Main Roads specification.
- Successful substitution of CRM binder for synthetic polymer modified binder in Main Roads standard OGA mix.
- Draft Specification 516 Crumb Rubber Open Graded Asphalt developed and validated through mix design and production trial.
- Full-scale trial sections constructed on Kwinana Freeway.
- Use of a workability additive facilitated placement of the OGA at 150°C or possibly lower temperature.
ACHIEVED TO DATE CONT.
- Personal exposure monitoring on the truck controller, paver operator and leading hand screed indicated emissions well below acceptable limits.
Substitution of CRM for synthetic polymer modified bitumen to be extended to a wider program of resurfacing work beginning in 2019/2020.
- Exploring the placement of OGA with higher in-situ air voids to achieve improved outcomes for road users and the community
Can CRM be used in other
types of asphalt?
What is the maximum amount
of rubber to yield the best
performance of the asphalt?
Project Update: Field Trial of Crumb Rubber in Open-grade Asphalt
WARRIP and industry partner Fulton Hogan are constructing a trial section of OGA with CRM binder on Kwinana Freeway during 17-20 March 2019. The demonstration will confirm whether the technology (design, manufacture & construction) can be successfully applied in WA prior to broader use within industry.
Every year millions of tyres in Australia reach their functional end-of-life. Crumb rubber modifier (CRM) in bitumen is used for road construction and can provide increased durability and cracking resistance. In addition to improved performance, recycling ground tyre rubber reduces landfill volumes and preserves natural resources. The use of CRM in high-performance sprayed seals has been routine practice in Western Australia (WA) for over 30 years. Internationally, the use of CRM binder in open-graded asphalt (OGA) is accepted practice and the project seeks to transfer the technology to WA.
- Comparison of specifications and practices
- Evaluate production and placement properties of OGA with CRM in the laboratory
- Develop a Main Roads specification for OGA with CRM
- Conduct and monitor trial constructing OGA with CRM
- Document findings, recommending areas of possible improvement
- Successful development of CRM binder with 18% crumb rubber by mass of total binder
- Successful substitution of CRM binder with 18% crumb rubber into Main Roads standard OGA.
- Successful yard trial paving 20 tonnes of OGA with 18% CRM binder.
- Construction of trial pavement on Kwinana Freeway Northbound in progress.