OVERVIEW
The global drive towards reusing and recycling continues to inspire efforts towards making the most of existing resources. One effective option currently reclaims asphalt from construction and demolition projects for use in new construction. Main Roads would like to increase the permissible amount of reclaimed asphalt pavement (RAP) in the current specifications. WARRIP has been tasked with assisting Main Roads WA to remove barriers to the greater utilisation of this resource. With better understanding of WA materials on hand, improved specifications and technical documents there are potential cost savings and environmental benefits to be realised.
SUMMARY
BACKGROUND
Main Roads Western Australia (Main Roads) currently permits the use of up to 10% RAP in intermediate
course asphalt. The outcomes from a 3-year Austroads project completed in 2016 included guidelines on
how to design asphalt mixes with higher (>15%) levels of RAP. WARRIP investigated current materials and
practice, in addition to plant capability in the Perth metropolitan area, resulting in the development of draft
Engineering Road Note 13B: Asphalt Mix Design with RAP (ERN 13B).
WHAT HAVE WE LEARNED?
Test results from Perth asphalt suppliers during a period of 12 months showed variation in the properties of RAP stockpiles.
The adoption of a RAP management plan and improved RAP management practices reduce variability.
There is a range of types of batch and drum asphalt plants in Perth. Each plant varies as to how RAP is added into the plant and how much can be added without compromising mixing efficiency.
The Queensland Department of Transport and Main Roads (TMR) is also moving to implement higher amounts of RAP based on the Austroads project. Main Roads and TMR collaborated in the development of ERN 13B
WHAT HAS HAPPENED?
- Developed Draft Engineering Road Note 13B: Asphalt Mix Design with RAP, which outlines 3 levels of RAP content that can be incorporated into the design of intermediate course asphalt.
- Proposed amendments to Main Roads Specifications 201, 510 and 511 to accommodate higher amounts of RAP.
- Workshopped and circulated ERN 13B and amendments to specifications to industry for comment.
PROCESS TO ENABLE THE USE OF RAP OUTLINED IN ERN 13B
| Hierarchy of RAP use levels | Level 1 ≤ 10% RAP | Level 2 11 to 25% RAP | Level 3 26 to 40% RAP |
| Requirements | Refer to Specification 510 | Material Asphalt mix design process and testing Plant validation | Material Asphalt mix design process and testing Plant validation |
| Asphalt mix approval | No additional approval required | Asphalt mix approval | Asphalt mix approval |
ERN 13B
ERN 13B is aimed at intermediate course asphalt that is produced with unmodified binder. Noteworthy
requirements are:
| Level 2 | Level 3 | |
| Class binder or blended in line to target viscosity | ✓ | ✓ |
| Nominate target grading | ✓ | ✓ |
| Fractionate into coarse and fine grading | ✘ | ✓ |
| No natural sand | ✓ | ✓ |
| No rejuvenating products | ✓ | ✓ |
| Viscosity based design of blend | ✓ | ✓ |
| Viscosity range limits same as Queensland’s’ | ✓ | ✓ |
| Helpful charts to assess applicable virgin binder to use | ✓ | ✓ |
| Heating of fractions before addition of binder to simulate production process | ✘ | ✓ |
Validate the ERN 13B process with industry partners before finalisation and publication of guidelines.
Investigate the effects of high RAP content in mixes incorporating polymer-modified binders.
Future Considerations
What applications are best suited for high RAP content asphalt to ensure consistent consumption in WA?
What environmental, social and economic benefits can be derived from the specification of high RAP asphalt?