Early OH&S indications positive for use of Crumb Rubber Modified Binder in Open Graded Asphalt
Crumbed rubber has been in used in binders and sealant in road building internationally, since the 1960s and in Australia since the mid-70s. The increased use of crumbed rubber, at various stages of the road building process, offers not only significant improvements to road surface durability but also a valuable use for end-of-life tyre-derived product.
As part of its Research and Development funding program, TSA has been working with a range of interested parties, on addressing barriers to increased use of crumbed rubber in seals and asphalt. One such barrier has been a perception that the use of crumbed rubber modified (CRM) binder may add to harmful emissions during the asphalt laying process.
To help assess that concern research supported by TSA, the Department of Environment and Heritage Protection (EHP, QLD) and Queensland Transport and Main Roads (TMR) included emissions monitoring of an open graded asphalt (OGA) demonstration project. This monitoring and analysis was completed by the Australian Road Research Board as part of the TMR/ARRB research program. Emissions were monitored at various stages of the asphalt manufacturing and laying process and at varying temperatures.
Three sections were laid to compare emissions from CRM binder OGA to ‘conventional’ SBS polymer modified binder (PMB) asphalt, i.e. hot mix CRM OGA, warm mix CRM binder OGA and hot mix SBS PMB OGA. Measurements were taken from the manufactured (loose) mix (at the manufacturing facility) and from personal monitoring devices worn by paving-team members. The tests sought to simulate the worst-case scenarios, in terms of operational and environmental conditions.
The early indications are that, on average where warm mix CRM binder OGA was used, there are no additional harmful emissions when compared to ‘conventional’ hot mix SBS PMB OGA. The initial results indicate that the temperature of the mix has a significant bearing on emissions. These results reflect those from other international studies in the USA & Europe.
Research and assessment of results continues with the results to be confirmed in the future; however, the initial results suggest that the increased use of crumbed rubber in asphalt can be achieved with no additional harmful emissions during the road building process when compared to ‘conventional’ PMB asphalt.
It is expected more details will be presented in a paper in August at the Australian Asphalt and Paving Association (AAPA) national conference in Melbourne with a full report to be published on the TMR/ARRB research program (NACoE) website. This will be significant for the application of rubber in roads.