A US industry expert has challenged Canadian operators to boost the use of reclaimed asphalt.
Jim Musselman, asphalt performance manager with Oldcastle Materials and former State Bituminous Materials Engineer for the Florida Department of Transport laid out the case for increasing the amount of reclaimed asphalt in new pavement at the Ontario Hot Mix Producers Association fall meeting.
But Musselman stressed that increasing reclaimed content has to be done in a quality-focused manner or there will be failures that will lead to restrictions on its use.
In the US, a fifth (70m tonnes) of the approximately 350m tonnes of asphalt mix produced and used to pave roads, is old recycled asphalt. “That saves a lot of space in landfills,” said Musselman, emphasizing the environmental and financial benefits of those recycling efforts.
These measures include an estimated $2.3bn in savings annually compared to the cost of purchasing raw materials, the conservation of 22 billion tonnes of asphalt binder and 68 million tonnes of aggregate, plus the reduced associated costs of producing, processing and trucking of those materials. Using RAP can also speed up construction, he said.
The Federal Highway Administration (FHWA) has been encouraging the use of recycled materials for a number of years and the use of RAP has increased from 15% in 2009 to 21% currently. For various reasons, the percentage varies from state to state, he said.
“We have a competitive market here,” said Musselman, referring to his home state of Florida where the average RAP content of all the asphalt mixes produced and placed statewide is roughly 30%, according to a National Asphalt Pavement Association survey.
Another economic driver is the fact that aggregate and asphalt binder are fairly expensive in the state. In central and north Florida, aggregate has to be obtained from other states and Canada, he said.
Although Musselman encouraged increased RAP contents, he highlighted measures and precautions required in producing high quality asphalt mixes with those higher contents — both at asphalt plants and on the construction road site.
Some basic steps include proper aggregate stockpiling and handling, establishing the goals and expectations for the mixture, understanding the specifications, properly evaluating the materials through frequent sampling, developing a high quality mix design and “properly constructing the pavement,” he said.
Achieving those standards requires good and constant communications with the entire project team, including producers, contractors and transportation agencies. Clearly understanding the specifications is particularly important, “because they can change quite frequently and are not written in a vacuum. Understand the specifications as well as the person who wrote them,” Musselman said.
Higher quality mixes with RAP will create greater confidence in allowing and using increased contents and that in turn will eliminate, “some of the barriers” associated with RAP and make its use more commonplace and acceptable. That acceptance will help lower construction costs, he said.
Musselman predicts that, “in the next 50 years RAP contents will average well over 50 per cent.”
There is a wealth of information available on producing high quality asphalt with high RAP, said Musselman, citing studies by the National Cooperative Highway Research Program and the National Asphalt Paving Association.