The effects of climate change and the need to limit damage to the environment means that every industry needs to take on the responsibility of reducing its impact on the environment. Among other measures, the development and construction industry is continuing to seek new ways to recycle and reuse waste materials. In the road construction sector the adoption of recycled (or reclaimed) asphalt paving for new road surfaces is growing as a way to limit the amount of waste material going to landfill and reduce emissions via the asphalt production process.
What is reclaimed asphalt pavement?
Reclaimed asphalt pavement (RAP) is a blend of crushed rock, sand, filler and bitumen. It is usually recovered from existing pavements during road profiling operations, or sourced from waste from asphalt production.
There are several benefits to using recycled asphalt for road construction:
- Reduction in greenhouse emissions. The production of new asphalt contributes to environmental pollution, so recycling existing asphalt will help to reduce this.
- Reduced landfill. Asphalt recycling reduces the amount of waste material sent to disposal sites to be used for landfill. The Western Australian government has increased the landfill levy from $8 to $40 per tonne, to encourage companies to send waste material to a recycling centre rather than a waste disposal site.
- Less demand on fresh quarried aggregate. Recycling reduces the requirement to quarry fresh aggregate, reducing the demand on the environment.
- Time savings. When recycling of road materials is done in situ it saves time by reducing the time it takes to transport new material to site and the time it takes for resurfacing.
- Reduced traffic. In situ recycling also reduces the number of heavy vehicles required to deliver materials to site, as well as the removal of waste materials from site. Fewer trucks means less emissions into the environment, and less nuisance to the community during the construction phase.
The Asphalt Recycling Process
Asphalt pavements are a mix of bitumen (approx. 5%) and aggregate (approx. 95%) and have the potential to be totally recyclable. Asphalt on existing roadways is typically processed by the following method:
- The material is removed by a road profiling machine and trucked to a processing area.
- A roadway consists of several layers of different materials and each layer is profiled off separately.
- The recycled asphalt paving (RAP) runs through a series of crushers, after which it is sized and stockpiled for reuse.
- RAP can be reused as a mix for new asphalt or used for hardstand for parking vehicles for example.
Both cold and hot processes can be used in recycling asphalt. In the hot mix asphalt process, the mixture is tumbled while being heated for a set amount of time before it is ready for use. The cold recycling process saves energy and reduces harmful carbon emissions.
RAP is used as a mix for new asphalt to varying degrees in different countries around the world. In Australia, permissible levels of RAP vary in the different states and territories. In Western Australia, mixes generally include 10 to 15 percent RAP. In the United States, nearly 80 percent of the states allow over 25 percent RAP in mixes. In some countries in europe including the Netherlands 50% RAP may be used in base, binder and dense wearing courses.
A commitment to recycling, reusing and repurposing material should be part of any road profiling company’s approach in Western Australia in order to divert waste from landfill and reduce use of non-renewable resources.
An environmentally responsible road profiling company should have an overarching Environmental Policy and Management System in place which minimises the direct and indirect impacts of their activities on the environment. Those companies that are industry leaders will be constantly exploring innovative ways to improve their operations by reducing waste, and offering better recycling options to their clients.